活塞制冷压缩机的故障分析及维护保养

制冷装置设备中比较容易出现故障的是制冷压缩机,因其需要长时不间断的机械运动,在进行机械运动的过程中则会因接触摩擦而磨损或损坏;此外,压缩机零部件较多,更多类型的故障也接踵而至。近年来因操作使用不当导致的压缩机发生故障和出现事故屡见不鲜,因此本文基于制冷压缩机的使用现状就其在使用过程中会出现的故障进行分析,并介绍相应有效的维护保养之道。

高新科技全新节能环保空调雪种HCR-22碳氢制冷剂的应用分析

近几年，全球环境不断恶化，人类正在经历一场前所未有的环境危机。究其原因，人类无度的排放是造成大气臭氧层破坏的主因之一。为了保护臭氧层，保护人类的健康，联合国环保组织早在1987年就在加拿大蒙特利尔市召开会议，36个国家和10个国际组织共同签署了《关于消耗大气臭氧层物质的蒙特利尔议定书》。我国1992年正式宣布加入修订后的《蒙特利尔议定书》。该议定书对制冷剂的使用作了明确的限定。很显然，制冷剂的替代在中国已是一项迫在眉睫的问题。文章所谈及的碳氢制冷剂HCR-22是一种适用于以前使用HCFCR22或CFCR502的空调系统与低温冷冻的天然有机溶液。

制冷季黄浦江水温变化及水源热泵机组能耗分析

利用实际工程项目获取的室外气象参数及黄浦江水温数据,分析上海地区制冷季室外温度与江水温度的变化,并通过逐日数据计算分析比较了江水源热泵机组与常规冷源机组的能耗,结论显示在制冷季中江水源热泵机组有一定的节能优势,但节能效果并不显著。

太阳能空调系统性能分析

本文对太阳能高效平板集热器与热水型一级溴化锂吸收式制冷机及热水型两级溴化锂吸收式制冷机组成的空调系统进行了计算分析。结果表明 ,在热水温度为 82 - 95℃的范围内 ,太阳能一级溴化锂吸收式制冷系统具有较高的效率 ,但系统效率随热源温度的下降而急剧降低 ;在热源温度为 65- 82℃的范围内 ,太阳能两级溴化锂吸收式制冷系统具有较突出的优越性 ,系统效率几乎不随热源温的变化而变化。因此 ,两级溴化锂吸收式制冷机与太阳能平板集热器有比较好的匹配性能。

实用制冷空调软件的开发

本文介绍了两个windows实用软件,一个是湿空气性质分析实用软件另一个是制冷循环分析实用软件。软件用Visual C++6.0编制,具有操作方便、精度高的特点。

永川煤矿-350m水平掘进工作面降温技术分析

结合永川煤矿热害情况和现场实际条件,通过对比分析多种降温措施,得出永川煤矿宜采用回风排热的冷风制冷系统进行热害治理。本文详细介绍了该系统在矿井实际条件下的组成和应用方式,并对制冷系统的结构和设计参数进行了进一步分析,为同类型的矿井局部制冷降温系统的实施提供参考。

南海某文化中心地下商业空调冷却塔免费供冷经济性分析

地下商业存在全年空调冷负荷,对冬季和过渡季空调采用冷却塔免费供冷技术,在经济上是否可行进行了研究。通过分析夏热冬暖地区全年湿球温度分布情况、冷水的供冷温度、新风供冷能力,提高冷却塔冬季和过渡季供冷小时数,得出冷却塔免费供冷的节能经济性。采用冷却塔免费供冷技术可以实现商业建筑运营降低空调运行成本的目的。

Performance analysis of aircraft low-power thermoelectric refrigeration system

An optimal design method for an aircraft low-power thermoelectric refrigeration system（TRS）is proposed using an existing experimental model as the research platform under given aircraft flight conditions.The variation curves of the cooling capacities and the refrigeration coefficients of the system running at three flight altitudes are investigated.The performance of the system is evaluated by the minimum-entropy-generation method and the performance penalty is also calculated.The power variation curves of the cooling system are obtained by an electric power experiment.The peak values of these curves are less than the maximal electric power supply of airborne equipment,proving that the use of the low-power TRS for airborne equipment is feasible.The COP,cooling capacity and entropy generation of the system are relative to the flight altitude and the current of the TRS.Through the analyses of these data,the optimal values of the COP are obtained,and the optimization measures are proposed to maximize the use of the advantages of the TRS.

在Visual C++6.0中利用DLL实现层次型编程技术及应用

介绍了DLL技术在Windows编程中的基本运用方法及应用 ,并结合武汉科技学院课题“制冷循环分析软件的开发” ,对软件工程中分散分模块实现全部目标提出了探讨。

Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system

This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES) system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.

Numerical Modeling of the Performance of R22 and R290 in Adiabatic Capillary Tubes Considering Metastable Two-Phase Region——Flow Characteristics and Parametric Analysis of R22 and R290

Characteristics of R22 and its new alternative refrigerant R200 flowing through adiabatic capillary tubes are investigated based on the homogeneous model. Extensive flow variables along tube length such as pressure, temperature, viscosity, velocity. Reynolds number, friction factor and vapor quality etc are compared between the two fluids under the same operating condition. Two cases are considered, namely, either the same tube length or the same mass flow rate as inlet condition. The results show that the mass flow rate in the capillary tube of R290 is 40% lower than that of R22 due to the differences of physical properties between the two fluids. Further. a parametric analysis is performed and it appears that effects of geometric and thermodynamic parameters on mass flow rate of R290 are weaker than that of R22. When the condensing temperature is increased from 40℃ to 50℃ C. the mass flow rate for R22 is increased by 16%. while the increasing rate for R290 is 13%.

