Thermal performance analysis for hot-wall condenser and evaporator configurations in refrigeration appliances

Abstract A sensitivity study is presented about the investigation of the influence exerted by the design parameters on the thermal performance of those refrigeration appliances employing hot-wall condenser and evaporator configurations, compared to the usual refrigerators, in which external heat exchangers are used. The heat transfer rates inside the wall of the hot-wall refrigerator were evaluated by means of a parametric finite element model; in particular, a chest freezer for domestic applications was considered. A thermodynamic approach was employed to assess the relative heat transfer merits of the apparatus (in respect of a usual refrigerator) from the point of view both of the thermodynamic performance and of capacity. The sensitivity analysis of the design parameters affecting the performance was developed (for fixed working temperatures) with reference to the thickness of the metallic plates, the thickness of the insulating foam, the evaporator and condenser tube diameters and pitches, and the thermal contact resistance between the tubes and the plates. The results show the great importance of the 2-D heat conduction in the metallic plates (`fin efficiency effect'), evidencing how the plate thickness and the thermal contact resistance between the refrigerator plates and the tube serpentines affects the global effectiveness of the system. Some practical suggestions are drawn in conclusion on the criteria which should be adopted in the thermal design of a hot-wall refrigerator.