Integration of variable refrigerant flow and heat pump desiccant systems for the heating season

Integration of the variable refrigerant flow (VRF) and heat pump desiccant (HPD) systems was investigated in a field performance test for a heating season. The HPD systems use only the moisture in the outdoor air and return air to humidify the indoors during ventilation in the heating season. Three different operating modes: non-ventilated, HPD ventilation assisted and HPD ventilation-humidification assisted VRF systems were investigated. It was found that the VRF systems provided an average of 93.5% of the total heating energy for the HPD ventilation assisted mode. The remainder was the recovered heat by the HPD systems during ventilation. The VRF systems provided an average of 46.8% of the total heating energy for the HPD ventilation-humidification assisted mode. The remainder was covered by the HPD systems which provided additional sensible and latent heating. Overall, among the three operating modes, it is concluded that the HPD ventilation-humidification assisted VRF outdoor units consume less energy than the HPD ventilation assisted ones (about the same energy as the non-ventilated ones), while providing the best indoor thermal comfort and indoor quality conditions. For the total system, the HPD ventilation-humidification assisted VRF systems consume less energy than the HPD ventilation assisted ones.     

Use of Simulink to evaluate the air-quality and energy performance of HRV-equipped residences in Fairbanks, Alaska

Mechanical ventilation systems in residences usually serve a single purpose, providing only a relatively small benefit compared to the capital cost. Polluted areas use mechanical ventilation to filter incoming air, cold regions use it to be able to recover the heat from the stale air going out. However, both issues – energy and air-quality – can be beneficially addressed together using one ventilation system in cold climate regions with air pollution problems, such as Fairbanks, Alaska. This paper presents a dynamic model for evaluating indoor PM_2.5 levels and energy consumption associated with ventilation. The model was verified by comparing the model-predicted real-time indoor PM_2.5 level with the actual level measured in a Fairbanks home and a good agreement (r = 0.95) was found. Then, the model was used to study three ventilation scenarios of a typical home in Fairbanks—natural ventilation, using an HRV, and using an HRV with an additional particulate filter. The external cost associated with breathing the indoor PM_2.5 was also evaluated. The scenario with an HRV and an additional filter was shown to have about $380 lower annual energy cost than the scenario with natural ventilation and the saving in the PM_2.5 associated external cost was about $690 annually. The savings were shown to exceed the operational costs of the ventilation system.     

Comparison study of a novel solid desiccant heat pump system with EnergyPlus

The variable refrigerant flow (VRF) air conditioning system usually needs to be operated with a ventilation system, since the VRF system cannot provide fresh air. The commonly used ventilation unit with the VRF system is the heat recovery ventilation (HRV) unit due to its merits of energy saving. In this study, a novel solid desiccant heat pump unit (DESICA) is introduced and mathematical model of DESICA is developed based on the dynamic building energy simulation software—EnergyPlus. The mathematical model is validated with experimental results. Based on the model, performance comparison study is conducted among the novel joint DESICA and VRF (DES&VRF) system, the conventional joint HRV and VRF (HRV&VRF) system, and the original VRF standalone with ventilation (VRFSA) system in an office building in Shanghai. Simulation results show that, HRV&VRF and VRFSA can handle the sensible load, though both of them cannot well deal with the latent load. On the contrary, DES&VRF system can keep both indoor temperature and humidity ratio at the target value, resulting in the best indoor thermal comfort than the other two systems. In addition, through the whole year, DES&VRF consumes 5% more energy than VRFSA and 20% less energy than HRV&VRF.     

HRV空调器的特性及应用

介绍了ＨＲＶ空调器的结构特性、运行及与ＶＲＶ联合运行的几种方式，并作了经济性比较。结合某联合ＶＲＶ系统运行的工程实例指出，ＨＲＶ可作为一种节能的新风空调器使用。     

Energy conservative building air conditioning system controlled and optimized using fuzzy-genetic algorithm

In this work, the combined effect of the energy conservative variable refrigerant volume (VRV) system and the variable air volume (VAV) system was experimentally investigated using genetic fuzzy optimization method that yielded better thermal comfort, indoor air quality (IAQ) requirements without compromising on the energy savings potential. The proposed system was tested using the demand controlled ventilation (DCV) combined with the economizer cycle ventilation (ECV) techniques and examined for a year-round building air conditioning (A/C) application. The supply air temperature (SAT) set points were varied under three distinct strategies and the optimal solutions obtained for the fuzzy systems designed resulted in an enhanced energy conservative potential. The test results of the proposed system were compared with the conventional fan coil A/C system. Based on the three strategies of the supply air temperature, the proposed system yielded an improved per day energy savings potential of 54% in summer and 61% in winter design conditions. Furthermore, for the strategies considered the proposed system achieved an annual energy conservative potential of 36% and exhibited more possible ways to achieve thermal comfort, IAQ and energy conservation.     

