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在蒸发温度为5～15℃,热流密度范围为5～20 kW-m-2,工质质量流速变化范围为100～400 kgm-2s-1和干度范围为0.1～0.8的条件下,采用低电压、大电流的直流电源直接电加热的方法,对R134a在卧式螺旋管内的沸腾两相流传热特性进行了实验研究。结果表明,传热系数随工质干度和质量流速的增加而显著增加;热流密度对传热系数的影响也比较明显,传热系数随着热流密度的增加而增加,干度较小时热流密度对传热系数的影响更为明显;系统压力的变化对传热系数的影响较小。通过对实验数据的非线性回归分析,发展了R134a卧式螺旋管内流动沸腾局部传热系数的计算关联式。
Under the condition of evaporation temperature of 5-15 ℃, heat flux density range of 5-20 kW-m-2, working fluid mass flow rate of 100-400 kgm-2s-1 and dryness range of 0.1-0.8, Low voltage, high current DC power direct heating method, the R134a in the horizontal spiral tube boiling two-phase heat transfer characteristics of the experimental study. The results show that the heat transfer coefficient increases remarkably with the increase of dry mass and mass flow rate. The influence of heat flux on the heat transfer coefficient is obvious. The heat transfer coefficient increases with the increase of heat flux. When the dryness is small, the heat flux The influence of heat transfer coefficient is more obvious; the change of system pressure has little influence on the heat transfer coefficient. Through the nonlinear regression analysis of the experimental data, the calculation correlation of the local heat transfer coefficient of the flow boiling in the R134a horizontal spiral tube was developed.