Optimization and comparative performance analysis of conventional and desiccant air conditioning systems regenerated by two different modes for hot and humid climates:Experimental investigation

A desiccant air conditioning system is considered a capable alternative to a conventional air conditioning system because of its independent control of temperature,humidity and being eco-friendly.Also,to resolve the problem of more energy consumption for the restoration of a desiccant,structures comprising of desiccant can utilize thermal energy or complete waste heat to revive desiccant material.Therefore,this research work executes an experimental,optimization and comparative examination for conventional and desiccant air conditioning sys-tems regenerated by two different modes,i.e.firstly using(Mode-I)complete waste heat from condenser and secondly using(Mode-II)rod(electric heater)heat for regeneration at different process air inlet temperatures,i.e.(28,29.5,31,32.5,34,35.5 and 37°C),at different process air inlet velocities,i.e.(1.5,2.5,3.5 and 4.5 m/s)and a fix(2.5 m/s)regeneration air inlet velocity.Thus,optimization of performance parameters,i.e.VCOP,ECOP,dehumidification effectiveness,moisture removal capacity(kg/hr),DCOP,regeneration effectiveness and regeneration rate(kg/hr),is identified for achieving maximum efficiency of conventional and desiccant air con-ditioning systems under the above operating conditions.

Metal hydride work pair development and its application on automobile air conditioning systems

Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26A10.13/ La0.6Y0.4Ni4.8Mn0.2 was developed working at 393-473 K/293-323 K/263-273 K. Property tests showed that both alloys have flat plateau slopes and small hystereses; system theoretical coefficient of performance （COP） is 0.711. Based on this work pair, a function proving automobile metal hydride refrigeration system was constructed. The equivalent thermal conductivities of the activated reaction beds were merely 1.1-1.6 W/（m-K）, which had not met practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power was 84.6 W at 423 K/303 K/273 K with COP being 0.26. By altering cycling parameters, experiment data showed that cooling power and system COP increase with the growth of heat source temperature as well as pre-heating and regeneration time while decrease with heat sink temperature increment. This study confirms the feasibility of automobile metal hydride refrigeration systems, while heat transfer properties of reaction beds still need to be improved for better performance.

Analysis and Evaluation of Thermal-cooling Loads of Office Buildings Using Carrier Software in Iran

The importance and necessity of energy saving in the world have been dis­cussed for many years,but achieving a logical and transparent solution is still one of the main challenges and problems of the world’s economy.The rapid growth of energy consumption in the last two decades has caused the security of the domestic energy supply of buildings to face serious prob­lems.In this research,first by entering parameters such as the type of mate­rials,doors and windows,and the type of soil on the floor connected to the ground,etc.in the heat and cold load calculation software(HAP Carrier)as the design calculations and then in the second step entering the specifica­tions inferred from the Iran’s national building code as a reference for ener­gy saving calculations,calculations are performed and compared as the first criterion,and finally these two outputs are compared.The actual energy consumption and determination of the building energy consumption index are determined as another criterion,as well as the degree of deviation from the actual consumption.The results showed that the theoretical method and the thermal and refrigeration load calculations of the Zanjan Gas Company building have 6%difference in cooling load but the heating load is about 34%different,which means for cooling loads,the theoretical model can be used with high accuracy but for heating loads,the national building code needs fundamental changes.

Investigation on the Influence of Refrigerant Charge Amount on the Cooling Performance of Air Conditioning Heat Pump System for Electric Vehicles

The application of air conditioning heat pump(ACHP) in electric vehicles could lead to significant electrical power saving effect. As for an air conditioning heat pump system for electric vehicles, the influence of refrigerant charge amount should be investigated during the design phase. In this study, experimental method was employed to investigate the influence of the refrigerant charge amount on the performance of the ACHP system. The results showed that the refrigerant charge amount had different influence on the refrigerant properties at various locations within the system. The coefficient of performance and pressure-enthalpy diagram were calculated, and showed a close relationship with refrigerant charge amount under different compressor speeds. The degree of subcooling and the degree of superheating were recorded and the critical charge amount was determined by a typical practical test method. In addition, the critical refrigerant charge amount determined by the experimental method was also compared with two typical void fraction correlation models, and the model with consideration of two phase stream reaction of the refrigerant showed a good estimation accuracy on the critical charge amount.

