Thermal comfort is a state of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation (ANSI/ASHRAE Standard 55). The human body can be seen as a heat engine in which food is the input energy. The human body will produce excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to the temperature difference. In a cold environment, the body loses more heat to the environment and in hot environments, the body does not have enough heat. Both hot and cold scenarios cause discomfort. Maintaining thermal comfort standards for occupants of buildings or other enclosures is one of the important goals of HVAC (heating, ventilation, and air conditioning) design engineers. Most people will feel comfortable at room temperature, daily temperatures of around 20 to 22 Â ° C (68 to 72 Â ° F), but these can vary greatly between individuals and depend on factors such as activity levels, clothing, and moisture.
Thermal neutrality is maintained when the heat generated by human metabolism is allowed to disappear, thus maintaining a thermal balance with the surrounding environment. The main factors affecting thermal comfort are the factors that determine the heat gain and loss, ie the metabolic rate, clothing isolation, air temperature, average temperature of radiation, air velocity and relative humidity. Psychological parameters, such as individual expectations, also affect thermal comfort.
The Predicted Mean Vote (PMV) model stands among the best known thermal comfort models. It was developed using the principles of heat balance and experimental data collected in climate spaces that were controlled under steady state conditions. The adaptive model, on the other hand, was developed based on hundreds of field studies with the idea that occupants interact dynamically with their environment. Occupants control their thermal environments by way of clothing, windows that can be operated on, fans, personal heaters, and sun shades.
The PMV model can be applied to air-conditioned buildings, whereas adaptive models can generally be applied only to buildings where no mechanical systems are installed. There is no consensus on which convenience models should be applied to partially spatially or temporally conditioned buildings.
The thermal comfort calculation in accordance with ANSI/ASHRAE Standard 55 can be performed freely with CBE Thermal Comfort Tool for ASHRAE 55.
Similar to ASHRAE Standard 55 there are other comfort standards such as EN 15251 and ISO 7730 standard.
Video Thermal comfort
Significance
Satisfaction with the thermal environment is important for its own sake and therefore affects productivity and health. Office workers who are satisfied with their thermal environment are more productive. Thermal discomfort has also been known to cause symptoms of sick building syndrome. The combination of high temperature and high humidity works to reduce thermal comfort and indoor air quality.
Although a single static temperature can be comfortable, thermal pleasure, alliesthesia is usually caused by a variety of thermal sensations. The adaptive model of thermal comfort allows the flexibility in designing a natural ventilated building that has more indoor conditions. Such buildings can save energy and have the potential to create more satisfied residents.
Maps Thermal comfort
Influencing factor
Because there is great variation from person to person in terms of physiological and psychological satisfaction, it is difficult to find the optimal temperature for everyone in a given space. Laboratory and field data have been collected to determine the conditions to be found convenient for a certain percentage of occupants.
There are six main factors that directly affect thermal comforts that can be grouped into two categories: personal factors - because they are the occupant characteristics - and environmental factors - which are conditions of a hot environment. The first is the metabolic rate and the level of clothing, the last is air temperature, average temperature of radiation, air velocity and humidity. Even if all these factors can change over time, the standard usually refers to steady conditions to learn thermal comfort, allowing only limited temperature variations.
Metabolic rate
People have different metabolic rates that can fluctuate due to the level of activity and environmental conditions. The ASHRAE 55-2010 Standard defines the metabolic rate as the rate of transformation of chemical energy into heat and mechanical work by metabolic activity in an organism, usually expressed in units of total body surface area. The metabolic rate is expressed in units met, defined as follows:
1 met = 58.2 W/mÃ,² (18.4 Btu/hÃ,  · ftÃ,²), which is equal to the energy produced per unit surface area of ​​the average person sitting at rest. The average surface area of ​​a person is 1.8 mÃ,² (19Ã, ftÃ,²).
