Showing papers on "Thermal comfort published in 1997"

Microclimatic landscape design: creating thermal comfort and energy efficiency

Abstract: B rown and Gillespie’s Microclimatic Landscape Design.\" Creating Thermal Comfort and Energy Efficiency is a readily understood explanation of how both climate and meteorology affect the landscape. It is also a brave attempt to induce designers of the landscape to utilize thermal calculations and trigonometry in their design processes. The opening chapters present lucid descriptions of how the sun impacts a site, and how winds are generated. The explanation of highand low-pressure zones, fronts, and winds is straightforward, informative, and enjoyable. (The authors frequently resort to food analogies in their descriptions of climatic and meteorological processes, with mixed success.) The text shows where \"conditional climatology\" information can be useful, and gives examples of both successful and unsuccessful landscape designs. The extent of total solar radiation beneath a tree is covered in detail, reminding us that more infrared radiation gets through than can meet the eye. The energy balance equation is provided piece by piece, so as not to overwhelm the reader with its complexity. This section makes it very clear that wind and solar radiation (along with precipitation, meaning snow) are the things designers CAN readily manipulate in landscape design, while air temperature and relative humidity are not so manipulable, so this should be attempted only in highly controlled instances such as small walled gardens or urban vestpocket parks. Each chapter ends with a series of discussion questions. These are thoughtful and occasionally playful, and their themes, continued from chapter to chapter, provide a sense of continuity throughout the book. They are not posed to elicit \"right\" or \"wrong\" answers; indeed, no answers are given, and such questions should be especially provocative for those who plan to teach from this book in a seminar format. As the text grows more detailed, the authors present case-bycase solutions of the energy balance equation to assess thermal comfort in various landscape scenarios. This makes number crunching look both easy and useful. It is here that some doubts arise. As a summary of significant conclusions, we are told that in summer, it is primarily blocking solar radiation that is the issue; in winter, it is blocking the wind first, and only then capturing solar radiation (except at southern latitudes, where perhaps solar should be first). I believe this results from the regional bias of the authors (both professors at the University of Guelph, Canada), as well as a reliance upon the energy balance calculations to the near exclusion of empirical testing. A bias toward one region leaves those of us \"outside\" wondering what some of the recommendations are based upon. This is most evident in their de-emphasis of summer wind enhancement as a worthwhile design objective. Summer wind is relegated to the role of carrying away solar heat from the exteriors of unshaded buildings. The authors rightly point out that wind warmer than either the human body or the building interior will ADD heat, rather than subtract it. But the role of psychological cooling through slight yet perceptible evaporation, and the welcome sensation of air motion--even warm air-on the skin, is ignored. The empirically derived \"extended comfort zone\" cited by Victor Olgyay (Design With Climate), Milne and Givoni (in Energy Conservation Through Building Design), Edward Ahrens, and others, includes higher air temperatures when they are accompanied by greater air velocity. For most of temperate North America (for which this book is written), there are many hours of summer days during which a building can still be brought within the comfort zone through cross ventilation; the surrounding landscape should assist this process. Cross ventilation is particularly applicable to commercial buildings with significant internal heat sources. By ignoring the movement of summer winds through buildings, or through open structures within the landscape, the authors discredit passive cooling by cross ventilation, as well as by night ventilation of thermal mass. Particularly for the North American West, these passive cooling strategies are promising for both thermal comfort and energy efficiency. Similarly, the role of the landscape in enhancing evaporative cooling is nearly ignored. In winter, solar radiation integrated into today’s code-insulated building is a much greater energysaving strategy than reduced exterior wind. The wind does not much influence a building skin’s heat losses, and today’s buildings are built so tightly that winter wind penetration is slight. While I agree that, in the open landscape, blocking the winter wind is probably more often important than access to sunlight, as we approach a building, this emphasis is reversed. Again, in the sunny winter North American West, the authors’ choice of priorities seems questionable. Daylighting is a topic entirely missing, as is the use of reflected sunlight. One result of energy-efficient landscape design should be energyefficient buildings. Thus, landscapes should encourage reflected winter daylight into windows, and should reduce the amount of summer daylight penetration, because this resource is so much greater in summer. Deciduous vines do the latter beautifully, gradually making a \"living awning\" more dense as the daylight grows stronger, less dense as daylight grows weaker, and they lend seasonal color and aroma as well. Yet, vines are almost ignored in this text, and energy efficiency seems to be exclusively about heating and cooling. This may be due to the attention given the energy balance equation and accompanying computer program; daylighting cannot readily be included in the energy balance equation. Yet the decision to daylight a building, rather than only electrically light it, will often determine which will be the main problem: cooling (with more

