Only Yesterday Essay

The â€Å"Roaring Twenties† as they’re called, was the time of ten years in the Untied States, which saw the greatest change in the public eye, the blast in the economy, and later the destruction of the country. This time in America was a period of financial thriving generally; an incredible social upheaval occurred and saw the development of a cutting edge America. This is the subject, Only Yesterday: An Informal History of the Nineteen-Twenties, composed by Fredrick Lewis Allen. Allen composes an exceptionally useful book of what occurred all through this extraordinary decade, however from the part of a standard person. He composes of the social history of the 1920s, with little to make reference to of significant governmental issues and financial matters. From presidents to mold, Allen covers everything. It’s a powerful glance at individuals during the 1920s, and what life resembled. Just Yesterday starts in May 1919, and closes with a concise glance at 1930 and 1931. The book starts out with a preface pretty much, in which Allen composes of an imaginary couple, the Smith’s, in the year 1919. Allen, through this preface, tells the peruser of the achievements up until 1919, and what is to come in the coming decade. This 14-page presentation lets peruser get a thought of what is to come, inside the book. It starts with a gander at the wartime economy and delayed down from it. The time of the alleged â€Å"Red Scare† is written in detail in this book. Allen composes of the dread during this time, from everything like Attorney-General Mitchell Palmer’s assaults on radicals, work strikes and political agitation, and the narrow mindedness of the mid 1920s. The Ku Klux Klan likewise had a significant influence in this period. The mid 1920s was an extraordinary time of widespread panic, and narrow mindedness for anything â€Å"un-American†. In one such story Allen expounds on, how a dark kid is battered to the point of death in a lake by whites on the shore, in the mid year of 1919. Despite the fact that this existed, the 1920s brought extraordinary change. The primary radio station was in November 2, 1920. Allen discusses the social occasions changing during this time too. Everything from sports to cosmetics was turning into a fixation, similar to baseball and tennis for the folks, and swimsuits and cosmetics for the ladies. During this time new games, for example, Mah Jong from China and crossword puzzles, and new tunes, all which caught the American soul, just as numerous different things, which excited Americans. As Allen composes, â€Å"A not many weeks after the fact there was new national rush as the updates on the finding of the burial chamber of King Tut-Ankh-Amen, cabled right from Egypt, eclipsed the updates on Radical preliminaries and the K.K.K.† This new time was the social upset for the individuals. Women started smoking and drinking openly, skirts got shorter, the utilization of cosmetics, and the journey for slimness started. The twenties was likewise a period of loosened up otherworldliness. Many took a gander at society as more significant than religion. Famous people supplanted religion now and again. The more youthful gernartion scanned for things, for example, energy and excites, and were significantly more open with their sexuality. Charles Lindbergh and his trans-Atlantic flight tossed him to fame. Intriguing others turned into the â€Å"thing to do†, and sexual intrigue was huge. Likewise during this season of social upset, preclusion was going full bore, while the eighteenth amendment was passed, and reduced savoring the nation, it wasn’t extremely viable for various reasons. The horde and Al Capone ran â€Å"bootlegging† of liquor. Racketeering was presented during this time, numerous individuals searching for the pyramid schemes, brought them into criminal operations, for example, smuggling and such. Individuals were simply finding themselves during this time and pubs and social clubs turned into the anger. Ladies would transparently drink and smoke to show their autonomy. Allen discusses the Harding Presidency and the embarrassments that encompassed it. The arrival to commonality as it was called; he restored the administration to the individuals. His embarrassments, which go from sneaking to mystery bars in this season of disallowance, to naming loved ones to the bureau, and numerous others. Allen likewise composes of the Coolidge administration and the flourishing alongside it. The securities exchange was in a blast, and the economy siphoning. The vehicle business powered the economy and radios carried the individuals closer to one another. Under the Coolidge success the â€Å"Big Bull Market† was framed. The financial exchange developed and developed. The economy developed and couldn’t be halted, the stocks became perilously high, yet like every single beneficial thing, it reached a conclusion. The finish of a period occurred in 1929 on September 3, after that costs smashed and kept on falling until October 24, when the market started to consistent once more. However, the market fell considerably increasingly, after that and into 1930â the market would be at an unsurpassed low. Allen credits this to a rundown of seven things running from overproduction to the mind of the American open, all which prompted the Great Depression. This is the exact opposite thing Allen composes, and he poses the inquiry, â€Å"What was to come in the nineteen-thirties?† With the fall of the market, came the fall of independence, as Allen composes, â€Å"As the stock costs fell so did the lengths of the dresses†Ã¢ ¦Ã¢â‚¬  These are the things, which characterized the time of the 1920s: sleek embarrassments, non-otherworldliness, the â€Å"good old days†, and the upheaval, which, fell right when was begun. The 1920s was in no way like America had seen previously. It was come back to the individuals, individuals weren’t hesitant to stand up, or take a stab at something new. What was to come during the 1930s? Another decade, which individuals expected to endure the downturn as opposed to mingle, and it would destroy everything, which was made during the 1920s. Just Yesterday, was an excellent gander at the 1920s. It adequately shows what individuals experienced in this insane time. This book centers around the social history of the â€Å"ëÅ"20s, from women’s skirts to the economy of 1929. Allen offsets this with the governmental issues of the three presidents, which characterized this time. The book is anything but difficult to peruse, and saves the peruser with his straightforward clear and oversimplified style of composing. The book was gigantically getting a charge out of, and catches the eye of the peruser right away. He alludes back to the New York Times, on various events, which is by all accounts one of his essential sources. He utilizes numerous subtleties to back up the narratives wherein he expounds on. While he isn't quite certain in his composition, he fuses a ton of data in the book. He told everything from the great, to the terrible and even to the revolting, which uncovered America’s genuine sense. Just Yeste rday: an extraordinary book for anybody taking a gander at the social history of the 1920s: where independence went out of control and â€Å"normalcy† had returned.