ASHRAE Standard 55 provides a price table that has been met for various activities. Some common values ​​are 0.7 met for sleep, 1.0 met for sitting and quiet position, 1.2-1.4 met for light standing activities, 2.0 met or more for activities involving movement, walking, lifting weights heavy or operate the machine. For intermittent activity, the Standard states that it is permissible to use a time-weighted metabolic rate if individuals perform activities that vary for an hour or less. For longer periods, different metabolic rates should be considered.
According to the ASHRAE Handbook of Fundamentals, estimating metabolic rate is complex, and for levels above 2 or 3 meet - especially if there are various ways of doing such activities - low accuracy. Therefore, this Standard does not apply to activities with an average rate higher than 2 meetings. Met values ​​can also be determined more accurately than those tabulated, using empirical equations that take into account the rate of oxygen consumption of breathing and the production of carbon dioxide. Another physiological but less accurate method is associated with heart rate, because there is a relationship between the latter and oxygen production.
The Compendium of Physical Activities is used by physicians to record physical activity. It has a different definition of met that is the ratio of the metabolic rate of activity referred to the resting metabolic rate. Since the formulation of this concept differs from the concept used by ASHRAE, this value can not be used directly in PMV calculations, but it opens up new ways to measure physical activity.
Food and beverage habits may have an influence on the metabolic rate, which indirectly affects thermal preferences. This effect may change depending on food and beverage intake. Body shape is another factor that affects thermal comfort. The heat dissipation depends on the body surface area. Tall and thin people have a higher surface to volume ratio, can dissipate heat more easily, and can tolerate higher temperatures than someone with a rounded body shape.
Isolation of clothing
The amount of thermal insulation imposed by a person has a great impact on thermal comfort, as it affects heat loss and consequently thermal balance. Insulating clothing layers prevent heat loss and can help keep a person warm or cause overheating. Generally, the thicker the garment, the greater the insulation capacity it has. Depending on the type of clothing material made from, air movement and relative humidity can decrease the insulating ability of the material.
1 clo equal to 0.155 mÃ,²Ã,  · K/W (0.88 Ã,  ° FÃ,  · ftÃ,²Ã,  · h/Btu). This corresponds to trousers, a long-sleeved shirt, and a jacket. The value of clothing insulation for general ensemble or other single clothing can be found in ASHRAE 55.
Air temperature
Air temperature is the average temperature of air around the occupants, with respect to location and time. According to ASHRAE 55 standards, the average space takes into account the ankle, waist and head levels, which vary for occupants sitting or standing. The temporal averages are based on three-minute intervals with at least 18 equally spaced points. The temperature of the air is measured by a dry-ball thermometer and for this reason it is also known as the dry-ball temperature.
Means radiation temperature
The temperature of the jet is related to the amount of radiant heat transferred from the surface, and it depends on the material's ability to absorb or radiate heat, or its emissivity. The average temperature of the jets depends on the temperature and emissivity of the surrounding surface as well as the view factor, or the number of surfaces that are "visible" to the object. So the average temperature of the jets that a person experiences in the room with the flowing sun rays varies depending on how much of his body is in the sun.
Airspeed
In HVAC, air velocity is defined as the rate of air movement at a point, regardless of direction. According to ANSI/ASHRAE Standard 55, it is the average speed of air exposed to the body, with respect to location and time. The temporal mean is equal to the air temperature, whereas the spatial averages are based on the assumption that the body is exposed to uniform air velocities, according to the thermo-physiological SET model. However, some spaces may provide a very uniform air velocity field and a loss of skin heat which can not be considered uniform. Therefore, the designer must decide on the right averages, especially including the incidence of airspeed on the part of the body that is not clothed, which has a greater cooling effect and potential local discomfort.
