Review of research into and application of chilled ceilings and displacement ventilation systems in Europe

This paper discusses the origination, development and current status of chilled ceilings, displacement ventilation and combined systems. Current knowledge of chilled ceilings (including ceiling panels and beams), displacement ventilation and combined systems is summarised and a comprehensive review of research into chilled ceilings and displacement ventilation systems is presented. Research work has been categorized, and some conclusions made. Opportunities for further work are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermal performance of a closed wet cooling tower for chilled ceilings: measurement and CFD simulation

A closed wet cooling tower, adapted for use with chilled ceilings in buildings, was tested experimentally. The thermal efficiency of the cooling tower was measured for different air flow rates, water flow rates, spray flow rates and wet bulb air temperatures. CFD was also used to predict the thermal performance of the cooling tower. Good agreement was obtained between CFD prediction and experimental measurement. Copyright © 2000 John Wiley & Sons, Ltd.     

Chilled ceilings and displacement ventilation

Displacement ventilation and chilled ceiling systems have been promoted as being ‘greener’ alternatives to other common forms of air conditioning system. They have been viewed by some of the building services industry as a welcome departure from the traditional ‘North American’ systems of air conditioning most frequently adopted to date, and could be viewed as a more suitable alternative for use in the moderate climatic conditions of the UK.This paper reviews some of the authors' recent and current work on the performance of these systems in office environments.     

Chilled ceiling and displacement ventilation system for energy savings: A case study

This paper studies the design and performance of cooled ceiling and displacement ventilation (CC/DV) systems application for buildings in Beirut for the purpose of saving energy. The transient thermal response of spaces cooled by the combined CC/DV system is needed for performance assessment. For that reason, the plume‐multi‐layer model of CC/DV cooled spaces is extended to transient applications. A design procedure for the combined CC/DV system in Beirut humid climate and buildings is developed to insure that both indoor air quality and comfort are satisfied within the conditioned zone. The contribution of the proposed procedure is that it guarantees that the stratification height (occupied zone) is at 1.1 m taking into consideration the plumes from internal sources and non‐isothermal walls. The design procedure is applied to a case study in Beirut to design a system for a typical office space at 85 W m^?2 sensible cooling load. The CC/DV system size is compared with the size of a conventional mixed convection system. It is found that the size of the CC/DV system is 10.2 kW compared to conventional system size of 7.9 and 13.4 kW at the 30 and 100% fresh air supply, respectively. For the same indoor air quality and thermal comfort level, the CC/DV system consumed 21% less cooling energy than the conventional 100% fresh air system over the cooling season. The initial cost of the CC/DV system is higher, but the pay back period based on transient operation is less than 5 yr. Copyright © 2006 John Wiley & Sons, Ltd.     

辐射供冷系统末端形式对比及发展研究

介绍几种辐射供冷空调的末端形式,比较冷吊顶、楼板辐射供冷、毛细管席的供冷能力、热舒适性、能耗及投资等方面的不同,并建议完善辐射供冷系统试验研究方法,着重进行拥有自主产权产品的制造工艺的研究。     

Experimental study for comparison of thermal comfort and air age between two combined ventilation systems with chilled ceiling considering occupant density

Due to the global spread of diseases and epidemics, the need to maintain a clean indoor atmosphere has received increasing attention in recent years. Therefore, there will be a need to clearly estimate and define the areas that affect human exposure to pollutants, taking into account the occupied density, which is the primary importance of this research. The capacity of the chilled ceiling combined with mixing ventilation and personal ventilation systems has been studied and compared to the chilled ceiling with mixing ventilation in terms of mean air age, temperature distribution, CO₂ concentration, and thermal efficiency, with the best flow rate of the proposed system considering the occupied density in a thermally insulated office room experimentally in the climate of Iraq (Hilla, a hot and dry climate). Twelve tests were performed for four different cooling loads with cooled ceilings (0%, 0.25%, 50%, and 80%), at a constant supply air flow rate with two PV airflow modifiers for three cases. As the cooling load treated by a chilled ceiling increased, the average air temperature increased with height in all cases. The lowest values of average air age appeared in the occupied area in the case of a chilled ceiling with mixing ventilation. This study shows that the chilled ceiling combined with a mixing ventilation and personal ventilation system with a flow rate of 7.5 L/s provides thermal comfort and higher air quality in the occupied area. based on the values of air exchange efficiency and occupants’ air exchange efficiency. As a result, a flow rate of 7.5 L/s is the best option for protecting occupants from direct pollution in the breathing zone and in the surrounding microclimate, because the lower the ventilation rate, the less air is changed for occupants.     

