制冷系统中蒸发式冷凝器性能的影响因素分析

本文基于蒸发式冷凝器传热传质的特点，分析了影响制冷系统中的蒸发式冷凝器性能的几个重要因素，介绍了蒸发式冷凝器研究和发展的有关趋势。     

蒸发式冷凝器热质传递模型的建立与分析

本文根据热力学和传热学理论,考虑因水蒸发或凝结而引起的喷淋水量和空气含湿量沿蒸发式冷凝器高度的变化,建立蒸发式冷凝器的热质传递数学模型,并对模型进行了合理简化,推导出描述这一热质传递过程常微分方程组的分析解。所得分析解给出了蒸发式冷凝器高度上空气含湿量、比焓、温度和水温等各参数的分布情况,并讨论了空气质量流量、喷淋水量等参数对蒸发式冷凝器换热性能的影响。蒸发式冷凝器数学模型的解析解可用于蒸发式冷凝器传热传质性能的理论分析及设计校核计算,具有较高的理论及应用价值。     

水平管蒸发式冷凝器性能研究

详细介绍了实验流程及测试方法和数据处理.高湿环境条件下的实验数据显示:相同湿球温度下,较干燥的空气可以获得较高的系统能效比,冷凝器排热效率的变化则不明显;相同干球温度、风量和淋水量时,湿球温度升高,冷凝器的排热能力显著降低,排热效率则略有增加.对于特定的蒸发式冷凝器,存在最佳的迎面风速和喷淋水密度.根据实验结果拟合得到了换热管外水膜一空气间的传热系数关系式.通过分析得出了不同排热量下冷凝器蒸气段、冷凝段和过冷段排热量比例和换热面积分配.     

蒸发式冷凝器应用于房间空调器的试验研究

试验研究表明，采用蒸发式冷凝器可使空调器的能效比提高５０％－７０％。为了工程设计的实用目的，根据试验结果回归得出了α，Ｊ，Δｐ等关系式。。     

蒸发式冷凝器的应用与研究

分析了蒸发式冷凝器的应用及研究现状,介绍了国内三种主要蒸发式冷凝器的特点,总结了蒸发式冷凝器使用中存在的问题并提出了解决方法,展望了蒸发式冷凝器的发展方向和应用前景。     

制冷系统中蒸发式冷凝器性能的影响因素分析

本文基于蒸发式冷凝器传热传质的特点,分析了影响制冷系统中的蒸发式冷凝器性能的几个重要因素,介绍了蒸发式冷凝器研究和发展的有关趋势。     

污垢对蒸发式冷凝器性能的影响

污垢是影响蒸发式冷凝器效率的主要因素之一。本文根据文献中污垢特性模型,利用实验数据,分析污垢层厚度对排热量的影响,通过计算可知:污垢导致设备排热量降低最大可达75%;同时分析在污垢条件下,湿球温度对换热性能增长的影响程度,研究结果表明:湿球温度降低引起的换热效率增长趋势,在垢层厚度增加的情况下减缓较快。     

蒸发式冷凝器压缩机能耗及换热性能实验研究

为进一步研究压缩机能耗及蒸发式冷凝器换热性能,本文采用对比实验的方法,研究了冷凝器进风温度,进风湿度以及喷淋水量等因素对空冷与蒸发式冷凝器的压缩机能耗及换热性能的影响。通过研究表明,冷凝器进风空气湿度对压缩机耗功量的影响较小,而压缩机耗功量随进风温度的增加而增加,随喷淋水量增加呈先减小后增加的趋势,喷淋水量在不同的进风温度工况下存在最佳值,蒸发式冷凝器管外复合换热系数随进风温度的增加而递减,随喷淋水量增加而增大。     

蒸发式冷凝器在人防工程中的应用

本文简单地介绍了冷却塔和蒸发式冷凝器在工程应用中的优缺点,一般情况都将这两种冷却设备放在地面通风良好的环境中。银川市南门广场人防地下商场,地面为12,000平方米的市民休闲绿地广场,南于冷却塔的噪声、飘水,因此在广场上不宜设置冷却塔。本工程空调冷却水的冷却采用蒸发式冷凝器,并且将蒸发式冷凝器从地上移置到地下室的机房内,与热泵机组配套使用,夏天作为冷凝器,冬天作为蒸发器在本工程中创造了比较满意的空调效果。但是使用蒸发式冷凝器的初投资比冷却塔高出5、6倍,而且所需冷却风量较大,因此设计时应做充分的综合比较。     

