微型压缩机驱动的单级与自复叠耦合系统的实验研究

搭建了微型压缩机驱动的单级与自复叠耦合系统的实验台,以单级制冷系统对自复叠系统进行预冷的方式获得更低的蒸发温度。高温级工质选用R404A,低温级工质选用R290/R170/R14组成的混合工质(充注质量比为0.33/0.17/0.50),在25℃环境温度,获得了系统的运行特性以及环境温度和高温级预冷温度对系统性能的影响。研究表明:在157 min的降温时间内,蒸发器进口温度达到-112℃,出口温度达到-111℃并保持稳定;环境温度从15℃升高到32℃,系统所能达到的最低温度由-116.68℃升高到-95.31℃;高温级预冷温度从-27℃降低到-37℃,系统蒸发器进口温度由-91.18℃降低到-112.7℃。     

基于遗传算法三级自动复叠制冷系统建模分析和优化

为了优化混合工质配比,提高系统性能,采用Aspen Plus来模拟自动复叠制冷系统,将遗传算法与混合工质的配比选取结合,以系统热力学完善度最高为目标函数进行优化,得出了不同蒸发器出口温度、冷凝器出口温度、压缩机压比时系统性能最优时混合工质的质量配比,为实际自动复叠制冷系统设计和制冷剂充注提供了理论数据。将一组三级自动复叠制冷系统的实验值与模拟值进行对比,发现模拟值与实验值的误差多数都在10%以内。     

微型压缩机驱动的单级与自复耦合系统的实验研究

搭建了微型压缩机驱动的单级与自复叠耦合系统的实验台,以单级制冷系统对自复叠系统进行预冷的方式获得更低的蒸发温度。高温级工质选用R404A,低温级工质选用R290/R170/R14组成的混合工质(充注质量比为0.33/0.17/0.50),在25 ℃环境温度,获得了系统的运行特性以及环境温度和高温级预冷温度对系统性能的影响。研究表明:在157 min的降温时间内,蒸发器进口温度达到-112 ℃,出口温度达到-111 ℃并保持稳定;环境温度从15 ℃升高到32 ℃,系统所能达到的最低温度由-116.68 ℃升高到-95.31 ℃;高温级预冷温度从-27 ℃降低到-37 ℃,系统蒸发器进口温度由-91.18 ℃降低到-112.7 ℃。     

-150℃四级自复叠制冷系统的实验与分析

搭建了一种四级自复叠制冷系统,采用由R600a、R134a、R23、R14、R50和R740等6种工质组成的非共沸混合制冷剂,经过调试与实验,成功得到了-150℃的柜内温度。讨论了该低温箱体的降温特性、压缩机的运行特性和混合工质的节流特性。研究表明,压缩机的吸、排气压力和温度关乎系统能否安全稳定的运行,每级毛细管的长度关乎系统的降温特性。     

混合工质组分对ORC系统性能影响实验研究

针对低品位热能的特点,利用搭建的有机物朗肯循环(ORC)系统实验装置,对采用不同组分混合工质R600a/R601a的ORC系统性能进行实验研究,获得系统和部件特性随组分的变化规律。实验结果表明:随着混合工质中的R600a组分的增大膨胀比减小,下降幅度为38.4%,涡旋膨胀机效率受R600a组分变化的影响较小,在60%附近上下波动;净发电功率、工质吸热量和蒸发过程温度滑移量都随着R600a组分的增大先增大后减小,在R600a组分为0.4处,混合工质具有最大的净发电功率、吸热量和温度滑移量,净输出功率比纯R601a高出25%。这说明非等温相变特性可以使混合工质的吸热过程更好地与热源流体的放热过程相匹配,从而提高热能利用率,增加发电功率。     

太阳能复叠喷射冷热双蓄系统性能优化潜力研究

针对太阳能R290/CO₂复叠喷射冷热双蓄系统,通过先进?分析方法研究系统部件间的相互作用以及优化潜力,探讨喷射器效率以及中间换热器CO₂侧压力对系统性能的影响规律。先进?分析结果发现R290喷射器的可避免内源损最大,其具有最高的改进潜力,系统?损中88.90%为内源?损、41.68%为可避免?损。通过提高喷射器效率可有效改善整个系统的?效率。同时系统中存在最佳的中间换热器CO₂侧压力,可使系统?效率达到最高,从而使得R290喷射器的可避免内源?损最小。     

混合工质用于地热热泵系统的实验研究

针对以40℃－45℃地热尾水为低温热源的热泵系统,进行了大量的实验研究,首先,在该系统中采用了循环性能较好的低环害混合工质,以达到实际运行和环保要求,其次,根据不同的冷凝器水流量和凝器的进口水温,总结得出了大量稳定工况实际样本,并绘制了不同水流量和水温下的EER（能效比）值曲面,为热泵在实际工程应用中的变工况调节运行的智能化提供了参考数据。     

