Acute And Chronic Forms Of Inflammation Biology Essay

Acute And Chronic Forms Of Inflammation Biology Essay Katharine Buzzbee is a pleasant young girl of 9 years old. She was brought to the health center with complaints of sore throat with difficulty swallowing. Her mother states that Katharine has had similar symptoms three separate times this year. The illnesses begin with irritation in the throat that progress to pain. The pain radiates to her ears and she generally develops a fever during the course of each attack. The patient also has a history of developing frequent colds where she experiences headaches, a stuffy nose and frequent sneezing. Her older brother and sister have both recently had the common cold. The patient is otherwise healthy with no major illnesses or injuries. Clinical manifestations: On examination, Katharines palatine tonsils are swollen, red and surrounded by exudate. She has a temperature of 101.1Â °F and complains of a running nose and headache. She appears tired and isnt as energetic as in our previous encounters. Diagnosis: acute tonsillitis. Throat culture confirmed strep. bacterial infection. Etiology: Acute tonsillitis is generally caused by a viral infection1, most commonly caused by common cold viruses such as: adenovirus, rhinovirus, influenza, coronavirus, respiratory syncytial virus. The Epstein-Barr virus, herpes simplex virus, cytomegalovirus and HIV occasionally manifest as tonsillitis. The second cause of acute tonsillitis is bacterial1 (about 30% of patients). The common bacterium is group A Beta hemolytic streptoccal. Other strains of bacteria are less common. The patient listed above has this type of infection. Pathogenesis: virus or bacteria attacks tonsil tissue exiting the response of innate immunity and adaptive immunity of T and B cells contained in the tonsils. The lymphocytes fight the infection, which leads to inflammation. As long as the lymphocytes and other cells can weaken the virus/bacteria the damage to the cells within the tonsils will remain reversible. Treatment: 10-day course of oral penicillin2, rest and hydration. Prognosis: symptoms should resolve during course of treatment. If frequent onset of tonsillitis continues tonsillectomy may be recommended. Inflammatory response The bacteria is ingested or inhaled and attaches to the palatine tonsils (injury). At the gross level the tonsils become swollen with erythema causing pain and difficulty completing normal tasks such as swallowing. In the study by Liljaa, Raisanenb and Stenfors3, the researchers studied bacterial and epithelial cells from palatine tonsils of nine patients with positive streptococcus pyogenes infection. The reported findings showed, S. pyogenes could be identified both in the mucous layer covering the tonsils and attached to the surface epithelial cells. Long chains of coccus-shaped bacteria could be seen encroaching on the epithelial cell borders. S. pyogenes can apparently penetrate the mucous barrier, attach to the epithelial cells, spread from cell to cell and possibly penetrate into the outermost layer of the epithelial cells. These events in turn provoke cytokine production and/or complement activation, which induce inflammatory reaction in the tonsillar tissue (activation). Dead bacteria and bacterial debris will remain at the site of the infection and must be removed (phagocytosis) from this area by neutrophils and macrophages5. Once the bacterium has been removed through phagocytes the tonsillar tissue will resume its normal form through resolution (healing process). Swelling and pain will cease. Chronic inflammation: Ulcerative Collitis Case study Jedediah Jones is a 24-year-old student pursing a degree in chiropractic medicine. He presents today with abdominal pain and frequent diarrhea containing mucus and blood. The onset of these symptoms began 2 months ago, but Jedediah decided to seek treatment when his frequent bowel movements began to disrupt his studies. Patient states that on average he has approximately 8 bowel movements per day, most frequently occurring after a meal. His abdominal pain is most severe before a bowel movement, but remains constant at the pain level of 4 out of 10. Patient says pain is 6 out of 10 at its worse. Patient attributes the symptoms to his newly adopted diet mostly consisting of fast food. Until recently he lived at home where all his meals were homemade. Patient has experienced an increased level of stress since beginning his studies (6 months ago) and subsequently quit smoking cigarettes. Patient exercises regularly, but has experienced a decrease in energy levels since the onset of symptoms. Patient denies other illness or injuries and is currently not taking any medication. Patients twin brother was recently diagnosed with Crohns disease and his maternal grandfather died of colon cancer at 48 years old. Clinical manifestations: LLQ tender upon palpation and entire abdomen appears distended. Patient claims 8 bowel movements per day with a watery consistency containing mucus and blood. Conjuctiva and finger nail beds appear pale. Diagnosis: ulcerative colitis, confirmed by positive biopsy removed during sigmoidoscopy. Inflammation of bowel appeared to extend no further than the descending colon with most severe inflammation and ulceration in the sigmoid section. Stool cultures ruled out parasitic infection. Etiology: the cause of ulcerative colitis is unknown, but factors such as genetics7, psychological stress, smoking cessation and poor diet have been attributed to onset of disease. Pathogenesis: as stated in the pathology textbook7, Most investigators believe that [ulcerative colitis and Crohn disease] result from a combination of defects in host interactions with intestinal microbiota, intestinal epithelial dysfunction, and aberrant mucosal immune responses. Treatment: Sulfasalazine 2 pills by mouth, 3 times per day. Rowasa (mesalamine) rectal suspension enema, at bedtime until bleeding stops. Prognosis: continue medication until symptoms have resolved completely. Maintenance therapy will be recommended indefinitely to avoid relapse. Inflammatory response Podolsky8 explains in his article that inflammatory bowel disease (IBD) is believed to be the result of an ongoing activation of the mucosal immune system. This abnormal response is likely due to the defects in both the intestinal epithelium and the mucosal immune system (injury). Podolsky8 clearly defines the inflammatory response of IBD, Chronic, recurrent intestinal inflammation appears to result from stimulation of the mucosal immune system by-products of commensal bacteria in the lumen. Stimulation may occur as a result of the penetration of bacterial products through the mucosal barrier, leading to their direct interaction with immune cells, especially dendritic cells and lymphocyte populations (chemotaxis). Alternatively, bacterial products may stimulate the surface epithelium, possibly through receptors that are components of the innate immune-response system; the epithelium can, in turn, produce cytokines and chemokines that recruit and activate mucosal immune cells (transmigration). Cellular changes occur in ulcerative colitis as the chronic inflammation may lead to mucosal atrophy7, damage to the muscularis propria and disrupt neuromuscular function leading to colonic dilation and risk of perforation (cellular changes). As stated in the textbook7, The inflammatory process is diffuse and generally limited to the mucosa and superficial submucosa. Submucosal fibrosis, mucosal atrophy and distorted mucosal architecture remain a residual of healed disease but histology may also revert to near normal after prolonged remission (healing process).

Analysis around Freuds view of the human mind Essay

This essay aims to discuss the key ideas behind Freud’s theories, including his model of the mind, psychosexual development, repression and cure through therapeutic techniques. Sigman Freud (1856 to 1939) was an Austrian physician, with an interest in the workings of the subconscious mind. â€Å"Freud spent his life trying to produce coherent a set of theories to explain all human behavioural, but never achieved his goal of one grand theory, (Benson, 1999, P48).  According to Freud, the mind has three levels of consciousness. The conscious equates to 1/7th of the mind, being ‘the awareness we have when awake.’ The pre-conscious, is a boundary containing memories of dreams, and causing slips of the tongue. Finally, the unconscious. Making up 6/7ths of the mind and containing ‘thoughts completely hidden and unavailable to us,’ (Benson, 1999, P47). Freud’s model divides the mind in to three parts: the Id, Ego and Superego. He believed that the first to develop was the Id, operating on the pleasure principle, in the unconscious mind. The Id ‘is the dark, inaccessible part of our personality,’ (Freud, 1933 p27). It drives a baby to seek pleasure, like ‘drink food warmth and comfort and avoid the unpleasureable, like hunger, being wet and cold†¦ The Id is selfish and ‘not concerned with social rules, but only with self gratification,’ (Cardwell et al, 1997 p549). The Id is made of two components. Benson (1999, P51) describes the first, Libido, as ‘the inborn energy we have that motivates us to survive.’ The second component, Freud named Thanatos, and described as the death instinct, expressed through aggression towards self and others. Cardwell et al (1997) explain that the Id’s discharge of energy and excitation without regard for consequence is known as primary proc ess thinking. At around two years old the human mind recognises the need to be realistic and plan for the future, rather than surviving on primary instinct. Thus the ego develops. Operating on the reality principle, it battles the Id for control of behaviour. Unlike the Id, the Ego has a partly conscious, secondary thought process. ‘The ego is still, however, essentially selfish, i.e. protecting the individual from harm,’ (Benson, 1999, p51). At around 3, we start to absorb influence from our parents and the Super Ego begins to develop. The Super Ego expands from our learned morals and the conventions of society. ‘Super means above – looking down and monitoring the â€Å"Id-Ego† Battle,’ (Benson, 1999, P52). Like the Ego, the Super Ego is partly conscious; however it is not selfish and considers others too. As it develops it becomes ‘our social conscience and guides us towards sociably acceptable behaviour.’ (Cardwell et al, 1997, p549).  Freud was responsible for modern society’s understanding of the effects childhood experiences can have on adult personalities. He split the childhood into five stages of psychosexual development. During the first, the Oral stage from 0 to 2 years, the only drive present is the Id. Focused on survival, the Id drives the baby to feed by suckling. Thus the mouth becomes the main source of pleasure. Benson (1999, p52) states that ‘through oral satisfaction the baby develops trust and an optimistic personality.’  From 2 to 3 years, the child becomes aware of its bowels and how to control them. Here begins the Anal Stage, as ‘the focus of gratification shifts to the anus†¦ aiding with potty training,’ a vital step to independence and survival, (Benson, 1999, P54). However, withholding elimination goes against the Id’s nature of random discharge without regard for consequence. This results in the requirement for an ego to develop, ‘and as such has important implications in the personality later in life,’ (Cardwell et al, p550, 1997). The phallic stage, from 3 to 5 years, starts when children become aware of sexual differences and become curious about their own genitals. Benson (1999) explains that boys will develop differently to girls from here on. Boys will develop Oedipus Complex and unconsciously experienced a sequence of sub stages. Firstly he will develop a strong desire for his mother. Then, after noticing the strong (sexual) bond between her and his father, he will become deeply jealous of his father and hate him. The boy’s fear of his father uncovering these thoughts instils a fear of the ultimate punishment, castration. The boy resolves that to avoid castration by pleasing his farther, and at the same time impress his mother, he must become like his father. This is called identification. Girls, having unconsciously concluded that they have already been castrated, do not develop the same fears. Though, ‘since their mother is the same, girls also end up identifying, i.e. adopting their mother’s morality and gender roles. This was always rather vague’ and known as the Electra Complex (Benson, 1999, p56).