蒸发式冷凝空调系统运行中能效的实验研究

将蒸发式冷凝器应用于建筑制冷空调系统作为新型的冷却散热设备,建立实验平台对运行参数进行优化和对系统能效进行实验研究。实验结果表明:该系统最佳的运行参数组合是风速3.1m·s-1和水喷淋密度0.052kg·m-1·s-1;随着负荷率的逐渐降低,冷凝温度在38.9～34.9℃之间,制冷机COP在5.02～2.54之间,冷凝侧EER在4.48～2.23之间。蒸发式冷凝空调系统运行稳定、高效节能,适用于建筑制冷空调。     

TRNSYS simulation for solar-assisted liquid desiccant evaporative cooling

ABSTRACT

Recently, desiccant cooling systems are well thought of as a competent method for controlling the water content in the air. A solar flat-plate collector has been used as it decreases the dependency on non-renewable resources. Solar-aided liquid desiccant systems have been used to reduce the dependency of air-conditioning systems on non-renewable sources of energy. Manipal’s humid and searing climate provides certain benefits in setting up such a system. The suggested system has reliability and equipment life and also takes complete advantage of the available solar energy for the renewal of the liquid desiccant. TRNSYS simulation is used to predict the efficiency and feasibility of the system. The temperature and energy-load variations were successfully obtained. An effective simulation was developed whereby the solar air conditioning of a room was indicated.     

溶液除湿过程热质交换规律分析

除湿器和再生器是溶液除湿系统的重要传热传质部件。建立了一个测试叉流除湿、再生模块性能的实验台,以溴化锂溶液为除湿剂,用除湿量、除湿效率和体积传质系数描述除湿效果,实验测试了溶液和被处理空气的进口参数对除湿器性能的影响。由实验数据得到的准则关联式,可供叉流除湿器设计参考使用。     

采用吸湿剂处理湿空气的流程优化分析

分析了吸湿剂与空气直接接触的热湿传递过程,得到了溶液与空气热湿传递过程中传热、传湿阻力表达式,比较了溶液-空气不同进口状态的传热、传湿不匹配系数.在溶液进口状态等浓度线上进行的热湿传递过程传热、传湿不匹配系数最小,而等焓线上发生的过程的传热、传湿不匹配系数较大.在构建溶液与空气的热湿处理流程中,应尽可能使除湿与再生过程贴近溶液等浓度线进行.固体吸湿剂与溶液之间的性质差异使得固体吸湿剂与空气间的热湿传递过程一般沿着等焓线发生.     

溶液-湿空气热质交换过程的匹配研究

吸湿性溶液与空气的热质交换过程既有热量的交换又有质量的交换,提高该过程的可逆程度是提高溶液除湿空调系统性能的重要手段。在对溶液的性质进行合理简化的基础上,分析了溶液与空气的热质交换过程的流量比和过程需要吸收或释放的热量,得到在不同工况下,可逆过程所要求的流量比和应该补充或带走的热量。认为这一结论有助于溶液除湿空调流程的设计和相关参数的选取。     

利用盐溶液制备冷水的冷水机组

在间接蒸发冷却装置的基础上，设计了利用盐溶液制备冷水的冷水机组，使得间接蒸发冷却技术能够应用于非干燥地区，并运用了热回收技术达到节能目的。通过对不同室外工况下冷水机组性能的模拟，发现COP对室外空气含湿量最敏感。最后模拟分析了在北京地区使用时此冷水机组的整体性能。     

Application of desiccant systems for improving the performance of an evaporative cooling-assisted 100% outdoor air system in hot and humid climates

The purpose of this study was to enhance the energy-saving potential of an indirect and direct evaporative cooling-assisted 100% outdoor air system (IDECOAS) by integrating it with either a solid or liquid desiccant system. The desiccant system can be installed either at the scavenger air side of the indirect evaporative cooler (IEC) to enhance its effectiveness or at the primary air side of the IEC to reduce the latent load of outdoor air. The operating energy consumption affected by the location and type of the desiccant unit integrated with IDECOAS was simulated under three different hot and humid climates using TRNSYS 17 integrated with commercial equation solver programme. And then, the most energy-conservative configuration was selected for each climate zone as the proposed system. The simulation results showed that configurations with the desiccant dehumidification unit located upstream of the IDECOAS consume 76–85% less cooling coil energy than those with the desiccant unit located downstream of the IDECOAS. It was also found that the liquid desiccant system saves 21–50% more primary energy than the solid one, when it is integrated with IDECOAS.     