Relative humidity
Relative humidity (dH) is the ratio of the amount of water vapor in air to the amount of water vapor that can be retained by air at certain temperatures and pressures. While the human body has sensors inside the skin that are quite efficient at sensing heat and cold, relative humidity is detected indirectly. Sweating is an effective heat loss mechanism that relies on the evaporation of the skin. But at high RH, the air is close to the maximum water vapor it can contain, so evaporation, and hence heat loss, decreases. On the other hand, a very dry environment (RH & lt; 20-30%) is also uncomfortable because of its effect on mucous membranes. Recommended indoor humidity levels are in the 30-60% range in air-conditioned buildings, but new standards such as adaptive models allow lower and higher moisture, depending on other factors involved in thermal comfort.
Recently, the relative humidity effect is low and high air velocities are tested in humans after bathing. The researchers found that relatively low humidity caused thermal discomfort as well as dry and itchy sensations. It is recommended to keep the relative humidity levels higher in the bathroom than other rooms in the house for optimal conditions.
Skin tone
Skin anxiety is defined as "the total proportion of the surface area of ​​the skin of a body covered with sweat." Wet skin in various areas also affects the thermal comfort felt. Humidity can increase the feeling of wetness in different areas of the body, leading to the perception of discomfort. This is usually localized in different parts of the body, and the local thermal comfort limit for the dampened skin is different from the location of the body. The extremities are much more sensitive to thermal discomfort than wet than the torso. Although local thermal discomfort can be caused from wetness, thermal comfort from the rest of the body will not be affected by the wetness of certain parts.
Temperature and humidity interactions
Various types of temperatures have evidently been developed to combine air temperature and humidity. For higher temperatures, there is a quantitative scale, such as a heat index. For lower temperatures, related interactions are only identified qualitatively:
High humidity and low temperatures cause the air to feel cold.
Cold air with high relative humidity "feels" colder than dry air at the same temperature because high humidity in cold weather increases heat conduction from the body.
There is controversy about why damp cold air feels colder than dry, dry air. Some believe it is because when the humidity is high, our skin and clothing become moist and better the heat conductor, so there is more cooling by conduction.
Natural ventilation
Many buildings use HVAC units to control their thermal environments. Other buildings are naturally ventilated and do not rely on such mechanical systems to provide thermal comfort. Depending on the climate, this can drastically reduce energy consumption. Sometimes this is seen as a risk, because indoor temperatures can be too extreme if the building is poorly designed. Properly designed, natural ventilated buildings keep indoor conditions in the window opening range and use summer fans, and wearing extra clothes in the winter, can make people feel comfortable thermally.
Model
When discussing thermal comfort, there are two different main models that can be used: static models (PMV/PPD) and adaptive models.
PMV/PPD Method
The PMV/PPD model was developed by P.O. Danger uses heat balance equations and empirical studies of skin temperature to define comfort. The standard thermal comfort survey asks subjects about their thermal sensations on a seven-point scale from cold (-3) to hot (3). The Fanger equation is used to calculate Predicted Mean Vote (PMV) from a large group of subjects for a special combination of air temperature, average temperature of radiation, relative humidity, air velocity, metabolic rate, and clothing isolation. Zero is the ideal value, representing thermal neutrality, and comfort zone is determined by a combination of six parameters in which the PMV is within the recommended limits (-0.5 & lt; PMV & lt; 0.5). While predicting the heat sensation of a population is an important step in determining what conditions are comfortable, it will be useful to consider whether people will be satisfied or not. Fanger developed another equation for linking PMV with Predicted Percentage of Dissatisfaction (PPD). This relationship is based on studies that survey subjects in spaces where indoor conditions can be controlled appropriately.
This method treats all the same residents and ignores the location and adaptation to the hot environment. It basically states that the indoor temperature should not change like the season. Instead, there should be a set of temperatures throughout the year. It takes a more passive attitude that humans do not have to adapt to different temperatures because it will always be constant.
ASHRAE Standard 55-2010 uses the PMV model to set requirements for indoor heating conditions. It takes at least 80% of the residents to be satisfied.
The CBE Thermal Convenience Tool for ASHRAE 55 allows users to enter six convenience parameters to determine whether a particular combination complies with ASHRAE 55. The results are displayed on the humidity-temperature or humidity-temperature graph and show the relative temperature and humidity range that will feel comfortable with the input values given for the remaining four parameters.
