冷空气幕加侧送方式影响室内热环境的数值模拟——一种新型室内送风方式探索

通过对受热墙体上增设冷空气幕和传统侧送的送风方式进行数值模拟研究,对比分析传统的侧送与受热墙体侧冷空气幕+侧送两种空调方式。探讨靠近受热墙体的冷空气幕对整体房间气流组织、人体舒适度和能量利用系数的影响规律。在特定的环境下(存在传热量较大窗墙的房间),冷空气幕+侧送的方式与传统侧送相比,模拟房间的整体风速较低,房间整体温度分布与置换通风相近,即房间截面的温度随着高度逐渐增加。在送风量相同的条件下,冷空气幕+侧送方式的能量利用系数、预测平均投票(predicted mean vote,PMV)及预测不满意百分率(predicted percent dissatisfied,PPD)值均优于传统侧送方式。     

空调房间空气流场分布的数值模拟

本文根据《采暖通风与空气调节设计规范》建立了空调房间的物理模型,确定了模型的相关热工参数.针对影响室内气流分布的诸多因素,选择性地分析了送回风口位置对室内气流分布的影响.本文采用CFD软件Airpak模拟了空调房间同侧上送下回、对侧上送下回、同侧下送上回、对侧下送上回四种典型送回风方式,得出室内温度场、速度场、空气龄和人体热舒适性等参数分布图,并根据ISO7730标准分析了四种送回风方式下的室内空气环境.经综合分析,同侧上送下回的送风方式为最佳气流组织方案.本研究对空调房间气流组织设计具有理论指导意义和实用价值.     

全空气定风量空调系统变频变风量运行控制与仿真研究

分析了全空气定风量空调系统空调房间的特性,推导出变风量送风方式下空调房间的数学模型,构造PID控制器、模糊控制器和神经网络控制器三种控制器,并利用Matlab软件中的Simulink工具箱对三种控制器的性能进行比较。     

高大空间空调气流组织优化研究与应用

分析制丝车间原有的空调气流组织的不足,将两套侧墙边的上送风空调改造为下送风空调,保留车间中央的1套作为备用.结合车间屋顶通风器进行排气.改造后,车间环境舒适度、节能均有显著提高.     

某下送风多功能厅气流组织及节能性的实测与分析

实测了采用下送风空调方式的某多功能厅的温度场和速度场。获得了夏季三种工况下的温度、速度分布及其随时间的变化。评价了该空调房间的节能性以及舒适状况。结果表明,在一定送风量和送风参数下能够满足舒适性要求,且具有较明显的节能效果,通风效率为1.7~3.2。     

关于天津某高校夏季中央空调人体热舒适度的研究

高校是教学和科研的重要场所,热舒适度的高低会直接影响到工作和学习的状态及效率。通过对天津地区某高校GHP燃气空调的热舒适度进行分析,当空调设定温度为26℃时,利用PMV热舒适度计算方法计算出不同房间的热舒适度值都处于较舒适区域。另外,运用调查问卷的方式对高校师生进行了实际热舒适度的调查与分析,调查问卷结果与理论计算结果一致。结合理论计算结果与调查问卷结果,对不同的房间进行了个性化温度设置,通过对比运行数据,发现恰当的设置空调温度在提高师生热舒适度的同时还能节约能源。     

高大铁路旅客候车室空调送风方式的选择

结合深圳北站空调系统的设计情况,从节能、舒适性出发,介绍高大空间的旅客候车室其空调送风方式的特点及适宜送风方案:旅客进出站通廊区域采用条形风口侧送风方式;大面积候车区域采用高位球形喷口送风方式;商业岛采用低位置换式孔板送风方式。     

隔断式工位空调系统气流组织与人体热舒适评价

采用K-ε湍流模型对采用隔断式工位空调的典型办公室工作微环境进行数值模拟,分析工位空调在人体周围所形成的非均一环境参数场,并进一步研究非均匀环境对人体热舒适的影响.在不同工位送风参数下对房间和人体周围环境参数的分布状况及吹风感和热舒适性进行研究.模拟结果发现:工位空调送风可以使室内温度呈现分区分布,工位送风效率高,可以...     

