Table 3 - uploaded by Bernard Thonon
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Source publication
Refrigeration and heat pumping effects can be produced via various processes. In this
document, we will focus on the use of the vapor compression cycle, which has been the
workhorse of the refrigeration industry for well over a century.
The use of carbon dioxide is presented; design and practical issues.
Context in source publication
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This paper proposes a quick method to investigate coefficient of performance (COP) of vapor compression heat pump from a dimensionless term, Figure of Merit (FOM), which covers refrigerant properties and operating temperatures as FOM=Ja0.1.Tc−TevTc. Twelve pure refrigerants including low global warming and natural refrigerants were studied. It coul...
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Vapor compression refrigeration cycle (VCRC) is widely used in refrigeration and air conditioning (R&A) systems. Sub-cooling is used to improve the coefficient of performance (COP) of the R&A system by enhancing the cooling capacity. This paper presents various sub-cooling methods, which have been established and applied to enhance the performance...
Two-phase ejectors play a major role as refrigerant expansion devices in vapor compression systems and can find potential applications in many other industrial processes. As a result, they have become a focus of attention for the last few decades from the scientific community, not only for the expansion work recovery in a wide range of refrigeratio...
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Citations
... Their use in refrigeration was encouraged because they were stable, efficient and safe. Gradually, they caused the decline of the use of natural fluids in refrigeration except NH 3 which was (and still is) the most popular refrigerant in large food processing plants (Bensafi andThonon, 2007, Calm, 2008). catalytically with ozone molecules thereby destroying them. ...
... If GHGs are concentrated in the atmosphere, they absorb this reflected heat and thus retain the heat on earth, which results in rise of surface temperature. Therefore there has been a general call on the reduction of these GHGs (Calm andDidion, 1998, Bensafi andThonon, 2007). Global warming potential (GWP) of a gas is its capacity to absorb heat as compared to an equal mass of CO 2 over a certain period of time when it is still in the atmosphere. ...
... The most common are air, water, NH 3 , hydrocarbons (HC) and Carbon dioxide (CO 2 or R744), also known as the gentle five. Natural refrigerants have negligibly small ODP and GWP (Bensafi and Thonon, 2007). ...
The influence of variables such as; refrigerant amount, chilling and cooling water temperature, throttle valve opening, cooling and chilling water flow rates, on the efficiency (coefficient of performance - COP) of a water to water carbon dioxide heat pump was investigated. Design of experiments was done using design-expert® 6 software for regression analysis. A response surface method known as central cubic design was used to provide optimum results with minimum experiments. Through multiple regression analysis, an empirical equation relating the COP to the variables was derived. Analysis of variance revealed that these regressions are statistically significant at 95% confidence level compounded with a very low standard deviation and a high adequate precision. The close relationship between the predicted COP values and the actual values further proves the worthiness of the empirical equation. It was observed that cooling water temperature had the highest influence followed by the chilling water temperature. Surprisingly, the amount of the refrigerant was third followed by the throttle valve opening. Understandably, chilling water flow rate had the least effect on the COP. Through response surface diagrams, the interactive influence of the variables were also observed. The COP values arrived at varied from 1.545 to 6.914 although if the variables were optimized fully within the scope of this study, a value of up to 11.8 could be achieved. Still, if the variables range is increased further, higher COP could be achieved. Finally, a discussion was done in a bid to explain these results. © 2015 Journal of Thermal Engineering Yildiz Technical University Press, Istanbul, Turkey.
... Source: Danfoss (2008) In general terms, it is concluded that CO 2 applications in the cold generation are many. Among these applications CO 2 is found in frigorific facilities as secondary fluid, in automotive air conditioning, vending machines and supermarkets (Bensafi and Thonon, 2007). ...
Carbon dioxide is an innocuous refrigerant for the environment. It is a substance of current interest in the refrigeration area. Its good thermodynamic and heat transfer properties have placed it in an excellent position for substituting refrigerants that contribute to global warming. This paper describes carbon dioxide as a refrigerant, the main characteristics that have made it a substance of current interest, its applications in subcritical and transcritical cycles, and a general vision of its usage at international level. Moreover, this paper presents the disadvantages of using this refrigerant and the upgrades made by the scientific community in order to improve the performance of those systems that work with this fluid. This paper is a reference for those interested in having a wider vision of frigorific technology based on carbon dioxide as a refrigerant.
