Designs of Heat Exchangers Essay Example for Free

Designs of Heat Exchangers Essay Heat transfer from one substance to another plays a major role in the process of some commonly use technology today. The heat transfer is done to control temperature, to heat up a cooler substance, or to cool down a hotter substance. This process is done by a machine called the heat exchanger. The heat exchanger is commonly used in the space heating, in cooling of engines, refrigeration and other processes which need temperature control. They are classified according to their flow arrangement design. One is the parallel-flow design which the two substance flow from the same direction and exit at the same direction also. The other one is the counter-flow design on which the fluids flow on opposite direction. The last one is the cross-flow heat exchanger where the fluids flow perpendicular to each other (Heat Exchanger Design, Inc. 2009). Figure 1. Parallel-flow and Counter-flow Design (Engineering Edge 2009) There are also several types of heat exchangers depending on its design. Some are shell and tube heat exchangers, plate heat exchangers, Regenerative heat exchangers and many others. The shell and tube design of the heat-exchanger consists of two sets of tubes. The first set of tubes is where the cooled or heated fluid flows and on the other set of tubes is the fluid that needed to be heated or cooled. The fluids are separated by the tube’s wall. This design ensures a better protection from leakage because of the tube design. So this design is ideal for the treatment of highly pressurize fluids (Kakac Liu 2002:8). The plate heat exchanger is consisting of multiple, thin and slightly separated plates which allow a larger fluid flow area fro heat transfer. It is said to be more effective than the shell and tube design because it provides more surface area for heat transfer. Additionally, the plate heat exchangers have recent developments on its brazing and gasket that makes it practical to use than other heat exchangers. However, the plate heat exchanger is needs a lot of space and it is more susceptible to leakage (Wang, Sunden Manglik 2007). The regenerative heat exchangers are heat exchangers that make use of the heated fluid after a process to be the heating fluid for the next process. This design can be on a plate or shell and tube structure. The advantages of this type are adapted from the design it is structured. Furthermore, this design brought an economical perspective to the first two designs. On the other hand, this design is only intended for the use of gas substances as fluids (Saunders 1988). Figure 4. Regenerative Heat Exchanger (Defense Research Development Organization 2004) The adiabatic wheel heat exchanger is a machine which uses a third substance, fluid or solid, to transfer heat between the streams. The disadvantage of this design is that there will be a small mixing of the two streams in the process of heat transfer (Saunders 1988). The plate fin heat exchanger is highly used in different industries. The plate-fin heat exchangers utilize plates and finned chambers for relatively high heat transfer. It is preferred by other industries because of its ability to transfer heat with to small difference between the streams. Additionally, it has a compact design and is very lightweight (Kakac Liu 2002:17). Another type is the fluid heat exchangers. The process being done is by showering fluids to a gas stream in an upward direction. The process is used in machines that needed gas cooling and purification at the same time (Saunders 1988). Figure 6. Thermal Fluid Heat Exchanger (Thermotech Industries n. d. ) A waste heat recovery unit is a heat exchanger that recovers waste heat from other mechanism and uses it to transfer heat the fluid being heating. This design is very desirable for refineries and plants since they have an abundant amount of waste heat from their machineries. This design is very economical since waste recycled to something useful (Saunders 1988). Figure 7. Waste Heat Recovery Unit (Turner 2005) Dynamic or scraped surface heat exchangers are heat exchangers that have high maintenance cost because of the constant surface scraping. The scraping is due to the process these machines are used. Such processes are heating and cooling of high-viscosity fluids and other highly fouling substance. However, this design has a sustainable heat transfer and it avoids fouling of the surface of transfer (Saunders 1988). Figure 8. Scraped Surface Heat Exchanger (GEA Niro 2008) The phase-change heat exchangers are machines that utilizes liquid and gas phase in heat transfer. These heat exchangers either heat a liquid to boil and evaporate or cool hot gases to condense. This process is common in distillation set ups. The distillation is a process of which a liquid is heated up and cooled down to remove impurities. It is also used in power plants such as nuclear power plants and fossil fuel plants. These power plants usually use steam driven turbines to generate electricity. In which the steam came from the heat exchange between the heater and the liquid (Saunders 1988). The heat exchangers above are heat exchangers which utilizes a wall to separate the two streams of liquids. The classifications above are based on the design of which how the two streams are separated. However, there are other heat exchangers that do not use walls or separators. These are called direct contact heat exchangers. These heat exchangers use two different phases in heat transfer (Saunders 1988). Figure 9. Phase-changed Heat Exchanger (NationMaster. com 2003) There are other heat exchangers in the market today. Some of these are the multi-phase heat exchangers and spiral heat exchangers. Selecting a proper heat exchanger can be a challenging task. It requires technical knowledge about the designs since there are many factors to be taken into consideration. Some are temperature ranges, the composition of the substance to be heated and pressure limits. That is why the decision about the design is made by a computer program or an engineer. Additionally, large companies and corporations tend to design their own heat exchanger to tend to their needs (Wang, Sunden Manglik 2007). Heat exchangers are seen everywhere without you noticing that they are there. The advances in the technology of heat exchangers can produce better results for engineers, researcher and many industrialists since it will increase the efficiency of the process which common machines have today. List of References Defense Research Development Organization (2004). Mechanical Propulsion System. Technology Focus [online] available from http://www. drdo. org/pub/techfocus/oct04/welcomeoct04. html [17 April 2009] Engineering Edge. (2009). Heat Transfer. [online] available from http://www. engineersedge. com/heat_transfer/parallel_counter_flow_designs. htm [17 April 2009] GEA Niro. (2008). Preheating System. [online] available from http://www. niro. com/niro/CMSDoc. nsf/WebDoc/ndkw5y7gby [17 April 2009] Heat Exchanger Design, Inc. (2009). Shell and Tube Heat Exchanger. [online] available from http://www. hed-inc. com/shell-tube. html [17 April 2009] Kakac, S. Liu, H. (2002). Heat Exchangers: Selection, Rating and Thermal Design (2nd Edition). CRC Press Linde Engineering Division (2005). Plate Fin Heat Exchangers. [online] available from http://www. linde-engineering. com/plant_components/plateheatexchanger_aluminium. php [17 April 2009] NationMaster. com (2003). Heat Exchanger. [online] available from http://www. nationmaster. com/encyclopedia/Heat-exchanger [17 April 2009] Saunders, E. A. (1988). Heat Exchanges: Selection, Design and Construction. New York: Longman Scientific and Technical Thermotech Industries (n. d. ) Products. [online] available from http://www. thermotech-finnedtubes. com/products. htm [17 April 2009] Turner, J. (2005). Making the Most of Waste Energy. Science and Technical Information- National Aeronautics Space Administration [online] available from http://www. sti. nasa. gov/tto/Spinoff2005/er_7. html [17 April 2009] Wang, L. , Sunden, B. , Manglik R. M. (2007). Plate Heat Exchangers: Design, Applications and Performance. Southamton, Boston: WIT Press

