地表水换热盘管换热特性的理论与试验研究

建立了地表水换热盘管的换热模型.对换热盘管在不同换热工况下的换热性能进行了测试,分析了管内外流速、管径及放热或吸热工况对换热性能的影响,分析了换热盘管换热量与盘管长度的关系,给出了不同接近温差时吸热量与盘管长度的关系曲线图.     

适用于湿工况的风机盘管简化换热模型

针对半集中式空调系统风机盘管的换热计算问题,通过干湿工况转换方法,设计了一种适用于湿工况的风机盘管换热模型.根据能量平衡和热传递原理,简化了该换热模型,使换热量仅由冷水流量、进水温度、盘管风量和进风温度等独立控制变量确定.在实际风机盘管上进行了仿真验证,得到了不同工作条件下的换热曲线.实验结果表明,该简化换热模型计算精度较高.     

空气处理机组的冷却盘管特性研究

空气处理机组实际运行过程中的参数变化对换热特性有较大影响。通过模拟计算得出了各种工况条件下的一次回风定风量空气处理机组的换热特性变化规律和变风量空气处理机组的换热特性。结果表明,冷却盘管入口空气参数和入口水温的变化对定风量空气处理机组的换热特性影响显著,而冷却盘管入口空气参数对变风量空气处理机组几乎没有影响。     

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     

热管换热器回收燃气热水器烟气余热研究

采用热管换热器回收燃气热水器烟气余热(显热、潜热),对热管换热器设计计算方法、换热量的理论计算方法进行探讨。结合试验方法,利用热管换热器回收家用燃气热水器烟气显热、潜热,考察不同工况下热管换热器理论换热量与实测换热量。在试验中回收到了凝结水,说明设计的热管换热器具备同时回收烟气显热和潜热的能力。由于蒸发段翅片间残留凝结水,影响了换热效果,使得实测显热、潜热换热量小于理论换热量。在后续的研究中,可以通过优化翅片结构等方式,减少凝结水的残留,进一步提高热管换热器的换热能力。     

结霜工况下闭式热源塔内翅片间距的模拟优化

为优化闭式热源塔内宽翅片盘管在结霜工况下的换热性能,本文对宽翅片盘管内部的热湿交换过程进行了分析,建立了稳态的数值模型。并利用Matlab自编程序,分析了结霜工况下不同翅片间距对盘管换热性能的影响。结果显示,翅片间距为2.0 mm时,盘管具有最佳的换热性能,在满足换热量的前提下,应优先选取大翅片间距来降低设备成本。     

数码涡旋多联式空调系统节能性探讨

本文针多联式空调系统在实际运行时是否节能的问题,基于不同建筑面积的4个办公建筑模型,分析了数码涡旋多联式空调系统、定风量全空气系统和风机盘管加新风系统在实际运行时,室外工况、区域负荷和运行时间3个因素对其运行能耗的影响,并分析了能耗差异的原因.结果表明,与定风量全空气系统和风机盘管加新风系统相比,数码涡旋多联式空调系统在变工况时的调节特性最好;在变负荷工况下,是否存在定风量全空气系统或风机盘管加新风系统比数码涡旋多联式空调系统节能的空调开启率分界点及其分界点值的大小取决于建筑负荷与空调系统部分负荷性能之间的匹配;与定风量全空气系统相比,数码涡旋多联式空调系统的室内机个性化调节的特性使其在房间的空调运行时间参差时更为节能.     

重庆某剧院空调系统板式换热器检测及诊断分析

针对某剧院中央空调系统效果不佳的问题进行检测诊断,现场测试了板式换热器实际运行工况。通过对实测换热量的修正,得到设计温差换热量QST和设计温差流量换热量QSTF,将其与额定换热量QS对比,以此作为判断板式换热器换热性能的依据。最后,就板式换热器的实际运行情况给出了相应的建议以及诊断其性能的步骤。     

风机盘管机组风量测试技术方案优化设计和分析

围绕风机盘管机组的性能要求,阐述智能化自动控制风洞式空气焓值风机盘管性能测试系统的组成,对额定风量检测的要求进行了详细的分析,采用涡街式流量计取代喷嘴,将平衡风机设计优化,满足标准实验工况的检测要求。     

风机盘管机组冷、热量综合表达式与应用

本文在分析影响风机盘管机组冷、热量因素的基础上,建立了综合表达式。可将风机盘管样本中标准工况(试验工况)下的热工性能数据,转变成各种使用工况下的热工性能数据,导出风机盘管水系统质调节与量调节的计算公式,为设计选用与运行调节提供了数学表达式。     

基于热湿分控的恒温恒湿空调机组性能的研究与分析

对已有的带热回收式直流变频恒温恒湿空调机组制冷性能进行了实验,提出了串级控制的热湿分控方法。在性能测试实验中,不同的风机频率与压缩机频率对显热与潜热有不同的影响。实验结果显示,当风机频率一定时,随着压缩机频率升高,显热与潜热相应增加;当压缩机频率一定时,显热与潜热增加程度会有所差异,应根据显热与潜热变化来控制室内的温湿度。     

Efficiency of energy recovery ventilator with various weathers and its energy saving performance in a residential apartment

The energy recovery ventilator (ERV) is an effective method, which can transfer heat and moisture from the exhaust air into the outdoor fresh air to save energy in buildings. Nowadays, ERV has been widely used in the commercial, industrial and residential buildings in China. Its energy saving performance depends on a lot of factors, such as the outdoor environmental conditions, the enthalpy efficiency of the exchanger, and so on. Based on the relationship among sensible heat, latent heat and enthalpy efficiency, we analyzed the weighted coefficient equations for describing the performance of ERV in different climatic zones in China. According to China weather data, enthalpy efficiency of the exchanger mainly depends on sensible heat efficiency in winter and latent heat efficiency in summer. The energy simulations of a sample apartment in a residential building were made under different operation conditions to study the performance of ERV. The energy saving performances of the ERV were studied with five different outdoor climatic conditions, the enthalpy efficiency, fan power consumption of ERV and fresh air change rate. To improve energy saving performance, better efficient enthalpy exchange material and higher effiencient fans must be explored, while reasonable fresh air change rate as well as proper operation period according to local climate should also be carefully considered.     

