HVAC (pronounced either "H-V-A-C" or "aetch-vak") is an acronym Acronyms and initialisms are abbreviations that are formed using the initial components in a phrase or name. These components may be individual letters or parts of words (as in Benelux). There is no universal agreement on the precise definition of the various terms (see nomenclature), nor on written usage (see orthographic styling). While popular that stands for the closely related functions of "Heating A heater is any object that emits heat or causes another body to achieve a higher temperature. In a household or domestic setting, heaters are usually appliances whose purpose is to generate heating . Heaters exists for all states of matter, including solids, liquids and gases, Ventilating Ventilating is the process of "changing" or replacing air in any space to provide high Indoor air quality. i.e. to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen. Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to, and Air Conditioning Air conditioning is the cooling 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. An air conditioner is an appliance, system, or machine designed to stabilise the air temperature and humidity within an area (used for cooling as" - the technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the design, production, and operation of machines and, based on the principles of thermodynamics In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure, fluid mechanics Fluid mechanics is the study of fluids and the forces on them. Fluid mechanics can be divided into fluid statics, the study of fluids at rest, and fluid dynamics, the study of fluids in motion. It is a branch of continuum mechanics, a subject which models matter without using the information that it is made out of atoms. Fluid mechanics,, and heat transfer Heat transfer is the transition of thermal energy from a hotter mass to a cooler mass. When an object is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat transfer, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium; this means that. Refrigeration Refrigeration is the process of removing heat from an enclosed space, or from a substance, and moving it to a place where it is unobjectionable. The primary purpose of refrigeration is lowering the temperature of the enclosed space or substance and then maintaining that lower temperature. The term cooling refers generally to any natural or is sometimes added to the field's abbreviation as HVAC&R or HVACR, or ventilating is dropped as in HACR (such as the designation of HACR-rated circuit breakers A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a).
HVAC is particularly important in the design of medium to large industrial and office buildings such as skyscrapers A skyscraper is a tall, continuously habitable building. There is no official definition or height above which a building may clearly be classified as a skyscraper. Most cities define the term empirically; even a building of 80 meters may be considered a skyscraper if it protrudes above its built environment and changes the overall skyline.[ and in marine environments such as aquariums An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants. The term combines the Latin root aqua, meaning water, with the suffix -arium, meaning "a place for relating to&, where safe and healthy building Sick building syndrome is a combination of ailments (a syndrome) associated with an individual's place of work (office building) or residence. A 1984 World Health Organization report into the syndrome suggested up to 30% of new and remodeled buildings worldwide may be linked to symptoms of SBS. Most of the sick building syndrome is related to poor conditions are regulated with temperature and humidity, as well as "fresh air" from outdoors.
Contents |
Background
The invention of the components of HVAC systems went hand-in-hand with the industrial revolution The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transport and technology had a profound effect on the socioeconomic and cultural conditions starting in the United Kingdom, then subsequently spreading throughout Europe, North America, and eventually the world. The, and new methods of modernization, higher efficiency, and system control are constantly introduced by companies and inventors all over the world. The three central functions of heating, ventilating, and air-conditioning are interrelated, providing thermal comfort Human thermal comfort is defined by ASHRAE as the state of mind that expresses satisfaction with the surrounding environment . Maintaining thermal comfort for occupants of buildings or other enclosures is one of the important goals of HVAC design engineers, acceptable indoor air quality Indoor air quality is a term referring to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants, within reasonable installation, operation, and maintenance costs. HVAC systems can provide ventilation Ventilating is the process of "changing" or replacing air in any space to provide high Indoor air quality. i.e. to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen. Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to, reduce air infiltration Infiltration is the unintentional or accidental introduction of outside air into a building, typically through cracks in the building envelope and through use of doors for passage. Infiltration is sometimes called air leakage. The leakage of room air out of a building, intentionally or not, is called exfiltration. Infiltration is caused by wind,, and maintain pressure relationships between spaces. How air is delivered to, and removed from spaces is known as room air distribution Characterizing how air is introduced to, flows through, and is removed from spaces is called room air distribution. HVAC airflow in spaces generally can be classified by two different types: mixing and displacement.[1]
In modern buildings the design, installation, and control systems There are two common classes of control systems, with many variations and combinations: logic or sequential controls, and feedback or linear controls. There is also fuzzy logic, which attempts to combine some of the design simplicity of logic with the utility of linear control. Some devices or systems are inherently not controllable of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally "size" and select HVAC systems and equipment. For larger buildings, building services designers and engineers An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality, safety and cost. The word engineer is derived from, such as mechanical, architectural Architectural engineering, also known as Building engineering, is the application of engineering principles and technology to building design and construction. Definitions of an architectural engineer may refer to:, or building services Architectural engineering, also known as Building engineering, is the application of engineering principles and technology to building design and construction. Definitions of an architectural engineer may refer to: engineers analyze, design, and specify the HVAC systems, and specialty mechanical contractors build and commission them. Building permits and code-compliance inspections of the installations are normally required for all sizes of buildings.[citation needed]