Enhanced airspeed method
ASHRAE 55 2013 contributes airspeed above 0.2 meters per second (0.66Ã, ft/sec) separately from the base model. Because air movement can provide direct cooling to people, especially if they are not wearing a lot of clothes, higher temperatures can be more comfortable than predicted PMV models. Air speeds up to 0.8 m/s (2.6 m/s) are allowed without local control, and 1.2 m/s is possible with local controls. This elevated air movement raises the maximum temperature for office space in summer to 30 ° C from 27.5 ° C (86.0-81,5 ° F).
Virtual Energy for Thermal Comfort
"Virtual Energy for Thermal Comfort" is the amount of energy necessary to make the relatively non-air-conditioned building relatively comfortable with air conditioning. This is based on the assumption that the house will eventually install an air conditioner or heater. Passive design improves thermal comfort in the building, thereby reducing the demand for heating or cooling. In many developing countries, however, most residents today are neither hot nor cold, due to economic constraints, as well as climatic conditions that limit the line of comfort conditions such as winter nights in Johannesburg (South Africa) or warm summer days in San Jose , Costa Rica. At the same time, as income increases, there is a strong tendency to introduce cooling and heating systems. If we recognize and appreciate passive design features that improve thermal comfort today, we reduce the risk of having to install an HVAC system in the future, or at least ensure that the system will be smaller and less used. Or in case the heating or cooling system is not installed due to the high cost, at least one should not suffer any discomfort in the room. To give an example, in San Jose, Costa Rica, if a house is being designed with a high degree of glaze and a small opening size, the internal temperature will easily rise above 30 ° C (86 ° F) and natural ventilation will not be enough to removing internal heat gain and solar gain. This is why Virtual Energy for Comfort is important.
The World Bank's assessment tool of EDGE software (Excellence in Design for Greater Efficiency) illustrates potential problems with discomfort in buildings and has created the concept of Virtual Energy for Convenience that provides a way to present potential thermal discomfort. This approach is used to provide design solutions that enhance thermal comfort even in buildings that run free. Although including the requirements for overheating at CIBSE, overcooling has not been assessed. However, overcooling can be a problem, especially in developing countries, for example in cities like Lima (Peru), Bogota, and Delhi, where cooler indoor temperatures can occur frequently. This may be a new area for research and design guidance to reduce discomfort.
Standard effective temperature
The standard effective temperature (SET *) is the human response model of the thermal environment. Developed by A.P. Gagge and accepted by ASHRAE in 1986, he is also referred to as the Pierce Two-Node model. The calculations are similar to PMV because they are a comprehensive comfort index based on a heat balance equation that combines personal factors of clothing and metabolic rate. The fundamental difference is that a two-node method is needed to represent human physiology in measuring skin temperature and skin wetness.
ASHRAE 55-2010 defines SET as "an imaginary environmental temperature at 50% relative humidity, 0.1 m/s [0.33 ft/dt] average air velocity, and average radiant temperature equal to air temperature on average, where total heat loss from the skin of an imaginary occupant with an activity level of 1.0 meets and a clothing rate of 0.6 clo equal to that of a person in the actual environment, with apparel and actual activity levels. "
Research has tested models against experimental data and found it tends to overestimate skin temperature and underestimate the skin's wetness. Fountain and Huizenga (1997) developed a thermal sensation prediction tool that computes SET.
Local thermal discomfort
Although thermal comfort is usually discussed for the body as a whole, thermal dissatisfaction can also occur only for certain parts of the body, due to local sources of unwanted heating, cooling or air movement. According to ASHRAE 55-2010 standards, there are four major causes of thermal discomfort to be considered. A part of the standard specifies the requirements for these factors, which apply to the person dressed mildly involved in near permanent physical activity. This is because people with higher metabolic rates and/or more thermally sensitive clothing insulation, and consequently have less risk of thermal discomfort.
