室内湿度对多联机空调性能的影响研究

通过运用焓差试验室对某品牌多联机空调机组进行试验,测试在相同室外温度、相同室内干球温度、不同室内湿球温度下多联机空调机组的各种性能参数变化情况,并且对其制冷量、能效、耗功、潜热显热量、潜热显热比、除湿量等进行了对比分析.试验结果表明:室内温度相同的情况下,室内相对湿度从35%增加到75%,机组制冷量增加了21.02%,耗功量增加了6.23%,能效增加了13.97%;当室内相对湿度小于35%的时候,机组能力全部靠显热来提供;在湿度较高和较低的情况下可以通过改变系统的控制方式来改变压缩机的运行频率,降低功耗,实现节能.     

横流热源塔换热性能研究

针对制热工况,建立横流热源塔传质传热数学模型。对数学模型的计算准确性进行实验验证。选取重庆、长沙、杭州、西安、南京、青岛6座城市作为计算对象,分析计算热源塔显热换热量、潜热换热量的影响因素以及一定计算条件下的显热换热量、潜热换热量。计算结果与实验测量结果偏差很小,数学模型的计算结果可信。进口防冻液温度的影响:当防冻液、空气质量流量一定时,6座城市的显热换热量、潜热换热量均随进口防冻液温度的升高而减小。进口防冻液温度相同时,显热换热量、潜热换热量由大到小的城市均为重庆、长沙、杭州、南京、西安、青岛。防冻液质量流量的影响:重庆、长沙、杭州、南京、西安、青岛的进口防冻液温度分别选取-4、-8、-9、-11、-12、-14 ℃,空气质量流量一定时,6座城市热源塔显热换热量、潜热换热量均随防冻液质量流量的增大而增大,但潜热换热量增大幅度非常小。空气质量流量的影响:重庆、长沙杭州、南京、西安、青岛的进口防冻液温度分别为-4、-8.-9、-11、-12、-14℃,防冻液质量流量一定时,6座城市热源塔显热换热量、潜热换热量均随空气质量流量增大而增大。空气质量流量对重庆热源塔潜热换热量的影响最明显,其次分别为长沙、杭州、南京、西安,对青岛热源塔潜热换热量的影响微弱。一定计算条件下,6座城市热源塔显热换热量差别比较小,而潜热换热量差别明显,室外空气含湿量越大的城市热源塔潜热换热量越大。     

冷凝热回收热水系统的应用研究

分析了冷凝器热回收系统的工作原理,证实冷凝热回收既能减少冷却塔的热排放负荷量,又能用以制取生活热水.结合工程实例,通过对在压缩机排气口增加换热器的冷凝热回收系统进行定量分析,在设计工况下,得到了冷凝器中显热和潜热所占的比例,其中,冷凝热的显热部分占总冷凝热的14.2％,液化潜热占80.6％,过冷热量只占5.2％.并且,热水流量和热回收率都随热水的出水温度升高而降低.     

板翅式空气全热交换器热回收效率的实验研究

通过一系列实验,研究了热湿交换材料特性、通道长度和运行工况等因素对全热交换器热回收效率的影响。利用经典传热、传质理论对实验结果进行了分析,指出当上述因素发生变化时,全热交换器潜热交换效率受到的影响大于显热交换效率。     

四种温度控制方法对相对湿度影响的比较

模拟比较了定风量变水量、变风量变水量、旁通型变风量、二次回风控制四种方法在部分负荷时的除湿能力.结果表明,定风量变水量控制在部分负荷时,室内相对湿度一直较高.除湿能力很差;旁通型变风量控制除湿能力较强;变风量变水量控制在潜热不变显热变化的情况下除湿能力较差,而在潜热显热都变化的情况下较好;二次回风控制只在实际显热比较小时除湿能力较差.     

无填料热源塔冬季吸热量分析

利用搭建的无填料热源塔实验平台实验,分析空气温度、相对湿度、溶液入口温度、气水比对热源塔吸热量的影响,对吸热量中的潜热吸热量和显热吸热量进行对比。结果表明:空气温度升高,溶液总吸热量增大但潜热吸热量减小;总换热量和潜热换热量随着相对湿度增高而增大,相对湿度较低时会抑制潜热换热量;气水比升高,热源塔吸热量增加;溶液入口温度升高,潜热吸热量和显热吸热量同时减少。     

基于ECR400型风机盘管性能影响因素实验研究

对以ECR400型为代表的风机盘管在不同运行工况下的性能在焓差实验室内进行了实际测试。分别得到在夏季制冷工况及冬季制热工况下,不同室内空气温度、风机盘管供水温度、供水流量以及风机盘管送风量等对风机盘管性能的影响。实验结果表明:室内空气温度、风机盘管供水温度、供水流量等对风机盘管制冷(热)与除湿性能都有显著影响,送风量的变化对风机盘管除湿性能的影响较小。本实验结论对风机盘管的设计选型及运行维护具有一定的指导意义     

基于能耗考虑的交叉流显热换热器性能评价方法

提出了根据实验数据和ε-NTU关系式求解交叉流板式显热换热器各种通道形式对流传热关联式的方法.考虑到换热器会给空调系统带来阻力损失,建议用回收热量与风机有效功率的比值来评价换热器的节能性能,并对两种通道形式的交叉流板式显热换热器进行了性能比较.     

