Dissertation > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Thermal Engineering Theory > Heat Transfer

Research on Compact and Saving Energy Heat Exchanger for Trans-critical Carbon Dioxide Air Conditioning

Author WangRenYuan
Tutor WuJinXing
School Zhengzhou University
Course Refrigeration and Cryogenic Engineering
Keywords Supercritical CO2 Microchannel Louver fin Arc Heat Transfer Drop Characteristics
Type Master's thesis
Year 2010
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Transcritical CO2 cycle system with excellent environmental characteristics, good heat transfer properties, low flow resistance and a large cooling capacity per unit volume so that it has a broad application prospects, while there is a low efficiency of the system and the system caused by high pressure equipment and pipeline safety problems to be solved. In this paper, supercritical CO2 as the research object, the numerical simulation method for the study of trans-critical CO2 air conditioning system heat exchanger were studied. The main research contents and the results achieved in the following areas: 1 pair of existing trans-critical CO2 refrigeration system heat exchanger comprehensive analysis found transcritical CO2 refrigeration system efficiency depends on the heat exchanger performance improved, and development of micro-channel compact heat exchanger to solve the supercritical CO2 refrigeration systems and equipment safety problem of low efficiency has a crucial role. Two pairs of physical properties of supercritical CO2 were analyzed using low Reynolds number LB model microchannels supercritical CO2 at different mass flow rate and pressure drop characteristics of heat transfer characteristics and the numerical calculation and the experimental data with the literature match better, also found that different heat flux on the microchannel heat transfer characteristics of supercritical CO2 and pressure drop characteristics have little effect. Three pairs of air-side heat transfer fins using blinds to build a three-dimensional air and fins coupled simplified geometric model, using Laminar model to calculate the heat transfer tube outer louver fins and resistance characteristics, and with the experimental data in the literature and empirical formula comparison of the data obtained, the degree of fit is better for the next louver fin structure parameter optimization and development of research methods provided. 4 In order to further clarify the air-side heat transfer fins enhanced performance, were investigated different fin height, window height wings, fin thickness and structural parameters such as fin pitch on the heat transfer coefficient and pressure drop, using Considering the heat transfer and pressure drop characteristics of the heat transfer - Pump power consumption function comparison method louver fin structure parameter optimization, to obtain a comprehensive set of louver fin structure better performance parameters. 5 developed a new fin curved shutters, window wings to different angles and under different louver fin radians numerical simulation study, get new curved louver fin heat transfer and pressure drop characteristics are more general louver fin an increase in the average heat transfer coefficient of increase up to 9.47%, the maximum amplitude of the average increase in pressure drop was 3.2%; louver fin, and on the whole arc of increase of the heat transfer coefficient of increase is higher than the pressure drop, play heat transfer enhancement purposes. In this paper, trans-critical CO2 refrigeration system parallel flow microchannel heat exchanger tube supercritical CO2 louver fin and tube outer numerical simulation study different pressures, mass flow rate and heat flux on the tube heat exchanger with supercritical CO2 pressure drop performance, analysis of different louver fin geometry on the tube outside air flow and heat transfer, and the development of a curved louver fin, has a certain value in engineering and academic significance.

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