Thermal Comfort Prediction Research Articles

Thermal comfort prediction of an underfloor air distribution system in a large indoor environment

The use of air distribution in HVAC has grown in popularity in buildings, and, to this end, the method chosen to deliver the conditioned air is strongly associated with increasing concerns about indoor environmental quality and its effect on occupants’ well-being. In the underfloor air distribution (UFAD) system, air is directly supplied to the base of the occupied zone, which causes temperature stratification from the lower to the upper layer of the zone. This flow pattern gives UFAD the advantage of using less energy while providing better thermal comfort than overhead air distribution (OHAD) system. This paper investigates the effectiveness of UFAD in a large space with a higher ceiling for various velocities of supply air and locations of diffusers at an identical air supply temperature. In particular, the goals of providing satisfactory comfort conditions for the occupants and its practical application to buildings have been examined. Computational fluid dynamics (CFD) software was used to simulate the thermal environment, along with the control variables for a huge theater space equipped with a UFAD system. Results show that the UFAD is capable of creating smaller vertical variations of air temperature and a more comfortable environment than conventional OHAD systems

Feasibility analysis of using humidex as an indoor thermal comfort predictor

HVAC energy savings have been a key focus of recent building energy management efforts, but the savings typically reduce thermal comfort for building occupants. Established thermal comfort models use complex and person-specific parameters, such as clothing insulation and metabolic rate, to predict individual comfort levels, making the design of automated comfort modelling systems a highly challenging endeavour. In this paper, we investigate the use of humidex, which encapsulates both temperature and humidity, as an easily measurable and highly representative indoor thermal comfort predictor. We verify the feasibility of humidex as an indoor thermal comfort predictor by contrasting its performance to that of the best feature set (the feature set that best predicts the thermal comfort) constructed jointly by recursive sequential forward selection and support vector regression. The analysis using the global datasets, including data from seven climate zones across three continents, shows that humidex is a favourable and easily measurable indoor thermal comfort descriptor when humidity is significant.We take away the message from the analysis and design, develop, and deploy a system that couples a deployment of sensor nodes in an office environment, where each node collects the ambient temperature and humidity at each person's desk, and an automated survey mechanism to record people's thermal sensation votes. We use subjective response through the surveys as ground truth to validate the performance of the thermal comfort prediction using humidex. The results confirm our analysis of global datasets and show that humidex is a good predictor of indoor thermal comfort at high humidity.

Effects of different cooling principles on thermal sensation and physiological responses

Applying low exergy cooling concepts in the built environment allows reduction of use of high quality energy sources. Non-uniform thermal conditions, which may occur due to application of lowex systems, can result in discomfort. Two different cooling principles were studied: passive (through convection in terms of increased air velocities) and active cooling (through convection or radiation). Furthermore, two different ventilation techniques were included: mixing and displacement ventilation. Ten male subjects (age: 20–29) were exposed to six different cases: (1) PC-C-M; passive cooling through mixing ventilation, (2) AC-C-M; active cooling through convection by mixing ventilation, (3) AC-C-D; active cooling through convection by displacement ventilation, (4) AC-R-M-C; active cooling through radiation by the ceiling and mixing ventilation, (5) AC-R-M-F; active cooling through radiation by the floor and mixing ventilation, and (6) AC-R-D-F; active cooling through radiation by the floor and displacement ventilation.Though all cases were designed at PMV≈0, subjective data indicate significant differences between the cases. For the prediction of thermal sensation and thermal comfort under non-uniform conditions, the operative temperature only is not sufficient. Combined local factors play an important role in the comfort assessment. Furthermore, non-uniform environments, as case 6, can achieve a comparable or even a more comfortable assessment compared to uniform environments.

