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《制冷与空调(四川)》2018,(5)
为了提高喷射制冷系统的性能系数,建立了双热源驱动的带回热两级喷射制冷循环的理论计算模型。以纯工质R236fa为研究对象,讨论回热对单工质两级喷射制冷系统性能的影响,并与传统单级喷射系统性能进行比较。最后利用?分析比较传统单级系统和新型两级喷射系统的?损情况。研究结果表明,在相同工况下,当系统采用单工质时,加回热的系统性能更优,系统的性能系数可以提高约15%~20%,相对于传统的单级系统可以提高50%以上,其?效率相对传统单级喷射系统更具明显优势。 相似文献
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针对非共沸混合制冷工质单级压缩回热制冷循环,分析了LHR循环的特点及主要研究问题。根据非共沸混合制冷工质的特性,讨论并选取了适合于-70℃低温冷柜的混合制冷工质R23和R600a。利用制冷工质物性分析软件NIST Refprop 8.0初步研究了不同配比时制冷系统的特性,然后通过实验方法从不同角度分析混合制冷工质的配比对系统性能的影响,最终得到比较合理的混合制冷工质R23/R600a组分比例3:7。同时分析了该配比下制冷压缩机排气温度、压比、低温冷柜内温度等的变化特点,最后对蒸发器的温度变化特性和回热器的温度变化特性进行了总结。 相似文献
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分析常规蒸气压缩制冷系统存在的不足,介绍引射式减压原理,并将其技术应用于制冷(热泵)循环系统,提出新型压缩/喷射制冷循环系统。对改进后的新型制冷系统进行热力学分析,结合制冷工质R134a的制冷工况特性,得出改进后新型制冷系统的优越性能,即提高制冷系统的能量利用效率。对制冷和空调系统节能研究具有一定的指导意义。 相似文献
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提出一种新型水冷自复叠制冷循环方式,用冷凝分离器代替传统循环的冷凝器和相分离器,在冷凝分离器中同时完成了高沸点工质的冷凝及高沸点工质与低沸点工质的分离。对采用这种冷凝分离器的水冷自复叠制冷循环方式的R22/R23、R290/R170、R134a/R23、R134a/R170四种工质对进行了循环特性研究。在自行搭建的水冷自复叠制冷系统实验台上进行了R22/R23、R134a/R23两种工质对的实验研究。结果表明,在相同工况下,R22/R23自复叠制冷系统的COP要高于R134a/R23自复叠制冷系统;和传统的自复叠系统相比,采用冷凝分离器的水冷自复叠制冷循环COP明显提高,提升率达到60%~100%。 相似文献
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本文对低温级以CO2为工质的超市复叠式制冷系统进行了热力学理论分析,计算了不同蒸发温度、冷凝温度和不同传热温差下的COP,并与传统的超市复叠制冷循环进行对比分析。结果发现自然工质CO2/NH,复叠制冷系统的性能效率为最好,而R290/CO2复叠制冷系统的COP与使用传统工质的相当。因此,将自然环保工质复叠式制冷系统应用于小型超市具有很好的应用前景。 相似文献
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太阳能取之不竭,用之不尽,对坏境没有污染,是一种最有前途的能源。如今,人们正在考虑利用太阳能制冷,因为在夏季太阳能最丰富的时候,也是人们最需要空调制冷的时候。利用太阳能对房间进行温度调节,首先要解决如何用太阳能制冷的问题。目前,用太阳能制冷主要有三种方法:一是吸收式制冷,即利用太阳辐射热能驱动溴化锂水溶液或氨水溶液的吸收式制冷系统:二是利用太阳能加热通过集热器内的低沸点工质,经汽化后通入汽轮机驱动制冷机制冷.[第一段] 相似文献
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This paper presents a theoretical study of a combined thermal system, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces power and refrigeration simultaneously. The thermal system could use low temperature heat sources. A simulation was carried out to evaluate the cycle performance using several working fluids as R123, R141b, R245fa, R601a and R600a. A one-dimensional mathematical model of the ejector was developed using the equations governing the flow and thermodynamics based on the constant area ejector flow model. The ejector is studied in optimal operating regime. The influence of thermodynamic parameters on system performance is studied. The results show that the condenser temperature, the evaporation temperature, the extraction ratio, the fluid nature and the generating temperature have significant effects on the system performances (the coefficient of performance of the combined cycle and the entrainment ratio of the ejector). 相似文献
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船用喷射制冷机组可以有效利用船舶上低品位热能,实现能源的节约和高效利用。简述了喷射制冷的原理,进行了热力学分析,对船用蒸汽喷射制冷机组及余热回收式喷射制冷机组的研究及发展现状进行了分析,并对太阳能等新型喷射制冷机组船用化进行了展望。 相似文献
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There has been a demand for developments of the ejector refrigeration systems using low grade thermal energy, such as solar energy and waste heat. In this paper, a novel regenerative ejector refrigeration cycle was described, which uses an auxiliary jet pump and a conventional regenerator to enhance the performance of the novel cycle. The theoretical analysis on the performance characteristics was carried out for the novel cycle with the refrigerant R141b. Compared with the conventional cycle, the simulation results show that the coefficient of performance (COP) of the novel cycle increases, respectively, by from 9.3 to 12.1% when generating temperature is in a range of 80–160 °C, the condensing temperature is in a range of 35–45 °C and the evaporating temperature is fixed at 10 °C. Especially due to the enhanced regeneration with increasing the pump outlet pressure, the improvement of COP of the novel cycle is approached to 17.8% compared with that in the conventional cycle under the operating condition that generating temperature is 100 °C, condensing temperature is 40 °C and evaporating temperature is 10 °C. Therefore, the characteristics of the novel cycle performance show its promise in using low grade thermal energy for the ejector refrigeration system. 相似文献