顶板冷辐射加置换通风空调系统评价分析

介绍了顶板冷辐射与置换通风相结合的空调系统特点,分析了该系统在改善室内空气品质和满足人体的热舒适性方面的特点,评价了该系统的节能效果和经济性。     

空调冷冻水泵变频能耗特性的研究

通过分析冷冻水管路特性随空调负荷变化的特点 ,得出了计算空调冷冻水泵变频调速运行总能耗的一般关系式。研究表明 ,在中央空调系统中 ,由于冷冻水管路特性曲线随空调负荷而变化 ,在确定水泵变频调速运行的能耗时已不能直接应用泵的相似定律 ;变频冷冻水泵的能耗并不与转速或流量的三次方成正比 ,而是与空调负荷、空调用户的流量分配及空调用户的位置等有关。     

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。     

吊顶辐射冷却塔供冷系统试验研究与性能分析

通过供冷试验及TRNSYS软件模拟研究了吊顶辐射冷却塔供冷系统的运行效果,分析了气象参数、部件结构等因素对系统供冷效果的影响,并与常规供冷系统全年的运行能耗进行对比。试验与理论分析结果表明,吊顶辐射冷却塔供冷系统的有效供冷量能够满足用户供冷需要,供冷房间温度稳定且分布均匀。冷却塔供冷效果与大气湿球温度、建筑内部负荷、热交换器结构等因素有关。辐射顶板末端与冷却塔供冷匹配性高,系统全年运行时数增加,应用于需全年供冷的建筑节能效果显著。     

空调冷冻水变主流系统运行能耗分析

比较了单级泵、双级泵、变主流系统等三种冷冻水系统的特点 ,对其能耗进行了对比分析 ,认为变主流系统能耗低、系统简单 ,有广泛的应用前景     

多污染热源置换通风的应用与节能

简述了多污染热源置换通风的原理、特性及其与混合通风的比较 ,列举了工程应用实例 ,并对其节能效果进行了分析讨论 ,指出多污染热源置换通风是一种值得推广的通风方式     

Simplification of analytical models and incorporation with CFD for the performance predication of closed‐wet cooling towers

Simplified analytical models are developed for evaluating the thermal performance of closed‐wet cooling towers (CWCTs) for use with chilled ceilings in cooling of buildings. Two methods of simplification are used with regard to the temperature of spray water inside the tower. The results obtained from these models for a prototype cooling tower are very close to experimental measurements. The thermal performance of the cooling tower is evaluated under nominal conditions. The results show that the maximum difference in the calculated cooling water heat or air sensible heat between the two simplified methods and a general computational model is less than 3%. The analytical model distribution of the sensible heat along the tower is then incorporated with computational fluid dynamics (CFD) to assess the thermal performance of the tower. It is found that CFD results agree well with the analytical results when the air flow is simulated with air supply from the bottom of the tower, which represents a uniform air flow. CFD shows the importance of the uniform distribution of air and spray water to achieve optimum design. Copyright © 2002 John Wiley & Sons, Ltd.     

Parametric analysis of space cooling systems based on night ceiling cooling with PCM‐embedded piping

A parametric analysis is conducted for space cooling systems based on cold water flowing, during the night, within regularly arranged pipes embedded in a layer of phase change material (PCM), located among the structural layers of the ceiling. The introduced PCM layer in conjunction with night cooling add to the usual ceiling cooling systems offers the advantages of low energy consumption, high cool storage capacity, operation under reduced night electricity price, smoothing of electricity consumption by eliminating daily peak loads, improved thermal comfort and elimination of ceiling dripping. Our parametric analysis is based on a transient three‐dimensional finite‐difference solution of the related heat‐transfer problem for various values of all the main system parameters. PCM phase change process is simulated by using the effective thermal capacity function, which is determined experimentally for PCM suitable for air‐conditioning applications. Our tests showed that the main parameters of the system are pipe spacing, PCM layer thickness, pipe depth within the ceiling, cooling water inlet temperature, night cooling duration and PCM properties (thermal conductivity, phase change heat and ends of phase change temperature range). The effect of all the above parameters is analysed and suggestions are made for selecting the proper combinations of their values in order to obtain the lowest energy consumption in conjunction with the highest level of thermal comfort. Copyright © 2010 John Wiley & Sons, Ltd.     

