| The small-diameter air conditioner(the tube diameter isn't more than 5mm)has the advantages of improved heat transfer capability,decreased copper use and reduced refrigerant charge.In order to avoid the decrease of evaporation pressure and the reduction of system performance due to excessive pressure drop,the refrigerant side of small-diameter air conditioner consists of heat exchangers with multi-channel in parallel.This kind of heat exchanger needs distributors to guarantee even distribution in each flow path.Refrigerant quality,mass flow rate,installation angle and inlet flow pattern are keys to improve the distribution uniformity.Therefore,it's necessary to study distribution performance and structure optimization under these elements.Currently literatures are mainly about distribution performance of T-type,Y-type,branch-type,and distributors in large air conditioner,however rare research has been carried out for distribution performance and structure optimization of distributor in small-diameter air conditioner.In this paper,the impacts of inlet quality,mass flow rate,installation angle,inlet flow pattern,refrigerant type on three types of common distributors were studied by means of experimental and numerical simulation,the annual distribution performance of distributors was defined,the structural optimization methods were proposed and optimized examples based on proposed methods were verified by experiment in a room air conditioner.The main research contents are introduced as follows:1)A mass flow distribution rig was designed and built to test the distribution uniformity of jack-type,cone-type,reflective-type distributor in the use of heating and enthalpy-changing method.Different impact factors including inlet quality,mass flow rate,installation angle,inlet flow pattern were tested and analyzed based on experimental results.The comparison of three distributor types was conducted under different installation angles and mass flow rates.2)CFD models of jack-type,cone-type,reflective-type distributor were built by Fluent Software.After independent verification of mesh,grid number of each distributor was verified.In addition,two distributor models based were simulated and verified by experimental data,which were respectively based on Eulerian multiphase flow model and mixed multiphase flow model.The results show that: simulated model based on Eulerian multiphase flow model has a result closer to the experimental data,with a deviation less than 15%.3)The annual distribution performance of three kinds of distributors was evaluated.The annual performance factor of distributor in indoor unit and outdoor unit was defined,and the distributor type with best annual performance through CFD simulation was obtained.4)The distribution performance under four refrigerant types(R22,R410 A,R290,R32)was studied.The main factors concerning refrigerant types that affect the distribution were theoretically analyzed,and three kinds of distributors under different refrigerant type were simulated,finally the distributor type with a proper distribution performance under four refrigerant types were presented,as well as its structural optimized direction.5)Based on the evaluation result of annual distribution performance and distribution performance under four refrigerants,jack-type and cone-type were chosen to improve their distribution performance.Structural optimized methods of jack-type and cone-type were proposed,and optimized examples were verified by the application in a room air conditioner which proved to enhance the energy efficiency of room air conditioner by 2.2%~ 2.7%. |
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