太陽能噴射制冷系統(tǒng)冷凝器的特性研究及優(yōu)化
發(fā)布時間：2018-10-16 11:51
【摘要】：空調(diào)制冷技術(shù)的應(yīng)用給人類帶來了舒適的工作生活環(huán)境,同時也消耗了大量能源。太陽能噴射制冷系統(tǒng)憑借其具有節(jié)約能源、結(jié)構(gòu)簡單、使用壽命長以及系統(tǒng)運(yùn)行可靠、穩(wěn)定性高等優(yōu)勢而備受矚目。然而,現(xiàn)階段太陽能噴射制冷系統(tǒng)的效率較低,因此,提高系統(tǒng)效率對實(shí)現(xiàn)其廣泛應(yīng)用具有重要意義�，F(xiàn)有文獻(xiàn)中針對系統(tǒng)性能的提高進(jìn)行了制冷劑、噴射制冷系統(tǒng)結(jié)構(gòu)形式以及噴射器優(yōu)化等方面的研究,但缺乏通過優(yōu)化系統(tǒng)重要部件冷凝器來提高系統(tǒng)整體性能的研究。本文在研究冷凝器綜合性能的基礎(chǔ)上,運(yùn)用數(shù)值模擬的方法,通過合理設(shè)計(jì)冷凝器結(jié)構(gòu)以實(shí)現(xiàn)提高系統(tǒng)制冷量,優(yōu)化系統(tǒng)性能的目的。選取冷凝器殼程對流傳熱系數(shù)與壓降三分之一次方的比值與太陽能噴射制冷系統(tǒng)制冷量、性能系數(shù)COP作為冷凝器綜合性能與系統(tǒng)整體性能的評價指標(biāo),主要研究內(nèi)容及結(jié)論如下:1.根據(jù)系統(tǒng)數(shù)學(xué)模型及FORTRAN編制的噴射器結(jié)構(gòu)設(shè)計(jì)程序,在TRNSYS軟件中建立太陽能噴射制冷系統(tǒng),計(jì)算某氣象日運(yùn)行工況下,制冷系統(tǒng)各參數(shù)隨太陽輻射強(qiáng)度的變化情況。由TRNSYS軟件模擬結(jié)果可知,從11:00至18:00點(diǎn),噴射器結(jié)構(gòu)不變時,系統(tǒng)的一次流量隨時間變化的規(guī)律是先增大后減小,噴射系數(shù)隨時間則先減小后增大,這是由于在蒸發(fā)溫度和噴射器結(jié)構(gòu)參數(shù)一定時,發(fā)生溫度越高,臨界冷凝溫度越高,噴射系數(shù)越小。2.冷凝流量由一次流量與二次流量之和決定,系統(tǒng)運(yùn)行開始和結(jié)束時冷凝流量較小,15:00左右達(dá)到最大值,約為0.1801 skg/。計(jì)算得出的冷凝器換熱量30kW,運(yùn)用HTRI換熱器軟件設(shè)計(jì)管殼式冷凝器,并在FLUENT中建立冷凝器模型。3.將FLUENT模擬與TRNSYS軟件相結(jié)合進(jìn)行模擬,計(jì)算結(jié)果表明:當(dāng)冷凝器折流板間距取260mm,換熱管間距取32mm,折流板圓缺高度在0.2D-0.4D之間變化時,折流板圓缺高度增大,冷凝器殼程的對流傳熱系數(shù)與壓降的整體趨勢均減小。當(dāng)折流板圓缺高度取0.2D時,冷凝器的綜合性能與系統(tǒng)性能相對較好。4.當(dāng)冷凝器折流板圓缺高度取0.2D,換熱管間距取32mm,折流板間距取值在180mm-260mm之間變化時,折流板間距越小,冷凝器殼程的對流傳熱系數(shù)和壓降越大,當(dāng)折流板間距取180mm時,冷凝器的綜合性能與系統(tǒng)性能的表現(xiàn)均最佳。5.當(dāng)冷凝器圓缺高度為0.2D,折流板間距為180mm,換熱管中心距在30mm-34mm之間變化時,換熱管間距存在最優(yōu)值。當(dāng)取32mm或34 mm時,冷凝器的綜合性能較好,當(dāng)管間距取32mm時,系統(tǒng)性能最好。
[Abstract]:The application of air conditioning and refrigeration technology brings people a comfortable working and living environment, but also consumes a lot of energy. Solar ejector refrigeration system has attracted much attention because of its advantages of saving energy, simple structure, long service life, reliable operation and high stability. However, the efficiency of solar ejector refrigeration system is low at present, so it is very important to improve the efficiency of solar energy ejector refrigeration system to realize its wide application. In the existing literature, the refrigerant, the structure of the ejector refrigeration system and the optimization of the ejector are studied, but there is no research on how to improve the overall performance of the system by optimizing the condenser, an important part of the system. Based on the study of the comprehensive performance of the condenser, the purpose of improving the cooling capacity of the system and optimizing the performance of the system is achieved by using the method of numerical simulation and the reasonable design of the condenser structure. The ratio of convection heat transfer coefficient to the pressure drop of the condenser shell to the 1/3 power and the cooling capacity of the solar ejector refrigeration system are selected. The performance coefficient COP is used as the evaluation index of the condenser's comprehensive performance and the overall performance of the system. The main contents and conclusions are as follows: 1. According to the mathematical model of the system and the structural design program of the ejector compiled by FORTRAN, the solar ejector refrigeration system is established in the TRNSYS software, and the variation of the refrigeration system parameters with the solar radiation intensity is calculated under a meteorological daily operating condition. From the simulation results of TRNSYS software, it can be seen that from 11:00 to 18:00, when the ejector structure is invariant, the primary flow rate of the system increases first and then decreases, and the ejection coefficient decreases first and then increases with time. This is because the higher the evaporation temperature and the ejector structure parameter, the higher the critical condensation temperature and the smaller the ejection coefficient. The condensing flow is determined by the sum of primary flow and secondary flow. At the beginning and end of system operation, the condensing flow is small, reaching the maximum value about 15:00, about 0.1801 skg/.. The calculated heat transfer of condenser is 30kW, and the shell and tube condenser is designed by using HTRI heat exchanger software, and the model of condenser is established in FLUENT. By combining FLUENT simulation with TRNSYS software, the results show that when the condenser baffle spacing is 260mm and the heat transfer tube spacing is 32mm, the baffle circular gap height increases with the change of 0.2D-0.4D height. The overall trend of convection heat transfer coefficient and pressure drop in the condenser shell is decreased. When the height of baffle plate is 0.2D, the condenser's comprehensive performance and system performance are relatively good. 4. 