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.     

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     

飞机座舱应用置换通风系统的节能分析

通过置换通风系统和混合通风系统的比较,阐述了置换通风系统的特点和优势.运用暖通空调领域设计置换通风系统的方法,并结合ISO7730 - 2005、ASHRAE62 - 1989和民航飞机相关标准对座舱通风的规定,以节能分析的方式得出了置换通风在飞机座舱通风系统应用上的节能优势.     

EnergyPlus软件在置换通风设计中的应用研究

介绍了EnergyPlus软件中的置换通风模型,采用EnergyPlus辅助某办公室置换通风系统设计,并采用CFD软件模拟了室内温度分布,结果表明,EnergyPlus可以精确地预测置换通风系统负荷,系统设计能满足热舒适要求。     

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.     

剧场观众厅空调风系统设计及数值模拟

介绍了大连市开发区文化中心主剧场观众厅的空调风系统设计方案。建立该主剧场观众厅有关速度场和温度场的数学模型,利用ICEMCFD和Fluent软件采用SIMPLE算法对此大空间内的气流组织和温度分布进行模拟,验证了设计方案的可行性,设计中采用置换通风的通风效率可达到1.67。     

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。     

地板送风与置换通风特性比较

介绍了置换通风与地板送风的原理。从原理出发,对地板送风与置换通风在气流组织、通风效率、 空气品质和热舒适等方面的特性进行了比较。     

置换通风的研究与应用现状

简述了置换通风的原理,回顾了置换通风应用的发展过程,总结了置换通风系统的优缺点,介绍了置换通风的设计方法和设计关键参数的确定,分析了置换通风的工作机理,介绍了置换通风的CFD研究,并指出置换通风是一种值得推荐的暖通空调方式。     

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.     

A natural ventilation wind tower with heat pipe heat recovery for cold climates

Commercial wind towers are passive ventilation technology based on traditional wind towers of the Middle East. Typical operation of wind towers in cold – mild climates is generally limited to summer-seasons as the outdoor air is too cold to be introduced into spaces for the majority of the year. In addition, the use of natural ventilation solutions has been seen to increase heat loss in buildings and lead to increased energy cost. Wind towers are normally shut down for the sake of avoiding indoor heating energy losses during winter months. Consequently, the concentration of pollutants has seen to rise above the guideline levels, which can lead to ill health. To improve the year-round capabilities of wind towers, a heat recovery system utilising the combination of heat pipes and heat sink was incorporated into a multi-directional wind tower. This study investigates the potential of this concept through the use of numerical analysis and wind tunnel experiments for validation. The findings showed that the wind tower with heat pipes was capable of meeting the required ventilation rates above an inlet air velocity of 1 m/s. In addition to sufficient ventilation, the integration of heat pipes had a positive effect on thermal performance of the wind tower; it raised the supply air by up to 4.5 K. The technology presented here is subject to a patent application (PCT/GB2014/052263).     

济南办公建筑自然通风工况下自然室温的研究

针对济南地区一办公房间,讨论不同的换气次数、围护结构和建筑朝向对自然室温影响的变化规律。指出夜间通风和节能50%的围护结构能获得适宜的自然室温,建筑朝向对自然室温的影响较小。     

Simulation of the metal hydride heat pump system with the single and double reactors

The main obstacles for the practical use of a metal hydride heat pump (MHHP) system are a low-heat transport rate of the metal hydride and a relatively large irreversible heat loss during the hydriding and dehydriding processes. Very extensive investigations are required to overcome these obstacles, which are both time-consuming and costly. In order to save both time and cost, computer simulation can be introduced in the development of such MHHP systems. In particular, simulation can provide useful technical knowledge for improving the system by optimum reactor construction and identification of optimum operational parameters.In this work, a simulation method for the MHHP system, based on the three-vector equilibrium space of temperature, concentration and enthalpy, is proposed and tested practically. Using a computer simulation program for a single reactor MHHP system driven by a given pressure or flow rate of hydrogen, it was possible to describe equilibrium properties of hydride as they are changed by variations in temperature and concentration. Simulation of the MHHP system with two reactors, i.e. one metal hydride pair, allowed the thermodynamics of a conventional system to be described theoretically.     