变水量对风机盘管全热,湿热,潜热冷量的影响

本文提出了风机盘管采用变水量调节时，水流量变化引起的全热、显热、潜热冷量以及供回水温差变化的规律，分析了这一变化导致室内相对湿度升高的机理，并提出了解决这一问题的初步设想方案。     

变水量对风机盘管全热、显热、潜热冷量的影响

本文提出了风机盘管采用变水量调节时，水流量变化引起的全热、显热、潜热冷量以及供回水温差变化的规律，分析了这一变化导致室内相对湿度升高的机理，并提出了解决这一问题的初步设想方案。     

Experimental study on a residential temperature-humidity separate control air-conditioner

According to the temperature and moisture characteristics and current problems experienced in the Yangtze River Area, a temperature-humidity separate control air conditioner was developed. This unit can remove indoor sensible heat and latent heat load separately, and adjust indoor temperature and humidity respectively, thus improve indoor comfort and reduce energy consumption. The air-conditioner consists of an air cooling evaporator and a water cooling evaporator. Orthogonal experiments were designed to study the influence of outdoor temperature, indoor temperature, indoor humidity, compressor frequency, and refrigerant distribution ratio in air cooling evaporator (RDRAE) on the unit performance. The results showed that the dehumidification capacity ranged from 0 to 4.02 kg/h; the EER ranged from 2.71 to 4.57; the cooling capacity ranged from 6822 to 13,080 W. The results can help to make the control logic of the unit, and be used as the basis of energy consumption calculation. Units with temperature and humidity separate control could save about 15.6% of the cooling energy consumption against traditional residential air-conditioner, and 47.8% against the traditional residential air-conditioner that could control both indoor temperature and humidity.     

集中空调系统各环节温差及提高性能的途径分析

从换热温差的角度分析了常规集中空调系统各环节的特性,研究了换热温差对空调系统投入的换热面积、输配能耗和制冷机组能耗等的影响.根据显热、潜热负荷的不同特点介绍了温湿度独立控制空调系统的理念,并分析了温湿度独立控制系统各环节中的温度分布情况.介绍了进一步提高新风处理过程性能及温度控制系统性能的方法,以某办公建筑为例分析了采用不同形式的集中空调系统方案时在换热温差、系统性能等方面的差异.     

An experimental study on the inherent operational characteristics of a direct expansion (DX) air conditioning (A/C) unit

For residential buildings located in the subtropics, direct expansion (DX) air conditioning (A/C) units are commonly used for environmental control. However, the use of standard DX A/C units having constant-speed compressor and relying on on–off cycling often leads to either space overcooling or an uncontrolled indoor humidity level, due to high latent cooling load resulted from hot and humid climates. This paper reports on an experimental study to investigate the inherent operational characteristics of a DX A/C unit at a fixed inlet air state when the speeds of both its compressor and supply fan are varied. The experimental results of the inherent operational characteristics related to both equipment sensible heat ratio (SHR) and operating efficiency are reported. Issues related to the practical applications of the inherent characteristics and their possible constrains are discussed.     

南京某别墅温湿独立控制空调系统的设计

地源热泵联合毛细管网辐射末端应用于别墅中,能够结合二者的优点,充分利用低品位能源,节能效果显著。毛细管网辐射末端配合置换通风系统实现了温湿度的解耦,毛细管网承担几乎全部的显热负荷,新风系统承担潜热负荷,做到温湿度独立控制,能够创造超高的热舒适性和室内环境品质。防结露控制系统通过实时的温湿度监测和流量调节,避免房间结露,保障了系统正常运行。热回收系统为别墅提供基本生活热水,不仅平衡了负荷,而且进一步提高了能源的综合利用效率。     

