肋片管蒸发器结霜对传热性能影响的实验研究

实验研究了低温条件下肋片管蒸发器结霜对传热性能的影响,得到了肋片间距、相对湿度、风速与传热系数的关系曲线,为低温环境中肋片管蒸发器的设计应用和除霜时间的选择提供参考。     

Impact of individually controlled facially applied air movement on perceived air quality at high humidity

The effect of facially applied air movement on perceived air quality (PAQ) at high humidity was studied. Thirty subjects (21 males and 9 females) participated in three, 3-h experiments performed in a climate chamber. The experimental conditions covered three combinations of relative humidity and local air velocity under a constant air temperature of 26 °C, namely: 70% relative humidity without air movement, 30% relative humidity without air movement and 70% relative humidity with air movement under isothermal conditions. Personalized ventilation was used to supply room air from the front toward the upper part of the body (upper chest, head). The subjects could control the flow rate (velocity) of the supplied air in the vicinity of their bodies. The results indicate an airflow with elevated velocity applied to the face significantly improves the acceptability of the air quality at the room air temperature of 26 °C and relative humidity of 70%.     

成都双流机场T1航站楼冬季室内参数实测与分析

2010年冬季对该机场航站楼室内相关空调设计参数进行了测试,分析了温度、相对湿度及风速的测试结果。结果表明,冬季航站楼室内存在温度偏高、相对湿度偏低,大厅冷风侵入严重等问题。各参数分布特性可为航站楼气流组织的优化设计及空调系统控制提供参考。     

Experimental analysis of energy recovery for humidity control in split A/C system

This study presents a proposed idea about making use of the thermal energy rejected by the condenser in a water-cooled split-air-conditioning systems to decrease the relative humidity of the cold air supplied by such air conditioners. Most of split air-conditioner systems cool air without controlling its humidity. An amount of heat is rejected from the air conditioner, through the condenser, into the surrounding in order to allow the refrigerant to cool down and condense, thus, part of the lost energy can be exploited to decrease the relative humidity of the sub-cooled air that leaves the evaporator as saturated humid air. Four variables, viz. the coil type (single or double), the amount of flowing water, water, temperature, and the cooled air velocity were studied to find out the optimum conditions required for this purpose. The requisite amount of heat that may adjust the relative humidity of the conditioned air was also determined. The experimental results suggest an optimum design of a heat exchanger for performing the use of the heat rejected from the condenser to achieve the aim. As a result, the proposed heat recovery concept can be worthily adopted to achieve economic results in large-scale systems.     

Numerical study of time-dependent hygrothermal conditions in depressurized crawl space

A finite element based hygrothermal model consisting of several interconnected components with varying number of spatial dimensions was applied to analyze the time-dependent temperature and humidity conditions of a mechanically depressurized and ventilated crawl space. Purpose of the depressurization is to prevent the intrusion of radon or other insanitary particles into indoor air. However, in typical foundation structures the depressurization will cause airflow from soil into the crawl space air and it may convey excessive moisture making the hygrothermal conditions potential for mould growth or other moisture-induced biological damage, which is not considered to be acceptable even with the depressurization. Although in general the forced convection of humidity from soil presumably increases relative humidity in crawl space, significant heat capacity of the ground may warm the air flowing into the crawl space and thus decrease the relative humidity. Overall effect of the depressurization on the conditions in crawl space is therefore not trivial. Because a full-scale three-dimensional finite element analysis of heat, mass and momentum transfer in crawl space and its surroundings would require excessive computational resources, several simplifications were necessary to apply in the model. According to the numerical results, the airflow through drainage layer into crawl space does not seem to have severe effect on the crawl space conditions. Conversely, in cold periods the relative humidity in crawl space is very low because of the air temperature is increased while flowing through the drainage layer.     

HEMS深井降温系统研发及热害控制对策

 深井高温热害作为深部煤炭资源开采中的严重灾害,高温不仅影响了围岩的力学性质,而且严重影响矿井安全生产,因此,必须进行深入研究。针对国内外矿井降温技术存在的问题,提出了以矿井涌水作为冷源的深井开采高温热害控制HEMS技术,运用提取出的冷量与工作面高温空气进行换热作用,降低工作面的环境温度及湿度。该技术结合夹河矿深井降温工程,建成了国内第一个控制深井热害的深部科学与工程实验室(DUSEL)。系统运行结果表明,工作面温度降低4 ℃～6 ℃,最高温度控制在28 ℃～29 ℃,相对湿度降低5%～10%,极大改善了井下工作环境,热害控制效果显著,具有广阔的推广应用前景。     

多层墙体热湿耦合传递模型及验证

从非平衡热力学角度论证了多层墙体热湿耦合过程采用水蒸气分压力和温度作为驱动势的合理性。由于水蒸气分压力是含湿量和温度的函数,利用全微分思想,建立了多层墙体热湿耦合传递模型,该方法可避免Budaiwi方法在热湿耦合模型建立过程中采用的空气含湿量与相对湿度间的近似表达式,而且简化了方程系数,便于方程的求解。通过对多层墙体求解结果的对比,验证了该模型的有效性。     

不同人体座位模型对大空间空气分布影响

本文对座椅送风系统的气流组织进行模拟研究,首先运用座椅送风的简化模型,模拟了人体座椅实体的简化模型和虚区域热源模型下气流组织的情况,分析了两种情况的温度场,速度场和相对湿度场,发现人体座椅实体模型模拟的剧院气流组织速度、湿度与温度分布分层更加明显,此特点更易于微气候的分区控制,用更少的能量达到人体舒适的满意度。该研究为大空间建筑空调系统优化设计、模拟气流组织提供了方法及理论依据,同时对研究空气分布对空调系统的舒适性和节能方面的影响有一定的帮助作用。     

喷淋工况下闭式热源塔传热特性

建立了闭式热源塔的数学模型,利用MATLAB自编程序,实现了对喷淋工况下热源塔的数值模拟,并将计算结果与实验结果进行了比较。利用程序得到了喷淋工况下的闭式热源塔内喷淋溶液、载热流体、空气焓值的分布,结果表明:塔内空气焓值呈线性分布,翅片换热器上半部分换热效果比下半部分好,塔的中部位置附近最先出现结霜现象,空气干球温度高于5.1℃,相对湿度高于75%,闭式热源塔热泵系统没有结霜风险,可以停止喷淋泵,有助减少热泵系统的运行能耗。     

室外热环境评价指标湿球黑球温度简化计算方法

针对室外热环境评价指标湿球黑球温度在实测和数值计算中都比较难获得的问题,在湿热地区广州夏季收集了空气干球温度、湿球温度、黑球温度、相对湿度、风速、太阳辐射和湿球黑球温度等数据,对收集的数据进行相关性分析和回归分析,相关性分析结果表明：空气温度、相对湿度、太阳辐射与湿球黑球温度具有一定的线性相关度,可以采用上述三个气象因子作为湿球黑球温度的简化计算参数;回归分析结果表明：回归的关联式与实测湿球黑球温度的相关性较高,并且满足多元线性回归的各项检验,认为该回归方程具有较高的可信度,可以在城市热环境的实测评价和数值预测过程中,作为湿球黑球温度的简化计算方法应用。