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A new model of a quantum refrigeration cycle composed of two adiabatic and
two isomagnetic field processes is established. The working substance in the
cycle consists of many non-interacting spin-1/2 systems. The performance of
the cycle is investigated, based on the quantum master equation and
semi-group approach. The general expressions of several important
performance parameters, such as the coefficient of performance, cooling
rate, and power input, are given. It is found that the coefficient of
performance of this cycle is in the closest analogy to that of the classical
Carnot cycle. Furthermore, at high temperatures the optimal relations of the
cooling rate and the maximum cooling rate are analysed in detail. Some
performance characteristic curves of the cycle are plotted, such as the
cooling rate versus the maximum ratio between high and low ``temperatures'
of the working substances, the maximum cooling rate versus the ratio between
high and low ``magnetic fields' and the ``temperature' ratio between high
and low reservoirs. The obtained results are further generalized and
discussed, so that they may be directly applied to describing the performance
of the quantum refrigerator using spin-$J$ systems as the working substance.
Finally, the optimum characteristics of the quantum Carnot and Ericsson
refrigeration cycles are derived by analogy. 相似文献
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An irreversible model of an Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas is established, which is
composed of two isothermal and two isobaric processes. The influence of both the quantum degeneracy and the finite-rate heat
transfer between the working fluid and the heat reservoirs on the performance of the cycle is investigated, based on the theory
of statistical mechanics and thermodynamic properties of an ideal Fermi gas. The inherent regeneration losses of the cycle
are analyzed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate
and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input.
The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient
of performance and power input are determined. Especially, the optimal performance of the cycle in the strong and weak gas
degeneracy cases and the high temperature limit is discussed in detail. The analytic expressions of some optimized parameters
are derived. Some optimum criteria are given. The distinctions and connections between the Ericsson refrigeration cycles working
with the Fermi and classical gases are revealed.
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热声制冷机作为一种新型制冷技术,具有效率高、可靠性好、环境友好等特点。目前,室温温区热声制冷机存在回热器声功利用量少、出口声功大、回收损失大等问题。本文基于SAGE软件,对室温温区热声制冷机的工作机理进行了研究。通过对两级及以上热声制冷机的制冷系数、制冷量以及进出口阻抗相角进行分析,探寻同时提高声功利用率和制冷量的方法。在分别以制冷系数和制冷量为优化计算目标的前提下,得到了室温温区多级热声制冷机的制冷量、制冷系数及声功利用率随级数变化的变化规律。计算结果显示,多级热声制冷机对出口声功的利用率存在最大值。可根据实际需求综合考虑制冷系数及制冷量,以得到较优的制冷工况。 相似文献
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《Heat Recovery Systems and CHP》1994,14(1):67-77
This communication presents a thermodynamic analysis and assessment of a Freon fluid Rankine cycle cooling system. The system consists of two subsystems—Rankine engine (RE) power cycle and a vapour compression (V-C) refrigeration cycle. The heat engine subsystem consists of a boiler, turbine, condenser and a feed pump while the cooling subsystem consists of a mechanical compressor, condenser, evaporator and an expansion valve. A number of working fluid combinations for the RE cycle and V-C cycle subsystems have been chosen on the basis of their thermodynamic properties and their suitability judged in terms of the performance parameters, namely, the thermal efficiency of the power cycle and the coefficient of performance (COP) of the refrigeration cycle. A regenerative heat exchanger (RHE) is incorporated in the RE cycle to improve the cycle efficiency and achieve energy conservation.The effects of various operation parameters, namely, component temperatures, adiabatic expansion/compression efficiencies and effectiveness of the RHE on the overall COP have been assessed. It is found that R114 + R22 give the best overall system performance and the presence of the RHE improves the system COP significantly. The effect of V-C cycle condenser temperature is more pronounced as compared to that of the RE cycle condenser and similarly the effect of evaporator temperature in the V-C cycle is more pronounced as compared to that of the boiler in the Rankine cycle subsystem. 相似文献
