风机盘管加新风系统变水温节能研究

研究了在风机盘管加新风系统中冷水温度变化对末端空气处理设备换热能力、除湿能力以及冷水机组性能的影响;给出风机盘管加新风系统中室内热湿平衡方程,编制计算程序,通过计算实例表明,对于一般舒适性空调系统,质调节能够满足室内温湿度要求,节能效果明显。     

空气-空气能量回收装置对风机盘管干工况运行节能效果的分析

在风机盘管加新风空调系统中,风机盘管干工况时只承担少部分室内瞬变负荷,由于干工况下新风机组需处理的新风焓差大,存在着干工况应用困难的问题.采用空气-空气能量回收装置(AAERE)预处理新风,可以解决风机盘管干工况运行中的困难.结果表明:采用AAERE回收部分余热预处理新风,可以降低新风机组需处理的焓差值,使用热回收后新风处理焓差值降低为33.6 kJ/kg,供冷量节约16.2%,使空调系统经济运行得到保障.     

固体吸附除湿技术用于民用建筑中央空调系统的经济性分析

针对传统空调冷却除湿方式的高能耗,提出将固体吸附除湿技术应用于民用建筑中央空调系统,并对采用这种除湿方式的干式风机盘管加固体吸附独立除湿新风系统与传统的风机盘管加新风系统在运行能耗方面进行经济性实例分析,结果表明干式风机盘管加固体吸附独立除湿新风系统较传统风机盘管加新风系统其夏季空调工况每天减少约14W/m2,有效降低建筑能耗。     

温湿度独立控制空调系统的应用

温湿度独立控制系统具有避免常规空调系统中冷源能源品位的损失、满足不同热湿比变化的要求及处理设备均为干工况运行等优点。干式风机盘管加新风空调系统虽值得推广,但在运行中存在一些问题。叙述了温湿度独立控制空调系统的特点及应用,指出,利用全热交换器预处理新风是解决干式风机盘管空调系统运行困难和降低新风机组能耗的有效手段。     

全空气型温湿度独立控制空调系统

分析了传统一次回风空调系统和风机盘管加新风温湿度独立控制空调系统的优缺点,在此基础之上提出适用于卷烟生产的全空气型温湿度独立控制空调系统。风机盘管加新风温湿度独立控d P制空调系统为空气-水系统不适用于卷烟生产,全空气型温湿度独立控制空调系统吸收了其控制精确又节能的优点且解决了一次回风系统再热再湿能源浪费的问题。     

对全空气定风量系统“可调新风比”的探讨与建议

<正>在公共建筑的空调设计中,常用的空调形式为全空气系统、风机盘管+新风系统、温湿度独立控制系统。无论采用哪种空调系统,都要根据建筑内的人员密度以及空调房间内的人数,确定空调房间的新风量。对于风机盘管+新风系统、温湿度独立控制系统,新风系统完全可以根据计算的新风量设计,相应的每层的新风机房、新风竖井、排风竖井、集中的新风热回收机组都按此新风量进行设计。那么对于全空气系统,又是如何规定的呢?1相关规范对伞空气定风培系统的可调新风比要求     

热湿地区直膨式辐射顶板空调系统模拟分析

以广州地区某办公楼为例,利用Energyplus对直膨式辐射顶板空调系统进行模拟,并与风机盘管+独立新风空调系统、双冷源新风机组+辐射顶板空调系统进行能耗对比分析。结果显示,在直膨式辐射顶板空调系统中,辐射顶板承担系统69.2%的显热负荷;相对于风机盘管+独立新风空调系统,系统节能率为20.09%,相对于双冷源新风机组+辐射顶板系统,系统节能率为7.16%。     

空调冷凝水作为冷却塔补水的可行性分析

以济南某别墅工程为例,应用风机盘管加新风的系统计算了别墅冷凝水的产生量,并对产生的冷凝水用于冷却塔补水进行了可行性分析。结果表明:夏季空调冷凝水作为一种辅助性冷源如果加以利用,能实现节能的目的。     

联合国环境规划署亚太资源中心办公楼热回收空调系统应用研究

对联合国环境规划署亚太资源中心办公楼采用的新型热回收新风机加空调盘管的集中空调系统进行分析,详细阐述了热回收新风机的特点、优势及节能潜力。对办公建筑的空调系统改造具有一定的指导意义。     

中央人民广播电台业务楼蓄冰空调的应用

中央人民广播电台业务楼总建筑面积约５万ｍ２。该楼空调采用风机盘管加新风系统，经计算夏季空调设计日最高冷负荷为１３９０ＲＴ，全日总负荷为１６１６０ＲＴＨ。原设计选用三台开利产５００ＲＴ离心机组１９ＸＬ５００，每台机组分别配备一台冷水泵和一台冷却泵。电力...     

