Study On Heat Transfer Characteristics Of Shell-side Two-phase Flow In Shell-and-tube Heat Exchanger Of Seawater System In Polar Carrier

The heat exchanger is the equipment for heat exchange of hot and cold fluid,The comprehensive performance of heat exchanger has a crucial impact on its normal operation.In order to guarantee the safe navigation of the polar carrier in the Arctic region,in this paper,CFD numerical simulation software FLUENT was used to simulate and analyze the shell and tube heat exchangers which acted as the oil cooler in the seawater system of a polar carrier.The structural parameters of the heat exchanger were optimized and the flow and heat transfer characteristics under different initial conditions were analyzed.The main research contents and conclusions of this paper are as follows:1)As the object of this study involves the flow heat transfer process of seawater-ice two-phase fluid,in this paper,the fluid medium was regarded as an incompressible fluid,and the diffusion phase and the continuous phase were regarded as continuous media based on the concept of two fluids.The Euler-Euler two-phase flow model was used as the numerical model of the heat exchanger.2)Based on the analysis of the structure of the shell and tube heat exchanger,in view of the complexity of its structure,the heat exchanger model was simplified and the geometry was established by modeling software without affecting the numerical results,and then grid partitioning and grid independence verification was carried on.3)The arrangement of the heat transfer tube bundle were analyzed,through numerical analysis,the conclusion showed that the triangular heat transfer tube bundle was more suitable for the research object in this paper,and the accuracy of the numerical model was verified.4)The baffle plate spacing(number)and the notch height of the baffle plate have great influence on the performance parameters of the heat exchanger.Based on the analysis of the velocity field,temperature field and pressure field of the heat exchanger under different baffle parameters,the heat exchanger is optimized by the thermal performance analysis method(h0/? p)combined with the heat transfer coefficient and the flow resistance loss.When the baffle structure parameters: the number is 4,the gap height is 0.4D,the comprehensive performance parameters are higher with superior heat transfer efficiency.5)The numerical simulation of the flow velocity V and the IPF(Ice Packing Factor)under different seawater-ice crystals two-phase fluid of the heat exchanger shell was carried out on the heat transfer equipment.In order to ensure that the ice crystal particles will not accumulate retained in the heat transfer equipment,affecting the normal operation,the analysis showed:(1)When the fluid medium flowed in the flow range of 1.5m/s-2.5m/s,the flow of energy to overcome the flow resistance of the energy consumed less,the heat transfer equipment can operate normally and has a better heat transfer efficiency;(2)2%-8% is the optimal interval of IPF.At this time,the the flow resistance of the heat exchanger will not be too large due to the high rate of IPF,resulting in the accumulation of ice crystals in the heat exchanger,affect the high efficiency of the normal operation of heat exchanger and even malfunction.Therefore,under certain conditions,in order to ensure the normal operation of the heat exchanger,so as to ensure the safety of the ship's navigation,the flow rate V and the IPF changes in the range of control within a certain range is necessary.