Flow Regimes and Thermal Patterns in a Subway Station

As underground railway systems can generate enough heat from their operations to raise station and vehicle temperatures substantially[1,2]. This may lead to passenger discomfort and complain in warm weather conditions if the underground railway environment is not cooled. This paper presents modifications that can be made on air conditioning systems in subway stations by discussing and analyzing air flow and thermal patterns in a typical one.As CFD is now a popular design tool for engineers from different disciplines for pursuing an optimum design due to the high cost, complexity, and limited information obtained from experimental methods[3-5]. The pre-processor Gambit is used to create the geometric model with parametric features. Commercially available simulation software “Fluent 6.3” is incorporated to solve conservation of mass, momentum and energy in the processing of air distribution, and to analyze turbulence affection combined heat transfer on air distribution. In this paper work, the so-called standard k-e turbulence model, one of the most widespread turbulence models for industrial applications, was utilized. Basic parameters included in this work are air temperature, air velocity, relative humidity and turbulence parameters are used for numerical prediction of indoor air distribution. The CFD model was validated by comparing the simulation results with measurements of air velocity, and in a plane perpendicular to the supply diffuser and another plane in the vicinity of the advertisement lamp box. Thermal comfort was used in this paper to judge the impact of any modification. The thermal comfort prediction through this work was based on the PMV (Predicted Mean Vote) model and the PPD (Percentage Predicted Dissatisfied) model, the PMV and PPD were estimated using Fanger’s model.

Thermal Comfort Evaluation with Fireplace in Occupied Space

The solid fuel heaters are popular in Slovakia again, where about 50% of new freestanding homes have one. The classic fireplace, with a blazing fire open to the room as traditional symbol of comfort and security becomes with better building thermal insulation a primary rather than an occasional indulgence heat source. This paper reports the results of field measurement and simulation investigating the thermal comfort criteria in occupied space with fireplace heating system. The field study was performed in a small furnished living-room. The indoor surface temperatures were captured with infrared camera and the mean radiant temperatures were calculated by the ESP-r simulation tool. Thermal comfort prediction maps (PPD and PMV index) are presented to describe range of occupant comfort levels with mean air temperature, air velocity and clothing level variations. It was found that this system provide full area improved thermal climate only with high air temperature level. The study was limited to the case with no vertical air temperature distribution.

Landscape Attributes, Microclimate and Thermal Comfort of an Urban Square in Moderate and Dry Climate

Recent rapid urban growth in major cities highlights the role of public squares, where their success can be gauged by its frequency of use and the outdoor thermal conditions. Despite the growing number of studies on outdoor thermal comfort in temperate and dry climate, those done in the Middle East are still limited. This paper examines the effects of landscape attributes on microclimatic conditions and outdoor thermal comfort based on the physiological equivalent temperature (PET) index in Esfahan, Iran. The thermal comfort prediction and correlation between thermal environment and the use of urban space were also explored. Two fieldwork studies were conducted through simultaneous environmental measurement and questionnaire survey in winter and summer at a public square in Esfahan. The obtained data became the basis for Tmrt (mean radiant temperature) and PET estimations, supported by RayMan model. The thermal environment was investigated with different landscape attributes. The derived thermal acceptable range was found to be considerably wider that those reported in previous studies. A strong correlation was confirmed between the thermal conditions and the use of outdoor spaces. The findings demonstrated the strong positive influence of air velocity and evaporative effect of water on thermal comfort. The findings contribute toward suitable design of public squares in climates similar to Esfahan.

Monotonic type-2 fuzzy neural network and its application to thermal comfort prediction

This paper studies the monotonic type-2 fuzzy neural network (T2FNN), which can be adopted in many identification and prediction problems where the monotonicity property between the inputs and outputs is required. Sufficient conditions on the parameters of the T2FNN are first presented to ensure the monotonicity between the inputs and outputs. Then, data-driven design model for the monotonic T2FNN is built. Also, under the monotonicity constraints, a hybrid algorithm is provided to optimize the parameters of the monotonic T2FNN. This hybrid algorithm utilizes the constrained least squares method and the penalty function-based gradient descent algorithm to realize reasonable parameter initialization and optimization. At last, an application to the thermal comfort index prediction is given to verify the effectiveness of the monotonic T2FNN. Comparisons with other methods are also made.

Numerical investigations of buoyancy-driven natural ventilation in a simple atrium building and its effect on the thermal comfort conditions