Business Law - S 18 of the Australian Consumer Law within the Competition and Consumer Act 2010 (ACL) Free Essay Example, 2000 words

Enforcement of the provision Section 18 of ACL is arguably wide in its application, considering that it takes care of any individuals who participate in deceptive behaviour and or those intending to do so. Owing to the fact that the Competition and Consumer Act 2010 (CCA) is a statutory provision, section 51 of the Australian Constitution limit its enforcement. Nonetheless, section 18 of the ACL is premised upon the power of the business organizations as enshrined in the Constitution to operate freely in legal business and act in good faith. Mardirossian, Robbins and Leibler (2010) noted that the condition imposed by â€Å"trade or commerce† is important to its enforcement. As Heinrich and Bracken (2009) have argued, parties may be indirectly liable for violations of s18 if the court establishes their knowledge of the breach before its commission or omission. Each of the federations and regions of Australia are covered under fair trading laws, which draws several similarities to the ACL, but whose mandat es are limited. Misleading and Deceptive practices The outlaw of misleading practices as set out in section 18(1) of the ACL should be interpreted together with section 4(2)(a) of the CCA in order to give it a complete, productive meaning. We will write a custom essay sample on Business Law - S 18 of the Australian Consumer Law within the Competition and Consumer Act 2010 (ACL) or any topic specifically for you Only $17.96 $11.86/page As Morrison, Abraham and Sheargold (2010) have indicated, to be deceptive or misleading, the practice must comprise a distortion of fact capable of enticing the relevant victim into arriving at an erroneous judgment. In most cases, misrepresentations are inaccurate statements of information. Nonetheless, statements that are credible may also have the intent to misrepresentations if their use is capable of swaying consumers into making mistakes. The appropriate test applied in common law with regard to misleading and deception practices is whether the practice is in itself erroneous; or has the potential to create an erroneous judgment in the consumer (Schaper, 2009/2010).

Strategic Management Accounting - 2595 Words

Tables of content Page No Introduction 03 Models and concepts affecting the pricing decision 03 Approaches to pricing 04 i. Cost–volume–profit analysis 05 ii. Cost plus mark-up pricing 07 iii. Target rate of return pricing 07 Standard costing and Variance analysis 08 The role of standard costing and variance analysis 12 Limitations of Standard Costing and variance analysis 12 Evaluation of Activity Based Costing system 13 Advantages of ABC system 17 Limitations of ABC system 17 References 18 Introduction This report is mainly focusing to understand and analyse the issues involved in Manac plc where by the company is not meeting target budgeted profit. This is a†¦show more content†¦Now let us look at some of the decision making models which affect the pricing decisions regarding our electrical goods made by us. At last, we should understand the mechanics of making pricing calculations of our standard electrical goods based on an appropriate model. Approaches to pricing There are many approaches to pricing and accounting information can be used for these approaches. They are; i. Cost–volume–profit analysis, ii. Cost-plus pricing, iii. Target rate of return pricing. i. Cost–volume–profit analysis This method known as CVP analysis is used to develop and understand the relationship between revenue, cost and sales volume. Thus, CVP is concerned with understanding of the relationship between changes in the number of units sold and changes in selling prices and costs. Typical issues that CVP answers are: * Effect on profits of changes in selling price or the volume of sales, * If we incur additional costs, changes that we should make to our selling price or to the volume that we need to sell (P.M. Collier 2003). CVP can be used as a sensitivity analysis which is an approach to understand as to how changes in one variable (e.g. selling price) affect to other variables (e.g. Sales Volume). Using this analysis which is illustrated bellow, we can have a better understanding of product’s selling price of Manac plc. Illustration 1 Target Budgeted profit of Manac plc is  £100,000 on sales of 20,000 units ofShow MoreRelatedStrategic Management Accounting13457 Words   |  54 Pagesof this journal is available at www.emeraldinsight.com/0951-3574.htm AAAJ 21,2 Strategic management accounting: how far have we come in 25 years? Kim Langï ¬ eld-Smith Monash University, Melbourne, Australia Abstract Purpose – The purpose of this paper is to provide a review of the origins of strategic management accounting and to assess the extent of adoption and â€Å"success† of strategic management accounting (SMA). Design/methodology/approach – Empirical papers which have directly researchedRead MoreStrategic Management Accounting1773 Words   |  8 PagesSTRATEGIC MANAGEMENT ACCOUNTING This report will attempt to explain what Strategic Management Accounting (SMA) is, how it developed, why Traditional Management Accounting (TMA) is not sufficient to provide information for strategic decisions and the difference between SMA and TMA. It will further outline some of the essential analytical tools or techniques in SMA such as Activity Based Costing (ABC) and the Balanced Scorecard (BSC). SMA is an extremely broad concept, so in order to give a bird’sRead MoreStrategic Management Accounting2093 Words   |  9 PagesWhat is Strategic Management Accounting? And why, Strategic Management Accounting? Simple definition: Management Accounting in the context of business strategies being planned and implemented by an organisation. Strategy is the way that a firm positions and distinguishes itself from its competitors. These business strategies must be developed in the context of the internal and external environments so that they are practical, or else they will remain a theoretical wish-list. It is alsoRead MoreStrategic Management Accounting3162 Words   |  13 Pagesproducts; and the emergence of e-business and so on. As a result of the defects of traditional accounting have been unable to meet these changes new management themes have evolved which in turn has resulted in the development of strategic management accounting. Strategic management accounting aims to provide relevant information to an organization’s management to enable them to make strategic plans and strategic decisions. The emphasis is on external information on competitors, customers, markets, andRead MoreRole Of A Strategic Management Accounting Essay1317 Words   |  6 Pagesand Goddard 2008) investigating the role of strategic management accounting in an organizational setting? The role of strategic management accounting (SMA) is a relatively new concept especially within organizational settings (Juras, 2014). In addition to being new, it posits as an interesting field of study since existing literature evidences that conducting management accounting in relationship with strategy is problematic (Endraria, 2015). Accounting managers endure challenge of aligning functionalRead MoreStrategic Management Accounting : The Beginning Essay1797 Words   |  8 PagesIntroduction Discussion 1. Strategic Management Accounting: The Beginning To survive and succeed in the ever-evolving global business climate requires an understanding on how to formulate business strategies that are future proof (Daud, 2012). In reaction to this growing pressure firms are looking for innovative ways to remain competitive and apply a strategic perspective in every aspect of their business. This led to a close up on conventional management and cost accounting practices and sparked criticismRead MoreQuestions On Strategic Management Accounting2396 Words   |  10 PagesOver the past recent years a new term namely â€Å"Strategic Management Accounting† has been introduced in management accounting discussion. In the following years and still today, a debate about what SMA comprises has been oriented. It is considered widely by organizations while drafting and implementing strategic planning and control system in an organization. This essay will elaborate the understanding and analyzing of work done by CIMA and some other surveyors in r elation to this field. SecondaryRead MoreManagment Accounting, Financial Control, Management Control, Strategic Management Accounting (Sma)3965 Words   |  16 PagesIntroduction: To better understand differences between many similar types of terms in accounting such as management accounting and financial accounting, management control and financial control and strategic management accounting we will explore the case study of TNT and how the company has been able to implement these important concepts practically in this case. Firstly, we will see how the management and financial controls were used in order to achieve what Taylor say’s is Critical Mass. We willRead MoreStrategic Management Accounting and Balanced Score Card11170 Words   |  45 PagesCHAPTER 17: ACCOUNTING FOR STRATEGIC MANAGEMENT CHAPTER OUTLINE ï  ± ï  ± ï  ± Learning outcomes Introduction Organisational strategy o Definition o Cumulative strategy (strategising) ï  ± Strategic management accounting (SMA) o Definition o Components of SMA o Does SMA still exist; or, what is it becoming? ï  ± The balanced scorecard o Its origins and its purpose o Elements and characteristics of a balanced scorecard o Designing a balanced scorecard o Features of a balanced scorecard o Why hasRead MoreStrategic Management Accounting : Cost Advantage And Differentiation Advantage996 Words   |  4 PagesTraditional management accounting is cost driven with short-term pricing and profit motive. It is fragmented and has internal and financial focus. Strategic management accounting is market driven with long-term pricing and profit motive. It is integrated and has value and external focus. Strategic management accounting raises the issues and addresses the weaknesses of traditional management accounting in the modern market place. Strategic management accounting requires the application of strategic management