热风送风温差对室内环境的影响

为了降低空调系统的能耗,本文以某一典型的空调办公室为研究对象,,采用数值计算软件Fluent模拟冬季室内气流组织的分布状况,对比分析了在相同的热负荷时不同的送风速度和送风温差对室内环境的影响,确定了在既定的热负荷时,在满足规范规定的送风温差的前提下,大温差送风可以提高人体活动区的温度,降低人体活动区的风速,为其他相同或类似房间空调系统的选择和气流组织设计提供参考。     

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。     

Thermal comfort standards for air conditioned buildings in hot and humid Thailand considering additional factors of acclimatization and education level

This paper presents the result of a large thermal comfort survey conducted using 1520 Thai volunteers from different climatic regions of Thailand. The survey was conducted using different types of air-conditioned buildings from the private and public sectors.Apart from common thermal comfort factors such as air dry bulb temperature, relative humidity and air velocity, two non-quantifiable factors were considered. These are the acclimatization to the use of air conditioner at home and the education level, i.e., post graduate, graduate and scholar. A general database for thermal comfort studies in Thailand was created, and different thermal comfort standards were developed for the three climatic regions of Thailand. Twenty six degree Celsius and 50–60% relative humidity could be used as a comfortable environment condition for the whole country. The data was then used to generalize an earlier concept we developed for setting thermal comfort standard using data from non air-conditioned buildings.     

基于热舒适的空调列车车厢风速设计参数优化

以Fanger热舒适方程及PMV,PPD评价指标为理论依据,模拟计算了夏季空调列车热环境,在满足乘车人员热舒适情况下,提出了较为合理的风速值,分析了风速和相对湿度对空调列车热舒适和能耗的影响。联系热舒适方程,通过优化参数可以减少空调列车能耗和解决列车超员问题。     

Thermal comfort in Japanese schools

Comfort standards (ASHRAE 55, ISO 7730) specify exact physical criteria for producing acceptable thermal environments, which include temperature, air movement, and humidity limits that are often difficult to comply with, particularly in the subtropical climate of Japan. Changing expectations of comfort are important in evaluating comfort since schools in Japan are not typically air-conditioned. With the rapid growth of school buildings in the US and all over the world, provisions for comfort are critical to student performance and occupant well-being. Are these temperate-climate, air-conditioning based standards applicable in these locations? This paper builds upon previous thermal comfort work that has focused primarily on office environments. For this project we adapt traditional methods of data collection and inquiry for use in the school environment. During the late summer 2000, we conducted surveys in naturally ventilated and air-conditioned schools, polling responses from 74 students, while simultaneously measuring indoor climate variables. Air-conditioned classrooms had conditions within the comfort zone, causing occupants to report ‘slightly cool’ thermal sensations. The naturally ventilated classrooms were 3 °C warmer than the air-conditioned classrooms and occupants voted that conditions were also within the central three categories (surrounding neutral) of the ASHRAE thermal sensation scale—therefore equated with comfort. These ‘neutral’ sensations, however, do not correlate to people’s preferred thermal state. Comfort responses are discussed in terms of comparisons to ASHRAE Standard 55-92 Thermal Conditions for Human Occupancy.     

Efficiency assessment of indoor environmental policy for air-conditioned offices in Hong Kong

To reduce carbon dioxide (CO₂) emissions through thermal energy conservation, air-conditioned offices in the subtropics are recommended to operate within specified ranges of indoor temperature, relative humidity and air velocity. As thermal discomfort leads to productivity loss, some indoor environmental policies for air-conditioned offices in Hong Kong are investigated in this study with relation to thermal energy consumption, CO₂ emissions from electricity use, and productivity loss due to thermal discomfort. Occupant thermal response is specifically considered as an adaptive factor in evaluating the energy consumption and productivity loss. The energy efficiency of an office is determined by the productivity which corresponds to the CO₂ generated. The results found that a policy with little impact on occupant thermal comfort and worker productivity would improve the office efficiency while the one with excessive energy consumption reduction would result in a substantial productivity loss. This study is a useful reference source for evaluating an indoor thermal environmental policy regarding the energy consumption, CO₂ emissions reduction, thermal comfort and productivity loss in air-conditioned offices in subtropical areas.     

