Energetic efficiency of room wall containing PCM wallboard: A full-scale experimental investigation

A wallboard new PCM material is experimentally investigated in this paper to enhance the thermal behavior of light weight building internal partition wall. The experiments are carried out in a full-scale test room which is completely controlled. The external temperature and radiative flux dynamically simulate a summer repetitive day. The differential test concern walls with and without PCM material under the same conditions. The PCM allows to reduce the room air temperature fluctuations, in particular when overheating occurs. A numerical modeling has been used to investigate energy storage. Five millimeters of PCM wallboard double the energy that can be stocked, and destocked, during the experiment. The experiments are fully described so that the results can be used for the validation of numerical models dealing with phase change materials.     

Experimental and theoretical investigation of non-isothermal transfer in hygroscopic building materials

In this paper a modified two-dimensional Luikov model for evaluating the non-isothermal moisture migration in porous building materials was proposed. The coupled heat and moisture transfer problem was modeled. Vapor content and temperature were chosen as the principal driving potentials. The coupled equations were solved by a numerical method, which consists of a finite difference technique with a fully implicit scheme in time. Two validation experiments were developed in this study. The evolution of transient moisture distributions in both one-dimensional and two-dimensional cases was measured. A comparison between experimental results and those obtained by the numerical model proves that they are fully consistent with each other. The modified model can be integrated into a whole building heat, air and moisture transfer model.     

Economic feasibility of thermal energy storage systems

This paper investigates the economic feasibility of both building an ice thermal storage and structure a time of rate tariff for the unique air conditioning (A/C) plant of the Grand Holy Mosque of Makkah, Saudi Arabia. The features of the building are unique where the air-conditioned 39,300 m² zone is open to the atmosphere and the worshippers fully occupy the building five times a day, in addition hundreds of thousands of worshippers attend the blessed weekend's prayer at noontime, which escalates the peak electricity load.     

Potential use of cold thermal energy storage systems for better efficiency and cost effectiveness

The present article deals with the employment of combined heat and power (CHP) micro gas turbines using natural gas and cold thermal energy storage system (CTES) in Tehran (with mild climate), Bandarabas (with hot and humid climate) and Kerman (with semi-hot climate). A micro CHP produces electricity to meet the electrical energy needs of the building, and it is also considered to meet part of the heating, cooling and domestic hot water energy needs through a heat pump and refrigeration system. A detailed study considering the effect of CTES system on the selection of micro gas turbines of a residential building located in Tehran is performed. The results show that since the number of micro gas turbines is dependent on the maximum cooling load required in the summer using CTES system reduces the CHP micro gas turbine units from 21 to 11 and costs from US$ 1,133,221 to US$ 799,061 (29.5% economical) for the residential building which is located in Tehran. Also, using this system in Kerman and Bandarabas reduces the micro CHP gas turbine units from 21.75 to 11.40, respectively.     

新型气动PCM控制系统的试验研究

本对采用三个气源的新型气动控制系统，进行了详细地试验研究，针对试验中出现的问题，提出了一些解决措施，试验结果表明：新型气动ＰＣＭ控制系统能获得±０．３ｍｍ的定位精度，并具有较好的跟踪性能。     

LNG气化站冷能利用的冷库系统设计

以福建省LNG项目的发展背景,确定LNG气化站冷能在冷库的利用实现模式和系统设计工艺设计,提出冷库冷能系统和低温集中空调系统综合应用设计方案的可行性。     

Modeling of a solar-assisted HVAC system with thermal storage

A numerical model of the solar-thermal-assisted heating, ventilation and air conditioning system in a 7000 m² educational building, situated in a high-desert climate, is used to predict performance and optimize control parameters. Heating, cooling and shoulder seasons are considered in the study. It is found that the solar assist can account for over 90% of the total heating requirements if certain energy conservation strategies are adopted. The solar cooling assist can reduce the total external cooling energy requirement by between 33% and 43%, the latter result achieved, surprisingly, at lower solar array operating temperatures. In the shoulder season, it is possible to operate the building without any external contribution, by heating the building in the coldest hours of the day, and using any excess heat to produce chilled water, to be stored and used when required. Operation of the solar-assisted system within a much larger district energy system makes it possible to achieve maximum performance.     

Experimental study of a ground sink direct cooling system in cold areas

A conception with ground as a heat sink directly for cooling of the buildings in cold areas is presented. A corresponding experimental system was constructed in Harbin area and operated in summer in 2006. Some important performance parameters, such as the cooling seasonal performance factor (CSPF) and the average heat rejection rate unit depth of borehole, were obtained and some analyses for the system characteristics are made. The experimental results show that the ground sink direct cooling system (GSDCS) presented has great potentialities in energy saving within a specified region.     

