IMPROVEMENT OF THE COOLING PERFORMANCE OF A FOOD PROCESSING STIRLING COOLER

摘要

The experimental free-piston Stirling cooler was described in a previous article and has now been improved. A sieve layer was added to the displacer (regenerator), which significantly enhanced the cooling performance of the cooler. A two-way analysis of variance test was used to confirm the optimal conditions (the type of mesh and thickness of the sieve layer) of the modified displacer, which was used in butter churning experiments. The results showed that only the thickness of the sieve layer had a statistically significant main effect on the cooling performance of the Stirling cooler. A comparison of the efficiency of butter churning using the original and modified displacer showed that with the modified displacer, butter clusters formed rapidly and that the quality of the butter was improved. Differential scanning calorimetry analysis showed that although the two types of butter cluster produced using the original and modified displacers had the same configuration, the content of fat and water was different. The results showed that the mass of the butter cluster manufactured with 25% fat content cream is higher than that of the butter cluster manufactured using 15 and 35% fat content cream. The results showed that the production of butter with more than 80% fat content seemed feasible.