IMPROVEMENT OF THE COOLING PERFORMANCE OF A FOOD PROCESSING STIRLING COOLER
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. PRACTICAL APPLICATIONS
Because a free-piston Stirling cooler uses no Chlorofluorocarbons as working fluid, it is applicable to food processing required for environmental sustainability recently. According to the vertical shaking of the cylinder of the experimental Stirling cooler, the process is available to apply for butter churning with refrigeration and mixing simultaneously. According to a smart design, the performance of the Stirling cooler was improved, and the results showed that using the Stirling cooler to produce butter was a highly feasible option. Improving the cooling efficiency of the Stirling cooler enhanced its suitability for butter churning.
Document Type: Research Article
Affiliations: Bioindustrial Sciences ProgramGraduate School of Life and Environmental SciencesUniversity of Tsukuba1-1-1, Tennodai, Tsukuba, Ibaraki 305-8572, Japan
Publication date: December 1, 2010