低温工况热源塔热泵系统应用试验分析

针对热源塔换热能力及热源塔联立热泵主机制热情况分别进行试验研究,并与风冷热泵的制热变化性能进行比较分析。结果表明,控制热源塔进口气液温差恒定的情况下,塔从空气中吸收的热量随环境温度的降低而增加,溶液中溶质的挥发对热源塔吸热量有重要影响;热源塔进口气液温差随环境自然变化的情况下,环境温度与蒸发温度的温差随环境温度的降低而减小,热源塔从空气中吸收的热量也随之减少。在低温工况下,虽然空气含湿量较少,但热源塔热泵系统相比于其他空气作为热源的热泵系统,在潜热换热方面有较大优势。     

Simulation of interaction between high-temperature process and heat emission from electricity system in summer

During the hot summer season, using electricity systems increases the local anthropogenic heat emission, further increasing the temperature. Regarding anthropogenic heat sources, electric energy consumption, heat generation, indoor and outdoor heat transfer, and exchange in buildings play a critical role in the change in the urban thermal environment. Therefore, the Weather Research and Forecasting (WRF) Model was applied in this study to investigate the heat generation from an indoor electricity system and its influence on the outdoor thermal environment. Through the building effect parameterization (BEP) of a multistorey urban canopy scheme, a building energy model (BEM) to increase the influence of indoor air conditioning on the electricity consumption system was proposed. In other words, the BEP+BEM urban canopy parameterization scheme was set. High temperatures and a summer heat wave were simulated as the background weather. The results show that using the BEP+BEM parameterization scheme of indoor and outdoor energy exchange in the WRF model can better simulate the air temperature near the surface layer on a sunny summer. During the day, the turning on the air conditioning and other electrical systems have no obvious effect on the air temperature near the surface layer in the city, whereas at night, the air temperature generally increases by 0.6 ℃, especially in densely populated areas, with a maximum temperature rise of approximately 1.2 ℃ from 22:00 to 23:00. When the indoor air conditioning target temperature is adjusted to 25–27 ℃, the total energy release of the air conditioning system is reduced by 12.66%, and the temperature drops the most from 13:00 to 16:00, with an average of approximately 1 ℃. Further, the denser the building is, the greater the temperature drop.     

Development of a ventilation system utilizing thermal energy storage for granules containing phase change material

We have developed an experimental ventilation system that features direct heat exchange between ventilation air and granules containing a phase change material (PCM). Measurement of outlet air temperature when the inlet air temperature was periodically varied to simulate changes of outdoor ambient air temperature showed that the outlet air temperature was stabilized and remained within the phase change temperature range. This effect is expected to be useful in practical ventilation systems. The potential of such systems for reducing ventilation load was examined through computer simulation for eight representative cities of Japan. This revealed how different temperature conditions would affect required heat storage capacity.     

压缩空气储能系统的理论分析及性能研究

压缩空气储能技术和抽水蓄能技术是两种最具潜力的电能规模化储存技术。构建了四套压缩空气储能方案,结合热力学第一定律对高压储罐内压缩空气的温度与压力参数的变化规律以及不同储能方案性能进行了比较。研究结果表明,高压储罐在与环境换热较差时,高压储罐的充气过程会经历较为明显的温升现象。200 m3储罐以1.0 kg/s流速充气至10 MPa时,温升幅度为22.46 ℃,储气过程的温升现象降低了储罐的空气容纳能力。在压缩空气储能系统性能方面,四套储能系统的热耗位于4 100 kJ/kW·h至4 200 kJ/kW·h之间,系统效率位于52.30%与56.33%之间。在储能系统效率与对外输出电能总量指标上,高压储罐与环境之间换热性能较好的储能系统均要优于换热条件较差的储能系统。     

Improved PV/T solar collectors with heat extraction by forced or natural air circulation

The photovoltaic (PV) cells suffer efficiency drop as their operating temperature increases especially under high insolation levels and cooling is beneficial. Air-cooling, either by forced or natural flow, presents a non-expensive and simple method of PV cooling and the solar preheated air could be utilized in built, industrial and agricultural sectors. However, systems with heat extraction by air circulation are limited in their thermal performance due to the low density, the small volumetric heat capacity and the small thermal conductivity of air and measures for heat transfer augmentation is necessary. This paper presents the use of a suspended thin flat metallic sheet at the middle or fins at the back wall of an air duct as heat transfer augmentations in an air-cooled photovoltaic/thermal (PV/T) solar collector to improve its overall performance. The steady-state thermal efficiencies of the modified systems are compared with those of typical PV/T air system. Daily temperature profiles of the outlet air, the PV rear surface and channel back wall are presented confirming the contribution of the modifications in increasing system electrical and thermal outputs. These techniques are anticipated to contribute towards wider applications of PV systems due to the increased overall efficiency.     

