被动式太阳房的降温研究

通风的目的是保证室内良好的空气品质,采用自然通风方式是生态建筑设计的重要内容,自然通风形成的室内热环境有利于人体舒适性.太阳能烟囱管能强化房间的自然通风,可以有效地改善室内的空气品质和室内热环境,但尚未达到舒适的温度.     

采用散热器和低温地板辐射供暖的室内热环境与能耗研究

建立了供暖房间室内空气自然对流二维空气湍流流动与传热数学模型，利用PHOE—NICS3．3计算软件对低温地板辐射供暖房间和散热器供暖房间的温度场进行了仿真模拟。建立了供暖房间热过程数学模型，对两种房间进行了编程计算。两个模型计算结果反映了低温地板辐射供暖房间的室内热环境优于散热器供暖房间。根据各自热环境特点，计算了两种房间的能耗。发现低温地板辐射供暖房间比散热器供暖房间节能109／6～129／6，其节能的主要原因是消除了空气局部高温区，避免了外围护上的附加传热量。     

基于动态热负荷的太阳能——地源热泵运行模式研究

建立了太阳能-地源热泵系统一体化模型,以大连地区气候条件为基础,计算了供暖季某天内房间热负荷的逐时值.在动态热负荷基础上,对联合供暖系统在不同串联运行模式和并联运行模式不同分流比的运行工况进行了模拟计算,将模拟结果与实脸数据对比,两者吻合较好.结果表明:房间热负荷的变化可影响热泵机组COP.联合运行模式在地温的恢复和系...     

严寒地区某公寓自然通风效果模拟分析

应用自然通风可以在实现建筑节能的同时提高室内空气品质。以某典型公寓建筑作为研究对象,用Dest对其自然通风进行模拟,分析严寒地区建筑的自然通风节能潜力,得出严寒地区自然通风潜力较大时间段,计算出自然通风有效性。并用Dest分别计算出过渡季节开窗与不开窗条件下的耗冷量,得出自然通风节能率。为了验证上述结论,用Airpak对典型时间、典型房间室内温度场、风速场、PMV分布进行模拟。     

局部大余热地下空间的空调节能策略研究

针对含有局部大余热地下空间的空调特点,建立了带有局部冷却处理的大余热空间空调系统的运行能耗模型,并给出了相应的空调运行管理策略。该策略通过优化房间风冷和水冷负荷分配,求解出房间的最佳送风状态,在满足空调房间环境要求的前提下,实现系统的节能运行。     

室内空气对流的特征与数值模拟

采用雷诺平均的Navier-Stokes方程和K-ε湍流模型,数值模拟了在温度梯度和浓度梯度作用下的房间空气对流结构。通过改变浮升力比Grc/GrT及自然对流与强迫对流强度比Gr/Re^2值的大小,分析了浓度浮升力方向及其大小和Gr/Re^2值对空气流态的影响。结果表明,当Grc/GrT改变时,热和污染源壁面附近的流体流动状态和热边界层厚度发生了改变;随着Gr/Re^2的增大,室内空气流型由机械通风主导逐步变化到自然通风主导。     

自然通风房间内油池面积变化对细水雾灭火效果影响的数值模拟

采用大涡模拟、混合物分数模拟和欧拉一拉格朗日粒子运动描述法研究了不同油池面积条件下自然通风房间内细水雾与油池火焰作用过程，分析了加入水雾对着火房间速度场和温度场的影响，推导出油池火焰根部空气卷吸速率与油池尺寸的关系，探讨了细水雾在火羽流的不同区域内的灭火机理。模拟结果表明：加入水雾不仅降低了着火房间热烟气层温度，而且显著影响了房间内速度场，在间歇火焰区和浮力羽流区以及热烟气层主要发挥细水雾的蒸发冷却作用，在恒定火焰区则是蒸发冷却和隔氧窒息共同作用，油池火根部的空气卷吸速率与油池边长的四次方成正比。     

城市住宅小区建筑室内外环境对局部气候的影响

以天津某高层住宅小区为对象,建立了小区建筑和室内户型的计算分析模型。基于CFD方法,开展了在冬、夏季典型气候下的室外风气候特性、室内自然通风情况的模拟分析研究。得到了住宅小区室外风速、风压的分布场、室内三维速度场、温度场分布场。探讨了风向、风速、窗户对局部气候的影响。研究表明对室外风环境,由于小区建筑的分布特征,存在着局部增强的强风区,最大速比达到1.8;就室内气候而言,具有自然对流效果的A型房间的自然通风效果要优于B型房间。通过对既有城市住宅小区的室内外气候环境的模拟分析,可以为建筑气候的设计提供重要的参考价值。     

