Performance analysis of ammonia-water absorption/compression combined refrigeration cycle

In view of different compressor adding ways in the ammonia-water absorption/compression combined refrigeration AWA /CCR cycle combining the Schulz state equation of the ammonia-water solution the theoretical analysis and calculations on two combination ways by adding the compressor in the high-pressure area and in the low-pressure area are conducted respectively.The effects of several factors including the evaporation temperature Te heat-source temperature Th as well as the cooling water temperature Tw on the equivalent heat consumption in compression qCW heat consumption in absorption qG and the system coefficient of performance COP are analyzed under the two combination configurations.The results show that the effect of the equivalent heat consumption in compression on the COP is less than that of the heat consumption in absorption.Besides the compressor set in the high-pressure area uses more energy than that in the low-pressure area. Moreover the compressor in the low-pressure area is superior to that in the high-pressure area with respect to the COP. Under the given intermediate pressure there is an optimum heat-source temperature corresponding to the maximum COP of the AWA/CCR cycle.

Experimental investigation of effect of refrigerant gases,compressor lubricant and operating conditions on performance of a heat pump

In the field of heat pumps,there are a number of parameters that affect the performance and efficiency of the apparatus,which have been the subject of studies by individual researchers in the literature.This study describes an experimental method in order to investigate the effects of some significant parameters on heat pump performance.In this regard,a laboratory heat pump setup has been utilized to operate in different working conditions for achieving an appropriate estimation to find out effects of mentioned parameters such as refrigerant type and charge amount,compressor oil viscosity,compressor cooling fan,secondary fluids temperature and flow rate.Different refrigerants have been selected and used as circulating fluid in the installed heat pump.Although this work has been devoted to a detailed attempt to recognize the effects of various parameters on the coefficient of performance(COP) value,an appropriate method has been carried out to survey the obtained results by using economic analysis.It was revealed that one of the main parameters is refrigerant charge amount which has a notable effect on COP.The temperature of the heat source was also tested and the performance of the system increased by more than 11% by employing mentioned modifications and various operating conditions.In addition,by selecting a low viscosity compressor oil,the system performance increased by 18%.This improvement is more than 6% for the case that cooling fan is installed to cool the compressor element.

Refrigeration Performance Analysis and Its Applicability of a New Metal Hydride Couple in Auto Air-conditioning

With COP and dynamic characteristics in refrigeration cycle as criteria,a new metal hydride couple——LaNi 4.61 Mn 0.26 Al 0.13 /La 0.6 Y 0.4 Ni 4.8 Mn 0.2 was selected by establishing calculation procedure and metal hydride selection model.The experimental results show that the refigeration cycle of the selected couple is good in the performance.The recovered waste heat and refrigeration power from exhaust gas of several kinds of automobile are calculated by waste-heat formula,coefficient R Q and COP.Refrigeration cycle of the new couple can satisfy the air-conditioning requirement of truck and car and is not enough in passenger car,according to the respective cooling load.

Experimental study on characteristics of transcritical heat pump water heater using refrigerant HFC125

To evaluate the performance of heat pumps using refrigerant HFC125,an experimental rig of a DC-inverter heat pump water heater is designed and set up,and the research on the transcritical heat pump water heater is carried out experimentally.It is found that there is a top value of the coefficient of performance（COP）when the system runs at 95 Hz of frequency.The relationships between the COP and compressor frequency,condensation pressure,evaporation pressure,condensation water temperature rise,and discharge temperature are discussed and analyzed at 95 Hz.And the COP of the HFC125 transcritical cycle is also compared with that of a R410 subcritical heat pump under the same conditions.The results indicate that there exists an optimum frequency for a better COP,and the system COP shows an increasing tendency with the decrease in condensation pressure and compressor ratio while the evaporation pressure remains invariant,and the COP decreases rapidly when cooling water temperature rises over 47.5 ℃.Compared with the R410A sub-critical cycle,the COP of HFC125 transcritical cycle significantly increases by 12% on average.

Parallel Operation Characteristics Analysis of Sewage Source Heat Pump Units in Winter

Sewage source heat pump unit operates under partial load most of the time, and study on the law of coefficient of performance (COP) of the unit varying with load ratio can provide basis for the heat pump units running in high efficiency. A mathematical model determining COP, evaporation temperature and condensation temperature of a single unit was proposed. Under the condition of uniform load distribution, the model was established according to different ways of bearing partial load with the same type multi...

Experimental investigation on the energy-saving diffuser of a main fan

The main fan diffuser in a coal mine is an energy-recycling equipment with a dynamic energy loss for the main fan. Engineering practices and related researches show that the body structures of three types of diffusers are irrational. To solve the problem, an energy-saving diffuser is designed on the basis of the velocity potential theory. Under conditions of inlet velocity from 7 m/s to 32 m/s, 7 condition experiments using the energy-saving diffuser of 2.31 AER （area-enlarging ratio） and 5 condi- tion experiments using the energy-saving diffuser of 2.00 AER were conducted. Through a comparative analysis of the experi- ments, the results show that the COP （coefficient of performance） of the energy-saving diffuser of 2.31 AER is better than that of the energy-saving diffuser of 2.00 AER.