Asymmetry of radiation temperature
The big difference in thermal radiation from the surface surrounding a person can cause local discomfort or reduce the acceptance of thermal conditions. ASHRAE Standard 55 sets limits on permissible temperature differences between the various surfaces. Because people are more sensitive to some asymmetry than others, for example a warmer palate than the vertical surface of hot and cold, the boundary depends on which surface is involved. The ceiling should not be more than 5 Â ° C (9.0 Â ° F) warmer, while the wall can be warmer to 23 Â ° C (41 Â ° F) compared to other surfaces.
Draft
While air movement can be fun and provide comfort in some circumstances, sometimes undesirable and cause discomfort. This unwanted air movement is called "concept" and most prevalent when the whole body heat sensation is cold. People are most likely to feel the concept of uncovered body parts such as head, neck, shoulders, ankles, feet, and feet, but the sensation also depends on air velocity, air temperature, activity, and clothing.
Vertical air temperature difference
Thermal stratification that produces air temperature at higher head level than the ankle level can cause thermal discomfort. ASHRAE Standard 55 recommends that the difference should not be greater than 3 Ã, Â ° C (5.4 Ã, Â ° F) for sitting occupants or for residents standing 4 Ã, Â ° C (7.2 Ã, Â ° F).
Floor surface temperature
Floors that are too warm or too cold can cause discomfort, depending on footwear. ASHRAE 55 recommends that floor temperatures remain in the range 19-29 Â ° C (66-84 Â ° F) in spaces where residents will wear light shoes.
Adaptive comfort model
The adaptive model is based on the idea that outdoor climate influences indoor comfort because humans can adapt to different temperatures during different times of the year. The adaptive hypothesis predicts that contextual factors, such as having access to environmental control, and past thermal history can influence the expectations and preferences of occupant occupants. Many researchers have conducted field studies around the world where they survey build occupants about their thermal comfort while taking environmental measurements simultaneously. Analyzing the results database of these 160 buildings reveals that residents of naturally ventilated buildings accept and even prefer a wider range of temperatures than their counterparts in closed and air-conditioned buildings because the temperatures they prefer depend on outdoor conditions. These results are included in the ASHRAE 55-2004 standard as adaptive comfort models. The adaptive graph connects the indoor comfort temperature to the applicable outdoor temperature and defines the 80% zone and 90% satisfaction.
ASHRAE-55 2010 Standard introduces the average outer temperatures that apply as input variables for the adaptive model. It is based on the average arithmetic of the average daily outdoor temperature above not less than 7 and not more than 30 consecutive days before the day in question. It can also be calculated by weighting the temperature with different coefficients, assigning an important increase in the latest temperature. In case this weighting is used, there is no need to appreciate the upper limit for the following days. To apply the adaptive model, there should be no mechanical cooling system for space, the occupant must engage in sedentary activity with a metabolic rate of 1-1.3 metric, and the prevailing average temperature greater than 10 ° C (50.0%). Â ° F) and less than 33.5 Â ° C (92.3 Â ° F).
This model applies primarily to naturally-controlled and naturally conditioned spaces, where outdoor climates can really affect indoor and comfortable conditions. In fact, studies by de Dear and Brager show that occupants in naturally ventilated buildings are tolerant of a wider range of temperatures. This is due to behavioral and physiological adjustments, as there are different types of adaptive processes. ASHRAE Standard 55-2010 states that differences in recent thermal experience, clothing change, availability of control options, and shifts in occupant expectations may alter the thermal response of people.
Adaptive models of thermal comfort are implemented in other standards, such as European standards EN 15251 and ISO 7730. While the exact methods and derivation results differ slightly from the adaptive standard of ASHRAE 55, they are essentially the same. The bigger difference is its application. The ASHRAE adaptive standard applies only to buildings without installed mechanical cooling, whereas the EN15251 can be applied to a blend mode building, provided the system is not running.
