一个可利用低品位热能的双级除湿冷却式空调系统

本文建立了一个可利用低品位热能的双级除湿冷却式空调系统及其数学模型,并用该模型模拟香港一办公楼作为新风系统的除湿冷却式空调系统。计算机模拟结果显示：双级系统所需的再生温度仅为５９．０℃,较单级系统低２４．２℃,这使得低品位热能的利用成为可能;双级除湿冷却式空调系统可提供湿度足够低的送风,以承担全部湿负荷,故该系统可以很好地与冷幅射天花板系统配合使用,从而实现显热与潜热的分别处理,提高温湿度的控制精度;而且由于机械制冷仅仅被用于消除显热,所以可以提高制冷系统的蒸发温度从而提高制冷系统的性能系数。     

电动汽车引射空调系统性能实验研究

本文提出一种电动汽车引射空调系统,该系统将车内蒸发器设计成前后排分离形式,并在其间加入引射器,以提高压缩机吸气压力,形成梯级蒸发,从而优化系统性能.实验研究了在不同蒸发温度、冷凝温度工况下电动汽车引射空调系统的性能,并与传统空调系统进行了对比.实验结果表明:在不同制冷工况下,电动汽车引射空调系统性能始终优于传统空调系统...     

热回收效率对排风热回收式热泵性能的影响研究

排风热回收式热泵因具有结构紧凑,节能环保等优点,在北欧等国家得到一定的推广。排风热回收式热泵主要分为单级和双级热回收式热泵,而热回收装置作为双级热回收式热泵的重要部件,其热回收效率会影响到整个热泵系统的性能。通过TRNSYS对双级热回收式热泵在重庆冬季的运行情况进行了模拟,并与常规空气源热泵和单级热回收式热泵进行了对比。结果表明,双级热回收式热泵机组的性能系数随着热回收的效率升高而降低,且介于单级热回收式热泵和常规空气源热泵的性能系数之间,而双级热回收式热泵系统的性能系数则随热回收的效率升高而升高,在热回收效率为0.6的情况下,系统的性能系数为5.262,相较单级热回收式热泵和常规空气源热泵的性能系数,能效分别提升了31.29%和83.22%。     

空调系统动态运行能效的探讨

根据空调系统运行的动态特点,分析了空调系统全年和典型日的变化;通过对空调系统主要组成部分的性能研究,为系统动态性能的研究奠定了基础,提出了空调系统动态运行能效的概念,它是指空调系统在运行工况下的综合能效,而不是设计条件下的能效,也不是系统某个组成部分的能效;针对空调系统部分负荷下的运行,综述了国内外在窄调系统动态性能以及节能运行调控策略方面的研究.     

广州市某大型商场空调系统运行性能分析

对广州市某大型综合性商场空调运行性能进行了调查,全面分析了空调机组的运行工况,得出空调系统的负荷变化规律、能耗现状.结合分析结果,提出该商场空调存在的问题,并探讨了空调系统节能技术措施.     

双级压缩空气循环制冷系统的特性与优化研究

空气循环制冷由于其性能低下,影响了其在普通空调中的应用,如何提高空气循环制冷系统的性能一直是研究的焦点。本文主要针对双级压缩空气循环制冷系统的特性与优化进行了研究,分析了系统的流程,建立了热力学模型;结果表明:转动部件的等熵效率及换热器效率对循环特性有显著影响,实际循环中存在一最优膨胀比,其位置受转动部件等熵效率及换热器效率影响,附加回热器可以提高循环的性能,同时降低了最优压比。     

金属氢化物热泵空调研究进展

叙述了节能环保新技术--金属氢化物热泵空调装置的原理、性能特点和国内外研究发展状况.介绍了美、日、欧等数套金属氢化物热泵空调的研制情况.综述了提高储氢合金材料性能和强化金属氢化物热泵空调系统传热能力的技术措施.最后,评述了金属氢化物空调热泵系统的组织情况及其运行的数值模拟研究.     

一种中频双级电子式电流互感器误差特性的研究

研究了一种基于低功率铁心线圈的中频双级电子式电流互感器.通过对中频双级电子式电流互感器等效电路的分析,得到了电流误差和相位误差的表达式.为验证双级电子式电流互感器的中频传感性能,构建了基于差值法的中频双级电子式电流互感器校验系统,该系统采用32位DSP浮点芯片TMS320F28335进行数据采集控制和运算处理.实验结果表明,该双级电子式电流互感器在50～1 000Hz频率范围内的误差准确度可达0.05级.     

小型蓄冷空调系统动态性能研究

阐述小型空调系统的工作原理和循环特性,分析了该蓄冷空调系统在不同工况下的性能,讨论了不同工况下的过冷度对该系统性能的影响.     

