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Abstract: Refrigerant and airflow maldistribution in fin-and-tube evaporators for residential air-conditioning was investigated with numerical modeling. Fin-and-tube heat exchangers usually have a pre-defined circuitry. However, the objective in this study was to perform a generic investigation of each individual maldistribution source in an independent manner. Therefore, the evaporator and the condenser were simplified to be straight tubes for the purposes of this study. The numerical model of the R410A system, its verification and an investigation of individual maldistribution sources are presented in this paper. The maldistribution sources of interest were: inlet liquid/vapor phase distribution, feeder tube bending and airflow distribution. The results show that maldistribution reduced the cooling capacity and the coefficient of performance of the system. In particular, different phase distribution and non-uniform airflow distribution reduced the performance significantly. Different feeder tube bendings only caused a minor decrease in performance. [Copyright &y& Elsevier]

• Flow distribution in an evaporator with 52 circuits was studied experimentally. • Face split design with enlarging header size reduced header ΔP and maldistribution. • Choked flow design of extra capillary tubes avoided liquid sucked into compressor. • Improved system presented even refrigerant distribution with various mass flow rate. • Cooling capacity and COP of the improved system increased by 10.5% and 13.4%. In this paper, the design concept of the face split evaporator with a retrofitted suction header and choked flow in the capillary tubes was adopted to improve a direct expansion air-conditioning system with a designed air flow rate of 20,000 m3/h. The novel design of the direct expansion air-conditioning system was experimentally tested and validated. Face split evaporator reduced the refrigerant pressure drop in the suction header and the choked flow design limited the maximum flow rate across each branch circuit, which both contributed to the uniform refrigerant flow distribution of the improved system. Consequently, the cooling capacity and COP of the improved system was 10.5% and 13.4% higher than the original system. With the refrigerant mass flow rate of the improved system varying from 1.33 kg/s to 2.05 kg/s, the measured cooling capacity ranged 240–350 kW and the ratio of the system COP to the ideal COP of the reversed Carnot cycle with the same evaporating and condensing temperatures maintained at 0.72–0.74. The experimental results demonstrated that the improved system performed a relatively uniform refrigerant flow distribution among the branch circuit of the evaporator regardless of the refrigerant mass flow rate. This study is beneficial to the optimization design of the multi-circuit evaporator for a direct expansion air-conditioning system with a large air flow rate in engineering applications. [ABSTRACT FROM AUTHOR]