Abstract
This study was made to investigate the condensation local heat transfer and adiabatic pressure drop of R134a inside a 2.5 mm outside diameter smooth and microfin tube at low mass flux condition. Data were measured for mass fluxes from 50 to 300 kg m−2s−1, vapor qualities from 0 to 1 and saturation temperatures from 20 to 30 °C. The effects of mass flux, vapor quality, saturation temperature, microfin and diameter of test tube were analyzed. The pressure drop of the microfin tube was about 1.5 times higher than that of the smooth tube at mass flux 50 kg m−2s−1. The heat transfer coefficient of the microfin tube was about 2–5 times higher than that of the smooth tube at mass flux 100 kg m−2s−1. Experimental results were also compared with typical correlations. For the microfin tube, however, all the existing correlations do not adequately predict the present data. Poor predictions may be attributed to the lack of the small diameter microfin tube with low mass flux data in their database. Hence, it is essential to develop a condensation and pressure drop correlation for the small diameter microfin tube at low mass flux condition.
Highlights
The demand for air-conditioner and refrigerator is increasing in both developed and emerging countries along with the development of life standard
The rate of pressure drop increase was not same for the two tubes with the same experimental conditions: when mass flux increased from 50 to 100 kg m−2s−1 for smooth tube, pressure drop increased about 2.3–4.5 times, while, for microfin tube, pressure drop increased about 2.4–6 times
The frictional pressure drop increased with fin due to the pressure drop increased about 2.3–4.5 times, while, for microfin tube, pressure drop increased about
Summary
The demand for air-conditioner and refrigerator is increasing in both developed and emerging countries along with the development of life standard. To keep the pressure drop minimum of small diameter tubes, low mass flux operation of the refrigerant is necessary. There is a need to investigate the condensation heat transfer and adiabatic pressure drop inside the small diameter tube at low mass flux condition. Some studies have been done to analyze the condensation heat transfer and pressure drop characteristics of refrigerants inside small diameter microfin tubes, for example, tubes with outer. Some investigations on the condensation heat transfer characteristics and frictional pressure drop in microfin and smooth tube are not in good agreement. The condensation heat transfer and frictional pressure drop characteristics of R134a in small diameter smooth and microfin tube were investigated and the experimental data compared with some related studies
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