Residential ventilation and energy characteristics

Abstract: The role of ventilation in the housing stock is to provide fresh air and to dilute internally generated pollutants in order to ensure adequate indoor air quality. Energy is required to provide this ventilation service, either directly to move the air or indirectly to condition the outdoor air for thermal comfort. Different kinds of ventilation systems have different energy requirements. Existing dwellings in the United States are ventilated primarily through leaks in the building shell (i.e., infiltration) rather than by mechanical ventilation systems. The purpose of this paper is to ascertain, from the best available data, the energy liability associated with providing the current levels of ventilation and to estimate the energy savings or penalties associated with tightening or loosening the building envelope while still providing ventilation for adequate indoor air quality. Various ASHRAE standards (e.g., 62, 119, and 136) are used to determine acceptable ventilation levels and energy requirements. Building characteristics, energy use, and building tightness data are combined to estimate both the energy liabilities of ventilation and its dependence on building stock characteristics. The average annual ventilation energy load for a typical dwelling is about 61 GJ (roughly 50% of total space-conditioning energy load); the cost-effective savings potentialmore » is about 38 GJ. The national cost savings potential, by tightening the houses to the ASHRAE Standard 119 levels while still providing adequate ventilation through infiltration or mechanical ventilation, is $2.4 billion. The associated total annual ventilation energy load for the residential stock is about 4.5 eJ (ExaJoules).« less

Field study of occupant comfort and office thermal environments in a cold climate

Abstract: This paper presents the findings of ASHRAE research project RP-821, a field study of occupant comfort and office thermal environments in 12 mechanically ventilated office buildings in southern Quebec. A total of 877 subjects were surveyed during hot and cold months. Each interview provided a set of responses to a questionnaire and a set of physical indoor climatic measurements. The incremental effect of chairs was included in the estimates of clo values. The observed temperature optima were somewhat consistent with the predictions of comfort models and standards abased on mid-latitude climate chamber experimental data. The Montreal subjects` thermal sensation and acceptability ratings were much less accepting of non-neutral temperatures than either the PPD index or ANSI/ASHRAE Standard 55 predicted. There was a consistent request for higher air velocity, indicating that air movement guidelines may be too restrictive as set out by ANSI/ASHRAE Standard 55 and ISO 7730. Job satisfaction, general health status, and perceived levels of personal control were moderately correlated with overall generalized assessments of the workplace physical environment. Lighting levels and exposure to humidifiers outside the workplace had some relationship to specific environmental conditions occurring at the time of the interviews. There was little difference between the sexesmore » in terms of thermal sensation, although there were significantly more frequent expressions of thermal dissatisfaction from the females in the sample, despite their thermal environment being no different from that of the males.« less

A behavioural approach to thermal comfort assessment

Abstract: The paper1 describes the use of field study data to identify and quantify the individual contribution's of adaptive actions by subjects in order to achieve thermal comfort. These actions include operating building controls, responding to spatial variation of room conditions, modifying posture and clothing, and metabolic rate. In order for these actions to occur, the adaptive opportunity must exist, which to some extent is a property of the building. Suggestions for the integration of adaptive effects into comfort-predicting models are made including a way of avoiding temperature as an input, which is shown to have poor correlation with reported thermal satisfaction.

Method and system for controlling an automotive HVAC system based on the principle of HVAC work

Abstract: A method and system for automatically controlling a heating, ventilation and air-conditioning (HVAC) system of a vehicle in order to achieve thermal comfort of an occupant of the automotive vehicle receives a plurality of input signals representative of ambient temperature, sunload, and a set-point temperature. A desired amount of HVAC Work necessary to achieve thermal comfort is determined based on either a target temperature or a model of an occupant's thermal comfort. A controller controls the HVAC system based on the desired amount of HVAC Work.

A field study of office thermal comfort using questionnaire software

Abstract: Custom software to automatically administer questionnaires on computer screens was installed on computers in four open-plan offices. Five questions related to thermal comfort were presented twice per day for three months. Results indicate that this new method of subjective data collection was successful and efficient: the participants had few complaints about the method of questionnaire delivery, and a substantial literature review demonstrates that the results are comparable with results from other field studies of thermal comfort conducted using different methods. Participants responded to the questionnaire 29% of the occasions on which it could have been presented and took an average of 45 seconds to answer the five questions. Overall, the number of thermal sensation votes indicating thermal acceptability were as predicted by the ANSI/ASHRAE Standard and by the comfort theory on which this standard was based. However, the results indicate a greater sensitivity to temperatures away from the neutral temperature than theory predicts. Only 11% of the variance in thermal sensation vote was explained by indoor air temperature. Approximately 15% of the people modified their clothing in the hour prior to the appearance of the questionnaire, suggesting that clothing modification may be an important mechanism for achieving thermal comfort.