Motorola Case Study Example | Topics and Well Written Essays - 1000 words

Motorola - Case Study Example Moreover, the expanding request of items and administrations it offered from the beginning ends up being a wonderful open door in its part. This implies if this must be applied in the current setting, since Motorola has for quite some time been built up in its industry, the open door is that it gets the opportunity to provide food the expanding and regularly changing business sector needs. Another open door for Motorola is the huge interest for items and administrations it is on top of at present. The presence of LG, Apple Incorporated, Nokia and other related organizations is a proof that the business where Motorola has a place is serious and is a decent setting to lead business that will keep going for long. Apple Incorporated is known for its profoundly inventive items. This implies there are more things to be found in the business where Motorola is locked in at present time. This implies an open door for Motorola to find and rediscover things all alone and acquaint them with the market. The previously mentioned open doors are significant for Motorola. In any case, there are additionally comparing dangers that move against it. The principal critical danger is a battling economy. The 2008 monetary downturn end up being a striking danger on account of Motorola. Financial condition is outside the bound of Motorola’s control and it certainly has critical effect on its part. Its monetary security has hushed up influenced by this. This came about to Motorola’s battling cell phone business which further baffles its partners at the primary concern. Another huge danger is Motorola’s contenders. The changing vital moves of Nokia, Samsung, Sony Ericsson Mobile Communications, LG Electronics, Apple Incorporated and others have immensely made fluctuating upper hand in Motorola’s industry. Every contender is attempting to make their own upper hand since they need to be significantly better than the remainder of the key players in the business ( Porter, 1990; Porter, 1998). For example, the motivation behind why Nokia was not totally hurt by the 2008 monetary downturn was because of its capacity to viably utilize its vital acquisitions, associations and industry driving in innovative work. Apple Incorporated then again is intending to be the top and driving organization of items in their most recent advancement. LG foresees client needs. Samsung is forceful in its venture into creating markets while improving solid brand mindfulness for its top of the line items. In any case, it didn't neglect the way that it needs to altogether deal with its mid-to-low range items to provide food a wide scope of clients. Consider that the contenders of Motorola are critical dangers since they recognize what they have to do in the market and they are unquestionably acceptable at making systems that will push them up to their upper hand. B. Depict the organization's most unmistakable qualities and shortcomings. Motorola’s qualities in clude its capacity to see completely the whole business and the changing needs of the market. This is because of the way that it is the spearheading organization in its industry. Subsequently, it has astounding thoughts that could be transformed into benefit. It has adequately made a name and has for some time been built up contrasted with its rivals. In this, it is highly unlikely that it couldn't outperform the opposition. In this way, what it needs to do currently is seen what the contenders

Suicide Warning Signs and Risk Factors

Suicide Warning Signs and Risk Factors Depression Suicide Print Suicide Risk Factors and Warning Signs By Nancy Schimelpfening Nancy Schimelpfening, MS is the administrator for the non-profit depression support group Depression Sanctuary. Nancy has a lifetime of experience with depression, experiencing firsthand how devastating this illness can be. Learn about our editorial policy Nancy Schimelpfening Medically reviewed by Medically reviewed by Daniel B. Block, MD on January 28, 2020 twitter linkedin Daniel B. Block, MD, is an award-winning, board-certified psychiatrist who operates a private practice in Pennsylvania. Learn about our Medical Review Board Daniel B. Block, MD Updated on February 04, 2020 Martin Dimitrov / istock More in Depression Suicide Causes Symptoms Diagnosis Treatment Types Childhood Depression In This Article Table of Contents Expand Risk Factors Warning Signs Safety Plan Suicide Prevention View All Back To Top Information presented in this article may be triggering to some people. If you are having suicidal thoughts, contact the National Suicide Prevention Lifeline at 1-800-273-8255 for support and assistance from a trained counselor. If you or a loved one are in immediate danger, call 911 immediately. If someone you love has  clinical depression, there is a strong risk that they will at some point think about suicide. Although estimates vary, the U.S. Department of Health and Human Services reports that around 2% of people who have ever had outpatient treatment for depression die by suicide.?? But depression is not the only risk factor for suicide. Suicide accounts for about 1.5% of all worldwide deaths. Other psychiatric conditions including substance use disorders, anxiety disorders, and psychosis can also be risk factors for suicide.?? While there is a strong relationship between mental health and suicide and the risk is serious, it is important to remember that the majority of people with mental health conditions do not attempt or complete suicide. In fact, the Centers for Disease Control and Prevention (CDC) reports that 54% of people who die by suicide did not have a known mental health condition.?? The best way to prevent suicide, according to Suicide Prevention Resources, is to make sure you know the risk factors and warning signs of suicide.?? Risk Factors Risk factors can include both the situations a person experiences and how the person is feeling internally. Though it may be easier to recognize situations and times when suicide is more common, understanding how someone is feeling inside requires a little more detective work. Life Situations Certain conditions and situations are associated with an increased risk of suicide, including:?? Death or terminal illness of a relative or friendDivorce, separation, or the breakup of a relationshipLoss of health (real or imagined)Loss of job, home, money, status, self-esteem, or personal securityDrug or alcohol misuseDepression In addition, there are certain times when people may be more prone to suicidal feelings, such as: Holidays and anniversariesThe first week after discharge from a hospitalWhen treatment with an antidepressant first beginsJust before and after diagnosis of a major illness (for example, the risk of suicide in cancer patients is highest shortly after diagnosis rather than after cancer has spread or progressed)??Just before and during disciplinary proceedings Emotional and Behavioral Changes Emotionally, the suicidal person may be feeling:?? Overwhelming painHopelessnessPowerlessnessWorthlessness, shame, guilt, or self-hatredFear of losing control and harming themselves or others Behaviorally, the person may:?? Appear sad, withdrawn, tired, apathetic, anxious, irritable, or prone to angry outburstsNot be performing well in school, work, or other activitiesBecome socially isolated or fall in with the wrong crowdHave declining interest in sex, friends, or activities previously enjoyedNeglect personal welfare or let their appearance goExperience a change in eating or sleeping habits Types of Suicide Risk Factors There are two different types of suicide risk factors: proximal risk factors and distal risk factors. Proximal risk factors are immediate signs that signal that a suicide attempt may take place such as recent suicidal thoughts, feelings of hopelessness, recent stressful life events, access to firearms, and learning about someone else dying by suicide.Distal factors are background issues or events that can increase the risk of suicide such as comorbid psychiatric conditions, a