TY - JOUR
T1 - Effect of periodic reverse flow on the heat transfer performance of microchannel evaporators
AU - Li, Huize
AU - Hrnjak, Pega
N1 - Publisher Copyright:
© 2017 Elsevier Ltd and IIR
PY - 2017/12
Y1 - 2017/12
N2 - Periodic flow reversal are commonly present in microchannel heat exchangers, but have been studied in air conditioning systems only recently. This paper presents the effect of periodic reverse flow on the heat transfer performance of a heat exchanger. Two heat exchangers with identical geometries in the heat transfer areas are employed and an artificial upstream flow resistance is added for one of them. The heat exchanger without artificial flow resistance is subject to more severe boiling instabilities and consequently generates four times more reverse vapor flow than the other one. The comparison of capacities under identical operating conditions reveals that higher intensity of reverse flow helps to improve cooling capacity by up to 13.3%. Meanwhile, numerical simulations of bubble dynamics coupled with heat transfer are carried out for both heat exchangers. Results show that in the heat exchanger with more reverse flow, the refrigerant side heat transfer coefficients are enhanced, especially in the upstream part of a channel where the flow velocity is relatively low.
AB - Periodic flow reversal are commonly present in microchannel heat exchangers, but have been studied in air conditioning systems only recently. This paper presents the effect of periodic reverse flow on the heat transfer performance of a heat exchanger. Two heat exchangers with identical geometries in the heat transfer areas are employed and an artificial upstream flow resistance is added for one of them. The heat exchanger without artificial flow resistance is subject to more severe boiling instabilities and consequently generates four times more reverse vapor flow than the other one. The comparison of capacities under identical operating conditions reveals that higher intensity of reverse flow helps to improve cooling capacity by up to 13.3%. Meanwhile, numerical simulations of bubble dynamics coupled with heat transfer are carried out for both heat exchangers. Results show that in the heat exchanger with more reverse flow, the refrigerant side heat transfer coefficients are enhanced, especially in the upstream part of a channel where the flow velocity is relatively low.
KW - Boiling instabilities
KW - Flow reversal
KW - Microchannel heat exchanger
KW - Model of bubble dynamics
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U2 - 10.1016/j.ijrefrig.2017.08.017
DO - 10.1016/j.ijrefrig.2017.08.017
M3 - Article
AN - SCOPUS:85031726045
SN - 0140-7007
VL - 84
SP - 309
EP - 320
JO - International Journal of Refrigeration
JF - International Journal of Refrigeration
ER -