直接蒸发式全新风机组在VRV新风系统中的应用

简述了直接蒸发式全新风机组的主要特点,并对该机组作为独立的新风系统在VRV系统中应用的优势进行了分析。同时指出在进行VRV新风系统设计时,需考虑到变新风工况下系统的空气处理过程,应注意室内综合热湿比、新风终状态和VRV系统室内机的热湿处理能力三者之间的关系,通过压缩机变容量技术,调整新风机组、VRV系统室内机内冷媒流量,来维持室内状态点的稳定。     

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。     

多元VRV空调系统的设计与安装

本文根据多元VRV空调的特点,分析了在小型建筑中选用VRV空调时布置灵活、控制方便、经济节能的优势,同时也提出VRV空调系统存在的系统冷剂泄漏安全、室内空气品质、噪声等问题。对VRV空调在不同建筑规模条件下使用的经济性进行了分析,论证了在较大规模建筑中VRV空调系统投资经济性降低,一般不宜选用,比较全面地指出了VRV空调系统的局限性。此外,笔者对业主如何科学地设计VRV空调提出了意见,并列举了VRV空调系统在安装时室外机散热、冷剂管道泄漏、控制电缆敷设中常见的质量问题,对VRV空调的适用性、舒适性、安全性及安装提出了建议。     

西安某高校图书馆地源热泵空调设计分析

基于西安某高校图书馆的中央空调系统设计,利用斯维尔软件对建筑进行全年负荷计算,对地源热泵搭配电蓄热、多联机、冷水机组搭配锅炉3种空调方案进行经济性计算并对比分析,确定采用地源热泵搭配电蓄热作为该图书馆的空调冷热源。为地源热泵的节能性提供一定的依据。     

援吉布提国家图书档案馆空调系统设计

介绍了空调冷源、空调通风及防排烟的设计。冷源采用T 3高温工况的风冷直接膨胀式机组;档案库、拷贝片库、音像磁带库、典藏书库内设置独立的风冷式恒温恒湿空调机组,机组采用一次回风定风量全空气系统,机组回风口采用消声型回风口,房间内送风口采用防结露方形盘式扩散风口,其余舒适性空调采用分体空调和多联机空调;多联机空调房间设置新风换气机系统;室外设备均需采用防盐雾腐蚀型设备。     

北方冬季变容量多联机组采暖方式比较

本文对变容量多联机组空调在在北方别墅冬季采暖中的应用进行了分析,并结合石家庄市某工程对普通变容量多联机组、低温制热多联机组和水冷式多联机组三种形式进行了比较,发现以水源热泵技术为基础的水冷式多联机组空调具有明显的技术和经济优势,值得在北方冬季别墅采暖工程中推广使用.     

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.     

Field performance measurements of a heat pump desiccant unit in heating and humidification mode

In this study, a novel self-regenerating electric vapor compression heat pump desiccant (HPD) unit operated in the heating and humidification mode during the winter season is introduced. The HPD unit was installed in an office suite for the field test. The performance of the HPD unit and the provided indoor conditions were measured over a wide range of operating conditions. The target indoor humidity ratio was set to 4.4 g/kg, which is the minimum required indoor humidity ratio for a comfortable indoor environment indicated in the ASHRAE winter thermal comfort zone. The seasonal comparison revealed that even though 77.7% of all outdoor humidity ratio data was lower than 4.4 g/kg, 78.2% and 85.8% of all the indoor humidity ratio data of each room were found to be higher than 4.4 g/kg. In addition, due to the significant sensible capacity of the HPD unit, the indoor temperatures could be maintained within 20-25 °C. These results prove that the HPD unit not only properly humidifies the indoors without using any additional water source, like the conventional humidifier, but also helps to keep the indoor temperature at the desired temperature levels.     

