| At present, China is facing multiple pressures of environmental pollution, energy shortages, energy saving and emission reduction, energy supply has become a bottleneck to restrict China's economic development. So, how efficiently use energy and save energy as an important factor to ensure that the national economy develops ahead ceaselessly. As a thermal power device, plate heat exchangers have been widely used in the fields of petroleum, chemical, power, refrigeration and food processing etc. And then enhanced heat transfer, efficient and energy-save technologies, product applications had been paid a great deal of attention. The novel Plate Heat Exchangers (PHE) was proposed, in this paper, methods integrating theoretical analysis, numerical simulation and experiment are adapted to research heat transfer mechanism and performance of double chevron-type PHE.The mathematical model of full-channel is established in cylindrical coordinates based on some simplifications of actual PHE. Viscosity and thermal conductivity dependence on temperature of working fluid is considered. Fluid and solid coupling heat transfer in PHE is considered. RNG k-s turbulence model, Mesh refinement, Boundary layer mesh and general grid interface (GGI) technologies are considered. Through numerical studies in three different4-plate PHE, a fact that the corrugation's geometry parameters(corrugation ratio, corrugation depth, corrugation density and corrugation inclination angle) can markedly influence the performance of double chevron-type PHE has been found, the law of geometry parameters influence the performance has been found out; at the same times, fluid medium's flow pattern, velocity distribution, pressure distribution, the temperature distribution in channel of double chevron-type PHE, as well as, temperature distribution and heat flux distribution in heat transfer surface are discussed, respectively.Based on Field Synergy theory, relationships of synergy between velocity field, temperature field and pressure field in heat exchangers are considered. According to the analysis results of double chevron-type PHE between different corrugation inclination angles shows that double chevron-type PHE with30°corrugation inclination angle was best synergy.Based on Enransy Dissipation theory the factor of equipartition of entransy dissipation and the distribution ratio of entransy dissipation were defined, the factor of equipartition of entransy dissipation can be employed to evaluate entransy dissipation distribution, namely the total entransy dissipation reaches the minimum when the local entransy dissipation is uniformly distributed in the heat exchangers, the distribution ratio of entransy dissipation represents the ratio of entransy dissipation for heat transfer to entransy dissipation for viscous flow in heat exchangers. By numerical simulation results to the factor of equipartition of entransy dissipation and the distribution ratio of entransy dissipation, relationships between available energy loss, entransy dissipation and equipartition of entransy dissipation were found, namely the available energy loss is the minimum when the total entransy dissipation reaches the minimum as local entransy dissipation is uniformly distributed in the heat exchangers. In addition, entransy dissipation for viscous flow increases as Reynolds number.The experiment system of investigating the performance of double chevron-type PHE has been set up. The Heat transfer equations and flow resistance equations of characteristic number have been acquired by water to water and oil to water heat exchanging experiments investigating to double chevron-type PHE. Results show that comprehensive performance of double chevron-type PHE is much better than that of traditional chevron PHE. The numerical method was validated by experiment data.Finally, numerical analysis for the gas-liquid two phase flow is performed and law of inlet velocity and volume content of stream influence the performance have been found out.
|
PDF Full Text Request