Analysis of exergy demand for air heating of an air handling unit

In modern buildings, an increasing amount of the consumed energy falls on ventilation systems. The amount of energy needed for ventilation depends on weather fluctuations, wind, interaction between natural gravity and air tightness of the building, heat exchangers used in ventilation systems, efficiency of other ventilation equipment, and operating mode of ventilation systems in the building. Ventilation systems are comprised of a variety of elements that facilitate processes using energy of different types. The main elements that use energy in ventilation systems are fans, heat exchangers, and heaters. They have a significant effect on both energy needs of a public building and the exergy efficiency of a system. In order to achieve a more efficient use of exergy in heat exchangers, it is recommended to execute processes under as little temperature difference as possible; however, this increases the area of heat exchangers. Results of the analysis show that it is recommended to design ventilation systems based on the temperature that corresponds with the maximum demand of exergy in order to use the heat recovery unit as much as possible in the system.     

Solar heat pump systems for domestic hot water

Vapour compression heat pumps can upgrade ambient heat sources to match the desired heating load temperature. They can offer considerable increase in operational energy efficiency compared to current water heating systems. Solar heat pumps collect energy not only from solar radiation but also from the ambient air. They can operate even at night or in totally overcast conditions. Since the evaporator/collector operates at temperatures lower than ambient air temperature it does not need glazing or a selective coating to prevent losses. Currently, however, they are not used much at all in domestic or commercial water heating systems. In this paper comparison is made of a conventional solar hot water system, a conventional air source heat pump hot water system and a solar heat pump water heating system based on various capital city locations in Australia. A summary is given of specific electricity consumption, initial and operating costs, and greenhouse gas generation of the three systems dealt with in this paper. The ultimate choice of unit for a particular location will depend heavily on the solar radiation, climate and the local price paid for electricity to drive or boost the unit chosen.     

Numerical Modeling of Fin Heat Exchanger in Application to Cold Storage

The fin-and-tube heat exchanger are extensively used in refrigeration systems applied to cold storage. The performance of the heat exchanger affects the efficiency of the refrigeration system. Prediction of temperature, humidity, as well as velocity distribution in a cold storage chamber requires accurate prediction of operation of the finned air cooler. The operation of the air cooler unit is usually taken into account in modeling of operation of the cold storage chambers, but with very simplified geometry and physics. On the other hand numerical investigations of the heat exchangers are focused on thermal performance mostly in order to improve the overall heat transfer coefficient or to optimize its geometry. Results of numerical modeling using the computational fluid dynamics software ANSYS FLUENT of fin-and-tube air cooler applied on a cold storage chamber is presented in the paper. Two different approaches were used: the dual cell model, and porous media conditions. Numerical predictions of air temperature as well as air velocity at the air cooler outlet were also validated on the basis of the own experimental data.     

Solar-powered systems for cooling, dehumidification and air-conditioning

This paper describes current trends in solar-powered air conditioning, which has seen renewed interest in recent years due to the growing awareness of global warming and other environmental problems. Closed-cycle heat-powered cooling devices are based mainly on absorption chillers, a proven technology employing LiBr–water as the working fluid pair. Recent developments in gas-fired systems of this type make available double- and triple-effect chillers with considerably higher COP than their single-effect counterparts, which makes it possible to reduce the amount of solar heat required per kW of cooling. These systems require, however, high-temperature solar collectors. The principles of multi-staging absorption systems are described. An economic comparison is provided which shows the total system cost to be dominated by the solar part of the system. At current prices, the high COP, high temperature alternative is still more costly than the low temperature one. Open-cycle desiccant systems employing either solid or liquid sorbents are described. While the main thrust in research on novel closed-cycle absorption systems has been toward increasing the operating temperature in order to improve efficiency through multi-staging, open-cycle absorption and desiccant systems have been developed for use with low temperature heat sources such as flat plate solar collectors. A novel open-cycle (DER) system is described, which makes it possible to use the solar heat at relatively low temperatures, for producing both chilled water and cold, dehumidified air in variable quantities, as required by the load.