TY - JOUR

T1 - Modelling distribution of evaporating CO2 in parallel minichannels

A1 - Brix,Wiebke

A1 - Kærn,Martin Ryhl

A1 - Elmegaard,Brian

AU - Brix,Wiebke

AU - Kærn,Martin Ryhl

AU - Elmegaard,Brian

PB - Elsevier Ltd.

PY - 2010

Y1 - 2010

N2 - The effects of airflow non-uniformity and uneven inlet qualities on the performance of a minichannel evaporator with parallel channels, using CO2 as refrigerant, are investigated numerically. For this purpose a one-dimensional discretised steady-state model was developed, applying well-known empirical correlations for calculating frictional pressure drop and heat transfer coefficients. An investigation of different correlations for boiling two-phase flow shows that the choice of correlation is insignificant regarding the overall results. It is shown that non-uniform airflow leads to maldistribution of the refrigerant and considerable capacity reduction of the evaporator. Uneven inlet ualities to the different channels show only minor effects on the refrigerant distribution and evaporator capacity as long as the channels are vertically oriented with CO2 flowing upwards. For horizontal channels capacity reductions are found for both non-uniform airflow and uneven inlet qualities. For horizontal minichannels the results are very similar to those obtained using R134a as refrigerant.

AB - The effects of airflow non-uniformity and uneven inlet qualities on the performance of a minichannel evaporator with parallel channels, using CO2 as refrigerant, are investigated numerically. For this purpose a one-dimensional discretised steady-state model was developed, applying well-known empirical correlations for calculating frictional pressure drop and heat transfer coefficients. An investigation of different correlations for boiling two-phase flow shows that the choice of correlation is insignificant regarding the overall results. It is shown that non-uniform airflow leads to maldistribution of the refrigerant and considerable capacity reduction of the evaporator. Uneven inlet ualities to the different channels show only minor effects on the refrigerant distribution and evaporator capacity as long as the channels are vertically oriented with CO2 flowing upwards. For horizontal channels capacity reductions are found for both non-uniform airflow and uneven inlet qualities. For horizontal minichannels the results are very similar to those obtained using R134a as refrigerant.

KW - Microchannel

KW - Heat exchanger

KW - Boiling

KW - Distribution

KW - Two-phase flow

KW - Simulation

KW - Carbon dioxide

KW - Modelling

U2 - 10.1016/j.ijrefrig.2010.04.012

DO - 10.1016/j.ijrefrig.2010.04.012

JO - International Journal of Refrigeration

JF - International Journal of Refrigeration

SN - 0140-7007

IS - 6

VL - 33

SP - 1086

EP - 1094

ER -