The Efficiency Analysis of the Exhaust Air Heat Pump System

This paper is based on long term parameter measurements of the exhaust air heat pumps (EAHP) system in a new built apartment building. The building was equipped with an exhaust air ventilation system and exhaust air heat pump for ventilation heat recover. The results of the measurements show that the COP of the EAHP is mainly related to the temperature graph of the heating system and the supply temperature of domestic hot water (DWH). During the measurement period some other impact factors, such as the quality of maintenance, the nighttime temperature graph of the heating system, the reduction of the exhaust air flows in case of low temperatures, mistakes in designing and low building quality, have also played a role. An analysis of energy consumption shows that in winter conditions the COP is about 3.0 and in the transition period about 3.3. The energy recovery value of the EAHP is 0.5.

多台冷水机组联合运行系统的最佳性能系数(COP)

根据空调负荷连续性和冷水机组承担负荷非连续性的特点,以及冷水机组的性能系数(COP)与其部分负荷率R有关的特性,提出一种基于最佳COP的冷水机组负荷分配方法.采用回归方法获得冷水机组R与COP的关系并建立机组能耗目标函数,利用序贯加权因子法获得最佳的负荷分配率.将该方法用于多台冷水机组联合运行系统的在线运行控制.试验结果表明,该优化控制策略优于常规的负荷等额分配控制或区间负荷比例分配控制策略.

国标中的COP与EER

通过对中华人民共和国国家标准中的COP和EER对比研读,分析了国家标准中的COP和EER的术语解释。COP既用来表示单一的制冷性能系数或制热性能系数,也用来表示制冷及制热性能系数;EER则用来表示制冷能效比,且EER不是独立出现,与此对应的是用来表示制热性能系数COP。

基于部分结构参数的螺旋形Savonius风轮性能优化

90°扭角螺旋形Savonius风轮模拟结果与试验结果的对比,证明κ-ε模型具有较高精度。采用该模型对螺旋形Savonius风轮进行数值计算,深析螺旋角度θ、隔板数N、螺距P3个结构参数对风能利用系数的影响规律,并与传统直叶片Savonius风轮进行静力矩对比。结果表明:θ=180°,N=6和P=6.0的风轮在叶尖速比为0.75时达0.21;螺旋形Savonius风轮静力矩系数均大于0,比传统直叶片风轮具有更良好的启动性能。

制约离心式制冷机组COP值的参数分析

利用方差分析方法分析了制冷机组实际运行负荷比例、机组导叶开度、冷冻水出口温度以及室外空气相对湿度对离心式制冷机组COP值的影响。当置信概率分别取95%和99%时,一元方差分析表明,机组导叶开度的检验统计量F值高于临界值F0.01(r-1,n-r),证明其对机组COP影响十分显著;实际运行负荷比例、冷冻水出口温度的检验统计量F值高于临界值F0.05(r-1,n-r),说明对机组COP影响显著;室外空气相对湿度的检验统计量F值低于临界值F0.05(r-1,n-r),则对制冷机组COP影响不显著。同时对冷冻水出口温度和室外空气相对湿度进行二元方差分析表明,两者交互作用的检验统计量F值高于临界值F0.01((r-1)(s-1),rs(c-1)),则证明两者交互作用制冷机组COP影响显著。依据分析结果调整机组运行参数,在制冷量不变的情况下,机组运行的COP值平均提高6.885%。

基于COP与改进PNN的除湿机故障诊断研究

COP作为制冷系统中的重要性能参数,直接反映制冷系统的效率及运行情况。基于制冷系统的这一特点,以除湿机为例,建立了基于除湿机COP的改进PNN故障诊断模型,通过监测COP的实测值超出正常设定范围判断系统存在故障,进而对系统故障进行识别,诊断故障发生的具体原因。实例表明,该方法用于除湿机的故障诊断切实可行。

S形断桥式自保温砌块的强度和保温性能研究

对S形断桥式自保温砌块进行了传热系数的热工计算,对该自保温砌块砌筑的墙体进行了传热系数的现场测试。热工计算得到的传热系数为0.29 W/(m^2·K),实测值为0.33 W/(m^2·K)。该砌块的抗压强度为5.81 MPa,抗弯强度为1.11 MPa。研究结果表明:S形断桥式自保温砌块符合DB 375026—2014《山东省居住建筑节能设计标准》对外墙传热系数的要求,并且具有较好的力学性能。

Energy performance analysis of multi-chiller cooling systems for data centers concerning progressive loading throughout the lifecycle under typical climates

The increasing demand for cooling energy in data centers has become a global concern.Existing studies lack a comprehensive analysis of the energy performance of widely used multi-chiller cooling systems in air-cooled data centers throughout their lifecycle,especially concerning progressive loading.To bridge this gap,this study conducts a thorough assessment of the energy performance of multi-chiller cooling systems throughout the entire lifecycle.Additionally,the impact of climate conditions on the energy efficiency of the cooling systems is analyzed,considering design variations for typical climates.Multi-chiller cooling system models are developed using the test data of cooling equipment and typical control algorithms.The energy performance of the cooling system is thoroughly analyzed under full-range cooling loads and climate conditions.Results show that free cooling time could differ up to 1442 hours at different part load ratios in the same location.Furthermore,the cooling system’s coefficient of performance(COP)varies significantly,by up to 6,at different part load ratios,corresponding to a difference in power usage effectiveness(PUE)up to 0.14.Notably,the average cooling system COP throughout the lifecycle loading is found to be only 11.7,2.9 lower than the design system COP.