Thermal comfort analysis inside a car

Abstract: Owing to the hot harsh weather conditions in Kuwait during the summer months, the ambient temperature inside a car parked in the sun may reach 50°C and the temperature may reach 75°C. As a result, people are seriously concerned about how to keep their cars cool. This paper addresses the behaviour of the air temperature inside a car parked in the sun. Different covering arrangements were tested, including covering the front windshield, covering the front windshield and four side windows, and covering both windshields and four side windows. In addition, the novel idea was also tested of installing a solar powered ventilating fan. Such a technique was found to be very effective in reducing the inside air temperature of a car parked in the sun. The effects of the covering arrangements of the car and the solar fan on the initial cooling rate of an air-conditioning system during normal driving conditions were also analysed. Different physical parameters, namely air velocity, mean radiant temperature and humidity, were combined with air temperature to determine the comfort level of a person inside a car. © 1997 by John Wiley & Sons, Ltd.

Cooling load dynamics of rooms with cooled ceilings

Abstract: Radiant cooling technologies are emerging in the European market. The dynamic building thermal analysis program ACCURACY has therefore been enhanced so as to calculate cooling loads and analyse annual energy consumption for rooms with cooled-ceiling climate systems. The program addresses the radiant effects of the ceiling panels on thermal comfort and cooling load dynamics. The program was validated against the measured dynamic response of a test room to step heating and step cooling. The underlying principles of the program are given. It is used to calculate the cooling load for an office room. This demonstrates the applicability and significance of the new method.

Naturally ventilated buildings with heat recovery: CFD simulation of thermal environment

Abstract: This paper presents a methodology for predicting air flow and thermal comfort in naturally ventilated buildings. Numerical simulations were carried out for a naturally ventilated room with heat-pip...

Thermal comfort in naturally-ventilated and air-conditioned classrooms in the tropics.

Abstract: Author(s): Kwok, Alison G | Abstract: Designers use thermal comfort standards, such as Thermal Environmental Conditions for Human Occupancy by the American Society of Heating Refrigeration, and Air-conditioning (ASHRAE Standard 55-1992) and Moderate Thermal Environments - Determination of PMV and PPD Indices and Specification of the Conditions for Thermal Comfort by the International Standards Organizations (ISO 7730-1994), to design systems to provide a physical environment appropriate for thermal comfort. This thesis examines the comfort criteria of ASHRAE Standard 55-1992 for their applicability in tropical classrooms. The Standard specifies exact physical criteria for producing acceptable thermal environments: minimum and maximum limits for temperature, air speeds, and humidity that are often difficult to apply, particularly in hot and humid tropical climates. The Standard’s requirements are based in part on climate-controlled, laboratory experiments in temperate climates. The primary questions here ask: Are laboratory-based air-conditioning standards applicable in tropical climates? Does a different set of criteria exist for people accustomed to hot and humid climates than for those living in temperate climates? Preference for, or acceptance of, thermal factors beyond the prescriptions of the standard might suggest wider latitude for environmental control and air-conditioning set points.Borrowing primarily from previous thermal comfort studies in office buildings and adapting them for the school setting, I used a variety of methods to collect the data: survey questionnaires, physical measurements, interviews, behavioral observations, and statistical analysis techniques. Hawaii serves as a case study where 3,544 students and teachers completed questionnaires in 29 naturally-ventilated and air-conditioned classrooms in 6 schools. Concurrent measurements of the physical environment were made during each class visit.The majority of classrooms failed to meet the physical specifications of the ASHRAE Standard 55-1992 comfort zone. Analysis of subjective responses using the thermal sensation, preference, and other scales and environmental indices, found votes of more than 80% acceptability by both naturally-ventilated and air-conditioned occupants whether in or out of the comfort zone. Responses from these two school populations, suggest not only a basis for separate comfort standards, but energy conservation opportunities through raising thermostat set points and certainly by choosing to design optimized naturally-ventilated environments.

Optimized thermal zone controller for integration within a building energy management system.

