Experimental Investigation on the Performance of Heat Pump Operating with Copper and Alumina Nanofluids

In the present study,an attempt ismade to enhance the performance of heat pump by utilizing two types of nanofluids namely,copper and alumina nanofluids.These nanofluids were employed around the evaporator coil of the heat pump.The nanofluids were used to enhance the heat input to the system by means of providing an external jacket around the evaporator coil.Both the nanofluids were prepared in three volume fractions 1%,2%and 5%.Water was chosen as the base fluid.The performance of the heat pump was assessed by calculating the coefficient of performance of the system when it was operated with and without nanofluid jacket.A significant enhancement in the coefficient of performance was noticed when copper and alumina nanofluids were employed in the system.Also,the coefficient of performance was found to have a direct relationship with the tested volume fractions.For the highest volume fraction of 5%,the performance of the heat pump was found to enhance by 23%with alumina nanofluid,while for copper nanofluid,a very significant enhancement in performance by 72%was observed.Thus,utilizing of nanofluids in heat pumps can be very beneficial towards performance enhancement and the idea can also be extended to other thermal systems such as steam power plant,automobile radiator,industrial heat exchangers and refrigeration systems.

Stress concentration coefficients of optimized cope-hole welded detail

The fatigue performance of optimized welded detail has been investigated by fatigue experiments of three welded specimens under different loadings.In addition,local finite element models of this welded detail were established using finite element software ANSYS.The influences of different factors such as plate thickness,plate gap and initial geometric imperfections on the stress concentration coefficient(SCC) were discussed.The experimental results indicate that the fatigue life of three specimens for this welded detail is 736,000,1,044,200 and 1,920,300 times,respectively.The web thickness,the filler plate thickness and the initial geometric imperfection have relatively less effect on the SCCs of this welded detail.However,cope-hole radius is influential on the SCCs of the web and the weld.The SCC of weld is significantly affected by the weld size and plate gap,but the SCCs of other parts of the welded detail are hardly affected by the plate gap.

Experimental Evaluation of the Heat Output/Input and Coefficient of Performance Characteristics of a Chemical Heat Pump in the Periodic Operation of CaCl₂Hydration

We herein evaluate the use of a chemical heat pump (CHP) for upgrading waste heat. CaCl2 was used in the system of CHP. We evaluated the heat storage and heat releasing of CHP, and confirmed the practicality from the experimental results. The reactor module employed was an aluminum plate-tube heat exchanger with corrugated fins, and the CaCl2 powder was in the form of a packed bed. Heat storage operation and heat dissipation operation are performed at the same time and supplied to the heat demand destination. At this time, an environmental heat source can be used during the heat radiation operation, and the heat output can release more heat than the heat input during heat storage. The heat discharging and charging characteristics of the reactor module were evaluated experimentally. The coefficient of performance (COP) was calculated for the heat upgrading cycle, and the heat output in the system was determined. A COP of 1.42 and output of 650 W/L, based on the heat exchanger volume, were obtained using a 600 s change time for the heat pump.

Experimental investigation of thermal performance characteristics of sintered copper wicked and grooved heat pipes:A comparative study

Heat pipes are most frequently used for thermal management solutions.Selection of right type of heat pipe for a specific scenario is utmost necessary for best outcomes.The purpose of this research is comparison of thermal performance characteristics of sintered copper wicked and grooved heat pipes,which are mostly used types of heat pipes.Distilled water filled heat pipes were tested through experimentation in gravity assisted position.Experimental outcomes have been compiled in terms of capillary pressure,operating temperature,thermal resistance and heat transfer coefficient.Capillary pressure is high in sintered heat pipes compared to grooved heat pipes irrespective of groove dimensions.Grooved heat pipes have lower operating temperature compared to sintered heat pipes at the same heat load.At 8 W,compared to sintered heat pipes,grooved heat pipes have 8.24% lower condenser surface temperature,4.41% lower evaporator surface temperature and 7.79% lower saturation temperature.Thermal resistance of sintered heat pipe is much lower than grooved heat pipe.The maximum relative difference of 63.8% was observed at 8 W.Heat transfer coefficient of sintered heat pipe was observed double compared to grooved heat pipe at 8 W heat load.Thermal resistance and hence heat transfer coefficient of sintered heat pipe change almost in a linear manner with respect to heat load but unexpectedly turning point is observed in thermal resistance and heat transfer coefficient of grooved heat pipe.Grooved heat pipes attain equilibrium much earlier compared to sintered ones.Varying heat loads from 4 to 20 W causes variation in equilibrium establishment time from 7 to 4 min for grooved and from 10 to 7 min for sintered heat pipes.

