办公建筑内地板送风和置换通风模式对室内环境质量影响的数值模拟对比研究

对地板送风和置换通风进行了理论分析和比较,利用数值计算分别对某办公室采用地板送风和置换通风进行了模拟,从PMV、PPD、通风效率等方面对模拟结果进行分析,最终得出结论：地板送风比置换通风具有更大的送风温差,且工作区的温度梯度较小,更具有舒适性和节能性,可以为工程设计和运行管理提供有益的参考。     

不同气流组织下夏季空调室内热舒适环境模拟

基于模型和Fanger提出的热舒适性PMV评价指标,对三种不同气流组织条件下夏季室内热舒适环境进行了数值模拟,模拟结果给出了室内的速度、温度及舒适度PMV指标分布情况。研究结论为改善室内热舒适环境,舒适性空调系统的设计及节能控制提供了参考依据。     

农村被动式住宅通风换气对室内热舒适性影响模拟分析

被动式建筑具有密闭性良好、减少能量损失的优势,在我国农村地区应用具有重要的节能意义。由于围护结构密闭性较高,被动式农村住宅通风换气技术对提高和保障室内空气品质和环境热舒适性尤为重要。针对沈阳某高校示范建筑,分析通风换气技术对其室内环境热舒适性影响,应用Airpak软件进行数值解算,给出室内温度场、速度场和PMV、PPD指标的分布状况。分析不同送风温度、送风风速工况条件下的室内空气温度分布情况,以及PMV、PPD指标对室内环境热舒适性的影响,确定满足环境热舒适性要求的送风工况,为农村被动式住宅的通风换气技术应用提供基础依据。     

地板送风气流组织特性的研究

采用数值模拟方法,对一应用地板送风系统的开敞式办公环境的气流组织进行模拟计算。通过对模拟结果的速度场和温度场的分析,表明了地板送风能够提供具有较好热舒适性的室内环境。     

地板送风空调房间数学建模及仿真

结合室内热力分层特性,将地板送风空调房间模型分为2个方面来建立:其一,以能量守恒原理为基础,建立了地板送风空调的黑箱模型,并利用阶跃响应实验确定了房间传递函数的各项参数;其二,在黑箱模型基础上考虑温度分层特性,结合房间的温度经验关系式,建立具有分层特性的地板送风空调房间数学模型。通过MATLAB Simulink进行控制建模及仿真,并利用仿真模型对实验的2种负荷工况进行仿真计算。仿真结果与实验结果吻合较好。     

KTV中央空调优化设计研究

应用Fluent对成都某KTV中央空调工程中包间1的室内气流组织进行数值模拟,并分析其速度场、温度场、PMV、PPD和空气龄,通过与传统KTV中央空调设计方案的对比,从节能、室内空气品质、热舒适度等方面指出本设计方案的合理性与经济性,从而为此类建筑的中央空调设计提供一定的参考依据。     

A new predictive thermal sensation index of human response

The purpose of this paper is to investigate the problem of determining a human thermal sensation index that can be used in feedback control of HVAC systems. We present a new approach based on fuzzy logic to estimate the thermal comfort level depending on the state of the following six variables: the air temperature, the mean radiant temperature, the relative humidity, the air velocity, the activity level of occupants and their clothing insulation. The new fuzzy thermal sensation index is calculated implicitly as the consequence of linguistic rules that describe human's comfort level as the result of the interaction of the environmental variables with the occupant's personal parameters. The fuzzy comfort model is deduced on the basis of learning Fanger's `Predicted Mean Vote' (PMV) equation. Unlike Fanger's PMV, the new fuzzy PMV calculation does not require an iterative solution and can be easily adjusted depending on the specific thermal sensation of users. These characteristics make it an attractive index for feedback control of HVAC systems. The simulation results show that the new fuzzy PMV is as accurate as Fanger's PMV.     

Evaluation of four control strategies for building VAV air-conditioning systems

It is necessary to adopt appropriate control strategies to save energy and improve the indoor air quality (IAQ). On the validated TRNSYS simulation platform, four different control strategies are investigated to examine the indoor air temperature, energy consumption, CO₂ concentration and predicted mean vote (PMV) for the variable air volume (VAV) systems in an office building in Shanghai. As an original scheme, Strategy A using constant outdoor air intake fraction shows high energy consumption, low CO₂ concentration and acceptable thermal comfort. By using minimum outdoor air ventilation based on dynamic occupancy detection, Strategy B can provide more than 15% energy saving, acceptable PMV value but high CO₂ concentration in breathing zone. By using indoor air temperature reset, Strategy C presents the most energy savings beyond 20% reduction, low CO₂ concentration but poor thermal comfort. In mild seasons, combining enthalpy-based outdoor airflow economizer cycle with supply air temperature reset, Strategy D can achieve 9.4% energy savings and the lowest CO₂ concentration. Taken together, each strategy covers some strengths as well as some weaknesses. How to comprehensively assess a control strategy for all specific objectives should be considered in future studies.     

Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate

The potential for improving occupants’ thermal comfort with personalized ventilation (PV) system combined with under-floor air distribution (UFAD) system was explored through human response study. The hypothesis was that cold draught at feet can be reduced when relatively warm air is supplied by UFAD system and uncomfortable sensation as “warm head” can be reduced by the PV system providing cool and fresh outdoor air at the facial level. A study with 30 human subjects was conducted in a Field Environmental Chamber. The chamber was served by two dedicated systems – a primary air handling unit (AHU) for 100% outdoor air that is supplied through the PV air terminal devices and a secondary AHU for 100% recirculated air that is supplied through UFAD outlets. Responses of the subjects to the PV-UFAD system were collected at various room air and PV air temperature combinations. The analyses of the results obtained reveal improved acceptability of perceived air quality and improved thermal sensation with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with ceiling supply diffuser. The local thermal sensation at the feet was also improved when warmer UFAD supply air temperature was adopted in the PV-UFAD system.     

车站高大空间空调系统气流组织与热舒适性分析

兼顾人体热舒适和建筑节能的要求,对目前车站高大空间空调气流组织的数值模拟研究报道进行对比分析。分析结果显示,人们对高大空间建筑室内热舒适要求高于居住建筑和办公建筑;从满足人体热舒适角度出发,空调送风加地板辐射供冷方案适于夏季满员工况,地板辐射供热加空调加湿方案适用于冬季满员工况;高大空间的空调系统适宜采用上送上回的送风方式,其温度场和速度场均优于上送下回的空调送风方式;在高大空间内设置分层空调系统将在一定程度上降低空调能耗,且分层空调中送风速度对分层界面的位置影响较大,送风温差对高大空间分层空调的温度分布和流场分布有较大影响。     

办公建筑中旋流风口地板送风系统的设计及实验研究

基于地板送风与置换通风原理的相似性,参考办公室中置换通风的设计方法,结合旋流风口地板送风系统的特性,提出旋流风口地板送风系统的设计方法。通过实验对设计方法进行了验证,并对室内热舒适性进行了评价。     

地板送风系统温度分层现象对能耗模拟程序的要求

地板送风系统的室内温度分层现象对准确预测系统能耗非常重要。目前,大部分用来计算能耗的程序都采用同一的室内温度假设。对天花板送风系统(即混合送风系统)而言,由于空调送风与室内气流混合充分,利用同一室内温度进行能耗分析是准确合理的。而对地板送风系统而言,特别是大空间,室内温度分层是该系统的本质特性,只有从根本上模拟温度分层特性,才能保证能耗分析软件的真实有效性。对地板送风系统采用同一室内温度进行能耗分析并不妥。因此,首先阐述了地板送风系统温度分层现象,分析了该系统的优点。其次,针对温度分层现象,介绍了地板送风系统能耗分析模型和负荷减小系数概念。最后,列举了国外几个常用的模拟程序,指出对地板送风系统,能耗模拟程序需注意或要解决的问题。     

Numerical simulation of the indoor environment

The CFD program VORTEX which has been developed for predicting the indoor environment in occupied spaces is described. The flow equations are the continuity equation, the Navier-Stokes equation, the thermal energy equation, the concentration equation and the equations for the kinetic energy of turbulence (k) and its dissipation rate () of the k- turbulence model. The equations are solved for the 3-D Cartesian system using the SIMPLE algorithm. The program produces a direct simulation of the thermal comfort indices PMV and PPD and the air quality of room air. Some applications involving mechanically ventilated (heating and cooling) and naturally ventilated rooms are presented. Results in the form of velocity vectors and contours for temperature, thermal comfort indices (PMV and PPD) and CO₂ concentration are produced for the cases investigated. Simulations using this program can provide design data as required by thermal comfort and indoor air quality standards and guides.     