There are basically three categories of thermal adaptations, namely: behavioral, physiological, and psychological.
Psychological Adaptation
The level of individual comfort in a particular environment can change and adapt over time due to psychological factors. The subjective perception of thermal comfort may be influenced by the memory of previous experiences. Habituation occurs when repeated exposure moderates future expectations, and responses to sensory input. This is an important factor in explaining the difference between field observation and PMV prediction (based on static models) in naturally ventilated buildings. In these buildings, the relationship with outdoor temperatures is twice as strong as expected.
Psychological adaptations are subtly different in static and adaptive models. The static model laboratory test can identify and measure non-heat (psychological) transfer factors that affect reported convenience. The adaptive model is limited to reporting differences (called psychologically) between modeled and reported convenience.
Thermal comfort as a "state of mind" is defined psychologically. Among the factors that affect the state of mind (in the laboratory) is a sense of control over temperature, knowledge of the temperature and appearance (test) of the environment. Thermal test chamber that looks "feels" warmer than what looks like the inside of a refrigerator.
Physiological Adaptation
The body has several thermal adjustment mechanisms to survive in a drastic temperature environment. In a cold environment, the body uses vasoconstriction; which reduces blood flow to the skin, skin temperature and heat dissipation. In a warm environment, vasodilation will increase blood flow to the skin, heat transport, and skin temperature and heat dissipation. If there is an imbalance despite the vasomotor adjustments listed above, in a warm environment, the production of sweat will begin and provide evaporative cooling. If this is not sufficient, hyperthermia will occur, the body temperature can reach 40 Ã, Â ° C (104Ã, Â ° F), and heat stroke may occur. In a cold environment, chills will begin, involuntarily forcing the muscles to work and increasing heat production by a factor of 10. If equilibrium does not recover, hypothermia can occur, which can be fatal. Long-term adjustment for extreme temperatures, several days to six months, may result in cardiovascular and endocrine adjustments. A hot climate can increase blood volume, improve vasodilation effectiveness, improve the performance of the sweat mechanism, and re-adjust the thermal preferences. In cold or hot conditions, vasoconstriction can become permanent, resulting in decreased blood volume and increased body metabolic rate.
Behavioral Adaptation
In a naturally ventilated building, residents take a lot of action to keep themselves comfortable when the condition of the room drifts in the direction of discomfort. Operating windows and fans, adjusting curtains/drapes, changing clothes, and eating food and drink are some common adaptive strategies. Among these, adjusting windows is the most common. Residents who perform such actions tend to feel colder at warmer temperatures than those who do not.
These behavioral actions significantly affect energy input simulations, and researchers develop behavioral models to improve the accuracy of simulated results. For example, there are many window-opening models that have been developed to date, but there is no consensus on the factors that trigger window opening.
Specificity and sensitivity
Individual differences
The thermal sensitivity of an individual is quantified by the descriptor F S , which takes a higher value for individuals with low tolerance to non-ideal thermal conditions. This group includes pregnant women, disabled people, as well as individuals under the age of fourteen or above sixty, who are considered an adult range. The existing literature provides consistent evidence that sensitivity to hot and cold surfaces usually decreases with age. There is also some evidence of a gradual reduction of body effectiveness in a thermo-setting after the age of sixty years. This is mainly due to the slower response of the underlying oppositional mechanisms used to maintain the core body temperature at ideal values. The age prefers warmer temperatures than young adults (76 vs 72 degrees F).
Situational factors include health, psychological, sociological, and vocational activities of people.
Biological gender differences
While the thermal comfort preferences between the sexes seem small, there are some differences. Studies have found men reported discomfort due to temperature rise much earlier than women. Men also estimate a higher level of discomfort than women. One recent study tested men and women in the same cotton dress, performing mental work while using dial dialing to report their thermal comfort to temperature changes. Often, women will prefer a higher temperature. But while women are more sensitive to temperature, males tend to be more sensitive to relative humidity levels.
