Performance enhancement of a subcooled cold storage air conditioning system

This article experimentally investigates the enhancement of thermal performance for an air conditioning system utilizing a cold storage unit as a subcooler. The cold storage unit is composed of an energy storage tank, liquid-side heat exchanger, suction-side heat exchanger and energy storage material (ESM), water. When the cooling load is lower than the nominal cooling capacity of the system, the cold storage unit can store extra cold energy of the system to subcool the condenser outlet refrigerant. Hence, both the cooling capacity and coefficient of performance (COP) of the system will be increased. This experiment tests the two operation modes: subcooled mode with energy storage and non-subcooled mode without energy storage. The results show that for fixed cooling loads at 3.05 kW, 3.5 kW and 3.95 kW, the COP of the subcooled mode are 16.0%, 15.6% and 14.1% higher than those of the non-subcooled mode, respectively. In the varied cooling load experiments, the COP of the subcooled cold storage air conditioning system is 15.3% higher than the conventional system.     

Case study and theoretical analysis of a solar driven two-stage rotary desiccant cooling system assisted by vapor compression air-conditioning

In this paper, a solar hybrid desiccant air conditioning system, which combines the technologies of two-stage desiccant cooling (TSDC) and air-source vapor compression air-conditioning (VAC) together, has been configured, experimentally investigated and theoretically analyzed. The system mainly includes a TSDC unit with design cooling capacity for 10 kW, an air-source VAC unit with 20 kW in nominal cooling capacity, a flat plate solar collector array for 90 m², a hot water storage tank and a cooling tower. Performance model of the system has been created in TRNSYS simulation studio. The objective of this paper is to report the test result of the solar hybrid air conditioning system and evaluate the energy saving potential, thereby providing useful data for practical application. Experimental results show that, under typical weather condition, the solar driven desiccant cooling unit can achieve an average cooling capacity of 10.9 kW, which contributes 35.7% of the cooling capacity provided by the hybrid system. Corresponding average thermal COP is over 1.0, electric COP is up to 11.48. Under Beijing (temperate), Shanghai (humid) and Hong Kong (extreme humid) weather conditions, the solar TSDC unit can remove about 57%, 69% and 55% of the seasonal moisture load, thereby reducing electric power consumption by about 31%, 34% and 22%, respectively. These suggest that the solar hybrid system is feasible for a wide range of operating conditions.     

太阳能辅助电动汽车热泵空调系统的研究

介绍研制的电动汽车热泵空调系统及其配用的双工作腔滑片压缩机的性能，依据测试样机的试验结果分转速对该空调系统制冷量，输入功率及COP等性能的影响，若轿车顶盖全部布满太阳电池，所产生的电能约为225W,可以使空调系统的制冷量增加8％左右，同时还能降低汽车空调冷负荷的峰值。     

Thermal storage in an air conditioning system with dual energy storage unit

在自行搭建的双蓄能实验平台上进行了制冷兼蓄热实验研究,对比了制冷兼蓄热模式和一般制冷模式,探讨了不同冷冻水流量和不同风机盘管风量对机组性能的影响.实验结果表明:蓄热对机组制冷端的影响很小,但是由于回收了大量的冷凝热,使得机组的综合能效比得到大幅提高,因此蓄热对空调节能具有较大作用.此外,在制冷兼蓄热模式下,冷冻水流量或风机盘管风量越大,机组的综合能效比越大,当风量为1033 m³/h,冷冻水流量为972 L/h时,机组综合能效比高达7.06.     

Operational results of an intermittent absorption cooling unit

The concept of solar cooling is appealing because the cooling load is in phase with the intensity of solar energy. Many system arrangements or cycles are employed to achieve solar cooling, such as Absorption, desiccant or Rankine‐vapour compression systems. The technical feasibility of driving an absorption‐cooling unit by a low‐temperature heat source (such as solar energy using a simple flat‐plate collector) for air‐conditioning applications is investigated in this work. This study aims to design and construct a prototype for an intermittent absorption refrigeration system and to examine its implementation. The operating characteristics of the considered unit are extensively investigated. In order to accomplish this strategy, the prototype was integrated in a test rig designed for this purpose and equipped with the necessary measuring instruments to determine the required operating criteria of the unit. The energy added or extracted to or from the different unit components is calculated and the system performance is analysed. The C.O.P of the unit is found to be 19% which is 2% lower than the designed value, which could be regarded as an encouraging result for more studies in this field. Copyright © 2002 John Wiley & Sons, Ltd.     

Studies of air-flow and temperature fields inside a passenger compartment for improving thermal comfort and saving energy. Part II: Simulation results and discussion

In the first paper the simulation model, numerical methods and experimental measurement validation for a vehicle compartment with two chairs and one long bench have been provided. In this paper, the simulated results are presented. Simulation results with a variety of conditions reveal that: (1) a good choice for decreasing the cooling load in the summer time is increasing the inlet air temperature, not reducing the volume flow rate of the inlet air; (2) the thermal comfort in a compartment with given conditions depends on the number of persons in it. For the compartment studied, when there are two passengers in the compartment both of them should sit in the backside; (3) the outside temperature has appreciable effect on the cooling load. While change of the vehicle speed hardly affects the cooling load of air conditioner when good seal of the compartment is assumed; (4) to decrease the cooling load one can change the material of the window (reducing its transmissivity), and improve thermal insulation on the vehicle body; (5) a better flow circulation near the compartment bottom is favorable to improve the uniformity of temperature field around the driver’s foot zone. The inlet air direction should be kept horizontal.     

