太阳能喷射制冷系统应用性能模拟

建立了太阳能喷射制冷系统性能分析模型,结合上海地区典型气象日气象条件,研究了太阳能喷射制冷系统在上海地区的动态性能及其应用的可行性。计算并分析了喷射子循环性能系数、系统热效率、太阳能保证率等逐时变化情况,分析了不同类型集热器对系统的影响。结果表明系统热效率、太阳能保证率等性能参数受气温、太阳能辐射强度等气象条件影响显著。一天中喷射子循环性能系数维持在0.5以上、8至14时太阳能保证率处于40%以上,表明可以通过增加集热器面积来满足用户要求,因此太阳能喷射制冷系统的应用其热力性能是可靠的,经济上是可行的。此外,研究表明集热器的类型对太阳能喷射制冷系统性能也有较大影响。     

太阳能吸收式串联流程制冷系统与性能分析

本文提出了一种串联流程的以太阳能与燃气双热源供热的溴化锂吸收式制冷系统。介绍了当前太阳能吸收式制冷的发展概况。对双热源制冷系统原理进行介绍,简述了制冷机内工质循环流程,并模拟分析了系统的热力性能,得到高压发生器与低压发生器在不同放气范围时系统制冷系数与双热源的供热分配情况。分析了一天内不同时段制冷系统运行特性在不同太阳辐照度下的变化特点。结果证明太阳能与燃气双热源串联流程溴化锂吸收式制冷方案具有节能高效的优势。     

带回热两级喷射制冷循环的特性分析

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。     

基于蒸汽喷射制冷的汽车空调建模与控制

以汽车尾气为热源,建立蒸汽喷射制冷循环的数学模型。针对汽车蒸汽喷射制冷系统的特点,设计应用于汽车蒸汽喷射制冷系统的模糊自适应PID控制器,并与PID控制算法进行对比研究。仿真结果表明,模糊自适应PID控制器在变负荷、变工况等条件下都优于PID控制器,为蒸汽喷射制冷在汽车空调中的应用提供可行性方案。     

太阳能喷射制冷的探讨

本文首先介绍了太阳能喷射制冷的原理及特点，然后分别介绍了系统的核心部件一喷射器、复合制冷系统以及制冷剂的研究进展。通过分析认为，随着电力紧缺以及绿色建筑的兴起，喷射制冷系统COP的提高，太阳能喷射制冷系统有着广阔的应用前景。     

太阳能喷射-电压缩复合制冷系统中增压器的选型及性能预测

本文预测了在建太阳能制冷实验台的性能及影响太阳能喷射系统的因素,并且对太阳能喷射．电压缩复合制冷系统中增压器的选型做了分析,认为采用变频压缩机作为复合系统的增压器可使系统效能更优。     

减压发生喷射吸收复合制冷原理与经济分析

为了提高制冷效率,降低换热器的热负荷,减少热能对制冷系统的注入,采用减压发生和液体喷射泵来推动制冷剂的循环,从而使整个制冷流程处在较低焓值下循环.无须给系统注入温度较高的热能,而只是利用吸收循环热,在降压条件下进行发生,大大降低了单位制冷量的能耗量,这优越于当前各类气体喷射吸收复合式制冷技术和其他各类制冷技术,其经济性是显而易见的,流程是简便易行的.     

斯特林制冷机用于商业制冷的研究现状初析

相对于传统的蒸汽压缩节流制冷系统,采用斯特林制冷循环的新型制冷系统具有高效率、“绿色”制冷剂、制冷温区广等特点,在环保及节能方面具有明显的优势。通过对国内外斯特林制冷技术用于商业制冷领域的发展进行综述,展望了这种极具潜力的制冷技术的前景。最后,大冷量中温区斯特林制冷机和冷头到冷空间的冷量传递作为斯特林制冷的两个关键技术分别进行了介绍。     

太阳能吸收式制冷-海水淡化联产系统在别墅的应用

设计太阳能吸收式制冷-海水淡化联产系统,以大连、深圳、上海3个沿海城市为例,选取一栋别墅建筑作为研究对象,利用Matlab对系统容量匹配和经济性进行比较。结果表明:对于同一栋别墅,太阳能集热器面积由建筑物所在地区的建筑冷负荷确定,大连最小,深圳其次,上海最大;淡水产量与建筑冷负荷呈正比关系;联产系统在上海初投资最高,在深圳运行维护费用最高,在大连投资回收期最长;相比太阳能吸收式制冷系统,太阳能吸收式制冷-海水淡化联产系统的投资回收期可缩短9.4%。     