Abstract In the present study use of solar-assisted buoyancy-driven natural ventilation in a simple atrium building is explored numerically with particular emphasis on the thermal comfort conditions in the building. Initially various geometric configurations of the atrium space were considered in order to investigate airflows and temperature distributions in the building using a validated computational fluid dynamics (CFD) model. The Reynolds Averaged Navier–Stokes (RANS) modelling approach with the SST-k–ω turbulence model and the Discrete Transfer Radiation Model (DTRM) was used for the investigations. The steady-state governing equations were solved using a commercial CFD solver FLUENT©. From the numerical results obtained, it was noted that an atrium space integrated with a solar chimney would be a relatively better option to be used in an atrium building. In the geometry selected, the performance of the building in response to various changes in design parameters was investigated. The produced airflows and temperature distributions were then used to evaluate indoor thermal comfort conditions in terms of the thermal comfort indices, i.e. the well-known predicted mean vote (PMV) index, its modifications especially for natural ventilation, predicted percent dissatisfied (PPD) index and Percent dissatisfied (PD) factor due to draft. It was found that the thermal conditions in the occupied areas of the building developed as a result of the use of solar-assisted buoyancy-driven ventilation for the particular values of the design parameters selected are mostly in the comfortable zone. Finally, it is demonstrated that the proposed methodology leads to reliable thermal comfort predictions, while the effect of various design variables on the performance of the building is easily recognized.

Sensitivity analysis of predicted night cooling performance to internal convective heat transfer modelling

The potential of night cooling, a passive cooling technique of growing interest, is typically investigated by numerical means. In particular multi-zone energy simulation is currently appraised for building design. Unfortunately, in addition to the inaccurate approximation of an ideally mixed room, the implemented empirical convective heat transfer coefficients (CHTCs) only apply to specific flow regimes – forcing to use arbitrary correlations and, thus, possibly limiting the usefulness of the simulation results. Therefore, the authors of this paper investigate the sensitivity of the night cooling performance to convection algorithms. First, the authors examine the applicability of convection correlations for real building enclosures, extracted from literature. Subsequently, simulations of a night cooled office room during summertime of a moderate climate (Belgium) are carried out in TRNSYS, using different convection correlations in addition to varying design parameters. The results show that the choice of the convection algorithm strongly affects the energy and thermal comfort predictions. More importantly, the convection algorithm is of the same importance as the design parameters – making an exact definition of the CHTC crucial. Therefore, additional research by experiments or airflow codes, based on fluid dynamics, is regarded necessary.

Effect of posture positions on the evaporative resistance and thermal insulation of clothing

Evaporative resistance and thermal insulation of clothing are important parameters in the design and engineering of thermal environments and functional clothing. Past work on the measurement of evaporative resistance of clothing was, however, limited to the standing posture with or without body motion. Information on the evaporative resistance of clothing when the wearer is in a sedentary or supine posture and how it is related to that when the wearer is in a standing posture is lacking. This paper presents original data on the effect of postures on the evaporative resistance of clothing, thermal insulation and permeability index, based on the measurements under three postures, viz. standing, sedentary and supine, using the sweating fabric manikin-Walter. Regression models are also established to relate the evaporative resistance and thermal insulation of clothing under sedentary and supine postures to those under the standing posture. The study further shows that the apparent evaporated resistances of standing and sedentary postures measured in the non-isothermal condition are much lower than those in the isothermal condition. The apparent evaporative resistances measured using the mass loss method are generally lower than those measured using the heat loss method due to moisture absorption or condensation within clothing. Statement of Relevance: The thermal insulation and evaporative resistance values of clothing ensembles under different postures are essential data for the ergonomics design of thermal environments (e.g. indoors or a vehicle's interior environment) and functional clothing. They are also necessary for the prediction of thermal comfort or duration of exposure in different environmental conditions.

On the unification of thermal perception and adaptive actions

Occupants exercise adaptive actions in response to discomforting environmental stimuli in an attempt to restore their comfort. These responses to adaptive actions are either ignored (conventional PMV models) or handled in an aggregated way (adaptive thermal comfort models). Furthermore the availability of adaptive actions and their effectiveness tends to be particular to a given building and climatic context. A good model should predict the probability with which available adaptive actions will be exercised and the feedback to occupants’ perceived comfort from these specific actions. In this paper we introduce a new modelling framework which does just that. Informed by results from detailed monitoring campaigns we first present a model to predict the probability distribution of thermal sensation in non air-conditioned buildings and a new method for deducing comfort zones in such buildings. We then introduce a methodology for combining recent advances in the prediction of occupants’ adaptive actions with the comfort feedback from these actions. We demonstrate how thermal sensation probability distribution may be deduced accounting for exercised adaptive actions and develop a comprehensive model for predicting comfort temperature which explicitly accounts for probable adaptive actions and their thermal feedback. We go on to describe how this modelling framework, which may be readily applied for thermal comfort prediction in specific building and climatic contexts, significantly deepens our understanding of adaptive thermal comfort mechanisms. Finally, we also describe ways of handling individuals’ diversity within this new framework as well as how it may be applied to evaluate visual and olfactory comfort.