不同地区住宅能耗与太阳能吸收式空调系统匹配性分析与模拟研究

为了满足农村住宅清洁用能的需求,多种形式的能源系统逐渐开始应用于广大的农村地区。随着太阳能集热器集热效率的提高,热驱动机组各项性能不断改善,这样有利于太阳能吸收式空调系统在农村地区的应用。为了研究太阳能吸收式空调系统与农村住宅全年能耗的匹配问题,文章首先建立了DeST住宅模型,然后利用TRNSYS软件建立了太阳能吸收式空调系统模型,最后根据模拟结果对国内不同气候区内农村住宅供热季、供冷季的平均热负荷值,以及全年的能耗进行分析。此外,文章还分析了典型日太阳能吸收式空调系统的运行策略与效果。分析结果表明:在无辅助热源的条件下,太阳能集热器的集热温度会大于80℃,满足空调机组的热驱动温度,因此可以作为太阳能吸收式空调系统的的热源;当启动温度为85℃时,空调机组的制冷量可以达到8 kW,性能系数COP为0.733。     

基于分区建模的大空间分层空调负荷随分层高度变化的研究

以某坡屋顶大空间建筑为研究对象,利用eQUEST软件,提出了空调区和非空调区分区的建模方法,依据所建模型分析全室空调和不同分层高度时夏季分层空调峰值冷负荷特性.模拟结果表明,分层空调形式的负荷比全室空调的减少30%以上,夏季空调峰值负荷随分层高度增加近似线性增加.比较模拟负荷与常规分层空调负荷计算结果发现,两者相对误差小于3%,说明基于动态能耗模拟软件分区模拟大空间分层空调负荷的方法合理.     

夏季大空间屋顶节能喷淋器的实验研究

针对大空间建筑模型进行喷淋效果实验,通过实验得到以下结论:由于Low-E玻璃材料在夏季具有较强的温室效应,未喷淋时,屋顶内表面平均温度为56.8℃,与环境平均温差为21.9℃,增加了空调的能耗。彩钢板屋顶具有较好的保温性能,未喷淋时,屋顶内表面平均温度为40.6℃,模型内部空间平均温度为38.9℃,该温度远低于Low-E玻璃模型温度,能耗比Low-E玻璃模型小。喷淋时,Low-E内层温度比外层温度低约5.4℃;彩钢板内外层温度在喷淋时两者相差不大,仅为0.5℃,喷淋对Low-E玻璃屋顶空调节能意义明显。     

冰蓄冷空调蓄冰罐单独融冰供冷的设备选择计算

本文介绍了建筑物冰蓄冷空调设计中当某些时间的空调冷负荷小于制冷机的空调供冷量而由蓄冰罐单独融冰供冷的设备选择计算方法。     

太阳能吸收式空调系统的经济性分析

针对一个特定的对象,进行了太阳能吸收式空调系统寿命周期内的模拟计算及影响因素的分析,结果表明：（1）单纯太阳能空调（无采暖与热水供应）的经济性很差,太阳能空调与供热的复合系统的经济性要优于单纯的太阳能空调系统;（2）太阳能采暖与空调的复合系统,采暖与供冷的负荷比对系统的经济性有很大影响,即使在最佳的负荷比时仍无法和常规的系统竞争;（3）太阳能与生活热水系统的负荷系统中,热水负荷所占比重越大,经济性越好,当太阳能空调使用生活热水系统夏季多余的热量时,太阳能空调系统经济上可以和天然气锅炉＋电动制冷机竞争,并具有很好的节能性和环境效益。     

基于Kuli的某商用车空调系统性能仿真及优化分析

本文利用流体分析软件Kuli建立了基于几何参数和实验数据的空调系统计算模型,对某商用车的空调系统进行了仿真分析,并用实验证实了仿真的可行性。分别建立了此空调系统的国内和国外某炎热地区的计算模型,结果表明此空调系统在国内工况可满足设计要求,而不满足国外某炎热地区的降温需求,在此基础上对空调系统提出了优化方案,优化后的空调系统可满足国外工况的设计要求。     

The minimum work required for air conditioning process

This paper presents a theoretical analysis based on the second law of thermodynamics to estimate the minimum work required for the air conditioning process. The air conditioning process for hot and humid climates involves reducing air temperature and humidity. In the present analysis the inlet state is the state of the environment which has also been chosen as the dead state. The final state is the human thermal comfort fixed at 20 °C dry bulb temperature and 60% relative humidity. The general air conditioning process is represented by an equivalent path consisting of an isothermal dehumidification followed by a sensible cooling. An exergy analysis is performed on each process separately. Dehumidification is analyzed as a separation process of an ideal mixture of air and water vapor. The variations of the minimum work required for the air conditioning process with the ambient conditions is estimated and the ratio of the work needed for dehumidification to the total work needed to perform the entire process is presented. The effect of small variations in the final conditions on the minimum required work is evaluated. Tolerating a warmer or more humid final condition can be an easy solution to reduce the energy consumptions during critical load periods.     

