Development Of Virtual Piston Model And Simulation Of Flow Characteristics Based On HVCHP

With the progress of society,environmental problems are gradually concerned.As an alternative product of coal-fired heating,Vuilleumier Heat Pump System has attracted more and more attention.In this paper,the Hofbauer-Vuilleumier Cycle Heat Pump(HVCHP)proposed by Hofbauer is studied.The specific work content are as follow:(1)In order to analyze low efficiency of Vuilleumier Heat Pump System,the efficiency of hypothetical engine and the cooler is analyzed by monitoring PV power flow and heat flow.However,in the current three chambers Vuilleumier model and four chambers Vuilleumier model,the efficiency of hypothetical engine and cooler obtained by the above two methods is not reasonable.Ther efore,a virtual piston model is proposed in this paper.In addition,the reason for the low efficiency of the whole system is analyzed,and it is found that the compression ratio of virtual engine is smaller than a stirling engine works independently.(2)The intermittent oscillating flow of working fluid in the heat exchanger of HVCHP was studied,a two-dimensional CFD model of straight tube heat exchanger is established.The difference of flow resistance loss and heat transfer between intermittent oscillating flow and continuous oscillating flow in heat exchanger are compared.And the effect of flow velocity variation on intermittent oscillating flow in heat exchanger is analyzed.It is found that there is a large difference between intermittent oscillating flow and continuous oscillating flow.The average pressure drop and heat transfer coefficient increase d by 33.3% and 14.6% respectively,and the increase of flow velocity leads to the decrease of friction coefficient and the increase of heat transfer coefficient.(3)The intermittent oscillating flow of working fluid in the regenerator of HVCHP was studied,a three-dimensional CFD model of stacked wire mesh regenerator is established,and the difference between intermittent oscillating flow and continuous oscillating flow in flow and heat transfer was compared,and the effects of hot end temperature,velocity and frequency on intermittent oscillating flow in regenerator are analyzed.It is found that the flow characteristics of intermittent oscillating flow and continuous oscillating flow are almost the same,and the difference only exists in the velocity conversion stage.Therefore,the empirical formula of continuous oscillating flow can be used in the study of intermittent oscillating flow.In the calculation range of this study,the effect on pressure drop of intermittent oscillating flow is in the order of velocity,hot end temperature and frequency,and the influence on heat transfer is in the order of velocity,frequency and hot end temperature.In this paper,a mathematical model is established to analyze the performance of engine and cooler in Vuilleumier Heat Pump,which provides references for the performance analysis of Vuilleumier Heat Pump;The intermittent oscillating flow of working fluid in the heat exchanger and regenerator of HVCHP is simulated by CFD,which has practical significance for the design and optimization of the system.