Showing papers on "Thermal comfort published in 2001"

The adaptive model of thermal comfort and energy conservation in the built environment.

Abstract: Current thermal comfort standards and the models underpinning them purport to be equally applicable across all types of building, ventilation, occupancy pattern and climate zone. A recent research project sponsored by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE, RP-884) critically evaluated these assumptions by statistically analysing a large database of research results in building comfort studies from all over the world (n=22,346). The results reported in this paper indicated a clear dependence of indoor comfort temperatures on outdoor air temperatures (instead of outdoor effective temperature ET* used in RP-884), especially in buildings that were free-running or naturally ventilated. These findings encourage significant revisions of ASHRAE’s comfort standard in terms of climatically relevant prescriptions. The paper highlights the potential for reduced cooling energy requirements by designing for natural or hybrid ventilation in many moderate climate zones of the world.

Thermal comfort controller having an integral energy savings estimator

Abstract: A thermal comfort controller using various recovery methods to change the indoor temperature to meet set points in a setup/setback schedule to maintain thermal comfort for occupants of an enclosure. The thermal comfort controller further comprising an apparatus to determine the expected energy savings when modifying the setup/setback schedule for the enclosure in which the temperature controller is used. The energy savings information may be displayed to the enclosure occupant for further consideration.

Climate, Comfort & Natural Ventilation: A new adaptive comfort standard for ASHRAE Standard 55

Abstract: Recently proposed revisions to ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy, include a new adaptive comfort standard (ACS) that allows warmer indoor temperatures for naturally ventilated buildings during summer. The ACS is based on the analysis of 21,000 sets of raw data compiled from field studies in 160 buildings, both airconditioned and naturally ventilated, located on four continents in varied climatic zones. This paper summarizes this earlier research, presents some of its findings for naturally ventilated buildings, and discusses the process of getting the ACS incorporated into Std. 55. We suggest ways the ACS could be used for the design, operation, or evaluation of buildings, and for research applications. We also use GIS mapping technology to examine the energy-savings potential of the ACS on a regional scale. Finally, we discuss related new directions for researchers and practitioners involved in the design of buildings and their environmental control systems.

Thermal comfort based fuzzy logic controller

Abstract: Most heating, ventilation and air conditioning (HVAC) control systems are considered as temperature control problems. In this work, the predicted mean vote (PMV) is used to control the indoor temperature of a space by setting it at a point where the PMV index becomes zero and the predicted percentage of persons dissatisfied (PPD) achieves a maximum threshold of 5%. This is achieved through the use of a fuzzy logic controller that takes into account a range of human comfort criteria in the formulation of the control action that should be applied to the heating system to bring the space to comfort conditions. The resulting controller is free of the set up and tuning problems that hinder conventional HVAC controllers. Simulation results show that the proposed control strategy makes it possible to maximize the indoor thermal comfort and, correspondingly, a reduction in energy use of 20% was obtained for a typical 7-day winter period when compared with conventional control.

Virtual Thermal Comfort Engineering

Abstract: Simulation of passenger compartment climatic conditions is becoming increasingly important as a complement to wind tunnel and field testing to help achieve improved thermal comfort while reducing vehicle development time and cost. Delphi Harrison Thermal Systems has collaborated with the University of California, Berkeley to develop the capability of predicting occupant thermal comfort to support automotive climate control systems. At the core of this Virtual Thermal Comfort Engineering (VTCE) technique is a model of the human thermal regulatory system based on Stolwijk’s model but with several enhancements. Our model uses 16 body segments and each segment is modeled as four body layers (core, muscle, fat, and skin tissues) and a clothing layer. The comfort model has the ability to predict local thermal comfort level of an occupant in a highly non-uniform thermal environment as a function of air temperature, surrounding surface temperatures, air velocity, humidity, direct solar flux, as well as the level of activity and clothing type of each individual. VTCE takes into account the geometrical configuration of the passenger compartment including glazing surfaces, pertinent physical and thermal properties of the enclosure with particular emphasis on glass properties. Use of Virtual Thermal Comfort Engineering (VTCE) will allow for exploration of different climate control strategies as they relate to human thermal comfort in a quick and inexpensive manner.

Improving indoor climate and comfort with wooden structures

Abstract: In this report, the moisture performance of a bedroom in a wooden apartment building is studied numerically using hourly weather data from 4 different cities (Helsinki, Finland, Saint Hubert, Belgium, Holzkirchen, Germany and Trapani, Italy). The bedroom is occupied for 9 hours by two adults during the night (22:00 to 7:00), the volume is 32.4 m3 and the wall surface area is 60 m2. With the basic input parameters (moisture production of 60g/h, ventilation rate of 0.5 ach and a permeable internal coating on the ceiling and walls) the moisture transfer between indoor air and the building structure is very active. With these parameters, the moisture transfer between indoor air and structures can significantly improve the indoor climate and air quality compared to the case where the internal coating is vapour tight. Moisture storage in wood based materials can reduce the peak humidity during the night and this moisture can then be removed by ventilation air during the following day. In general (at a ventilation rate of 0.5 ach), the indoor humidity is close to the outdoor humidity when the occupants enter the room (22:00) for all structures and materials. The increase in absolute humidity during the night is quite independent of the climate, but the amount of time when the indoor climate and air quality are unsatisfactory is very dependent on the climate. Passive methods of controlling the indoor climate are naturally more successful in moderate climates than in hot and humid climates, even though they provide benefits in all climates.

