Minichannel, Evaporator, Condenser
The use of aluminum heat exchangers for refrigeration and air-conditioning equipment is very interesting since it allows to reduce weight and manufacturing costs while maintaining high performance. In this paper a two-phase heat transfer characterization of an innovative aluminum minichannel heat exchanger is presented. The heat exchanger (HX) is composed by rectangular channels with internal perforated turbolators. A special test section has been projected and realized in the Two Phase Heat Transfer Lab of the University of Padova in order to measure the heat transfer coefficient (HTC) on the refrigerant side during flow boiling and condensation. The test section has a single refrigerant channel with a perforated fin to make the minichannels. The test section is provided with 14 water flow modules installed at top and bottom of the refrigerant channel to promote boiling or condensation of the refrigerant. Therefore, the test section is made of seven different zones: each of them is equipped with 8 thermocouples to measure the wall temperature during the refrigerant phase change. The heat flow rate in each zone is calculated by an energy balance on the water side. Pressure transducers and thermocouples on the refrigerant side allow to determine the saturation temperature and thus the heat transfer coefficient of the refrigerant. The operating refrigerant used during tests is R410A. The particular scheme adopted for the test section enables to measure HTC at varying vapor quality and heat flow rate. Vaporization and condensation tests were carried out with different saturation temperatures, specific heat flow rate (from 40 to 150 kW/m2) and refrigerant mass flux (50÷150 kg/(m2 s) ). Data acquired have been compared with vaporization and condensation predictions from various correlations available in literature. This part of the work is very interesting since no data is available in the literature for such a geometry in vaporization nor in condensation. Therefore, the present paper will investigate the potential performance of these innovative minichannel heat exchangers as condensers and evaporators in air-conditioning equipment.