Essay Cars in F. Scott Fitzgeralds The Great Gatsby

In Fitzgerald’s The Great Gatsby, symbols are an important and integral part of what makes it a great novel. Though there are numerous and different aspects that could be explored, a repeated and often mentioned aspect are the revolutionary vehicles. Cars in the 1920s were a symbol of status and privilege as they were becoming increasingly affordable. Though most people could own a car due to Ford releasing the Model T, the colored vehicles usually a sign of wealth and status. Fitzgerald often uses the car as a symbol of death, or a journey to a destructive event, rarely is the car portrayed in a positive manner. I think that in The Great Gatsby, Fitzgerald is trying to connect automobiles and vehicles to the idea of consumerism. And by†¦show more content†¦Another interesting detail is Gatsby’s car is yellow instead of the standardized black of the era stresses the thought that he is engrossed with the obsession of displaying his material wealth to get the lov e of Daisy. The Death car is yellow, and in the novel yellow symbolizes money and corruption in the novel. The creamy color of Gatsby’s car also symbolizes decay of corruption; therefore Gatsby’s car is like a bulging piece of fruit that is overripe and has started to rot. To each character cars had a different meaning. For Tom, who has numerous cars uses them as a reminder of the past, the cars a symbol of how consumerist and materialistic he is. He believes that maybe if he had enough things, enough cars, he will be happy. Gatsby has an excessive car, a symbol of trying to attain what Tom has, however never being able to really reach that status. Nick has no car, Nick really represents Fitzgerald’s own opinion on the era. Fitzgerald presents us with two possibilities of the future. The people with cars end up being miserable and lost and Nick. Myrtle is killed by a car, another symbol of how materialism can consume someone. Myrtle wanted what she couldn’t have, a lavish life without work. In conclusion, Fitzgerald’s attitude towards consumerism and materialism is brought to light by his portrayal of vehicles in The Great Gatsby. As if Fitzgerald could tell the future, our society as it is today is mostly drivenShow MoreRelatedViews of Entitlement in the Great Gatsby1596 Words   |  7 PagesThe Great Gatsby as Fitzgerald’s explanation of an American Reality which contradicts the American Dream That was always my experience—a poor boy in a rich town; a poor boy in a rich boys school; a poor boy in a rich mans club at Princeton.... However, I have never been able to forgive the rich for being rich, and it has colored my entire life and works.   —F. Scott Fitzgerald: A Life in Letters, ed. Matthew J. Bruccoli. New York: Scribners, 1994. pg. 352. The Great Gatsby, by F. ScottRead More gattom Importance of the Automobile in The Great Gatsby Essay1522 Words   |  7 Pagesthe Automobile in The Great Gatsby    F. Scott Fitzgeralds The Great Gatsby was written about a time of gaiety for a certain set of people. One of the major thematic aspects of the book is driving and the automobile. At the time the book was written the car had begun its establishment as a national institution. This is apparent in one of the central events in the book. Toms unfaithfulness first comes to light from a car accident in Santa Barbara. He misguides the car and the misdirection ofRead More F. Scott Fitzgerald’s The Great Gatsby Essay1211 Words   |  5 PagesF. Scott Fitzgerald’s Portrayal of the Twenties F. Scott Fitzgerald was accurate in his portrayal of the aristocratic flamboyancy and indifference of the 1920s. In his novel, The Great Gatsby, Fitzgerald explores many aspects of indifference and flamboyancy. A large influence on this society was the pursuit of the American Dream. Gangsters played a heavily influential role in the new money aristocracy of the 1920s. The indifference was mainly due to the advent of Prohibition in 1920. One majorRead MoreThe Great Gatsby By F. Scott Fitzgerald1395 Words   |  6 Pagesthe words of Mr. F. Scott Fitzgerald, â€Å"we are all just humans†¦ drunk on the idea that love, only love, could heal our broken bones.† Fitzgerald was a romantic living in the modernist 1920s, and his classic work The Great Gatsby was certainly a romantic book, and thusly did not succeed in his time; in fact, it did not succeed until after his death in the 1940s. Fitzgerald saw the green light, but it was just as out of reach to him as it was to Mr. Gats by. Though The Great Gatsby was unappreciatedRead MoreF.Scott Fitzgeralds The Great Gatsby Essay967 Words   |  4 Pageswere three things that were important to anyone looking to be anyone in East New York’s high society in the Roaring 20s. F. Scott Fitzgerald captured all three with his literary voice. He made impressions everywhere with the supreme achievement of his third novel, The Great Gatsby. This novel is a tale of people’s exciting lives in the 1920’s. Fitzgerald uses the Great Gatsby to illustrate the American identity during the early twentieth century. Fitzgerald uses symbolism and narrative techniquesRead More The Importance of George Wilson in The Great Gatsby Essay738 Words   |  3 PagesThe Importance of George Wilson in The Great Gatsby   Ã‚  Ã‚   F. Scott Fitzgeralds The Great Gatsby is a superbly written and an intrinsically captivating novel that deals with the decline of the American Dream and how vapid the upper class is. To illustrate and capture the essence of these themes, Fitzgerald uses characters Gatsby, who epitomizes the actual American Dream, and Daisy, who is based on the ideal girl. Yet, as these characters grasp the topics Fitzgerald wants to convey, thereRead MoreF. Scott Fitzgerald’s Expression of Temptation, Deceitfulness, and Jealousy in The Great Gatsby1252 Words   |  6 PagesF. Scott Fitzgerald’s book The Great Gatsby was a remarkable book. Fitzgerald Made the characters of the book as real and as personal as possible. Three characteristics stood out in the novel to me. Tom’s Jealousy of Gatsby relationship with his wife, Gatsby’s lies about who he is and his life, and Daisy’s ways to tempt Gatsby to fall in love with her. The novel was inspired by the way he fell in love with his wife Zelda. The novel The Great Gatsby displays deceitfulness in many of its charactersRead MoreThe Colors of Gatsby, F. Scott Fitzgeralds Famous Novel1640 Words   |  7 PagesF. Scott Fitzgerald is famous for the detail with which he crafted the quintessential American novel, The Great Gatsby. With his well-chosen words, Fitzgerald painted a fantastic portrait of life during the Roaring Twenties in the minds of his readers, a picture rich with color and excitement. Four colors: green, gold, white, and gray played key roles in the symbolic demonstration of ideas and feelings which, woven together seamlessly, made The Great Gatsby a world-renowned work of literary geniusRead More Symbols and Symbolism in The Great Gatsby Essay1207 Words   |  5 PagesSymbolism in The Great Gatsby       Fitzgerald’s The Great Gatsby has more relevance in today’s society than it did when it was written. With the recent societal trend that emphasizes lack of morals and material wealth over a meaningful existence, Fitzgerald’s message really hits home. Which is more important - money or love? Social status or being true to oneself? Fitzgerald uses metaphor and symbols to great effect in order to illustrate what can happen when the pursuit of happinessRead MoreThe Great Gatsby And F. Scott Fitzgerald1456 Words   |  6 Pagesmy cocky and immature counterparts. The Great Gatsby and F. Scott Fitzgerald American novelist Francis Scott Key Fitzgerald, best known by his pen name F. Scott Fitzgerald, is regarded as one of the greatest American writers of the 20th century, his stories coinciding with the Jazz Age. Most notable of his many novels is The Great Gatsby. Many see this piece as being quite similar to his own life, that characters such as the novel s protagonist Jay Gatsby and narrator Nick Carraway reflect this

Steam Jet Refrigeration Cycle Free Essays

