Study on optimum design method for pleasant outdoor thermal environment using genetic algorithms (GA) and coupled simulation of convection,radiation and conduction

Extensive research has recently been conducted into improving outdoor thermal environments in summer. In this paper, (1) an optimum design method is developed with genetic algorithms (GAs) and coupled simulation of convection, radiation, and conduction for comfortable outdoor thermal environments, and (2) in order to examine the validity of the proposed optimum design system, an apartment block space in an urban area is set up as an analysis target and the optimum arrangement of buildings and trees in two cases are analyzed for pleasant outdoor thermal environment design. For the optimum arrangement of trees, two different cases within the target area are examined to clarify the effect of different target areas (all open space or walkways) on optimization. For the optimum arrangement of buildings, in order to clarify the effect of the different positions of apartment blocks and building coverage ratio, three cases with different positions or building shapes in the target domain are examined. As a result, the optimum arrangements of the buildings are derived using GA and simulations for the three cases, and the validity of the optimum design method is confirmed.     

Study on mitigation measures for outdoor thermal environment on present urban blocks in Tokyo using coupled simulation

The heat island phenomenon and degradation of the urban thermal environmental have become serious problems in Japan. In order to improve the outdoor thermal environment, it is necessary to understand quantitatively the effects of various measures. In this paper, the authors have performed coupled simulations of convection, radiation and conduction to evaluate the outdoor thermal environment over different urban blocks – ōtemachi as representative of a high-rise area and Kyobashi as a mid-rise area in Tokyo, Japan – to compare the effects of measures such as the heat release point and means of air-conditioning, greening, high surface albedo, and traffic volume. The results showed that the effectiveness of moderation countermeasures differed according to the configuration of the urban blocks.     

Numerical simulation of ground heat and water transfer for groundwater heat pump system based on real-scale experiment

The groundwater heat pump (GWHP) system is an open-loop system that draws water from a well or surface water, passes it through a heat exchanger and discharges the water into an injection well or nearby river. By utilizing the relatively stable temperature of groundwater, GWHP system can achieve a higher coefficient of performance and can save more energy than conventional air-source heat pump (ASHP) system. The performance of the system depends on the condition of groundwater, especially temperature and depth, which affect performance of the heat pump and system. For the optimization of design and operation of GWHP systems, it is necessary to develop a simulation tool which can predict groundwater and heat flow and evaluate system performance comprehensively. In this research, 3D numerical heat-water transfer simulation and experiments utilizing real-scale equipment has been conducted in order to develop the optimization method for GWHP systems. Simulation results were compared with the experimental results, and the validity of the simulation model was confirmed. Furthermore, several case studies for the optimal operation method have been conducted by calculating the coefficient of performance on various groundwater and well conditions.     

Energy saving in the conventional design of a Spanish house using thermal simulation

During the last decade, regulations designed to change the way of designing, building, maintaining, renovating and demolishing buildings and their surroundings have been developed at European level. However, sustainability targets shift throughout the life of a building and design solutions should go beyond strict compliance with each country's regulations. This study prioritises a building's energy behaviour during its use. It demonstrates the value of combining simple passive strategies with thermal simulation tools in standard architectural design practice. To achieve this, we started from the conventional design of a house in the North of Spain, applying passive techniques to achieve energy savings and environmental improvements that exceed regulatory requirements. Simple heating and cooling practices are incorporated into the design. The final house combines all favourable actions that manage to reduce consumption, especially during the most intense winter period. The final design is fully south facing, with an additional 20% glazing in the north and south façades, a 35-cm lintel in the window frames and an additional 2 cm insulation on the façade. Simulation reduced overall thermal consumption by almost 13%. The embodied energy used for the improvements is barely significant. Although the additional investment is arguably not profitable in economic terms, the increased investment is minimal in comparison with total investment in the building.     

双级循环高温热泵换热面积仿真优化设计方法

以COP为优化目标,以制热量、冷凝器和蒸发器(简称两器)水侧流速和压降、压缩机排气温度为约束条件,提出了双级循环离心压缩高温热泵系统换热器换热面积仿真优化设计方法。该方法包括两器总换热面积优化、两器面积比优化、回热器与两器面积配比优化3个过程。建立了双级循环高温热泵数值仿真设计系统,并进行了换热器换热面积优化设计。结果表明,换热器换热面积优化设计是解决热泵系统单一部件结构参数不匹配的有效途径;优化设计后,在保证热泵制热性能不变的前提下,两器总面积约降低了8.6%,蒸发换热管总管数减少了35.5%,优化效果显著。     

Thermal simulation software outputs: a framework to produce meaningful information for design decision-making

This paper describes a process used to develop and test a framework to produce thermal simulation post-processed information meaningful to building design decision-making. The framework adopts a user-centred approach in which the building designer is considered the ultimate simulation tool user either directly or indirectly when supported by consultants. The framework supports the building designer's ‘modus operandi’ and is developed through a set of interdisciplinary research methods. Participatory Action Research, Thematic Analysis and Grounded Theory are used, together with principles from Information Visualization, dynamic thermal modelling and Building Design, following a design approach to problem-solving taken from the discipline of Interaction Design. The various elements of the framework and their connections are derived from analysis of sequences of design actions made by novice designers undertaking complex design activities. Tests of the framework are undertaken through an online questionnaire and five semi-structured interviews with UK architectural design practices.     

