Study Of Direct Contact Heat Transfer Performance Of Opening SK Static Mixer

Agriculture,as the basis of survival,has made a great contribution to the development of China’s economy and needs to be developed on the basis of achieving the economical use of agricultural energy in order to give agriculture a better chance of sustainable development,so agriculture should develop innovative strategies to improve the utilization of energy in the construction process.Direct contact heat exchangers,as an efficient heat exchange equipment that can improve energy utilization,are also widely used in agricultural energy,such as biomass utilization,thermal energy storage,drying of agricultural products and solar thermal utilization.Compared to inter-wall heat exchangers,direct contact heat exchangers allow direct contact between hot and cold fluids,eliminating the problem of lower heat transfer efficiency due to heat transfer through solid walls,and are simple in structure and easy to clean.However,it is not guaranteed that the cold and hot fluids are in full contact in the direct contact heat exchanger with empty tubes,resulting in the failure to bring the direct contact heat transfer efficiency between fluids to a large enough level.The method of applying SK static mixing elements inside the direct contact heat exchanger can enhance the degree of mixing between cold and hot fluids and improve the heat transfer efficiency.To further enhance the heat transfer efficiency of direct contact heat exchanger and improve the efficiency of energy utilization,this dissertation is proposed the design of openings on SK static mixing element and its application in direct contact heat exchanger.And adopts the numerical simulation method of computational fluid dynamics(CFD)to study its heat transfer performance,which has certain guiding significance for improving the heat transfer efficiency of direct contact heat exchanger.The main studies are as follows:(1)The perforation index(PI)was introduced to guide the perforation design of the SK static mixer.With a fixed value of PI,five different SK direct contact heat exchangers with n=1,2,3,6,and 9 different numbers of perforations were designed.Among them,when n=2,3 and 6,two different ways of opening holes on the SK static mixer are used,one is arranged vertically and the other is arranged horizontally.Ansys Workbench’s Fluent module was used to construct the geometrical model,perform the meshing and direct contact heat transfer simulations,in which the meshing was analyzed for mesh independence and an experimental platform was built to validate the numerical simulations.(2)The effect of SK static mixing elements with different numbers of openings on direct contact heat transfer is investigated for continuous phases(heat transfer oil-THERMINOL~?62)and dispersed phases(organic working substance-R141b)at three initial heat transfer temperature differences.The calculation results show that the SK static mixing element with small or more holes have better optimization effect on direct contact heat transfer,and the smaller hole size can break up the bubble group of gaseous mass,which increases its surface area and enhances the heat transfer between fluids.In particular,at an initial heat transfer temperature difference of 50°C,the volumetric heat transfer coefficient of the 9-hole SK direct contact heat exchanger is approximately 20%higher than that of the SK direct contact heat exchanger without open holes;at initial heat transfer temperature differences of 30°C and 70°C,the volumetric heat transfer coefficient of the 6-hole SK direct contact heat exchanger is approximately 20%higher than that of the SK direct contact heat exchanger without open holes.(3)The effect of SK static mixing elements with different opening positions on direct contact heat transfer was investigated for continuous(heat transfer oil-THERMINOL~?62)and dispersed phases(organic working substance-R141b)at three initial heat transfer temperature differences.The results show that,compared to the vertical opening,the horizontal opening in the SK static mixing element improves the homogeneity,turbulence intensity and volumetric heat transfer coefficient of the direct contact heat exchanger,with the volumetric heat transfer coefficient increasing by up to 18%.