喷水室内热湿交换数值模拟研究

介绍了喷水室这种利用水与空气直接接触来达到调节空气温度、湿度的方式,并在其他学者研究的基础上,主要利用数值模拟的方法分析各个因素对喷水室内热湿交换过程的影响.认为提高断面空气流速,可以提高喷水室的热湿交换效率;加大空气与水的初始温差,有利于喷水室的热湿交换;喷水方向和排间距对喷水室的热湿交换也有较大的影响.     

直接接触式恒湿设备中热湿交换水箱的结构优化分析

直接接触式恒湿设备对环境湿度的调控效果受到其热湿交换水箱中空气与水热湿交换效率的制约,为提高空气与水的热湿交换效率,在深入分析传热传质机理的基础上,利用CFD软件建立了三维热湿交换水箱的数学模型,对3种不同结构水箱内的空气处理过程进行了模拟分析。结果表明,较大的空气流速可以获得较高的传热传质速率;水箱中增加导流板能提高空气与水的湿交换速率;"上送上回"式水箱中传质速率受液位高度变化的影响最小,且始终能保持最好的湿交换效果。     

国内喷水室的研究现状

与表面式空气处理设备不同,喷水室是空气与水直接接触的空气热湿处理设备。根据喷水温度不同,喷水室可实现多种空气热湿处理过程,同时,还具有一定对空气的净化除尘功效。本文介绍了喷水室的分类,并从其原理出发总结了国内有关喷水室的热湿交换性能、喷嘴和净化除尘3个方面的研究进展,分析了喷水室研究的发展趋势。     

喷水室热工计算的一种方法

本文分析了喷水室内水和空气之间的热质交换过程,推导出通用有效热交换效率E和传热效率X的理论计算公式,并建立了这两种效率之间的关系式,在此基础上提出了可用于喷水室热工计算的一种计算方法,该法可以在不涉及任何实验结果的条件下求解喷水室各类热工计算,计算结果与实验结果以及国内外现行的其他计算方法的计算结果基本一致。     

地下水电站通风道气流参数计算模型研究

针对目前水电站地下风道气流参数计算模型的不足,提出准三维计算模型,可对空气与风道的热湿交换进行准确的计算。通过分析地下水电站通风道气流与岩体热湿传递的物理模型和基本特征,提出计算思想并建立相应的数学模型,可对空气与风道的传热及结露同时求解,编制模型求解的计算机程序,将风道沿长度方向分为多个单元进行逐次求解,最后将实测数据与程序计算数据进行对比,结果表明,实测与计算的温度波幅衰减幅度相近,绝大部分时间内,两种结果差值低于1℃。     

降膜蒸发冷凝器建模及仿真

为详细分析降膜蒸发冷凝器传热传质规律,本文将冷凝器等效为所有单管组成的网络,每根单管离散为多个微元,建立了带增膜板的蒸发冷凝器稳态传热传质微元数学模型,并引入了一个新的无量纲准则数Xr,以反映水膜厚度对空气和水膜间传热传质的影响。通过VS 2010软件编程,采用双点弦截法迭代计算,模拟并分析了顺排和叉排结构管束的蒸发冷凝器管外水膜温度、空气温度、空气湿度和管内热流体温度的变化规律。仿真软件能反映并能预测多种结构降膜蒸发冷凝器的性能,为冷凝器的优化提供仿真依据。     

植被高度对建筑微环境影响的数值模拟

植物通过蒸腾作用,与周围大气不断进行着热湿交换,从而调节大气的温、湿度分布。植被对太阳辐射的反射和遮挡作用,使得调节作用提升到叶面高度附近。植被的高度、覆盖率、覆盖面积都会对空气的温、湿度分布产生不同的影响。利用流体力学计算软件,提出了把建筑室内外热环境耦合,将植被区域视为多孔介质的方法,初步分析了不同高度植被对建筑微环境的空气温度及热量交换的影响规律,旨在探究各种植被条件对建筑微环境的影响。     

计算表面式空气冷却器的简便方法

本文从表明热湿交换相似关系的Lewis比例出发,经过较严格的数学推导,得出了利用干工况传热效率计算表面式空气冷却器(简称表冷器)湿工况传热的简便方法——焓值效率法和湿球温度效率法。用这个方法,函数关系清晰明了,可不用试算而简便地直接算出结果,而且便于制成计算图表,使各类计算更加方便直观;同时,经过与实测结果的比较表明,计算精度也令人满意。     