Abstract: Today’s important buildings are often equipped with a Building Energy Management System (BEMS) that aims to control and optimise all the energy fluxes involving the HVAC system, but also the lighting and other appliances. The BEMS is also intended to maintain an acceptable level of comfort in the building by a proper control strategy. The notion of comfort not only means the thermal comfort but is also related to the Indoor Air Quality (IAQ) and to other discomfort sources : noise, insufficient or glaring light, ...

Thermal comfort in naturally-ventilated and air-conditioned classrooms in the tropics. - eScholarship

Abstract: Designers use thermal comfort standards, such as Thermal Environmental Conditions for Human Occupancy by the American Society of Heating Refrigeration, and Air-conditioning (ASHRAE Standard 55-1992) and Moderate Thermal Environments - Determination of PMV and PPD Indices and Specification of the Conditions for Thermal Comfort by the International Standards Organizations (ISO 7730-1994), to design systems to provide a physical environment appropriate for thermal comfort. This thesis examines the comfort criteria of ASHRAE Standard 55-1992 for their applicability in tropical classrooms. The Standard specifies exact physical criteria for producing acceptable thermal environments: minimum and maximum limits for temperature, air speeds, and humidity that are often difficult to apply, particularly in hot and humid tropical climates. The Standard’s requirements are based in part on climate-controlled, laboratory experiments in temperate climates. The primary questions here ask: Are laboratory-based air-conditioning standards applicable in tropical climates? Does a different set of criteria exist for people accustomed to hot and humid climates than for those living in temperate climates? Preference for, or acceptance of, thermal factors beyond the prescriptions of the standard might suggest wider latitude for environmental control and air-conditioning set points. Borrowing primarily from previous thermal comfort studies in office buildings and adapting them for the school setting, I used a variety of methods to collect the data: survey questionnaires, physical measurements, interviews, behavioral observations, and statistical analysis techniques. Hawaii serves as a case study where 3,544 students and teachers completed questionnaires in 29 naturally-ventilated and air-conditioned classrooms in 6 schools. Concurrent measurements of the physical environment were made during each class visit. The majority of classrooms failed to meet the physical specifications of the ASHRAE Standard 55-1992 comfort zone. Analysis of subjective responses using the thermal sensation, preference, and other scales and environmental indices, found votes of more than 80% acceptability by both naturally-ventilated and air-conditioned occupants whether in or out of the comfort zone. Responses from these two school populations, suggest not only a basis for separate comfort standards, but energy conservation opportunities through raising thermostat set points and certainly by choosing to design optimized naturally-ventilated environments.

Optimal predictive control of thermal storage in hollow core ventilated slab systems

Abstract: The energy crisis together with greater environmental awareness, has increased interest in the construction of low energy buildings. Fabric thermal storage systems provide a promising approach for reducing building energy use and cost, and consequently, the emission of environmental pollutants. Hollow core ventilated slab systems are a form of fabric thermal storage system that, through the coupling of the ventilation air with the mass of the slab, are effective in utilizing the building fabric as a thermal store. However, the benefit of such systems can only be realized through the effective control of the thermal storage. This thesis investigates an optimum control strategy for the hollow core ventilated slab systems, that reduces the energy cost of the system without prejudicing the building occupants thermal comfort. The controller uses the predicted ambient temperature and solar radiation, together with a model of the building, to predict the energy costs of the system and the thermal comfort conditions in the occupied space. The optimum control strategy is identified by exercising the model with a numerical optimization method, such that the energy costs are minimized without violating the building occupant's thermal comfort. The thesis describes the use of an Auto Regressive Moving Average model to predict the ambient conditions for the next 24 hours. A building dynamic lumped parameter thermal network model, is also described, together with its validation. The implementation of a Genetic Algorithm search method for optimizing the control strategy is described, and its performance in finding an optimum solution analysed. The characteristics of the optimum schedule of control setpoints are investigated for each season, from which a simplified time-stage control strategy is derived. The effects of weather prediction errors on the optimum control strategy are investigated and the performance of the optimum controller is analysed and compared to a conventional rule-based control strategy. The on-line implementation of the optimal predictive controller would require the accurate estimation of parameters for modelling the building, which could form part of future work.

An Automobile Heating, Ventilating and Air Conditioning (HVAC) System with a Neural Network for Controlling the Thermal Sensations Felt by a Passenger.

