Performance comparison of microchannel evaporators with refrigerant R-22

Abstract

An experimental study on the performance comparison of microchannel evaporators with refrigerant R-22 was conducted. Six microchannel evaporators were designed and manufactured for a residential air-conditioner. They were tested with psychrometric calorimeter test facilities. The experiment was performed with both vapor compression system and refrigerant circulation system. Each evaporator was made up of two parallel now heat exchangers connected with several return pipes. The parallel flow heat exchanger had 41 microchannel tubes inserted between inlet and outlet headers. The microchannel tube had 8 rectangular ports with the hydraulic diameter of 1.3 mm. For the vapor compression system, the flow area ratio and the number of return pipes had a great effect on the cooling capacity. Type 3 with a flow area ratio of73% and 58% showed the best cooling capacity. It had 12 return pipes and 3 circuits. There is a merging manifold in it. The effect of the number of circuits and merging manifold on the cooling capacity was relatively small. For the refrigerant circulation system, the effect of the mass now rate on the cooling capacity was slightly superior to that of inlet quality. The effect of the number of circuits on the cooling capacity was different from the result of the vapor compression system. The effect of merging manifold was negligible, which was consistent with the result of the vapor compression system. The cooling capacity proportionally increased as the vertical inclination angle of the evaporator increased due to gravity force.

Drop-in Test of Microchannel Evaporators Using R-22 for Residential Air Conditioners

“…Actually, this concept of the flow area ratio has been already applied to the microchannel condenser used in the automobile air conditioner and is protected by patent [19]. The concept of the flow area ratio for the residential air conditioner as an evaporator has been used in the work done by Cho and Cho [15] and is in the process of patent [20]. Prototypes 1 and 3 had the same geometry except for the location and number of return pipes.…”

“…They reported that the highest EER and cooling capacity was achieved with the system that used the microchannel heat exchangers with 20 FPI and a 15 • windward inclination of the heat exchanger. Cho and Cho [14,15] investigated the two-phase flow distribution and pressure drop in microchannel tubes under non-heating and heating conditions using the refrigerant of R-22, and they represented the effects of some static and dynamic parameters on the cooling capacity by evaluating several prototype microchannel evaporators. Kim et al [16] investigated the effect of inclination on the air-side performance of a brazed aluminum heat exchanger under dry and wet conditions.…”

Air-side performance of a micro-channel heat exchanger in wet surface conditions

“…Because of their specific structure, compactness, light weight, minimal refrigerant usage, and higher heat transfer performance compared to conventional fin-and-tube heat exchangers, micro-channel heat exchangers are a potential alternative for air-conditioning in the future. Many investigations have studied the effects of fin geometries on the air-side performance of louvered fin-and-flat tube heat exchangers under dry and wet surface conditions [1][2][3][4][5][6]. McLaughlin and Webb [1] investigated the effects of louver pitch and fin pitch under wet surface conditions.…”

“…They found that the cooling capacity for a corrugated louvered fin evaporator was better than that of the flat louvered fin evaporator. Cho and Cho [6] experimentally studied the effect of refrigerant mass flow rate, inlet vapor quality and the inclination angle of the test section on the cooling capacity. They found that the cooling capacity increased with increasing refrigerant mass flow rate and inclination angle (from vertical).…”

“…Despite its importance in the refrigerating applications, no attention was paid to the air-side performance of a micro-channel heat exchanger working with refrigerants. Up to now, there have been only three works, carried out by [5,6,11], dealing with the refrigerants. However, the experimental apparatus used in these three studies could not provide a wide range of the experimental conditions for both air side and tube side.…”