单层工厂周围不同下垫面对空气温度的影响研究

植物通过蒸腾作用,与周围大气不断进行着热湿交换,从而调节大气的温、湿度分布。植被对太阳辐射的反射和遮挡作用,使得调节作用提升到叶面高度附近。植被的高度、覆盖率、覆盖面积都会对空气的温、湿度分布产生不同的影响。利用流体力学计算软件CFD,提出了把建筑室内外热环境耦合的方法,初步分析了不同下垫面对空气温度的影响规律,旨在探究各种下垫面条件对建筑微环境的影响。     

热湿地区办公建筑空调冷冻水变温调节分析

依据BIN能耗分析负荷计算方法,以广州为例,分析了热湿地区办公类建筑在不同室外气象参数下的负荷特点,并研究了在风机盘管加新风系统中冷冻水温度变化对末端空气处理设备全热、显热、潜热以及热湿比的影响,通过计算实例,给出了热湿地区办公类建筑分阶段变水温运行方案。     

板式蒸发式冷凝器传热传质的数值模拟

根据能量守恒和质量守恒定律,对板式蒸发式冷凝器中制冷剂、冷却水与空气之间的传热传质过程,建立了热质交换过程的二维数学模型,由此分析板式蒸发式冷凝器中冷却水温度、空气温度和空气含湿量等参数的分布规律,以及空气流速、干湿球温度、冷却水喷淋密度和冷凝温度对板式蒸发式冷凝器热流密度的影响,并将模拟结果通过实验进行了验证,两者之间的误差在10%以内。研究表明:板式蒸发式冷凝器的热流密度随进口空气流速的增加而增大,随湿球温度的升高而减小,几乎不受进口空气干球温度的影响;热流密度随着冷却水喷淋密度的增加逐渐增大,但增大至一定量后不再对热流密度有明显影响;冷凝温度越高,其热流密度越大。上述结论对板式蒸发式冷凝器的优化设计具有指导意义。     

Thermal calculation of the ejection cooling tower and method of improving its efficiency

A mathematical model for thermal calculation of the ejection cooling tower has been proposed. New data on the effect of the air flow rate, meteorological conditions, heat load, and water pressure in the water distribution system of the cooling tower on the spray characteristics and water cooling have been obtained. A novel method of improving the efficiency of the ejection cooling tower has been developed.     

空调器送风参数对房间速度场和温度影响的计算模拟和试验研究

本文对天花板嵌入式空调器工作的房间,建立了空气流动的三维紊流数学模型,对不同送风参数下的流场和温度场做了计算.并对计算结果进行分析,总结出送风参数对空调房间的气流流动与温度分布的影响规律.又搭建试验台,对不同送风参数下空调房间的温度场和速度场进行试验研究.用小尺度实体模型试验的方法,首次把PIV新技术运用到空调房间流场的测量上.测试结果与计算结果吻合较好,验证了建立的数字模型的正确性,也验证了PIV技术可以运用到大空间的流场测量上.最后利用气流理论对嵌入式空调器不同送风参数下的房间温度场和流场进行了评价.     

Mathematical Modeling of Evaporative Cooling of Water in a Mechanical-Draft Tower

A mathematical model of the operation of a mechanical-draft tower is proposed. The model represents a boundary-value problem for five differential equations and for the first time takes into account the following parameters: temperature of inflowing water, its discharge, mean radius of water droplets, mean air velocity inside the water-cooling tower, rate of fall of a droplet, height from which droplets fall, and meteorological conditions, including atmospheric pressure. The basic parameters of the water-cooling tower influencing its thermal efficiency have been revealed. The dissipation of the kinetic energy of the air flow due to the air friction against the surface of falling droplets has been taken into account.     

