COMPARATIVE OPERATION OF SMALL VUILLEUMIER CRYOCOOLERS UNDER ISOTHERMAL AND ADIABATIC CONDITIONS

Vuilleumier refrigerators capable of reaching cryogenic temperatures have been developed over the past years. A thermodynamic analysis can provide useful results concerning the energy quantities involved in this type of cryocoolers. Comparison of an isothermal and an adiabatic model yields the differences of the performance under each condition. Adiabatic cooling capacity is higher than the isotheimal, but the COP decreases. Additionally, the temperatures of the heat exchangers that reject heat and produce the cooling effect, affect the capacity and the performance of the cryocooler in opposite way. Furthermore, the cooling capacity is dependent on the pressure inside the machine and its speed, but the performance is not affected by these variables.