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Experimental studies of evaporation and condensation of refrigerants inside a tube have often been carried out using a double-tube heat exchanger, where the refrigerant flows inside the inner tube and... the water flows countercurrently in the surrounding annulus. To consider a method of measuring the heat transfer coefficient of refrigerants inside the inner tube, the heat transfer characteristics of a double-tube counter flow heat exchanger were calculated in the case of fully developed turbulent single phase flow inside the inner tube and developing laminar single phase flow in the annulus. Based on the calculation results, following two kinds of heat transfer coefficients, which can be measured experimentally, were obtained. α_<R1>=q_w/(T_<Wi|z/L=0.5>-T_R) α_<R2>=q_w/(T_<Wim>-T_R) where q_w is the average wall heat flux, T_<wi|z/L=0.5> is the inner wall temperature at the central position of the tube lengh L, T_R is the reference refrigerant temperature, and T_<wim>, is the inner wall temperature averaged over the tube length. The values of α_<R1> are 5 to 23% higher than the values of heat transfer coefficient, given as a parameter in the calculation, due to the axial change of heat transfer characteristics in the annulus, while the values of α_<R2> are nearly equal to the values in the calculation. To eliminate the influence of the heat transfer characteristics in the annulus, the measurement of α_<R2> is recommended. If α_<R1> is measured, a correction function should be preliminarily determined.続きを見る
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Mendeley出力
KJ00004507653