某大型冷库消防安全评估

冷库建筑相对封闭,且建筑内部处于低温环境,具有特殊的火灾危险.针对某大型冷库存在防火分区面积过大等问题,对货架间的热辐射蔓延进行计算,并利用FDS对冷库火灾烟气流动和热辐射蔓延进行模拟分析.开展疏散实验,测得人员在黑暗中行走速度为0.66 m/s,计算冷库中人员的疏散时间.根据火灾蔓延与人员疏散研究结果,论证了在先进的消防技术和有效的消防管理条件下,增大冷藏间占地面积和防火分区面积的可行性.提出了对于大型冷库的消防技术和管理方面的建议.     

Thermal storage and nonlinear heat-transfer characteristics of PCM wallboard

For the materials with constant thermophysical properties, the thermal performance of wallboards (or floor, ceiling) can be described by decrement factor f and time lag φ. However, the phase change material (PCM) may charge large heat during the melting process and discharge large heat during the freezing process, which takes place at some certain temperature or a narrow temperature range. The behavior deviates a lot from the material with constant thermal physical properties. Therefore, it is not reasonable to analyze the thermal performance of PCM wallboard by using the decrement factor f and time lag φ. How to simply and effectively analyze the thermal performance of a PCM wallboard is an important problem. In order to analyze and evaluate the energy-efficient effects of the PCM wallboard and floor, two new parameters, i.e., modifying factor of the inner surface heat flux ‘α’ and ratio of the thermal storage ‘b’, are put forward. They can describe the thermal performance of PCM external and internal walls, respectively. The analysis and simulation methods are both applied to investigate the effects of different PCM thermophysical properties (heat of fusion H_m, melting temperature T_m and thermal conductivity k) on the thermal performance of PCM wallboard for the residential buildings. The results show that the PCM external wall can save more energy by increasing H_m, decreasing k and selecting proper T_m (α < 1); that the PCM internal wall can save more energy by increasing H_m and selecting appropriate T_m, k. The most energy-efficient approach of applying PCM in a solar house is to apply it in its internal wall.     

夜间通风相变贮能堆积床系统降温效果实验研究

提出了夜间通风相变贮能堆积床系统的概念，介绍了在北京搭建的系统实验装置，分析了系统的实测降温效果，与普通的夜间通风降温方法作的比较表明，该系统降温效果显著。     

Experimental and modelling study of twin cells with latent heat storage walls

An experimental and numerical simulation study of the application of phase change materials (PCMs) in building components is presented for thermal management of a passive solar test-room. The experimental study was conducted in an outdoor test cell constituted of two small rooms separated with a wall containing PCM. A specific wall made of hollow glass bricks filled with PCM was studied. Three PCMs were tested: fatty acid, paraffin, and salt hydrate whose melting temperatures are 21 °C, 25 °C and 27.5 °C respectively.Indoor and outdoor temperatures were measured with thermocouples. Ten fluxmeters located at the centre of each wall allowed us to measure the heat fluxes across the walls. Tests were carried out in real climatic conditions.A one-dimensional numerical model has been developed to simulate the transient heat transfer process in the walls. Reasonable agreement between the simulation and the experimental results was observed.     

Experimental investigation of dehumidification process in cooling coil by utilizing air-to-air heat exchanger in humid climate of Iran

Energy recovery systems can be used in HVAC to reduce energy consumption by recovering wasted energy from the exhausted air to pre-cool inlet fresh air. In this paper, experimental study of utilizing cooling coil (CC) and cooling coil combined with heat exchanger (CCHE) has been developed. Considering the different climate zones in Iran, the experimental study has been done for the areas with high humidity content. In each case, the effects of air-to-air heat exchanger (HE) on the sensible and latent cooling load are investigated. The analysis gives the applicability of HE in Iran for various operational conditions to obtain air with lower moisture content. In CCHE systems more latent load quota is allocated in cooling coils and lower air humidity ratio can be obtained. Also in the cities with higher dew point depression (difference between dry-bulb and dew point temperature) more humidity reduction is achieved and the difference between latent load quotas of CCHE system is higher than CC system.     

