| The multi-branch design of the evaporator can improve its heat transfer efficiency,but the uneven distribution of refrigerant in each branch will reduce the heat transfer efficiency of the evaporator,so it is necessary to set a distributor in front of the evaporator to distribute the two-phase refrigerant evenly.Both the structural parameters and the inlet conditions of the distributor will affect its distribution efficiency,therefore,it is of great significance to study the influence of the related structural factors and non-structural factors on the distribution of the distributor.Based on Venturi distributor,the feasibility of prediction of two-phase flow distribution by simulation is verified by comparing with existing experiments firstly in this paper,and then further studied the influence of four factors on the distribution efficiency of the Venturi distributor through simulation,as well as the circulation characteristics and the distribution characteristics in the Venturi distributor of five refrigerants under the same working conditions.Firstly,by simulating the existing two-phase flow distribution experiments,the variation of the distribution trend of the simulation and the experiment is compared when the working conditions change,it is verified that the standard k-ε model and the Eulerian two-phase flow model can predict the two-phase flow distribution under different working conditions,and the unevenness is proposed to measure the distribution efficiency of the Venturi distributor.Secondly,the influence of the angle between the outlet pipe and the center line and the profile of the contraction section on the distribution efficiency of Venturi distributor is studied by simulation,meanwhile,the two factors are are brought together to optimize the structure of the distributor.Results show that the optimal angle between outlet pipe and center line of the Venturi distributor is 60°,and the optimal profile of the contraction section is straight line,moreover,the distribution efficiency can be improved to the greatest extent when the two structural factors both take the optimal value.Then,the influences of inlet quality and inlet mass flow rate on the distribution efficiency were studied qualitatively and quantitatively,and circulation characteristics and distribution characteristics of five refrigerants in the distributor under the same working condition were also studied.Results show that the distribution efficiency of Venturi distributor will increase with the decrease of inlet quality and the increase of mass flow rate,under the working condition of this paper,the unevenness decreases by15.78% when the inlet quality decreases by 0.05,and the unevenness decreases by54.87% when the mass flow rate increases by 0.5 times,R1234ze(E)has the best circulation and distribution characteristics among all refrigerants.Finally,the influence of four factors on the gas-liquid two-phase distribution in the Venturi distributor was observed and the relationship between the pressure drop on the center line of the contraction section and unevenness was studied.Results show that factors other than mass flow rate will affect the distribution of two-phase refrigerant in the distributor,in addition,when the pressure drop on the center line of the contraction section is greatly different,the greater the pressure drop is,the more uniform the distribution will be.However,when the pressure drop in the contraction section is similar,the final distribution situation cannot be directly determined by the size of the pressure drop. |
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