Thermal comfort analysis of a low temperature waste energy recovery system: SIECHP

The use of a recovery device is justified in terms of energy savings and environmental concerns. But it is clear that the use of a recovery system also has to lead to controlling indoor environmental quality, nowadays a priority concern. In this article, experimental research has been carried out whose aim is to study the thermal comfort provided by a combined recovery equipment (SIECHP), consisting of a ceramic semi-indirect evaporative cooler (SIEC) and a heat pipe device (HP) to recover energy at low temperature in air-conditioning systems. To characterize this device empirically in terms of thermal comfort (TC), Fanger's predicted mean vote (PMV), draught rate, and vertical air temperature difference were used in this study as the TC criteria.     

空调分区系统中几种空调方式的探讨

本文首先指出在办公建筑中,合理的进行内外分区是实现温度均匀分布的关键。说明了在空调分区系统中,采用适当的空调方式给内、外区供冷供热,是减小能耗、节约能源的重要措施。其次介绍了三种在空调分区系统中可以采用的节能的空调方式,分别为:利用冷却塔给内区供冷、以乙二醇为载冷剂给内区供冷及采用变风量调节。并根据工程实例详细讲述了这三种空调方式的使用的环境、工作原理及优缺点。指出这三种空调方式都可以充分利用天然能源,减小能耗。     

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.     

Performance of energy recovery ventilator with various weathers and temperature set-points

Based on the generic dynamic building energy simulation environment, EnergyPlus, the simulation model of energy recovery ventilator (ERV) is developed in this paper. With different indoor temperature set-points, the energy performance of ERV along with the availability of ERV is investigated both for Beijing and Shanghai weathers in China in terms of the ratio of heat recovery to energy supply by HVAC devices and ERV. Simulation results show that the seasonal average of the ratio is linear with indoor temperature set-points. The availability of ERV in Shanghai is better than that in Beijing during the winter. In summer, the utilization of ERV is uneconomical if the indoor temperature set-point is higher than 24 °C for the Beijing climate. The indoor temperature set-points have the reverse effects to the availability of ERV in the mid-season and to that in the hottest months. Meanwhile, the heating amount recovery in summer and the cooling amount recovery in winter, both of which impair the strong points of the energy recovery, are analyzed quantitatively.     

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.     

Energy simulation and analysis of the heat recovery variable refrigerant flow system in winter

Heat recovery variable refrigerant flow (HR-VRF) system can supply cooling and heating for the building simultaneously and make good use of the indoor cooling and heating capacity efficiently. This system has a good energy performance and can meet the emerging requirements of modern buildings. In order to evaluate the energy features of the system, a new energy simulation module is developed and embedded in the dynamic energy simulation program, EnergyPlus. Using the program with the newly developed module, the dynamic energy simulation is performed for a simplified typical commercial building. The indoor thermal comfort of the building in winter and the setting temperature of the system are analyzed. Based on the simulation results, the energy characteristics of the system are investigated, and it is indicated that different methods of the temperature control and the percentage of the heat recovery have influence on the relative ratio of the energy saving. If the HR-VRF system adopts the same temperature control method as the heat pump VRF (HP-VRF) system, the HR-VRF system promises 15-17% energy-saving potential, when compared to the HP-VRF system.     

北方地区某新风能量回收系统用户风机盘管冻裂原因分析

分析了该住户风机盘管在供暖初期冻裂的原因——空气-空气能量回收系统新风送风温度低于0℃,指出为防止送风温度过低导致盘管冻裂,应避免在住宅供暖设计中采用将新风直接送入热水盘管再热的方式。     

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.     

冷凝热回收系统中的热水系统设计探讨

结合一座典型星级酒店,提出了一套应用冷凝热回收的热水系统设计方案,并通过对补水方式、运行工况等内容的优化设计进一步降低能耗。     

带冷凝热回收的直流变频恒温恒湿空调机组热湿分控实验研究

基于已有的带冷凝热回收的直流变频恒温恒湿空调机组,提出了一种串级控制的热湿分控方法。为了验证该控制方法的可行性,对机组出风温湿度控制效果和被控房间的温湿度控制效果进行了测试。实验结果表明,采用该控制方法的恒温恒湿机组能满足实验工况下的热湿控制要求,送风温度控制精度为±0.2℃,送风含湿量控制精度为±0.2g/kg,被控房间的干球温度控制精度为±0.04℃,被控房间的露点温度控制精度为±0.02℃。     

Passive climate control in Spanish office buildings for long periods of time

Recent studies have shown that the effect of the internal wall coating on an indoor thermal environment can be seen for short periods of time [Hameury S. Moisture buffering capacity of heavy timber structures directly exposed to an indoor climate: a numerical study. Building and Environment 2005;40(10):1400–12]. However, for long periods of time this effect is hidden by the air renovation and vapour release. These passive methods are gaining popularity because they are energy conscious and environmentally friendly. However, there is little published data on mass transfer between building envelopes and indoor air [Simonson CJ, Salonvaara MH. Mass transfer between indoor air and a porous building envelope: part I—field measurements. In: Proceedings of healthy buildings, vol. 3, 2000; Simonson CJ, Tuomo O. Moisture performance of buildings envelopes with no plastic vapour retarders in cold climates. In: Proceedings of healthy buildings, vol. 3, 2000]. The main objective of this study is to show the internal wall coating effect on indoor air conditions by means of the indoor air parameters. These measurements were taken in 25 office buildings during different seasons. Our results will allow us to understand the internal coating effect for long and short periods of time and, therefore, the thermal comfort and indoor air quality conditions.     

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.     

