A Dynamic Analysis of Free Piston Vuilleumier Cycle Heat Pumps A Dynamic Analysis of Free Piston Vuilleumier Cycle Heat Pumps

A dynamic analysis of a free piston Vuilleumier cycle heat pump was performed by a time-stepping integration method. The nonlinear relationship between displacement and force for pistons was taken into account for the motion of reciprocating components, in addition to the pressure change of working gas, nonlinear viscous dissipative force due to an oscillating flow and discontinuous damping force caused by solid friction. The displacement of pistons and pressure changes in the Vuilleumier cycle heat pump were integrated by an ideal isothermal thermodynamic relationship. It was assumed that the flow friction was proportional to the kinematic pressure of working gas, and that the solid friction at the seals was due to the functions of the working gas pressure and the tension of seal springs. In order to investigate the dependence of the characteristics of a machine on various dynamical parameters, some calculations were performed for a proposed case study machine and discussed. The roles of working gas pressure, the displacer piston rod and dissipative force due to flow and solid friction were clarified, and the proposed method was found to be very effective in predicting dynamic behavior of free piston Vuilleumier cycle heat pumps and in designing the machine components.

A dynamic analysis of a free piston Vuilleumier cycle heat pump was performed by a time-stepping integration method. The nonlinear relationship between displacement and force for pistons was taken into account for the motion of reciprocating components, in addition to the pressure change of working gas, nonlinear viscous dissipative force due to an oscillating flow and discontinuous damping force caused by solid friction. The displacement of pistons and pressure changes in the Vuilleumier cycle heat pump were integrated by an ideal isothermal thermodynamic relationship. It was assumed that the flow friction was proportional to the kinematic pressure of working gas, and that the solid friction at the seals was due to the functions of the working gas pressure and the tension of seal springs. In order to investigate the dependence of the characteristics of a machine on various dynamical parameters, some calculations were performed for a proposed case study machine and discussed. The roles of working gas pressure, the displacer piston rod and dissipative force due to flow and solid friction were clarified, and the proposed method was found to be very effective in predicting dynamic behavior of free piston Vuilleumier cycle heat pumps and in designing the machine components.