Emotional Fundamentalism in River of Earth Essay -- Literary Analysis

James Still's River of Earth presents the bleak realities faced by an Appalachian family that struggles with meeting their most basic needs. The Baldridge's struggle with poverty is surely representative of many Appalachian families during the Depression era. The hardships of poverty, and its psychological and physical effects, are worsened by the isolation and sense of helplessness felt by the characters within River of Earth. Religion functions as the combatant to these struggles; the form of Christianity offered by Still strays from the standard fundamentalist fire-and-brimstone preachings often associated with evangelism in the Appalachian region. Instead, a more emotional form of fundamentalism is found. Religion is a positive, empowering force that is both spiritually and socially freeing for the otherwise repressed and isolated characters within the novel. Within the text, Still offers little escape for the characters. They are grounded and focused on the realities at hand. There is little indulgence in fanciful things or things not of this world. Religion is one of the few escapes the characters are allowed. Still does not offer a standard fundamentalist take on Christianity, despite the strong fundamentalist strains that are often associated with Appalachia. Generally, fundamentalism strongly emphasizes innate depravity and the damnation sinners face. Instead, Still lightens the message. Sermons on hope, grace, and mercy are extended to the characters. Through this more forgiving variety of Christianity, the characters are able to look forward to an eternal existence without adding any more stress to their current existences. It is suggested there is a tendency in Appalachia to lean towards forms of Christianity that pe... ...tianity that thoroughly responded to the needs of individuals. The isolation and desperation found in Depression-era rural Appalachia greatly influenced the type of Christianity that involved in the region. The need for society, community, control, and most significantly, optimism, spawned a form of Christianity that was both social and accommodating to sensitive emotional needs. Works Cited Photiadis, John D., and John F. Schnabel. "Religion: A Persistent Institution In A Changing Appalachia." Review Of Religious Research 19.1 (1977): 32. Academic Search Complete. Web. 3 Apr. 2012. Still, James. River of Earth. Lexington: The University of Kentucky Press, 1978. Print Tillich, Paul. "Paul Tillich on the Method of Correlation." The Christian Theology Reader. Ed. Alister McGrath. West Sussex: Wiley-Blackwell, 2011, 43-46. Print. .

