An experimental study and infrared thermography analysis on the effect of using various flute-type distributors in mini-channel evaporators employed by room air conditioners

In air conditioners, mini-channel heat evaporator/heat exchanger excels in performance over the traditional fin-tube counterpart. However, the uniformity of two-phase refrigerant flow distribution in mini-channel evaporators remains unclear. To enhance the flow distribution in mini-channels, a flute-type coaxial multi-opening distributor is inserted into the header of a vertical mini-channel evaporator. Using a room air conditioner (RAC) unit (cooling capacity at 7.5 kW and R410A as the refrigerant) as a sample, the opening direction and inter-opening distance along the distributor are changed to obtain the variation range where the two-phase flow distribution uniformity in the mini-channel evaporator performs the best. Considering the secondary throttle effect caused by the inserted flute-type distributor, the proper width of the preceding throttle opening is proposed based on the performance of the sample unit under the nominal condition of refrigeration. The thermal cycle pressure enthalpy diagrams of the sample unit and the infrared thermography of the mini-channel evaporator are used to verify the effect of the proposed flute-type distributor forms. The results reveal that, the most uniform refrigerant two-phase flow within the mini-channel is achieved when using a non-uniform distributor and β = 180°. It was also indicated that the CC and EER of the RAC unit are significantly increased by 2.62–6.43% and 4.04–11.39%. Additionally, the annual electricity consumption and total equivalent warming impact of the slotted distributor embedded in the microchannel evaporator were reduced by 0.40 MWh and 6.9%, respectively. Graphical abstract: [Figure not available: see fulltext.]