过热度对翅片管蒸发器性能影响的模拟研究

利用EVAP-COND软件对三排管翅片管蒸发器进行模拟计算。选取3种制冷剂R22、R134a和R410A,4种不同的流路布置方式,分别计算不同制冷剂出口过热度下蒸发器的总换热量,对模拟结果进行分析对比,研究出口过热度对翅片管蒸发器换热性能的影响,得出有利于指导蒸发器优化设计的结论。蒸发器出口制冷剂过热度越大,制冷量越小;设计的4种流路布置方案中第二种方案最为合理;制冷剂R410A换热性能最佳,可以替代R22。     

同时供冷供热的双级压缩制冷热泵循环性能研究

本文提出了一种双级压缩制冷热泵循环,它能够实现冷热量的同时独立调节.通过实际案例,理论分析了不同制冷剂质量流量分配率、环境温度、热水温度以及过冷与过热度工况下新循环的性能,并考察了特征温度的影响因素.     

热力条件对工质热力循环影响的分析

根据工质是否能达到环境影响小、价格合理、来源丰富、热力学性质满足制冷循环等指标。选择HFCs类制冷剂R245fa,R245ca和R236ea及R134a和碳氢类的制冷剂R600作为热泵新工质进行性能循环分析。并以热泵的制热系数COP,单位容积的制热量qv,压缩机进出口的压力比为工质循环性能评价依据进行具体的理论计算,最后整理、统计数据的计算结果,作出不同热力条件下,各种工质COP、qv压比的比较图,得出不同工质在不同热力条件下的性能特点和各自的适用范围。     

空调冷源温度与冷水机组的能效

在阐明影响冷水机组能效的基础上,利用压焓图,对制冷循环进行了热力学分析,进而以表格的形式列出了制冷剂分别为R134a和R407c,冷凝温度为40℃,蒸发温度在5℃～16℃之间变化时,制冷理论循环的单位质量制冷量、耗功量及制冷系数的变化规律.结果表明,制冷剂分别为R134a、R407c时,蒸发温度每升高1℃,制冷系数平均...     

风机变频对空气源热泵热水器系统性能影响的研究

本文建立了以制冷剂R22为工质的空气源热泵热水器性能测试系统,进行了风机变频实验,并对蒸发器建立了仿真模型。通过夏季实验和模拟分析了蒸发器传热系数与迎面风速的关系。研究结果表明:1)蒸发器出口制冷剂过热度和传热系数随着空气流速的增大而增大,直至达到某一定值后趋于稳定,说明并非风速值越大,蒸发器换热性能越好,而且较大的过热度会导致压缩机吸气温度过高,影响压缩机的使用寿命;2)不同环境温度下均存在1个最佳迎面风速使机组系统性能达到最佳,且这个最佳风速随环境温度的上升而降低。环境温度分别为20℃、25℃和30℃时,最佳迎面风速分别为6 m/s、5 m/s和4 m/s。     

环境温度对空气源热泵系统制热性能的影响研究

为了得到环境温度对以R410A(新型混合制冷剂)为制冷剂的空气源热泵系统性能的影响,使用Dymola仿真平台,搭建系统模型,同时利用文献实验数据验证系统模型的准确性,分析空气源热泵系统在不同外界工况下性能系数变化情况。通过研究得到如下结论:(1)环境温度从10℃下降到-30℃,空气源热泵系统的排气温度从86℃升高到了134℃,工质质量流量从90 g/s降低到了12 g/s,制热量从16 500 W降低到了3 300 W,制热系数从3.6下降到了1.9。(2)随环境温度的下降,压缩机吸气过热度从12 K减小到了2 K,并在0℃时产生了拐点;环境温度低于0℃时,系统能效比、制热量随过热度的减小逐渐增大,但是在过热度减小到0 K,系统能效比、制热量开始下降;环境温度高于0℃时,系统能效比、制热量随过热度的减小先逐渐增大后减小;环境温度为5℃和10℃时,过热度分别为5 K和9 K,系统的能效比、制热量最大。该研究将为寒冷地区空气源热泵系统的设计提供理论依据。     