Deception Point Page 61

The chamber looked like a walk-in closet whose ceiling, walls, and floor had been completely covered with foam spires jutting inward from all directions. It reminded Rachel of a cramped underwater cave where stalagmites had run wild, growing off every surface. Most unsettling, however, was the apparent lack of a floor. The floor was a taut, meshed chicken-wire grid strung horizontally across the room like a fishing net, giving the inhabitants the feeling that they were suspended midway up the wall. The mesh was rubberized and stiff beneath the feet. As Rachel gazed down through the webbed flooring, she felt like she was crossing a string bridge suspended over a surrealistic fractalized landscape. Three feet below, a forest of foam needles pointed ominously upward. Instantly upon entering Rachel had sensed the disorientating lifelessness to the air, as if every bit of energy had been sucked out. Her ears felt as if they'd been stuffed with cotton. Only her breath was audible inside her head. She called out, and the effect was that of speaking into a pillow. The walls absorbed every reverberation, making the only perceivable vibrations those inside her head. Now the captain had departed, closing the padded door behind him. Rachel, Corky, and Tolland were seated in the center of the room at a small U-shaped table that stood on long metal stilts that descended through the mesh. On the table were affixed several gooseneck microphones, headphones, and a video console with a fish-eye camera on top. It looked like a mini-United Nations symposium. As someone who worked in the U.S. intelligence community-the world's foremost manufacturers of hard laser microphones, underwater parabolic eavesdroppers, and other hypersensitive listening devices-Rachel was well aware there were few places on earth where one could have a truly secure conversation. The dead room was apparently one of those places. The mics and headphones on the table enabled a face-to-face â€Å"conference call† in which people could speak freely, knowing the vibrations of their words could not escape the room. Their voices, upon entering the microphones, would be heavily encrypted for their long journey through the atmosphere. â€Å"Level check.† The voice materialized suddenly inside their headphones, causing Rachel, Tolland, and Corky to jump. â€Å"Do you read me, Ms. Sexton?† Rachel leaned into the microphone. â€Å"Yes. Thank you.† Whoever you are. â€Å"I have Director Pickering on the line for you. He's accepting AV. I am signing off now. You will have your data stream momentarily.† Rachel heard the line go dead. There was a distant whirr of static and then a rapid series of beeps and clicks in the headphones. With startling clarity, the video screen in front of them sprang to life, and Rachel saw Director Pickering in the NRO conference room. He was alone. His head snapped up and he looked into Rachel's eyes. She felt oddly relieved to see him. â€Å"Ms. Sexton,† he said, his expression perplexed and troubled. â€Å"What in the world is going on?† â€Å"The meteorite, sir,† Rachel said. â€Å"I think we may have a serious problem.† 71 Inside the Charlotte's dead room, Rachel Sexton introduced Michael Tolland and Corky Marlinson to Pickering. Then she took charge and launched into a quick account of the day's incredible chain of events. The NRO director sat motionless as he listened. Rachel told him about the bioluminescent plankton in the extraction pit, their journey onto the ice shelf and discovery of an insertion shaft beneath the meteorite, and finally of their sudden attack by a military team she suspected was Special Ops. William Pickering was known for his ability to listen to disturbing information without so much as flinching an eye, and yet his gaze grew more and more troubled with each progression in Rachel's story. She sensed disbelief and then rage when she talked about Norah Mangor's murder and their own near-death escape. Although Rachel wanted to voice her suspicions of the NASA administrator's involvement, she knew Pickering well enough not to point fingers without evidence. She gave Pickering the story as cold hard facts. When she was finished, Pickering did not respond for several seconds. â€Å"Ms. Sexton,† he finally said, â€Å"all of you†¦ † He moved his gaze to each of them. â€Å"If what you're saying is true, and I cannot imagine why three of you would lie about this, you are all very lucky to be alive.† They all nodded in silence. The President had called in four civilian scientists†¦ and two of them were now dead. Pickering heaved a disconsolate sigh, as if he had no idea what to say next. The events clearly made little sense. â€Å"Is there any way,† Pickering asked, â€Å"that this insertion shaft you're seeing in that GPR printout is a natural phenomenon?† Rachel shook her head. â€Å"It's too perfect.† She unfolded the soggy GPR printout and held it up in front of the camera. â€Å"Flawless.† Pickering studied the image, scowling in agreement. â€Å"Don't let that out of your hands.† â€Å"I called Marjorie Tench to warn her to stop the President,† Rachel said. â€Å"But she shut me down.† â€Å"I know. She told me.† Rachel looked up, stunned. â€Å"Marjorie Tench called you?† That was fast. â€Å"Just now. She's very concerned. She feels you are attempting some kind of stunt to discredit the President and NASA. Perhaps to help your father.† Rachel stood up. She waved the GPR printout and motioned to her two companions. â€Å"We were almost killed! Does this look like some kind of stunt? And why would I-â€Å" Pickering held up his hands. â€Å"Easy. What Ms. Tench failed to tell me was that there were three of you.† Rachel could not recall if Tench had even given her time to mention Corky and Tolland. â€Å"Nor did she tell me you had physical evidence,† Pickering said. â€Å"I was skeptical of her claims before I spoke to you, and now I am convinced she is mistaken. I do not doubt your claims. The question at this point is what it all means.† There was a long silence. William Pickering rarely looked confused, but he shook his head, seeming lost. â€Å"Let's assume for the moment that someone did insert this meteorite beneath the ice. That begs the obvious issue of why. If NASA has a meteorite with fossils in it, why would they, or anyone else for that matter, care where it is found?† â€Å"It appears,† Rachel said, â€Å"that the insertion was performed such that PODS would make the discovery, and the meteorite would appear to be a fragment from a known impact.† â€Å"The Jungersol Fall,† Corky prompted. â€Å"But of what value is the meteorite's association with a known impact?† Pickering demanded, sounding almost mad. â€Å"Aren't these fossils an astounding discovery anywhere and anytime? No matter what meteoritic event they are associated with?† All three nodded. Pickering hesitated, looking displeased. â€Å"Unless†¦ of course†¦ â€Å" Rachel saw the wheels turning behind the director's eyes. He had found the simplest explanation for placing the meteorite concurrent with the Jungersol strata, but the simplest explanation was also the most troubling. â€Å"Unless,† Pickering continued, â€Å"the careful placement was intended to lend credibility to totally false data.† He sighed, turning to Corky. â€Å"Dr. Marlinson, what is the possibility that this meteorite is a counterfeit.† â€Å"Counterfeit, sir?† â€Å"Yes. A fake. Manufactured.† â€Å"A fake meteorite?† Corky gave an awkward laugh. â€Å"Utterly impossible! That meteorite was examined by professionals. Myself included. Chemical scans, spectrograph, rubidium-strontium dating. It is unlike any kind of rock ever seen on earth. The meteorite is authentic. Any astrogeologist would agree.†