一种具有强化自然通风效果的太阳能空调房

提出一种依靠吸附制冷原理制冷，结合太阳能通风筒强化自然通风的太阳能空调房，其特点在于一方面可充分利用太阳能吸附集热器和太阳能通风筒集热面有效降低房间的太阳热负荷；另一方面利用吸附床吸附制冷过程释放大量吸附热的现象，用于强化夜间自然通风。该文针对房间的通风率、进风温度变化等进行了分析，结果表明，典型条件下，采用2．5m^2的太阳能通风筒集热面、5m^2的吸附制冷系统集热面，一间20m^2的太阳房日间通风率可达100kg／h，夜间通风率则可进一步提高30％～40％。和其它空词装置相结合，该太阳房可用作独立式住宅，粮仓等，对于创造健康的居住环境和经济节能型仓储系统都有重要意义。     

基于热舒适观点的房间热性能评价

介绍了通过计算不舒适指标评价房间热性能的方法。基于人体热反应从热舒适角度来评价房间的热性能 ,得出人体热舒适对房间建筑参数的敏感程度。这些参数主要包括围护结构的物理性质 ,房间的位置、朝向及几何形状     

Energy saving by integrated control of natural ventilation and HVAC systems using model guide for comparison

Integrated control by controlling both natural ventilation and HVAC systems based on human thermal comfort requirement can result in significant energy savings. The concept of this paper differs from conventional methods of energy saving in HVAC systems by integrating the control of both these HVAC systems and the available natural ventilation that is based on the temperature difference between the indoor and the outdoor air. This difference affects the rate of change of indoor air enthalpy or indoor air potential energy storage. However, this is not efficient enough as there are other factors affecting the rate of change of indoor air enthalpy that should be considered to achieve maximum energy saving. One way of improvement can be through the use of model guide for comparison (MGFC) that uses physical-empirical hybrid modelling to predict the rate of change of indoor air potential energy storage considering building fabric and its fixture. Three methods (normal, conventional and proposed) are tested on an identical residential building model using predicted mean vote (PMV) sensor as a criterion test for thermal comfort standard. The results indicate that the proposed method achieved significant energy savings compared with the other methods while still achieving thermal comfort.     

Performance evaluation of indirect evaporative cooling using whole-building hygrothermal simulations

In an indirect evaporative cooling (IEC) installation the return air is cooled by adiabatic humidification. In an air/air heat exchanger this air cools down the supply air. This paper presents a simulation methodology focusing on the interaction between the thermal performance of an IEC system and the heat and moisture balance of the building where it is applied. The thermal effectiveness of an IEC system is first studied by measurements. It was found that the effectiveness is independent of the air inlet conditions. In the second part the influence of the ventilation rate, the indoor moisture production and the moisture buffering capacity on the thermal performance were evaluated using dynamic calculations with the multizone building simulation program TRNSYS. Increasing the indoor moisture production and lowering the ventilation rate both reduce the thermal performance of the system. Hygroscopic materials may ameliorate the applicability of IEC.     

Nonlinear coupling between thermal mass and natural ventilation in buildings

An ideal naturally ventilated building model that allows a theoretical study of the effect of thermal mass associating with the non-linear coupling between the airflow rate and the indoor air temperature is proposed. When the ventilation rate is constant, both the phase shift and fluctuation of the indoor temperature are determined by the time constant of the system and the dimensionless convective heat transfer number. When the ventilation rate is a function of indoor and outdoor air temperature difference, the thermal mass number and the convective heat transfer air change parameter are suggested. The new thermal mass number measures the capacity of heat storage, rather than the amount of thermal mass. The analyses and numerical results show that the non-linearity of the system does neither change the periodic behaviour of the system, nor the behaviour of phase shift of the indoor air temperature when a periodic outdoor air temperature profile is considered. The maximum indoor air temperature phase shift induced by the direct outdoor air supply without control is 6 h.     

A ventilated courtyard as a passive cooling strategy in the warm humid tropics

The paper investigates the potential of a courtyard for passive cooling in a single storey high mass building in a warm humid climate. The inclusion of an internal courtyard in building design is attributed to the optimization of natural ventilation in order to minimize indoor overheating conditions. However, the efficiency of this strategy greatly depends on the design details of the building composition in providing appropriate airflow pattern to the courtyard. From the results of thermal measurements, a significant correlation between wall surface temperatures and indoor air temperatures is evident. A reduction of indoor air temperature below the levels of ambient is seen as a function of heat exchange between the indoor air and high thermal mass of the building fabric. However, this behavior is affected by indoor airflow patterns, which are controlled through the composition between envelope openings and the courtyard of the building.From a computational analysis, several airflow patterns are identified. A relatively better indoor thermal modification is seen when the courtyard acts as an air funnel discharging indoor air into the sky, than the courtyard acts as a suction zone inducing air from its sky opening. The earlier pattern is promoted when the courtyard is ventilated through openings found in the building envelope. The computational simulation utilizing the standard k-ε turbulent model with isothermal condition agrees closely with the measurements taken from the field investigation.     

