Modelling of capillary tubes behaviour with HCFC 22 ternary alternative refrigerants

In this paper, a numerical model is presented for predicting capillary tube performance using new ternary mixtures proposed as alternatives to R 22. The model has been established after the fluid flow conservation equations written for a homogeneous refrigerant fluid flow under saturated, subcooled and two- pase conditions. Numerical results showed that the proposed model in question fairly simulated experimental on ternary refrigerant mixtures and fairly predicted the capillary tube behaviour under the investigated; subcooled, saturated, and two-phase flow conditions. © 1998 John Wiley & Sons, Ltd.     

Performance of some zeotropic mixtures as alternative refrigerants to R22 and R502

Many zeotropic refrigerant mixtures are being proposed as alternatives to CFCs and HFCFs refrigerants that are being phased out. The main advantage in the use of zeotropic mixtures is the possibility of reduction in entropy generation in the condenser and evaporator by matching the glides of refrigerant and heat transfer fluid. Glide matching is difficult with some zeotropic mixtures due to the nonlinear variation of enthalpy with temperature during phase change. Also, there is a distinct possibility of formation of pinch points with some mixtures, resulting in entropy generation. In this paper, the performance of four mixtures of R32, R134a, R125, R143a and R23 are studied as alternatives to R22 and R502 from thermodynamic as well as temperature pinch points of view. The results demonstrate the importance and the need for pinch point analysis in the evaluation of alternative zeotropic refrigerant mixtures. © 1998 John Wiley & Sons, Ltd.     

Performance assessment of heat pumps using HFC125/HCs mixtures

The analysis of heat pump cycles with and without an internal heat exchanger (IHE) is carried out in the paper, in which HFC125/HCs binary mixtures are used as the alternative refrigerants. And the cycle performance under different operation conditions is also compared. The results show that when the mass fraction of HFC125 ranges from 10 to 20%, the coefficient of performance (COP) for HFC125/HC290 (M1) mixtures is 0.92 and 1.01% lower than that of HCFC22 and HFC134a, respectively. For HFC125/HC600 (M2) and HFC125/HC600a (M3) mixtures, the COPs are higher than those of HCFC22 at the mass fraction of HFC125 between 0 and 74.1%, 0 and 66.5% in the mixtures, respectively, and compared with HFC134a, the COPs and volumetric heating capacities are higher when the mass fraction of HFC125 is between 38.6 and 73.3%, and 30.8 and 66%, respectively. For HFC125/HC1270 (M4) mixtures, the COPs are always lower than those of HCFC22 and HFC134a. It is also found that the IHE has a slight effect on the COPs with varying the mass fraction of HFC125 in the binary mixtures. The results obtained can provide some useful guidelines for the choice of alternative refrigerants. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance of alternative refrigerants for residential air-conditioning applications

In this study, performances of two pure hydrocarbons and seven mixtures composed of propylene, propane, HFC152a, and dimethylether were measured to substitute for HCFC22 in residential air-conditioners and heat pumps. Thermodynamic cycle analysis was carried out to determine the optimum compositions before testing and actual tests were performed in a breadboard-type laboratory heat pump/air-conditioner at the evaporation and condensation temperatures of 7 and 45 °C, respectively. Test results show that the coefficient of performance of these mixtures is up to 5.7% higher than that of HCFC22. While propane showed a 11.5% reduction in capacity, most of the fluids had a similar capacity to that of HCFC22. For these fluids, compressor-discharge temperatures were reduced by 11–17 °C. For all fluids tested, the amount of charge was reduced by up to 55% as compared to HCFC22. Overall, these fluids provide good performances with reasonable energy-savings without any environmental problem and thus can be used as long-term alternatives for residential air-conditioning and heat-pumping applications.     

Study of viscosity and thermal conductivity effects on condensation characteristics of some new alternative refrigerant mixtures

In this paper, a numerical study of the impact of the transport properties on the condensation characteristics of certain refrigerant mixtures is presented. New correlations have been developed to calculate the thermal conductivity and viscosity of some alternative refrigerant mixtures such as R-507, R-404A, R-407C, and R-410A. In addition, new improved condensation correlations have been developed and presented for predicting the heat transfer coefficient and pressure drop. The results clearly showed that the condensation characteristics were well predicted using the newly proposed correlations with mean deviation of ±10 and 20% for the heat transfer coefficient and pressure drop respectively. Copyright © 2002 John Wiley & Sons, Ltd.     