溶液除湿空调系统蓄能性能分析

介绍了溶液除湿蒸发冷却空调系统的蓄能原理,分析了蓄能密度的影响因素。与冰蓄冷、水蓄冷和气体水合物蓄冷等常规蓄冷方式的比较结果表明,溶液除湿空调系统在蓄能方面有明显的优势,其蓄能密度远大于常规蓄冷方式。该系统可以利用太阳能作为再生能源,白天蓄存浓溶液用于夜间制冷,节能效果显著。     

空调用蒸发式冷凝器能耗实验研究

当室外气温较高时,风冷热泵系统冷凝器存在换热效果下降的问题,而蒸发式冷凝器可以改善此问题,蒸发式冷凝器因此逐步得到广泛重视。为研究采用蒸发式冷凝器制冷系统的能耗情况,通过正交实验的方法,对比研究了蒸发式冷凝器与风冷式冷凝器在相同工况下压缩机能耗情况,并对影响其性能的因素进行了分析。研究表明,各因素对压缩机耗功量的影响能力依次为:冷凝器进口空气温度、速度及冷凝器喷水量。压缩机耗功量随进口空气温度的升高、进风空气速度降低而增大,随喷水量增加存在先减小后保持不变的现象。     

Feasibility and performance analysis of a desiccant solution regenerator using hot air

This paper investigated a desiccant solution regenerator using hot air to concentrate diluted desiccant solution, aiming to utilize the waste heat of hot air, such as the hot air from the condensers of vapor compression refrigeration systems. To verify the feasibility of the utilization of the hot air for the desiccant solution regeneration and disclose the performance of such kind of regenerators, performance analysis was conducted numerically by a validated mathematical model and parametric distribution of the air in a typical case was explored. The results showed that it was possible to use hot air for the desiccant solution regeneration when the requirement of the lowest inlet solution temperature was met and a typical case showed that the suggested hot air temperature was around 65 °C. Effects of main operation parameters on the regeneration thermal efficiency and regeneration rate were discussed and the result showed the regeneration thermal efficiency could achieve the maximum (η_{reg, max}) when the R was around 8 and lower flow rate of the desiccant could achieve higher η_{reg, max}. In addition, effects of dimensions of the regenerator on the regeneration performance were disclosed and some suggestions of design of the regenerators were introduced based on the study.     

Similarity of coupled heat and mass transfer between air–water and air–liquid desiccant direct-contact systems

Packed-bed heat and mass transfer devices are widely used in air-conditioning systems, such as cooling tower, evaporative cooler of air–water direct-contact devices, dehumidifier and regenerator of air–liquid desiccant direct-contact devices. Similarities of heat and mass transfer characteristics between air–water and air–liquid desiccant devices are considered and investigated in this paper. Same reachable handling region of outlet air can be obtained for both air–water and air–liquid desiccant devices, which is among three boundary lines, isenthalpic line of inlet air, iso-relative humidity line of inlet fluid (water or desiccant), and the connecting line of inlet statuses of air and fluid. Inlet conditions of air and fluid affect heat and mass transfer characteristics to some extent, so that a zonal method is proposed only according to the relative statuses of inlet air to inlet fluid. Four zones, dehumidification zones A, D and regeneration zones B, C, are divided for air-desiccant direct-contact devices. The first three zones A, B and C are divided for air–water direct-contact devices, with the same zonal properties as those of air-desiccant devices. In order to obtain better humidification performance, fluid should be heated (in zone C) rather than air (in zone B). And fluid should be cooled (in zone A) rather than air (in zone D) to obtain better dehumidification performance. Counter-flow pattern should be applied for best mass transfer performance in the same conditions within the recommended zone A or C, while parallel-flow pattern is the best in zone B or D.