Effects of Collagen Peptide from Cyanea nozakii on Mouse Immune Function

[Objective ] The study aimed to provide a theoretical basis for the clinical application of collagen peptide from Cyanea nozakii. [ Method] After acute toxicity test on mice, collagen peptide from C. nozakii were given to mice by continuous intragastric administration for 30 d at the doses of 25, 50, 100 mg/kg, and then the phagocytosis of macrophage, delayed type hypersensitivity （DTH） and serum hemolysin level were determined. [ Result] Collagen peptide from C. nozakii was atoxic or low toxic, and the three immune indices of experimental groups were signifi- canUy higher than those of the control group （treated with same volume of normal saline） at 0.05 or 0.01 level. E Conclusion] Collagen peptide from C. nozakii has a certain immunopotentiation.

Cooling of Superheated Refrigerants Flowing inside Tubes Filled with Porous Media： Study of Heat Transfer and Pressure Drop, Carbon Dioxide Case Study

In this work an experimental study combined with an analytical investigation for cooling superheated Carbon Dioxide （CO2） gas were carried out. This work is intended to be part of the super critical Gustav Lorentzen refrigeration cycle of CO2. Experimental and analytical works concentrated on heat transfer and pressure drop for single phase flow during gas cooling inside tubes filled with porous media. Analytical empirical correlations were formulated for the coefficient of convectional heat transfer and for the pressure drop. A comparison between experimental results and that obtained by developed correlations were carried out, and a comparison between these results and literature published ones were carried out too. The results of this research showed that for cooling process the proposed correlations were proved to be acceptably accurate for pressure drop with difference from experimental results of 2%, while for convective heat transfer the difference from experimental results reached about 3%. More than 90% agreement with literature results was obtained. This work can enhance the calculations of heat flux and pressure drop of gases flow inside porous media filled tubes, and can help in the design procedure of heat exchangers and cooling processes.

Second Law of Thermodynamics Analysis of Transcritical Carbon Dioxide Refrigeration Cycle

In order to identify the locations of irreversible loss within the transcritical carbon dioxide refrigeration cycle with an expansion turbine, a method with respect to the second law of thermodynamics based on exergy analysis model is applied. The effects of heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures on the exergy loss, exergy efficiency and the coefficient of performance (COP) of the expansion turbine cycle are analyzed. It is found that the great percentages of exergy losses take place in the gas cooler and compressor. Moreover, heat rejection pressures, outlet temperatures of gas cooler and evaporating temperatures have strong influence on the exergy efficiency, COP and the exergy loss of each component. The analysis shows that there exists an optimal heat rejection pressure corresponding to the maximum exergy efficiency and COP, respectively. The results are of significance in providing theoretical basis for optimal design and the control of the transcritical carbon dioxide system with an expansion turbine.

Thermodynamic Analysis and Comparison on Low Temperature CO_2-NH_3 Cascade Refrigeration Cycle

This paper is focused on the cascade refrigeration cycle using natural refrigerant CO 2-NH 3. The properties of refrigerants CO 2 and NH 3 are introduced and analyzed.CO 2 has the advantage in low stage of cascade refrigeration cycle due to its good characteristics and properties. The thermodynamic analysis results of the CO 2-NH 3 cascade refrigeration cycle demonstrates that the cycle has an optimum condensation temperature of low stage and also has an optimum flow rate ratio.By comparing with the R13-R22 and NH 3-NH 3 cascade refrigeration cycles, the mass flow rate ratio of CO 2-NH 3 is larger than those of R13-R22 and NH 3-NH 3, the theoretical COP of CO 2-NH 3 cascade refrigeration cycle is larger than that of the R13-R22 cascade cycle and smaller than that of the NH 3-NH 3 cascade cycle. But the real COP of CO 2-NH 3 cascade cycle will be higher than those of R13-R22 and NH 3-NH 3 because the specific volume of CO 2 at low temperature does not change much and its dynamic viscosity is also small.

Theoretical Study and Performance Analysis of an Adsorption Chiller

The thermodynamic cycle for an adsorption system is presented inp-T diagram. In order to investigate the performance of the adsorption system, a lumped parameter transient model of the chiller is developed, in order to predict the behaviors of the adsorption chiller system and find the influence of working conditions on its operation. For the working process of the main components of the system, including adsorber, condenser and evaporator, the coupled unsteady equations were set up for each stage. The model was then solved using stable numerical methods from EES （equation engineering solver）, and the performance of the adsorber and condenser/evaporator of the system was analyzed. The condensation, evaporation and adsorber temperature values as well as the adsorption ratio and desorption ratio were obtained as function of operating time. Also, the coefficient of performance was analyzed in function of the heat source temperature and the cooling source temperature.

Exergetic Comparative Analysis of Ammonia and Carbon Dioxide Two-Stage Cycles for Simultaneous Cooling and Heating

The paper deals with the comparative analysis of the performance of cooling and heating systems operating with NH3 （ammonia） or CO2 （carbon dioxide）, both natural refrigerants. The study is based on the exergetic analysis that points out the location and the magnitude of a system malfunction. Both systems, with NH3 or CO2 operate in two stages. The exergetic analysis gives the direction of the structural optimization. The exergetic analysis has shown that the best structural schematic is not the same for the two agents. The exergetic analysis points out that the largest exergy destruction in the CO2 cycle is due to the throttling process and offers solutions to diminish it.