Evaluation and comparison of thermal comfort of convective and radiant heating terminals in office buildings

Radiant heating systems are increasingly widely utilized in buildings for its energy conservation potential and enhanced thermal comfort. This paper presented an experiment to compare the thermal comfort performance of radiant heating system with convective heating system through objective measurement and subjective survey. Six physical parameters which might influence occupants' thermal satisfaction, including the Mean Radiant Temperature(MRT), humidity, air movement, A-weighted sound level,temperature fluctuation and vertical temperature difference, were measured. In addition, 97 subjects participated in the subjective survey part of this experiment, experiencing all the three environments heated by air source heat pump, radiator and floor heating.And they were asked to vote in six thermal comfort related aspects, i.e. thermal sensation, humidity, draught, local discomfort,overall thermal satisfaction and overall preferences, plus the acoustic environment, since the operation noise of heating system might lead to complains of the occupants. It was found that in continuous heating, no significant difference between radiant and convective heating system was observed in the Mean Radiant Temperature(MRT), indoor humidity and noise issue. Though radiant heating systems resulted in lower draught risk and less local discomfort complains in the feet region due to the less significant temperature fluctuations and vertical temperature gradients, radiant heating did not have significantly higher overall thermal satisfaction votes and was not significantly more preferred by occupants.     

Numerical procedure for predicting annual energy consumption of the under-floor air distribution system

As compared with the mixing system, indoor air temperature stratification in the under-floor air distribution (UFAD) system offers an opportunity for cooling load reduction in the occupied zone. This stratification is a major feature that offers the energy saving potential, but it has not been thoroughly taken into account in most energy simulation programs. In this article, a numerical procedure, based on coupling two types of modeling, i.e., CFD (computational fluid dynamic) simulation and dynamic cooling load simulation, is proposed to predict annual energy consumption. The dimensionless temperature coefficient is first defined in the UFAD system and obtained from CFD simulation, based on the boundary conditions from a cooling load program ACCURACY. According to this coefficient, temperature stratification input to ACCURACY is then revised to calculate the updated supply and exhaust air temperatures for final annual energy prediction. To demonstrate the method, a small office room is investigated using Hong Kong weather data. With the constant air volume (CAV) supply in the UFAD system, it is found that the dimensionless temperature coefficient is almost a constant, when the locations of heat sources are fixed. As compared with the mixing system, the UFAD system derives its energy saving potential from the following three factors: an extended free cooling time, a reduced ventilation load, and increased coefficients of performance (COP) for chillers.     

送风角度对空调列车室内热舒适性的影响

本文以YW25G型空调硬卧列车为研究对象,采用LVEL湍流模型,模拟不同送风角度下的列车内温度场、速度场、空气龄、CO2浓度及热舒适指标PMV、PPD的分布情况,通过比较得到最佳送风角度,为改善列车室内的热舒适性提供参考依据.     

地板送风房间内流场、温度场及负荷特性的研究

地板送风系统通过安装于架空地板上的旋流或格栅型散流器送风,架空地板下的静压箱是其区别于置换送风系统和全混送风系统的重要特征之一。本文采用数值模拟的方法对有、无静压箱工况下的下送风系统进行了对比研究,通过对室内流场和温度场的分析,考察了静压箱对室内热平衡的影响。其次,通过负荷有效系数计算了温度分层环境下的空调负荷,并给出了负荷有效系数的数值计算方法,可为今后地板送风系统的工程设计提供参考。     

地板送风静压箱送风均匀性研究

地板送风空调系统因其在热舒适、室内空气品质和节能性等方面的诸多优点,在我国逐渐得到研究和应用。本文采用CFD建立地板送风静压箱模型,模拟分析了静压箱地板送风系统静压箱高度、进风口位置及形状对静压箱送风均匀性的影响,可为工程设计提供参考。     

Predictive controllers for thermal comfort optimization and energy savings

The present work is focused on the study of indoor thermal comfort control problem in buildings equipped with HVAC (heating, ventilation and air conditioning) systems. The occupants’ thermal comfort sensation is addressed here by the well-known comfort index known as PMV (predicted mean vote) and by a comfort zone defined in a psychrometric chart. In this context, different strategies for the control algorithms are proposed by using an only-one-actuator system that can be associated to a cooling and/or heating system. The first set of strategies is related to the thermal comfort optimization and the second one includes energy consumption minimization, while maintaining the indoor thermal comfort criterion at an adequate level. The methods are based on the model predictive control scheme and simulation results are presented for two case studies. The results validate the proposed methodology in terms of both thermal comfort and energy savings.     

工位空调送风气流微环境评价

模拟了三种送风速度下送风气流在人体活动区形成的速度场、温度场及PMV的分布，结果表明人员活动区存在送风不均匀和温度分层现象，有助于解决吹风感；PMV值在 1和-1之间，可以满足人体热舒适要求。