string(61) " ow rates gives the mass \? ow rate of the compressed vapor\." Chemical Engineering and Processing 41 (2002) 551– 561 www. elsevier. com/locate/cep Evaluation of steam jet ejectors Hisham El-Dessouky *, Hisham Ettouney, Imad Alatiqi, Ghada Al-Nuwaibit Department of Chemical Engineering, College of Engineering and Petroleum, Kuwait Uni6ersity, P. We will write a custom essay sample on Steam Jet Refrigeration Cycle or any similar topic only for you Order Now O. Box 5969, Safat 13060, Kuwait Received 4 April 2001; received in revised form 26 September 2001; accepted 27 September 2001 Abstract Steam jet ejectors are an essential part in refrigeration and air conditioning, desalination, petroleum re? ning, petrochemical and chemical industries. The ejectors form an integral part of distillation columns, condensers and other heat exchange processes. In this study, semi-empirical models are developed for design and rating of steam jet ejectors. The model gives the entrainment ratio as a function of the expansion ratio and the pressures of the entrained vapor, motive steam and compressed vapor. Also, correlations are developed for the motive steam pressure at the nozzle exit as a function of the evaporator and condenser pressures and the area ratios as a function of the entrainment ratio and the stream pressures. This allows for full design of the ejector, where de? ing the ejector load and the pressures of the motive steam, evaporator and condenser gives the entrainment ratio, the motive steam pressure at the nozzle outlet and the cross section areas of the diffuser and the nozzle. The developed correlations are based on large database that includes manufacturer design data and experimental data. The model includes correlatio ns for the choked ? ow with compression ratios above 1. 8. In addition, a correlation is provided for the non-choked ? ow with compression ratios below 1. 8. The values of the coef? cient of determination (R 2) are 0. 85 and 0. 78 for the choked and non-choked ? w correlations, respectively. As for the correlations for the motive steam pressure at the nozzle outlet and the area ratios, all have R 2 values above 0. 99.  © 2002 Elsevier Science B. V. All rights reserved. Keywords: Steam jet ejectors; Choked ? ow; Heat pumps; Thermal vapor compression 1. Introduction Currently, most of the conventional cooling and refrigeration systems are based on mechanical vapor compression (MVC). These cycles are powered by a high quality form of energy, electrical energy. The inef? cient use of the energy required to operate such a process can be generated by the combustion of fossil uels and thus contributes to an increase in greenhouse gases and the generation of air pollutants, such as NOx, S Ox, particulates and ozone. These pollutants have adverse effects on human health and the environment. In addition, MVC refrigeration and cooling cycles use unfriendly chloro-? oro-carbon compounds (CFCs), which, upon release, contributes to the destruction of the protective ozone layer in the upper atmosphere. * Corresponding author. Tel. : + 965-4811188Ãâ€"5613; fax: + 9654839498. E -mail address: eldessouky@kuc01. kuniv. edu. kw (H. El-Dessouky). Environmental considerations and the need for ef? cient se of available energy call for the development of processes based on the use of low grade heat. These processes adopt entrainment and compression of low pressure vapor to higher pressures suitable for different systems. The compression process takes place in absorption, adsorption, chemical or jet ejector vapor compression cycles. Jet ejectors have the simplest con? guration among various vapor compression cycles. In contrast to other processes, ejectors are formed of a single uni t connected to tubing of motive, entrained and mixture streams. Also, ejectors do not include valves, rotors or other moving parts and are available ommercially in various sizes and for different applications. Jet ejectors have lower capital and maintenance cost than the other con? gurations. On the other hand, the main drawbacks of jet ejectors include the following: ? Ejectors are designed to operate at a single optimum point. Deviation from this optimum results in dramatic deterioration of the ejector performance. 0255-2701/02/$ – see front matter  © 2002 Elsevier Science B. V. All rights reserved. PII: S 0 2 5 5 – 2 7 0 1 ( 0 1 ) 0 0 1 7 6 – 3 552 ? H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 Ejectors have very low thermal ef? iency. Applications of jet ejectors include refrigeration, air conditioning, removal of non-condensable gases, transport of solids and gas recovery. The function of the jet ejector differs considerably in these processes. For example, in refrigeration and air conditioning cycles, the ejector compresses the entrained vapor to higher pressure, which allows for condensation at a higher temperature. Also, the ejector entrainment process sustains the low pressure on the evaporator side, which allows evaporation at low temperature. As a result, the cold evaporator ? uid can be used for refrigeration and cooling functions. As for the removal of non-condensable gases in heat transfer units, the ejector entrainment process prevents their accumulation within condensers or evaporators. The presence of non-condensable gases in heat exchange units reduces the heat transfer ef? ciency and increases the condensation temperature because of their low thermal conductivity. Also, the presence of these gases enhances corrosion reactions. However, the ejector cycle for cooling and refrigeration has lower ef? ciency than the MVC units, but their merits are manifested upon the use of low grade energy that has limited effect on the environment and lower ooling and heating unit cost. Although the construction and operation principles of jet ejectors are well known, the following sections provide a brief summary of the major features of ejectors. This is necessary in order to follow the discussion and analysis that follow. The conventional steam jet ejector has three main parts: (1) the nozzle; (2) the suction chamber; a nd (3) the diffuser (Fig. 1). The nozzle and the diffuser have the geometry of converging/diverging venturi. The diameters and lengths of various parts forming the nozzle, the diffuser and the suction chamber, together with the stream ? ow rate and properties, de? e the ejector capacity and performance. The ejector capacity is de? ned in terms of the ? ow rates of the motive steam and the entrained vapor. The sum of the motive and entrained vapor mass ? ow rates gives the mass ? ow rate of the compressed vapor. You read "Steam Jet Refrigeration Cycle" in category "Essay examples" As for the ejector performance, it is de? ned in terms of entrainment, expansion and compression ratios. The entrainment ratio (w ) is the ? ow rate of the entrained vapor Fig. 1. Variation in stream pressure and velocity as a function of location along the ejector. H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 divided by the flow rate of the motive steam. As for the expansion ratio (Er), it is de? ned as the ratio of the motive steam pressure to the entrained vapor pressure. The compression ratio (Cr) gives the pressure ratio of the compressed vapor to the entrained vapor. Variations in the stream velocity and pressure as a function of location inside the ejector, which are shown in Fig. 1, are explained below: ? The motive steam enters the ejector at point (p ) with a subsonic velocity. ? As the stream ? ows in the converging part of the ejector, its pressure is reduced and its velocity increases. The stream reaches sonic velocity at the nozzle throat, where its Mach number is equal to one. The increase in the cross section area in the diverging part of the nozzle results in a decrease of the shock wave pressure and an increase in its velocity to supersonic conditions. ? At the nozzle outlet plane, point (2), the motive steam pressure becomes lower than the entrained vapor pressure and its velocity ranges between 900 and 1200 m/s. ? The entrained vapor at point (e ) enters the ejector, where its velocity increases and its pressure decreases to that of point (3). ? The motive steam and entrained vapor streams may mix within the suction chamber and the converging section of the diffuser or it may ? ow as two separate treams as it enters the constant cross section area of the diffuser, where mixing occurs. ? In either case, the mixture goes through a shock inside the constant cross section area of the diffuser. The shock is associated with an increase in the mixture pressure and reduction of the mixture velocity to subsonic conditions, point (4). The shock occurs because of the back pressure resistance of the condenser. ? As the subsonic mixture emerges from the constant cross section area of the diffuser, further pressure increase occurs in the diverging section of the diffuser, where part of the kinetic energy of the mixture is converted into pressure. The pressure of the emerging ? uid is slightly higher than the condenser pressure, point (c ). Summary for a number of literature studies on ejector design and performance evaluation is shown in Table 1. The following outlines the main ? ndings of these studies: ? Optimum ejector operation occurs at the critical condition. The condenser pressure controls the location of the shock wave, where an increase in the condenser pressure above the critical point results in a rapid decline of the ejector entrainment ratio, since the shock wave moves towards the nozzle exit. Operating at pressures below the critical points has negligible effect on the ejector entrainment ratio. 