A new ventilation mode of air conditioning in subway vehicles and its air distribution performance

The traditional ventilation mode of subway vehicles adopts the form that the inlets and outlets are placed on the upper part of the cabin.The air distribution formed in this mode often cause serious problems of thermal comfort and energy consumption.In order to solve these problems caused by the traditional ventilation mode,a new hybrid ventilation mode was proposed.The hybrid ventilation mode uses both upper and underside air supply inlets.A method for evaluating the air distribution performance of subway air conditioning was developed.The method applies non-uniformity coefficients,maximum temperature difference,air diffusion performance index,modified energy utilization coefficient and Air short-circuit comprehensive coefficient.Air short-circuit comprehensive coefficient was a new index to evaluate the degree of air short-circuit of supply air.Based on the airflow simulation,the air distribution performance for the hybrid ventilation mode was evaluated using these indexes,and compared with the traditional ventilation mode.The results show that compared with the traditional ventilation mode,the hybrid ventilation mode has more uniform temperature distribution,better thermal comfort,higher energy utilization efficiency and lower degree of air short-circuit of supply air.

Modelling of a Two-Phase Thermosyphon Loop for Passive Air-Conditioning of a House in Hot and Dry Climate Countries

The two-phase thermosyphon loop is an efficient solution for space cooling. This paper presents the simulation results of numerical studies on the heat transfer and thermal performance of a two-phase thermosiphon loop for passive air-conditioning of a house. The fluid considered in this study is methanol, which is compatible with copper and is environmentally friendly. These numerical results show that the temperature at the evaporator wall drops from 23°C to 13°C and increases at the condenser. The solar flux density has a strong influence on the condenser temperature. The mass flow rates and masses at the evaporator and condenser increase with temperature. The variation of evaporating and condensing temperature affects the performance of the system. For a constant evaporating and condensing temperature of 2°C and 29°C, the COP is 0.77 and 0.84 respectively. With these results, the use of the two-phase thermosyphon loop in air conditioning is possible to obtain a thermal comfort of the occupants acceptable by the standards but with a large exchange surface of the evaporator.

夏热冬冷地区多能互补溶液除湿空调系统优化

为缓解基于太阳能-地热能(太-地)互补利用的溶液除湿空调系统在夏热冬冷地区中长期运行后土壤温度产生较大波动导致系统能效降低的问题。提出一种太阳能-地热能-空气能(太-地-空)多能互补的溶液除湿空调系统,针对该系统采用的过渡季节和制热季节补热方式对土壤温升及系统能效进行研究。结果表明:太-地互补系统运行20 a后土壤温度上升18.3℃,新系统在过渡补热和制热季节补热2种方式下运行20 a期间土壤温度无大幅波动;太-地系统运行20 a后机组制冷和系统全年性能系数C_(OP)分别下降30.5%和24.5%,太-地-空系统则在20 a的运行期间内均稳定在额定值。由研究结果可知,太-地-空多能互补的溶液除湿空调系统采用过渡季节补热的方式不会出现土壤热不平衡性问题,系统更能够长期稳定运行。

混合工质电动汽车空调全生命周期气候性能分析

空调作为整车系统中环境调控的关键子系统,其全生命周期的碳排放对于电动汽车的环保和排放要求至关重要。本文结合汽车空调系统全生命周期气候性能LCCP模型及相关数据,对全国各省份电动汽车空调系统的LCCP情况进行分析,同时对两种不同制热方案以及不同电力碳强度下的LCCP进行了比较分析。结果表明,RE170/R134a低GWP混合工质(二甲醚与R134a质量分数比90∶10)替换后电动汽车空调LCCP值降低了11.2%~28.1%,而采用热泵替换PTC电加热器后电动汽车空调LCCP值降低了0~33.1%,此外,随着未来我国电力碳强度与电动汽车保有量的变化,至2035年单辆车的LCCP值将会下降31.7%~39.3%,而全国整体电动汽车LCCP值将大幅上升。

回热器对CO_(2)驻车空调系统制热性能影响的研究

为了提升驻车空调的制热性能,搭建了一套带回热器的跨临界CO_(2)驻车空调系统,在焓差室中实验研究了有无回热器时气冷器出口温度与排气压力对系统的性能影响。结果表明:在排气压力分别为8.5、9.0、9.5 MPa时,气冷器出口温度从20℃升高至35℃时,制热COP_(h)降低幅度分别为29.7%、19.9%、16.4%;系统使用回热器后最优排气压力下降,下降幅度分别为4.4%、6.1%,对应的最大COP_(h)增加幅度分别为3.2%、3.7%。通过曲面拟合得到了系统使用回热器时提升制热性能的排气压力与气冷器出口温度关联式,该式对回热器在跨临界CO_(2)驻车空调系统制热模式下的实际应用有一定指导意义。

