Experimental Study On Boiling Heat Transfer In Shell And Tube Heat Exchanger

As an important equipment in petroleum and chemical industry,The shell and tube heat exchanger play a large role in conserving energy and reducing emissions in the industry. In recent years,with the developing of heat transfer technology, The spiral flat tube as a kind of widely used heat exchanger also developes fastly.the scholars at home and abroad did researches on two phase flow boiling flow and heat transfer characteristics one after another. There is a deviation results from different researchers due to the complexity of two phase flow and the limitation of the experimental conditions.In addition there is less research on the effects of heat transfer and flow for the non-condensable gas. So this article is based on the gas-liquid two phase flow medium in the flat spiral tube heat exchanger tube bundles.In the process of two phase flow boiling heat transfer experiment to add a little amount of noncondensable gas. The main research work is as follows:1、Through the analysis of experimental data, the two phase flow and heat transfer characteristics are along with the Reynolds number, the prandtl number, quality, rate of gas and liquid phase change laws of import volume flow to change.in terms of flow characteristics frictional resistance increase with the increase of the pressure drop along with the prandtl number; Within a certain range, frictional resistance did cyclical fluctuations with the increase of gas rate. The fluctuation cycle increases gradually,and the wave did amplitude along with the increase of the liquid import volume flow. in terms of heat transfer characteristics,In the conditions of presence of non condensable gas the average Nusselt number increases with the two-phase flow boiling heat transfer of Reynolds number. In the process of boiling heat with the low gas flow rate,the flux density decreased with the increase of gas rate. It showed cyclical fluctuations with the further increase of gas rate.2% On the basis of above experiments,experiment was conduscting by changing the pitch. Explore the different pitch sizes did the influence for the two-phase boiling flow and heat transfer characteristics. Find when did the experiment with small pitch, The increasing amplitude of Nusselt number was accompanied with the increasing of Reynolds number, and the maximum value of Nusselt number is larger than the high pitch. So it had better effect of heat transfer. The heat transfer did the more significant enhancement with the increasing of Reynolds number. when did the experiment with small pitch,The heat flux did larger decline with the decline of the gas rate. With the increase of gas rate, The fluctuations wave period becomes larger for periodic heat flow density, and the fluctuation frequency becomes smaller.3、Based on the previous research model foundation, according to the collation and analysis of experimental data. This study used mathematical analysis software for multivariate nonlinear regression analysis,then got the empirical correlation about the frictional pressure drop and average Nusselt number. They also had certain value for engineering application.