The effects of the airflows with the same flow rate and different air front velocity distributions on the performance of a two-row finned tube evaporator with two circuits were numerically studied by the software EVAP-COND 2.1. The air velocity distribution was in four shapes
i.e.
rectangle
two triangles with respective upper and lower right angles
and isosceles triangle. The results show that the evaporator capacity increases with the increase in the uniformity of the air velocity distribution. The capacity for the isosceles triangle
two triangles with upper and lower right angles is 8.5%
34.3% and 35.3% less than that for the rectangle shape
respectively. The non-uniform distribution of the air velocity causes different airflow rates of the two circuits
leading to the reduction of the overall heat transfer coefficient and then the decrease in the evaporator capacity. The different airflow rates of the two circuits result in different refrigerant outlet states. The refrigerant flow rate and the evaporator capacity decrease with the increase in the difference in the refrigerant outlet states between the two circuits. Moreover
the reverse heat transfer occurs easily for the circuit with greater airflow rate because the air temperature is lower than the refrigerant temperature. In addition
when the air velocity distribution is non-uniform
the effect of the circuit number on the evaporator capacity is significant
and there is an optimum circuit number.
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references
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