采用[bmim]Zn_(2)Cl_(5)/NH_(3)和NaSCN/NH3为工质的两级复叠吸收式制冷稳态特性

提出了一种以[bmim]Zn_(2)Cl_(5)/NH_(3)和NaSCN/NH3为工质的新型两级复叠吸收式制冷(TCAR)。基于系统部件的质量守恒,能量守恒和[火用]方程,对TCAR系统的热性能进行了数值研究。计算并分析了热源温度和冷媒水入口温度关键性能参数的影响。结果显示:TCAR系统的热性能优于两级吸收式制冷(TAR)系统,性能系数(COP)略低于热驱动压缩吸收式制冷(HACR)系统,但TCAR系统的热源温度低于HACR系统,且TCAR系统的结构比HACR系统简单得多。计算并比较了每个部件的[火用]损,发现发生器、冷凝器以及吸收冷凝器的[火用]损最大。

环境参数对回热空气制冷系统COP及能效最优压缩比的影响分析

为配合加强基加利修正案中氢氟碳化物的管控,环境友好型制冷空调系统的研究成为热点。针对以空气为工质的制冷系统,为研究系统性能系数(COP)及其达峰的最优压缩比,本文建立了回热直流高压空气制冷系统COP计算模型,探讨分析了环境温度、压力及相对湿度等参数对系统COP与能效最优压缩比的影响。结果表明:降低环境温度、增大环境压力可降低系统的能效最优压缩比并提高制冷COP,且环境压力升高可显著减少膨胀过程的凝冰量;环境空气相对湿度对能效最优压缩比及系统制冷COP影响较小。

纳米NiFe_2O_4与OLFs冷冻机油对往复式冰箱压缩机性能的影响

采用MINICER 993.0490分散机将纳米铁酸镍(n-NiFe_2O_4)和纳米洋葱状富勒烯(onion-like fullerenes,OLFs)添加到KFR22中制备出纳米冷冻机油。采用SRV(II)摩擦磨损试验机测试了该冷冻机油在冰箱压缩机工况下往复运动的润滑性能。依据SH/T0762-2005和GB/T5773-2004规定的测试方法和条件,对采用此纳米冷冻机油冰箱用往复压缩机性能进行了对比检测。结果表明:采用此纳米冷冻机油后压缩机的平均性能系数COP由1.5提高至1.58,增加5.3%。

S型桨叶捕能消波浮式防波堤仿真及试验研究

为了促进开放海域海养殖装备智能化、无人值守化发展,解决离岸养殖装备自主供能以及安全防护问题,针对所提出的Savonius型(S型)桨叶捕能消波式浮式防波堤,建立二维波浪数值水池,搭建物理水槽试验系统和海试系统,通过仿真和试验研究系统在不同结构参数下的水动力学特性,分析探究相对间距、相对入水深度、波陡对系统捕能消波性能的影响.研究结果表明:该防波堤系统能同时进行捕能和消波,其捕能性能随着波陡的增加而增加,在周期1.6 s时捕能效果最好;消波性能随相对间距的增加而变好,透射系数为0.2~0.8,消波效果显著.系统捕能与消波性能存在相互影响,多数情况下两者不能同时达到最佳.海试运行测试验证了该型防波堤的捕能消波效果.

变频冰箱压缩机用外转子PMSM的研究

为变频冰箱压缩机设计了一款外转子的永磁同步电机(PMSM),并基于二维有限元模型分析了转子壳体壁厚、磁铁厚度以及磁铁形状对电机性能的影响。样机实验结果表明,与常规内转子PMSM驱动的方案相比,由外转子PMSM驱动的变频冰箱压缩机具有能效高、成本低、质量轻、体积小的优点。

热泵干燥系统E_R及COP的实验研究

以三氟二氯乙烷（R123）为热泵工质，空气为换热介质，通过调节循环风速、辅助电加热和节流阀的开度，测定不同条件下的蒸发温度、冷凝温度和压缩机功率的冷量的有效利用率ER及COP。结果表明：在蒸发温度45℃、冷凝温度85℃、风速6m／s条件下，COP达到最大值3．3。在蒸发温度30—45℃、冷凝温度70～80℃，COP维持在2以上；在实验温度范围内，％最小为18．2％，蒸发温度23℃、冷凝温度80℃、风速2m／s时‰达到最大值71．5％。