一种新型双温空调器的混合制冷理论循环原理和节能潜力探讨

提出一种由空气处理器和金属辐射板作为双温蒸发器的新型空调制冷系统和相应的混合制冷理论循环。新型空调制冷系统主要由压缩机、冷凝器、两个热力膨胀阀、喷射器和双温度蒸发器构成。本文对制冷循环的性能以及室内空气处理过程进行了热力学分析和对比,结果表明：双温空调制冷理论循环的性能可比常规带新风的空调器提高13.73%,制冷系数可达7.43;当室内新风负荷和湿负荷较大的情况下,双温空调的制冷性能系数会有所降低,但仍比常规空调器的理论性能系数高5.21%。     

风冷太阳能双级氨喷射制冷系统冷藏工况性能分析

通过建立数学模型,对额定制冷量为9.4kW的冷藏库用风冷太阳能双级氨喷射制冷系统进行了变工况性能分析.该系统的制冷量随冷藏温度升高而增大,随环境温度升高而减小,随太阳辐照度增强而增大;COP的变化规律与制冷量类似,其差别是随太阳辐照度增强先迅速增大,但当太阳辐照度增大到一定程度后,COP的变化趋于平缓.在正常使用条件下(冷藏温度不低于4℃,环境温度不高于38℃,太阳辐照度不低于500W/m2),系统的制冷量为6.3～26kW,COP为0.042～0.087.该系统能较好地与亚热带典型城市南宁的果蔬盛产季节气候条件相匹配.     

Hybrid vapor compression refrigeration system with an integrated ejector cooling cycle

A refrigeration system was developed which combines a basic vapor compression refrigeration cycle with an ejector cooling cycle. The ejector cooling cycle is driven by the waste heat from the condenser in the vapor compression refrigeration cycle. The additional cooling capacity from the ejector cycle is directly input into the evaporator of the vapor compression refrigeration cycle. The governing equations are derived based on energy and mass conservation in each component including the compressor, ejector, generator, booster and heat exchangers. The system performance is first analyzed for the on-design conditions. The results show that the COP is improved by 9.1% for R22 system. The system is then compared with a basic refrigeration system for variations of five important variables. The system analysis shows that this refrigeration system can effectively improve the COP by the ejector cycle with the refrigerant which has high compressor discharge temperature.     

A theoretical study of a novel regenerative ejector refrigeration cycle

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.     

Use of ejectors in a multi-evaporator refrigeration system for performance enhancement

In this study, an improved cooling cycle for a conventional multi-evaporators simple compression system utilizing ejector for vapour precompression is analyzed. The ejector-enhanced refrigeration cycle consists of multi-evaporators that operate at different pressure and temperature levels. 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 model includes effects of friction at the constant-area mixing chamber. The energy efficiency and the performance characteristics of the novel cycle are theoretically investigated. The comparison between the novel and conventional system was made under the same operating conditions. Also, a comparison of the system performances with environment friendly refrigerants (R290, R600a, R717, R134a, R152a, and R141b) is made. The theoretical results show that the COP of the novel cycle is better than the conventional system.     

Numerical simulation of an advanced energy storage system using H2O–LiBr as working fluid, Part 1: System design and modeling

The advanced energy storage technology proposed and patented by authors can be applied for cooling, heating, dehumidifying, combined cooling and heating, and so on. It is also called the variable mass energy transformation and storage (VMETS) technology in which the masses in one or two storage tanks change continuously during the energy charging and discharging processes. This paper presents an advanced energy storage system using aqueous lithium bromide (H₂O–LiBr) as working fluid. As one of VMETS systems, this system is a closed system using two storage tanks. It is used to shift electrical load and store energy for cooling, heating or combined cooling and heating. It is environmental friendly because the water is used as refrigerant in the system. Its working principle and process of energy transformation and storage are totally different from those of the traditional thermal energy storage (TES) systems. The electric energy in off-peak time is mostly transformed into the chemical potential of the working fluid and stored in the system firstly. And then the potential is transformed into cold or heat energy by absorption refrigeration or heat pump mode when the consumers need the cold or heat energy. The key to the system is to regulate the chemical potential by controlling the absorbent (LiBr) mass fraction or concentration in the working fluid with respect to time. As a result, by using a solution storage tank and a water storage tank, the energy transformation and storage can be carried out at the desirable time to shift electric load efficiently. Since the concentration of the working solution in the VMETS cycle varies continuously, the working process of the VMETS system is dynamic. As the first part of our study, the working principle and flow of the VMETS system were introduced first, and then the system dynamic models were developed. To investigate the system characteristics and performances under full-storage and partial-storage strategies, the numerical simulation will be performed in the subsequent paper. The simulation results will be very helpful for guiding the actual system and device design.     

