Investigation and Numerical Simulation on Condensation Heat Transfer of Shell and Tube Heat Exchanger
|School||Huazhong University of Science and Technology|
|Keywords||shell and tube heat exchanger condensation heat transfer numerical simulation Fluent|
Shell and tube heat exchangers are widely used in refrigeration, petrochemical industry, energy source, aviation and other fields, because they have some features such as simple structure, mature technology, easy to clean, wide applicability. Now, the energy are shortage, and their prices are soaring, so the problems about using&recovering heat energy maximally and enhancing heat transfer are concerned gradually. Steam condensation is heat transfer process with phase change. Compared to heat transfer process with no phase change, the heat transfer efficiency of steam condensation is better. Therefore, the investigation on condensation heat transfer has become one trend. Traditional shell and tube heat exchangers often use segmental- baffled support structures and smooth tube bundles, which have simple manufacturing processes, strong adaptability. However, the heat exchangers have high resistance in shell side, and the heat transfer efficiency is not ideal.In order to improve the comprehensive performance of shell and tube heat exchangers, in this paper, the heat transfer mediums are water and steam, and an investigation on condensation heat transfer characteristics outside horizontal smooth tube, spiral corrugated tube and transversally corrugated tube are carried out. Besides, according to boundary conditions given by experimental data, numerical stimulations with Fluent software about tube side and shell side of shell and tube heat exchanger are made. The main contents and conclusions of the paper are as follows:(1) An investigation that the effects of tube side and shell side fluid flow rate on condensation heat transfer is carried. When the baffles are different, as tube side fluid flow rate varies, the changing regularities of total heat transfer coefficient and condensation heat transfer coefficient to three kinds of tubes are different. However, when steam heat flux in shell side is increased, total heat transfer coefficient and condensation heat transfer coefficient to three kinds of tubes are increased.(2) The experiment studies the effect of the baffle spacing on heat transfer efficiency. The results indicate that when the rod baffle spacing is 100mm, heat transfer efficiencies of smooth tube and transversally corrugated tube are best, while spiral corrugated tube, 200mm.(3) The experiment studies the effects of different baffles and tube shapes on condensation heat transfer efficiency. The results indicate that heat transfer efficiency of rod baffle heat exchanger is better than that of segmental baffle heat exchanger. But, to different tube shapes, the improving level of heat transfer efficiency is different. When the baffle spacing is 200mm, heat transfer efficiency of spiral corrugated tube heat exchanger with rod baffle is best, total heat transfer coefficient and condensation heat transfer coefficient are most enhanced 50% and 142%.(4) Compared to two steam entrances, the heat transfer efficiency is better when steam gets into heat exchanger from one entrance. To different tube shapes, the excellent degree is different, but spiral corrugated tube is best.(5) In all experimental conditions, when the spacing is 100mm, heat transfer efficiency of transversally corrugated tube heat exchanger with rod baffle is best.(6) Heat transfer efficiency of transversally corrugated tube heat exchanger with rod baffle(heat exchangerⅠ) and spiral corrugated tube heat exchanger with rod baffle(heat exchangerⅡ) are better than that of traditional smooth tube heat exchanger with segmental baffle (heat exchangerⅢ). Compared to heat exchangerⅢ, heat transfer coefficients of heat exchangerⅠand heat exchangerⅡare most enhanced 114%, 69%.(7) Numerical simulations to tube side and shell side of heat exchanger with the Fluent software are made. The paper analyzes temperature fields, velocity fields, turbulence intensity fields of element model and entity model. By comparing numerical results and experimental results, it can be found that numerical simulation to shell and tube heat exchanger is valid.