family history of suicide, and a history of previous suicide attempts. Warning Signs Suicide warning signs which you should be aware of include:?? DepressionPrevious suicide attemptsPreoccupation with deathStatements like, You would be better off without me or I wish I were deadTalking openly about wanting to kill oneselfDevelopment of a suicide plan, acquiring the means to carry it out, rehearsal behavior, or setting a time for the attemptMaking out a will or giving away favorite possessionsInappropriately saying goodbyeMaking ambiguous statements like, You wont have to worry about me anymore, I wish I could go to sleep and never wake up, or I just cant take it anymoreSuddenly switching from being very depressed to being very happy or calm for no apparent reason If You See Warning Signs If you observe any of these warning signs in your loved one, encourage them to seek help from a mental health professional. If they refuse, be persistent. If they appear to be in immediate danger of hurting themselves, do not leave them alone, remove any possible means that they can use to hurt themselves, and get them to an emergency room as soon as possible. Never hesitate to contact the National Suicide Prevention Hotline online or by phone at 1-800-273-8255. Caring counselors are available for free 24 hours a day, 7 days a week. Safety Plan While not exclusive to depression, suicidal thoughts are common among people with depression. If you are living with depression but do not feel suicidal, some people find it helpful to make up a contingency plan on the chance that they may feel suicidal in the future. How to Create a Suicide Safety Plan Suicide Prevention If you dont know if you should be concerned about a loved one and arent ready to take them to the emergency room or call the suicide hotline, here are some things you can do.?? Be Alert Know the risk factors and warning signs. Be particularly concerned if your loved one shows multiple suicide warning signs. Encourage a loved one with depression to seek help. Help them locate treatment resources such as a doctor, therapist, or suicide hotline. Communicate Dont discount your loved ones feelings. Even if a situation seems easily fixable to you that doesnt mean that your loved one sees it the same way. Ask your loved one about suicidal thoughts. Many people are afraid that bringing up the idea of suicide will raise the likelihood it will occur. Thats simply not true. Show Support Express your love. Even if you feel your love should be obvious through your actions, many people craveâ€"and feel validated byâ€"the expression of that love in words. Share your feelings with one another. Your loved one may ask you to keep what they share with you to yourself and not tell anyone. But when it comes to suicide warning signs, not only is that ask not fair to you, but it may be in their best interest to involve others if needed. Use your best judgment, and make your loved ones health and safety your first priority. A Note About Warning Signs While most people who attempt suicide do show some sort of warning signs, there are also those people who, because of social stigma or a desire to not appear weak, will successfully hide what they are feeling. If you fail to recognize that your loved one is considering or considered suicide, do not blame yourself. Remember that you did the best you could with the information you had. How to Help When Someone Is Suicidal

Free Speech vs Hate Speech Essay - 1647 Words

Free Speech vs. Harmful Hate Speech Freedom of speech is instilled at the beginning of the Bill of Rights and it allows citizens of the United States to express their opinions without being afraid of what might happen to them, much like in other countries. Many times people are directly or indirectly harmed by others’ actions that are considered a right under the freedom of speech clause. Though, some people worry that if we do not allow for complete freedom of speech, it is hard to figure out what the limits are. So how can we distinguish between what is covered under our freedom of speech right and what is not if there are no limits? Freedom of speech is a constitutional right given to every citizen, entitling them to voice their†¦show more content†¦In response, the Superintendent issued a ban on all such anti-religious speech. Ironically, the cheerleaders meant no harm, obviously the banner was against a school whose mascot was a Native American. The cheerleaders in turn, sued the school district to preserve their rights to free speech, which resulted in an injunction allowing them to display the banner. â€Å"Free speech prevailed, reminding us of the well-established principle that students do not shed their constitutional rights to freedom of speech or expression at the schoolhouse gate† (Mateer). In a case such as this, where no one was being harmed, an advocacy group came out and stated that the banner indeed racially targeted a group of individuals, when in fact it was not doing anything of the sort. Things like this will always happen, it does not matter if boundaries are placed on the freedom of speech clause or not, there will always be a way to get around it unless the government says â€Å"no one has any freedom of speech.† In this day and age, we are subject to many instances of harmful hate speech, even if it is not directed toward us. The current legal standing in the United States state that the government cannot limit speech on the basis of its content. Thus, speech cannot be censored because its message is racist, religious, sexist, or inspirational. While the prevailing attitude in the American judicialShow MoreRelatedFree Speech vs. Hate Speech Essay1362 Words   |  6 Pageshistory, the United States Constitution has been put to the test over the issue of free speech. The First Amendment states, Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances. Even though free speech is one of the core American values proudly embedded in each citizen, some poopAmericansRead MoreFree Speech Vs Hate Speech Essay769 Words   |  4 PagesFree speech versus hate speech is a very widespread debate as there are convincing arguments on both sides that are very compelling. Although there a re many points commonly used to back up the argument that are false and inaccurate. All Americans have a right to freedom of religion, speech, press, petition, and assembly as depicted in the first amendment, but the exceptions to freedom of speech have never directly been acknowledged by the U.S. Supreme Court. The common slippery-slope argument forRead MoreThe Freedom Of Hate Speech Is Not Freedom Speech1143 Words   |  5 PagesHate Speech is not Freedom Speech Between August 11th and August 12th of 2017, the world watched the disturbance news of what was going on in Charlottesville, Virginia. The horrific videos and images left the world in shock. Groups of white supremacy, nationalists, hitler youths marched in unison screaming, â€Å"White lives matter! Blood and Soils! You will not replace us! Jews will not replace us!† More groups enraged their voices across Virginia to scream hate speech to other races. They threatenedRead MoreHate Speech1536 Words   |  7 PagesHate Speech Essay In the first amendment of the United States constitution, American citizens are guaranteed the right to free speech. This is a fundamental right of American law, and one of the foundations of the U.S. Constitution. It is also the breeding ground for one of the most widely debated issues in America: What, if any, measures should be put into place to regulate hateful language? Most people will agree under one definition or another that hate speech is a socially deviant activityRead MorePaper on Freedom for the Thought That We Hate825 Words   |  4 PagesPaper on Freedom for the Thought that we Hate In the book Freedom for the Thought that we Hate, author Anthony Lewis takes a simply phrased law, the First Amendment and shows how complex freedom of speech really is once put into the real world of freedom, as we know it. He shows through his rejections of absolutism, strong support towards freedom restriction, and objective analysis of Chief Justice Oliver Wendell Holmes, that the United States press is unlike any other in the world. Lewis rejectsRead MoreSpeech On Freedom Of Speech1484 Words   |  6 Pagesof Speech Professor Hunt Culver Stockton College Freedom of Speech Americans have many freedoms that people in other countries can only wish they had. Just imagine a life where you could possibly be killed for speaking your mind and stating your opinion, other countries are living lives like that. According to Katy Davis, The United States ratified the first amendment on December 15th 1791 (Davis, n.d). We as a country don’t know where the government draws the line between hate speechRead MoreWe Must Stop Hate Speech1709 Words   |  7 Pages During the turbulent tides of the 2016 election, the question of whether or not hate speech is protected under the First Amendment has been brought up multiple times. Hate speech is defined by the American Bar Association as â€Å"speech that offends, threatens, or insults groups, based on race, color, religion, national origin, sexual orientation, disability, or other traits.