Application of ANN to explore the potential use of natural ventilation in buildings in Turkey

Indoor natural ventilation provides both the circulation of clear air and the decrease of indoor temperature, especially, during hot summer days. In addition to openings, building dimensions and position play a significant role to obtain a uniform indoor air velocity distribution. In this study, the potential use of natural ventilation as a passive cooling system in new building designs in Kayseri, a midsize city in Turkey, was investigated. First, indoor air velocity distributions with respect to changing wind direction, magnitude and door openings were simulated by the FLUENT package program, which employs finite element methods. Using the simulated data an artificial neural network (ANN) model was developed to predict indoor average and maximum air velocities. The simulations produced by FLUENT show that the average indoor air velocity is generally below 1.0 m/s for the local prevailing wind directions. The simulations results suggest that, in addition to the orientation of buildings in accordance with prevailing wind directions, a proper indoor design of buildings in the area can significantly increase the capability of air ventilation during warm summer days. It was found that a high correlation exists between the simulated and the ANN predicted data indicating a successful learning by the proposed ANN model. Overall, the evaluation of the network results indicated that the ANN approach can be utilized as an efficient tool for learning, training and predicting indoor air velocity distributions for natural ventilation.     

Natural ventilation in Beirut residential buildings for extended comfort hours

This paper examines the effectiveness of natural ventilation in Beirut for the purpose of extending comfort periods within living and sleeping zones of the residential buildings. A field survey is conducted to estimate the common window opening and degree profiles. A base case model representing a typical residential apartment located in Beirut was then adopted in integrated environmental solutions (IES) software and calibrated by experimentation through monitoring simulated and measured data indoor. The calibrated IES model was used to evaluate typical wall layering and building local materials and their role in improving indoor comfort with natural ventilation. The simulation results showed that an optimal wall configuration of higher insulation and capacitance, comprised of a 5?cm layer of strawboard sandwiched between a 2?cm?×?10?cm wall of masonry Hempcrete units, achieved the highest degree of thermal comfort and enhanced comfort in winter season when compared to the base case.     

Impact of passive cooling techniques on energy demand for residential buildings in a Mediterranean climate

This study presents the thermal analysis of a building prototype, which was designed and built in accordance with energy efficiency measures to improve indoor thermal comfort, particularly in summer. The building prototype is located in Souidania (20 km southwest of Algiers, latitude 36°7N, Longitude 03°2E). The location is characterized by a temperate Mediterranean climate. In order to perform this analysis, various activities are carried out: a series of monitoring campaigns; dynamic simulations with TRNSYS software, calibration of the model with experimental data and comparative study with buildings that use different wall constructions. Based on a validated building thermal model, dynamic analysis is carried out in order to evaluate the impact of thermal mass and of eaves and night ventilation. The results demonstrate that cooling energy demand is more affected by thermal transmittance values than by the envelope thermal mass. A recommended guideline for the optimum overhang length for south-facing windows is proposed. Ultimately, it is found that the combination of both natural ventilation and horizontal shading devices improves thermal comfort for occupants and significantly reduces cooling energy demand.     

Design and simulation of a new energy conscious system, (ventilation and thermal performance simulation)

This paper presents the results of simulating the ventilation and thermal performance of a new passive cooling and heating system. The new system was integrated into the roof of a typical contemporary North African house, which was modelled and mounted inside a wind tunnel, for natural ventilation simulation. Thermal performance of the new system was simulated using a new computer programme (BTS), developed by the author. Results are presented in terms of indoor temperature and CATD and HATD, which are newly introduced concepts in defining the building cooling and heating loads.     

INTEGRATED PREDICTIVE ADAPTIVE CONTROL OF HEATING,COOLING, VENTILATION,DAYLIGHTING AND ELECTRICAL LIGHTING IN BUILDINGS

The present energy consumption of European Buildings is higher than necessary, given the developments in control engineering. Optimization and integration of smart control into building systems can save substantial quantities of energy on a European scale while improving the standards for indoor comfort. Many tools are available for the simulation of one or some of the following aspects: (a) heating, cooling and indoor thermal comfort, (b) ventilation and indoor air quality, (c) daylighting, electrical lighting and light quality, (d) installations, local control and fault detection, (e) Genetic optimized Neuro-Fuzzy control. The interaction between these aspects, however, is very relevant and cannot be neglected. Therefore, an integrated software tool is required. TNO together with the University of Delft develops such an integrated tool. This paper describes the first results of the utilization of this tool and the development of an integrated, predictive, adaptive building system for indoor climate control.