蒸气喷射准双级压缩制冷系统的实验研究
发布时间：2019-01-22 18:08
【摘要】：在蒸气压缩式制冷循环中,确定制冷工质后,系统的蒸发压力和冷凝压力分别由蒸发温度和冷凝温度决定。蒸发温度由系统的功能所决定,而冷凝温度受环境介质限制。当蒸发温度降低时,压缩机的压缩比增大,由于压缩机存在余隙容积,根据相关理论求解公式可以看出,随着压缩比的增大,压缩机的余隙容积逐渐减小,当压缩比增加到某一数值后使得余隙容积降为零,此时,压缩机便不再吸气,制冷量也随之降为零。而本文利用喷射器提高引射流体的压力而不直接消耗机械能的特点,将其引入到单级蒸气压缩式制冷系统中,搭建蒸气喷射准双级制冷系统实验台,并研究系统性能。喷射器利用压缩机的排气作为动力,引射蒸发器出口的制冷工质,提高其压力后送入压缩机吸气口,不仅降低了压缩比,使系统获得更低的蒸发温度,而且没有其余的机械能消耗。喷射器是蒸气喷射准双级压缩制冷系统的重要部件,本文用动力函数法计算得到喷射器的基本尺寸,并在实验中探究其进出口状态参数变化对喷射系数以及系统性能的影响。此外,文中对压缩机、蒸发器、冷凝器、膨胀阀及气体喷射器建立数学模型,利用MATLAB语言编制相关计算程序,理论模拟系统性能。搭建实验台,此实验台可以通过阀门的开关实现单级蒸气压缩式制冷循环与蒸气喷射准双级压缩制冷循环的两种运行方式,并在不同工况下对系统制冷量及系统性能的变化进行实验研究。本文通过对蒸气喷射准双级制冷系统和传统单级蒸气压缩制冷系统的实验对比得出:蒸气喷射准双级制冷系统可以获得比单级蒸气压缩制冷系统更低的蒸发温度,并且在较低的蒸发温度下,蒸气喷射准双级制冷系统性能优于单级蒸气压缩制冷系统;实验数据显示,当蒸发温度降低到-22.57℃时(Tk=303.15K),蒸气喷射准双级制冷系统的COP开始优于单级蒸气压缩制冷系统;当蒸发温度到-31.43℃时(Tk=308.15K),单级蒸气压缩式制冷系统将不再产生冷量,这是由于随着压比的不断增大,压缩机容积系数变为零,压缩机吸气量随之变为零,虽然制冷系统仍在不断运行,但其制冷量却为零,而本课题中测得蒸气喷射准双级制冷系统可达到的最低蒸发温度为-36.52℃。对气体喷射器进行实验研究,探究其进出口参数的变化对喷射器喷射系数及系统性能、制冷量的影响。首先分析了喷射器出口流体压力变化对喷射系数和系统性能及制冷量的影响。实验数据显示:随着混合流体出口压力的增加,喷射系数逐渐降低,系统制冷量也呈下降趋势,但系统COP随着混合出口流体压力的变化曲线为二次曲线,当喷射器进口流体压力为880KPa时,混合流体出口压力在220KPa~240KPa时系统COP较好;其次分析了工作流体对喷射系数及系统的影响。实验数据显示:当工作流体的压力逐渐增加时,喷射系数及系统COP、制冷量均呈现先增加后降低的趋势,在本文实验条件下,当工作流体的压力为900KPa~930KPa时,系统COP较好;另外对喷射器引射流体的压力与喷射系数及系统COP、制冷量间的关系进行分析。分析实验数据可得:当引射流体的压力增加时,喷射系数呈上升趋势,随着喷射系数的逐渐增加,蒸气喷射准双级制冷系制冷量呈现相同的变化趋势,但引射流体压力与系统COP的变化曲线为二次曲线,当引射流体的压力为130KPa~150KPa时,系统COP较好。
[Abstract]:In the vapor compression refrigeration cycle, the evaporation pressure and the condensation pressure of the system are determined by the evaporation temperature and the condensation temperature after the refrigeration working medium is determined. The evaporation temperature is determined by the function of the system, and the condensation temperature is limited by the ambient medium. when the evaporation temperature is reduced, the compression ratio of the compressor is increased, At this time, the compressor no longer inhales, and the cooling capacity also drops to zero. In this paper, the injector is used to improve the pressure of the injection fluid without directly consuming the mechanical energy. It is introduced into a single-stage vapor compression refrigeration system, and the experimental table of the vapor-injection quasi-dual-stage refrigeration system is set up, and the performance of the system is also studied. the ejector uses the exhaust of the compressor as the power to draw the refrigerant working medium at the outlet of the evaporator, and the pressure is increased to the suction port of the compressor, so that the compression ratio is reduced, the system can obtain lower evaporation temperature, and the rest of the mechanical energy is not consumed. The ejector is an important part of the vapor injection quasi-double-stage compression refrigeration system. The basic dimensions of the ejector are calculated by the power function method, and the effect of the change of the inlet and outlet state parameters on the injection coefficient and the system performance is investigated in the experiment. In addition, a mathematical model is established for compressor, evaporator, condenser, expansion valve and gas ejector, and the relevant calculation program and theoretical simulation system performance are prepared by using MATLAB language. The experiment table can be set up. The experiment table can realize the two modes of the single-stage vapor compression