Numerical modelling of air temperature and velocity in a forced ventilation piggery

IntroductionPigs are reared under more intensive conditions thanother fanned animals because of their unique nature.Their growth vales with their living environment andthey are very responsive to the climatic variationll'2'31.Therefore, they are subjected to intensive environmentcontrol and management for higher productivity. Mostprevious research conducted to predict the thermalconditions inside a piggery, whether steady or transientwas based on the one-dimensional heat balance. Someexamples…     

日照作用对热源建筑自然通风影响的研究

参照变电站主变压器室，建立了双侧开口热源建筑数值模型，通过改变大气透过率（sunshine fraction）的大小改变日照强度，利用FL U EN T进行求解，考察日照作用对热源建筑自然通风流动的影响。计算结果表明：日照作用影响热源建筑室内外热量传递的大小和方向，当大气透过率为0．15时，室内外两侧传递热量达到平衡。较大的日照强度导致通风量增大，室内气流速度分布更均匀，日照作用下不同高度的气流温度受到的主要影响因素不同。     

Influence of edge velocity on flame front position and displacement speed in turbulent premixed combustion

Using a novel concept, the present study experimentally investigates underlying physics pertaining to statistics of the flame front position and the flame front velocity in turbulent premixed V-shaped flames. The concept is associated with characteristics of the reactants velocity at the vicinity of the flame front, referred to as the edge velocity. The experiments are performed using simultaneous Mie scattering and Particle Image Velocimetry techniques. Three mean streamwise exit velocities of: 4.0, 6.2, and 8.6 m/s along with three fuel–air equivalence ratios of: 0.7, 0.8, and 0.9 are examined. The results show that fluctuations of the flame front position and the flame front velocity are induced by the fluctuations of the component of the edge velocity transverse to the mean flow direction. Analysis of the results show that the mean of the flame front velocity in the normal direction to the flame front is significantly dependent on the vertical distance from the flame-holder. Relatively close to the flame-holder, the mean of the flame front velocity in the direction normal to the flame front is about zero; however, it increases to values several times larger than the laminar flame speed by increasing the vertical distance from the flame-holder.     

舰船局部空调区与高温环境区的传热研究

分析了送风流量对舰船局部空调区的速度场、温度场的影响和局部空调区与环境区的显热与潜热传递情况，得出了局部空调区的有效半径、高温环境区向局部空调区传递的显热流量和潜热流量与送风量和风口安装高度的关系。     

自然通风的策略形式及模拟分析

介绍了自然通风的策略形式 ,阐述了采用网络法和CFD对自然通风的模拟分析。最后提出了自然通风的策略选择和模拟分析中要注意的几个问题。     

Transient temperature distributions in canned products during heat sterilization and cooling

This reseach was performed using experimental temperature data and a simple analytical model to estimate the temperature distributions at the centres of cylindrically canned products (diameter/thickness ratio = 4/1) during heat sterilization and cooling under continuous flow conditions for two retort temperatures (115 and 121°C). The recorded experimental temperature data for an individual can for two different retort temperatures were then used to construct the dimensionless experimental centre temperature curves. In order to predict dimensionless centre temperature profiles with a mathematical model, the convection boundary condition (i.e. 0·1 < Bi < 100) in transient heat transfer was considered. The predicted temperature profiles were compared with the experimental centre temperature measurements for two cases—heat sterilization and cooling. The experimental temperature values were in very good agreement with the theoretical predictions. The results of this study show that the present technique is a reasonable tool for estimating in a simple and accurate form the temperature distributions of a cylindrically canned product subject to both heat sterilization and cooling.