双效复叠吸附式制冷循环的研究

为克服吸附式制冷能量利用效率不高的缺点，采用硅胶－水、分子筛－水分别作为两级循环的工作对以及两级循环中都用分子筛－水为工作对，构造了两种双效复叠式制冷循环．该循环可有效利用第二级循环的吸附热、析出蒸汽的显热，能有效提高热力完善度。建立了计算机模型，对系统和影响性能的一些参数进行了分析讨论。     

双效复叠吸附式制冷循环的研究

为克服吸附式制冷能量利用效率不高的缺点,采用硅胶-水、分子筛-水分别作为两级循环的工作对以及两级循环中都用分子筛-水为工作对,构造了两种双效复叠式制冷循环.该循环可有效利用第二级循环的吸附热、析出蒸汽的显热,能有效提高热力完善度.建立了计算机模型,对系统和影响性能的一些参数进行了分析讨论.     

Experimental investigations on ejector refrigeration system with ammonia

A vapor ejector refrigeration system has been designed and developed to operate with ammonia. In this paper, performance of ejector refrigeration system has been experimentally studied with three different area ratio ejectors by varying operational parameters namely generator, condenser and evaporator temperatures. Effect of non-dimensional parameters like compression ratio, expansion ratio and area ratio on the system performance is studied. Entrainment ratio and coefficient of performance of the system increase with increase in ejector area ratio and expansion ratio and they increase with decrease in compression ratio.     

肋片间距对表冷器性能影响的实验研究

表冷器肋片间距是影响表冷器传热性能的主要因素。在实验研究和理论分析的基础上，以单位体积换热量和单位阻力换热量为衡量依赖，找出了表冷器性能相对优化的肋片间距值。结果表明，在常用的间距范围内，3.3mm左右较好。     

三级复叠式制冷系统低温级制冷剂的应用分析

为研究三级复叠制冷系统中低温循环制冷剂替代的可行性方案,采用R1150/R170/R717、R50/R170/R717和R14/R170/R717三种工质组合,对三级复叠式制冷系统的高低温循环压缩机的排气温度、压缩机输入功率、COP、热力学完善度、系统的■效率、■损失以及系统中各个部件■损失所占比例随蒸发温度的变化进行热力学分析。研究结果表明:不同蒸发温度下均存在最佳中间循环冷凝温度,使COP值最大。蒸发温度由-100.0℃升高到-80.0℃时,R1150/R170/R717的■损失最小,COP、热力学完善度和■效率最大。R1150/R170/R717的COP由0.60增大到0.82。R1150/R170/R717的COP比R14/R170/R717的COP高3.47%～4.49%。主要的■损失部件是冷凝器,冷凝器的■损失所占比例随蒸发温度的升高而升高。推荐在三级复叠式制冷系统中采用R1150/R170/R717制冷剂组合方案,研究结果为三级复叠式制冷系统工质组的选择提供理论依据。     

太阳能喷射式制冷系统性能的实验研究

对太阳能喷射式制冷系统进行了实验研究,采用电加热模拟太阳能辐射的方法,研究了冷凝器、发生器和蒸发器温度对制冷系统COP的影响,给出了太阳能喷射式制冷系统制冷能力与COP随时刻的变化关系。系统在80℃热源条件下,全天提供16℃的冷水,系统最大制冷量为0.43 kW。     

Investigation on adsorption refrigeration with a single adsorbent bed

This paper describes an experimental investigation of adsorption refrigeration with a single generator (adsorbent bed) in a basic cycle, which verifies the previous theoretical conclusions that the cycle time and the maximum desorption temperature (corresponding to the maximum temperature of external heat source) are key factors with various influences to the COP and the cooling capacity of a cycle on a prototype machine. Moreover, in order to investigate the difference between theoretical and real cycles, a new physical parameter, the packing coefficient, is introduced to the adsorption cycle © 1998 John Wiley & Sons Ltd.     

Experimental investigations of a small-scale solar-assisted absorption cooling system

The present study deals with a small-scale solar-assisted absorption cooling system having a cooling capacity of 3.52 kW and was investigated experimentally under the climatic conditions of Taxila, Pakistan. Initially, a mathematical model was developed for LiBr/H₂O vapor absorption system alongside flat-plate solar thermal collectors to achieve the required operating temperature range of 75°C. Following this, a parametric analysis of the whole system was performed, including various design and climate parameters, such as the working temperatures of the generator, evaporator, condenser, absorber, mass flow rate, and coefficient of performance (COP) of the system. An experimental setup was coupled with solar collectors and instruments to get hot water using solar energy and measurements of main parameters for real-time performance assessment. From the results obtained, it was revealed that the maximum average COP of the system achieved was 0.70, and the maximum outlet temperature from solar thermal collectors was 75°C. A sensitivity analysis was performed to validate the potential of the absorption machine in the seasonal cooling demand. An economic valuation was accomplished based on the current cost of conventional cooling systems. It was established that the solar cooling system is economical only when shared with domestic water heating.     