553 ? At the critical condition, the ejector entrainment ratio increases at lower pressure for the boiler and condenser. Also, higher temperature for the evaporator increases the entrainment ratio. ? Use of a variable position nozzle can maintain the optimum conditions for ejector operation. As a result, the ejector can be maintained at critical conditions even if the operating conditions are varied. ? Multi-ejector system increases the operating range and improves the overall system ef? ciency. Ejector modeling is essential for better understanding of the compression process, system design and performance evaluation. Models include empirical correlations, such as those by Ludwig [1], Power [2] and El-Dessouky and Ettouney [3]. Such models are limited to the range over which it was developed, which limits their use in investigating the performance of new ejector ? uids, designs or operating conditions. Semi-empirical models give more ? exibility in ejector design and performance evaluation [4,5]. Other ejector models are based on fundamental balance equations [6]. This study is motivated by the need for a simple mpirical model that can be used to design and evaluate the performance of steam jet ejectors. The model is based on a large database extracted from several ejector manufacturers and a number of experimental literature studies. As will be discussed later, the model is simple to use and it eliminates the need for iterative procedures. 2. Mathematical model The review by Sun and Eames [7] outlined the developments in mathematical modeling and design of jet ejectors. The review shows that there are two basic approaches for ejector analysis. These include mixing of the motive steam and entrained vapor, either at constant ressure or at constant area. Design models of stream mixing at constant pressure are more common in literature because the performance o f the ejectors designed by this method is more superior to the constant area method and it compares favorably against experimental data. The basis for modeling the constant pressure design procedure was initially developed by Keenan [6]. Subsequently, several investigators have used the model for design and performance evaluation of various types of jet ejectors. This involved a number of modi? cations in the model, especially losses within the ejector and mixing of the primary and secondary streams. In this section, the constant pressure ejector model is developed. The developed model is based on a number of literature studies [8 – 11]. The constant pressure model is based on the following assumptions: H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 554 Table 1 Summary of literature studies on ejector design and performance Reference Fluid Boiler, evaporator and condenser temperature ( °C) Conclusion [19] R-113 60–100; 5–18; 40–50 Basis for refrigerant selection for solar system, system performance increased with increasing boiler and evaporator temperatures and decreasing condenser temperature. 20] R-113; R-114; R-142b; R-718 80–95; 5–13; 25–45 Comparison of ejector and refrigerant performance. Dry, wet and isentropic ?uids. Wet ? uid damage ejectors due phase change during isentropic expansion. R-113 (dry) has the best performance and R142b (wet) has the poorest performance. [21,22] R-11 4 86; ? 8; 30 Increase in ejector performance using mechanical compression booster. [8] Water 120–140; 5–10; 30–65 Choking of the entrained ? uid in the mixing chamber affects system performance. Maximum COP is obtained at the critical ? ow condition. [13] Water 120–140; 5–10; 30–60 Effect of varying the nozzle position to meet operating condition. Increase in COP and cooling capacity by 100%. [23] R-113 70–100; 6–25; 42–50 Entrainment ratio is highly affected by the condenser temperature especially at low evaporator temperature. [24] R-11 82. 2–182. 2; 10; 43. 3 Entrainment ratio is proportional to boiler temperature. [25,26] R-114 90; 4; 30 Combined solar generator and ejector air conditioner. More ef? cient system requires multi-ejector and cold energy storage (cold storage in either phase changing materials, cold water or ice). [27] R-134A 15; 30 Modeling the effect of motive nozzle on system performance, in which the ejector is used to recover part of the work that would be lost in the expansion valve using high-pressure motive liquid. [28] Water 100–165; 10; 30–45 Combined solar collector, refrigeration and seawater desalination system. Performance depends on steam pressure, cooling water temperature and suction pr essure. [4] Water [29] Water – Model of multistage steam ejector refrigeration system using annular ejector in which the primary ? uid enters the second stage at annular nozzle on the sidewall. This will increase static pressure for low-pressure stream and mixture and reduce the velocity of the motive stream and reduce jet mixing losses shock wave formation losses. [24] R11; R113; R114 93. 3; 10; 43. 3 Measure and calculate ejector entrainment ratio as a function of boiler, condenser and evaporator temperatures. Entrainment ratio decreases for off design operation and increases for the two stage ejectors. [30] R113; R114; R142b 120–140; 65–80 Effect of throat area, location of main nozzle and length of the constant area section on backpressure, entrainment ratio and compression ratio. Developed a new ejector theory in which the entrained ? uid is choked, the plant scale results agree with this theory. Steam jet refrigeration should be designed for the most often prevailing conditions rather than the most severe to achieve greater overall ef? ciency. [5] Mathematical model use empirical parameters that depend solely on geometry. The parameters are obtained experimentally for various types of ejectors. [31] R134a 5; ? 12, ? 18; 40 Combined ejector and mechanical compressor for operation of domestic refrigerator-freezer increases entrainment ratio from 7 to 12. 4%. The optimum throat diameter depends on the freezer emperature [9] R11; HR-123 80; 5; 30 Performance of HR-123 is similar to R-11 in ejector refrigeration. Optimum performance is achieved by the use of variable geometry ejector when operation conditions change. H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 1. The motive steam expands isentropically in the nozzle. Al so, the mixture of the motive steam and the entrained vapor compresses isentropically in the diffuser. 2. The motive steam and the entrained vapor are saturated and their velocities are negligible. 3. Velocity of the compressed mixture leaving the ejector is insigni? cant. 4. Constant isentropic expansion exponent and the ideal gas behavior. 5. The mixing of motive steam and the entrained vapor takes place in the suction chamber. 6. The ? ow is adiabatic. 7. Friction losses are de? ned in terms of the isentropic ef? ciencies in the nozzle, diffuser and mixing chamber. 8. The motive steam and the entrained vapor have the same molecular weight and speci? c heat ratio. 9. The ejector ? ow is one-dimensional and at steady state conditions. The model equations include the following: ? Overall material balance (2) Expansion ratio ? ‘ 2pn k? 1   Pp P2 n (k ? 1/k) ?1 Pe P2 n (k ? 1/k) ?1 (6) M*2 + wM*2 Te/Tp p e ‘ M 2(k + 1) M 2(k ? 1) + 2 (8) Eq. (8) is used to calculate M*2, M*2, M4 e p Mach number of the mixed ? ow after the shock wave 2 M2+ 4 (k ? 1) M5 = (9) 2k 2 M ? 1 (k ? 1) 4 Pressure increase across the shock wave at point 4 (10) In Eq. (10) the constant pressure assumption implies that the pressure between points 2 and 4 remains constant. Therefore, the following equality constraint applies P2 = P3 = P4. Pressure lift in the diffuser  n Pc p (k ? 1) 2 =d M5+1 P5 2 ? (5) ? (k/k ? 1) (11) where pd is the diffuser ef? ciency. The area of the nozzle throat A1 = where M is the Mach number, P is the pressure and is the isentropic expansion coef? cient. In the above equation, pn is the nozzle ef? ciency and is de? ned as the ratio between the actual enthalpy change and the enthalpy change undergone during an isentropic process. Isentropic expansion of the entrained ? uid in the suction chamber is expressed in terms of the Mach number of the entrained ? uid at the nozzle e xit plane   P5 1 + kM 2 4 = P4 1 + kM 2 5 (4) Isentropic expansion of the primary ? uid in the nozzle is expressed in terms of the Mach number of the primary ? uid at the nozzle outlet plane Mp2 = ? ? (3) Er = Pp/Pe ? ? 2 k? 1 (7) (1 + w )(1 + wTe/Tp) here w is the entrainment ratio and M * is the ratio between the local ? uid velocity to the velocity of sound at critical conditions. The relationship between M and M * at any point in the ejector is given by this equation M* = Compression ratio Cr = Pc/Pe ? ? ‘ The mixing process is modeled by one-dimensional continuity, momentum and energy equations. These equations are combined to de? ne the critical Mach number of the mixture at point 5 in terms of the critical Mach number for the primary and entrained ?uids at point 2 M* = 4 where m is the mass ? ow rate and the subscripts c, e and p, de? ne the compressed vapor mixture, the ntrained vapor and the motive steam or primary stream. Entrainment ratio w = me/mp ? ? (1) mp + m e = mc ? Me2 = 555 mp Pp ‘ RTp k + 1 kpn 2 (k + 1)/(k ? 