低温实验冷库系统优化切换的实验研究

在提倡节能节材的今天，冷库用制冷系统的经济性显得至关重要。对于获取低温的两种手段—双级压缩循环和复叠循环来说，它们分别在不同的温区具有经济性优势。针对一座具有双级压缩循环和复叠循环组合系统的--60℃低温实验冷库，简要介绍了其系统组成，从能量平衡的角度引入了系统运行的经济指标；通过实验分别得出了双级压缩系统和复叠系统的性能数据；运用Microsot Excel办公软件分析实验数据，找出了两套系统经济指标随冷库内温度变化的曲线；分析了经济性能随冷库内温度及环境温度变化的特点，进一步找出了从双级压缩系统向复叠系统切换的最佳温度区域。     

除湿溶液蒸汽压的研究

除湿溶液表面蒸汽压的大小直接影响液体除湿空调系统的性能,在常用的除湿剂中由于氯化钙的价格低廉,是一种比较经济的除湿剂,但它的缺点是蒸气压比较高,除湿效果不稳定,而氯化锂的价格高,水蒸气压较低且稳定,是一种性能非常优良的除湿剂.为了提高除湿溶液的除湿性能和降低其价格,可以把两种除湿剂按不同的比例进行混合,就可以得到性价比比较好的除湿溶液.文中应用经典热力学理论研究了常用除湿溶液表面蒸汽压的形成机理.对氯化钙、氯化锂及其混合溶液表面蒸汽压进行了计算,计算结果和实验结果非常接近,认为该方法可以用来较准确的估算各类除湿溶液的蒸汽压,为液体除湿空调系统中除湿剂的选择提供理论依据.     

Evaluation of heat and mass transfer coefficients in a gauze-type structured packing air dehumidifier operating with liquid desiccant

In this paper, high performance packing, namely, structured packing that has good heat and mass transfer characteristics, is proposed for dehumidification of air using liquid desiccants and for regeneration of liquid desiccants. In order to design a structured packing tower for liquid desiccant — air contacting operations, heat and mass transfer coefficients for each phase are required. This paper is concerned with the interface transfer of heat and mass when air is brought into contact with the liquid desiccant solution. A theoretical study of evaluating heat and mass coefficients in an air-desiccant contact system employing three liquid desiccants, namely calcium chloride, lithium chloride, and a mixture of 50% calcium chloride and 50% lithium chloride (called cost effective liquid desiccant, CELD) is investigated. Moreover, air phase transfer coefficients are correlated with flow rates of air and liquid and the temperature of air, whereas liquid phase coefficients are correlated with rates of air and liquid flow, and the temperature and concentration of the liquid. The findings for the three liquid desiccants are compared and discussed.     

制冷系统中干燥剂的制备研究进展

氟利昂与制冷机油（或溶剂油）一起组成的制冷介质中,常常含有空气、水分、酸份等微量杂质。微量杂质的存在常常导致制冷系统无法正常进行。为此,制冷系统一般采用硅胶、活性氧化铝、分子筛、活性炭等干燥剂来净化回路中的水分、酸份等污染物。随着氟利昂制冷剂的不断更新,对相应的干燥剂的性能也提出更高的要求。通过详细介绍制冷系统中氟利昂干燥剂的不同制备方法并比较它们的优缺点,提出干燥剂的研究开发主要应从两个方向努力：一是提高产品的性能,尤其是相容性和吸水能力;另一方面是简化工艺,降低成本。分子筛具有均一孔径、高比表面积以及选择性吸附等性能,是氟利昂制冷剂最理想的干燥剂材料。加强对分子筛的改性和成型工艺研究,是逐步解决氟利昂制冷介质干燥的主要途径。     

复叠式与二级压缩式热泵冷冻干燥系统循环特性比较

为了降低干燥过程的能耗,提高冷冻干燥过程的经济性,故以R600a/R290和R90为工质,分别构建了复叠式循环和二级压缩式循环的热泵冷冻干燥系统.对2种热泵干燥系统的构建方法和循环性能进行了分析和计算,并讨论了中间温度、加热温度和冷阱温度变化对系统循环特性的影响.计算结果表明,复叠式热泵循环和二级压缩式热泵循环均可用于冷冻干燥系统;在常规的冷冻干燥条件下,系统中采用复叠式热泵循环较适宜.     