Off-Design Performance Analysis of Axial Flow Fan in Helicopter

A theoretical calculation method of off-design performance is developed for an axial flow fan of oil cooling system in helicopter,including calculation of aerodynamic parameters and performance parameters.When calculating inlet shock loss,the shock loss coefficient is obtained by comparing results of theoretical calculation,experimental and numerical calculation.The theoretical results and numerical results show that all air velocity components increase from hub to shroud in main flow area at rated condition.Tip leakage vortex moves downstream as flow rate increases.When flow rate decreases,Re decreases,and boundary layer thickness from hub to shroud area all increases gradually.Tip leakage vortex moves upstream,and secondary loss increases.Low speed area in the passage is widened along with high speed area moving to hub area,influenced by boundary layer separation.Consequently wake area and jet area at fan outlet are both larger than rated condition.Therefore optimization design for off-design performance of the fan is required on aerodynamic parameters influencing fan loss.A reliable method is supplied for estimating altitude performance of lubricating system in helicopter.

Establishment of a Model for the Calculation of the COP of a Solar Adsorption Refrigerator

This paper deals with the evaluation of the Coefficient of Performance (COP) of solar adsorption refrigeration. In the literature, simulation models to predict the thermal behaviour and the coefficient of performance of these systems are uncommon. This is why we suggest a model to simulate the operation of the machine in a typical hot and dry climate of the city of Ouagadougou. The objective is to provide a model for calculating the COP from the measurement of the ambient temperature and the irradiation of a given site. Starting from mathematical modelling, a resolution and simulation were made with COMSOL software based on the Dubinin-Astakhov adsorption model, the heat transfer balance equations, and the Linear Driving Force (LDF) model to describe the thermal behaviour of the system. A one-week measurement sequence on the adsorption solar refrigerator at the Albert Schweitzer Ecological Centre (CEAS) validated the numerical results. The measurement shows that for the days with high sunshine, the temperature of the reaction medium reaches 110°C, and the pressure reaches 500 mbar. This leads to a production of cold that allows it to reach the temperature of -5°C at the evaporator. Under these conditions, the COP is worth 14%. These results are obtained both by numerical simulation using the COMSOL 5.1 software and after a measurement session on the solar refrigerator available to the CEAS. We obtained an experimental and theoretical coefficient of performance varying between 9% and 14% with a difference of between 0% and 3%. We conclude that our model is suitable to estimate the COP of any device based on its thermal properties, the ambient temperature and the irradiation of a given site.

Molecular characterization of a peanut variety and its derivatives based on SSR and COP analysis

Despite the economic importance of the peanut, no studies have been carried out to deter-mine the correlation between genetic distances based on molecular markers and on coefficient of parentage （COP） data. In this study, simple sequence repeat （SSR） and pedigree data were used to assess the ge-netic distance between the Fuhuasheng variety and its derivative cultivars. A total of 39 SSR polymor-phism primers were used, and 151 bands were obtained, with an average of 2. 04 bands in each primer. The genetic SSR - based distance （GD） values ranged from 0. 02 to 0. 81, while the COP - based GD ranged from 0. 25 to 0. 98. Certain Fuhuasheng loci displayed higher transmission rates. These loci or nearby chromosomal regions might be associated with desirable traits in Fuhuasheng variety, thus being frequently selected in breeding programs. Therefore, it can be suggested that COP analysis should be the preferred method for estimating genetic diversity invarieties with available complete pedigree information and parents. In this case, marker analysis would provide the best estimations.

