Design Optimization Of ORC And Seawater Desalination System Driven By Industrial Waste Heat

With the increasing global concern on energy shortage and carbon emission,the recovery of sustainable energy from thermal processes has been widely concerned.Today,a number of available heat energy is wasted and cannot be recovered each year.At the same time,the emission of wasted heat often causes environmental harm.If waste heat energy can be used and reused effectively,it will contribute to achieving energy security,environmental sustainability and a low-carbon future.In industrial applications,a large number of the wastewater of high temperature will be produced,and discharged directly into the environment will emit a large amount of heat,resulting in heat island effect.The waste heat utilization of these high temperature wastewater is helpful to achieve the target of carbon emission and meet the requirements of energy conservation and emission reduction.In this study,the emphasis is on desalination technology paired with the organic Rankine cycle.For the organic Rankine cycle,since the cross-tube spray falling film evaporator is primarily employed in absorption refrigeration,vapor compression refrigeration,desalination,and other sectors,research has been published on its usage in power-generating systems.With R245fa as the working fluid,the heat transfer test platform of a cross-tube spray falling film evaporator for an ORC power production system was constructed.The effects of the initial temperature of geothermal water and its flow rate,spray density of the organic working fluid,and other variables on the heat transfer coefficient outside the tube were explored.It find that the heat transfer coefficient increases and subsequently declines with the growth of the initial temperature of geothermal water,its flow rate,and the spray density of the organic working fluid.Modifications are made to the parameters of the existing empirical equation of the out-of-tube heat transfer coefficient of the cross-tube sprayed falling film evaporator,and the experimental correlation equation of the out-of-tube evaporation heat transfer coefficient under the joint action of multiple factors is derived.Hollow fiber membrane tube banks（HFMTB）can be utilized in sweeping gas membrane distillation（SGMD）,the decrease in brine temperature reduces the transport of the heat and mass in the membrane module.A heating water tube incorporated within the hollow fiber membrane can effectively resolve the problem.This study develops internally-heated hollow fiber membrane tube banks（IHFMTB）.The IHFMTB consists of two tubes.The outer tube is a hydrophobic semi-permeable membrane that may simultaneously transmit moisture and heat,and the inner tube is permeable to heat.Based on boundary conditions of the conjugate transport,the equations heat and mass transfer conditions and governing momentum in the membrane,shell,and tube sides are established and resolved.The mean Nusselt numbers and Sherwood numbers,friction factors of the module are acquired and verified.Effects of the Reynolds numbers（Re）,the packing fraction（φ）,and the ratio of inner and outer radius(r_t,i/r_m,i)in membranes on conjugate transport are investigated.It can find that the ratio of the inner and outer radius(r_t,i/r_m,i)have prominent effects on the mean Nusselt numbers and Sherwood numbers for the brine stream,while the packing fraction（φ）has pronounced influences on those for the sweeping gas stream.Based on this,coupling two system models to obtain key factors such as coupled system power output and water production.The results showed that the coupled system using R123as the working fluid had the highest power output,while in the subsystem of seawater desalination,the larger the inner diameter ratio and the higher the Reynolds number of air and seawater,the more freshwater was produced.