A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid a...A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±800 of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes.展开更多
An analytic model for working fluids flowing through capillary tubes has been established with the approximate integral method. All the possible flow regimes in the capillary tubes,including subcooled, two-phase and s...An analytic model for working fluids flowing through capillary tubes has been established with the approximate integral method. All the possible flow regimes in the capillary tubes,including subcooled, two-phase and superheated regimes, are covered in the model, and different analytic solutions are given respectively for each flow regime. As examples, the mass flow rates of refrigerants R12, R134a and R600a through capillary tubes are predicted by the model,and compared with those evaluated by a general distributed-parameter model. The mean bias falls into 1% and the maximum bias is 2.2%, while the computation speed of the new model is more than one order of magnitude higher than that of the distributed-parameter one.展开更多
It is necessary to establish a simple and accurate mathematical model of capillary tubesfor the study of the system performance of refrigeration appliances equipped with the capillary tube. In this work, a new general...It is necessary to establish a simple and accurate mathematical model of capillary tubesfor the study of the system performance of refrigeration appliances equipped with the capillary tube. In this work, a new general integral model of capillajry tubes has been presented. It covers subcooled, two--phase and superheated flow regions which may occur inthe capillary tube. In the different flow region, special approximate integral equation is developed. This model is used in prediction of mass flow rate of the refrigerants, R12, R134aand R600a flowing through the capillary tube. The results are compared with those of thedistribut ed-- p aramet er mo del. The average devtat ion is 1. 3 0 % and t he maximum deviationis +4.58/-6.39%. The computation speed of the recommended model is more than one orderof magnitude higher than that of the distributed-parameter one.展开更多
文摘A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±800 of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes.
文摘An analytic model for working fluids flowing through capillary tubes has been established with the approximate integral method. All the possible flow regimes in the capillary tubes,including subcooled, two-phase and superheated regimes, are covered in the model, and different analytic solutions are given respectively for each flow regime. As examples, the mass flow rates of refrigerants R12, R134a and R600a through capillary tubes are predicted by the model,and compared with those evaluated by a general distributed-parameter model. The mean bias falls into 1% and the maximum bias is 2.2%, while the computation speed of the new model is more than one order of magnitude higher than that of the distributed-parameter one.
文摘It is necessary to establish a simple and accurate mathematical model of capillary tubesfor the study of the system performance of refrigeration appliances equipped with the capillary tube. In this work, a new general integral model of capillajry tubes has been presented. It covers subcooled, two--phase and superheated flow regions which may occur inthe capillary tube. In the different flow region, special approximate integral equation is developed. This model is used in prediction of mass flow rate of the refrigerants, R12, R134aand R600a flowing through the capillary tube. The results are compared with those of thedistribut ed-- p aramet er mo del. The average devtat ion is 1. 3 0 % and t he maximum deviationis +4.58/-6.39%. The computation speed of the recommended model is more than one orderof magnitude higher than that of the distributed-parameter one.