The HVAC industry is a worldwide enterprise, with career opportunities including operation and maintenance, system design and construction, equipment manufacturing and sales, and in education and research. The HVAC industry had been historically regulated by the manufacturers of HVAC equipment, but Regulating and Standards organizations such as HARDI HARDI, or Heating, Airconditioning & Refrigeration Distributors International, is a not for profit association whose focus is to promote the business interests of wholesale air-conditioning, heating, and refrigeration companies. HARDI's member companies are estimated to represent about 80% of the industry's wholesale sales- over $20 billion, ASHRAE The American Society of Heating, Refrigerating and Air Conditioning Engineers is an international technical society for all individuals and organizations interested in heating, ventilation, air-conditioning, and refrigeration (HVAC&R). The Society, organized into Regions, Chapters, and Student Branches, allows exchange of HVAC&R knowledge, SMACNA The Sheet Metal and Air Conditioning Contractors' National Association is an international association of HVAC contractors. Its headquarters is at 4201 Lafayette Center Drive Chantilly, Virginia 20151-1209, and it has about 2,000 members and 98 chapters in the United States, Canada, Brazil, and Australia, ACCA, Uniform Mechanical Code Designated as an American National Standard, the Uniform Mechanical Code is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation and inspection of mechanical (HVAC, combustion, exhaust, refrigeration) systems as a means of promoting the public's health, safety and welfare, International Mechanical Code The International Building Code is a model building code developed by the International Code Council (ICC). It has been adopted throughout most of the United States, and AMCA The Amateur Motorcycle Association is a non-profit making governing body for off road motorcycling sport in the United Kingdom. Based in Cannock, Staffordshire, the organisation has over 200 affiliate clubs, catering for motocross, trials, enduro and historical motocross have been established to support the industry and encourage high standards and achievement.
Heating
Main article: Central heating A central heating system provides warmth to the whole interior of a building from one point to multiple rooms. When combined with other systems in order to control the building climate, the whole system may be a HVAC (heating, ventilation and air conditioning) systemThere are many different types of standard heating systems. Central heating A central heating system provides warmth to the whole interior of a building from one point to multiple rooms. When combined with other systems in order to control the building climate, the whole system may be a HVAC (heating, ventilation and air conditioning) system is often used in cold climates to heat private houses and public buildings. Such a system contains a boiler A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, furnace A furnace is a device used for heating. The name derives from Latin fornax, oven. The earliest furnace was excavated at Balakot, a site of the Indus Valley Civilization, dating back to its mature phase . The furnace was most likely used for the manufacturing of ceramic objects, or heat pump A heat pump is a machine or device that moves heat from one location at a lower temperature to another location (the 'sink' or 'heat sink') at a higher temperature using mechanical work or a high-temperature heat source. The difference between a heat pump and a normal air conditioner is that a heat pump can be used to heat a home as well as cool to heat water, steam, or air, all in a central location such as a furnace room A furnace room is a room for locating the furnace and auxiliary equipment. Such a room minimizes the visual impact of the furnace, pipes and other gear. A modern compact furnace can readily fit into a small closet. However care must be exercised to provide adequate ventilation as the exterior of the furnace unit puts out a significant amount of in a home or a mechanical room A mechanical room or a boiler room is a room or space in a building dedicated to the mechanical equipment and its associated electrical equipment. Unless a building is served by a centralized heating plant, the size of the mechanical room is usually proportional to the size of the building. A small building or home may have at most a utility room in a large building. The use of water as the heat transfer medium is known as hydronics Hydronics is the use of water as the heat-transfer medium in heating and cooling systems. Some of the oldest and most common examples are steam and hot-water radiators. Historically, in large-scale commercial buildings such as high-rise and campus facilities, a hydronic system may include both a chilled and a heated water loop, to provide for both. The system also contains either ductwork, for forced air systems, or piping to distribute a heated fluid and radiators Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating to transfer this heat to the air. The term radiator in this context is misleading since most heat transfer from the heat exchanger is by convection Convection is the movement of molecules within fluids . It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids, not radiation Thermal radiation is electromagnetic radiation emitted from a material which is due to the heat of the material, the characteristics of which depend on its temperature. An example of thermal radiation is the infrared radiation emitted by a common household radiator or electric heater. A person near a raging bonfire will feel the radiated heat of. The radiators may be mounted on walls or buried in the floor to give under-floor heat.
In boiler fed or radiant heating systems, all but the simplest systems have a pump to circulate the water and ensure an equal supply of heat to all the radiators. The heated water can also be fed through another (secondary) heat exchanger inside a storage cylinder to provide hot running water.