4. When the circular gap height of condenser baffle plate is 0.2D, the distance of heat transfer tube is 32mm, and the distance of baffle plate is changed between 180mm-260mm, the smaller the baffle spacing is, the greater the convective heat transfer coefficient and pressure drop of condenser shell are. When the baffle spacing is taken as 180mm, the convection heat transfer coefficient and pressure drop of the condenser shell are increased. The comprehensive performance and system performance of condenser are the best. 5. 5. When the height of the condenser is 0.2D, the baffle spacing is 180mm, and the center distance of the heat transfer tube varies between 30mm-34mm, there is an optimum value of the heat transfer tube spacing. When 32mm or 34 mm is used, the condenser has better comprehensive performance, and when the tube spacing is 32mm, the system performance is the best.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU831
[Abstract]:The application of air conditioning and refrigeration technology brings people a comfortable working and living environment, but also consumes a lot of energy. Solar ejector refrigeration system has attracted much attention because of its advantages of saving energy, simple structure, long service life, reliable operation and high stability. However, the efficiency of solar ejector refrigeration system is low at present, so it is very important to improve the efficiency of solar energy ejector refrigeration system to realize its wide application. In the existing literature, the refrigerant, the structure of the ejector refrigeration system and the optimization of the ejector are studied, but there is no research on how to improve the overall performance of the system by optimizing the condenser, an important part of the system. Based on the study of the comprehensive performance of the condenser, the purpose of improving the cooling capacity of the system and optimizing the performance of the system is achieved by using the method of numerical simulation and the reasonable design of the condenser structure. The ratio of convection heat transfer coefficient to the pressure drop of the condenser shell to the 1/3 power and the cooling capacity of the solar ejector refrigeration system are selected. The performance coefficient COP is used as the evaluation index of the condenser's comprehensive performance and the overall performance of the system. The main contents and conclusions are as follows: 1. According to the mathematical model of the system and the structural design program of the ejector compiled by FORTRAN, the solar ejector refrigeration system is established in the TRNSYS software, and the variation of the refrigeration system parameters with the solar radiation intensity is calculated under a meteorological daily operating condition. From the simulation results of TRNSYS software, it can be seen that from 11:00 to 18:00, when the ejector structure is invariant, the primary flow rate of the system increases first and then decreases, and the ejection coefficient decreases first and then increases with time. This is because the higher the evaporation temperature and the ejector structure parameter, the higher the critical condensation temperature and the smaller the ejection coefficient. The condensing flow is determined by the sum of primary flow and secondary flow. At the beginning and end of system operation, the condensing flow is small, reaching the maximum value about 15:00, about 0.1801 skg/.. The calculated heat transfer of condenser is 30kW, and the shell and tube condenser is designed by using HTRI heat exchanger software, and the model of condenser is established in FLUENT. By combining FLUENT simulation with TRNSYS software, the results show that when the condenser baffle spacing is 260mm and the heat transfer tube spacing is 32mm, the baffle circular gap height increases with the change of 0.2D-0.4D height. The overall trend of convection heat transfer coefficient and pressure drop in the condenser shell is decreased. When the height of baffle plate is 0.2D, the condenser's comprehensive performance and system performance are relatively good. 4. 4. When the circular gap height of condenser baffle plate is 0.2D, the distance of heat transfer tube is 32mm, and the distance of baffle plate is changed between 180mm-260mm, the smaller the baffle spacing is, the greater the convective heat transfer coefficient and pressure drop of condenser shell are. When the baffle spacing is taken as 180mm, the convection heat transfer coefficient and pressure drop of the condenser shell are increased. The comprehensive performance and system performance of condenser are the best. 5. 5. When the height of the condenser is 0.2D, the baffle spacing is 180mm, and the center distance of the heat transfer tube varies between 30mm-34mm, there is an optimum value of the heat transfer tube spacing. When 32mm or 34 mm is used, the condenser has better comprehensive performance, and when the tube spacing is 32mm, the system performance is the best.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU831
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