Theoretical investigation of the evaporation heat transfer cofficient of refrigerant R-134a in a plate heat exchanger

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Title: Theoretical investigation of the evaporation heat transfer cofficient of refrigerant R-134a in a plate heat exchanger
Author: Donowski, Vincent
Abstract: The evaporation heat transfer coefficient of refrigerant R-134a flowing in a plate heat exchanger is investigated analytically in this study. With the introduction of new HFC refrigerants to replace CFC refrigerants, the understanding and modeling of heat transfer coefficient characteristics is important in designing more efficient evaporators for refrigeration and air conditioning applications. In the present work experimental data for two-phase evaporation heat transfer of refrigerant R-134a in a plate heat exchanger (Yan and Lin, 1999b) is compared with relevant published correlations (Yan and Lin, 1999b; Kandlikar, 1991) in order to explore a proposed correlation scheme to best predict the data set. Experimental data for the evaporation heat transfer of refrigerant R-134a in a plate heat exchanger could only be found published by Yan and Lin (1999b). Their work utilizes a single pass plate heat exchanger, consisting of three plates, to collect two-phase flow data. In the present work, resulting correlations proposed by Yan and Lin (1999b) are found to have large discrepancies from the data for both a single-phase water-to-water experiment and the two-phase experiment for evaporation heat transfer coefficient of refrigerant R-134a in a plate heat exchanger. Research of other literature revealed the Kandlikar (1991) model for correlating flow boiling heat transfer in augmented tubes and compact evaporators to have relevance in the present study. In the present work one correlation for the single-phase water-to-water experiment, and two correlation schemes for the two-phase refrigerant R-134a experiment are proposed which best fit the experimental data presented by Yan and Lin (1999b) for the plate heat exchanger. The new single-phase correlation provides an accurate prediction to the data. The first proposed two-phase correlation utilizes augmentation factors similar to those proposed by Kandlikar (1991). Results for this correlation are within 17% of the experimental data. Augmentation factors are ignored in the second proposed two-phase correlation, which predicts the data within 16%. Both correlations provide better results than the Kandlikar model (Kandlikar, 1991), which predicts the data within 20% for vapor quality between 0.2 and 0.8, and the correlation proposed by Yan and Lin (1999b), which yields a large discrepancy from the data. The second improved two-phase correlation shows only nominal improvement over the first, and lacks a theoretical base. As a result, the first two-phase correlation scheme developed in this thesis work is suggested for use in the specific case of evaporation in the plate heat exchanger.
Record URI: http://hdl.handle.net/1850/13955
Date: 1999

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