An extensive field study was conducted in a naturally ventilated residential building in Kota Kinabalu, Sabah, Malaysia. This investigation explored the sex of thermal sensitivity to indoor environments in non-air conditioned residential buildings. Several hierarchical regressions for categorical moderators were selected for data analysis; The results showed that women were slightly more sensitive than men to indoor air temperature, whereas, under thermal neutrality, it was found that both men and women had the same heat sensations.
Regional differences
In many regions of the world, thermal comfort needs can vary by climate. In China the climate has humid summers and cold winters, causing the need for efficient thermal comfort. Energy conservation in relation to thermal comfort has been a major problem in China in recent decades due to rapid economic growth and population. Researchers are now looking for ways to heat and cool buildings in China for lower costs and also with less harm to the environment.
In tropical Brazil, urbanization causes a phenomenon called urban heat island (UHI). This is an urban area that has risen above the thermal comfort limit due to the entry of large people and only down in the comfortable range during the rainy season. Hot urban islands can occur over urban cities or areas built under the right conditions. Urban urban islands are caused by urban areas with few trees and vegetation to block solar radiation or evapotranspiration, many structures with large roof proportions, and low heat-absorbing sidewalks, high levels of carbon dioxide pollution that retain heat released by the surface, a large amount of heat generated by the air conditioning system from solid buildings, and a large amount of car traffic generating heat from the engine and exhaust.
In the hot and humid regions of Saudi Arabia, thermal comfort issues become important in mosques where Muslims go to pray. They are huge open buildings that are only used intermittently (very busy for Friday prayers on Fridays), so it is difficult to give them the proper ventilation. Large size requires large amounts of ventilation, but this requires a lot of energy because the building is only used for a short time. Some mosques have too cold problems from their HVAC systems running too long, and others remain too hot. The effect of the pile also comes into play because of its large size and creates a large layer of hot air above the people in the mosque. The new designs have placed a lower ventilation system in buildings to provide more temperature control at ground level. New monitoring measures are also being taken to improve efficiency.
Thermal stress
The concept of thermal comfort is closely related to thermal stress. It tries to predict the effects of solar radiation, air movement, and humidity for military personnel undergoing training or athletes during a competition event. The value is expressed as the temperature of a wet ball or an index of discomfort. Generally, humans do not work well under heat pressure. The performance of people under heat stress is about 11% lower than their performance in normal thermal wet conditions. In addition, human performance in relation to thermal stress varies greatly by the type of task that individuals complete. Some of the physiological effects of thermal heat pressure include increased blood flow to the skin, sweating, and increased ventilation.
Research
Factors affecting thermal comfort were explored experimentally in the 1970s. Many of these studies lead to the development and refinement of ASHRAE Standard 55 and performed at Kansas State University by Ole Fanger and others. Perceived convenience is found to be a complex interaction of these variables. It was found that the majority of individuals would be satisfied with a set of ideal values. As the value range deviates progressively from the ideal, fewer people are satisfied. These observations can be expressed statistically as percent of individuals who express satisfaction with the comfort condition and predicted predicted mean voting (PMV). This approach is challenged by the adaptive comfort model, developed from the ASHRAE 884 project, which reveals that residents feel comfortable over a wider range of temperatures.
This research is applied to make Building Energy Simulation program (BES) for residential building. Residential buildings in particular can vary considerably more in thermal comfort than public and commercial buildings. This is due to the smaller size, the variety of clothing worn, and the different uses of each room. The main rooms of concern are the bathrooms and bedrooms. The bathroom needs to be at a comfortable temperature for humans with or without clothing. Bedrooms are important because they need to accommodate different levels of clothing and also different metabolic rates of people who fall asleep or awake. Clock discomfort is a common metric used to evaluate the thermal performance of space.
Thermal comfort research in clothing is currently being carried out by the military. New air ventilated clothing is being investigated to improve evaporative cooling in military environments. Some models are manufactured and tested based on the amount of cooling they provide.