refrigeration cycle and the vapor injection quasi-double stage compression refrigeration cycle through the switch of the valve, and carry out the experimental research on the system cooling capacity and the system performance under different working conditions. by comparing the experimental results of a vapor-jet quasi-dual-stage refrigeration system and a conventional single-stage vapor compression refrigeration system, the vapor-jet quasi-dual-stage refrigeration system can achieve a lower evaporation temperature than a single-stage vapor compression refrigeration system and, at a lower evaporation temperature, The performance of the vapor-jet quasi-dual-stage refrigeration system is better than that of a single-stage vapor compression refrigeration system, and the experimental data show that the COP of the vapor-injection quasi-dual-stage refrigeration system is better than the single-stage vapor compression refrigeration system when the evaporation temperature is reduced to-22.57 DEG C (Tk = 303.15K). when the evaporation temperature is at-31.43. degree. C. (Tk = 308. 15K), the single-stage vapor compression refrigeration system will no longer generate a cold amount, because the compressor volume coefficient becomes zero as the pressure ratio increases, and the compressor suction amount becomes zero, although the refrigeration system is still running continuously, but the refrigerating capacity is zero, and the minimum evaporation temperature of the vapor injection quasi-double-stage refrigeration system measured in the subject is-36.52 DEG C. The effect of the change of the inlet and outlet parameters on the injection coefficient and the system performance and the cooling capacity of the ejector was investigated. The effect of the change of the fluid pressure on the injection coefficient and the system performance and the cooling capacity is analyzed. The experimental data show that, with the increase of the outlet pressure of the mixed fluid, the injection coefficient is gradually reduced, and the cooling capacity of the system is also decreasing, but the system COP is a quadratic curve with the change curve of the fluid pressure of the mixed outlet, and when the inlet fluid pressure of the ejector is 880KPa, The system COP is better when the outlet pressure of the mixed fluid is 220KPa-240KPa, and the effect of the working fluid on the injection coefficient and the system is also analyzed. The experimental data show that, when the pressure of working fluid is gradually increased, the injection coefficient and system COP and refrigerating capacity show a tendency to decrease, and under the experimental conditions of this paper, the system COP is better when the pressure of working fluid is 900KPa-930KPa. In addition, the relationship between the pressure and the injection coefficient and the system COP and the cooling capacity of the ejector fluid is analyzed. The experimental data can be obtained: when the pressure of the injection fluid is increased, the injection coefficient is on the rise, and with the gradual increase of the injection coefficient, the cooling capacity of the vapor injection quasi-dual-stage refrigeration system exhibits the same variation trend, but the change curve of the injection fluid pressure and the system COP is a quadratic curve, When the pressure of the injection fluid is 130KPa-150KPa, the system COP is better.
