Boiling heat transfer and critical heat flux in pool boiling of ammonia-water mixture

在较高压力P=0.7 ~ 1.5MPa和较低压力P= 0.1 ~ 0.7MPa条件下，测定了氨-水混合物在氨质量浓度C=0.5 ~ 1和0 ~ 0.3范围内的池沸腾传热系数。传热特性可根据热通量分为三个部分，例如低、高和第二瞬态热通量区。在本研究中，热传递系数被处理在两个区域的高和第二瞬态热流区。在C=0.1 ~ 0.9的范围内，与纯液相比，传热系数显著降低。然而，发现热传递变得比氨的热传递大0.97的范围。通过对实测传热系数与现有的几个关联式的比较，发现没有一个关联式能很好地预测传热系数。因此，通过修正Stephan和Korner相关性，提出了一种新的相关性，因为它们的相关性显示出类似的趋势。关系式为：h=1/B（（1-C）/h_1+C/h_2）其中B=1+A_0| y_1-（1-C）|h_i=d_i（P/P_s）^n（f_q）^B/R（i=1和2）是由Nishikawa和Fujita给出的每种纯液体的传热系数。y_1的值为水蒸气的mss浓度。用表中所列的值，可以很好地预测传热系数。

Heat transfer coefficient has been measured during pool boiling of ammonia-water mixture at a ammonia mass concentration ranging from C=0.5 to 1 at a higher pressure of P=0.7 to 1.5 MPa and from 0 to 0.3 at a lower pressure of 0.1 to 0.7 MPa. The characteristics of heat transfer can be categorized into three parts depending on heat fluxes such as low, high and second transient heat flux regions. In the present study, the heat transfer coefficients are treated in the two regions of high and second transient heat flux regions. The heat transfer coefficients dramatically decrease in the mass concentration ranging from C=0.1 to 0.9 compared with those for both the pure liquid. However, the heat transfer is found to become around range of 0.97 larger than that for ammonia. On comparison of the measured heat transfer coefficients and several existing correlations, it is found that no correlation can predict the heat transfer coefficients well. Therefore, a new correlation is proposed by revising the Stephan and Korner correlation, since their correlation shows a similar trend. The correlation can be given in the following form :h=1/B ((1-C)/h_1+C/h_2)where B=1+A_0|y_1-(1-C)|(0.88+0.12P), and h_i=d_i(P/P_s)^n(fξq)^b/R of i=1 and 2 are heat transfer coefficients for each pure liquid given by Nishikawa and Fujita. The value of y_1 is mss concentration of water vaporThe heat transfer coefficients can be predicted well by the above correlation with the value listed in Table.