Economical assessment of different HVAC systems for an operating room: Case study for different Turkish climate regions

In this study, the annual energy consumptions of four different heating, ventilation and air conditioning (HVAC) systems serving to operation rooms (ORs) located at five different cities (Izmir, Antalya, Istanbul, Ankara and, Erzurum) in Turkey are analyzed. The study is performed for four different HVAC systems: (a) 100% fresh air system (System I), (b) 100% fresh air with half air volume rate at night period (System II), (c) 100% fresh air with half air volume rate at night period and heat recovery unit (System III), (d) 50% fresh air with half air volume rate at night period and with heat recovery and mixing units (System IV). Life cycle cost (LCC) for 20 years life span is calculated for the considered systems. It is found that System IV considerably reduces energy consumption and it is economically proper for the considered cities. The rate of energy consumption and LCC reductions are greater for the cities with extreme climate condition having relatively low specific humidity ratio. Using System IV instead of System I reduces OR energy consumption by 74% for the city of Erzurum which has a cold and dry climate.     

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.     

蒸发冷却空调新风系统的全年应用研究

结合干热、严寒或寒冷地区全年气候特点及冬夏季建筑能耗特性,通过逐时新风能耗模拟计算,得到设置热回收装置的全年用蒸发冷却空调系统冬季新风节能量远大于夏季节能量,选用热回收装置时应重点关注冬季热回收效率,各类热回收装置中转轮热回收装置全年节能量最大,节能效果最好。基于此,深入分析了蒸发冷却空调系统冬夏季新风加湿需求、新风量变化范围和水系统管径选择,给出了全年用蒸发冷却空调机组冬季运行的防冻措施。     

绿色建筑理念在中国(泰州)科学发展观展示馆暖通空调设计中的体现

以中国(泰州)科学发展观展示馆项目为例,从暖通空调设计师的视角,介绍了《绿色建筑评价标准》在节能与能源利用和室内环境质量方面的各项细则要求。以绿色建筑三星级为目标,结合当地的气候特点,运用了地埋管地源热泵、变频调速、新风热回收、置换通风、多元通风等多项实用的节能技术,探讨了绿色建筑技术在暖通空调系统设计中的应用。     

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.     

冬季北方地区住宅建筑通风方式对比研究

随着住宅节能技术的广泛推行,对窗户的气密性要求越来越高,冬季冷风渗透远远不能满足室内人员对新风的最低需求。为了寻找节能、舒适的通风方式,本研究利用FLUENT对工程中较为常见的通风方式：自然通风方式、自然进机械排通风方式、带热交换的墙式通风器方式、带热交换的通风换气机组方式在气流组织、舒适性能、能耗特性及初投资方面进行了应用效果评价。最终得出：对于层高和装修标准较高的高级住宅中使用带热交换的通风换气机组,可以使通风系统在满足热舒适性和空气品质的基础上,更加节能,而对于一般住宅建筑,自然进机械排通风方式是相对最优选择。     

承德奥林匹克体育中心体育场暖通空调设计

介绍了该体育场供暖系统、通风及防排烟系统的设计及采用的节能措施--冬季采用地板辐射供暖系统;体育场配套用房采用变制冷剂流量(热泵)多联机空调系统加新风换气机;商业用房预留分体空调电源;内区设机械通风系统.     

Residential air-to-air heat exchangers: Performance energy savings,and economics

Residential energy consumption can be decreased if air infiltration is reduced by constructing houses more tightly. In some cases, however, reduced air infiltration can lead to problems with indoor air quality (e.g., excess humidity and high levels of indoor-generated air contaminants). One solution to this problem is to install a residential air-to-air heat exchanger. The heat exchanger provides a controlled supply of ventilation which counteracts the adverse effects of reduced infiltration. In addition, the heat exchanger recovers much of the energy that would normally be lost when ventilation occurs by air infiltration. Thus, by employing heat exchangers in low-infiltration houses, it is possible to save energy without sacrificing indoor air quality.This paper discusses the performance of residential heat exchangers and summarizes results from tests of several models. It also compares the energy consumed, during the heating season, in low-infiltration houses with heat exchangers, with the energy consumed in typical houses in four cities throughout the United States. For each city, a cost-benefit analysis is performed from the point of view of a home-owner. Houses with natural gas, oil, and electrical heating systems are considered. Our analysis indicates that the energy required to heat ventilation air in homes employing heat exchangers is 5.3 – 18.0 GJ less than the energy required to heat ventilation air in typical homes. In homes with heat exchangers, the heat exchanger's fan system required 2.2 – 3.6 GJ of electrical energy during the heating season. The net present benefit for homes employing heat exchangers, when compared with typical homes, ranged from —$1350 to +$2400 and discounted payback periods ranged from five to over 30 years. The cost-effectiveness of employing heat exchangers was found to be highly affected by climate, type of heating fuel, heat exchanger performance, and ventilation rate.     