Thermal comfort enhancement by using a ceiling fan

A parametric analysis on the effect of using a ceiling fan in an air-conditioned room is performed by two-dimensional (2D) numerical simulation of steady state airflow and heat transfer. Thermal comfort analysis is done for a person standing in a room with an inlet and an outlet for air conditioning and a ceiling fan. Representative three-dimensional (3D) simulation is also performed for the comparison of results obtained by using 2D and 3D models. Distributions of velocity, temperature, and relative humidity are presented. Different cases in which the ceilings fan may be not in use or in use with different air speed normal to the plane of fan blades due to different rotational speeds are considered. Predicted mean vote is computed and used to assess the thermal comfort characteristics. It is found that as the normal air speed from the fan increases, thermal comfort significantly shifts toward the cooler scale to allow higher supply air temperature or higher heat load in the room while maintaining the same comfort level.     

Temperature distributions in air-conditioned rooms

This paper contributes to a better understanding of the parameters which influence the thermal comfort achievable in an air-conditioned room. First, simplified relationships were established to enable a study to be made of the temperature distribution using reduced scale models. A prototype and a 0·3 scale model were constructed. An experimental technique for measuring the air temperature at various points in the two rooms was then established. Experiments to test the validity of the similarity criteria were next carried out.A study was then made, for various supply conditions, of the temperature distribution in a room heated by blown hot air. In this way it was shown that the Archimedes number could be considered a characteristic number for the room air supply. The limit values required for good thermal comfort in a given room were established in this way.The differing results obtained should facilitate temperature distribution forecasting in air-conditioned rooms.     

Earth-to-air heat exchangers for Italian climates

The European Energy Efficiency Building Directive 2002/91/CE, as well as other acts and funding programs, strongly promotes the adoption of passive strategies for buildings, in order to achieve indoor thermal comfort conditions above all in summer, so reducing or avoiding the use of air conditioning systems.In this paper, the energy performances achievable using an earth-to-air heat exchanger for an air-conditioned building have been evaluated for both winter and summer. By means of dynamic building energy performance simulation codes, the energy requirements of the systems have been analysed for different Italian climates, as a function of the main boundary conditions (such as the typology of soil, tube material, tube length and depth, velocity of the air crossing the tube, ventilation airflow rates, control modes). The earth-to-air heat exchanger has shown the highest efficiency for cold climates both in winter and summer.The possible coupling of this technology with other passive strategies has been also examined. Then, a technical-economic analysis has been carried out: this technology is economically acceptable (simple payback of 5–9 years) only in the cases of easy and cheap moving earth works; moreover, metallic tubes are not suitable.Finally, considering in summer a not fully air-conditioned building, only provided with diurnal ventilation coupled to an earth-to-air heat exchanger plus night-time ventilation, the possible indoor thermal comfort conditions have been evaluated.     

大空间两种气流组织夏季热环境及其能耗实验研究

以某大空间实验基地为研究对象,针对喷口送风和柱状下送风两种分层空调的热环境及供冷量进行了实测研究.研究结果表明:因喷口送风空调区较大,在夏季室外气象参数基本相同的两种室外气象条件下,喷口送风空调系统供冷量比柱状下送风空调系统的供冷量分别高出20.8%、24.4%,且喷口送风空调系统抗干扰能力较柱状下送风强;喷口送风时工作区温度均匀性好于柱状下送风,头足温差较小,但其工作区风速超过标准,而柱状下送风时工作区风速则符合环境设计要求;两种不同送风量下喷口送风时吹风感指数分别为15.64%、11.23%,而柱状下送风时吹风感指数分别为4.17%、2.40%,柱状下送风要明显优于喷口送风.故从节能及热舒适性角度综合考虑,单侧回风的大空间建筑应尽可能采用柱状下送风分层空调,而对于干扰比较大,空调场地较小,无法布置柱状下送风口的场合,则选取喷口送风较好.     

Neural computing thermal comfort index for HVAC systems

The primary purpose of a heating, ventilating and air conditioning (HVAC) system within a building is to make occupants comfortable. Without real time determination of human thermal comfort, it is not feasible for the HVAC system to yield controlled conditions of the air for human comfort all the time. This paper presents a practical approach to determine human thermal comfort quantitatively via neural computing. The neural network model allows real time determination of the thermal comfort index, where it is not practical to compute the conventional predicted mean vote (PMV) index itself in real time. The feed forward neural network model is proposed as an explicit function of the relation of the PMV index to accessible variables, i.e. the air temperature, wet bulb temperature, globe temperature, air velocity, clothing insulation and human activity. An experiment in an air conditioned office room was done to demonstrate the effectiveness of the proposed methodology. The results show good agreement between the thermal comfort index calculated from the neural network model in real time and those calculated from the conventional PMV model.