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。

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%。

吸收式热泵COP影响因素修正曲线的试验确定方法

受汽轮机组运行工况、外网供热需求变化等因素影响,试验工况下热泵运行参数往往会偏离设计工况要求。制造厂家一般只给出设计工况下COP值,缺乏相应参数的修正曲线,或只给出一些经验值,难以对其进行准确修正,试验结果不利于热泵的性能考核验收。介绍了影响热泵COP相关参数的试验控制方法,提出了COP修正曲线的试验确定方法,成功应用于某300MW供热机组循环水余热利用工程试验测试中。首次给出了相关参数COP修正曲线的试验测试值,对类似工程的性能考核验收具有工程借鉴价值。

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.

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。

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。

行业和地方标准中的COP与EER

通过中华人民共和国行业标准和地方标准中有关COP和EER的研究,分析了行业标准和地方标准中的COP和EER的术语解释和其他条文涉及的COP、EER的解读。行业标准中COP表示为制冷性能系数,而EER为制冷能效比或冷源系统能效系数;地方标准中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用来表示制冷或制热能效比。

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％。

Assessment of Operational Performance in a Power Generation/Selling Integrated Company Using a Dynamic Proportional Adjustment Coefficient

Currently,the operational performance assessment system in the power market primarily focuses on power generation and electricity retail companies,lacking a system tailored to the operational characteristics of power generation/selling integrated companies.Therefore,this article proposes an assessment index system for assessing the operational performance of a power generation/selling integrated company,encompassing three dimensions:basic capacity,development potential,and external environment.A dynamic proportional adjustment coefficient is designed,along with a subjective and objective weighting model for assessment indexes based on a combined weightingmethod.Subsequently,the operational performance of an integrated company is assessed using extension theory.The results in the case study demonstrate the feasibility and effectiveness of the proposed dynamic proportional adjustment coefficient.

布雷顿与斯特林联合循环ECOP性能分析

以反映热机循环输出和损失之比的生态学性能系数ECOP为目标,用有限时间热力学的方法分析了具有热阻、热漏的布雷顿与斯特林联合循环的性能;导出了在牛顿传热律下布雷顿循环的ECOP的解析式,并通过数值算例得到了它们之间的关系;分析并研究了各种参数对联合循环性能的影响。

基于气隙式膜蒸馏的溴化锂吸收式制冷系统COP的优化

针对传统的溴化锂吸收式制冷系统难以利用低品位热源的问题,将气隙式膜蒸馏(AGMD)技术引入到溴化锂吸收式制冷系统中,是使其能够利用低品位热源的一种新的工艺流程。本文根据已有的1H,1H,2H,2H-全氟癸基三乙氧基硅烷(FAS)-Al2O3管式复合膜的膜蒸馏性能数据,对典型的基于AGMD的溴化锂吸收式制冷系统进行了热力计算。结果发现制冷系统的性能系数(COP)值较小,仅为0.280,因而需要对其工艺流程作进一步的优化。经热力学分析确定了优化的方案:在膜发生器浓溶液出口处增加回路,从而改进了原制冷系统的工艺流程。研究结果表明,制冷系统的COP值会随着回流比的增大而增大。当回流比达到8时,COP值可达到0.765,相较于改进前的系统增大了1.74倍,大大改善了制冷系统的性能。

Coefficient of Performance at Maximum χ-Criterion for Feynman Ratchet as a Refrigerator

The χ-criterion is defined as the product of the energy conversion efficiency and the heat absorbed per unit time by the working substance [de Tom′as et al., Phys. Rev. E 85(2012) 010104(R)]. The χ-criterion for Feynman ratchet as a refrigerator operating between two heat baths is optimized. Asymptotic solutions of the coefficient of performance at maximum χ-criterion for Feynman ratchet are investigated at both large and small temperature difference. An interpolation formula, which fits the numerical solution very well, is proposed. Besides, the sufficient condition for the universality of the coefficient of performance at maximum χ is investigated.

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.