Experimental study on a new internally cooled/heated dehumidifier/regenerator of liquid desiccant systems

For providing good performance of dehumidifier and regenerator with certain dimensions, a new type of internally cooled/heated dehumidifier/regenerator based on the plate–fin heat exchanger (PFHE) was designed. To investigate the behavior of the new equipment, an experimental setup was established in an environment chamber with regulable temperature and humidity air. By the internally cooled dehumidification testing, effects of the cooling water temperature, the air flow rate and the desiccant temperature on the dehumidification performance and the cooling efficiency were presented. The behavior of internally cooled dehumidification process was compared with that of the adiabatic dehumidification process. The results suggested that the cooling efficiency decreased with the increasing of the cooling water temperature and desiccant with low temperature could bring more mass transfer coefficients. There is an optimal air flow rate to achieve the maximum absolute humidity decrease of the air. By the internally heated regeneration testing, effects of the air flow rate and the desiccant inlet temperature on the regeneration performance and air outlet parameters were discussed and also compared with those of the adiabatic regeneration process. It was concluded that the regeneration efficiency of internally heated regeneration was more than that of the adiabatic regeneration, and the internally heated regenerator could offer better thermal performance.     

基于场协同理论的冷藏展示柜内流体对流换热分析

目的研究冷藏柜内对流换热机理,增强冷藏柜内流体对流换热效果,提高冷气流冷却效率。方法从冷藏柜出风口角度出发,建立数学模型,通过Ansys流体分析软件对冷藏柜内流场进行模拟仿真,应用场协同理论研究冷藏柜内流体流动及传热机理。结果出风口角度在30°附近时冷藏柜内换热效率较高且温度分布较为均匀,此时商品壁面的存在改变了冷气流流动方向。在壁面增加半圆突起后,气流沿圆弧切线方向流动,改善了速度与温度梯度之间的协同程度,从速度场、温度场及其相互作用的角度增强了冷藏柜内的对流换热效果,整体换热效率提高了38.65%。结论冷藏柜内流体流动及传热强化的根本在于流体的扰动,而出风口角度的改变和壁面凸起的存在加强了商品对流体的扰动,两者共同作用改变了冷藏柜内场的分布,进而提高了冷藏柜整体的冷藏效率,该研究可为冷藏柜的工厂化生产提供参考价值。     

Experimental study on improving operating conditions of wet cooling towers using various rib numbers of packing

There are different mass and heat transfer mechanisms between water and air flows inside wet cooling towers (WCTs) so that it is a very difficult task to manage or optimize their operations. In this experimental work, the WCT performance is parametrically investigated in order to understand effects of water flow rate, inlet water temperature, type and arrangement of packing, and mass flow rate of air. Three different types of PVC packings (7, 9 and 18 ribs) are studied in this article separately to investigate influences of rib numbers. Furthermore, operation of the WCT is investigated by changing the inlet water temperature, rib numbers of packing, and flow rate of air and water. Ultimately, a guideline is proposed to reach optimum operating conditions of WCTs by virtue of mathematical equations derived from regression analysis of the measured data.     

空调水系统节能技术分析

本文从空调水系统目前存在的问题为切入点,以节能为原则,探讨和分析了空调水系统中变流量技术应用特点和节能效果,结合工程实例,通过对水泵变频调速技术在空调水系统中的应用和相应投资、运行费用的详细分析,阐明了空调水系统采用水泵变频调速技术可以带来明显的节能效果,空调制冷系统的冷冻水、冷却水变流量系统可使冷水机组在部分负荷下运行带来显著的节能效果.     

Heat and mass transfer characteristics in a spray chamber

This paper presents a one-dimensional mathematical model for heat and mass transfer of water droplets in a spray chamber. The model includes drop size distribution and velocity of the droplets generated by a nozzle of inlet diameter 3.2 mm. By using the conservation of mass and energy, the changes in water temperature, air temperature and humidity along the spray cone in the spray chamber can be calculated. This model is tested with two different water mass flows. The results look reasonable from practical point of view and they also show that higher water mass flow results in a higher air temperature drop and higher humidity.     

基于有限测点的空调系统性能在线监测方法

智能控制技术与互联网技术在房间空调系统应用的基础是对其性能的在线实时监测。本文提出一种房间空调系统性能在线监测的方法。首先将空调器布置温度测点采集到的换热器铜管表面温度和电流电压等电路参数结合,转化为制冷循环中制冷剂的状态参数;再通过压缩机流量半经验计算模型计算制冷剂的质量流量,进而得出室内机中制冷剂侧的换热量;最后结合电路参数求得的整机功率,实现房间空调系统制冷量、制热量、功率、能效的实时监测。结果表明:采用此方法计算房间空调器性能参数的最大偏差小于15%,主要误差来源为蒸发压力的计算误差。