1) (12) The area ratio of the nozzle throat and diffuser constant area        A1 Pc 1 = A3 Pp (1 + w )(1 + w (Te/Tp)) P2 1/k P (k ? 1)/k 1/2 1? 2 Pc Pc 2 1/(k ? 1) 2 1/2 1? k+1 k+1 1/2 (13) H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 556 ? The area ratio of the nozzle throat and the nozzle outlet A2 = A1 ‘  1 2 (k ? 1) 2 1+ M p2 2 M p2 (k + 1 2  ? (k + 1)/(k ? 1) (14) ? 3. Solution procedure ? Two solution procedures for the above model are shown in Fig. 2. Either procedure requires iterative calculations. The ? rst procedure is used for system design, where the system pressures and the entrainment ratio is de? ned. Iterations are made to determine the pressure of the motive steam at the nozzle outlet (P2) that gives the same back pressure (Pc). The iteration sequence for this procedure is shown in Fig. 2(a) and it includes the following steps: ? De? ne the design parameters, which include the entrainment ratio (w ), the ? ow rate of the compressed ? ? ? ? vapor (mc) and the pressures of the entrained vapor, ompressed vapor and motive steam (Pe, Pp, Pc). De? ne the ef? ciencies of the nozzle and diffuser (pn, pd). Calculate the saturation temperatures for the compressed vapor, entrained vapor and motive steam, which include Tc, Tp, Te, using the saturation temperature correlation given in the appendix. As for the universal gas constant and the speci? c heat ratio for steam , their values are taken as 0. 462 and 1. 3. The ? ow rates of the entrained vapor (me) and motive steam (mp) are calculated from Eqs. (1) and (2). A value for the pressure at point 2 (P2) is estimated and Eqs. (5) – (11) are solved sequentially to obtain the ressure of the compressed vapor (Pc). The calculated pressure of the compressed vapor is compared to the design value. A new value for P2 is estimated and the previous step is repeated until the desired value for the pressure of the compressed vapor is reached. Fig. 2. Solution algorithms of the mathematical model. (a) Design procedure to calculate area ratios. (b) Performance evaluation to calculate w. H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 ? The ejector cross section areas (A1, A2, A3) and the area ratios (A1/A3 and A2/A1) are calculated from Eqs. (12) – (14). The second solution procedure is used for performance evaluation, where the cross section areas and the entrainment and motive steam pressures are de? ned. Iterations are made to determine the entrainment ratio that de? nes the ejector capacity. The iteration sequence for this procedure is shown in Fig. 2(b) and it includes the following steps: ? De? ne the performance parameters, which include the cross section areas (A1, A2, A3), the pressures of the entrained vapor (Pe) and the pressure of the primary stream (Pp). ? De? ne the ef? ciencies of the nozzle and diffuser (pn, pd). ? Calculate the saturation temperatures of the primary nd entrained streams, Tp and Te, using the saturation temperature correlation given in the appendix. ? As for the universal gas constant and the speci? c heat ratio for steam, their values are taken as 0. 462 and 1. 3. ? Calculate the ? ow rate of the motive steam and the properties at the nozzle outlet, which include mp, P2, Me2, Mp2. These are obtained by solving Eqs. (5), (6), (12) and (14). ? An estimate is made for the entrainment ratio, w. ? This value is used to calculate other system parameters de? ned in Eqs. (7) – (11), which includes M*2, e M*2, M*, M4, M5, P5, Pc. p 4 ? A new estimate for w is obtained from Eq. 13). ? The error in w is determined and a new iteration is made if necessary. ? The ? ow rates of the compressed and entrained vapor are calculated from Eqs. (1) and (2). 4. Semi-empirical model Development of the semi-empirical model is thought to provide a simple method for designing or rating of steam jet ejectors. As shown above, solution of the mathematical model requires an iterative procedure. Also, it is necessary to de? ne values of pn and pd. The values of these ef? ciencies widely differ from one study to another, as shown in Table 2. The semi-empirical model for the steam jet ejector is developed over a wide ange of operating conditions. This is achieved by using three sets of design data acquir ed from major ejector manufacturers, which includes Croll Reynolds, Graham and Schutte – Koerting. Also, several sets of experimental data are extracted from the literature and are used in the development of the empirical model. The semiempirical model includes a number of correlations to calculate the entrainment ratio (w ), the pressure at the nozzle outlet (P2) and the area ratios in the ejector 557 Table 2 Examples of ejector ef? ciencies used in literature studies Reference [27] [32] [33] [31] [10] [24] [8] [34] pn pd 0. 9 0. 5 0. 7–1 0. 8–1 0. 85–0. 98 0. 85 0. 75 0. 75 0. 8 0. 85 0. 7–1 0. 8–1 0. 65–0. 85 0. 85 0. 9 pm 0. 8 0. 95 (A2/A1) and (A1/A3). The correlation for the entrainment ratio is developed as a function of the expansion ratio and the pressures of the motive steam, the entrained vapor and the compressed vapor. The correlation for the pressure at the nozzle outlet is developed as a function of the evaporator and co ndenser pressures. The correlations for the ejector area ratios are de? ned in terms of the system pressures and the entrainment ratio. Table 3 shows a summary of the ranges of the experimental and the design data. The table also includes the ranges for the data reported by Power [12]. A summary of the experimental data, which is used to develop the semi-empirical model is shown in Table 4. The data includes measurements by the following investigators: ? Eames et al. [8] obtained the data for a compression ratio of 3 – 6, expansion ratio 160 – 415 and entrainment ratio of 0. 17 – 0. 58. The measurements are obtained for an area ratio of 90 for the diffuser and the nozzle throat. ? Munday and Bagster [4] obtained the data for a compression ratio of 1. 8 – 2, expansion ratio of 356 – 522 and entrainment ratio of 0. 57 – 0. 905. The measurements are obtained for an area ratio of 200 for the diffuser and the nozzle throat. ? Aphornratana and Eames [13] obtained the data for a compression ratio of 4. 6 – 5. 3, expansion ratio of 309. 4 and entrainment ratio of 0. 11 – 0. 22. The measurements are obtained for an area ratio of 81 for the diffuser and the nozzle throat. ? Bagster and Bresnahan [14] obtained the data for a compression ratio of 2. 4 – 3. 4, expansion ratio of 165 – 426 and entrainment ratio of 0. 268 – 0. 42. The measurements are obtained for an area ratio of 145 for the diffuser and the nozzle throat. ? Sun [15] obtained the data for a compression ratio of . 06 – 3. 86, expansion ratio of 116 – 220 and entrainment ratio of 0. 28 – 0. 59. The measurements are obtained for an area ratio of 81 for the diffuser and the nozzle throat. ? Chen and Sun [16] obtained the data for a compression ratio of 1. 77 – 2. 76, expansion ratio of 1. 7 â⠂¬â€œ 2. 9 and entrainment ratio of 0. 37 – 0. 62. The measure- H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 558 ments are obtained for an area ratio of 79. 21 for the diffuser and the nozzle throat. ? Arnold et al. [17] obtained the data for a compression ratio of 2. 47 – 3. 86, expansion ratio of 29. 7 – 46. , and entrainment ratio of 0. 27 – 0. 5. ? Everitt and Riffat [18] obtained the data for a compression ratio of 1. 37 – 2. 3, expansion ratio of 22. 6 – 56. 9 and entrainment ratio of 0. 57. The correlation for the entrainment ratio of choked ?ow or compression ratios above 1. 8 is given by W = aErbP cP d ec (e + fP g ) p (h + iP jc) (15) Similarly, the correlation for the entrainment ratio of un-choked ? ow with compression ratios below 1. 8 is given by W = aErbP cP d ec (e + f ln(Pp)) (g + h ln(Pc)) (16) vapor compression applications. As shown in Fig. 3, the ? tting result is very satisfact ory for entrainment ratios between 0. 2 and 1. This is because the major part of the data is found between entrainment ratios clustered over a range of 0. 2 – 0. 8. Examining the experimental data ? t shows that the major part of the data ? t is well within the correlation predictions, except for a small number of points, where the predictions have large deviations. The correlations for the motive steam pressure at the nozzle outlet and the area ratios are obtained semi-empirically. In this regard, the design and experimental data for the entrainment ratio and system pressures are used to solve the mathematical model and to calculate the area ratios and motive steam pressure at the nozzle utlet. The results are obtained for ef? ciencies of 100% for the diffuser, nozzle and mixing and a value of 1. 3 for k. The results are then correlated as a function of the system variables. The following relations give the correlations for the choked ? ow: The constants in Eqs. (15) and (16) are given as follows P2 = 0. 13 P 0. 33P 0. 73 e c (17) A1/A3 = 0. 34 P 1. 09P ? 1. 12w ? 0. 16 c p Entrainment ratio Entrainment ratio correlation choked correlation non-choked ?ow (Eq. (15); Fig. 3) ? ow (Eq. (16), Fig. 4) ?1. 89? 10? 5 ?5. 32 5. 04 9. 05? 10? 2 22. 09 ?6. 13 0. 82 ?3. 37? 10? 5 ? ? 0. 79 a 0. 65 b ?1. 54 c 1. 72 d 6. 9v10? 2 e 22. 82 f 4. 21? 10? 