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Room Air Distribution
Room air distribution is characterizing how air is introduced to, flows through, and is removed from spaces. HVAC airflow in spaces generally can be classified by two different types: ''mixing'' (or dilution) and ''displacement''. Mixing systems Mixing systems generally supply air such that the supply air mixes with the room air so that the mixed air is at the room design temperature and humidity. In cooling mode, the cool supply air, typically around 55 °F (13 °C) (saturated) at design conditions, exits an outlet at high velocity. The high-velocity supply air stream causes turbulence causing the room air to mix with the supply air. Because the entire room is near-fully mixed, temperature variations are small while the contaminant concentration is fairly uniform throughout the entire room. Diffusers are normally used as the air outlets to create the high-velocity supply air stream. Most often, the air outlets and inlets are placed in the ceiling. Supply diffusers in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASHRAE Handbook
The ASHRAE Handbook is the four-volume flagship publication of the nonprofit technical organization ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers). This Handbook is considered the most comprehensive and authoritative repository of practical knowledge on the various topics that form the field of heating, ventilation, air-conditioning, and refrigeration ( HVAC&R). The four volumes are ''Fundamentals'', ''Refrigeration'', ''HVAC Applications'' ("Applications"), and ''HVAC Systems and Equipment'' ("Systems and Equipment"). Members of ASHRAE receive the current volume, in both print and CD-ROM form, each year as a basic membership benefit. An enhanced electronic version, known as ''ASHRAE Handbook Online'' is a web-based version updated annually that contains the four latest volumes as well as extra content such as calculations, demonstration videos, and spreadsheets. The various versions of the Handbook are typically available to the public via ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dilution (equation)
Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to the solution. To dilute a solution means to add more solvent without the addition of more solute. The resulting solution is thoroughly mixed so as to ensure that all parts of the solution are identical. The same direct relationship applies to gases and vapors diluted in air for example. Although, thorough mixing of gases and vapors may not be as easily accomplished. For example, if there are 10 grams of salt (the solute) dissolved in 1 litre of water (the solvent), this solution has a certain salt concentration (molarity). If one adds 1 litre of water to this solution, the salt concentration is reduced. The diluted solution still contains 10 grams of salt (0.171 moles of NaCl). Mathematically this relationship can be shown by equation: : c_1V_1 = c_2V_2 where *''c''1 = initial concentration or molarity *''V''1 = initi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMACNA
The Sheet Metal and Air Conditioning Contractors' National Association (SMACNA; pronounced 'Smack'-'Nah') is an international trade association with more than 4,500 contributing contractor members in 103 chapters throughout the United States, Canada, Australia and Brazil. Its headquarters is in Chantilly, Virginia. Member profile SMACNA members perform work in industrial, commercial, institutional and residential markets. They specialize in heating, ventilation and air conditioning (HVAC); architectural sheet metal; industrial sheet metal; kitchen equipment; specialty stainless steel work; manufacturing; siding and decking; testing and balancing; service; and energy management and maintenance. Technical manuals and standards The voluntary technical standards and manuals developed by SMACNA Contractors have found worldwide acceptance by the construction and design community, as well as local, national, and foreign government agencies. ANSI, the American National Standards Instit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Conditioning
Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling the humidity of internal air. Air conditioning can be achieved using a mechanical 'air conditioner' or alternatively a variety of other methods, including passive cooling or ventilative cooling. Air conditioning is a member of a family of systems and techniques that provide heating, ventilation, and air conditioning (HVAC). Heat pumps are similar in many ways to air conditioners, but use a reversing valve to allow them to both heat and also cool an enclosed space. Air conditioners, which typically use vapor-compression refrigeration, range in size from small units used within vehicles or single rooms to massive units that can cool large buildings. Air source heat pumps, which can be used for heating as well as cooling, are becoming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Comfort
Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC ( heating, ventilation, and air conditioning) design engineers. Thermal neutrality is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indoor Air Quality
Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduced productivity, and impaired learning in schools. Common pollutants of indoor air include: Secondhand tobacco smoke, air pollutants from indoor combustion, radon, molds and other allergens, carbon monoxide, volatile organic compounds, legionella and other bacteria, asbestos fibers, carbon dioxide, ozone and particulates. Source control, filtration, and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality in most buildings. Determination of IAQ involves the collection of air samples, monitoring human exposure to pollutants, collection of samples on building surfaces, and computer modelling of air flow inside buildings. IAQ is part of indoor environmental quality (IEQ), which include ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underfloor Air Distribution
