Study On A Wide Flow Channel Plate Heat Exchanger With Low Flow Resistance And High Heat Transfer Performance

With China’s rapid economic development, energy demand increases every year. Traditional coal- fired boilers to produce not only the inevitable lot of smoke, haze and other air pollution caused, and to emit large quantities of greenhouse gases in the atmosphere, but does not match the level of heat, coal is a high- grade energy, combustion temperatures up to thousands o f degrees while building heating demand only need to maintain 18. Two belong to the low-grade reclaimed water can be environmentally friendly, a huge amount of water, contains a huge amount of energy to meet the heating needs.Heat pumps generally use direct and indirect extraction of recycled water to extract the heat, and in the direct extraction process due to the complexity of reclaimed water quality susceptible to corrosion heat pump units, long-term operation of the unit unfavorable; indirect extraction, currently running in the heat transfer coefficient is not widespread high, high dirt excessive growth or operating costs, did not follow the dirt run-growth characteristics. Though the sewage plant effluent reached the secondary effluent discharge standards, but the water intake is not very clean, such as water peak sewage treatment capacity exceeds wastewater treatment plant, as well as rain led to sewage soared, sewage plant will be taken directly to the overflow discharge measures in these cases of large-scale water utility emissions will increase. To make the system long-term operation, to protect the heat pump units, mainly indirect systems to study the regeneration of instability for this pollutant discharge water quality characteristics of plate heat exchangers in the form of wide flow channel structure, can effectively prevent the obstruction of occur, and achieve the purpose of high heat transfer through the structure optimization.Firstly, the topic for a wide flow channel plate heat exchanger modeling, numerical simulation using the computational fluid software FLUENT, using the average Nusselt number to measure the effect of heat transfer, verify the validity of the simulation results, using Reynolds separation fitting criteria related to heat equation and Euler equations.Secondly, by studying the growth of reclaimed water fouling characteristics of heat exchanger fouling Growth factors were analyzed, predictive model derived from the accumulation of dirt fouling resistance progressive growth equation, and fitting relations dirt thickness and flow rate, this can seek the dirt thermal resistance associated flow rates. From the principle of plate heat exchanger heat transfer and thermal calculation principles deduced the heat exchanger area calculation, logarithmic mean temperature difference, calculated the total heat transfer coefficient and flow resistance, combined with the gradual fouling resistance equations developed a recycled water exchange software, which have the capable of forecasting the fouling growth of heat exchanger.In the end, using numerical simulation to optimize the structure of the heat exchanger analysis, integrated heat transfer and flow characteristics of the flow channel spacing of 27 mm is better; the use of three indicators of the heat exchanger plate spacing affected different dirt evaluate growth characteristics, combined with the growth characteristics of fouling get the following conclusions: reclaimed water side of the optimum operating flow rate between 0.5~0.6m / s; by varying the evaporator outlet temperature, compared to the parameters shows that, when the evaporator outlet temperature is 8℃, the three indicators better.