A new type of cooling ceiling panel with corrugated surface—Experimental investigation

In this paper a new type of cooling ceiling panel with corrugated surface has been studied experimentally. A heat flux and a heat transfer coefficient for the new type panel were compared with the reference values obtained for a panel of a flat surface. It was shown that increase of the new panel cooling performance results both from increase of its area and from enhancement of natural convection heat transfer. For typical operation conditions, the increase of the new type panel cooling capacity varies from 26 to 55%, in comparison with the reference panel. In addition, the new type panel is more resistant to the risk of dew point and enables the achievement of higher EER values by the heat pump cooperating with it.     

A comprehensive state‐of‐the‐art survey on power generation expansion planning with intermittent renewable energy source and energy storage

Generation expansion planning (GEP) is a power plant mix problem that identifies what, where, when, and how new generating facilities should be installed and when old units be retired over a specific planning horizon. GEP ensures that the quantity of electricity generated matches the electricity demand throughout the planning horizon. This kind of planning is of importance because most production and service delivery is dependent on availability of electricity. Over the years, the traditional GEP approaches have evolved to produce more realistic models and new solution algorithms. For example, with the agitation for green environment, the inclusion of renewable energy plants and energy storage in the traditional GEP model is gradually gaining attention. In this regards, a handful of research has been conducted to identify the optimal expansion plans based on various energy‐related perspectives. The appraisal and classification of studies under these topics are necessary to provide insights for further works in GEP studies. This article therefore presents a comprehensive up‐to‐date review of GEP studies. Result from the survey shows that the integration of demand side management, energy storage systems (ESSs), and short‐term operational characteristics of power plants in GEP models can significantly improve flexibility of power system networks and cause a change in energy production and the optimal capacity mix. Furthermore, this article was able to identify that to effectively integrate ESS into the generation expansion plan, a high temporal resolution dimension is essential. It also provides a policy discussion with regard to the implementation of GEP. This survey provides a broad background to explore new research areas in order to improve the presently available GEP models.     

Estimating the potential yield of small building‐mounted wind turbines

The wind profile in the urban boundary layer is described as following a logarithmic curve above the mean building height and an exponential curve below it. By considering the urban landscape to be an array of cubes, a method is described for calculating the surface roughness length and displacement height of this profile. Firstly, a computational fluid dynamics (CFD) model employing a k‐? turbulence model is used to simulate the flow around a cube. The results of this simulation are compared with wind tunnel measurements in order to validate the code. Then, the CFD model is used to simulate the wind flow around a simple pitched‐roof building, using a semi‐logarithmic inflow profile. An array of similar pitched‐roof houses is modelled using CFD to determine the flow characteristics within an urban area. Mean wind speeds at potential turbine mounting points are studied, and optimum mounting points are identified for different prevailing wind directions. A methodology is proposed for estimating the energy yield of a building‐mounted turbine from simple information such as wind atlas wind speed and building density. The energy yield of a small turbine on a hypothetical house in west London is estimated. The energy yield is shown to be very low, particularly if the turbine is mounted below rooftop height. It should be stressed that the complexity of modelling such urban environments using such a computational model has limitations and results can only be considered approximate, but nonetheless, gives an indication of expected yields within the built environment. Copyright © 2007 John Wiley & Sons, Ltd.     

Investigation of energy transportation capability of a phase change slurry through a cold storage‐cooling coil system

Microencapsulated phase change materials slurries (MEPCM slurries) have the advantage that they can be used as heat transport and storage medium, and therefore provide improved continuity of energy transport. Energy transportation capability of a MEPCM slurry based on Rubitherm RT6 through a cold storage‐air handling system was investigated for various concentrations and pump powers. The transport properties of the MEPCM have been identified. The optimum concentration for maximum energy transportation capability and energy transportation effectiveness of the system has been found. This investigation is intended for determination of the optimum concentration of MEPCM slurry for an air conditioning system that uses MEPCM slurry as a secondary cooling medium directly into air handling units and stored for load shifting. Copyright © 2009 John Wiley & Sons, Ltd.     

Heating and cooling of a hospital using solar energy coupled with seasonal thermal energy storage in an aquifer

A system is being designed, using solar energy in combination with Aquifer Thermal Energy Storage (ATES), that will conserve a major part of the oil and electricity used for heating or cooling the Cukurova University, Balcali Hospital in Adana, Turkey. The general objective of the system is to provide heating and cooling to the hospital by storing solar heat underground in summer and cold in winter. As the main source of cold energy, ventilation air at the hospital and surface water from the nearby Seyhan Lake will be used.