水平强化管管外R407C降膜蒸发换热特性实验研究

Experimental Study on the Falling Film Evaporation Heat Transfer Performance of Working Medium R407C outside the Horizontal Enhanced Tube

搭建降膜蒸发实验台,对水平布置的强化管单管外的降膜蒸发换热特性进行了实验研究。实验强化管外径为19 mm,有效长度为2 500 mm。实验采用一种新型布液器,布液采用滴淋方式,以R407C为管外降膜蒸发工质,与管内热水进行热交换,分别在变蒸发管管内流速(1、1.5、2、2.5、3m/s)、变喷淋量(0.08~0.16 kg/(m·s))、变蒸发温度(2.5~16℃)和变热流密度(15~40 k W/m^2)的情况下进行实验,得到了R407C在管外降膜蒸发时的特性:随着热流密度的增加,传热系数不断增大;随着喷淋量的增加,传热系数先增大后减小,降膜蒸发存在一个最佳喷淋量;随着蒸发温度的升高,传热系数不断增大。同时分析了强化传热的原理。

By setting up a falling film evaporation experiment table,an experimental study was carried out in order to investigate the falling film evaporation heat transfer performance outside a single horizontal enhanced tube. The outer diameter of the enhanced tube is 19 mm and its effective length is 2 500 mm. A new-model liquid distributor was used in the experiment with the trickle manner for the liquid arrangement. R407 C was used as falling film evaporation working medium outside the tube to exchange heat with hot water inside the tube. Experiments were performed respectively under the conditions of various flow velocity inside the evaporation tube( 1,1. 5,2,2. 5,3 m / s),of various spray rate( 0. 08 ~ 0. 16 kg /( m·s)),of various evaporation temperature( 2. 5 ~ 16 ℃),and of various heatflux density( 15 ~ 40 k W / m^2). The falling film evaporation performances of R407 C outside the tube were obtained. With the increase of heat-flux density,the heat transfer coefficient was increasing. With the increase of spray rate,the heat transfer coefficient increased firstly and then decreased and the falling film evaporation corresponded to an optimum spray rate. With the increase of evaporation temperature,the heat transfer coefficient was in-creasing. In addition,the principle of heat transfer enhancement was analyzed in this paper