空气热回收器在风机盘管干工况空调系统中的节能分析

在风机盘管加新风空调系统中,风机盘管干工况运行时,新风机组需要处理的新风焓差大,采用空气热回收器预处理新风,降低了新风机组处理空气的焓差值,节约了系统全年运行费用。     

A comparison of winter pre-heating requirements for natural displacement and natural mixing ventilation

In winter, natural ventilation can be achieved either through mixing ventilation or upward displacement ventilation (P.F. Linden, The fluid mechanics of natural ventilation, Annual Review of Fluid Mechanics 31 (1999) pp. 201-238). We show there is a significant energy saving possible by using mixing ventilation, in the case that the internal heat gains are significant, and illustrate these savings using an idealized model, which predicts that with internal heat gains of order 0.1 kW per person, mixing ventilation uses of a fraction of order 0.2-0.4 of the heat load of displacement ventilation assuming a well-insulated building. We then describe a strategy for such mixing natural ventilation in an atrium style building in which the rooms surrounding the atrium are able to vent directly to the exterior and also through the atrium to the exterior. The results are motivated by the desire to reduce the energy burden in large public buildings such as hospitals, schools or office buildings centred on atria. We illustrate a strategy for the natural mixing ventilation in order that the rooms surrounding the atrium receive both pre-heated but also sufficiently fresh air, while the central atrium zone remains warm. We test the principles with some laboratory experiments in which a model air chamber is ventilated using both mixing and displacement ventilation, and compare the energy loads in each case. We conclude with a discussion of the potential applications of the approach within the context of open plan atria type office buildings.     

LCA-based environmental assessment of the use and maintenance of heating and ventilation systems in Dutch dwellings

Buildings contribute significantly to the human-induced environmental burden. This comes not only from construction and demolition but also from activities throughout the operational phase – building maintenance and energy use for climate control. This paper describes how life cycle assessment (LCA) methodology can be applied to quantitatively assess the environmental performance of the use and maintenance of heating and ventilation systems. The studied climate systems include individual non-condensing boilers, condensing boilers and heat pumps on exhaust air for heating and hot tap water combined with either collective mechanical exhaust ventilation or individual balanced ventilation with heat recovery. This study shows that a heat pump causes the highest environmental burden of all the assessed climate systems due to the electricity needed for operation, high material content of the system and the refrigerant used. If the electricity used by the heat pump is generated fully by local photovoltaic cells, environmental performance will improve, but not for all environmental impact categories. Climate systems that reduce energy demand for heating, such as ventilation with heat recovery, will reduce the environmental impact related to energy use for space heating. However, if the electricity used to operate the system increases, along with the material content of the systems and distribution networks, other environmental impact categories than those related to space heating will also increase. Finally, maintenance frequency and related transportation of maintenance workers have a marginal effect on total environmental impact.     

办公建筑外墙传热系数对空调负荷的影响

采用建筑空调模拟软件DeST对我国南北6城市不同传热系数外墙的办公建筑的空调冷热负荷进行模拟计算,计算和分析的结果表明,冬季,外墙的传热系数越小,空调热负荷越小,建筑越节能;夏季的情况与冬季不同,传热系数越小,空调冷负荷越大,建筑反而不节能.室内设定温度升高或降低,空调负荷并不是按相同比例变化,因此,存在满足人体热舒适的情况下最佳室内设定温度.室外气象条件对建筑能耗节能率的影响程度在夏热冬暖地区超过了围护结构的传热系数.     