Feasibility Study on Prediction of Temperature Distribution and Thermal Comfort with a Helmet by a Computer Simulation

Feasibility Study on Prediction of Temperature Distribution and Thermal Comfort with a Helmet by a Computer Simulation

Development of a computational tool to quantify architectural-design effects on thermal comfort in naturally ventilated rural houses

In the present study, the effect of the opening size and building direction on night hours thermal comfort in a naturally ventilated rural house is investigated. Initially, the airflow in and around the building is simulated using a validated computational fluid dynamics (CFD) model. Local climate night-time data (wind velocity and direction, temperature and relative humidity) are recorded in a weather station and the prevailing conditions are imposed in the CFD model as inlet boundary conditions. The produced airflow patterns are then used to evaluate indoor thermal comfort. For this reason, special thermal comfort indices, i.e. the well-known predicted mean vote (PMV) index and its modifications especially for natural ventilation, are calculated with respect to various residential activities. Mean values of these indices (output variables) within the occupied zone are calculated for different combinations of opening sizes and building directions (input variables), to generate a database of input–output pairs. Finally, the database is used to train and validate Radial Basis Function Artificial Neural Network (RBF ANN) input–output “meta-models”. It is demonstrated that the proposed methodology leads to reliable thermal comfort predictions, while the optimum design variables are easily recognized.

Prediction of wind environment and thermal comfort at pedestrian level in urban area

This paper reviews the recent developments in CWE research for predicting the pedestrian level wind and thermal environments in urban areas, primarily achieved by the researchers in the field of environmental engineering in Japan. First the progress in turbulence models in the last decade and in their applications to the problems related to wind climate is briefly reviewed, and the results of Architectural Institute of Japan (AIJ) collaborative project in cross comparisons of CFD results of wind environments are presented. Next, recent achievements in the field of modeling canopy flows for reproducing the aerodynamic and thermal effects of trees, buildings and automobiles are outlined. Examples of numerical results obtained using tree and vehicle canopy models are shown to demonstrate the significant effects of stationary and non-stationary subgrid scale flow obstacles on turbulent flowfield within street canyons.

Parameter study on performance of building cooling by night-time ventilation

Especially for commercial buildings in moderate climates, night-time ventilation seems to be a simple and energy-efficient approach to improve thermal comfort in summer. However, due to uncertainties in the prediction of thermal comfort in buildings with night-time ventilation, architects and engineers are still hesitant to apply this technique. In order to reduce the uncertainties, the most important parameters affecting night ventilation performance need to be identified. A typical office room was therefore modelled using a building energy simulation programme (HELIOS), and the effect of different parameters such as building construction, heat gains, air change rates, heat transfer coefficients and climatic conditions including annual variations on the number of overheating degree hours (operative room temperature >26 °C) was evaluated. Climatic conditions and air flow rate during night-time ventilation were found to have the largest effect. But thermal mass and internal heat gains also have a significant effect on cooling performance and the achievable level of thermal comfort. Using this modelling approach, significant sensitivity to heat transfer was found only for total heat transfer coefficients below about 4 W/m 2 K.

Forty years of Fanger’s model of thermal comfort: comfort for all?

The predicted mean vote (PMV) model of thermal comfort, created by Fanger in the late 1960s, is used worldwide to assess thermal comfort. Fanger based his model on college-aged students for use in invariant environmental conditions in air-conditioned buildings in moderate thermal climate zones. Environmental engineering practice calls for a predictive method that is applicable to all types of people in any kind of building in every climate zone. In this publication, existing support and criticism, as well as modifications to the PMV model are discussed in light of the requirements by environmental engineering practice in the 21st century in order to move from a predicted mean vote to comfort for all. Improved prediction of thermal comfort can be achieved through improving the validity of the PMV model, better specification of the model's input parameters, and accounting for outdoor thermal conditions and special groups. The application range of the PMV model can be enlarged, for instance, by using the model to assess the effects of the thermal environment on productivity and behavior, and interactions with other indoor environmental parameters, and the use of information and communication technologies. Even with such modifications to thermal comfort evaluation, thermal comfort for all can only be achieved when occupants have effective control over their own thermal environment. The paper treats the assessment of thermal comfort using the PMV model of Fanger, and deals with the strengths and limitations of this model. Readers are made familiar to some opportunities for use in the 21st-century information society.