† One side argues that hateful comments should not and are not protected due to the oppression they bring. After all, why wouldRead More The Controversy Over Internet Censorship Essay1152 Words   |  5 Pagescan be accessed at the touch of a button: anything from encyclopedias, to surveys and essays, to articles from magazines, and adult sites.   Anyone who pays for their Internet service is usually offered space for his or her own web page, and even many free services provide space for personal web pages.   All of this available space can be used for any number of reasons: posting newsletters for community groups, advertising for businesses, or just voicing one’s opinion.   For those of us who know how toRead More Censorship and the Internet Essay1213 Words   |  5 Pagesgreater space for free expression in countries where traditional broadcast and print media are restricted† (64). Free expression is a very guarded privilege to United States citizens. Private citizens and businesses can censor what is accessed on their computers to protect themselves, so why would it not be acce ptable for the government to censor what is accessed in order to protect the citizens of the United States of America. Some believe this is an infringement of free speech, while others findRead MoreFree Speech : The Importance Of The Freedom Of Speech1079 Words   |  5 PagesFree speech in my mind, should be universally protected, except when that speech turns into hate against any particular minority and incites violence that is not needed for the safety of the public at large. Freedom of speech serves to be a fundamental democratic right that affords every citizen to participate in the United States constitutional democracy. It is a vital tool because it can be used by every person, rich, poor, black or white, to voice their concerns and rejections of the federal or

Understanding About Term Paper

Understanding About Term Paper For starters, learn about research then understand what are requested to accomplish in a specific project. Research is a rather skilful and precise undertaking. It is the most critical step that will enable students to choose the most appropriate writing companies. A citation is a part of information which you use to back up your arguments in papers. You are able to use any of them and they're never used together. The term papers ought to be in sync with the authentic info and studies that have been done before. The term papers on various levels have various heights of research. You've been assigned a term paper and do not have any idea whatsoever how to write it and you decide to go for one of many term papers services. It's absolutely not possible to say that one part of the expression paper is more essential that the other one. Make tasks more bearable by producing an outline on how you are going to organize your term paper. The express ion paper is normally categorized in two distinct categories like the analytical term papers and argumentative term papers. An individual cannot compose a term paper just by reading a couple of pages of some random text. however, it involves a complete method and procedure. Whenever you have researched on a specific topic, you're expected to use a particular citation style. The students should know the methods and procedures so that if they choose a topic of their own they have a tendency to understand what methodology ought to be followed what style of writing needs to be used and the way the new findings can be written in the papers. Thus every student must understand how to cite a paper and apply the necessary citation style format. Without needing an impressing amount of exploration subject matter your term paper won't be very very likely to definite whole. Everything mentioned in the conclusion ought to depend on the facts and proofs presented in the major body. 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Employing a writing service is the best method to have a well-written essay to use as a guideline to make sure t he essays you write are hitting each one of the essential points and are at the appropriate depth needed for your academic grade. Paper writing is regarded to be the most authentic and dependable means to compose notes and assignments. The customized writing can get easy undertaking for those students who would like to do writings in an excellent way. The Hidden Gem of about Term Paper You could also choose professional customized term paper writing service that is certain to get you satisfied. As soon as you locate a service you want, don't neglect to look at my review of it. It's critical that the service you select knows for sure they're only selecting the very best essay writers. In summary, the service exists, so should you need to use it in order to find a top essay, that's reason enough. The subject of the custom papers is selected by the students by themselves. It can be crucial that you start off with any perform whenever feasible. You've got to compose several ac ademic papers over the duration of a year. There are lots of paper templates to select from, but a lot of the time your instructor will require a particular format for the entire class to follow. The Chronicles of about Term Paper With whomever you choose to support, it's a simple fact that research papers were, are and is going to be a strong portion of a student's academic career. Students ought to be trained for research and term paper is the very best means to do so. Research could possibly be stated as being the absolute most potent and the hardest part and you'll have to understand that may be quizzed of you. It could be pointed out as being the most impressive plus the most challenging part additionally you have got to find out what that may be requested of you. The expression paper writers, i.e. students should take suitable knowledge from different people and distinct resources. Term papers are now an essential portion of the curriculum either it's a school level, college level or university level. It's important for all of the students to have a very clear knowledge on the best way to write a specific paper. Yet another thing a student shouldn't be stern in his approach, your paper has to be treated objectively because your personal affiliations and feelings can impact the credibility of the analysis. Getting the Best about Term Paper There are specific term paper writing services that are currently working for the benefits of students so they may have their assignments written in short time period but with very great quality. It's vital that you just commence together who has any work as shortly as possible. Overall, it's a lengthy procedure and degrades the standard of work. Term papers also make the student to set some true hard work into their researching skills. Make certain you don't do the exact same. The term papers are a type of information conveyed by the folks. Subject Selection The very first thing that is essential in starting your Term Papers is selecting your subject of interest.