Thermodynamic analysis of single-stage and single-effect two-stage adsorption cooling cycles using indigenous coconut shell based activated carbon-CO2 pair

The CO₂ adsorption pressure concentration isotherms of indigenous coconut shell based activated carbon are measured using Sievert's type experimental setup. The thermodynamic properties viz. isosteric heat of adsorption at surface loading, Gibbs free energy, entropy and specific heat capacity are estimated using measured adsorption isotherms data. These measured adsorption isotherms data and thermodynamic properties are used for the thermodynamic analysis of single-stage and single-effect two-stage adsorption cooling system. The performance of the adsorption cooling cycle in terms of the maximum theoretical specific cooling effect and coefficient of performance at different driving heat source temperatures (80 °C for single-stage and 65 °C for single-effect two-stage) and evaporator temperatures (0, 5, 10 and 15 °C) is estimated. The maximum values of specific cooling effect and coefficient of performance are obtained as 9.26 kJ kg⁻¹ and 0.06 for single-stage and 8.85 kJ kg⁻¹ and 0.04 for single-effect two-stage cooling system respectively.     

Second-law-based thermodynamic analysis of two-stage and mechanical-subcooling refrigeration cycles

Thermodynamic analysis of HFC-134a vapor-compression refrigeration cycles is investigated by both the first and second laws of thermodynamics. Second-law analysis is carried out for both two-stage and mechanical-subcooling refrigeration cycles. The analysis is performed on each of the system components to determine their individual contribution to the overall system irreversible losses. It is found that most of the losses are due to a low compressor efficiency. Irreversibilities of expansion valves and condenser are also significant. In addition, it is shown that the optimum inter-stage pressure for two-stage and mechanical-subcooling refrigeration systems is very close to the saturation pressure corresponding to the arithmetic mean of the refrigerant condensation and evaporation temperatures. These results are compared with the existing practice in the industry. Furthermore, theoretical results of a two-stage refrigeration system performance are also compared with experimental values for a CFC-22 system.     

Performance improvement of a transcritical CO2 refrigeration cycle using two-stage thermoelectric modules in sub-cooler and gas cooler

A novel integration of a trans-critical CO₂ refrigeration cycle with thermoelectric modules in the gas cooler and sub-cooler is presented, wherein a two-stage thermoelectric generator (TEG) produces power from the waste heat of gas cooler, which is a considerable amount of required power in two-stage thermoelectric cooler (TEC) to sub-cool the refrigerant before expansion device. Mathematical simulation of TEG and TEC as well as energy and exergy based thermodynamic analysis of the proposed system is performed, and the effects of some important parameters on the system performance are investigated. A comparison is carried out between the proposed system and the simple CO₂ refrigeration cycle, indicating that the proposed configuration improves the coefficient of performance (COP) about 19%. Also, it is observed that the TEC and TEG have better performance in a two-stage configuration. The parametric study reveals that the new configuration decreases the cycle operation pressure at maximum COP and exergetic efficiency.     

An Effective Desiccant System to Regulate the Humidity Inside the Chambers of the Solid Dosage Forms

The most common way to protect moisture-sensitive pharmaceutical powders is to utilize protective packaging. However, the most convenient package materials are all permeable to water molecules to some extent and limited protection is normally achieved with this arrangement even though desiccants are employed. In the present study we introduce a novel system that can regulate the internal humidity of the containers used with solid dosage forms for a desired time at a requested level. Instead of the widely used solid adsorbents the system utilizes saturated salt solutions loaded in desiccant bags made of various polymer materials with appropriate permeation properties. By utilizing salt solutions the size of the desiccant bag can be further reduced. A wide variety of commonly used powder chambers and desiccant bags are tested, proving the effectiveness of the introduced system.     

An effective desiccant system to regulate the humidity inside the chambers of the solid dosage forms

The most common way to protect moisture-sensitive pharmaceutical powders is to utilize protective packaging. However, the most convenient package materials are all permeable to water molecules to some extent and limited protection is normally achieved with this arrangement even though desiccants are employed. In the present study we introduce a novel system that can regulate the internal humidity of the containers used with solid dosage forms for a desired time at a requested level. Instead of the widely used solid adsorbents the system utilizes saturated salt solutions loaded in desiccant bags made of various polymer materials with appropriate permeation properties. By utilizing salt solutions the size of the desiccant bag can be further reduced. A wide variety of commonly used powder chambers and desiccant bags are tested, proving the effectiveness of the introduced system.     

内燃动车动力总成隔振性能分析

大功率柴油机产生的宽频带振动,双层隔振系统具有良好的高频隔振能力,已在船舶等领域得到了应用。但在中、高速柴油机的内燃机车等领域,国内对于双层隔振系统的应用研究很少。结合国内首次研制的某型内燃动车动力总成系统,对双层隔振系统的隔振性能进行了仿真和实验研究。首先采用理论计算和实验识别结合的方法确定了作用在柴油发电机组上的激振力（矩）特性;然后建立了双层隔振系统多体动力学模型,通过仿真计算,求得了理论力传递率;最后进行了双层隔振系统力传递率测试,获得了双层隔振系统实际力传递率,其力传递率明显低于单层隔振系统。对于双层隔振系统设计和工程应用有一定的参考。