Numerical Investigation On Fouling Performance In Heat-exchanger Based On Von-Karman Analogy

Fouling in enhanced heat exchangers is a comprehensive and complex problem, which has many influential factors, so more investigations are needed in the detail researches of heat transfer and fouling performance in heat exchangers, which have substantial significances and actual applications. From mass balance and numerical simulation in the investigation on the flow and heat transfer performance of enhanced heat exchangers, this paper uses Von-Karman analogy to predict the fouling performance in three internal repeated rib tubes and three corrugated plate heat exchangers with different geometries. Additionally, the influences of fluid velocity and geometries have been discussed and compared with experimental data, which can be used to optimize the designs of heat exchangers generally and broaden its further applications. Results are as follows:(1) The turbulent model with non-equilibrium wall functions is used in the3D numerical simulation to obtained Nusselt number and wall shear stress, while the Von-Karman analogy is used to obtain mass transfer coefficient. By comparing the results with experimental data, the investigation method the paper used is right.(2) The different geometry parameters of internal repeated rib tubes are investigated to find their influence on stream line, wall shear stress and fouling resistance. To explain the diversity of anti-fouling performance in different tubes, the rib distance is the most important parameter. If it is too large for the stream line to develop or too small to disturb the reattachment, the wall shear stress will not big enough to peel off the fouling deposition, which can results a poor fouling performance.(3) The Nusselt number, friction factor and wall shear stress is calculated in the three corrugated plate heat exchangers with different geometries parameters including plate height, plate spacing and plate angle. The Nusselt numbers in the three PHEs are all increased with the velocity, but the increasing rate is declined. BRM01has the best heat transfer performance because of its most compact geometry design, the largest plate angle65°nd smallest corrugation pitch7mm.(4) The fouling resistance is reduced with the increase of velocity, but the reduction rate reduces when velocity increases. So in the operation of PHE, an optimum velocity may exist. If the velocity is too small, the fouling resistance can be too large to have a good heat transfer performance. And the continued increasing of velocity will demand a high pumping cost while has little improvement in fouling performance. Re=2500is recommended according to this paper.