Abstract: The purpose of this study is to develop a heating, ventilating and air conditioning(HVAC)system for automobiles which can control the interior environment according to thermal sensations felt by humans and to evaluate the effectiveness of this HVAC system. The facial skin temperature of a passenger was estimated from environmental information, that is air temperature, wind velocity, etc., with a neural network, and the thermal sensation felt by the passenger was calculated from the facial skin temperature. Thus, this HVAC system can estimate the thermal sensation level without the direct measurement of passenger's skin temperature. The passenger's facial skin temperatures calculated by the neural network were stored in a memory IC, and the memory IC was built into the automobile. When the NN was used for retrieving the facial skin temperature of a passenger, the stored result was provided by the memory IC. This HVAC system was capable of controlling the interior environment according to the thermal sensation of the passenger, thus maintaining the passenger's level of comfort.. The passenger was more comfortable with our HVAC system than with the conventional automobile air conditioner, in particular, just after the passenger gets into the automobile. When driving the automobile on the road, this HVAC system also controls the interior environment to maintain the comfort level of the passenger.

Thermal comfort analysis using BCAP for retrofitting a radiantly heated residence

Abstract: This paper presents the use of a thermal comfort design methodology to analyze the thermal comfort distribution in a radiantly heated room. The rooms chosen for the analysis are part of a house in a retirement community in the northeastern United States. The algorithm used to calculate the thermal comfort distribution was developed under ASHRAE RP-657. This algorithm computes heat transfer within a radiantly heated or cooled room, the mass-averaged room air temperature, and the wall surface temperature distributions. The radiation formulation used in the model accommodates arbitrary placement of walls and objects within the room. The results are corroborated by comparing the calculated mass-averaged dry-bulb air temperature to the observed room air temperature. The work reported here was funded under ASHRAE RP-907.

Gas-fired desiccant system for retail super center

Abstract: Concerns about indoor air quality have led to increasing outside air requirements that have prompted HVAC system designers to rethink how to handle outside air. The resulting increase in latent load can cause a variety of problems such as uncomfortably high humidity, mold and mildew, sweating ducts and higher energy cost. These problems occur not only in very humid climates but also in moderate climates during the swing season when the sensible load is low and the outside humidity is high. This combined with increasing concern for occupant comfort has led engineers to look for HVAC designs that provide good temperature and humidity control while still providing adequate quantities of outside air ventilation. This article describes the results of a one-year monitored evaluation of a gas-fired desiccant makeup air system used in a Wal-Mart super center. The system provides continuous fresh-air ventilation and independent temperature and humidity control. It also demonstrates the potential for energy savings and reduced first cost of the HVAC system. This approach, investigated by the owners` design team and independently monitored and verified in this Gas Research Institute-funded field study, has proven to be a cost-effective solution to meeting the new ventilation standard.

Recent research on an indirect evaporative cooler (IEC) Part 2: thermal performance of a non‐conditioned building coupled with an IEC

Abstract: The thermal performance of a non-conditioned building fitted with an indirect evaporative cooler (IEC) has been investigated in terms of hourly, monthly and seasonal discomfort index. The effect of various design parameters of the IEC on the discomfort index has been investigated for three different climatic areas of India, i.e. hot-dry, warm, humid and composite. The analysis has shown that the IEC is effective for creating thermal comfort conditions in buildings in dry-hot and composite climates.

Three-Dimensional Simulation for Urban Warming and Proposal of an Environmental Index for Urban Environment.

Abstract: In most cities, it is becoming evident that the increase in energy consumption is causing environmental problems, including a temperature rise in the urban atmosphere (an urban heat island) and air pollution. The present paper reports on the results of a three-dimensional computer simulation of the urban heat island in the Tokyo metropolitan area, as well as moisture migration. The three-dimensional governing equations for the urban atmospheric boundary layer were formulated by virtue of the vorticity-velocity vector potential method. Particular attention was focused on the representation of a buoyancy term in the equation of motion in the vertical direction, thereby describing the cross-over effect and stratified inversion layer near the ground surface. According to a recent computer simulation for urban warming in the Tokyo metro area in 2031, the maximum ambient temperature in the evening (18 : 00) at Otemachi will exceed 42°C. In contrast to the interior thermal comfort in residential and office buildings, the urban outdoor comfort is strongly affected by intense thermal radiation coming from the surface of the structures, as well as solar radiation. Motivated by the above facts, we propose a new standard effective temperature index (USET*), which is applicable to urban comfort. By using this comfort index, assessment of the urban environment is made for both presentday Tokyo and Tokyo around 2030. Furthermore, it is suggested that a comprehensive urban environmental index (UEI). which includes pollutants and ultraviolet rays, is adopted for the future urban environment.