Study of thermoelectric subcooling on small-scale CO2 transcritical systems for performance improvement with and without ejector and heat recovery

Abstract

In this study, performance of TEC and TEC-TEG modules for providing subcooling in multi evaporator CO2 booster systems with and without ejector operating at high ambient is explored. Effect on heat recovery potential is also determined. The degree of subcooling explored is from 1K to 5K with TEC. Subcooling decreases heat rejection pressure, which improves cooling COP. For the conventional system, the cooling COP of baseline is 1.57 at 45 °C ambient, which improves to a maximum of 1.68 a 7% increment when 5K subcooling with externally powered TEC is implemented. Further, power required for 1K subcooling can be generated using TEG, leading to an increment in COP to 1.623, a 3.2% improvement. For the ejector system the baseline has a cooling COP of 1.9, which improves to 2 with 5K subcooling when TEC is used. In this case also TEG is able to supply the power of 1K subcooling to TEC that results in performance improvement around 3.2%.