Numerical Simulation For Shell-side Passes Of A Shell-and-tube Heat Exchanger And Research On Structural Optimization

For some shell-and-tube heat exchangers with single segmental baffles fluid in the shell-side changes flow direction in the windward side and washes the exchanger tubes vertically as a result of the blocking of the baffles, and then rounds the baffle through the segment. The flow shows Z-type, which favors heat transfer enhancement. However, the blocking makes pressure drop in the shell-side increase and causes fluid to flow slowly in the leeward, it is influential to heat exchange that the local heat can not be transferred in time.The paper established j-f factor made up of heat transmission factor j and friction factor f, acted as an evaluating indicator of comprehensive heat transfer performance to a heat exchanger j-f factor could reduce the effects of velocity response of pressure drop in the shell-side and make heat transfer coefficient keep subject position, so it can reasonably evaluate the comprehensive heat transfer performance. ThenThe paper did research on baffle opening optimization to the cut height of 0.2D. by numerical simulation Firstly research on the baffle opening layouts was done. Finding different baffle opening layouts affected the fluid field in the shell-side to different degrees, but j-f factor was always greater than 1, the stagnation with a low speed in the leeward of the baffles flowed faster, pressure drop in shell-side reduced, temperature gradient and velocity gradient reduced, comprehensive heat transfer performance increased. The paper established the optimal baffle opening layout based on j-f factor value. Then numerical simulations on 18 sets of apertures based on the optimal baffle opening layout. The results indicated that j-f factor was always greater than 1, j-f factor increased 3.58%～17.66% with the increasing of area opening, and then decreased. Then, the optimal aperture was found.In the end research on how inlet velocity of the shell-side affected the optimal results was done. Within the permissible velocity range the velocity increased from 0.3m/s to 1.3m/s progressively, the results indicated in the shell-side pressure drop and heat transfer coefficient increased with the increasing of the inlet velocity, j-f factor based on optimal aperture always kept the maximum, indicating the inlet velocity made no difference on the optimal results.