二氧化碳制冷及其在工程机械领域的应用分析

本文介绍了二氧化碳制冷剂的基本特性及二氧化碳制冷系统工作原理,分析了二氧化碳制冷跨临界循环过程及其特点。比较分析了二氧化碳制冷剂相比其他制冷剂的优势,介绍了二氧化碳制冷系统的应用现状。对工程机械驾驶室的热环境进行分析计算,比较了二氧化碳制冷相比传统制冷方法在工程机械领域的应用优势。结果表明:在工程机械实用过程中,二氧化碳制冷系统可以有效克服传统制冷方法的短板,应用效果良好,在工程机械及其他领域应用潜力巨大。     

回热式户用冰蓄冷空调系统特性

根据户用空调系统使用时间不固定的特点,利用回热理论,研发了回热式户用冰蓄冷空调系统。分析了冰层厚度、初始蒸发温度、蓄冷管直径对蓄冷过程的影响;对研制的回热式户用冰蓄冷空调系统在蓄冷运行、制冷蓄冷同时运行模式下进行了性能测试,并与不带回热器系统进行比较。实验结果表明:使用回热器后,蓄冷运行时,吸气温度提高近25℃;蒸发温度提高近3℃;解决了吸气管外结霜、结冰问题;COP提高了3.6%。该系统的制冷蓄冷同时运行模式,解决了家用空调使用时间不固定的问题,起到了移峰填谷的作用。     

在用R12离心式冷水机组替代物的选择

根据相似原理，分析了现离心式冷水机组使用的制冷剂R11和R12的替代物物性的特殊要求，计算出各参数对出口压力的影响，得到替代物的选择原则，并筛选出两种综合性能较为优越的R12的替代物LxRl和LXR2。     

采用不同制冷剂的半封闭活塞式制冷压缩机性能比较

为了保护大气环境,适应工质替代。本文详细的阐明了不同制冷剂的性质和其理论循环的性能参数,给出了C0PELAND L型半封闭活塞式制冷压缩机的特点,对低温下COPELAND L型半封闭活塞式制冷压缩机进行了分析,将不同容量的压缩机在不同温度下使用不同制冷剂时的制冷量,输入功率,COP等性能参数做了比较,为今后压缩机与制冷剂的优化配置提供了参考依据。     

塑料换热器在溴化锂吸收式制冷机中的应用

重点分析了溴化锂吸收式制冷机存在的腐蚀性问题，提出用塑料换热器替代金属换热器的构想。以聚四氟乙烯塑料为例从塑料的分子结构特点、传热性能与成本、强度、换热器结构等方面进行了详细探讨，为进一步解决溴化锂制冷机的腐蚀问题提供参考。     

恒华国际商务中心空调设计

介绍了冰蓄冷技术在大型公共建筑中的应用,冰盘管蓄冰槽、基载主机、双工况主机、板式换热器和各种循环水泵的合理配置和控制要求及内区有余热时的空调系统设计。     

Performance analysis on a hybrid air-conditioning system of a green building

This paper presents the performance analysis on a hybrid air-conditioning system according to the hybrid building energy system of the green building demonstration project in Shanghai, in which a 150 m² solar collector is used to power two 10 kW adsorption chillers, a vapor compression heat pump is used to cool air in the evaporating end while the condensing heating at about 80 °C is fully used to regenerate a liquid desiccant dehumidification system. In the hybrid system, the sensible cooling to the air is treated mainly by solar adsorption cooling and vapor compression cooling, whereas the latent heat is treated by the liquid desiccant dehumidification system with regeneration from the condensing heat of the heat pump. The results show that the performance of this system is 44.5% higher than conventional vapor compression system at a latent load of 30% and this improving can be achieved by 73.8% at a 42% latent load. The optimal ratio of adsorption refrigerating power to total cooling load for this kind of hybrid systems is also studied in this paper.     

变频空调器制冷系统的计算模拟与实验验证

简要介绍了变频空调器制冷系统中换热器（蒸发器和冷凝器）、毛细管、压缩机、连接管道和储液器等设备的数学模型的建立和耦合求解。根据毛细管节流并带有低压储液器的制冷系统的特点,提出了了制冷剂充灌量和储液器出口过热度相结合,作为系统模拟计算的最终封闭条件。通过对变频空调器不同频率和不同充灌量下的实验研究,验证了所建模型的正确性。     

Research on the control laws of the electronic expansion valve for an air source heat pump water heater

