Abstract
The condensate on the surface of the minichannel heat exchanger generated during air cooling substantially reduces the heat transfer performance as it works as an evaporator in the air-conditioning system. This has received much attention in scientific communities. In this paper, the effect of operating parameters on the heat transfer performance of a minichannel heat exchanger (MHE) is investigated under an evaporator working condition. An experimental MHE test system is developed for this purpose, and extensive experimental studies are conducted under a wide range of working conditions using the water-cooling method. The inlet air temperature shows a large effect on the overall heat transfer coefficient, while the inlet air relative humidity shows a large effect on the condensate aggregation rate. The airside heat transfer coefficient increases from 66 to 81 W/(m2·K) when the inlet air temperature increases from 30 to 35 °C. While the condensate aggregation rate on the MHE surface increases by up to 1.8 times when the relative humidity increases from 50% to 70%. The optimal air velocity, 2.5 m/s, is identified in terms of the heat transfer rate and airside heat transfer coefficient of the MHE. It is also found that the heat transfer rate and overall heat transfer coefficient increase as the air velocity increases from 1.5 to 2.5 m/s and decreases above 2.5 m/s. Furthermore, a large amount of condensate accumulates on the MHE surface lowering the MHE heat transfer. The inclined installation angle of the MHE in the wind tunnel effectively enhances heat transfer performance on the MHE surface. The experimental results provide useful information for reducing condensate accumulation and enhancing microchannel heat transfer.
Highlights
The minichannel heat exchanger (MHE) is used as a novel condenser due to its advantages, such as high efficiency, compact structure, and low material cost [1,2]
Test system was developed to investigate the ofinfluence of inlet air air velocity, and inclined installation angle of on the surface condensate aggregation/removal and temperature, air velocity, and inclined installation angle of MHE on the surface condensate heat transfer performance of the used as evaporators
Some specific conclusions were drawn aggregation/removal and heat transfer performance of the MHE used as evaporators
Summary
The minichannel heat exchanger (MHE) is used as a novel condenser due to its advantages, such as high efficiency, compact structure, and low material cost [1,2]. It can be widely applied in automotive air conditioning [3,4] and thermoelectrics [5,6]. MHEs have attracted more and more attention in the context of building air-conditioning and associated heat exchange elements. The MHE concept was first proposed by Tuckerman and Pease [7] in the 1980s and, subsequently, widely used in large-scale integrated circuits. Li Hui et al [10] utilized an MHE as a condenser in Energies 2020, 13, 1065; doi:10.3390/en13051065 www.mdpi.com/journal/energies
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