Membrane heat exchanger in HVAC energy recovery systems, systems energy analysis

The thermal performance of an enthalpy/membrane heat exchanger is experimentally investigated. The heat exchanger utilizes a 60gsm Kraft paper as the heat and moisture transfer surface for HVAC energy recovery. The heat exchanger sensible, latent and total effectiveness have been determined through temperature and moisture content measurements. The annual energy consumption of an air conditioner coupled with an enthalpy/membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using in-house modified HPRate software. The heat exchanger effectiveness are used as thermal performance indicators and incorporated in the modified software. Energy analysis showed that an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system in hot and humid climates where the latent load is high. It has been shown that in humid climate a saving of up to 8% in annual energy consumption can be achieved when membrane heat exchanger is used instead of a conventional HVAC system.     

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。     

相变热回收式通风装置的研发及性能测试研究

随着建筑节能标准的提高,建筑外窗气密性要求不断提高。靠门窗渗透的自然通风量已不能满足室内空气质量的要求。采用机械通风的方式引入新风也存在着通风量的大小及通风模式会影响建筑节能的问题。为此,将相变蓄能技术应用于民用建筑的机械通风系统,研发出一种相变热回收式通风装置,以更好地解决室内空气质量和节能问题。所研发装置利用相变材料的蓄、放热性能,通过交替运行的通风模式,以及通风装置的不断循环,实现无管道式的相变热回收式建筑通风系统。主要采用实验研究的方法,在人工气候室内对研发样机进行了2个蓄、放热周期(4种工况)的测试研究。结果表明,相变热回收式通风装置的进口温度恒定、出口温度随时间不断变化,不同时间阶段呈现不同的变化趋势。第一时间阶段,即初始阶段,出口温度随时间变化剧烈,表明相变蓄能装置进入相变阶段,相变潜热量不断增大。第二时间阶段,即相变阶段,出口温度随时间呈线性变化,表明相变蓄能装置温度恒定,与空气流体发生稳定的相变传热。第三时间阶段,即完成阶段,出口温度变化小,基本接近进口温度,表明相变蓄能装置相变结束。从相变传热机理进行分析,固-液相变传热过程主要包括液态显热蓄(放)热、相变潜热蓄(放)热和固态显热(蓄)放热3个阶段,实验过程中出口温度随时间变化呈现出的几个时间阶段的不同规律,与相变传热机理有关联且相互对应。相变热回收式通风装置的风量恒定、不同进口温度工况下的对比数据表明,进口温度与相变温度的温差越大,初始阶段的出口温度变化越剧烈,相变阶段的出口温度线性变化率越大,且蓄、放热效率越高。进口温度与相变温度的温差约17℃时,蓄、放热效率分别达到56.2%(蓄)、50.8%(放)。     

Experimental investigation of dehumidification process in cooling coil by utilizing air-to-air heat exchanger in humid climate of Iran

Energy recovery systems can be used in HVAC to reduce energy consumption by recovering wasted energy from the exhausted air to pre-cool inlet fresh air. In this paper, experimental study of utilizing cooling coil (CC) and cooling coil combined with heat exchanger (CCHE) has been developed. Considering the different climate zones in Iran, the experimental study has been done for the areas with high humidity content. In each case, the effects of air-to-air heat exchanger (HE) on the sensible and latent cooling load are investigated. The analysis gives the applicability of HE in Iran for various operational conditions to obtain air with lower moisture content. In CCHE systems more latent load quota is allocated in cooling coils and lower air humidity ratio can be obtained. Also in the cities with higher dew point depression (difference between dry-bulb and dew point temperature) more humidity reduction is achieved and the difference between latent load quotas of CCHE system is higher than CC system.     

Applicability and optimum control strategy of energy recovery ventilators in different climatic conditions

Energy recovery ventilators (ERVs) transfer energy between the air exhausted from building and the outdoor supply air to reduce the energy consumption associated with the conditioning of ventilation air. In this paper, the applicability of ERVs with sensible and latent effectiveness values in a practical range is studied using TRNSYS simulation program. The impact of ERV on annual cooling and heating energy consumption is investigated by modeling a 10-storey office building in four American cities as representatives of major climatic conditions. The results show that heat and moisture recovery can lead to a significant reduction in the annual heating energy consumption (i.e., up to 40%, which is 5% higher than heat recovery). Also, an ERV with the capability of moisture recovery may reduce the annual cooling energy consumption by 20% provided the ERV is properly controlled. Since the un-controlled operation of ERVs during the summer may increase the cooling energy consumption, an optimum control strategy is developed and verified in the paper. This optimum control strategy depends on ERV's latent to sensible effectiveness ratio. For instance, an ERV with equal sensible and latent effectiveness should be operated when either the outdoor enthalpy or temperature is greater than that of the indoor air.     

游泳馆空调负荷计算探讨

通过对游泳馆内池水蒸发换热及池水与室内空气之间的显热换热分析,推导出池水蒸发潜热负荷计算公式。结合工程实例,计算了池水蒸发潜热量,得出池水蒸发潜热负荷是空调负荷的一个重要影响因素。     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.