In the last twenty years, researchers have also developed sophisticated thermal comfort models that divide the human body into many segments, and predict local thermal discomfort by considering the balance of heat. It has opened a new arena of thermal comfort modeling aimed at heating/cooling selected body parts.
Medical environment
Whenever the referenced study tries to discuss the hot conditions for different groups of occupants in one room, the final study presents only a comparison of thermal comfort satisfaction based on subjective studies. No research has attempted to reconcile the different thermal comfort requirements of different types of occupants who were forced to stay in one room. It therefore seems necessary to investigate the different thermal conditions required by different groups of occupants in the hospital to suit their different needs in this concept. To reconcile the difference in the necessary thermal comfort conditions, it is recommended to test the possibility of using different local beam temperature ranges in one room through the appropriate mechanical system.
Although different studies are conducted on thermal comfort for patients in the hospital, it is also necessary to study the effects of thermal comfort conditions on the quality and quantity of healing for hospital patients. There is also genuine research showing the relationship between thermal comfort for staff and their level of productivity, but no individual-produced research in hospitals in this field. Therefore, research for coverage and individual methods for this subject is recommended. Also research in terms of cooling and heating systems for patients with low levels of immune system protection (such as HIV patients, burn patients, etc.) is recommended. There are important areas, which still need to be focused on including thermal comfort for staff and their relationship to their productivity, using different heating systems to prevent hypothermia in patients and to improve thermal comfort for hospital staff simultaneously.
Finally, the interaction between people, systems and architectural design in hospitals is an area where it requires the further work required to improve the knowledge of how to design buildings and systems to reconcile many conflicting factors for the people who occupy this building.
Personal convenience system
Personal convenience system (PCS) refers to a device or system that heats or cools the occupant of the building in private. This concept is greatly appreciated in contrast to central HVAC systems that have uniform temperature settings for large areas. Personal comfort systems include fans and air diffusers of various types (eg desk fans, nozzles and diffusers slots, overhead fans, low volume high volume fans, etc.) and personalized sources of radiant or conductive heat (boots legs, legwarmers, hot water bottles) etc.). PCS has the potential to meet individual comfort requirements much better than current HVAC systems, because the interpersonal differences in heat sensation due to age, sex, body mass, metabolic rate, clothing and thermal adaptation can amount to a temperature variation equal to 2-5 K, which is impossible for a central, uniform HVAC system to serve. In addition, studies have shown that perceived ability to control one's thermal environment tends to widen the tolerable temperature range. Traditionally, PCS devices have been used separately from each other. However, it has been proposed by Andersen et al. (2016) that PCS device networks produce well-connected thermally transmitted sensors, and report real-time in-house information and respond to program actuation requests (eg parties, conferences, concerts etc.) Can be combined with occupants of conscious building applications to activate new methods to maximize comfort.
See also
References
Further reading
- Thermal Convenience , Fanger, P. O, Denmark Technical Release, 1970 (Reprinted by McGraw-Hill, New York, 1973).
- Thermal Leisure chapter, Basic volume of ASHRAE Handbook , ASHRAE, Inc., Atlanta, GA, 2005.
- Weiss, Hal (1998). The Secret of Warmth: For Comfort or Survival . Seattle, WA: Book Mountain Climber. ISBNÃ, 0-89886-643-X. OCLCÃ, 40999076.
- Godish, T. Indoor Environmental Quality. Boca Raton: CRC Press, 2001.
- Bessoudo, M. Building Facade and Thermal Comfort: Impact of climate, sun shade, and glass on indoor thermal environment. VDM Verlag, 2008
- Nicol, Fergus (2012). adaptive thermal comfort: principles and practices . London New York: Routledge. ISBN: 978-0415691598.
- Humphreys, Michael (2016). Adaptive thermal comfort: foundation and analysis . Abingdon, U.K. New York, NY: Routledge. ISBN: 978-0415691611.
Source of the article : Wikipedia
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