Personal thermal comfort system using thermal storage

Abstract: The present invention is directed to method and apparatuses for modifying the air of a localized zone to suit personal comfort. This invention includes the heating or cooling of the air in the localized zone with a novel apparatus and inhibiting the concurrent release of byproduct air at undesirable temperatures while using a heat pump. The apparatus includes a thermal storage mass that provides a reservoir for the undesirable heating or cooling effects for later restoration. This restoration would occur at a predetermined time in predetermined amounts, typically when the localized zone is unoccupied.

Assessment of thermal comfort during surgical operations

Abstract: The thermal environment was studied in two operating rooms at the Montreal General Hospital. Thermal comfort of the staff was assessed based on measurements of the environment during surgical operations and on questionnaires given to the staff. Infrared pictures of representative surfaces and people were also taken and, when possible, skin and core temperatures of the patient were also measured. The thermal resistance of clothing and the activity levels for all the people were estimated from published tables and previous research studies. Three thermal zones were studied: zone 1, bounded by the patient, the surgical staff, and the surgical lights; zone 2, the adjacent area; and zone 3, the farthest one. It was found that under the present environmental and personal conditions it is not possible to provide all groups of people with an acceptable thermal environment. In general, surgeons tend to feel from slightly warm to hot (they sweat very often), anesthesia staff and nurses from slightly cool to cold, and the patient from slightly cool to very cold (patients sometimes woke up shivering). In addition to questionnaires, thermal comfort was predicted based on Fanger’s PMV model, which assumes a uniform thermal environment. Based on Fanger’s model, the air temperature that could have ensured satisfactory thermal comfort for the surgeon, under the particular conditions studied, was about 66°F (19°C). However, at that temperature, to remain in good thermal comfort, nurses and anesthetists must be clothed with at least 0.9 clo and the patient covered with at least 1.6 clo. In practice, however, the radiant temperature asymmetry from the surgical lights in zone 1, which ranges between 11°F (6°C) and 13°F (7°C) over the operating table and between 18°F (10°C) and 22°F (12°C) over the floor (at a level of 1.1 m), causes surgeons’ dissatisfaction with the environment at any air temperature. Possible solutions to minimize radiation and its effects on the surgeons are discussed, which would permit ambient temperatures more favorable for the patient and all the staff.

Climate, comfort, & natural ventilation: a new adaptive comfort standard for ASHRAE standard 55 - eScholarship

Abstract: Recently proposed revisions to ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy, include a new adaptive comfort standard (ACS) that allows warmer indoor temperatures for naturally ventilated buildings during summer. The ACS is based on the analysis of 21,000 sets of raw data compiled from field studies in 160 buildings, both airconditioned and naturally ventilated, located on four continents in varied climatic zones. This paper summarizes this earlier research, presents some of its findings for naturally ventilated buildings, and discusses the process of getting the ACS incorporated into Std. 55. We suggest ways the ACS could be used for the design, operation, or evaluation of buildings, and for research applications. We also use GIS mapping technology to examine the energy-savings potential of the ACS on a regional scale. Finally, we discuss related new directions for researchers and practitioners involved in the design of buildings and their environmental control systems.

Environmental Comfort Criteria: Weighting and Integration

Abstract: This paper presents an integration method for evaluating environmental quality in office buildings based on a series of interviews with 50 experts in the field of environmental quality in the built environment. A structured questionnaire was completed by experts during the interviews. The categories of environmental quality considered in this evaluation include lighting comfort, acoustic comfort, thermal comfort, and acceptable indoor air quality. Each category includes a set of performance criteria. Sixty-five performance criteria covering the evaluation of environmental quality in office buildings were extracted from the interviewed experts. The development of this integration method for assessing the environmental quality of built environments is described and an illustration of its application is presented.

Analysis of mean radiant temperature and thermal comfort

Abstract: Mean radiant temperature is an important environmental parameter that influences building performance and occupants' thermal comfort. In this technical note, the effect of glazing on the mean radiant temperature and thermal comfort in rooms is analysed. It is shown that a tall and narrow window performs better than a square window in terms of indoor thermal comfort. Also, double-glazing is effective in reducing the thermal discomfort due to radiant asymmetry.

The Physical Environment and Occupant Thermal Perceptions in Office Buildings An Evaluation of Sampled Data from Five European Countries

Abstract: The results from a large field study of thermal comfort in European office buildings are reported. Measurements of physical environmental conditions and occupant perceptions were collected over sixteen months from twenty-six different office buildings located in France, Greece, Portugal, Sweden and the UK. This thesis focuses on the physical environmental measurements and occupant thermal perceptions; however, additional variables with connections to environmental satisfaction are also examined. An overview of human comfort theory is presented to help place this thesis in appropriate context. The overview presents thermal comfort issues within a broad framework of human response to the environment including physical, physiological, behavioural, psychological and other variables. A more narrowly focused overview of current thermal comfort research is also included. The work attempts to show relationships and produce useful information from the data set using graphical methods, especially lowess, a locally weighted regression based scatter plot smoothing technique. The objective of using this approach is to literally show the relationships visually. This approach allows the data set itself to illustrate the actual thermal conditions in European office buildings and the occupant perceptions of those conditions along with illustrating relationships. The data are examined in some detail with key relationships identified and explored. Significant differences between countries, both for the physical conditions and the perceptions of those conditions are identified. In addition, the variation over the course of the year for each country is explored. The relationship of daily average outdoor temperatures to indoor temperatures and indoor temperature perceptions is found to be critically important. The relationships, which appear to drive perceptions of thermal comfort, occur in complex ways, making simple, all encompassing explanations impossible. The nature and size of the variations means that the application of simple European wide models of thermal comfort is questionable. It appears that individuals in different Europe countries have different expectations for their indoor office thermal environment.