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Passakorn Srisastra Satha Aphornratana Thanarath Sriveerakul 《International Journal of Refrigeration》2008,31(5):921-929
This paper proposed a workless-generator-feeding (WGF) system for a jet refrigeration cycle, using R141b. This feeding system does not require any mechanical power. The liquid refrigerant from the condenser was fed to the vapour-generator by means of the generator pressure and gravitational force. The system was tested and compared with a conventional system using a mechanical pump. It was found that this system was workable. The heat input to the generator was slightly higher than that for a system using a mechanical pump. The jet refrigeration cycle employing this new feeding system provided a slightly lower coefficient of performance (COP) compared to a system using a mechanical pump. However, this new system did not require any mechanical energy. Therefore, the jet refrigeration system employing this WGF system is truly a heat-power refrigeration cycle. 相似文献
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针对采用传统蒸气压缩制冷循环的冷藏冷冻箱的冷藏室换热温差大、有效能损失大的缺陷,提出了一种新的串联式双毛细管冷藏冷冻箱制冷循环。该循环系统是在常规的制冷循环的冷藏蒸发器和冷冻蒸发器之间增加一个毛细管,以提高冷藏蒸发温度,从而减少传热温差,进而降低冷藏室的有效能损失。利用PR方程计算制冷剂的热力学性质,编写了蒸气压缩制冷循环的有效能分析程序,分别对传统和新提出的冷藏冷冻箱制冷循环进行了计算。结果表明:传统冷藏冷冻箱制冷循环在制冷剂为R12、R134a时,有效能效率分别为21.20%、20.57%;双毛细管冷藏冷冻箱制冷循环在制冷剂为R12、R134a时,有效能效率分别为23.97%、23.44%;同比提高13.07%和13.95%。 相似文献
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In the proposed cogeneration cycle, a LiBr-H2O absorption refrigeration system is employed to the combined power and ejector refrigeration system which uses R141b as a working fluid. Estimates for irreversibilities of individual components of the cycle lead to possible measures for performance improvement. Results of exergy distribution of waste heat in the cycle show that around 53.6% of the total input exergy is destroyed due to irreversibilities in the components, 22.7% is available as a useful exergy output, and 23.7% is exhaust exergy lost to the environment, whereas energy distribution shows 44% is exhaust energy and 19.7% is useful energy output. Results also show that proposed cogeneration cycle yields much better thermal and exergy efficiencies than the previously investigated combined power and ejector cooling cycle. Current investigation clearly show that the second law analysis is quantitatively visualizes losses within a cycle and gives clear trends for optimization. 相似文献
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The combined power and cooling cycles driven by waste heat and renewable energy can provide different kinds of energy forms and achieve a higher thermodynamic efficiency. However, only a few researchers have focused on the improvement of temperature matching between the heat source and working fluid. This paper proposes a transcritical power and ejector refrigeration cycle (TPERC) to improve temperature matching between the heat source and working fluid. Based on the modelling of the TPERC system, a comparison of working fluids and the effects of system parameters on the cooling capacity, work output, thermal efficiency and exergy efficiency are discussed. The results show that of the seven working fluids selected, R1234ze has the largest thermal efficiency and exergy efficiency, principally due to having the highest critical temperature. At the identical turbine back pressure, condensing temperature and evaporation temperature, the turbine inlet temperature and its corresponding generation pressure have little impact on thermal efficiency. 相似文献