VRV(变制冷剂流量)空调系统热回收型在建筑内区的应用及节能性分析

为了降低空调系统的能耗，对于建筑内区的房间在冬季需要供冷的情况下，可以用变频技术中的热回收型VRV（变制冷剂流量）空调系统，充分利用室内的冷量和热量，实现冷热能量在建筑物内的最佳平衡从而达到节能效果。通过对热回收型VRV中央空调系统的结构和运行原理及具体工程实例的分析，对热回收型、VRV（变制冷剂流量）空调系统在建筑内区的应用及其节能性进行了探讨。     

变频多联机系统调试中的一些典型问题及解决思路

分析变频多联机系统调试中常见的一些典型问题,如操作阀未打开、室内机电子膨胀阀工作异常、冷媒系统中混入氮气以及冷媒过多或过少等;讨论了这些典型问题的判断方法及其解决思路,以期对一线安装维修人员有所帮助.     

A PV system enhanced the performance of roof solar collector

A simple PV ventilation system was used to enhance the performance of roof solar collector (RSC) for reducing heat gain and increasing the ventilation rate inside houses. The RSC is composed of CPAC Monier concrete tiles at the outer side, air gap and gypsum board at the house side. The PV system consists of one PV panel (27 Wp), a DC electrical fan (7.3 W) installed in the gap of RSC and a control unit.

Field testing results showed that the average temperature gradient between CPAC tiles, gypsum board and room was low, about 7°C, demonstrating a high heat gain reduction. The temperature of gypsum board was very close to the indoor temperature. The average PV powered air flow rate and the corresponding air change per unit RSC were about 100–250 m³/h and 3–8 ACH, respectively. Such rates are 2–4 times higher than those obtained with the natural ventilation induced by RSC. In addition, PV-powered RSC is an interesting option in the sense that it promotes solar energy and conserve energy.     

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)。     

The effect of the ventilation retrofit in a school on CO_2,airborne particles,and energy consumptions

The energy retrofit of existing buildings is a key strategy to reduce the energy costs of the building sector.Amongst the retrofit solutions,the adoption of mechanical ventilation systems represents a necessary approach for buildings w ith high crow ding index,such as schools.The air quality in schools is a main issue since children spend a significant fraction of the year in such microenvironments. To date,the scientific literature has carried out several studies concerning the air quality in naturally ventilated schools worldwide,nonetheless most of the studies performed a general evaluation of the air quality just using the CO_2 as a comprehensive indicator. This is an oversimplified approach since the indoor air quality is affected by several pollutants,including airborne particles,whose behavior cannot be predicted by the CO_2 one.The aim of the research is the evaluation of the effect of the ventilation retrofit in a classroom on different indoor air quality parameters and energy consumption. To this end a mechanical ventilation system w ith a heat recovery unit w as installed in a testclassroom and tests w ith CO_2-based demand controlled ventilation w ere performed. CO_2 levels and indoor-to-outdoor particle concentrations w ere measured and compared to the pre-retrofit ventilation conditions( i. e. manual airing procedures).Results showed that mechanical ventilation systems have simultaneous positive effects on the different pollutants investigated as well as on ventilation heat losses: indeed,lower indoor-to-outdoor concentration ratios,with respect to the airing approach,were detected simultaneously for CO_2,sub-micron particles and PM10.     

VRV系统在娱乐建筑中的应用

通过VRV系统在公共文化娱乐建筑的设计实例,介绍了数码空调多联机系统与新风换气系统、消防防排烟系统相结合的优化空调设计方案,满足了该建筑空调系统的舒适性要求、节能要求和消防要求,为今后同类建筑采用VRV空调系统设计提供可借鉴的经验。     

Understanding the role of inhabitants in innovative mechanical ventilation strategies

The causes and implications are explored for why some inhabitants choose to avoid or abandon usage of their mechanical ventilation system. Over half of respondents in four LEED-certified high-rise residential buildings in Toronto, Canada, were found not to use their heat recovery ventilators (HRV). Questionnaire scores, comments and interview results found the following reasons: acoustic dissatisfaction, difficulty with the accessibility of filters, inhabitant knowledge and preferences, and lack of engagement with training materials. A disconnect also exists between the expectations of designers and the thinking and behaviours of inhabitants. The implications of inhabitants' ventilation behaviours were also explored though metered energy data as well as noise and indoor air quality (IAQ) measurements within their dwellings. Results suggest that abandoning mechanical ventilation in favour of passive ventilation can actually lead to greater satisfaction with IAQ and to decreased energy consumption. It is recommended that designers employ resilient design strategies that allow for varied preferences (e.g., for passive ventilation) to be exercised by inhabitants without undermining suite- or building-level performance. The study also highlights the importance of using post-occupancy evaluation methodology to understand how inhabitants interact with (new) technology in order to optimize performance and satisfaction in high-rise residential buildings.