Validation of a supervisory control system for energy savings in membrane bioreactors

The application of fixed operational protocols and settings for membrane bioreactors (MBR) often leads to suboptimal filtration conditions due to the dynamic nature of mixed liquor characteristics. With regard to process optimization and energy savings, the potential benefits of a dynamic control system, enabling to adapt fouling control actions (ACS outputs) in an automated way to the actual mixed liquor fouling propensity, are thus obvious. In this paper, the pilot-scale validation of such an advanced control system (ACS) is elaborated. A specific on-line fouling measurement method, the MBR-VFM (VITO Fouling Measurement), was used for the evaluation of the mixed liquor’s reversible fouling propensity, which was used as a primary ACS input parameter. A first series of tests with a gradual increase in complexity of the selected input and output parameters indicated the functionality of the ACS and demonstrated a substantial reduction of aeration, however sometimes at the expense of a higher fouling rate. The ACS was further fine-tuned and subsequently tested for a longer period under more dynamic operating conditions. A significant correlation was found between the reversible fouling potential measured by the MBR-VFM and the on-line permeability, indicating that the MBR-VFM is a suitable ACS input. Furthermore, an average 22% reduction in aeration flow to the membranes could be achieved without any obvious negative effect on filtration performance. This indicates that this approach is promising to optimize energy consumption in MBRs.     

Performance testing of a counter-cross-flow run-around membrane energy exchanger (RAMEE) system for HVAC applications

A novel run-around membrane energy exchanger (RAMEE) system is designed, built, and tested for heating, ventilating, and air-conditioning applications. The RAMEE system consists of two counter-cross-flow liquid-to-air membrane energy exchangers, one located in the supply and the other in the exhaust air streams of a building. Inside each exchanger, a micro-porous membrane separates the air and desiccant solution streams. This membrane allows heat and water vapor exchange between the two streams. The RAMEE system thus exchanges sensible and latent energy between the supply and exhaust air streams by using a desiccant solution as the energy carrier that is pumped in a loop between the two exchangers. The RAMEE performance is evaluated by testing the system with various air and desiccant solution flow rates during standard summer and winter operating conditions. During summer test conditions, the total system effectiveness increases with increasing desiccant flow rate, but decreases as the air flow rate increases. Under winter test conditions, the total effectiveness changes little with changes in the air and desiccant flow rates. For some test conditions, the maximum total effectiveness of the system is between 50 and 55%. The effectiveness data are compared to available correlations and reasons for discrepancies are discussed.     

四管热泵热回收型空调系统及其能耗分析

简要介绍了四管热泵热回收型空调系统的构造和运行，给出了用于评价整个系统综合性能的系统能效比的定义，分析了系统全年能效比随建筑冷热负荷比Ｋ的变化规律，指出在一定的Ｋ值范围内，四管热泵系统既能够满足不同用户的冷热需求，又能实现节能运行，能效比高于通常的双管热泵系统。     

废轮胎媒介-A2/O工艺的脱氮性能研究

将废轮胎切碎后与乙烯-乙酸乙烯酯共聚物(EVA)及沸石按一定比例混合制成一种辅助媒介,并添加至A2/O工艺的好氧段,考察了对脱氮效果的影响.试验结果表明,投加该媒介后可在好氧段内产生大量的微缺氧区,当维持污泥浓度为3～4 g/L、DO为1.6～2.4 mg/L以及进水C/N值为9～11、pH值为7.7～8.1的条件下,取得了较好的同步硝化反硝化效果,使脱氮能力提高了约13%.     

The use of a double heat pipe heat exchanger system for reducing energy consumption of treating ventilation air in an operating theatre—A full year energy consumption model simulation

In two earlier papers [Y.H. Yau, Application of a heat pipe heat exchanger to dehumidification enhancement in tropical HVAC systems—a baseline performance characteristics study, International Journal of Thermal Sciences 46 (2) (2007) 164–171; Y.H. Yau, The analysis of enthalpy change with and without a heat pipe heat exchanger in a tropical air conditioning system, International Journal of Energy Research 30 (15) (2006) 1251–1263], two series of experiments were conducted under controlled conditions to establish the baseline performance characteristics of the heat pipe heat exchanger (HPHX). In the present paper, a complete empirical transient systems simulation program model is assembled to estimate the air states as well as the entire typical meteorological year energy consumption of an operating theatre located in Kuala Lumpur, Malaysia.     

Application of an energy management and control system to assess the potential of different control strategies in HVAC systems

The significant and continuous increment in the global electricity consumption is asking for energy saving strategies. Efficient control for heating, ventilation and air-conditioning systems (HVAC) is the most cost-effective way to minimize the use of energy in buildings. In this framework, an energy management and control system (EMCS) has been developed to schedule electricity end-uses in the campus of the Universidad Politécnica de Valencia (UPV), Spain. This paper presents an evaluation performed by using the EMCS of different control strategies for HVAC split systems. It analyzed the effect of different schedules for a common air-conditioning device and demand response strategies are tested in several situations. The economic saving is calculated taking into account the electricity contract clauses. Finally, a test is made for the control of a group of similar devices in order to reduce the maximum peak power in consumption and to obtain a flexible load shape with the HVAC loads. The studies are then extrapolated to a larger system, the whole University campus, for which energy and economic savings are quantified.     

乙二醇热回收空调系统的节能分析

介绍了带乙二醇循环装置热回收空调系统的组成,工作原理,并以上海某建筑为例,比较了绕流二盘管,绕流三盘管及常规的采用再热的空调系统的能耗,认为在上海地区,采用绕流二盘管系统可节能23．3％,采用绕流三盘管系统可节能46．6％,绕流环路热回收技术在空调节能方面具有广阔应用前景。     

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.