4 g 1. 34 h 9. 32 j 1. 28? 10? 1 j 1. 14 R2 0. 85 A2/A1 = 1. 04 P ? 0. 83 c P 0. 86 p w (18) ? 0. 12 (19) The R 2 for each of the above correlations is above 0. 99. Similarly, the following relations give the correlations for the un-choked ? ow: P2 = 1. 02 P ? 0. 000762P 0. 99 e c (20) A1/A3 = 0. 32 P 1. 11P ? 1. 13w ? 0. 36 c p (21) A2/A1 = 1. 22 P ? 0. 81P 0. 81w ? 0. 0739 c p (22) 2 Fitting results against the design and experimental data are shown in Figs. 3 and 4, respectively. The results shown in Fig. 3 cover the most commonly used range for steam jet ejectors, especially in vacuum and The R values for the above three correlations are above 0. 99. The semi-empirical ejector design procedure involves sequential solution of Eqs. (1) – (14) together with Eq. (17) or Eq. (20) (depending on the ? ow type, choked or non-choked). This procedure is not iterative in contrast with the procedure given for the mathematical model in the previous section. As for the semi-empirical performance evaluation model, it involves non-iterative solution of Eqs. (1) – (14) together with Eq. (15) or Eq. (16) for choked or non-choked ? ow, respectively. It should be stressed that both solution procedures are indepen- Table 3 Range of design and experimental data used in model development Source Er Cr Pe (kPa) Pc (kPa) Pp (kPa) w Experimental Schutte–Koerting Croll–Rynolds Graham Power 1. 4–6. 19 1. 008–3. 73 1. 25–4. 24 1. 174–4. 04 1. 047–5. 018 1. 6–526. 1 1. 36–32. 45 4. 3–429. 4 4. 644–53. 7 2–1000 0. 872–121. 3 66. 85–2100. 8 3. 447–124. 1 27. 58–170. 27 2. 76–172. 37 2. 3–224. 1 790. 8–2859. 22 446. 06–1480. 27 790. 8–1480. 27 3. 72–510. 2 38. 6–1720 84. 09–2132. 27 6. 2–248. 2 34. 47–301. 27 344. 74–2757. 9 0. 11–1. 132 0. 1–4 0. 1818–2. 5 0. 18–3. 23 0. 2–4 H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 559 Table 4 Summary of literature experimental data for steam jet ejectors Ad/At Pp (kPa) Pe (kPa) Pc (kPa) Pp/Pe Pc/Pe w Reference 90 198. 7 232. 3 270. 3 313. 3 361. 6 1. 23 1. 23 1. 23 1. 23 1. 23 3. 8 4. 2 4. 7 5. 3 6 161. 8 189. 1 220. 1 255. 1 294. 4 3. 09 3. 42 3. 83 4. 31 4. 89 0. 59 0. 54 0. 47 0. 39 0. 31 [8] [8] [8] [8] [8] 90 198. 7 232. 3 270. 3 313. 3 361. 6 1. 04 1. 04 1. 04 1. 04 1. 04 3. 6 4. 1 4. 6 5. 1 5. 7 191. 6 223. 9 260. 7 302. 1 348. 7 3. 47 3. 95 4. 44 4. 91 5. 49 0. 5 0. 42 0. 36 0. 29 0. 23 [8] [8] [8] [8] [8] 90 198. 7 232. 3 270. 3 313. 3 361. 6 0. 87 0. 87 0. 87 0. 87 0. 87 3. 4 3. 7 4. 4 5. 1 5. 4 227. 7 266. 2 309. 8 59 414. 4 3. 89 4. 24 5. 04 5. 85 6. 19 0. 4 0. 34 0. 28 0. 25 0. 18 [8] [8] [8] [8] [8] 200 834 400 669 841 690 690 1. 59 1. 59 1. 71 1. 59 1. 94 1. 94 3. 2 3. 07 3. 67 3. 51 3. 38 3. 51 521. 7 250. 2 392. 3 526. 1 356 356 2. 0 1. 92 2. 15 2. 19 1. 74 1. 81 0. 58 1. 13 0. 58 0. 51 0. 86 0. 91 [4] [4] [4] [4] [4] [4] 81 270 270 270 270 270 0. 87 0. 8 7 0. 87 0. 87 0. 87 4. 1 4. 2 4. 4 4. 5 4. 7 309. 5 309. 5 309. 5 309. 5 309. 5 4. 7 4. 8 5. 04 5. 16 5. 39 0. 22 0. 19 0. 16 0. 14 0. 11 [13] [13] [13] [13] [13] 145 660 578 516 440 381 312 278 1. 55 1. 55 1. 58 1. 57 1. 59 1. 62 1. 68 5. 3 5. 3 5. 3 5. 03 4. 77 4. 23 4. 1 426. 5 373. 5 326. 280. 6 239. 9 192. 6 165. 1 3. 42 3. 42 3. 36 3. 21 3 2. 61 2. 44 0. 27 0. 31 0. 35 0. 38 0. 42 0. 46 0. 42 [14] [14] [14] [14] [14] [14] [14] 143. 4 169. 2 198. 7 232. 3 270. 3 1. 23 1. 23 1. 23 1. 23 1. 23 2. 53 2. 67 3. 15 4 4. 75 116. 8 137. 8 161. 8 189. 1 220. 1 2. 06 2. 17 2. 56 3. 26 3. 87 0. 59 0. 51 0. 43 0. 35 0. 29 [15] [15] [15] [15] [15] 29. 7 33. 5 37. 8 46. 5 2. 47 2. 78 3. 14 3. 86 0. 5 0. 4 0. 3 0. 27 [17] [17] [17] [17] 119. 9 151. 7 224. 1 195. 1 195. 1 186. 2 1. 7 2. 3 3. 9 1. 6 1. 9 2. 9 1. 8 2. 2 3. 3 1. 6 1. 9 2. 8 0. 62 0. 49 0. 34 0. 78 0. 64 0. 37 [16] [16] [16] [16] [16] [16] 2. 3 2. 3 2. 3 56. 9 38. 6 22. 6 . 3 1. 9 1. 4 0. 57 0. 56 0. 57 [18] [18] [18] 81 1720 1720 1720 1720 79. 21 116 153 270 198 198 198 57. 9 47. 4 38. 6 57. 7 51. 4 45. 5 37. 01 67. 6 67. 6 67. 6 121. 3 99. 9 67. 6 1. 02 1. 2 1. 7 143 143 143 143 560 H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 wide range of compression, expansion and entrainment ratios, especially those used in industrial applications. The developed correlations are simple and very useful for design and rating calculations, since it can be used to determine the entrainment ratio, which, upon speci? cation of the system load, can be used to determine the motive steam ? w rate and the cross section areas of the ejector. Acknowledgements Fig. 3. Fitting of the entrainment ratio for compression ratios higher than 1. 8. The authors would like to acknowledge funding support of the Kuwait University Research Administration, Project No. EC084 entitled ‘Multiple Effect Evaporation and Absorption/Adsorption Heat Pumps’. Appendix A. Nomenclature A COP Cr Er m M M* Fig. 4. Fitting of the entrainment ratio for compression ratios lower than 1. 8. dent of the nozzle and diffuser ef? ciencies, which varies over a wide range, as shown in Table 2. 5. Conclusions A semi-empirical model is developed for design and erformance evaluation of steam jet ejector. The model includes correlations for the entrainment ratio in choked and non-choked ? ow, the motive steam pressure at the nozzle outlet and the area ratios of the ejector. The correlations for the entrainment ratio are obtained by ? tting against a large set of design data and experimental measurements. In addition, the correlations for the motive steam pressure at the nozzle outlet and the area ratios are obtained semi-empirically by solving the mathematical model using the design and experimental data for the entrainment ratio and system pressures. The correlations cover a P DP R Rs T w cross section area (m2) coef? cient of performance, dimensionless compression ratio de? ned as pressure of compressed vapor to pressure of entrained vapor expansion ratio de? ned as pressure of compressed vapor to pressure of entrained vapor mass ? ow rate (kg/s) Mach number, ratio of ? uid velocity to speed of sound critical Mach number, ratio of ? uid velocity to speed of sound pressure (kPa) pressure drop (kPa) universal gas constant (kJ/kg  °C) load ratio, mass ? ow rate of motive steam to mass ? ow rate of entrained vapor temperature (K) ntrainment ratio, mass ? ow rate of entrained vapor to mass ? ow rate of motive steam Greek symbols k compressibility ratio p ejector ef? ciency Subscripts 1–7 locations inside the ejector b boiler c condenser d diffuser e evaporator or entrained vapor m mixing n nozzle p primary stream or motive steam t throat of the nozzle H. El -Dessouky et al. / Chemical Engineering and Processing 41 (2002) 551 – 561 Appendix B B. 1. Correlations of saturation pressure and temperature   The saturation temperature correlation is given by T = 42. 6776 ? 3892. 7 ? 273. 15 (ln(P /1000) ? 9. 48654) here P is in kPa and T is in  °C. The above correlation is valid for the calculated saturation temperature over a pressure range of 10 – 1750 kPa. The percentage errors for the calculated versus the steam table values are B 0. 1%. The correlation for the water vapor saturation pressure is given by  ln(P /Pc) = Tc ?1 T + 273. 15  8 ? % fi (0. 01(T + 273. 15 ? 338. 15))(i ? 1) i=1 where Tc = 647. 286 K and Pc = 22089 kPa and the values of fi are given in the following table f1 f2 f3 f4 ?7. 419242 0. 29721 ?0. 1155286 0. 008685635 f5 f6 f7 f8 0. 001094098 ?0. 00439993 0. 002520658 ?0. 000521868 How to cite Steam Jet Refrigeration Cycle, Essay examples

Animal Handling and Preparation for Imaging

Question: Discuss about animal handling skills, accommodation and husbandry and review of the animal husbandry techniques? Answer: Risk Assessments The method of effective and safe animal handling technique primarily demands focus on the animals, which are being handled and knowledge to understand and read the body language of the animals (Stout, 2014). Depending upon the body language and the varying scenario, different types of techniques and tools has been developed in recent days, which assists in providing proper and safe animal handling. Therefore, animals with different temperaments in different situation need to be guided with proper animal handling techniques in order to ensure safe and ethical practice (Stout, 2014). A risk of injury or ill health is often associated with the handling techniques. The potentiality of the risk increases if the animals are not being handled frequently or is devoid of human contact for a longer period (Hosey et al. 2013). There are several factors that need to be understood for handling animals with different temperament under different condition. The factors primarily include: The physical and mental ability of the person in terms of handling the animal Equipments availability for e.g. cages, poles, leads etc. The animal being handled which deals with the fact that how familiar the animal is being handled and the likelihood of the animal to get handled. The person associated with handling shall be able to use all the necessary equipments, be aware of the various kind of complications which may rise, be able to work in a calm and confident way thereby implementing proper training methods (Stout, 2014). Thus, it can be clearly stated that for executing a proper decision making strategy, one need to understand the basic factors associated