Thermal and exergoeconomic analysis of a novel solar driven combined power and ejector refrigeration (CPER) system

In the present study, a novel solar driven combined power and ejector refrigeration system (CPER) of 50 kW power capacity composed of an ORC (organic Rankine cycle) and an ejector refrigeration system is investigated. Solar driven CPER system is composed of two main cycles: collector cycle and refrigeration cycle. The collector cycle is made of a U-tube ETC and circulation pump and the ejector refrigeration cycle consists of generator, turbine, ejector, heat exchanger, condenser, evaporator, expansion valve, and pump. Thermodynamic performance of the proposed CPER system is evaluated and a thermo-economic analysis is conducted using the SPECO (specific exergy costing) method. A parametric study showed the effects of condenser temperature, evaporator temperature, generator pressure, turbine back pressure and turbine extraction ratio. The genetic algorithm optimization analysis is conducted which shows 25.5% improvement in thermal energy, 21.27% in exergy efficiency, and 7.76% reduction in the total cost of the CPER system. The results reveal that the performance of the CPER system is considerably improved at higher temperatures of generator and evaporator.     

Modelling commercial refrigeration systems coupled with water storage to improve energy efficiency and perform heat recovery

A basic CO₂ transcritical/subcritical commercial refrigeration system is considered, applied to cold rooms and display cabinets in a supermarket. Subcooling of the refrigerant or heat recovery from condensation can be performed, taking advantage of a large fire prevention water tank. The whole refrigeration system is modelled in a TRNSYS environment, taking into account the hourly weather data and calculating the hourly cooling load demand from display cabinets and cold rooms equipment. New types have been written to describe display cabinets and cold rooms, CO₂ refrigerating units and a particular water store.Simulations consider a simple double compression cycle with liquid receiver, and other options among which an auxiliary compressor. Results show that CO₂ plants are feasible and energetically acceptable in mild climates, provided that improvements to standard cycle are adopted. Furthermore, heat recovery can be effectively performed through the employment of a heat storage.     

一种新型喷射-压缩复合循环制冷系统节能运行优化工况点的探讨

CCRS是使用机械压缩机的制冷循环（RAC／MC）和使用喷射器的冷却循环（EJC）复合的一种新型节能循环系统，其中EJC是由RAC／MC的余热驱动的，并作为RAC／MC的底部循环，通过分析表明，CCRS的COP值比单独压缩制冷循环系统的COP有明显提高，而且合理的喷射冷却循环工况对COP值的提高有很大影响，在喷射工况一定时，发生器中温度的变化，使得系统的制冷量和COP存在极限值，此时对应的工况即系统的最佳工况，具有实际指导意义，同时还比较了系统使用R22和R134a作为压缩式制冷循环制冷剂的性能差异。     

两级蒸发对跨临界CO_2引射制冷系统影响的实验研究

两级蒸发引射制冷循环中通过二级蒸发器不仅能调节引射器出口干度还能提高系统效率。通过改变第二蒸发器冷冻水流量对两级蒸发引射制冷系统进行实验研究,并与改变引射器面积比的调控效果进行比较。结果表明:在实验工况范围内,气冷器压力、第一蒸发器压力和压缩机流量都随第二蒸发器冷冻水流量的增加而增大;而且引射器面积比越大,气冷器压力越高而蒸发器压力和压缩机流量越低。同时,系统引射系数随第二蒸发器冷冻水流量的增加而降低,而制冷量和COP则升高,尤其是在小引射系数下,系统制冷量和COP提高的更为明显。本研究为引射循环提供了另外一种良好的调控思路。     

一种新型跨临界CO2冷电联供系统热力分析

提出一种新型跨临界二氧化碳（trans-critical carbon dioxide,TCO₂）再压缩循环和喷射器制冷循环耦合的冷电联供系统。该系统在输出电能的同时,利用低品位热能驱动喷射器工作输出冷量。以输出电量1 MW为设计目标,对比冷电联供系统和再压缩发电系统的性能,研究联供系统各部件（火用）损和主要热力参数对其性能的影响。结果表明：联供系统利用CO₂余热驱动喷射器输出冷量,循环热效率高于单一再压缩系统;加热器（火用）损所占比例最大,回热器次之;透平进口温度、压力和背压对联供系统工质流量、循环效率、输出功率、加热器功率、压缩机耗功及喷射器制冷量等参数影响较大;而冷凝温度和蒸发温度仅对制冷循环制冷量影响较大。在设定条件下,联供系统的循环热效率和（火用）效率可分别达到46.99%和47.21%。