Wawzyniak, M., Walter, C., Kemle, A., and David, G., "High Efficiency Subcool Condenser," SAE Int. J. Passeng. Cars - Mech. Syst. 6(2):918-926, 2013, doi:10.4271/2013-01-1295.
Sustainable reduction of the CO2 emissions of future vehicles goes hand in hand with the increase in efficiency of ancillary units. Of particular importance is the reduction of fuel consumption attributed to the vehicle's air conditioning system. The innovative development of a condenser with a 3-pass subcooling zone renders it possible to significantly increase the efficiency of the cooling circuit. This is applicable both in the case of current and future refrigerants.The basis for increasing the efficiency of the condenser is rooted in the systematic analysis of the local heat transfer functions, pressure drops and implementation of an improved flow path configuration. The current condenser design, which includes the functionality of a receiver/dryer with a dedicated subcooling zone, is effective at providing stable liquid refrigerant to the TXV under a variety of conditions. By optimally adapting the flow cross-section to the density change of the refrigerant and increasing the subcooling function by means of a 3-pass flow subcooling zone, it is possible to achieve a significantly lower outlet temperature of the refrigerant. The locally higher pressure drop in the subcooling zone does not have a negative impact on the vapor compression circuit and can therefore be used to increase efficiency without the risk of losses.The theoretical derivation, as well as simulation and measurement results for the new condenser, are presented and discussed in comparison with conventional designs. A new condenser specification has been derived and validated for the system-oriented evaluation of the component. Finally, the validation results from the circuit and vehicle measurements in the wind tunnel are presented. The newly developed condenser resulted in a significant increase of 4% of evaporator performance while maintaining mass and package space. Alternatively, weight and conduction depth can be reduced by 25% while maintaining capacity and system efficiency.