Design Of Flow Path And Development Of Distributor In Small Diameter Tubes Heat Exchanger For Air Conditioner

An important development direction of future room air conditioners is to decrease the diameter of copper tubes,since room air conditioners with smaller diameter copper tubes can make heat exchangers more compact,efficient and environmentally friendly.To overcome the problem of the refrigerant mal-distribution of multi-path evaporators in air conditioners,a distributor in good geometry is in great need.The design idea of flow path and distributor of room air conditioner using small diameter heat exchanger is proposed.The design of flow path of heat exchanger for room air conditioner includes 2 steps.Firstly,the heat transfer and pressure drop of enhanced tubes and smooth tubes are calculated to determine the tube type;and then the algorithm of flow path parameters and the tube diameter is established based on heat transfer performance and pressure drop to optimize the flow path and the tube diameter.The design results indicate that,when 5 mm enhanced tubes are replaced with 3 mm smooth tubes in the heat exchangers of a typical room air conditioner,in cooling condition the heat transfer performance of the indoor unit and the outdoor unit increase by 12.7% and 5.7% respectively,and in heating condition the UA of the indoor unit and the outdoor unit increase by 10.1% and 15.4% respectively.The pressure drops of the indoor unit and the outdoor unit in cooling and heating conditions are all within 50 kPa.The mass of copper decreases by 57.2% and the mass of aluminum increases by 2.1%.In the part of developing distributor,a distributor which is capable to distribute two-phase refrigerant evenly into all the paths of evaporators is proposed.The basic idea to design the distributor is to form an annular flow before distribution and then allocate the annular flow uniformly.The detailed development method of the new distributor includes a calculation model for the inlet tube geometries of the distributor to form an annular flow and a new type connection structure between the inlet tube and the outlet tubes to allocate the annular flow.The proposed uniform distributor is manufactured and then tested by a vis UAlized experiment.The experimental results show that the distribution unevenness of the novel distributor at the horizontal,sloped and vertical installation are 18%?18% and 35% lower than those of the conventional cone-type distributor respectively,which means a much better performance of the proposed distributor.