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB657
本文编号：2413437
[Abstract]:In the vapor compression refrigeration cycle, the evaporation pressure and the condensation pressure of the system are determined by the evaporation temperature and the condensation temperature after the refrigeration working medium is determined. The evaporation temperature is determined by the function of the system, and the condensation temperature is limited by the ambient medium. when the evaporation temperature is reduced, the compression ratio of the compressor is increased, At this time, the compressor no longer inhales, and the cooling capacity also drops to zero. In this paper, the injector is used to improve the pressure of the injection fluid without directly consuming the mechanical energy. It is introduced into a single-stage vapor compression refrigeration system, and the experimental table of the vapor-injection quasi-dual-stage refrigeration system is set up, and the performance of the system is also studied. the ejector uses the exhaust of the compressor as the power to draw the refrigerant working medium at the outlet of the evaporator, and the pressure is increased to the suction port of the compressor, so that the compression ratio is reduced, the system can obtain lower evaporation temperature, and the rest of the mechanical energy is not consumed. The ejector is an important part of the vapor injection quasi-double-stage compression refrigeration system. The basic dimensions of the ejector are calculated by the power function method, and the effect of the change of the inlet and outlet state parameters on the injection coefficient and the system performance is investigated in the experiment. In addition, a mathematical model is established for compressor, evaporator, condenser, expansion valve and gas ejector, and the relevant calculation program and theoretical simulation system performance are prepared by using MATLAB language. The experiment table can be set up. The experiment table can realize the two modes of the single-stage vapor compression refrigeration cycle and the vapor injection quasi-double stage compression refrigeration cycle through the switch of the valve, and carry out the experimental research on the system cooling capacity and the system performance under different working conditions. by comparing the experimental results of a vapor-jet quasi-dual-stage refrigeration system and a conventional single-stage vapor compression refrigeration system, the vapor-jet quasi-dual-stage refrigeration system can achieve a lower evaporation temperature than a single-stage vapor compression refrigeration system and, at a lower evaporation temperature, The performance of the vapor-jet quasi-dual-stage refrigeration system is better than that of a single-stage vapor compression refrigeration system, and the experimental data show that the COP of the vapor-injection quasi-dual-stage refrigeration system is better than the single-stage vapor compression refrigeration system when the evaporation temperature is reduced to-22.57 DEG C (Tk = 303.15K). when the evaporation temperature is at-31.43. degree. C. (Tk = 308. 15K), the single-stage vapor compression refrigeration system will no longer generate a cold amount, because the compressor volume coefficient becomes zero as the pressure ratio increases, and the compressor suction amount becomes zero, although the refrigeration system is still running continuously, but the refrigerating capacity is zero, and the minimum evaporation temperature of the vapor injection quasi-double-stage refrigeration system measured in the subject is-36.52 DEG C. The effect of the change of the inlet and outlet parameters on the injection coefficient and the system performance and the cooling capacity of the ejector was investigated. The effect of the change of the fluid pressure on the injection coefficient and the system performance and the cooling capacity is analyzed. The experimental data show that, with the increase of the outlet pressure of the mixed fluid, the injection coefficient is gradually reduced, and the cooling capacity of the system is also decreasing, but the system COP is a quadratic curve with the change curve of the fluid pressure of the mixed outlet, and when the inlet fluid pressure of the ejector is 880KPa, The system COP is better when the outlet pressure of the mixed fluid is 220KPa-240KPa, and the effect of the working fluid on the injection coefficient and the system is also analyzed. The experimental data show that, when the pressure of working fluid is gradually increased, the injection coefficient and system COP and refrigerating capacity show a tendency to decrease, and under the experimental conditions of this paper, the system COP is better when the pressure of working fluid is 900KPa-930KPa. In addition, the relationship between the pressure and the injection coefficient and the system COP and the cooling capacity of the ejector fluid is analyzed. The experimental data can be obtained: when the pressure of the injection fluid is increased, the injection coefficient is on the rise, and with the gradual increase of the injection coefficient, the cooling capacity of the vapor injection quasi-dual-stage refrigeration system exhibits the same variation trend, but the change curve of the injection fluid pressure and the system COP is a quadratic curve, When the pressure of the injection fluid is 130KPa-150KPa, the system COP is better.
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB657
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