不可逆费米奥托制冷循环性能分析

基于回热式不可逆奥托制冷循环和理想费米气体的状态方程,导出以费米气体为工质的奥托制冷循环的输入功、制冷量、制冷系数等重要性能参数的表达式,以此讨论费米气体的量子简并性、回热及内不可逆性对循环性能的影响,给出以理想费米气体为工质的回热式不可逆奥托制冷循环的性能特征。所得结果有助于进一步了解经典气体奥托制冷循环与量子气体奥托制冷循环的区别和联系。     

Ecological optimization for an irreversible magnetic Ericsson refrigeration cycle

An irreversible Ericsson refrigeration cycle model is established, in which multi-irreversibilities such as finite-rate heat transfer, regenerative loss, heat leakage, and the efficiency of the regenerator are taken into account. Expressions for several important performance parameters, such as the cooling rate, coefficient of performance （COP）, power input, exergy output rate, entropy generation rate, and ecological function are derived. The influences of the heat leakage and the time of the regenerative processes on the ecological performance of the refrigerator are analyzed. The optimal regions of the ecological function, cooling rate, and COP are determined and evaluated. Furthermore, some important parameter relations of the refrigerator are revealed and discussed in detail. The results obtained here have general significance and will be helpful in gaining a deep understanding of the magnetic Ericsson refrigeration cycle.     

不可逆自旋量子制冷循环参数的优化设计

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。     

Performance of an irreversible quantum refrigeration cycle

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.     

玻色气体的量子简并性对不可逆布雷顿制冷循环性能的影响

基于不可逆布雷顿制冷循环模型和理想玻色气体的状态方程,导出以玻色气体为工质的布雷顿制冷循环的输入功、制冷系数、制冷量等重要参数的表示式,由此讨论玻色气体的量子简并性和不可逆绝热过程对循环性能的影响,揭示以玻色气体为工质的不可逆布雷顿制冷循环的一般性能特性,从而导出一些重要结论．进而给出几种特殊情况下循环的性能特性．得到的结果有助于进一步了解经典布雷顿制冷循环和量子布雷顿制冷循环之间的区别和联系．     

以理想玻色气体为工质的量子Ericsson制冷循环

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。     

The performance analysis of a micro-/nanoscaled quantum heat engine

A new model of micro-/nanoscaled heat engines consisting of two thin long tubes with the same length but different sizes of cross section, which are filled up with ideal quantum gases and operated between two heat reservoirs, is put forward. The working fluid of the heat engine cycle goes through four processes, which include two isothermal processes and two isobaric processes with constant longitudinal pressure. General expressions for the power output and efficiency of the cycle are derived, based on the thermodynamic properties of confined ideal quantum gases. The influence of the size effect on the power output and efficiency is discussed. The differences between the heat engines working with the ideal Bose gas and Fermi gas are revealed. The performance of the heat engines operating at weak gas degeneracy and high temperatures is further analyzed. The results obtained are more general and significant than those in the current literature.     

谐振子量子制冷循环

本文基于量子主方程和半群方法,分析了以谐振子系统为工质的量子制冷循环中的回热特征及时间演化公式,推导出制冷系数、制冷率和输入功率的一般表达式,在高温极限下详细推导出它们的具体优化特征.这里所获得的结论可以与经典制冷循环的结论进行比较,发现有许多类似之处.     

The performance characteristics of an irreversible quantum Otto harmonic refrigeration cycle

In this paper, an irreversible quantum Otto refrigeration cycle working with harmonic systems is established. Base on Heisenberg quantum master equation, the equations of motion for the set of harmonic systems thermodynamic observables are derived. The simulated diagrams of the quantum Otto refrigeration cycle are plotted. The relationship between average power of friction, cooling rate, power input, and the time of adiabatic process is analyzed by using numerical calculation. Moreover, the influence of the heat conductance and the time of iso-frequency process on the performance of the cycle is discussed.     

实际回热式布雷顿制冷机的性能优化

用有限时间热力学方法分析实际回热式布雷顿制冷机的性能特性,以制冷率和制冷系数为优化目标,优化了高低、温侧换热器和回热器的热导率分配以及工质和热源间的热容率匹配,并采用数值计算分析了各参数值对最优性能的影响特点.所得结果对工程制冷系统设计有一定的指导意义。     

Performance characteristics and parametric optimization of an irreversible magnetic Ericsson heat-pump

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.     