Thermal simulation software outputs: a conceptual data model of information presentation for building design decision-making

Building simulation outputs are inherently complex and numerous. Extracting meaningful information from them requires knowledge which mainly resides only in the hands of experts. Initiatives to address this problem tend either to provide very constrained output data interfaces or leave it to the user to customize data organisation and query. This work proposes a conceptual data model from which meaningful dynamic thermal simulation information for building design decision-making may be constructed and presented to the user. It describes how the model was generated and can become operational, with examples of its applications to practical problems. The paper therefore contains useful information for software developers to help in specifying and designing simulation outputs which better respond to building designers’ needs.     

基于CFD建筑热环境模拟的建筑方案优化设计研究

考虑了影响建筑热环境的6个建筑设计要素:窗墙面积比、窗类型(传热系数)、水平遮阳板尺寸、外墙传热系数、屋顶传热系数及房间尺寸(长∶高∶宽)。根据设定的室内热环境评价指标:室内温度平均值、PMV平均值、温度不均匀系数和速度不均匀系数,通过正交试验和CFD模拟,得到了自然通风建筑设计中,使建筑热环境相对最优化的6个建筑设计要素的最优搭配方案。     

A design supporting simulation system for predicting and evaluating the cool microclimate creating effect of passive evaporative cooling walls

As a passive cooling strategy to control increased surface temperatures and create cooler urban environments, we have developed a passive evaporative cooling wall (PECW) constructed of pipe-shaped ceramics that possess a capillary force to absorb water up to a level higher than 130 cm. The current paper presents a simulation system to predict and evaluate microclimatic modifying effects of PECWs in urban locations where PECW installation is under consideration at the design stage. This simulation system is composed of a CFD simulation tool and a 3D-CAD-based thermal simulation tool. Simulation methodology of coupling the two simulation tools was developed and described in this paper. Numerical models for simulating surface temperatures and evaporation of PECWs were proposed based on analysis results of experimental data. Validation of the proposed numerical models was confirmed by comparing simulated results with measured data. In order to demonstrate the applicability of the proposed simulation system, a case study was then performed to predict and evaluate the microclimate in a rest station where PECWs were assumed to be installed. Spatial distributions of air temperature, airflow, moisture and surface temperature in the rest station were simulated under a sunny weather condition in the summer of Tokyo. Furthermore, thermal comfort indexes (mean radiant temperature and new standard effective temperature) were used to evaluate thermal comfort in the human activity spaces of the rest station. Simulation results show that this simulation system can provide quantitative predictions and evaluations of microclimatic modifying effects resulting from the application of PECWs.     

Thermal performance of a naturally ventilated building using a combined algorithm of probabilistic occupant behaviour and deterministic heat and mass balance models

This study explores the role of occupant behaviour in relation to natural ventilation and its effects on summer thermal performance of naturally ventilated buildings. We develop a behavioural algorithm (the Yun algorithm) representing probabilistic occupant behaviour and implement this within a dynamic energy simulation tool. A core of this algorithm is the use of Markov chain and Monte Carlo methods in order to integrate probabilistic window use models into dynamic energy simulation procedures. The comparison between predicted and monitored window use patterns shows good agreement. Performance of the Yun algorithm is demonstrated for active, medium and passive window users and a range of office constructions. Results indicate, for example, that in some cases, the temperature of an office occupied by the active window user in summer is up to 2.6 °C lower than that for the passive window user. A comparison is made with results from an alternative behavioural algorithm developed by Humphreys [H.B. Rijal, P. Tuohy, M.A. Humphreys, J.F. Nicol, A. Samuel, J. Clarke, Using results from field surveys to predict the effect of open windows on thermal comfort and energy use in buildings, Energy and Buildings 39 (7) (2007) 823-836.]. In general, the two algorithms lead to similar predictions, but the results suggest that the Yun algorithm better reflects the observed time of day effects on window use (i.e. the increased probability of action on arrival).     

Dynamic simulation based optimized design method of concrete production system for RCC dam

The construction system of roller compacted concrete (RCC) dam is running according to a series of connected procedures which are highly impacted and interacted consisting with the resource level. Therefore, a dynamic simulation model of the construction system for RCC dam is presented. With this model, the design of concrete production system is placed in the whole system and tested with related dynamic impactions and interactions under complicated boundaries. Moreover, if several simulation experiments were conducted, plenty of detailed information throughout the construction duration is obtained. Consequently, the optimal one should be chosen on the basis of actual requirement and situation.     

Minimisation of energy consumption of a bioclimatic building based on heat balance study and stand-alone PV system sizing using LLP

Bioclimatic buildings are very comfortable habitats for significant savings in the consumption of daily energy. They help to protect the environment by preventing the emission of dust and pollutant gases into the atmosphere. In this paper, a sizing method is proposed that ensures a suitable internal climate with adequate comfort. First, a simple algorithm is used for the estimation of the heat balance and performance of a typical bioclimatic house in the region of Laghouat, Algeria. Second, the load demand is assured using an optimal stand-alone photovoltaic system sizing method based on the loss of load probability method (LLP) while ensuring the minimum cost of the system. The results show the effectiveness of the proposed method that can be used to develop an optimal building sizing project in all its dimensions, in particular to reduce the overall budget of the operation.