Thermodynamic, economic and environmental performance of a flute-type distributor embedded micro-channel evaporator for RACs

Room air conditioners embedded with micro-channel heat exchangers generally manifest excellent thermal performance. However, the non-uniform refrigerant distribution in micro-channels remains as a bottleneck problem. To address this problem, a micro-channel evaporator with a built-in flute-type distributor was designed and fabricated based on a finned-tube evaporator. This paper studies the influence of the structure of the built-in flute-type distributor on the gas–liquid two-phase refrigerant flow in the micro-channel flat tubes. The effects of the primary throttling depth, the placement angle between the opening of inlet header and the inlet of micro-channel flat tube, and the indoor dry-bulb temperature were studied using the enthalpy difference method. The cooling capacity, power input and energy efficiency ratio of the testing unit were compared regarding each influencing factor, and the optimal primary throttling depth was obtained. The thermodynamic performance of various room air conditioner evaporators with and without micro-channels and flute-type distributors were also compared. In addition, an economic and environmental analysis was conducted on the optimal configuration. The results showed that, the evaporator achieved a higher inlet pressure, lower pressure loss, and higher cooling capacity and energy efficiency ratio when the placement angle was 180°±6°. Compared to micro-channel evaporator embedded room air conditioner with no distributor, the energy efficiency ratio of room air conditioner with flute-type distributor embedded micro-channel evaporator with a 180° placement angle was improved by 11.8%. When the angle was within β = 180°±6°, the change of refrigeration capacity was not obvious. It was also showed that the annual power consumption, life cycle cost and total equivalent warming impact of the flute-type distributor embedded micro-channel evaporator was reduced by 13.6%, 12.0% and 12.9% respectively.