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The aim of the paper is to present the performance characteristics of a Stirling refrigeration cycle in micro/nano scale, in which the working substance of cycle is an ideal Maxwellian gas. Due to the quantum boundary effect on the gas particles confined in the finite domain, the cycle no longer possesses the condition of perfect regeneration. The inherent regenerative losses, the refrigeration heat and coefficient of performance (COP) of the cycle are derived. It is found that, for the micro/nano scaled Stirling refrigeration cycle devices, the refrigeration heat and COP of cycle all depend on the surface area of the system (boundary of cycle) besides the temperature of the heat reservoirs, the volume of system and other parameters, while for the macro scaled refrigeration cycle devices, the refrigeration heat and COP of cycle are independent of the surface area of the system. Variations of the refrigeration heat ratio rR and the COP ratio rε with the temperature ratio τ and volume ratio rV for the different surface area ratio rA are examined, which reveals the influence of the boundary of cycle on the performance of a micro/nano scaled Stirling refrigeration cycle. The results are useful for designing of a micro/nano scaled Stirling cycle device and may conduce to confirming experimentally the quantum boundary effect in the micro/nano scaled devices. 相似文献
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Experimental investigation of a thermoacoustic-Stirling refrigerator driven by a thermoacoustic-Stirling heat engine 总被引:1,自引:0,他引:1
In this paper, a thermally-driven thermoacoustic refrigerator system without any moving part is reported. This refrigeration system consists of a thermoacoustic-Stirling heat engine and a thermoacoustic-Stirling refrigerator; that is, the former is the driving source for the latter. Both the subsystems are designed to operate on traveling-wave mode. In the experiment, it was found that the DC-flows had significant negative effect on the heat engine and the refrigerator. To suppress these DC-flows, two flexible membranes were inserted into the two subsystems and worked very well. Then extensive experiments were made to test the influence of different parameters on refrigeration performance of the whole system. The system has so far achieved a no-load temperature of -65 degrees C, a cooling capacity of about 270 W at -20 degrees C and 405 W at 0 degrees C; in fact, the result showed a good prospect of the refrigeration system in room-temperature cooling such as food refrigeration and air-conditioning. 相似文献
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Slaton WV Raspet R Hickey CJ Hiller RA 《The Journal of the Acoustical Society of America》2002,112(4):1423-1430
The preceding paper [J. Acoust. Soc. Am. 112, 1414-1422 (2002)] derives the propagation equation for sound in an inert gas-condensing vapor mixture in a wet-walled pore with an imposed temperature gradient. In this paper the mass, enthalpy, heat, and work transport equations necessary to describe the steady-state operation of a wet-walled thermoacoustic refrigerator are derived and presented in a form suitable for numerical evaluation. The requirement that the refrigerator operate in the steady state imposes zero mass flux for each species through a cross section. This in turn leads to the evaluation of the mass flux of vapor in the system. The vapor transport and heat transport are shown to work in parallel to produce additional cooling power in the wet refrigerator. An idealized calculation of the coefficient of performance (COP) of a wet-walled thermoacoustic refrigerator is derived and evaluated for a refrigeration system. The results of this calculation indicate that the wet-walled system can improve the performance of thermoacoustic refrigerators. Several experimental and practical questions and problems that must be addressed before a practical device can be designed and tested are described. 相似文献
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以理想玻色气体为工质的量子Ericsson制冷循环 总被引:5,自引:1,他引:4
文中基于理想玻色气体的状态方程 ,分析了以理想玻色气体为工质的量子 Ericsson制冷循环中的回热特征 ,推导出其制冷循环的制冷系数表达式。并在高温和低温条件下对制冷系数进行了讨论。这将对低温气体制冷机的研究提供理论依据。 相似文献
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基于量子主方程和半群逼近方法,研究以许多无相互作用的自旋-1/2系统为工质的、由两个绝热和两个等磁场过程组成的不可逆量子制冷循环的一般性能特性。导出循环的性能系数、制冷率和输入功率等重要性能参数的表达式。应用数值求解,对受有限循环时间约束的制冷率进行了优化,计算了最大制冷率和相应的最佳性能参数,确定了性能系数的最佳区域和工质温度及两个等磁场过程时间的优化范围。进而详细分析了高温下循环的优化性能,所得结果被进一步推广,以致可直接用来描述由自旋-J系统为工质的量子制冷循环的性能。 相似文献
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Taking into account the finite-rate heat transfer in the heat-transfer processes, heat leak between the two external heat reservoirs, regenerative loss, regeneration time, and internal irreversibility due to dissipation of the cycle working substance, an irreversible magnetic Ericsson heat-pump cycle is presented. On the basis of the thermodynamic properties of magnetic materials, the performance characteristics of the irreversible magnetic Ericsson heat-pump are investigated and the relationship between the optimal heating load and the coefficient of performance (COP) is derived. Moreover, the maximum heating load and the corresponding COP as well as the maximum COP and the corresponding heating load are obtained. Furthermore, the other optimal performance characteristics are discussed in detail. The results obtained here may provide some new information for the optimal parameter design and the development of real magnetic Ericsson heat-pumps. 相似文献