with animal handling (Moberg, 2013). This includes implementation of plans and strategy to understand the availability of the equipments, which involved use of proper handling techniques depending upon the type of animals being handled. Gloves and other protective materials have been used for reducing the risk of injury associated with the animal. Animals are handled with processes with which they are familiar with and were kept away from unfamiliar activities (Rutherford, 2015). In case of aggressive animals, before implementing an alternative method, the review of the method has been generated (Hose y et al. 2013). Lifting and carrying of heavy items has been not practiced as it is associate with causing injury to the animal (Rutherford, 2015). Use of chemical substances has been strictly prohibited as it leads to hazardous effects. Personal hygiene has also been maintained equally thereby maintaining a high standards at all time. Arrangements were also made in order make safe disposal of the infected material. Animal Handling Skills Rabbits are considered to be highly susceptible to the effects of stress and is approached in a calm and confident way such that they dont feel annoyed or disturbed. The rabbit is then restrained firmly by scarf with a hand supporting the animals hindquarters in a proper way for handling or moving. While moving the animal in a new environment, care shall need to be taken such that the rabbit do not remain scared all the time. The rabbit has been kept in a small room provided with one or two litter boxes. A fresh layer of grass hay helps the animal to hop easily in the new home. Fresh water has been kept in a bowl that needs to be kept available to the animal all the time. The animal has been fed with small corns, seeds which minimize the risk for digestive upset (Keeble et al. 2012). Safe handling of the birds, which falls under the class avian, has been achieved by properly controlling the birds feet, hand, legs and wings such that no injury has been caused to the bird. The birds have been grasped firmly in order to avoid putting too much pressure (Jones et al. 2012). In order to so, the handler needs to use appropriate protective clothes, which involves the use of gloves, long sleeved shirts, and other accessories as required. The birds have been lightly wrapped in a small, clean towel, which provides a more protection. Different modes of feeding have been used for the feeding the birds. The method of syringe feeding is used for very small or weak birds that cannot be fed with a spoon. Thus, a syringe is used in a small plastic tube fitted at the end of the syringe (Jones et al. 2012). This particularly ensures that the tube is soft and does not have any sharp edges. The method of feeding has been considered tricky and has been coordinated under expert animal h andlers. Stick or finger feeding method involves the use of a matchstick. The end of the stick is made blunt in a way that the birds do not spike it and the food has been put at the end of the stick into the birds food. The most commercial and common method of feeding is spoon-feeding which includes the use of a plastic teaspoon or a metal teaspoon into the narrow shape which represents the beak of the parent. The birds suck the feed off the spoon and helps in swallowing the food by itself. All the diets have been mixed in a proper way such that it provides a healthy and proper way of feeding technique (Jones et al. 2012). In the case of the amphibians, a small dip net has been used in order to shoo the animal into the net. The opening has been covered with one hand and the net has been turned upward to cover the uppermost part. Another method of handling an amphibian involves moistening of hand, which involves holding the amphibian in hand, but care has been taken in a way that the handling method does not cause any hurt to the amphibian during the process of handling. In general, toxins are produced on a large scale from the body of the amphibians. Therefore, in the case of handling an amphibian, the handler needs to use strong leather or synthetic gloves. Thus, handling techniques need to be precise and ethical. Herps have been feed with insects and they are trained in such a way that putting a dish of insect in front of them they will start keeping feeding for them. In the case of lizards, a pile of chopped vegetables has been used for the feeding purpose (Rendle et al. 2012). Accommodation and Husbandry Good husbandry and accommodation primarily focus on the availability of various kinds of accommodation techniques involved in the case of rabbits, amphibians, and birds. The accommodation of new husbandry techniques helps in understanding and better implementation of the animal handling techniques for ensuring proper and effective care to the mentioned animals (Piedrafita, 2015). The management and care of the animals will help in improving the genetic qualities and behavior of the associated animals as mentioned. For better domestication of animals, animal husbandry needs to be practiced in order to carry forward the effective methods of animal care (Stout, 2014). The available accommodations need to be improved in a way such that the animal finds it free and comfortable with the necessary changes. The introduction of the new accommodation involves the use of effective and strategic implementation that deals with the improvement of the accommodation system. In the case of rabbits, b etter cage needs to be provided in such a way that they find it easy to roam around which causes no actual harm to the rabbit (Keeble et al. 2012). Similarly, for both the birds and amphibians, introducing better recommendation will further help in suitable improvement of the respective accommodation and other animal husbandry techniques. Review of the Animal Husbandry Techniques In accordance with the present topic, it can be shown that proper handling, care, and management methods are implemented in order to provide proper handling for the animals (Huntingford, 2012). The methods that have been used food accommodation, feeding clearly emphasizes on the fact that animals are very sensitive in nature and a good animal handler needs to keep in focus all the available techniques and methods in order to execute better handling and care. Different feeding plans have been excised depending upon the type of organisms. The feeding plans vary from one animal to another and it needs to be kept in mind that the feeding techniques differ from the feeding techniques of other animals and there shall be a clear difference while executing (Stout, 2014). Different techniques have been utilized in the given report which clearly emphasizes on various kinds of plans and records that have been executed in terms of handling rabbits, amphibians, and birds. The animal husbandry met hods thus implemented helps in the understanding of the various facts which supports proper domestication methods that are associated for handling animals with a different mentality and different conditions (Banks et al. 2013). In order to get accustomed to the situation, the different techniques that have been used in the given report help in understanding and developing a clear knowledge regarding the process of domestication, feeding, adaptation, and accommodation (Rutherford, 2015). The commercial method that has been used for the process of breeding is the method of artificial insemination and embryo transfer which guarantees to improve the genetics associated with the given animal (Moberg, 2013). This also helps in understanding regarding the genetic diversity of the animals (Keeble eta al. 2012). The handling and feeding techniques that have been implemented here clearly justifies the technique as because for every animal a separate and a different technique helps in better u nderstanding of the animals temperament and mentality and thus helped us to work accordingly (Banks et al. 2013). References Stout, D. B. (2014). Animal Handling and Preparation for Imaging. InMolecular Imaging of Small Animals(pp. 495-516). Springer New York. Hosey, G., Melfi, V., Pankhurst, S. (2013).Zoo animals: behaviour, management, and welfare. Oxford University Press. Moberg, G. P. (Ed.). (2013).Animal stress. Springer. Rutherford, A. (2015). Animal Transport for Animal Care Professionals. Piedrafita, J. (2015). Teaching of animal breeding. What, when, where?.ITEA,111(4), 348-365. Fryxell, J. M., Sinclair, A. R., Caughley, G. (2014).Wildlife ecology, conservation, and management. John Wiley Sons. Clark, J. A. (2013).Environmental aspects of housing for animal production. Elsevier. Banks, R. E., Sharp, J. M., Doss, S. D., Vanderford, D. A. (2013).Exotic small mammal care and husbandry. John Wiley Sons. Keeble, E., Heggie, H., Varga, M., Lumbis, R., Gott, L. (2012). Mammals: biology and husbandry.BSAVA manual of exotic pet and wildlife nursing, 34-57. Rendle, M., Cracknell, J., Varga, M., Lumbis, R., Gott, L. (2012). Reptiles: biology and husbandry.BSAVA manual of exotic pet and wildlife nursing, 80-108. Jones, R., Dodd, C., Varga, M., Lumbis, R., Gott, L. (2012). Birds: biology and husbandry.BSAVA manual of exotic pet and wildlife nursing, 58-79. Huntingford, F. (Ed.). (2012).The study of animal behaviour. Springer Science Business Media.