量子简并性对气体斯特林制冷循环性能的影响

基于理想量子气体的状态方程，分析了量子气体斯特林制冷循环中的回热特征，推导出循环的制冷系数一般表达式.获得了在强简并和弱简并条件下循环的制冷系数，对全面理解气体斯特林制冷机的性能有所帮助. 关键词： 量子简并性 斯特林制冷循环     

耦合高压斯特林制冷效应的复合磁制冷循环的数值模拟

本文借助计算流体力学软件, 对复合磁制冷机进行整机数值模拟分析. 以复合磁制冷机为建模原形, 分别计算了主动式磁制冷循环以及复合磁制冷循环. 利用模型计算分析了利用系数, 工作频率对主动式磁制冷的制冷效果影响, 同时模拟计算了不同相位角、不同频率下的复合磁制冷机的制冷效果, 计算得到适合复合磁制冷循环的最佳匹配相位角. 模拟计算结果对后续实验台的设计搭建有很好的指导作用.     

Performance Analysis and Optimization for Irreversible Combined Carnot Heat Engine Working with Ideal Quantum Gases

An irreversible combined Carnot cycle model using ideal quantum gases as a working medium was studied by using finite-time thermodynamics. The combined cycle consisted of two Carnot sub-cycles in a cascade mode. Considering thermal resistance, internal irreversibility, and heat leakage losses, the power output and thermal efficiency of the irreversible combined Carnot cycle were derived by utilizing the quantum gas state equation. The temperature effect of the working medium on power output and thermal efficiency is analyzed by numerical method, the optimal relationship between power output and thermal efficiency is solved by the Euler-Lagrange equation, and the effects of different working mediums on the optimal power and thermal efficiency performance are also focused. The results show that there is a set of working medium temperatures that makes the power output of the combined cycle be maximum. When there is no heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are parabolic-like ones, and the internal irreversibility makes both power output and efficiency decrease. When there is heat leakage loss in the combined cycle, all the characteristic curves of optimal power versus thermal efficiency are loop-shaped ones, and the heat leakage loss only affects the thermal efficiency of the combined Carnot cycle. Comparing the power output of combined heat engines with four types of working mediums, the two-stage combined Carnot cycle using ideal Fermi-Bose gas as working medium obtains the highest power output.     

Thermal modelling and energy conservation studies on freon rankine cycle cooling system with regenerative heat exchanger

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.     

Performance characteristic of a Stirling refrigeration cycle in micro/nano scale

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 r_R and the COP ratio r_ε with the temperature ratio τ and volume ratio r_V for the different surface area ratio r_A 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.     

二级不可逆磁Brayton制冷循环性能分析及参数优化

建立受有限速率热传导和绝热过程不可逆性影响的二级磁Brayton制冷循环模型,导出循环的性能系数和制冷率表达式,分析等磁场过程的磁场比、绝热不可逆因子、等磁中冷过程等对二级不可逆磁Brayton制冷循环最大制冷率及相关参数的影响,所得结论能为提高磁制冷机的循环性能提供参数设计参考.     

The performance evaluation of a micro/nano-scaled cooler working with an ideal Bose gas

Based on the size effect of a confined ideal Bose gas, the design concept of a quantum cooler is originally put forward. The cooler consists of two long tubes with the same length but different sizes of cross section, which are filled up with the ideal Bose gas, and is operated between two heat reservoirs. Expressions for the refrigeration rate and coefficient of performance (COP) of the cooler are derived. The effects of the size effect on the refrigeration rate and COP are discussed. The general performance characteristics of the cooler are revealed.     

Einstein制冷循环气泡泵的性能研究

基于Einstein制冷循环设计了气泡泵实验装置,以氨水为工质,对给定工况下气泡泵的性能进行研究。对沉浸比和加热功率对气泡泵的提升性能的影响进行分析,并将实验值与理论模型进行比较。结果表明:气泡泵的液体输送特性与气泡泵提升管管径、沉浸比、加热功率有关;气泡泵的液体流量随着加热功率增大、沉浸比的增大而增大,提升管内径对液体流量的影响不明显。实验结果与理论模型分析结果相一致。     

热漏、热阻及回热特性对磁Ericsson制冷循环最优性能的影响

建立了同时考虑热漏、热阻及回热等主要不可逆因素的顺磁质 Ericsson制冷循环的模型。针对回热平衡与回热不平衡的情况 ,应用有限时间热力学理论 ,导出了制冷率与制冷系数间的基本优化关系 ,给出了制冷率、制冷系数的优化值域 ,结果反映了回热式制冷机的主要观测特征。讨论了基本优化关系的应用 ,分析了热漏、热阻及回热损失对制冷循环性能影响的本质差异