废热/动力联合驱动的混合制冷循环特性分析

根据废热驱动的吸收式制冷循环特点以及对汽车制冷系统的技术要求,提出了一种采用直接风冷的,以汽车发动机废热和动力联合驱动的新型吸收/压缩混合制冷循环.在设计工况(空气温度35℃,冷凝温度55℃,制冷剂蒸发温度3℃,制冷负荷30kW)下,对采用R124-DMAC工质的混合制冷循环进行热力计算,其综合性能系数(COPint)为14.85.通过热力循环分析发现发生器负荷率和环境温度变化对混合制冷循环工作特性有较大的影响.     

风机盘管冷量影响因素显著性分析及其冷量计量方法

本文利用正交试验的方差分析方法讨论了风机盘管各因素对其冷量的影响程度,在此基础上阐述了一种针对定流量风机盘管集中空调系统的冷量计量方法--风侧冷量计量法的基本原理,并对该方法的计量精度进行了分析。     

Performance evaluation of a solar-powered flat-plate multichannel liquid desiccant air conditioning system

There has been a limited application of liquid desiccant (LD) dehumidification systems in space air conditioning until now. The key elements responsible for this restricted implementation are leakage of desiccant solution, corrosion of components, and solution carryover along with the processed air to the space to be conditioned. To remove these problems, an evacuated tube solar heat collector-driven multichannel liquid desiccant air conditioning system has been proposed and experimentally investigated. In this study, dehumidification and regeneration rate, their effectiveness, cooling effect of the dehumidifier, and indirect evaporative cooling unit have been analyzed. The results obtained indicate that the process air has been dehumidified and cooled by 6.32 g kg⁻¹ and 5.26°C, respectively. The regeneration rate and effectiveness have been obtained to be 0.26 g s⁻¹ and 0.31, respectively. In terms of the cooling effect, the system output of 0.703 and 0.130 kW has been obtained from the dehumidifier and indirect evaporative cooling unit of the system, respectively. The proposed system validates the possibility of the novel solar-powered liquid desiccant air conditioning system concept and provides growth and development of the LD air conditioning technology for space air conditioning.     

Methodology for the energy analysis of an air cooled GAX absorption heat pump operated by natural gas and solar energy

In this work a methodological analysis and energy evaluation of an air cooled absorption system, with generator–absorber heat exchange (GAX), and operated by a hybrid natural gas–solar energy source is presented. Given the characteristic non-linearity of the resulting system of equations, the methodology proposed envisages a calculation sequence for the external currents and an iterative procedure for the internal currents.The system studied intents to be an alternative for space conditioning in the residential sector, the unit was designed with a capacity of 10.6 kW (3 Ton) of cooling and uses as working fluid ammonia–water. Giving priority to internal energy integration, an arrangement is proposed for the GAX cycle that allows 19% of solar contribution at full load, being greater at partial loads. In spite of using ambient air up to 40 °C with a relative humidity of 24% as cooling source, a COP value of 0.86 for cooling and 1.86 for heating was calculated, with an internal energy integration of 16.9 kW, 37% more than the energy that is supplied to the generator.     

AE94.3A型燃气轮机进气冷却的应用可行性研究

对AE94.3A型燃气轮机燃气-蒸汽联合循环热力系统平衡进行研究进而发现,与同类型、同等级不同型号机组相比,AE94.3A型联合循环机组余热锅炉的排烟温度较高,排烟余热仍有进一步利用的空间。通过设计优化,扩大省煤器受热面,回收烟气余热加热给水,驱动热水型溴化锂制冷机制冷,用于机组满负荷调峰时的压气机进气冷却或厂房及办公区域空调供冷,对改善燃气轮机联合循环的运行性能,实现能源梯级利用,提高能源利用率和机组经济性运行起到了很大作用。     

水源热泵在空调系统中应用的经济性分析

本文对水源热泵的能耗进行了分析,表明水源热泵机组的性能系数与水源的温度直接相关,讨论了水源热泵在嵊州市空调系统集中供冷供热的可行性,对集中冷热水供水系统夏季空调工况与冬季热泵工况的经济性进行了计算与分析,结果表明,嵊州市利用水源热泵建立集中冷热水供水系统的社会经济效益显著,具有重要的节能与环保意义。     

基于互连思想的直接空冷机组运行优化技术研究

将不同机组间的空冷凝汽器单元或者不同机组空冷凝汽器进行互连,充分利用停运或低负荷机组的空冷散热面积,提高运行机组的散热面积和散热能力。通过对直接空冷单元互连和直接空冷凝汽器互连两种设计方案的分析表明,运行机组的运行背压获得较大幅度的下降,同时显著提高了运行机组在夏季高温条件下的带负荷能力和节能运行水平。随着环境温度或机组运行负荷的降低,通过互连改造后运行机组背压降低的幅度逐渐减小。