基于盲板的地板送风式数据中心热管理与能效案例研究

数据中心机房空调设备长期运行,每年需对其性能进行测试和评估,以确保安全高效运行。针对机架内服务器布局、盲板结构以及工况适应性进行实测,研究了封闭式冷通道地板下送风式数据中心的热环境;并通过热性能指标和能效指标,对该数据中心的安全性和能效进行了全年评估。结果表明:在冷通道中间区域推荐安装功率为2 kW以上的机架;机架间隙处安装盲板后,能够促进服务器内部冷气流循环,减少热气流的回流干扰,最大出口温度降低3.32℃,出口平均速度降低约24%;夏季工况时,该数据中心的PUE、WUE、CUE分别约为1.2、3.5、0.84,且WUE呈现出较强的季节性,冬季工况时,自由冷却可有效降低数据中心的能耗。此外,数据中心冷通道末端的机架过热问题显著,其中16个机架的机柜冷却指数均低于90%,热损失较高。

耦合溶液除湿的二氧化碳制冷系统性能仿真

二氧化碳具有环保、稳定性好、制取成本低等多种优势,被认为是比较理想的取代当前使用的HCFCs和HFCs的制冷剂。然而,跨临界二氧化碳制冷循环由于高压问题导致循环效率较低,并且冷凝除湿效率低下。为了解决上述问题,论文提出了一种耦合了溶液除湿系统的跨临界二氧化碳压缩式制冷系统,并进行了理论模拟和分析。发现在不同工况下,该系统相比单独的二氧化碳制冷循环系统,效率可以提高10%~80%。表明其拥有广阔的发展潜力和应用前景。

模块化光伏空调机组研发及性能实测分析

针对岛礁等孤立区域远离内陆、设备系统维修不便、安全可靠性要求高的问题,本文设计出直流型、交流型蓄电模块化新型光伏空调机组,对蓄电、逆变、制冷等机组部件进行了集成设计,对集成热堆积造成的机组性能衰减进行了理论分析。搭建了性能实验平台,实测了晴天、多云和雨天等不同天气工况下模块化空调机组的运行性能,得到2类机组的COP范围为2.80~3.35。模块化光伏空调机组可满足太阳能丰富的孤立区域的空调需求,具有更换灵活方便的特点。

新型高效空气冷却燃气轮机系统热力性能分析

为改善空气冷却重型燃气轮机热力性能,提出了一种能够高效利用抽气能量的新型空气冷却燃气轮机系统并研究了其热力性能的变化。以传统典型F级燃气轮机不同环境温度下的性能数据作为对比基础,通过数值仿真分析了新型高效空气冷却燃气轮机中冷却系统设计参数变更条件下的系统性能指标变化,计算对比了3种运行模式下的热力性能。结果表明:新型高效空气冷却燃气轮机能够有效降低压气机抽气温度,进而改善燃气轮机热力性能。在夏季工况下,进口温度分别被冷却到30、20、15℃时,燃气轮机功率分别升高了25.92、40.49、48.22 MW,燃气轮机效率分别提升了0.78、1.19、1.40个百分点。

空调负荷集群参与辅助服务的运行调控与评价技术综述

空调负荷具有总量大、易调节、对用户影响较小的特点,是理想的需求侧可调节资源,有必要从不同角度梳理空调负荷参与辅助服务技术的研究进展和方向。首先,介绍不同类型空调资源的单体和聚合建模技术。其次,分析了空调参与一次调频、二次调频、备用容量等不同辅助服务的主要难题和技术方法,介绍考虑信息安全可靠的空调调控技术,并从电网互动和用户舒适度等方面归纳空调负荷的评价技术。最后,提出进一步挖掘空调负荷调节潜力的建议,以期促进空调负荷调控技术从理论研究向实际应用的转化。

小管径空调冷凝器翅片的优化

空调小管径换热器可降低成本、减少制冷剂充注量,对实现节能减排意义重大。对5 mm单排管空调冷凝器的平直翅片进行优化,以代替一款7 mm单排管空调冷凝器。优化对象为管间距、片宽和翅片间距,优化目标为增大换热量、减小空气侧压降并降低成本。选用田口法进行实验设计和单目标优化,用灰色关联度分析和综合性能指标法进行多目标优化,最终优化结果为管间距16.0 mm,片宽16 mm,片距1.4 mm,换热量与D7管原型机持平,压降降低35%,成本降低26%,可成功代替7 mm冷凝器。

