Experimental Study of Air Conditioning Unit of Evaporative Cooling Assisted Mechanical Refrigeration

The evaporative cooling,which assists the refrigeration machinery air-conditioning systems test-rig,has been designed.Its structure and working principle were described,and the performance test was conducted and analyzed.The test shows that making full use of the evaporative cooling "free cooling" in Spring and Autumn seasons can fully meet the requirements of air-conditioned comfort through the switch of the function in different seasons.Taking into account the evaporative cooling fan and pump energy consumption,compared with the traditional mechanical refrigeration system,more than 80 percent of energy can be saved,and the energy efficiency ratio of the Unit(EER)is as high as 7.63.Using the two stages of indirect evaporative cooling to pre-cool the new wind in summer,under the conditions of the same air supply temperature requirements,0.83 kg/s chilled water saved can be equivalent to the traditional mechanical refrigeration system,and when the new wind ratio up to 50 percent,more than 10 percent load was reduced in mechanical refrigeration system.The overall EER increased about 35 percent.

Entropy Assessment on Environmental Influence of Condense Heat in Recovery System in Air-Conditioning Refrigerating Machine

This paper presented an entropy evaluation method for the influences of condense heat recovery system on the environment.Aiming at the damage of the condense heat to the environment,an entropy of resource loss and an emission entropy from the condense heat recovery system in the air conditioning refrigerating machine were introduced.For the evaluation of the entropies,we developed a new algorithm for the parameter identification,called the composite influence coefficient,based on the Least Squares Support Vector Machine method.By simulation,the numerical experiments shows that the Least Squares Support Vector Machine method is one of the powerful methods for the parameter identification to compute the damage entropy of the condense heat,with the largest training error being-0.025(the relative error being-3.56%),and the biggest test error being 0.015(the relative error being 2.5%).

AIR CONDITIONING REFRIGERANTS AND OZONE PROTECTION

Until recently, CFC-11 and CFC-12 were the most widely used refrigerant gases in air conditioning systems. Environmental agencies around the world, however, have specifical concern for these gases as a direct cause of the depletion of the Earth’s ozone layer. Consequently, the world’s industrial nations are taking concerted action to decrease the use of CFCs, calling for attention of the engineers and designers involved in the manufacture and application of refrigeration systems for air conditioning. This paper analyses the available alternatives of CFCs in the industry and examines the problem found in process application.

Evaporative Condensers in Comfortable Air Conditioning System

The operating theory of an evaporative condenser was expatiated.The difference between an evaporative condensing refrigeration system and a general refrigeration system was analyzed.Compared with the air-cooled and the water-cooled,the virtues of energy-conservation and water-conservation of evaporative condensers were analyzed.Some questions existing in the application of evaporative condensers were pointed out,the corresponding solving methods were analyzed accordingly,and the development trend of evaporative condensing technique in mechanical refrigeration system field and the applied foreground of evaporative condensers in comfortable air conditioning were prospected.

Experiments on an Open-Loop Cycle Carbon Dioxide Refrigeration System

An open loop cycle carbon dioxide(CO2)refrigeration system is established,and the cooling performances of high-pressure CO2 under different storage conditions(25℃,30℃,and 35℃)are investigated.Moreover,the experimental mass flow rates of CO2 are compared with the theoretical values at different conditions and refrigeration capacities.The results indicate that the storage condition of CO2 has a significant impact on the refrigeration performance,and the mass flow rate of CO2 increases with the increasing storage temperature in a given refrigeration capacity.

Presence of Contaminants in Refrigerant and Their Effect on Refrigeration Cycle

Refrigerant is a medium used in refrigeration cycle. Until now in thermodynamic models calculations of refrigerant is not considered with lubricant and moist air but as an ideal pure gas （without any contaminants）. This is also the case in refrigeration cycle where the refrigerant is very often considered as an ideal one. Lubricant, air and water vapour are not considered in thermodynamic calculations in spite of their existence. The problems in the existing research are summarized. A further study is suggested on refrigerant systems. This circulation of such calculations is at the origin of a deviation from a theoretical behaviour. This article aims at reviewing the researches of oil-refrigerant, air-refrigerant, moist air-refrigerant or oil-moist air-refrigerant mixtures and focuses particularly on mixture enthalpy calculation. This paper deals with the description of the real mixture of refrigerant and contaminants （lubricant, water, moist air and other remains of refrigerants at elevated pressures and temperatures） which flow in a refrigerating cycle and the main point of this paper is to appoint thermodynamic parameters of such a mixture using the thermodynamic formulas.

Comprehensive approach to predicting the circulation composition of zeotropic refrigerants

The problem of composition shift in zeotropic fluid circulation, which is encountered in modern air conditioning and refrigeration systems, is studied. It reveals that the composition shift phenomena is contributed by fractionation related to four mechanisms. This paper concentrates on the modeling of component fractionation in heat exchangers. Element approach is employed, and the amount of each component holdup is calculated element by element with a proper void fraction model. The circulation concentration is determined from the refrigerant differential holdup in heat exchangers. Simulations are carried out to prove the validity. The results can improve the reliability and efficiency in zeotropic refrigerant applications.

