PDF Publication Title:
Text from PDF Page: 024
cooling capacity. Because of the above-mentioned low critical temperature, R744 can be run in a trans- critical cycle. This means that the working medium would evaporate in the subcritical region and successively reject heat in a gas cooler instead of a condenser, at temperatures above the critical point (Bathkar, 2013). 2.3.3. HCs An advantage with this type of refrigerants is their miscibility with synthetic lubricants and mineral oil. These fluids therefore do not have to be changed when switching from HCFC or HFC mixtures to HC ones. Besides, their short atmospheric life results in a very low GWP and they represent the best choice when considering their cost. On the other hand, they present problems because of their flammability. The two main HCs used as refrigerants are isobutane (refrigerators) and propane (small commercial appliances and residential heat pumps). Many examples of blends involving HCs, with different components and variable relative percentages in mass, exist in the literature. The general conclusion seems to be a lower energy consumption, compared to both equivalent R134a and R22 systems. In conclusion, HC mixtures are a good alternative in small applications such as domestic refrigeration, small capacity refrigeration and heat pump units and MAC systems (Mohanraj, 2011) (Bathkar, 2013). R290 (propane) It has environmental and thermodynamic outstanding characteristics but, as HC, has high flammability and thus cannot be implemented in existing FC systems. Moreover, because of the safety issues it is only applicable in industrial/commercial refrigeration systems and air conditioning, as well as domestic air conditioning, provided proper refitting. Restrictions to the placement of the system and to the refrigerant charge are imposed by the Standard EN378 (EN 378, 2008). Despite the flammability concerns, research is active and products are being brought to the market from companies such as Ait- Deutschland (Maul, 2013). In order to lessen the flammability, mixtures can be used. Ki-Jung Park et al. (2009) investigated for example a mixture of R170/R290 (with varying relative composition) in a heat pump as a substitute for R22, both in summer and winter conditions. The results showed an increase in the COP of up to 15.4%, despite a decrease in the capacity (up to -7.5%). Other observed improvements of the system are the decrease in the compressor discharge temperature and a reduction in the refrigerant charge. Fan et al. (2013) investigated a R744/R290 mixture, finding an increased COP, along with an increased volumetric heating capacity when compared to an equivalent R22 system. Though, it is observed that the performance is efficient only when working with large heat-sink temperature rise. R1270 (propylene) Literature is very limited, and major studies still need to be performed. The environmental characteristics are optimal, but propylene, as propane, implies an A3 flammability level and thus is not suitable for retrofitting existing systems. It is most adapt to low – medium temperature applications. (Linde , 2015). Propylene is an unsaturated molecule and therefore its stability is lower than that of propane. Therefore the latter is often given priority to the former when selecting an environmentally friendly refrigerant. -15-PDF Image | Next generation of refrigerants for residential heat pump systems
PDF Search Title:
Next generation of refrigerants for residential heat pump systemsOriginal File Name Searched:
MartinaLonghini_ThesisReport.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)