Simulation Of Two-phase Flow In Flash Tank Of Semi-high Temperature Heat Pumps

Refrigerant injection has proven ti be effective in improving the performance of heat pump and air conditioner, this technique could be applied to semi-high heat pump design. Two typical refrigerant injection cycles can be found in the literature. It has concluded that the heating capacity and COP of the flash tank cycle are 105% and 4.3% higher than those of the internal heat exchanger cycle, respectively. Flash tank is the key part of the flash tank cycle and ensuing the reliable cycle operation. A simulation was carried to analyze the flash process in the flash tank with a software.Three initial inlet parameters which were inlet velocity, the inlet pressure, the inlet liquid volume fraction and one structural parameter which is inlet angle were selected in the simulation study respectively. Moreover, the change ratio of inlet and outlet volume fraction of liquid was selected as a measure of flash tank performance.A thermodynamic mode of flash evaporation was developed. A refrigerant named R134 a was chosen as the working fluid. The parameters were setted. An analysis of the distribution of pressure and liquid-vapor in the flash tank with a 0° inlet angle was carried to find the distribution law respectively, concluded with a the change ratio of inlet and outlet volume fraction of liquid no more than 4.825%.The influence of three inlet initial variables and one structure parameter on the distribution of pressure and liquid-vapor were investigated, and the influence of three inlet initial variables on the performance of the flash tank were summed up. The change ratio of inlet and outlet volume fraction of liquid was found to increase with an increase of the inlet pressure and a decrease of the inlet velocity, the impact of the inlet liquid volume fraction could be ignored.In this paper, the impact of the structure parameter named inlet angle on the performance of flash tank was detailed analyzed combined with different inlet velocity and inlet pressure. The change ratio of inlet and outlet volume fraction of liquid was found to increase with an increase of the inlet angle. The change ratio was found no more than 4.825% in the range of variables in this paper. Furthermore, the influence of the inlet angle was found weakened with a increase of the inlet pressure and a decrease of the inlet velocity.The research of flash tank in this paper could be useful for the flash tank design.