Simulation of Air Source Heat Pump with Refrigerant Injection for Heating Operation

An air source heat pump(ASHP)with refrigerant injection is proposed for the air conditioning system of electric vehicles(EVs),especially for efficient heating in cold winter,when there is no wasted heat of engines.The simulation model is built with the framework of two-phase fluid network,where the compressor is separated as two compressors and the economizer is treated as two heat exchangers in the injection path and the main refrigerant path.With the validated simulation model,the heating performance is analyzed,and the results show that the coefficient of performance(COP)of ASHP with refrigerant injection is higher than 1.4 and the discharge temperature is less than 100℃ when the outdoor temperature is-20℃.The above performance ensures that the air conditioning system and EVs can operate normally with high efficiency even in the cold winter,which is much helpful for the practicability of EVs.

新型低GWP制冷剂在-100~200℃的应用研究进展

制冷剂是蒸气压缩循环中必不可少的工作流体,氢氟烷烃类化合物是目前制冷、空调和热泵设备中的主要制冷剂,但该类制冷剂会引起全球变暖等问题,因此亟需开发应用性能相似、环境性能友好的新型制冷剂。介绍了不同制冷剂在-100~200℃蒸气压缩循环应用场景中的使用现状,并综述了具有前景的低GWP制冷剂替代方案研究进展;在此基础上,对HFO-1234yf、HFO-1234ze(E)、HFO-1234ze(Z)、HCFO-1233zd(E)、HFO-1336mzz(Z) 5种低GWP制冷剂在实际应用系统中的最新研究及关键问题进行总结。

Simulation technology for refrigeration and air conditioning appliances

Simulation technology has been widely used for performance prediction and optimal design of refrigeration and air conditioning appliances. A brief history of simulation technology for refrigeration and air conditioning appliances is reviewed. The models for evaporator, condenser, compressor, cap- illary tube and thermal insulation layer are summa- rized, and a fast calculation method for thermody- namic properties of refrigerant is introduced in this paper. The model-based intelligent simulation tech- nology and the simulation technology based on graph theory are also illustrated. Finally, an updated trend of simulation technology development for refrigera- tion and air conditioning appliances is discussed.

不同冷藏条件下斜纹夜蛾卵对夜蛾黑卵蜂寄生的影响

【目的】夜蛾黑卵蜂(Telenomus remus)是草地贪夜蛾(Spodoptera frugiperda)的优势卵寄生蜂,而斜纹夜蛾(Spodoptera litura)是繁殖夜蛾黑卵蜂的优良寄主,明确斜纹夜蛾卵冷藏温度、时长对夜蛾黑卵蜂繁殖能力的影响,为草地贪夜蛾的生物防治提供参考。【方法】设置斜纹夜蛾卵不同冷藏温度(4、8、12℃)和冷藏时间(0、3、6、9、12 d),统计其对夜蛾黑卵蜂寄生率、羽化率和雌性率的影响。【结果】斜纹夜蛾卵不同冷藏温度和冷藏时间均能显著影响夜蛾黑卵蜂的寄生率、羽化率和雌性率(P<0.01),且随着斜纹夜蛾卵冷藏温度的下降和冷藏时间的延长,夜蛾黑卵蜂的寄生繁殖指标呈下降趋势。当冷藏温度分别为8℃或12℃、冷藏时间为3d时,夜蛾黑卵蜂寄生率、羽化率和雌性率分别为85.98%、94.71%、56.15%(8℃,3d)和85.49%、94.61%、60.00%(12℃,3d),与对照相比无显著差异(P>0.05),是最适宜的冷藏条件;当冷藏温度为12℃、冷藏时间为6d或9d时,夜蛾黑卵蜂寄生斜纹夜蛾卵受到显著影响(P<0.05),夜蛾黑卵蜂寄生繁殖受到一定影响,但仍可维持种群正常繁殖,可作为备选的冷藏条件。其他冷藏条件对夜蛾黑卵蜂寄生斜纹夜蛾卵有显著影响(P<0.05),不宜作为斜纹夜蛾卵的冷藏条件。【结论】生产上需短期冷藏斜纹夜蛾卵时,可选择冷藏温度8或12℃、冷藏时长3 d;冷藏时间更长时可选择12℃,但不应超过9d。

汽车空调制冷系统故障分析

以汽车空调系统为研究对象,针对汽车空调制冷系统故障进行分析研究。首先,对汽车空调系统及制冷原理进行了简要介绍;其次,结合汽车空调系统维修工作实际,对制冷故障的原因及表现,从机械故障、系统故障两个不同的方面,进行了分析与总结;最后,在上述研究的基础上,从几个不同的方面详细介绍了汽车空调制冷系统故障诊断方法。

