BODY Mechanical refrigeration based on the vapor compression cycle was first demonstrated in the 1830s and for the next century a broad range of substances were used; these included toxic compounds, such as sulfur dioxide, as well as refrigerants still in widespread use, such as ammonia. The widespread adoption of home refrigerators in the 1930s spurred the development of nonflammable and low-toxicity refrigerants, and the CFC (chlorofluorocarbon) and later HCFC refrigerants dominated this “second generation” of fluids. Refrigerants are the working fluids in refrigeration, air-conditioning, and heat-pumping systems. They absorb heat from one area, such as an air-conditioned space, and reject it into another, such as outdoors, …show more content…
There is no single setoff optimum characteristics (especially for thermodynamic properties), and often there are tradeoffs among desirable characteristics. Thus, a variety of refrigerants having a range of properties is needed to meet the requirements of various applications. A broad range of fluids has been used as refrigerants over the years, and current usage is dominated by a range of fluorinated chemicals, known as HFCs, in addition to hydrocarbons and several inorganic compounds, including ammonia and carbon dioxide …show more content…
The thermodynamic characteristics (most importantly normal boiling point, critical temperature, and heat capacity) must be matched to the application for the system to operate efficiently. Here there is no single set of optimum values, and a variety of refrigerants having a range of properties is needed to meet the requirements of various applications. Favorable transport properties (low viscosity and high thermal conductivity) have an impact on the size of the heat exchangers and thus cost of the overall system. Energy efficiency, along with the ozone depletion potential and global warming potential are key environmental criteria. Environmental impacts related to ozone depletion drove the phase out of the CFC and HCFC refrigerants. Global climate change concerns have focused attention on the HFC refrigerants. The atmospheric lifetime of a refrigerant affects both ODP and GWP; low values are associated with short atmospheric lifetimes. Here there is often a direct conflict between the need for chemical stability (within the sealed refrigeration system) and the need for chemical breakdown if a refrigerant is released to the
Air Conditioning Heating & Refrigeration News, 217(6),
Article 1 David Nelson Crosthwait Jr was born in Nashville, Tennessee on May 27th in 1898. He is and african american pioneer in the field of heating and air conditioning. He is best known for heating up Radio City Music City in New York City. Crosthwait grew up in Kansas City,Missouri, where he attended all-black school. His parents were very encouraging and challenged him to do experiments and to make designs.
h. Gas chamber In this method of execution the prisoner is restrained and sealed in an airtight chamber and dropped hydrochloric acid potassium cyanide or sodium cyanide crystals which producing hydrocyanic gas. This gas destroys the body's ability to process blood hemoglobin, and unconsciousness can occur within a few seconds if the prisoner takes a deep breath. Death usually occurs within six to 18 minutes. After the pronouncement of death the chamber is evacuated through carbon and neutralizing filters.
In scientific writing being able to identify and use audience, context, and purpose correctly in scientific writing is very helpful in providing what the specific paper will be about (context), who it is targeted toward (audience), and what is the reasoning behind the given section of a reading (purpose). Aristotle was once quoted saying, “Rhetoric is the art of seeing, in any given case, the available means of persuasion.” Being able to dissect someone's stance on an argument is a very important skill to have. Just because someone is able to publish a paper on a certain topic does not mean you should immediately accept everything in that paper. In the scientific journal titled, “The Delphic Oracle:
The history of steamboats is quite interesting. Back before cars and trains existed, rivers were used for trasportation. The travels they often took were slow because speed of travel depended on the river current, and manpower. That is, until, the 1800s where steamboats could reach up to speeds of 5 miles per hour. After they realized they could reach such speeds, the men started river travel and trade.
The HCFC was one of the first replacements to the CFC, it is less harmful to the ozone, but has an increased
The inspiration of Dome-Fridge was came from the working principle of the igloo by the Eskimos. As Figure 1 displayed, the appearance of Dome-Fridge looks similarly to an igloo, which both of them are having a dome-shaped structure. However, the structure and functions carried out by igloos and Dome-Fridge are different. For instance, igloos are built above ground and used to keep inside warm in the extreme cold northern regions, whereas Dome-Fridge is buried in the soil to have a cool atmosphere with low temperature inside it for storage of vaccines. Dome-shaped was chosen for the design because it exhibits few characteristics that are more advantageous for this project compared to the rectangular-shaped.
Before this invention, drivers had to manually load and unload ice to maintain the temperature inside their trucks. However, Jones's new system eliminated the need for manual loading ("Frederick McKinley Jones" Biography.com). According to the National Inventors Hall of Fame, his automatic refrigeration system maintained a consistent temperature inside the truck, ensuring the preservation of perishable goods ("Frederick McKinley Jones" National Inventors Hall of Fame). This invention not only improved the efficiency of the transportation but also reduced costs and increased the safety of the drivers. Jones's work in this field established him as a pioneer in refrigeration technology, leaving a big impact on the transportation
In the poem “Treblinka Gas Chamber”, by Phyllis Webb and in the TRC’s “The History”, both texts share a common theme of inhumane treatment towards children within certain cultural and ethnical groups. While the two authors explore distinct historical contexts, both texts are centred on racial segregation with nationalistic motives. Phyllis Webb appeals to a logos strategy through the use of allusion. In her poem, “Treblinka Gas Chamber”, Webb presents fictional and historical examples to display her knowledge and establish her credibility.
He uses his advocacy for air conditioning to gently approach the uncomfortable topic of our wrong-doings saying, “I’m hardly against air conditioning… it can save the lives of sick, elderly, and frail… [it] can enhance productivity and make factories safer for workers.” Gaining trust from the audience he continues to tackle the issue by suggesting that instead of complying with our expectation of having our thermostats set to “Igloo, arctic and frigid” we should use our air conditioning responsibly, such as reducing indoor temperatures to the mid-70s and no farther. However he is not convinced our culture would ever readily agree to limitations of this nature, therefore, Klinenberg suggests that there be new rules and regulations instituted concerning the use of air
the refrigerant is in a high-pressure, gas state. With the help of the A/C fan, the refrigerant cools as it moves through the condenser. During this process, the condenser pressurizes the gas and turns it into a liquid before it reaches the evaporator. Chevrolet C1500 Evaporator: When the refrigerant is in its liquid form, it expands.
It may take a few years for CFCs to escape the troposphere and enter the stratosphere, and then even longer to develop into harmful forms, but they have long lifetimes. Under
Introduction Chevron Phillips Chemical Company is the major producer of Cyclohexane. This successful company hoses the three largest cyclohexane plants in the world. Many are puzzled by how the production of cyclohexane seems to have become stagnant. Perhaps this is due to the cost of benzene increasing or the demand increasing. Through thorough investigation, the answer to this question and many more can be answered.
Arguably the most significant thing humans have done to cause climate change is the drastic increase in CO2. As a result of human activities, carbon dioxide, methane, nitrous oxide, and the halocarbons (a group of gases containing fluorine, chlorine, and bromine) build up in the atmosphere over time, as well as the natural sources of CO2, like vegetation. The concentration ofCO2 has went from 280 to more than 380 parts per million in just two hundred years. Still currently rising, the burning of fossil fuels by humans will continue to cause global warming and climate
As mentioned by Casper (2007), ‘Cold Chain Logistics deals with the production, processing, packaging station, cold storage warehouses, transportation, distribution centres, retailer, end consumer and in the user household refrigerators of products from the manufacture to the customer that are temperature sensitive.’ In this thesis, we are mainly concerned