The Main Tents Of Ethical Leadership Essay - 1346 Words

The main tents of ethical leadership in public service is for leaders to be transparent, accountable, and professional to have a successful organization. Committed leaders will exemplify professionalism for followers and possessing the motivation to achieve organizational goals. Naturally, to be professional is to comprehend the significance of roles and performance in public service. Accountability is important to the functionality of a public organization. And transparency in public administration is needed to be sure the public has information handy (Haq, 2011). Leaders possess certain skills to distinguish between ethical and unethical acts. Technical, conceptual, interpersonal skills along with emotional and social intelligence contribute to proper understanding of ethical dilemmas, ethical decision making and dissemination and establishment of ethical values. When developed these skills can show leader how to strive for greater ethics oriented in public service (Haq, 2011). LaTisha feels possessing technical skills help a leader to become more efficient and responsive. Therefore, making them informative about rules and regulations that helps to create rule of law, accountability and transparency. It is less likely that unethical behavior would be a factor. In addition, conceptual skills support the leaders in effective planning, organizing and problem solving. These skills are extremely beneficial in the event of ethical dilemmas and conflicts of interest. TheseShow MoreRelatedLeadership Styles And Theories Of Leadership876 Words   |  4 Pagesbstract This paper is to define the definition of leadership, and how its breakdown of various leadership styles and theories. I will also focus on more than one leadership style on what is to believe the best aligns thoughts of what leadership should mean. The leadership style is a mixed character of leadership that combines the transformational and servant leadership theories in to Healthcare. 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