高温相变共晶盐潜热蓄冷介质的配制与测试

配备了一种高相变温度蓄冷介质并进行了性能测试,该介质的熔点为１０ ．０ ～１０ ．５℃,固—液相变潜热为１２８ ．６ ｋＪ／ｋｇ（１８５ ．２ ｋＪ／ｄｍ３） ,主要成分为Ｎａ２ＳＯ４·１０Ｈ２ Ｏ,ＮＨ４Ｃｌ,硅胶及ＳｉＯ２ ,其特点是原料来源丰富,潜热和显热蓄冷量较大,是一种有发展前途的蓄冷介质     

Impacts of some building passive design parameters on heating demand for a cold region

In this study, the impact of passive design parameters such as building shape and orientation position on heating demand has been theoretically investigated. Therefore, a transient heat transfer problem in the building envelope with insulation and without insulation is solved by using the finite difference method. The considered buildings are placed on the ground with the azimuth angles from 0^°$0^{°}$ to 90^°${90}^{°}$. The heat loss per unit area of the buildings is computed by hour–hour and the yearly energy consumption of the buildings is also determined in the simulation model. The climatic data of Elazigˇ (38.4^°N)$(38.4^{°}\mathrm{N})$, a city located in a cold region of Turkey, are considered for the analysis. It is shown that buildings with a square shape have more advantages, and the most suitable orientation angles are 0^°$0^{°}$ and 80^°${80}^{°}$ for buildings having shape factors (the ratio of building length to building depth ) 2/1 and 1/2, respectively.     

Experimental investigation of wallboard containing phase change material: Data for validation of numerical modeling

In construction, the use of phase change materials (PCM) allows the storage/release of energy from the solar radiation and/or internal loads. The application of such materials for light weight construction (e.g. a wood house) makes it possible to improve thermal comfort in summer and reduce heating energy consumption in winter. The choice of a PCM depends deeply on the building structure, on the weather and on building use: numerical modeling is indispensable. In this paper, an experimental comparative study is described, using cubical test cells with and without PCM composite. A set of experimental data is detailed, concerning the air and wall temperatures. The results are compared with a numerical modeling and show that hysteresis must be taken into account to predict correctly the heat transfer.     

An experimental investigation of distortional buckling of steel storage rack columns

An experimental investigation on the behavior of steel storage rack columns subjected to compression is presented. Members of different lengths are tested, but special attention is focused on the behavior of the specimens having lengths that make them subject to distortional buckling. This mode of buckling can be observed in moderately long specimens; namely, longer than the stub columns used for the determination of the local buckling strength, but short enough to avoid the effects of global buckling. The deformation experienced by these specimens is measured, and it is observed that there is a range of member lengths where the failure mode is a combination of distortional buckling and global buckling modes. Furthermore, it is verified that, although the effect of the interaction between these modes on the member strength is not large, the accuracy of the current design procedures improves if it is considered in the calculations.     

Numerical and experimental study on heat pump water heater with PCM for thermal storage

An air source heat pump water heater with phase change material (PCM) for thermal storage was designed to take advantage of off-peak electrical energy. The heat transfer model of PCM was based upon a pure conduction formulation. Quasi-steady state method was used to calculate the temperature distribution and phase front location of PCM during thermal storage process. Temperature and thermal resistance iteration approach has been developed for the analysis of temperature variation of heat transfer fluid (HTF) and phase front location of PCM during thermal release process. To test the physical validity of the calculational results, experimental studies about storing heat and releasing heat of PCM were carried. Comparison between the calculational results and the experimental data shows good agreement. Graphical results including system pressure and input power of heat pump, time-wise variation of stored and released thermal energy of PCM were presented and discussed.     

冰蓄冷技术在某商务中心应用的经济性分析

本文主要结合福州市某商务中心项目的冷热源方案,着重通过初投资、运行费用、回收年限方面对冰蓄冷与常规电制冷两种空调系统进行技术及经济性的比较、分析,探讨冰蓄冷空调系统在夏热冬暖地区应用的可行性及经济性。     

蒸压灰渣页岩砖砌体抗压及抗剪性能试验研究

通过对3种砂浆砌筑的24件蒸压灰渣页岩砖砌体试件的轴心抗压试验与通缝抗剪试验,分别对该砌体在轴心压力与剪力作用下的抗压性能与抗剪性能进行试验研究,分析了该砌体的破坏特征、抗压能力与抗剪性能。研究表明：轴压试验中,与黏土砖相比蒸压灰渣页岩砖砌体的初始裂缝出现较早,砌体的抗压强度随着砂浆强度的提高而提高。砌体通缝抗剪试验试...