An investigation of the mixing position in the recuperators on the performance of an auto-cascade refrigerator operating with a rectifying column

Based on case studies, the paper investigated the influence of the low pressure refrigerant mixing position in recuperators on the performance of an auto-cascade refrigerator operating with a rectifying column in theory and experiment. From temperature profiles in recuperators with the heat recuperated, a stable region and two unstable regions was found along the recuperators. When the mixing position is within the stable region, the specific refrigerating effect determined by the pinch point of recuperators can be obtained at the specified refrigerating temperature. But the given refrigerating temperature cannot be maintained for the same specific refrigerating effect when the mixing position is within the unstable region. In the stable region, the optimum mixing position with the minimum heat transfer area required for the given specific refrigerating effect exists. The average temperature difference of the high and low pressure refrigerants within the recuperators is the largest as well as the heat recuperated for the optimum mixing position. Experimental results agree with key points of the theoretical analysis. The new approach employed and results obtained in the paper will be valuable to the optimum design and application of the auto-cascade refrigerator in future.

► An auto-cascade refrigerator (ACR) operating with a rectifying column was studied.
► The influence of the mixing position in recuperators on the performance was investigated.
► A stable region and two unstable regions along the recuperators were found.
► The optimum mixing position in the stable region with the minimum heat transfer area was found.
► The minimum heat transfer area is based on the given specific refrigerating effect.