Heat Exchanger Free Essays

string(118) " economic optimization it is suggested that the baffles be spaced no closer than 20% of the shell’s inner diameter\." Heat exchanger An interchangeable plate heat exchanger Tubular heat exchanger. A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact. We will write a custom essay sample on Heat Exchanger or any similar topic only for you Order Now [1] They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Contents| Flow arrangement Countercurrent (A) and parallel (B) flows * Fig. 1: Shell and tube heat exchanger, single pass (1–1 parallel flow) * Fig. 2: Shell and tube heat exchanger, 2-pass tube side (1–2 crossflow) * Fig. : Shell and tube heat exchanger, 2-pass shell side, 2-pass tube side (2-2 countercurrent) There are three primary classifications of heat exchangers according to their flow arrangement. In parallel-flow heat exchangers, the two fluids enter the exchanger at the same end, and travel in parallel to one another to the other side. In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is the most efficient, in that it can transfer the most heat from the heat ( transfer) medium due to the fact that the average temperature difference along any unit length is greater. See countercurrent exchange. In a cross-flow heat exchanger, the fluids travel roughly perpendicular to one another through the exchanger. For efficiency, heat exchangers are designed to maximize the surface area of the wall between the two fluids, while minimizing resistance to fluid flow through the exchanger. The exchanger’s performance can also be affected by the addition of fins or corrugations in one or both directions, which increase surface area and may channel fluid flow or induce turbulence. The driving temperature across the heat transfer surface varies with position, but an appropriate mean temperature can be defined. In most simple systems this is the â€Å"log mean temperature difference† (LMTD). Sometimes direct knowledge of the LMTD is not available and the NTU method is used. Types of heat exchangers Shell and tube heat exchanger A Shell and Tube heat exchanger Main article: Shell and tube heat exchanger Shell and tube heat exchangers consist of a series of tubes. One set of these tubes contains the fluid that must be either heated or cooled. The second fluid runs over the tubes that are being heated or cooled so that it can either provide the heat or absorb the heat required. A set of tubes is called the tube bundle and can be made up of several types of tubes: plain, longitudinally finned, etc. Shell and tube heat exchangers are typically used for high-pressure applications (with pressures greater than 30 bar and temperatures greater than 260  Ã‚ °C). [2] This is because the shell and tube heat exchangers are robust due to their shape. Several thermal design features must be considered when designing the tubes in the shell and tube heat exchangers: * Tube diameter: Using a small tube diameter makes the heat exchanger both economical and compact. However, it is more likely for the heat exchanger to foul up faster and the small size makes mechanical cleaning of the fouling difficult. To prevail over the fouling and cleaning problems, larger tube diameters can be used. Thus to determine the tube diameter, the available space, cost and the fouling nature of the fluids must be considered. * Tube thickness: The thickness of the wall of the tubes is usually determined to ensure: * There is enough room for corrosion * That flow-induced vibration has resistance * Axial strength * Availability of spare parts Hoop strength (to withstand internal tube pressure) * Buckling strength (to withstand overpressure in the shell) * Tube length: heat exchangers are usually cheaper when they have a smaller shell diameter and a long tube length. Thus, typically there is an aim to make the heat exchanger as long as physically possible whilst not exceeding production capabilities. However, there are many limitations for this, including space availabl e at the installation site and the need to ensure tubes are available in lengths that are twice the required length (so they can be withdrawn and replaced). Also, long, thin tubes are difficult to take out and replace. * Tube pitch: when designing the tubes, it is practical to ensure that the tube pitch (i. e. , the centre-centre distance of adjoining tubes) is not less than 1. 25 times the tubes’ outside diameter. A larger tube pitch leads to a larger overall shell diameter, which leads to a more expensive heat exchanger. * Tube corrugation: this type of tubes, mainly used for the inner tubes, increases the turbulence of the fluids and the effect is very important in the heat transfer giving a better performance. Tube Layout: refers to how tubes are positioned within the shell. There are four main types of tube layout, which are, triangular (30 °), rotated triangular (60 °), square (90 °) and rotated square (45 °). The triangular patterns are employed to give greater heat transfer as they force the fluid to flow in a more turbulent fashion around the piping. Square patterns are employed where high fouling is experienced a nd cleaning is more regular. * Baffle Design: baffles are used in shell and tube heat exchangers to direct fluid across the tube bundle. They run perpendicularly to the shell and hold the bundle, preventing the tubes from sagging over a long length. They can also prevent the tubes from vibrating. The most common type of baffle is the segmental baffle. The semicircular segmental baffles are oriented at 180 degrees to the adjacent baffles forcing the fluid to flow upward and downwards between the tube bundle. Baffle spacing is of large thermodynamic concern when designing shell and tube heat exchangers. Baffles must be spaced with consideration for the conversion of pressure drop and heat transfer. For thermo economic optimization it is suggested that the baffles be spaced no closer than 20% of the shell’s inner diameter. You read "Heat Exchanger" in category "Papers" Having baffles spaced too closely causes a greater pressure drop because of flow redirection. Consequently having the baffles spaced too far apart means that there may be cooler spots in the corners between baffles. It is also important to ensure the baffles are spaced close enough that the tubes do not sag. The other main type of baffle is the disc and donut baffle, which consists of two concentric baffles. An outer, wider baffle looks like a donut, whilst the inner baffle is shaped like a disk. This type of baffle forces the fluid to pass around each side of the disk then through the donut baffle generating a different type of fluid flow. Fixed tube liquid-cooled heat exchangers especially suitable for marine and harsh applications can be assembled with brass shells, copper tubes, brass baffles, and forged brass integral end hubs. [3] (See: Copper in heat exchangers). Conceptual diagram of a plate and frame heat exchanger. A single plate heat exchanger An interchangeable plate heat exchanger applied to the system of a swimming pool Plate heat exchanger Main article: Plate heat exchanger Another type of heat exchanger is the plate heat exchanger. One is composed of multiple, thin, slightly separated plates that have very large surface areas and fluid flow passages for heat transfer. This stacked-plate arrangement can be more effective, in a given space, than the shell and tube heat exchanger. Advances in gasket and brazing technology have made the plate-type heat exchanger increasingly practical. In HVAC applications, large heat exchangers of this type are called plate-and-frame; when used in open loops, these heat exchangers are normally of the gasket type to allow periodic disassembly, cleaning, and inspection. There are many types of permanently bonded plate heat exchangers, such as dip-brazed, vacuum-brazed, and welded plate varieties, and they are often specified for closed-loop applications such as refrigeration. Plate heat exchangers also differ in the types of plates that are used, and in the configurations of those plates. Some plates may be stamped with â€Å"chevron†, dimpled, or other patterns, where others may have machined fins and/or grooves. Plate and shell heat exchanger A third type of heat exchanger is a plate and shell heat exchanger, which combines plate heat exchanger with shell and tube heat exchanger technologies. The heart of the heat exchanger contains a fully welded