Study On Falling Film Heat Transfer Theory Research Of Spray Heat Exchanger

Currently, the environment and energy problems are becoming worse and worse. To develop and use new energy and research new technology and method will be helpful to alleviate the tense situation concerning environment and energy. Therefore, this essay takes the spray heat exchanger, the core part of polluted water heat pump as the study object, to carry out research on the falling film heat exchange on the outside of the horizontal single pipe, The main research are summarized as follows:Firstly, this essay introduces17 heat exchange correlation equations of falling-film heat exchange model, and compares the Nusselt number calculated through the correlation equations to that of the test so as to screen out the correlation equations the calculating result of and the fluctuation trend of which is similar to that of the test. This correlation equation derives from heat exchange model of J.T.Rogers. After further modification, it could be used to analyze the heat exchange characters of the spray heat exchanger.Secondly, according to the method Gimbutis used to revise the model of W.M.Rohsenow, the correlation equation is fitted and revised, and the revised result is testified. In order to guarantee the validity of the fitting, the data used in fitting and revision come from different tests in which the pipes and the distance between the pipes are all different. Afterwards, in the partial revising process of the model, this essay, based on the basic theoretical framework of J.T.Rogers, with variables added such as physical property and liquid film fluctuation, re-establishes the division limit, discusses the critical condition for the existence of full development division and revises partial Nusselt number formula of different divisions to finally get the heat exchange correlation equation that can be applied in spray heat exchanger.Later, according to the above-mentioned theoretical results, the thickness distribution feature and heat transferring feature of the spray heat exchanger is analyzed. During the analysis of the thickness distribution feature, this essay first uses test data to testify the thickness equation of J.T.Rogers’ model, then compares that to other equation of liquid film thickness in other literature, and finally conclude the thickness distribution rule of the liquid film. On the analysis of the heat transferring feature, this essay studies the distribution features of Nusselt numbers along the circumferential direction in different divisions and presents the distribution rules vividly by simulation.At last, based on the above-mentioned thickness distribution feature and the heat transferring features, this essay calculates the average Nusselt number and liquid film thickness on the hypothesis that the spray heat exchanger is used under more general conditions. Also, in accordance with this calculation result, some suggestions are brought up for improvement with the purpose of providing theoretical groundings for practical application of the spray heat exchanger.