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10 1 Introduction 0 100 200 300 400 Enthalpy (KJ/Kg) 500 600 310K 7 0.7 ΔPrejection Δw Δqheating The variation of heating capacity and compressor work with the identical high-side pressure increment illustrated in the P-h diagram of transcritical carbon dioxide heat pump cycle. ● In transcritical CO2 cycle, the effect of evaporation temperature on heating capacity and COP is smaller than that of other conventional subcritical cycles which indicates the transcritical CO2 heat pump can supply heat more stably in con- ditions with varying heat source temperatures (for instance, air source transcritical CO2 heat pumps can perform better with varying ambient temperatures over a year). Therefore, when compared with conventional heat pumps by considering supplementary heat, the transcritical CO2 heat pump may have higher overall heating COP (i.e. the ratio of heat pump heating load plus supplementary heating load to the power input) due to the smaller requirement on supplementary heating devices [6]. 1.2.3 Modifications of Transcritical CO2 Cycles Based on the basic CO2 cycle, several modifications to cycles can be obtained by modifying the existing components, adding other devices or designing new circulations in order to get better performance. Heat exchangers like gas coolers and evaporators can be modified by using different types of heat exchange channels, like the fin and tube type, the shell and tube type and the microchannel type, leading to different results. For instance, microchannel tubes can increase the heat transfer area, thus reducing the heat exchanger size, and also can improve heat transfer performance. Calculations showed that the capacity of a microchannel evaporator was 33% higher than that of the conventional fin-and-tube type [28]. Besides the choice of type, the heat exchanger parameter (e.g. tube diameter, tube pitch, fin spacing), channel arrangement (e.g. cross-flow, counter-flow), orientation (e.g. vertical flow, horizontal flow) and wall material (e.g. stainless steel, copper, aluminum) also have a unique impact on heat transfer and cycle performance, which should be modified comprehensively. Adding a suction line heat exchanger (SLHX) is a common method of preheating the vapor before compression and subcools the cooled fluid at the outlet of the gas cooler. This Figure 1.5 Pressure (MPa)PDF Image | What is a heat pump
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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
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