circular plate pack made by pressing and cutting round plates and welding them together. Nozzles carry flow in and out of the platepack (the ‘Plate side’ flowpath). The fully welded platepack is assembled into an outer shell that creates a second flowpath ( the ‘Shell side’). Plate and shell technology offers high heat transfer, high pressure, high operating temperature, compact size, low fouling and close approach temperature. In particular, it does completely without gaskets, which provides security against leakage at high pressures and temperatures. Adiabatic wheel heat exchanger A fourth type of heat exchanger uses an intermediate fluid or solid store to hold heat, which is then moved to the other side of the heat exchanger to be released. Two examples of this are adiabatic wheels, which consist of a large wheel with fine threads rotating through the hot and cold fluids, and fluid heat exchangers. Plate fin heat exchanger Main article: Plate fin heat exchanger This type of heat exchanger uses â€Å"sandwiched† passages containing fins to increase the effectiveness of the unit. The designs include crossflow and counterflow coupled with various fin configurations such as straight fins, offset fins and wavy fins. Plate and fin heat exchangers are usually made of aluminium alloys, which provide high heat transfer efficiency. The material enables the system to operate at a lower temperature and reduce the weight of the equipment. Plate and fin heat exchangers are mostly used for low temperature services such as natural gas, helium and oxygen liquefaction plants, air separation plants and transport industries such as motor and aircraft engines. Advantages of plate and fin heat exchangers: High heat transfer efficiency especially in gas treatment * Larger heat transfer area * Approximately 5 times lighter in weight than that of shell and tube heat exchanger. * Able to withstand high pressure Disadvantages of plate and fin heat exchangers: * Might cause clogging as the pathways are very narrow * Difficult to clean the pathways * Aluminum alloys are susceptible to Mercury Liquid Embrittlement Failure Pillow plate heat exchanger A pillow plate exchanger is commonly used in the dairy industry for cooling milk in large direct-expansion stainless steel bulk tanks. The pillow plate allows for cooling across nearly the entire surface area of the tank, without gaps that would occur between pipes welded to the exterior of the tank. The pillow plate is constructed using a thin sheet of metal spot-welded to the surface of another thicker sheet of metal. The thin plate is welded in a regular pattern of dots or with a serpentine pattern of weld lines. After welding the enclosed space is pressurized with sufficient force to cause the thin metal to bulge out around the welds, providing a space for heat exchanger liquids to flow, and creating a characteristic appearance of a swelled pillow formed out of metal. Fluid heat exchangers This is a heat exchanger with a gas passing upwards through a shower of fluid (often water), and the fluid is then taken elsewhere before being cooled. This is commonly used for cooling gases whilst also removing certain impurities, thus solving two problems at once. It is widely used in espresso machines as an energy-saving method of cooling super-heated water to use in the extraction of espresso. Waste heat recovery units A Waste Heat Recovery Unit (WHRU) is a heat exchanger that recovers heat from a hot gas stream while transferring it to a working medium, typically water or oils. The hot gas stream can be the exhaust gas from a gas turbine or a diesel engine or a waste gas from industry or refinery. They can also be integrated into a heatcatcher system that allows an ORC[further explanation needed] generator to produce waste heat to power. Dynamic scraped surface heat exchanger Another type of heat exchanger is called â€Å"(dynamic) scraped surface heat exchanger†. This is mainly used for heating or cooling with high-viscosity products, crystallization processes, evaporation and high-fouling applications. Long running times are achieved due to the continuous scraping of the surface, thus avoiding fouling and achieving a sustainable heat transfer rate during the process. Phase-change heat exchangers Typical kettle reboiler used for industrial distillation towers Typical water-cooled surface condenser In addition to heating up or cooling down fluids in just a single phase, heat exchangers can be used either to heat a liquid to evaporate (or boil) it or used as condensers to cool a vapor and condense it to a liquid. In chemical plants and refineries, reboilers used to heat incoming feed for distillation towers are often heat exchangers. 4][5] Distillation set-ups typically use condensers to condense distillate vapors back into liquid. Power plants that use steam-driven turbines commonly use heat exchangers to boil water into steam. Heat exchangers or similar units for producing steam from water are often called boilers or steam generators. In the nuclear power plants called pressurized w ater reactors, special large heat exchangers pass heat from the primary (reactor plant) system to the secondary (steam plant) system, producing steam from water in the process. These are called steam generators. All fossil-fueled and nuclear power plants using steam-driven turbines have surface condensers to convert the exhaust steam from the turbines into condensate (water) for re-use. [6][7] To conserve energy and cooling capacity in chemical and other plants, regenerative heat exchangers can transfer heat from a stream that must be cooled to another stream that must be heated, such as distillate cooling and reboiler feed pre-heating. This term can also refer to heat exchangers that contain a material within their structure that has a change of phase. This is usually a solid to liquid phase due to the small volume difference between these states. This change of phase effectively acts as a buffer because it occurs at a constant temperature but still allows for the heat exchanger to accept additional heat. One example where this has been investigated is for use in high power aircraft electronics. Direct contact heat exchangers Direct contact heat exchangers involve heat transfer between hot and cold streams of two phases in the absence of a separating wall. [8] Thus such heat exchangers can be classified as: * Gas – liquid * Immiscible liquid – liquid Solid-liquid or solid – gas Most direct contact heat exchangers fall under the Gas- Liquid category, where heat is transferred between a gas and liquid in the form of drops, films or sprays. [2] Such types of heat exchangers are used predominantly in air conditioning, humidification, industrial hot water heating, water cooling and condensing plants. [9] Phases[10]| Continuous phase| Driving force| Change of phase| Examples| Gas – Liquid| Gas| Gravity| No| Spray columns, packed columns| | | | Yes| Cooling towers, falling droplet evaporators| | | Forced| No| Spray coolers/quenchers| | Liquid flow| Yes| Spray condensers/evaporation, jet condensers| | Liquid| Gravity| No| Bubble columns, perforated tray columns| | | | Yes| Bubble column condensers| | | Forced| No| Gas spargers| | | Gas flow| Yes| Direct contact evaporators, submerged combustion| HVAC air coils One of the widest uses of heat exchangers is for air conditioning of buildings and vehicles. This class of heat exchangers is commonly called air coils, or just coils due to their often-serpentine internal tubing. Liquid-to-air, or air-to-liquid HVAC coils are typically of modified crossflow arrangement. In vehicles, heat coils are often called heater cores. On the liquid side of these heat exchangers, the common fluids are water, a water-glycol solution, steam, or a refrigerant. For heating coils, hot water and steam are the most common, and this heated fluid is supplied by boilers, for example. For cooling coils, chilled water and refrigerant are most common. Chilled water is supplied from a chiller that is potentially located very far away, but refrigerant must come from a nearby condensing unit. When a refrigerant is used, the cooling coil is the evaporator in the vapor-compression refrigeration cycle. HVAC coils that use this direct-expansion of refrigerants are commonly called DX coils. Some DX coils are â€Å"microchannel† type. [11] On the air side of HVAC coils a significant difference exists between those used for heating, and those for