基于地下室恒温恒湿空调机组的控制策略研究

基于已有的直流变频变风量恒温恒湿空调机组,针对地下建筑常年湿度较大的情况,提出一种变频变风量结合主、副电子膨胀阀的多变量控制策略,并通过LabVIEW软件实现编程控制。为验证控制方法的可行性,采用模拟负荷发生器在实验室中模拟地下空间的实验热湿环境特征,根据机组处理的热湿能力选取不同热湿负荷工况下进行实验室温湿度控制实验。实验结果表明,在此控制方法下该恒温恒湿机组能满足实验工况下的地下空间热湿的控制要求,在两组总负荷不同的情况下,干球温度和相对湿度都能稳定在设定值附近,系统的控制精度和稳定性良好。     

Multivariable control of indoor air temperature and humidity in a direct expansion (DX) air conditioning (A/C) system

Controlling indoor humidity at an appropriate level is very important since this affects occupants' thermal comfort and indoor air quality (IAQ). The paper presents an investigation on developing a multi-input multi-output (MIMO) control strategy for simultaneously controlling the indoor air temperature and humidity by varying the speeds of both compressor and supply fan in an experimental DX A/C system. The MIMO-based controller was designed based on the linearized dynamic model of the experimental DX A/C system. The Linear Quadratic Gaussian (LQG) technique was used in designing the MIMO-based controller. The controllability tests with respect to both the disturbance rejection capability and the command following capability were carried out to assess the control performance of MIMO controller. The results of disturbance rejection capability test showed that the MIMO control strategy can effectively maintain the indoor air temperature and humidity to their respective settings after an unmeasured heat load disturbance was imposed by simultaneously varying speeds of both the compressor and the supply fan of the DX A/C system. Furthermore, in the command following capability test for indoor air temperature, the test results showed that the indoor air temperature can be controlled to its new setting while indoor humidity remained unchanged. Similar test results were also observed in the command following capability test for indoor humidity. Therefore, the MIMO controller developed can effectively control indoor air temperature and humidity simultaneously by varying compressor speed and supply fan speed of the DX A/C system. Compared to the previous related studies using conventional on–off control method or single-input single-output (SISO) control strategy, which can only effectively control either air temperature or relative humidity, the MIMO controller can simultaneously control the indoor air temperature and humidity with adequate control sensitivity and accuracy. The application of MIMO control strategy developed can be extended to other HVAC systems in the future to improve their operating performance and energy efficiency.     

A comparative study of different control strategies for indoor air humidity

There has been a rising concern in controlling the high indoor humidity of hot and humid countries. When an air-conditioned space experiences only part of its design heat load, its humidity tends to rise as a result of the air-conditioning system trying to control the indoor temperature by reducing its cooling capacity. In this study, the part-load dehumidification performances of three temperature control strategies are compared, namely, chilled water flow control, bypass air control and the variable air volume control. Coil simulations are employed to study the part-load performance of these control strategies. The coil model has been validated with experimental data to within ±6.5%. The relative humidity of a space depends of factors such as design sensible heat factor of the space, temperature control strategy employed and load condition experienced by the space. Simulation results have indicated that chilled water control strategy results in the highest indoor humidity throughout the range of conditions studied while variable air volume system provides highly effective dehumidification performance of the cooling coil. Bypass air control appears to be a good option for adoption as it is able to provide an acceptable humidity over a wide range of load conditions without having to affect the air movement within the space.     

夏热冬冷地区民用建筑除湿方式的适用性分析

本文对常见的几种空气除湿的原理进行了分析,针对夏热冬冷地区的建筑气候特点,比较了冷冻除湿、通风升温除湿、被动除湿、干式除湿和复合式除湿等各自的特点和适用场合。分析了该地区空气处理设备实现温湿度独立控制的必要性,强调了空调设备设计选型时不能只考虑设备显热冷负荷,说明了湿度控制对空气处理设备设计选型的要求,提出了独立新风系统集中除湿和室内空气湿度独立控制的重要途径,并从室内环境质量综合控制角度指出了民用建筑空气除湿技术和该地区空气湿度控制方式的发展趋势。     

The characteristics of space cooling load and indoor humidity control for residences in the subtropics

For residential buildings located in the subtropics, it is more challenging and difficult to deal with space latent cooling load than space sensible load, using a room air conditioner (RAC), partly due to hot and humid climates. This paper reports a simulation study on the characteristics of space cooling load and indoor humidity control for residences in the subtropics, using a building energy simulation program. Both the weather conditions and the typical arrangements of high-rise residential blocks in subtropical Hong Kong were used in the simulation study. The simulation results on both the space cooling load characteristics and the hourly application sensible heat ratio (SHR) in the living/dining room and the master bedroom in a selected west-facing apartment under different operating modes of RACs in the summer design day are presented. The problem of indoor humidity control due to the mismatching between an application SHR and an equipment SHR in the two rooms both in the summer design day and during part load operations and the influences of indoor furnishings acting as moisture capacitors on indoor RH level are discussed.