R1234yf新能源汽车空调电子膨胀阀测试系统研制

针对目前国内现有电子膨胀阀测试系统偏差大、测试范围小、耗能大,研制了一种新型R1234yf新能源汽车空调电子膨胀阀测试系统,该测试系统利用制冷剂节流后气相经压缩机加压、液相经制冷剂循环泵加压,两相充分混合后进入冷凝器,利用排气节流阀直接控制被测电子膨胀阀阀后压力。依据汽车热管理国家标准对该测试系统进行了可行性及热力性能分析,并与实际制冷方法、液环法测试系统冷凝热负荷及耗功总和进行对比。结果表明:该系统利用两相环法,可以减少冷凝后的冷凝热量,通过排气节流阀控制被测阀后压力,取消蒸发器,提高系统性能;在流经被测试电子膨胀阀的工质质量流量为0.02~0.18 kg/s工况下,该系统冷凝热负荷较实际制冷方法减小了71.6%,较液环法降低了37.9%,耗功总和则比实际制冷方法下降了63.7%~38.6%,但比液环法约增加了7.5%。该系统可为新能源汽车空调行业电子膨胀阀性能测试提供可行且节能的测试方法。

热泵型多联式空调系统稳态仿真

热泵型多联式空调系统(简称热泵型多联机)相对于单冷型多联机,在系统结构和系统控制上更复杂,使得对其进行性能仿真时,需要在系统描述和求解算法方面进行改进。本文对热泵型多联机进行稳态仿真。通过使用邻接矩阵的对角线元素来反映部件工作状态,变换邻接矩阵切换制冷制热模式的方法,对热泵型多联机的结构进行描述;根据热泵型多联机实际运行时的控制策略,采用基于过热度/过冷度的制冷剂流量分配算法对模型进行求解。对于样机的仿真及实验对照表明:在额定制冷和额定制热工况下,热泵型多联机仿真预测的系统能力、功率和系统能效的误差均在5%以内,系统温度和压力的误差分别在±3℃和±100 kPa以内,能够满足热泵型多联机设计的精度需求。

电动汽车空调系统结构原理概述

随着环境可持续发展战略的提出,低碳、低排放的发展趋势是现代汽车工业的发展方向。纯电动汽车以其显著的环保性能、低噪声、低能耗等优势,作为环保交通工具出现在了人们的日常出行中。空调是汽车上的第二大耗能部件,对整车的能耗产生了较大的影响。通过电动空调结构的分析对比,为研究人员可以继续探索纯电动汽车空调系统在哪些方面可以进行改进,进一步提升空调系统的性能和功能,满足用户对舒适性、便捷性和节能环保的需求。

热泵空调系统对纯电动汽车采暖性能影响的试验研究

采暖装置的能耗对纯电动汽车的续驶里程产生重要影响。为解决采暖高能耗问题,热效率较高的热泵空调系统逐渐代替正温度系数(PTC)材料作为纯电动汽车的采暖装置。文章通过基于整车层面的对比试验研究,测试二者在不同温度工况下的采暖效果和功耗,分析热泵空调系统的代替效果。试验结果表明,在温度较高的工况下,热泵空调系统采暖效果与PTC接近并且能耗显著降低;在温度较低的工况下,热泵空调系统的采暖效果弱于PTC,同时节能效果对比PTC优势缩小。试验结果为热泵空调的选配和改进研究提供一定的参考。

电动轿车空调系统振动噪声传递路径测试分析

为控制某纯电动汽车怠速空调开启工况时车内噪声,开展空调系统振动噪声传递路径研究。首先,采用Bench-mark分析、整车-子系统性能分解、旋转件阶次频率分析等方法,获得了该纯电动汽车空调系统关键零部件振动噪声传递路径,发现冷却风扇安装支架刚度和空调管路振动是引起车内噪声偏大的主要因素;然后,提出了安装支架刚度加强方案和空调管路减振措施;最后通过试验数据验证,经过改进后该车型怠速空调开启工况车内噪声由46.2dB(A)降低到44.5dB(A),满足了目标值45.0dB(A)要求。上述研究方法可为纯电动汽车空调系统振动噪声传递路径分析提供参考,亦可为相关车型空调系统结构设计提供借鉴。