An experimental comparison between LPG and engine exhaust gas as energy source for an absorption refrigeration system

This paper presents an experimental analysis of an absorption refrigeration system, comparing two different energy sources. The exhaust gas from an internal combustion engine was evaluated against the original energy source, liquefied petroleum gas (LPG). The experiments were performed in a domestic refrigerator, monitoring the air temperature and humidity inside the equipment. A production engine was tested with 25% and wide‐open throttle valve (WOT), mounted on a bench dynamometer. The energy demand, cooling capacity and coefficient of performance (COP) were determined for both energy sources. The results showed that engine exhaust gas is a potential source for absorption refrigeration systems. When the engine exhaust gas was used as energy source, the energy available for the refrigerator was higher with 25% throttle valve opening. Copyright © 2011 John Wiley & Sons, Ltd.     

An experimental analysis of the effect of refrigerant charge level on an automotive refrigeration system

The performance of an automotive refrigeration system is dependent on the refrigerant charge level. Due to inevitable leaks in the system, the amount of refrigerant will decrease over time and thus ultimately reduce the system's performance. A reduction in the amount of refrigerant charge results in excessive compressor cycling, a lower condenser pressure, a higher refrigeration temperature, and an increase in the amount of superheat. This paper identifies and quantifies the individual component losses in an automotive refrigeration system as a function of the refrigerant charge level. A second law analysis, based on nondimensional entropy generation, is carried out to quantify the thermodynamic losses. A passenger vehicle with a cycling-clutch, orifice tube refrigeration system was instrumented to measure various temperatures and pressures, and relative humidity. The data were collected at idle conditions. Thermodynamic equations, which are used to determine the system's thermal performance, are presented. The system's second law efficiency increases 26 % as the amount of refrigerant charge decreases by 44 %. Also the individual component losses are quantified as a function of the refrigerant charge level. The compressor and the condenser losses account for the largest percentage of the total losses, and are of similar magnitude. The evaporator–accumulator and the orifice tube losses account for a smaller percentage of the total losses, and are also of similar magnitude. With a reduction in the refrigerant charge level of 44 %, the losses in the compressor, the condenser, the evaporator–accumulator, and the orifice tube decrease 13 %, 8 %, 10 %, and 33 %, respectively.     

Simulation on a proposed large-scale liquid hydrogen plant using a multi-component refrigerant refrigeration system

A proposed liquid hydrogen plant using a multi-component refrigerant (MR) refrigeration system is explained in this paper. A cycle that is capable of producing 100 tons of liquid hydrogen per day is simulated. The MR system can be used to cool feed normal hydrogen gas from 25 °C to the equilibrium temperature of −193 °C with a high efficiency. In addition, for the transition from the equilibrium temperature of the hydrogen gas from −193 °C to −253 °C, the new proposed four H₂ Joule–Brayton cascade refrigeration system is recommended. The overall power consumption of the proposed plant is 5.35 kWh/kg_LH2, with an ideal minimum of 2.89 kWh/kg_LH2. The current plant in Ingolstadt is used as a reference, which has an energy consumption of 13.58 kWh/kg_LH2 and an efficiency of 21.28%: the efficiency of the proposed system is 54.02% or more, where this depends on the assumed efficiency values for the compressors and expanders. Moreover, the proposed system has some smaller-size heat exchangers, much smaller compressor motors, and smaller crankcase compressors. Thus, it could represent a plant with the lowest construction cost with respect to the amount of liquid hydrogen produced in comparison to today’s plants, e.g., in Ingolstadt and Leuna. Therefore, the proposed system has many improvements that serve as an example for future hydrogen liquefaction plants.     

煤粉细度对燃烧特性影响的实验研究

对冷水江和斗笠山两种煤粉,采用热天平进行了热重分析实验,分析了煤粉样在不同细度下的着火特性、燃烧特性、燃尽性能及动力学参数,给出了反映煤粉燃尽性能的综合判别指数Hj并进行了对比.结果表明:在相同的升温速度下,随着煤粉粒径的减小,挥发分析出量及DTG峰值增大,出现最大燃烧速率的时间提前;煤粉粒径减小,活化能降低,着火温度降低,着火提前,煤粉的燃烧特性也随之变好.