空气换热器在冷却顶板空调系统中的节能潜力

分析计算了采用不同空气换热器组合方案时CC/DV系统和CC/MV系统的新风能耗,指出两个空气热回收装置组合使用可以消除新风再热能耗,但在夏季湿热地区,排风潜热回收比消除新风再热能耗更重要,应尽可能使用全热空气换热器。     

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)。     

夏热冬冷地区高大公用建筑空调能耗特性分析

利用Energyplus软件对夏热冬冷地区高大公用建筑空调能耗进行模拟分析,通过正交试验法研究空调能耗受负荷影响因子的影响情况,给出的影响因子排序为设备负荷〉照明负荷〉人员密度〉室内设计温度〉新风量〉窗墙比〉外窗传热系数〉屋面传热系数〉遮阳系数〉外墙传热系数;进一步研究围护结构的影响因子与空调节能的关系,拟合得到节能率与围护结构影响因子间的回归方程,用于指导建筑空调节能设计及改造。     

办公建筑热回收装置节能运行模式分析

当前新风负荷占建筑能耗的比重很大,而热回收可以有效减少新风负荷。为进一步细分空调系统中热回收装置的全年运行情况,提高热回收装置的节能运行效果,针对北京地区办公建筑,以研制的热管式热交换器为例,利用De ST软件构建了办公建筑模型。空调系统采用两管制风机盘管加新风系统。引入平衡温度的概念,划分了热回收装置的全年启停时间及对应运行模式,根据标准气象年的气象数据绘制能量回收效果图,得到相应模式下的热回收量,可节省62.6%~66%的新风负荷,节能效果明显。     

热管式排风热回收在厦门地区的适用性分析

根据空调排风热回收技术存在的问题,通过具体实例,针对具体地区,分析了需选择的不同排风热回收方式,以达到真正的节能效果。主要应用动态温度和动态效率的方法,对厦门某公共建筑中所采用的热管式排风热回收技术进行节能性和经济性计算与分析,得出热管式排风热回收技术不适合用在夏热冬暖地区。通过对比显热回收与全热回收的节能效果,得出厦门地区排风热回收的适用形式。此文总结出并非所有空调系统只要采用了排风热回收技术就一定能达到节能、经济目的。     

Impact of air leakages and short circuits in ventilation units with heat recovery on ventilation efficiency and energy requirements for heating

The impact of unintentional air flows on the performance of ventilation units with heat recovery is discussed on the basis of single room ventilation units. Assuming an external short circuit (outdoor) and internal (inside the ventilation unit) air leakages, which lead to internal short circuits, a model is developed and characteristic numbers for ventilation efficiency, efficiency of heating load reduction and effectiveness of electrical energy use are derived. Differences between supply and extract air flow rates, resulting in increased air flows through cracks in the building envelope, are taken into consideration too. The use of tracer gas techniques to measure air leakage rates from ventilation units is described briefly. It is shown by numerical examples that unintentional air flows can considerably reduce the performance of ventilation units in terms of ventilation efficiency and, in combination with unintentional heat flows through the casing, energy savings. Therefore, these flows should be avoided or at least reduced to an acceptable level by an appropriate construction, manufacturing process and installation of the units.     

Primary energy implications of ventilation heat recovery in residential buildings

In this study, we analyze the impact of ventilation heat recovery (VHR) on the operation primary energy use in residential buildings. We calculate the operation primary energy use of a case-study apartment building built to conventional and passive house standard, both with and without VHR, and using different end-use heating systems including electric resistance heating, bedrock heat pump and district heating based on combined heat and power (CHP) production. VHR increases the electrical energy used for ventilation and reduces the heat energy used for space heating. Significantly greater primary energy savings is achieved when VHR is used in resistance heated buildings than in district heated buildings. For district heated buildings the primary energy savings are small. VHR systems can give substantial final energy reduction, but the primary energy benefit depends strongly on the type of heat supply system, and also on the amount of electricity used for VHR and the airtightness of buildings. This study shows the importance of considering the interactions between heat supply systems and VHR systems to reduce primary energy use in buildings.     

板式空气全热交换器在上海地区的应用性分析

以实际工程运用为例,分析了板式空气全热交换器引入空调系统后对于系统运行能耗的影响.根据实测数据计算了全热交换器的全热效率、潜热效率和显热效率,并且得出了在设备使用年限内静态和动态投资回收期分别为2.8年和3.3年.板式空气全热交换器在上海地区具有很好的应用前景.