cooling. Due to psychrometrics, air that is cooled often has moisture condensing out of it, except with extremely dry air flows. Heating some air increases that airflow’s capacity to hold water. So heating coils need not consider moisture condensation on their air-side, but cooling coils must be adequately designed and selected to handle their particular latent (moisture) as well as the sensible (cooling) loads. The water that is removed is called condensate. For many climates, water or steam HVAC coils can be exposed to freezing conditions. Because water expands upon freezing, these somewhat expensive and difficult to replace thin-walled heat exchangers can easily be damaged or destroyed by just one freeze. As such, freeze protection of coils is a major concern of HVAC designers, installers, and operators. The introduction of indentations placed within the heat exchange fins controlled condensation, allowing water molecules to remain in the cooled air. This invention allowed for refrigeration without icing of the cooling mechanism. [12] The heat exchangers in direct-combustion furnaces, typical in many residences, are not ‘coils’. They are, instead, gas-to-air heat exchangers that are typically made of stamped steel sheet metal. The combustion products pass on one side of these heat exchangers, and air to heat on the other. A cracked heat exchanger is therefore a dangerous situation that requires immediate attention because combustion products may enter living space. Spiral heat exchangers Schematic drawing of a spiral heat exchanger. A spiral heat exchanger (SHE), may refer to a helical (coiled) tube configuration, more generally, the term refers to a pair of flat surfaces that are coiled to form the two channels in a counter-flow arrangement. Each of the two channels has one long curved path. A pair of fluid ports are connected tangentially to the outer arms of the spiral, and axial ports are common, but optional. [13] The main advantage of the SHE is its highly efficient use of space. This attribute is often leveraged and partially reallocated to gain other improvements in performance, according to well known tradeoffs in heat exchanger design. A notable tradeoff is capital cost vs operating cost. ) A compact SHE may be used to have a smaller footprint and thus lower all-around capital costs, or an over-sized SHE may be used to have less pressure drop, less pumping energy, higher thermal efficiency, and lower energy costs. Construction The distance between the sheets in the spiral channels are maintained by usi ng spacer studs that were welded prior to rolling. Once the main spiral pack has been rolled, alternate top and bottom edges are welded and each end closed by a gasketed flat or conical cover bolted to the body. This ensures no mixing of the two fluids occurs. Any leakage is from the periphery cover to the atmosphere, or to a passage that contains the same fluid. [14] Self cleaning SHEs are often used in the heating of fluids that contain solids and thus tend to foul the inside of the heat exchanger. The low pressure drop lets the SHE handle fouling more easily. The SHE uses a â€Å"self cleaning† mechanism, whereby fouled surfaces cause a localized increase in fluid velocity, thus increasing the drag (or fluid friction) on the fouled surface, thus helping to dislodge the blockage and keep the heat exchanger clean. The internal walls that make up the heat transfer surface are often rather thick, which makes the SHE very robust, and able to last a long time in demanding environments. † They are also easily cleaned, opening out like an oven where any build up of foulant can be removed by pressure washing. Self-Cleaning Water filters are used to keep the system clean and running wi thout the need to shut down or replace cartridges and bags. Flow arrangements Concurrent and countercurrent flow. There are three main types of flows in a spiral heat exchanger: 1. Counter-current Flow: Fluids flow in opposite directions. These are used for liquid-liquid, condensing and gas cooling applications. Units are usually mounted vertically when condensing vapour and mounted horizontally when handling high concentrations of solids. 2. Spiral Flow/Cross Flow: One fluid is in spiral flow and the other in a cross flow. Spiral flow passages are welded at each side for this type of spiral heat exchanger. This type of flow is suitable for handling low density gas, which passes through the cross flow, avoiding pressure loss. It can be used for liquid-liquid applications if one liquid has a considerably greater flow rate than the other. . Distributed Vapour/Spiral flow: This design is that of a condenser, and is usually mounted vertically. It is designed to cater for the sub-cooling of both condensate and non-condensables. The coolant moves in a spiral and leaves via the top. Hot gases that enter leave as condensate via the bottom outlet. Applications The SHE is good for applications such as pasteurization, digester h eating, heat recovery, pre-heating (see: recuperator), and effluent cooling. For sludge treatment, SHEs are generally smaller than other types of heat exchangers. [citation needed] Selection Due to the many variables involved, selecting optimal heat exchangers is challenging. Hand calculations are possible, but many iterations are typically needed. As such, heat exchangers are most often selected via computer programs, either by system designers, who are typically engineers, or by equipment vendors. To select an appropriate heat exchanger, the system designers (or equipment vendors) would firstly consider the design limitations for each heat exchanger type. Though cost is often the primary criterion, several other selection criteria are important: * High/low pressure limits * Thermal performance Temperature ranges * Product mix (liquid/liquid, particulates or high-solids liquid) * Pressure drops across the exchanger * Fluid flow capacity * Cleanability, maintenance and repair * Materials required for construction * Ability and ease of future expansion * Material selection, such as copper, aluminum, carbon steel, stainless steel, nickel alloys, and titanium. Small-diamete r coil technologies are becoming more popular in modern air conditioning and refrigeration systems because they have better rates of heat transfer than conventional sized condenser and evaporator coils with round copper tubes and aluminium or opper fin that have been the standard in the HVAC industry. Small diameter coils can withstand the higher pressures required by the new generation of environmentally friendlier refrigerants. Two small diameter coil technologies are currently available for air conditioning and refrigeration products: copper microgroove[15] and brazed aluminium microchannel. [16] Choosing the right heat exchanger (HX) requires some knowledge of the different heat exchanger types, as well as the environment where the unit must operate. Typically in the manufacturing industry, several differing types of heat exchangers are used for just the one process or system to derive the final product. For example, a kettle HX for pre-heating, a double pipe HX for the ‘carrier’ fluid and a plate and frame HX for final cooling. With sufficient knowledge of heat exchanger types and operating requirements, an appropriate selection can be made to optimise the process. [17] Monitoring and maintenance Online monitoring of commercial heat exchangers is done by tracking the overall heat transfer coefficient. The overall heat transfer coefficient tends to decline over time due to fouling. U=Q/A? Tlm By periodically calculating the overall heat transfer coefficient from exchanger flow rates and temperatures, the owner of the heat exchanger can estimate when cleaning the heat exchanger is economically attractive. Integrity inspection of plate and tubular heat exchanger can be tested in situ by the conductivity or helium gas methods. These methods confirm the integrity of the plates or tubes to prevent any cross contamination and the condition of the gaskets. Mechanical integrity monitoring of heat exchanger tubes may be conducted through Nondestructive methods such as eddy current testing. Fouling Main article: Fouling A heat exchanger in a steam power station contaminated with macrofouling. Fouling occurs when impurities deposit on the heat exchange surface. Deposition of these impurities can decrease heat transfer effectiveness significantly over time and are caused by: * Low wall shear stress * Low fluid velocities * High fluid velocities * Reaction product solid precipitation * Precipitation of dissolved impurities due to elevated wall temperatures The rate of heat exchanger fouling is determined by the rate of particle deposition less re-entrainment/suppression. This model was originally proposed in 1959 by Kern and Seaton. Crude Oil Exchanger Fouling. In commercial crude oil refining, crude oil is heated from 21  °C to 343  °C prior to entering the distillation column. A series of shell and tube heat exchangers typically exchange heat between crude oil and other oil streams to heat the crude to 260  °C prior to heating in a furnace. Fouling occurs on the crude side of these exchangers due to asphaltene insolubility. The nature of asphaltene solubility in crude oil was successfully modeled by Wiehe and Kennedy. 