407 人体の温熱快適性に与える衣服素材の影響に関する基礎的研究(省エネルギー(2),環境保全型エネルギー技術)

There is increasing concern about the health effects of the severe thermal environment in urban area. Because of these situations, it is important to estimate the thermal comfort for environmental improvements and designs. For estimating thermal comfort, surrounding environmental components, especially clothing material, are important, because clothing material has an impact on thermal exchange between exterior environment and human body. In this paper, the heat and the moisture transfer properties were examined in various conditions. The heat and the moisture transfer coefficients were calculated from measured values such as mass, temperature and humidity based on heat balance of sensible heat and latent heat. The heat and the moisture transfer coefficients can be obtained at the same time using our own making experimental apparatus. The heat and the moisture transfer coefficients indicate how effectiveness of the velocity of wind, the thickness of clothing material and the differences among fabric were clarified. The radiation properties such as reflectivity, transmissivity and adsorption of clothing were measured. These data are utilized for prediction of human thermal comfort.

Thermal-comfort analysis and simulation for various low-energy cooling-technologies applied to an office building in a subtropical climate

Simulation of buildings’ thermal-performances is necessary to predict comfort of the occupants in buildings and to identify alternate cooling control-systems for achieving better indoor thermal environments. An analysis and prediction of thermal-comfort using DesignBuilder, based on the state-of-the-art building performance simulation software EnergyPlus, is carried out in an air-conditioned multi-storeyed building in the city of Rockhampton in Central Queensland, Australia. Rockhampton is located in a hot humid-region; therefore, indoor thermal-comfort is strongly affected by the outdoor climate. This study evaluates the actual thermal conditions of the Information Technology Division (ITD) building at Central Queensland University during winter and summer seasons and identifies the thermal comfort level of the occupants using low-energy cooling technologies namely, chilled ceiling (CC), economiser usages and pre-cooling. The Fanger comfort-model, Pierce two-node model and KSU two-node model were used to predict thermal performance of the building. A sophisticated building-analysis tool was integrated with the thermal comfort models for determining appropriate cooling-technologies for the occupants to be thermally comfortable while achieving sufficient energy savings. This study compares the predicted mean-vote (PMV) index on a seven-point thermal-sensation scale, calculated using the effective temperature and relative humidity for those cooling techniques. Simulated results show that systems using a chilled ceiling offer the best thermal comfort for the occupants during summer and winter in subtropical climates. The validity of the simulation results was checked with measured values of temperature and humidity for typical days in both summer and winter. The predicted results show a reasonable agreement with the measured data.

Thermal comfort evaluation with virtual manikin methods

Computational fluid dynamics has become an important tool in the prediction of thermal comfort in occupied spaces. Despite its ability to predict temperature and velocity fields, it is more difficult to evaluate the degree of thermal comfort experienced by an occupant. This article describes the construction of a new numerical thermal manikin, with new comfort evaluation methods based on data from thermal manikin measurements as well as subjective results from several hundred experiments. The level of thermal comfort is highly dependent on the local environment. Human beings respond differently to local heat transfer in different parts of their bodies. It is suggested for that reason that local results from manikins should be presented in new clothing independent comfort zone diagrams. The research presented in here is intended to be used to evaluate system solutions that provide improved thermal climate in many different everyday situations, e.g. all types of buildings and vehicles.

DRESSMAN a thermal comfort measurement device for drivers and pilots

DRESSMAN (Dummy REpresenting Suit for Simulation of huMAN heatloss) designates a novel measurement device for climate measurements that allows the prediction of human thermal comfort experienced normally inside rooms (vehicles, aircraft, railway compartments, buildings, etc.), on the basis of climate measurements. It is specially designed for use by an operating driver or pilot. Measurement results can be listed in tabular form and can also be represented by way of colour gradations in a virtual 3D human model. Optionally, visualisation may be either online or by post processing. Due to its very quick response, DRESSMAN is particularly suited to nonstationary processes, to get information about fast physical thermal variations. DRESSMAN was specially developed to measure the expected local thermal sensations at different body parts, which are influenced by air temperature, air velocity and thermal radiation.