 |
Pega Hrnjak, Ph.D., University of Illinois, ACRC and CTS |
Over last twenty years microchannel heat exchangers (MHX) have dramatically increased their presence in energy conversion systems: from aircraft and automotive applications and expanding to residential and industrial refrigeration and air-conditioning. This presentation presents major issues impacting application of MHX as evaporators: 1) condensate retention/removal, 2) frosting/defrosting and 3) refrigerant distribution. The physics of the issues are discussed along with directions for mitigating them. Particular attention is given to refrigerant distribution and potential of Flash Gas Bypass to improve it. In addition, quantification of vapor flow reversal in MHX tubes is presented along with system improvements obtained by its removal.