Comparison of Boiling characteristics between Conventional and Environmentally Accepted New Freons

主要的实验结果如下：1.混合物的池核沸腾-对不同组成的混合物R11-R11 3和乙醇-水在宽压力和热流密度范围内进行了实验。(i)现有的混合物沸腾中常见的传热恶化预测方法无法再现观察到的恶化率随压力的变化。(ii)观察到的组合物，其中传热系数采取最小值从预测值移动到较低浓度的更易挥发的组分。(iii)传热恶化可能与传质阻力有关，如果恶化是基于与混合物具有相同性质的假想纯液体的传热系数来评估的。目前提出的纯液体的关联式对于这个目的是没有用的。混合物R11-R113在垂直管中的流动沸腾进行了测试，改变组成、质量比、温度和温度。 ...更多信息 速度和热通量(i)在低干度下，还观察到池沸腾中遇到的传热恶化。(ii)对应于从核态沸腾到两相强制对流的过渡，混合物的传热系数也随干度的增加而逐渐增大，但过渡质量略低。(iii)在高品质下，混合物的传热性能没有恶化。(iv)现有的沸腾数关联式不能涵盖较宽压力范围内的数据。提出了新的关联式，该关联式考虑了低品质时的传热恶化.用新的氟里昂R123代替R11，在压力P= 0. 5范围内进行了上平板饱和沸腾实验。1至3.2MPa和热通量q=3000至600000 W/m2。(i)无论是传热系数的水平和压力和热通量的影响是类似的R11。(ii)实验传热系数h[W/m2 K]与h = 1.58 f（P/Pc）* qO有很好的关联。其中q：热通量[W/m2]，P/Pc：减压[-]，F（P/Pc）=（P/Pc）0.23/（1-0.99*（P/Pc）0.9）。(iii)Zuber的关联式适用于预测临界热流密度。少

Results are summarized about three major experiments as follows.1. Nucleate Pool Boiling of Mixtures --- Mixtures Rll-Rll3 and Ethanol Water of different compositions were tested under the wide ranges of pressure and heat flux. (i) The existing predictive methods of heat transfer deterioration, encountered usually in mixture boiling, cannot reproduce the observed change with pressure of the deterioration rate. (ii) The observed composition where the heat transfer coefficient takes the minimum shifts from the predicted value to lower concentration of more volatile component. (iii) Heat transfer deterioration might be related to the mass transfer resistance, if the deterioration was evaluated based on the heat transfer coefficient of the imaginary pure liquid with the same properties as the mixture. Existing correlations proposed so far for pure liquids are of no use for this purpose.2. Flow Boiling of Mixture --- Mixture Rll-Rll3 in a vertical tube was tested varying composition, mass v … More elocity and heat flux. (i) At low quality, the heat transfer deterioration encountered in pool boiling is also observed. (ii) Corresponding to the transition from the nucleate boiling -io the two-phase forced convection, the heat transfer coefficient for mixtures also rises gradually with increasing quality, but the transition quality is somewhat lower. (iii) At high quality, The heat transfer deterioration is not observed for mixtures. (iv) The existing correlations with the boiling number cannot cover the data over the wide range of pressure. The new correlation was proposed accounting for the heat transfer deterioration observed at low quality.3. Pool Boiling of Altei, native Freons --- By using the new freon R123, an alternative to Rll, the saturated boiling from the upward-facing plate was experimented over the ranges of pressure P=O. l to 3.2 MPa and heat flux q=3000 to 600000 W/m2. (i) Both the level of heat transfer coefficient and effects of pressure and heat flux are similar to those for Rll. (ii) Experimented heat transfer coefficient h[W/m2K]is well correlated by h = 1.58 f(P/Pc)* qO. 8, where q : heat flux[W/m2], P/Pc : reduced pressure[-]and F(P/Pc)=(P/PC)0.23/(1-0.99*(P/Pc)0.9). (iii) Zuber's correlation is applicable to predict the critical heat flux. Less