18] The precipitation of insoluble asphaltenes in crude preheat trains has been successfully modeled as a first order reaction by Ebert and Panchal[19] who expanded on the work of Kern and Seaton. Cooling Water Fouling. Cooling water systems are susceptible to fouling. Cooling water typically has a high total dissolved solids content and suspended colloidal solids. Localized precipitation of dissolved solids occurs at the heat e xchange surface due to wall temperatures higher than bulk fluid temperature. Low fluid velocities (less than 3  ft/s) allow suspended solids to settle on the heat exchange surface. Cooling water is typically on the tube side of a shell and tube exchanger because it’s easy to clean. To prevent fouling, designers typically ensure that cooling water velocity is greater than 0. 9 m/s and bulk fluid temperature is maintained less than 60  °C. Other approaches to control fouling control combine the â€Å"blind† application of biocides and anti-scale chemicals with periodic lab testing. Maintenance Plate heat exchangers must be disassembled and cleaned periodically. Tubular heat exchangers can be cleaned by such methods as acid cleaning, sandblasting, high-pressure water jet, bullet cleaning, or drill rods. In large-scale cooling water systems for heat exchangers, water treatment such as purification, addition of chemicals, and testing, is used to minimize fouling of the heat exchange equipment. Other water treatment is also used in steam systems for power plants, etc. to minimize fouling and corrosion of the heat exchange and other equipment. A variety of companies have started using water borne oscillations technology to prevent biofouling. Without the use of chemicals, this type of technology has helped in providing a low-pressure drop in heat exchangers. In nature Humans The human nasal passages serve as a heat exchanger, which warms air being inhaled and cools air being exhaled. You can demonstrate its effectiveness by putting your hand in front of your face and exhaling, first through your nose and then through your mouth. Air exhaled through your nose is substantially cooler. [20][21] In species that have external testes (such as humans), the artery to the testis is surrounded by a mesh of veins called the pampiniform plexus. This cools the blood heading to the testis, while reheating the returning blood. Birds, fish, marine mammals Countercurrent exchange conservation circuit Further information: Countercurrent exchange in biological systems â€Å"Countercurrent† heat exchangers occur naturally in the circulation system of fish, whales and other marine mammals. Arteries to the skin carrying warm blood are intertwined with veins from the skin carrying cold blood, causing the warm arterial blood to exchange heat with the cold venous blood. This reduces the overall heat loss in cold waters. Heat exchangers are also present in the tongue of baleen whales as large volumes of water flow through their mouths. 22][23] Wading birds use a similar system to limit heat losses from their body through their legs into the water. Carotid rete The carotid rete is a counter-current heat exchanging organ in some ungulates. The blood ascending the carotid arteries on its way to the brain, flows via a network of vessels where heat is discharged to the veins of cooler blood descending from the nasal passages. The carotid rete allows Thomson’s gazelle to maintain its brain almost 3 °C cooler than the rest of the body, and therefore aids in tolerating bursts in metabolic heat roduction such as associated with outrunning cheetahs (during which the body temperature exceeds the maximum temperature at which the brain could function). [24] In industry Heat exchangers are widely used in industry both for cooling and heating large scale industrial processes. The type and size of heat exchanger used can be tailored to suit a process depending on the type of fluid, its phase, temperature, density, viscosity, pressures, chemical composition and various other thermodynamic properties. In many industrial processes there is waste of energy or a heat stream that is being exhausted, heat exchangers can be used to recover this heat and put it to use by heating a different stream in the process. This practice saves a lot of money in industry, as the heat supplied to other streams from the heat exchangers would otherwise come from an external source that is more expensive and more harmful to the environment. Heat exchangers are used in many industries, including: * Waste water treatment Refrigeration * Wine and beer making * Petroleum refining In waste water treatment, heat exchangers play a vital role in maintaining optimal temperatures within anaerobic digesters to promote the growth of microbes that remove pollutants. Common types of heat exchangers used in this application are the double pipe heat exchanger as well as the plate and frame heat exchanger. In aircraft In commercial aircraft heat exchangers are used to take heat from the engine’s oil system to hea t cold fuel. 25] This improves fuel efficiency, as well as reduces the possibility of water entrapped in the fuel freezing in components. [26] Early 2008, a Boeing 777 flying as British Airways Flight 38 crashed just short of the runway. In an early-2009 Boeing-update sent to aircraft operators, the problem was identified as specific to the Rolls-Royce engine oil-fuel flow heat exchangers. [26] Other heat exchangers, or Boeing 777 aircraft powered by GE or Pratt and Whitney engines, were not affected by the problem. [26] How to cite Heat Exchanger, Papers

Internet Appliances Have Arrived Essays - Classes Of Computers

Internet Appliances Have Arrived This article was about a new kind of devices referred to as Internet Appliances. These devices look like small PCs but they only come with the online essentials: a screen, a keyboard, a modem, and a browser (no hard disk or floppy drive). These devices are directed at consumers who are interested in only using the Internet. Three devices were tested and described: Microsoft Network Companions from Compaq and Vestel, and the New Internet Computer (NIC). The two Microsoft Network units were very similar in design. They both have an embedded mouse and keyboards with short cut keys. A bad point of these machines is that they only function with Microsoft Network as the Internet service provider, which can result in a large amount of money as an overall investment. As far as price is concerned, the Vestel unit did not have a set price at the time of publication while the Compaq retails at $599.00. Up to $400.00 of that amount is available for Microsoft Network rebate. The rebate amount varies with the length of the contract. Overall both machines should be sufficient for first time Internet users. The third device, The New Internet Computer (NIC) is the opposite of the Microsoft network machines. NIC is the most computer-like of the three appliances. Included with the device is a small vertical case, two stand-alone speakers, a tabletop mouse with a mouse pad, and a full size keyboard without shortcut buttons. The price for the NIC is a modest $200.00 plus $130.00 for the 15 monitor. NetZero is one of the units default Internet service provider options. This is a nice option because you wont have to pay a monthly fee for Internet service. From the information given in the article the NIC seems to be the most reasonable of the three. For beginners the cheapest of the three makes the most sense. Bibliography Olafson, Peter. Are PCs Toast? Internet Appliances Have Arrived. PC World, November 2000: 70 Computers Essays