An air-charged Stirling-cycle refrigerator with novel isothermalisers

While the Stirling cycle is a simple thermodynamic cycle, energy dense machines are expensive and complex due to the complicated heat exchangers. Heat exchangers are essential to increase the heat transfer but they increase the dead volume, cost and pumping losses. In this contribution, a simple and novel isothermaliser is proposed that improves the cooling power density of the Stirling-cycle refrigerator without adding to the dead volume. Simulations based on the second order polytropic model show that the cooling power and efficiency can be enhanced and the regenerator losses can be significantly reduced. The novel isothermaliser leads to better performance than the conventional Stirling refrigerator at temperatures of 27/7o C achieving higher cooling density per swept volume of 2.5 folds. The increased power density enables the Stirling refrigerator to compete with the vapour compression cycle in both high-lift and near-ambient refrigeration.