Implement Method Of Multi-flow-path In Single Channel And Performance Research Of Plate Heat Exchangers

As an efficient and compact heat exchanger element, plate heat exchangers are widely used in petroleum, chemical industry and district heating system. The hot and the cold fluid flow unequal working condition exist widely in most of these industries. Owing to its singularity, plate heat exchanger cannot reach its full result. To cure the above problems, this paper presents a new type of plate heat exchanger. According to the size of lateral evenly divided the small flow side plate into three small processes by adding split gaskets to realize the hot and the cold fluid flow area unequal. By analyzes the data of numerical simulation and experimental research on heat transfer and flow characteristics of plate heat exchangers, it is proved that the new plate heat exchanger can fit the problem properly. Application methods on fabricating cost of plate heat exchanger are discussed through designing typical working condition.Gasket seals are furnished in plate heat exchanger zone, which are used to divide the whole channel into three zones. The fluid flows through three flow-paths from inlet to outlet, in order to increase fluid velocity and heat-transfer coefficient of low flow.The hot and the cold fluid flow area unequal plate heat exchangers are investigated numerically in water and oil respectively, to compare the convective heat transfer and friction coefficient of the divisional plate and the undivided plate under the same flow rate. Which reaches the oil convective heat transfer of divisional plate increases by about 30%, the friction coefficient increases a little; the water convective heat transfer show a slight increase, the friction coefficient increases by about 25%. As the fluid flow rate increase, the convective heat transfer of water and oil show a greater degree of increase. By analyzes the flow distribution on the fluid heat transfer surface, it is found that the velocity and the pressure drop of each small flow are uniform.According to the one shell-and-three tube heat exchanger correction factor graph, it gets the mean temperature difference correction factor of divided plate. Which is compared with numerical simulation results, their results is in agreement qualitatively.The length and the position of gasket are discussed, it turned out that gasket should make the fluid flow area of the corner close to the fluid flow area of main flow, the end of the shape better be round or oval. Which can reduce the flow disturbance effectively, and then reduce the local resistance loss. By analyzes the pressure distribution of plate cross section on perpendicular to the direction of fluid flow, it is found the pressure on plate contact points is the highest that the gasket should avoid them.The water-water and water-oil experiment of plate heat exchangers are carried out, it obtains the correlation formulas about the heat transfer and resistance of water and oil in divided and undivided plate. By analyzes the heat transfer and resistance characteristics with the change of Reynolds number of same fluid in divided and undivided plate, it finds that the heat transfer and resistance characteristics of water and oil are both increased in divided plate, the resistance of water increased more than it of oil, the heat transfer in oil increased more than it in water. A water-oil experiment of the flow area unequal plate heat exchangers are carried out for the convective heat transfer and friction coefficient of the divisional plate. Which are compared with numerical simulation results, it is found that the experiment convective heat transfer is lower than numerical data, and the experiment friction coefficient is higher than numerical data, the maximal errors are both lower than 8%.. Through the comparison of experimental mean temperature difference and numerical data under the same P and R, the maximal errors are lower than 3%, indicating the numerical simulation are reliable. The mean temperature difference of new plate heat exchanger can be obtained by referring shell-and-tube heat exchanger correction factor graph.The paper choose several groups of typical fluid heat transfer characteristics unequal working condition, and then use the flow area unequal and normal flow area equal plate heat exchanger to design respectively. It reach the results that the water-oil flow area unequal plate heat exchanger can save 27% heat transfer area under the same thermal load, the fluid change into water-water, the heat transfer area can be save 49%. In conclusion, the new plate heat exchanger is more economical in industry application.