低溫有機(jī)朗肯循環(huán)余熱回收系統(tǒng)的工質(zhì)優(yōu)選
發(fā)布時間：2019-06-26 21:46
【摘要】：有機(jī)朗肯循環(huán)(Organic Rankine Cycle)以低沸點有機(jī)物為系統(tǒng)循環(huán)工質(zhì),吸收低溫?zé)崮?推動膨脹機(jī)膨脹做功,其開發(fā)利用對提高能源利用率,減少環(huán)境污染具有重要意義。本文以熱力學(xué)定律為依據(jù),首先建立純工質(zhì)ORC系統(tǒng)模型,同時根據(jù)純工質(zhì)的選取原則,選取了R600、R601、異己烷、己烷、R601a、環(huán)己烷、庚烷、新戊烷、R123、R365mfc、R141b、R245ca、R245fa、苯十四種低沸點有機(jī)物作為系統(tǒng)工質(zhì),從熱力學(xué)特性和經(jīng)濟(jì)特性兩個方面,對純工質(zhì)ORC系統(tǒng)進(jìn)行研究,結(jié)果表明,大部分烷類工質(zhì)的熱效率和壓比相對其他類工質(zhì)較高,而所需質(zhì)量流量遠(yuǎn)小于其他類工質(zhì),且烷類工質(zhì)cyclohexane以其較高的熱效率、較低的單位功量質(zhì)量流量和UA等特性,被認(rèn)為是低品位余熱回收系統(tǒng)中較理想的循環(huán)工質(zhì)。其次,考慮到純工質(zhì)在換熱過程中的缺點,對混合工質(zhì)ORC系統(tǒng)進(jìn)行分析,文中選取了具有阻燃特性的HFC類工質(zhì)R245fa和循環(huán)性能較好的HC類工質(zhì)cyclohexane組成非共沸混合物,同時建立非共沸混合工質(zhì)ORC系統(tǒng)模型,以?損之比、系統(tǒng)熱效率、壓比、不可逆損失及UA等作為性能指標(biāo),從焓差與溫度之間的線性度、熱力學(xué)特性和經(jīng)濟(jì)特性三個方面對純工質(zhì)和混合工質(zhì)的性能進(jìn)行比較,結(jié)果表明,混合工質(zhì)的?損之比和斜率平方差較純工質(zhì)更小,焓差和溫度之間的線性度更好,換熱過程更接近理想換熱;大部分混合工質(zhì)的熱效率、系統(tǒng)凈功量均高于純工質(zhì),熱力學(xué)性能較優(yōu),但其UA和質(zhì)量流量也高于純工質(zhì),經(jīng)濟(jì)特性較純工質(zhì)稍弱。同時,混合工質(zhì)R245fa+cyclohexane(0.8,0.2)以其最低的?損之比和斜率平方差,最高的熱效率和系統(tǒng)凈功量,被認(rèn)為是較純工質(zhì)更適合煙氣余熱回收系統(tǒng)的循環(huán)工質(zhì)。
[Abstract]:The organic Rankine cycle (Organic Rankine Cycle) takes the low boiling point organic matter as the system circulation working fluid, absorbs the low temperature heat energy, promotes the expander to do the work, its development and utilization is of great significance to improve the energy utilization rate and reduce the environmental pollution. In this paper, based on the law of thermodynamics, the ORC system model of pure working fluid is established. At the same time, according to the selection principle of pure working fluid, the pure working fluid ORC system is studied from two aspects of thermodynamic and economic characteristics. The results show that the pure working fluid ORC system is studied from two aspects of thermodynamic and economic characteristics. The results show that R365mfc, R141b, R245ca, R245fa, benzene 14 kinds of low boiling point organic matter are used as working fluid in the system, and the pure working fluid ORC system is studied from two aspects of thermodynamic and economic characteristics. The thermal efficiency and pressure ratio of most alkane refrigerants are higher than those of other refrigerants, and the required mass flow rate is much lower than that of other refrigerants. Cyclohexane is considered to be an ideal circulating working fluid in low-grade waste heat recovery system because of its high thermal efficiency, low unit power mass flow rate and UA. Secondly, considering the shortcomings of pure working fluid in the heat transfer process, the mixed working fluid ORC system is analyzed. In this paper, the HFC working fluid R245fa with flame retardant property and the HC working fluid cyclohexane with good cycle performance are selected to form the non-azeotropic mixture. At the same time, the non-azeotropic mixed working fluid ORC system model is established. The ratio of loss, thermal efficiency, pressure ratio, irreversible loss and UA are used as performance indexes to compare the performance of pure working fluid and mixed working fluid from three aspects: linearity, thermodynamic and economic characteristics between enthalpy difference and temperature. The loss ratio and slope square difference are smaller than those of pure working fluid, the linearity between enthalpy difference and temperature is better, and the heat transfer process is closer to the ideal heat transfer process. The thermal efficiency of most mixtures is higher than that of pure working fluid, and the thermodynamic performance of the system is better, but its UA and mass flow rate are also higher than those of pure working fluid, and the economic characteristics are slightly weaker than those of pure working fluid. At the same time, the mixed working fluid R245fa cyclohexane (0.8, 0.2) is the lowest. The ratio of loss to slope square difference, the highest thermal efficiency and the net power of the system are considered to be more suitable for circulating working fluid of flue gas waste heat recovery system than pure working fluid.