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。

制冷与空调专业课程的课程思政教学实践

培养一流人才,既要高水平地传授专业知识,也要进行“立德树人”的全要素培养。课程思政教学是实现“立德树人”教育的重要途径。课程思政是时代要求,符合马克思主义教育哲学思想,契合先进的教育理念,也是中国优秀传统教育文化的传承。课程思政题材内涵十分丰富,各类专业课程应挖掘出与课程内容紧密贴合的富有特色的思政元素。制冷与空调专业课程制冷设备和空气调节工程的思政元素聚焦于能源的现状及发展、全球气候变暖、“双碳”战略和“中国制造”等题材,达到良好的思政教学效果。课程思政教学也应探索先进的教学方式,以达到满意的教学效果。

电臂尺寸和安装条件对热电模块力学性能的影响

针对热电制冷模块中热电臂尺寸对模块整体热应力场的影响,以C-31106型热电制冷模块为研究对象,建立由31对热电偶组成的热-电-力学耦合多物理场模型.采用有限元仿真方法,考虑钎料层的存在并引入表征黏塑性材料的Anand修正本构方程,建立3种安装条件下的热电模型,分析不同电流下热电臂高度和截面边长对热电模块温度场和力学性能的影响规律.结果表明,当热电臂处于最佳高度时,在给定范围内热电臂截面边长越大,越有利于提高热电模块力学可靠性,当工作电流为2.6 A,截面边长从0.99 mm增加到1.09 mm时,冷、热端的最大von Mises应力分别减小了74.67%和22.60%.对模块冷端和热端分别采用固定约束和机械压装的安装方式可有效提高热电模块的力学可靠性,当采用上述安装方式时,冷、热端的最大von Mises应力相比两端只采用固定约束的安装方式分别减小了48.76%和74.02%.

高职制冷专业科教融汇的实践探索

科教融汇是职业教育发展的新方向。其核心在于如何“融”、怎样“汇”。顺德职业技术学院制冷与空调技术专业在多年政校企合作、产学研结合的实践基础上,初步形成了“产品价值链-人才培养链-技术平台链-创新价值链”四链贯通的科教融汇模式,将人才培养与技术创新有效链接,既实现了教学与科研的协同发展,也实现了专业与产业协同发展。

“车辆制冷与空气调节”课程教学改革探讨

分析“车辆制冷与空气调节”课程的特点,并结合该课程在教学中存在的问题,探讨了在教学改革过程中采取的措施:整合教学内容、改进教学方法和手段、调整教学环节及加强实验室建设等。在师生共同努力下,课程教学得到了不断改进和优化,学生普遍反映课程内容设计合理、思政案例丰富、学习过程充实,自身专业素质和创新设计能力得到了提高,对人生观和价值观有了更加深入的思考,取得了良好的教学效果。

基于改进的粒子群优化算法的暖通空调制冷机房BIM自动优化布置方法

采用结合Revit API和MATLAB的编程模式,对Revit平台进行了有效的二次开发,从而实现了暖通空调制冷机房设备的自动化布置设计,不仅有效地实现了设备布置方案的自动生成,还支持了布置方案的预览与验证,显著提高了设计效率和准确性。该研究的创新之处在于成功将粒子群优化算法与BIM技术相结合,为暖通空调系统的自动化设计提供了新的视角,并验证了BIM在暖通空调领域正向设计中的应用潜力。

“制冷与空调”职业教育的模式探索与实践

结合中华人民共和国教育部对“制冷与空调”职业教育的相关专业简介的发布,以中高职衔接的制冷与空调技术专业(3+2学制)为例,提出“制冷与空调技术专业教学标准明确‘制冷与空调’学习方向、《制冷空调系统安装维修工》国家职业标准夯实‘制冷与空调’职业基础能力、《中华人民共和国职业分类大典》中制冷与空调工种作业标准拓展‘制冷与空调’职业发展能力、中华人民共和国第二届职业技能大赛中制冷与空调项目考核标准检验‘制冷与空调’职业应用能力”的思路,为制冷与空调技术专业教学模式提供一些参考。

高职制冷空调专业虚拟仿真教学资源的构建

针对当前高职制冷空调专业实训教学中存在的“三高三难”问题,提出了构建虚拟仿真教学资源的必要性,阐述了以学生为中心、实践为导向的建设思路,详细阐述了虚拟仿真教学资源的内容构建,包括制冷循环原理、制冷压缩机、冷库制冷装置、中央空调系统、CO_(2)制冷系统、冷链设备控制和冷链信息等方面的虚拟仿真实训系统,以及虚拟仿真资源教学管理平台软件,介绍了虚拟仿真教学资源在制冷空调专业课程教学中的应用效果,为专业数字化转型奠定了基础。