Permeation characteristics of hydrogen through palladium membranes in binary and ternary gas mixtures

The permeances of two palladium (Pd) membranes in pure H₂, binary and ternary gas mixtures are investigated experimentally. With 10% of gas impurities (N₂, CO₂, or CO) in H₂, the profiles of dimensionless permeance suggest that H₂ permeation rate is lessened by approximately 50% to 90%, and the permeance reduced by the gas impurities is ranked as CO > CO₂ > N₂. By introducing a parameter of permeance resistance, which is the reciprocal of permeance, the permeance resistance in a ternary gas mixture can be predicted from the summation of individual permeance resistances in binary gas mixtures, revealing no synergistic effect exhibited from the interaction of contaminants. At least 75% and up to 100% of H₂ in the gas mixtures can be recovered in the membrane system, and the maximum H₂ recovery develops at the H₂ partial pressure difference of 2 or 3 atm. In the Arrhenius‐type equation describing the relationship between the permeance and temperature, the activation energy is between approximately 2 and 18 kJ mole^?1. In general, the permeances of the membranes in gas mixtures, especially in ternary gas mixtures, are more sensitive to temperature when compared with those in pure H₂, stemming from lower activation energy exhibited. Copyright © 2017 John Wiley & Sons, Ltd.     

Manufacturing productivity and energy efficiency: a stochastic efficiency frontier analysis

This paper presents a mathematical model to estimate both production frontier and energy demand frontier, and evaluate the energy efficiency in the automotive manufacturing sector using plant‐level production and utility consumption data. By using the stochastic frontier analysis, two models—an output efficiency model (production frontier) and an input efficiency model (energy demand frontier)—are developed to analyze the plant's energy efficiency performance relative to the ‘best practice’ among peers. Both the structure and parameters of two stochastic frontier functions are identified to understand the relationship between production inputs (e.g., utilities and plant‐specific variables) and the overall productivity. A case study of a set of automotive engine manufacturing plants is conducted and shows that electricity has higher efficiency than other forms of utility in those production‐related activities, and the regional and climate factors have significant impacts on energy efficiency. The models provide a way to measure how far from the production frontier as well as how far from the energy demand frontier the plant is. The results also provide useful information about the inefficient energy components in manufacturing facilities. The opportunities of improving plant‐level efficiency in automotive manufacturing plants can be revealed by the results. Copyright © 2015 John Wiley & Sons, Ltd.     

Energy efficiency of a solar drying system

A solar collector, part of a drying system using solar energy as a heat source, was developed and reported previously and used in product-drying applications. In this study, energy efficiency analyses of the drying system in terms of the collector efficiency were investigated. The results obtained show that the present collector used in this solar drying system is an efficient and effective unit for practical drying applications.     

储能在能源安全中的作用

世界各国在积极发展可再生能源,而很大部分可再生能源用于发电.因此“能源安全”的范畴与重心将从20世纪的以石油安全为主逐步转向21世纪的以电力安全为主.确保安全、高质量供电,同时维持电力供需平衡是电力系统面临的持续挑战.发展新能源电力为常规电力机组的变负荷能力提出新的挑战:要求电力机组具备更快的变负荷调节能力;电力机组变负荷目标的不确定性增大;电力机组负荷调节范围更大.在电力系统中采用集成储能模块是解决电力系统变负荷和新能源电力接人产生问题的有效措施.储能总的作用是实现新能源电力上网、保持电网高效安全运行和电力供需平衡.储能系统的具体功能有三种:提高电能质量、提供桥接电能、能量管理.电力储能技术有抽水蓄能技术、压缩空气储能技术、超导储能技术、超级电容器储能技术、电化学储能技术、复合储能技术.对我国发展储能产业提出以下建议:从宏观战略层面制定储能发展规划;出台利于储能技术产业化的激励政策与机制;发布储能相关技术标准和管理规范,建立储能装置回收管理机制;加强储能技术研发与示范;建立储能产业链,降低成本;探索优化商业运营模式,加快储能技术的市场化步伐.     

世界环境可持续指数发布

评估世界各国和地区环境质量的“环境可持续指数”今年1月底在瑞士达沃斯正式对外发布。今年，在接受调查的144个国家和地区中，芬兰环保状况全球最佳，名列榜首。     

Energy analysis of a CO2 recycling system

In this report, a CO₂ recycling system is proposed and designed for the purpose of CO₂ mitigation through utilization of natural energy (photovoltaic power generation). The materials for construction and unit requirements of this system are quantified and also an energy analysis is performed as one of life‐cycle analysis (LCA) of this system. Concrete required for the foundation of the facilities is the largest material requirement and accounts for 62 per cent of the total amount of materials for building this system. The energy consumption needed to build the photovoltaic (PV) power generation facilities represents the largest fraction of energy consumption and accounts for 82 per cent of the energy consumption needed for building of plants. The energy balance ratio of the system is approximately 1.85. It clearly reveals that this system would be an effective way to utilize natural energy. Copyright © 2000 John Wiley & Sons, Ltd.     

