TY - GEN
T1 - Distribution function for reversible microchannel heat exchanger with vertical headers - Considering the effects of inlet conditions, geometries and fluid properties
AU - Zou, Yang
AU - Hrnjak, Predrag Stojan
PY - 2015
Y1 - 2015
N2 - Refrigerant maldistribution deteriorates microchannel evaporator performance because it creates unwanted superheated region. The objective of this study is to explore what affects distribution in the vertical header and how to model distribution. Two-phase R245fa, R134a, R410A or R32 is circulated into the transparent vertical header through multi-parallel microchannel tubes in the bottom pass and exits through multi-parallel microchannel tubes in the top pass representing the flow in the heat pump mode of a reversible microchannel heat exchanger. Based on the visualization, the best distribution is when the momentum in the upper region is high enough to lift liquid to the top, while the momentum in the lower region is not too high to create semi-annular flow. An empirical function is derived to model refrigerant distribution by relating liquid takeoff ratio with inlet quality, vapour phase Reynolds number and Froude number in the header immediately upstream of the microchannel tube.
AB - Refrigerant maldistribution deteriorates microchannel evaporator performance because it creates unwanted superheated region. The objective of this study is to explore what affects distribution in the vertical header and how to model distribution. Two-phase R245fa, R134a, R410A or R32 is circulated into the transparent vertical header through multi-parallel microchannel tubes in the bottom pass and exits through multi-parallel microchannel tubes in the top pass representing the flow in the heat pump mode of a reversible microchannel heat exchanger. Based on the visualization, the best distribution is when the momentum in the upper region is high enough to lift liquid to the top, while the momentum in the lower region is not too high to create semi-annular flow. An empirical function is derived to model refrigerant distribution by relating liquid takeoff ratio with inlet quality, vapour phase Reynolds number and Froude number in the header immediately upstream of the microchannel tube.
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U2 - 10.18462/iir.icr.2015.0006
DO - 10.18462/iir.icr.2015.0006
M3 - Conference contribution
AN - SCOPUS:85016749058
T3 - Refrigeration Science and Technology
SP - 1748
EP - 1755
BT - 24th IIR International Congress of Refrigeration, ICR 2015
PB - International Institute of Refrigeration
T2 - 24th IIR International Congress of Refrigeration, ICR 2015
Y2 - 16 August 2015 through 22 August 2015
ER -