Magnetic and magnetocaloric properties in melt-spun and annealed Ni42.7Mn40.8Co5.2Sn11.3 ribbons

The Ni_42.7Mn_40.8Co_5.2Sn_11.3 ribbons were prepared by melt spinning. After heat treatment, the martensitic transformation temperature and Curie temperature of austenite of the annealed ribbons increased remarkably. Inverse and direct magnetocaloric properties were investigated in the melt-spun and annealed ribbons. The effective refrigerant capacities for these ribbons were discussed in this paper.     

风冷机房专用空调安装探讨

主要从机房专用空调的选型及位置的确定、制冷剂管路的设计以及安装施工方法等方面进行阐述。     

Use of nanoparticles to make mineral oil lubricants feasible for use in a residential air conditioner employing hydro-fluorocarbons refrigerants

The application of nano-fluids in refrigerating systems is considered to be a potential way to improve the energy efficiency and reliability of HVAC&R facilities and to make economic the use of environment-friendly refrigerants. In this paper, we report a method that uses nanoparticles to enhance the energy efficiency of retrofitted residential air conditioners (RAC) employing HFCs as alternative refrigerants. The reliability and performance of RAC with nanoparticles in the working fluid have been investigated experimentally. A new mineral-based nano-refrigeration oil (MNRO), formed by blending some nanoparticles (NiFe₂O₄) into naphthene based oil B32, was employed in the RAC using R410a as refrigerant. A method showing how to disperse the NiFe₂O₄ nanoparticles in the mineral oil refrigeration lubricants is presented together with an investigation of their stability. The solubilities of the new MNRO in R134a, R407C, R410a and R425a were measured. The performances of the RAC, such as the cooling/heating capacity, the power input and the energy efficiency ratio, were determined. The results indicate that the mixture of R410a/MNRO works normally in the RAC. The cooling/heating EER of the RAC increased about 6% by replacing the Polyol-Easter oil VG 32 lubricant with MNRO.     

Comparison of low temperature mixed refrigerant cycles for separation systems

Numerous mixed refrigerant cycles (MRCs) were developed in the past several decades in different applications. In this paper, two sets of low temperature MRCs are developed and simulated for a typical olefin plant utilizing a mixture of methane, ethane, propane and nitrogen as cycle working fluid to replace the pure ethylene refrigeration cycle that is used in conjunction with propylene refrigeration cycle in conventional plants. The key parameters of the cycles including mixture compositions and operating pressure levels are optimized to meet the objective of minimum shaftwork in compressor. The results show that different cycle configuration has different optimal mixture composition and low and high operating pressures. The results of exergy analysis reveal that the main location of the exergy loss in the cycles is the heat exchanger system. Also, the Carnot factor versus heat flow diagram is provided to identify the distribution of inefficiencies in the heat exchangers for each cycle. The simulation results show that MRCs can improve the thermodynamic performance of refrigeration system using the optimal working fluid mixture composition, optimal high and low operating pressures and optimal arrangement of the cycle components. Copyright © 2008 John Wiley & Sons, Ltd.     

Effect of refrigerant charge on the performance of air conditioning systems

An air conditioning system operates in an optimal condition if the system is fully charged with a specified amount of refrigerant. Poor field maintenance or refrigerant leakage causes low level of charge resulting in a lower thermal performance and higher operating cost. An experimental investigation was conducted to study the effect of low charge level of R‐22 on the performance of a 3‐ton residential air conditioning system. The experimental results show that if a system is undercharged to 90 per cent then the effect is small: a 3.5 per cent reduction in cooling capacity and a 2 per cent increase in the coefficient of performance (COP). However, the system performance suffers serious degradation if the level of charge drops below 80 per cent. An ice layer formed on the outer surface of the cooling coil impedes the heat transfer between the warm air and cold refrigerant vapour. An economic analysis shows that the cost of properly charging an under‐charged system which is at an 85 per cent charge level, can pay for itself in savings in a short period of 3–4 months. Copyright © 2001 John Wiley & Sons, Ltd.     

浅谈TCE供应格局变化对我国HFC-134a行业的影响

随着全球经济形势的变化,先是金融危机冲击氯碱行业,国外TCE（三氯乙烯）装置纷纷减产或关停;再有国际氟化工公司战略转型,基础氟化工产品[1]（HFC-134a、低端PTFE等）生产向发展中国家转移;后是各国政府纷纷出台政策刺激经济,制冷剂需求持续升温,而其生产原料之一TCE供应格局却发生了翻天覆地的变化,本文详细分析原料TCE对下游HFC-134a行业的深远影响,提出制冷剂行业针对TCE供应格局变化的应对建议。     

AVR单片机氡室温湿度智能控制的方案设计与实现

介绍了一种新型的采用AVR单片机作为主控器的氡室温湿度智能控制系统,阐述了ATmega128单片机与温湿度传感器、氡室制冷系统和除湿系统等部件实现的软、硬件接口技术要点。通过对温湿度控制能力的理论计算,确定该套方案是可行的。该控制系统既可以独立完成对氡室温湿度的监控,也可以通过RS-232C接口与PC机通信,组成基于PC机的控制系统。     

New design of CHP for hypermarket of higher energy efficiency,less-fugitive refrigerant emissions and a remarkable reduction in initial and operating cost

High initial cost of power plant, limited power capacity of the existing plant and the frequent black out of many districts due to the continuous increase in electrical demands, in addition to the adverse effect of the blackout on hypermarkets, especially on foodstuff such as meat, chicken, etc. strongly encourage the adoption of a regenerating process and the principle of combined heat and power. This work investigates the upgrading of the combined cooling heat and power system and improving the regenerating process adopted in the first design of an existing project. Linking between refrigeration and air-conditioning systems is proposed in scheme-II. A single-effect absorption chiller operating in the range of refrigeration scale (i.e. aqueous-ammonia refrigeration, not air-conditioning scale, LiBr–H₂O employed in scheme-I) will be adopted using pressurised hot water recovered from the generators. The chilled water system will be serving three categories in the following order, namely, refrigeration stores, cold stores and air-conditioning units, respectively. The chilled water output of the first category will be the input of the second one. This will enhance the overall system efficiency, reduce the generator load and lessen the fugitive refrigerant emissions, which mainly participate in ozone-depleting potential and global-warming potential. This is in addition to the dramatic reduction in initial and operating cost, which can be estimated to be 50% and 79.6%, respectively.     

CO2/R170混合物作为复叠式制冷系统低温环路制冷剂的性能

针对CO2/R170混合物在复叠式制冷系统低温环路使用的工况，建立了固液平衡和汽液平衡的数学模型，决定了保证混合物在较低温度下不结晶的配比。在一定的配比范围内对混合物进行了循环性能和可燃性分析。研究了混合物配比对循环性能参数和可燃性的影响，以及中间温度在高温环路使用R290、低温环路使用CO2/R170混合物时，复叠式制冷系统整体制冷系数（COP）的变化趋势。研究表明，这种混合物适宜作为复叠式制冷系统低温环路的制冷剂。     

新型工质HFC161热物性计算研究

HFC161是近几年来国际上热物性研究关注的热点之一,作为制冷剂替代物,目前物性数据非常缺乏,公开发表的文献报告十分有限,基于制冷空调系统仿真的特点,以状态方程法建立了HFC161热力性质计算模块并进行了实用化的处理.计算结果与已公布的HFC161热物性参数数据进行比较,表明准确度能够满足工程计算的需要.