计算机显示器能效标识制度与能效测试

在计算机显示器能效标准和能效测试的基础上,通过分类统计的方法,分析了被测显示器的能效等级和能效指标的分布,讨论了计算机显示器的能效水平和制约因素,说明能效标识制度的实施促进了计算机显示器的节能进程,并对其节能技术创新具有一定的指导意义。     

Influence of magnetic field on two‐phase flow convective boiling of some refrigerant mixtures

In this paper, an experimental study on the influence of magnetohydrodynamic (MHD) on heat transfer characteristics of two‐phase flow boiling of some refrigerant mixtures in air/refrigerant horizontal enhanced surface tubing is presented. Correlations were proposed to predict the impact of MHD on the heat transfer characteristics such as average heat transfer coefficients, and pressure drops of R‐507, R‐404A, R‐410A, and R‐407C in two‐phase flow boiling inside enhanced surface tubing. In addition, it was found that the refrigerant mixture's pressure drop is a weak function of the mixture's composition. It was also evident that the proposed correlations for predicting the heat transfer characteristics were applicable to the entire heat and mass flux, investigated in the present study. The deviation between the experimental and predicted value using new and improved correlations for the heat transfer coefficient and pressure drop were less than ±20%, for the majority of data. Copyright © 2005 John Wiley & Sons, Ltd.     

Influence of Tube's Diameter on Boiling Heat TransferPerformance in Small Diameter Tubes

INTaoDUCTIONReclitlydry-troeeVaPoratorofairconditioningmaChineandreffigeratorhavebeendevefoPinginthedirectionofusingsmalldiamtertube.TheHITACHICo.conductedaserlesofeVaPoratfonhe8ttransferexperimeats,usingthethinwallcoppertubesofinnerdiamter9.52nun,8mm,7mmand5nunre-spectivelytheworkingmediawasHCFC22(qualityx=o.6)I'].TheresulthasshoWnthatheeVaPo-rationheattransfercoefficielltsweresghcatlyincreasedwiththedecreasingoftubediameter.EVaThorationheattransfercoefficientofa5.onuninnerdiare…     

Influence of Tube‘s Diameter on Boling Heat Transfer Performance in Small Diameter Tubes

This paper reports the experiments of evaporation study in 6 mm inner copper diameter tubes using HFC-134a, HCFC-22 and CFC-12 as working fluid. The results show that the evaporation heat transfer coefficient increases with the decreasing of inner diameter of tubes. A new concept of non-dimensional tube diameter U is proposed in this paper for correction of the influence of the tube diameter on the evaporation heat transfer coefficient. And further, a convenient empirical correction method is presented.     

电能替代应用及效益评价

结合高校生活热水供应系统来具体量化电能替代所带来的经济效益和环境效益,同时在此基础上,结合较成熟的评价方法,对高校生活热水供应系统电能替代的效益进行全面的量化评价.计算结果表明,考虑环境效益的计算模型更贴近实际,评价结果更合理,为进一步推广电能替代技术提供了参考.     

21世纪中国能源发展趋势展望

通过对中国能源结构现状数据和非常规能源潜力的分析,叙述了中国到2050年进入中等发达国家水平的过程中,煤炭、石油等常规能源所占能源总量比重将逐渐下降,非常规能源所占比重将逐渐上升,逐渐成为替代能源乃至主导能源的发展趋势。     

我国煤液化燃料替代石化能源的开发与应用

本文介绍了我国石油能源供需紧张状况,煤液化燃料的开发及替代能源应用现状。开发煤液化燃料产品,构建能源多元化结构,势在必行。     

Behaviour of ternary blends in heated suction accumulator

The results of an experimental study on the behaviour of azeotropic ternary refrigerant mixtures in heated suction accumulator are presented. The experiment set up was composed of a fully instrumented air‐source heat pump with a capacity of 36 000 BTUH and equipped with a heated suction accumulator. Standard test conditions were used at the condenser inlet; however, the refrigerant temperatures were varied at the evaporator entrance from 2 to −40°C, to simulate various conditions encountered in extreme air‐source heat pump applications. The primary parameters observed during the course of this study were mass flux, heat flux, and quality, evaporator and condenser thermal capacities, and power consumed and pressure ratios for the azeotropic refrigerant mixtures under investigation. The test results showed that heated suction accumulators enhance the evaporation of the more volatile component of ternary azeotropic refrigerant mixtures. Thus, increasing the mixture thermal capacity as well as the coefficient of performance (COP). Furthermore, experiments have also shown capacity increases of 27% with heated accumulator over unheated accumulator at −30°C outside air temperatures. Copyright © 1999 John Wiley & Sons, Ltd.