Abstract:

The decrease in length-diameter ratio may lead to some technical problems in shell-and-tube heat exchangers, such as fluid flow maldistribution, sharp increase of pressure drop, and performance deterioration.In order to solve above problems, two techniques are proposed in this study, application of a novel structure of multi-parallel-channel inlet/outlet (MPC）and installation of fluid flow distributors (FDBs）in the region of inlet/outlet in shell-side.The shell-side fluid flow is simplified according to its structural characteristics and the unit duct model is established.By employing commercial CFD software of FLUENT 6.3, the numerical investigation on shell-side fluid flow was carried out.The numerical model and method were confirmed by experiment.Without FDBs and with FDBs of different punching ratios, both shell-side velocity distribution and resistance were investigated with different values of Reynolds number and number of tube rows (N).Without FDBs, as N decreases, the distribution of shell-side is effectively improved and the resistance is reduced sharply, with more than 70% of total pressure drop reduced when N decreases from 11 to 7 at the same Re.FDBs improve the shell-side fluid distribution effectively, but increase the shell-side pressure drop.The comparison shows that the fluid flow distributor with the best fluid flow distribution gives the largest pressure drop, about 10%—12% larger than that without FDB and about 4%—6% larger than that with other two FDBs.The largest pressure drop of shell-side is generated in the regions of inlet and outlet.