非共沸混合媒体用EHD熱交換器の研究

抄録

To realize higher performance heat pump systems utilizing nonazeotropic mixtures, the EHD (Electrohydrodynamic) evaporator and condenser have been experimentally studied. Conventionally manufactured surfaces have not been effective for the evaporation and the condensation of nonazeotropic mixtures because of the accumulation of less evaporative or less condensable components of the mixture near the heat transfer surface. By setting the perforated coaxial cylindrical electrode inside of the 3.75-m-long evaporator tube, the evaporation and boiling heat transfer of the nonazeotropic mixture of HCFC 123 and HFC 134a on the inner surface of the tube have been enhanced by the factor of about 3 times over a wide range of qualities with the application of 7 kV at the electrode distance of 2.5 mm. Furthermore, using the electrically conducting transparent glass, it was clarified that the flow pattern has been changed and that some EHD phenomena such as the EHD surface instability have been observed. As for the condenser, the necessary tube length for condensation outside of the vertical tube has been shortened by two kinds of EHD effects, the increase of the condensation surface and the realization of the thinner film of the condensate.