【作者】 郭春生；

【导师】 程林；

【作者基本信息】 山东大学 ， 热能工程， 2012， 博士

【摘要】 目前中国正面临着环境污染、能源紧张和节能减排的多重压力,能源供应成为制约我国经济发展的瓶颈。因此如何有效的利用能源和节约能源成为保证国民经济不断向前发展的重要因素。板式换热器作为一种传热性能优越的热动力元件,广泛的应用于石油、化工、动力、制冷和食品加工等行业,因此研究强化传热技术、开发新型的、紧凑的、高效的板式换热器,提高板式换热器的换热性能,减少换热过程中的能量损失,具有十分重要的意义。本文提出了一种新型复合人字形板式换热器,采用理论分析、数值模拟及实验研究相结合的方式对其换热特性和阻力特性展开了研究。首先,依据一定假设对板式换热器进行简化,建立了完整流道的板式换热器模型,在考虑介质流体物性变化和流体与固体耦合换热的基础上,使用RNG k-ε湍流模型、换热面网格加密技术、边界层网格技术及GGI(general grid interface)网格链接技术,模拟分析了1-1程三流道板式换热器模型。通过对数值模拟结果的分析,得到了包括：大小波纹比例、波高、波纹密度及波纹倾斜角度在内几个重要几何参数对复合人字形板式换热器流动与传热特性的影响规律；同时讨论分析了复合人字形板式换热器流道内介质流动形态、速度分布、压力分布、和温度分布以及换热面的温度分布和热流分布情况。基于场协同原理,综合考虑速度场、温度场及压力场三场的协同性,分析了波纹倾斜角度对新型复合人字形板式换热器的协同性影响,结果显示：波纹倾角在30°-70°范围内,倾角为30。的复合人字形板式换热器三场协同性最佳。根据(?)耗散原理,定义了评价换热器性能的(?)耗散均匀性系数。火积耗散均匀性系数代表换热器内(?)耗散分布情况,当换热器内(?)耗散分布均分时,换热器总的(?)耗散最小；同时定义了(?)耗散的分配率,其代表换热器内由温差引起(?)耗散与由阻力引起(?)耗散之间的比例关系。复合人字形板式换热器的(?)耗散均匀性和(?)耗散分配率分析结果表明：在对流换热过程中(?)耗散与系统有用能损失存在对应关系,火积耗散最小意味着系统有用能损失最少；同时(?)散与系统(?)耗散均匀性也存在对应关系,系统(?)耗散越均匀意味其(?)耗散越小,即系统有用能损失最少。随着雷诺数的增加,在总的(?)耗散中,由阻力引起的(?)耗散比重逐渐增大。通过建立复合人字形板式换热器实验系统,对复合人字形板式换热器进行了水-水及油-水实验研究,得到了流体在这种换热器内的换热准则方程和流动特性方程。实验结果和数值模拟结果均表明：复合人字形板式换热器的综合性能与传统人字形板式换热器相比优势明显。最后,本文研究了复合人字形板式换热器内的气液两相流动与传热,给出了不同蒸汽入口速度和蒸汽入口体积含气量的影响规律。更多还原

【Abstract】 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.更多还原