Compared to the conventional air conditioner, the air source heat pump water heater (ASHPWH) possesses wider operating ranges and more dramatic changes in working conditions. Conversely, traditional throttle devices, such as the thermostatic expansion valve (TEV) and capillary tube, are restricted by narrow regulating ranges in refrigerant mass flow rate and lagging response to the superheat. This article incorporates a novel dual-fuzzy-controller to regulate the electronic expansion valve (EEV) specialized for the ASHPWH system. The study analyzes the effects of the EEV initial opening and the target superheat on the performance of the ASHPWH. Moreover, this research proposes a fuzzy control method of selecting the initial opening and the target superheat on the basis of the ambient temperature and water temperature, and employs superheat error (e) and the derivation of superheat error (ec) as the input variables of the fuzzy controller B to regulate the opening of the EEV during steady running process. To improve self-adaptability of the fuzzy controller, a rule modifier and a gain scheduler are introduced. In order to quantitatively reflect the difference in the performance between the TEV-controlled system and EEV-controlled one, experimental comparison between the EEV and the TEV is presented. Results demonstrate that both the stability and efficiency of the ASHPWH can be improved significantly by the EEV.     

The application of heat pipe heat exchangers to improve the air quality and reduce the energy consumption of the air conditioning system in a hospital ward—A full year model simulation

Research was conducted to study the effect of heat pipe heat exchangers on the existing air conditioning system of a hospital ward located in Malaysia, a tropical region. The present research employs the transient system simulation software (TRNSYS) to study the hour-by-hour performance of the system in terms of supply duct air and indoor air conditions in the ward space. Fieldwork study showed that the existing air conditioning system operating in the Orthopaedic Ward, University of Malaya, Malaysia is not capable of providing the desired supply duct air and indoor air to the space. Therefore, the possibility of improving the air conditioning system by adding heat pipe heat exchangers was investigated. The impact on energy consumption, power savings, supply duct air and indoor air with heat pipe heat exchangers incorporated in the air conditioning system were simulated and the results were compared with the existing system.Based on the present research, the system with the added eight-row heat pipe heat exchangers is recommended to provide convenient and healthy air into the ward space according to the ASHRAE recommendations. Moreover, it was found that by applying the new design, a considerable amount of energy and power could be saved.     

地源热泵桩基与钻孔埋管换热器换热性能比较

相对于钻孔埋管换热器,桩基埋管换热器在换热性能和经济性方面均具有较大优势,目前越来越广泛的应用于地源热泵工程中。围绕钻孔与桩基埋管换热器的结构特点和换热机理进行对比分析,针对南京某项目桩基埋管换热器开展了换热性能实测及数值模拟分析,并采用数值模拟手段对比分析了钻孔与桩基埋管换热器的换热性能差异。研究结果进一步证明了桩基埋管换热器具有良好的换热性能。提出的传热性能数值模拟方法可较准确地计算出桩基和钻孔埋管换热器的传热效率。     

Selective permeation of moisture and VOCs through polymer membranes used in total heat exchangers for indoor air ventilation

Fresh air ventilation is central to indoor environmental control. Total heat exchangers can be key equipment for energy conservation in ventilation. Membranes have been used for total heat exchangers for more than a decade. Much effort has been spent to achieve water vapor permeability of various membranes; however, relatively little attention has been paid to the selectivity of moisture compared with volatile organic compounds (VOCs) through such membranes. In this investigation, the most commonly used membranes, both hydrophilic and hydrophobic ones, are tested for their permeability for moisture and five VOCs (acetic acid, formaldehyde, acetaldehyde, toluene, and ethane). The selectivity of moisture vs. VOCs in these membranes is then evaluated. With a solution-diffusion model, the solubility and diffusivity of moisture and VOCs in these membranes are calculated. The resulting data could provide some reference for future material selection. PRACTICAL IMPLICATIONS: Total heat exchangers are important equipment for fresh air ventilation with energy conservation. However, their implications for indoor air quality in terms of volatile organic compound permeation have not been known. The data in this article help us to clarify the impacts on indoor VOC levels of membrane-based heat exchangers. Guidelines for material selection can be obtained for future use total heat exchangers for building ventilation.     

地源热泵夏季性能测试及传热模型

对50m深埋地下换热器地源热泵系统夏季间歇运行时的制冷性能进行了测试，分析了系统运行对地温的影响，提出采用混合系统来解决重庆地区冬夏季土壤中吸热、放热不平衡的问题，引入圆柱源理论建立了垂直U型管传热模型，模拟结果与实验结果吻合较好。