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TK115
[Abstract]:The organic Rankine cycle (Organic Rankine Cycle) takes the low boiling point organic matter as the system circulation working fluid, absorbs the low temperature heat energy, promotes the expander to do the work, its development and utilization is of great significance to improve the energy utilization rate and reduce the environmental pollution. In this paper, based on the law of thermodynamics, the ORC system model of pure working fluid is established. At the same time, according to the selection principle of pure working fluid, the pure working fluid ORC system is studied from two aspects of thermodynamic and economic characteristics. The results show that the pure working fluid ORC system is studied from two aspects of thermodynamic and economic characteristics. The results show that R365mfc, R141b, R245ca, R245fa, benzene 14 kinds of low boiling point organic matter are used as working fluid in the system, and the pure working fluid ORC system is studied from two aspects of thermodynamic and economic characteristics. The thermal efficiency and pressure ratio of most alkane refrigerants are higher than those of other refrigerants, and the required mass flow rate is much lower than that of other refrigerants. Cyclohexane is considered to be an ideal circulating working fluid in low-grade waste heat recovery system because of its high thermal efficiency, low unit power mass flow rate and UA. Secondly, considering the shortcomings of pure working fluid in the heat transfer process, the mixed working fluid ORC system is analyzed. In this paper, the HFC working fluid R245fa with flame retardant property and the HC working fluid cyclohexane with good cycle performance are selected to form the non-azeotropic mixture. At the same time, the non-azeotropic mixed working fluid ORC system model is established. The ratio of loss, thermal efficiency, pressure ratio, irreversible loss and UA are used as performance indexes to compare the performance of pure working fluid and mixed working fluid from three aspects: linearity, thermodynamic and economic characteristics between enthalpy difference and temperature. The loss ratio and slope square difference are smaller than those of pure working fluid, the linearity between enthalpy difference and temperature is better, and the heat transfer process is closer to the ideal heat transfer process. The thermal efficiency of most mixtures is higher than that of pure working fluid, and the thermodynamic performance of the system is better, but its UA and mass flow rate are also higher than those of pure working fluid, and the economic characteristics are slightly weaker than those of pure working fluid. At the same time, the mixed working fluid R245fa cyclohexane (0.8, 0.2) is the lowest. The ratio of loss to slope square difference, the highest thermal efficiency and the net power of the system are considered to be more suitable for circulating working fluid of flue gas waste heat recovery system than pure working fluid.
【學(xué)位授予單位】：華北電力大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TK115
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