Underfloor air distribution (UFAD) is an air distribution strategy for providing ventilation and space conditioning in buildings as part of the design of a HVAC system. UFAD systems use an underfloor supply plenum located between the structural concrete slab and a raised floor system to supply conditioned air to supply outlets (usually floor diffusers), located at or near floor level within the occupied space. Air returns from the room at ceiling level or the maximum allowable height above the occupied zone. The UFAD system takes advantage of the thermal plume and stratification phenomenon: the conditioned air is supplied directly to the occupied zone (OZ). The thermal plumes generated by the occupants and other heat sources introduce the conditioned air to absorb the heat and humidity and then bring the contaminated air to the upper zone (UZ). At a certain plane in the room, the airflow rate returned to the UZ is equal to the supply air. The plane divides the room into OZ and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duct (HVAC)
Ducts are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The needed airflows include, for example, ''supply air'', ''return air'', and ''exhaust air''. Ducts commonly also deliver '' ventilation air'' as part of the supply air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort. A duct system is also called ''ductwork''. Planning (laying out), sizing, optimizing, detailing, and finding the pressure losses through a duct system is called ''duct design''. Materials Ducts can be made out of the following materials: Galvanized steel Galvanized mild steel is the standard and most common material used in fabricating ductwork because the zinc coating of this metal prevents rusting and avoids cost of painting. For insulation purposes, metal ducts are typically lined with faced fiberglass blankets (duct liner) or wrapped externally with fiberglass blankets (duct wrap). When ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grille (architecture)
A grille or grill (French word from Latin ''craticula'', small grill) is an opening of several slits side-by-side in a wall, metal sheet or another barrier, usually to allow air or water to enter and/or leave and prevent larger objects (such as animals) from going in or out. A similar definition is "a French term for an enclosure in either iron or bronze." Register vs. grille In heating, cooling, ventilation, or a combination thereof, a grille is a perforated cover for an air duct. Grilles sometimes have louvers which allow the flow of air to be directed. A register differs from a grille in that a damper is included. However, in practice, the terms "grille", "register", and "return" are often used interchangeably, and care must be taken to determine the meaning of the term used. Grillwork Grillwork is decorative grating of metal, wood, stone, or other material used as a screen, divider, barrier, or as a purely decorative element. It may function as a window, either w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HVAC
Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. " Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR (as in the designation of HACR-rated circuit breakers). HVAC is an important part of residential structures such as single family homes, apartment buildings, hotels, and senior living facilities; medium to large industrial and office buildings such as skyscrapers and hospitals; vehicles such as cars, trains, airplanes, ships and submarines; and in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fres ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indoor Air Quality
Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduced productivity, and impaired learning in schools. Common pollutants of indoor air include: Secondhand tobacco smoke, air pollutants from indoor combustion, radon, molds and other allergens, carbon monoxide, volatile organic compounds, legionella and other bacteria, asbestos fibers, carbon dioxide, ozone and particulates. Source control, filtration, and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality in most buildings. Determination of IAQ involves the collection of air samples, monitoring human exposure to pollutants, collection of samples on building surfaces, and computer modelling of air flow inside buildings. IAQ is part of indoor environmental quality (IEQ), which include ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Comfort
Thermal comfort is the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation ( ANSI/ASHRAE Standard 55).ANSI/ASHRAE Standard 55-2017, Thermal Environmental Conditions for Human Occupancy The human body can be viewed as a heat engine where food is the input energy. The human body will release excess heat into the environment, so the body can continue to operate. The heat transfer is proportional to temperature difference. In cold environments, the body loses more heat to the environment and in hot environments the body does not release enough heat. Both the hot and cold scenarios lead to discomfort. Maintaining this standard of thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC ( heating, ventilation, and air conditioning) design engineers. Thermal neutrality is maintained when the heat generated by human metabolism is allowed to dissipate, thus maintaining thermal equil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
