Information about Thermal Comfort
Human thermal comfort is the state of mind that expresses satisfaction with the surrounding environment, according to ASHRAE Standard 55. Achieving thermal comfort for most occupants of buildings or other enclosures is a goal of HVAC design engineers. Indoor air quality is not part of thermal comfort, but is also a key concern of HVAC designers.
Fundamental studies of thermal comfort, such as acceptable ranges of dry-bulb temperatures, relative humidities, and activity levels were completed in the 1970s. Many of these studies, which led to the development and refinement of ASHRAE Standard 55, were performed at Kansas State University by Ole Fanger and others. Some key findings were that not everyone will be satisfied by a particular set of indoor environmental conditions, but in ranges of conditions about 80% express satisfaction. If very good conditions are in place, a maximum of 95% of all persons might be satisfied. Statistical methods were used to evaluate the thermal comfort opinions of the many test subjects to yield what are known as the comfort conditions; the predicted mean vote (PMV) was one of the measures used.
Most important for thermal comfort is the so called operative temperature. This is the average of the air dry-bulb temperature and of the mean radiant temperature at the given place in a room. In addition, there should be low air velocities and no 'drafts', little variation in the radiant temperatures from different directions in the room, the humidity has to be in a comfortable range, and the air temperatures in a height of 0.1 m above the floor should not be more than 2°C lower than than the temperature at the place of the occupant's head. Also the temperatures should not change too rapidly - neither across the space nor with time.
In addition to environmental conditions, thermal comfort depends on the clothing and activity level of a person. The amount of clothing is measured against a standard amount that is roughly equivalent to a typical business suit, shirt, and undergarments. Activity level is compared to being seated quietly, such as in a classroom.
This standard amount of insulation required to keep a resting person warm in a windless room at 70 °F (21.1°C) is equal to one Clo. Clo units can be converted to R-value by multiplying Clo by 0.88 and R-value can be converted to Clo by multiplying R-value by 1.136.
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Fundamental studies of thermal comfort, such as acceptable ranges of dry-bulb temperatures, relative humidities, and activity levels were completed in the 1970s. Many of these studies, which led to the development and refinement of ASHRAE Standard 55, were performed at Kansas State University by Ole Fanger and others. Some key findings were that not everyone will be satisfied by a particular set of indoor environmental conditions, but in ranges of conditions about 80% express satisfaction. If very good conditions are in place, a maximum of 95% of all persons might be satisfied. Statistical methods were used to evaluate the thermal comfort opinions of the many test subjects to yield what are known as the comfort conditions; the predicted mean vote (PMV) was one of the measures used.
Most important for thermal comfort is the so called operative temperature. This is the average of the air dry-bulb temperature and of the mean radiant temperature at the given place in a room. In addition, there should be low air velocities and no 'drafts', little variation in the radiant temperatures from different directions in the room, the humidity has to be in a comfortable range, and the air temperatures in a height of 0.1 m above the floor should not be more than 2°C lower than than the temperature at the place of the occupant's head. Also the temperatures should not change too rapidly - neither across the space nor with time.
In addition to environmental conditions, thermal comfort depends on the clothing and activity level of a person. The amount of clothing is measured against a standard amount that is roughly equivalent to a typical business suit, shirt, and undergarments. Activity level is compared to being seated quietly, such as in a classroom.
This standard amount of insulation required to keep a resting person warm in a windless room at 70 °F (21.1°C) is equal to one Clo. Clo units can be converted to R-value by multiplying Clo by 0.88 and R-value can be converted to Clo by multiplying R-value by 1.136.
See also
References
- Thermal Comfort, P. O. Fanger, McGraw-Hill, New York, 1970.
- Thermal Comfort chapter, Fundamentals volume of the ASHRAE Handbook, ASHRAE, Inc., Atlanta, GA, 2005.
- Weiss, Hal (1998). Secrets of Warmth: For Comfort or Survival. Seattle, WA: Mountaineers Books. ISBN 0-89886-643-X. OCLC 40999076.
External links
HVAC may also stand for High-voltage alternating current
HVAC (pronounced either "H-V-A-C" or, occasionally, "aitch-vak") is an initialism/acronym that stands for "heating, ventilation, and air conditioning"...... Click the link for more information.
Indoor Air Quality (IAQ) deals with the content of interior air that could affect health and comfort of building occupants. The IAQ may be compromised by microbial contaminants (mold, bacteria), chemicals (such as carbon monoxide, radon), allergens, or any mass or energy stressor
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Kansas State University, officially called "Kansas State University of Agriculture and Applied Science" [2] but commonly shortened to K-State, is an institution of higher learning located in Manhattan, Kansas, in the United States.
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Povl Ole Fanger (July 16, 1934 – September 20, 2006) was an expert in the field of the health effects of indoor environments. He was a University Professor at Syracuse University when he died at the age of 72 from an abdominal aortic aneurism.
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In the study of human thermal comfort, the operative temperature is one of several parameters devised to measure the air's cooling effect upon a human body. It is equal to the dry-bulb temperature at which a specified hypothetical environment would support the same heat loss from
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R-value is a term predominantly used in the building industry to rate the insulative properties of construction materials and building assemblies.
It is derived from the U-factor (see below). The higher the R-value, the greater insulation value.
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It is derived from the U-factor (see below). The higher the R-value, the greater insulation value.
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Povl Ole Fanger (July 16, 1934 – September 20, 2006) was an expert in the field of the health effects of indoor environments. He was a University Professor at Syracuse University when he died at the age of 72 from an abdominal aortic aneurism.
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Characterizing how air is introduced to, flows through, and is removed from spaces is called room air distribution.[1] HVAC airflow in spaces generally can be classified by two different types: mixing (or dilution) and displacement.
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Psychrometrics or psychrometry are terms used to describe the field of engineering concerned with the determination of physical and thermodynamic properties of gas-vapor mixtures.
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The term air conditioning most commonly refers to the cooling and dehumidification of indoor air for thermal comfort. In a broader sense, the term can refer to any form of cooling, heating, ventilation or disinfection that modifies the condition of air.
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OCLC Online Computer Library Center
Nonprofit membership cooperative
Founded Dublin, OH, U.S. (1967)
Headquarters Dublin, OH, U.S.
Key people Robert L.
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Nonprofit membership cooperative
Founded Dublin, OH, U.S. (1967)
Headquarters Dublin, OH, U.S.
Key people Robert L.
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