Forced air systems A forced-air system is one which uses air as its heat transfer medium. These systems rely on ductwork, vents, and plenums as means of air distribution, separate from the actual heating and air conditioning systems. The return plenum carries the air from several large return grills to a central air handler for re-heating. The supply plenum directs send heated air through ductwork Ducts are used in heating, ventilation, and air conditioning to deliver and remove air. These needed airflows include, for example, supply air, return air, and exhaust air. Ducts also deliver, most commonly as part of the supply air, ventilation air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal. During warm weather the same ductwork can be used for air conditioning. The forced air can also be filtered or put through air cleaners.
Heating can also be provided from electric, or resistance heating A heater is any object that emits heat or causes another body to achieve a higher temperature. In a household or domestic setting, heaters are usually appliances whose purpose is to generate heating . Heaters exists for all states of matter, including solids, liquids and gases using a filament that becomes hot when electric current is caused to pass through it. This type of heat can be found in electric baseboard heaters, portable electric heaters, and as backup or supplemental heating for heat pump (or reverse heating) system.
The heating elements (radiators or vents) should be located in the coldest part of the room, typically next to the windows to minimize condensation and offset the convective air current formed in the room due to the air next to the window becoming negatively buoyant due to the cold glass. Devices that direct vents away from windows to prevent "wasted" heat defeat this design intent. Cold air drafts can contribute significantly to subjectively feeling colder than the average room temperature. Therefore, it is important to control the air leaks from outside in addition to proper design of the heating system.
The invention of central heating is often credited to the ancient Romans The Roman Empire was the post-Republican phase of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean. The term is used to describe the Roman state during and after the time of the first emperor, Augustus, who installed a system of air ducts called a hypocaust A hypocaust was an ancient Roman system of central heating / underfloor heating. The word literally means "heat from below", from the Greek hypo meaning below or underneath, and kaiein, to burn or light a fire. They are traditionally considered to have been invented by Sergius Orata, though this is not fully confirmed in the walls and floors of public baths and private villas. [2]
Ventilating
Main article: Ventilation (architecture) Ventilating is the process of "changing" or replacing air in any space to provide high Indoor air quality. i.e. to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen. Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to An air handling unit An air handler, or air handling unit , is a device used to condition and circulate air as part of a heating, ventilating, and air-conditioning (HVAC) system. Usually, an air handler is a large metal box containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to is used for the heating and cooling of air in a central location (click on image for legend).Ventilating Ventilating is the process of "changing" or replacing air in any space to provide high Indoor air quality. i.e. to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen. Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to is the process of "changing" or replacing air in any space to control temperature or remove moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and to replenish oxygen. Ventilation includes both the exchange of air to the outside as well as circulation of air within the building. It is one of the most important factors for maintaining acceptable indoor air quality Indoor air quality is a term referring to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants in buildings. Methods for ventilating a building may be divided into mechanical/forced and natural types.[3] Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to keep interior building air circulating, and to prevent stagnation of the interior air.
Mechanical or forced ventilation
"Mechanical" or "forced" ventilation is used to control indoor air quality Indoor air quality is a term referring to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. Excess humidity, odors, and contaminants can often be controlled via dilution or replacement with outside air. However, in humid climates much energy is required to remove excess moisture from ventilation air.
Kitchens and bathrooms typically have mechanical exhaust to control odors and sometimes humidity. Factors in the design of such systems include the flow rate (which is a function of the fan speed and exhaust vent size) and noise level. If ducting for the fans traverse unheated space (e.g., an attic), the ducting should be insulated as well to prevent condensation on the ducting. Direct drive fans are available for many applications, and can reduce maintenance needs.
Ceiling fans and table/floor fans circulate air within a room for the purpose of reducing the perceived temperature because of evaporation of perspiration on the skin of the occupants. Because hot air rises, ceiling fans may be used to keep a room warmer in the winter by circulating the warm stratified air from the ceiling to the floor. Ceiling fans do not provide ventilation as defined as the introduction of outside air.
Natural ventilation
Natural ventilation is the ventilation of a building with outside air without the use of a fan or other mechanical system. It can be achieved with openable windows or trickle vents when the spaces to ventilate are small and the architecture permits. In more complex systems warm air in the building can be allowed to rise and flow out upper openings to the outside (stack effect) thus forcing cool outside air to be drawn into the building naturally through openings in the lower areas. These systems use very little energy but care must be taken to ensure the occupants' comfort. In warm or humid months, in many climates, maintaining thermal comfort solely via natural ventilation may not be possible so conventional air conditioning systems are used as backups. Air-side economizers perform the same function as natural ventilation, but use mechanical systems' fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate.
|
Fri, 13 Aug 2010 16:19:30 GMT+00:00
Examiner.com Climate control costs are known. The benefits are unknown. Subscribe free to this Ecopolitics column by clicking the [+ Subscribe] blue box below the title ...
![Fulbright Scholar headed to Nepal [HQ]](/q8-FqdcFrFBYLvlkJdOaSRu8kwJLmts0-s0-q8-UTVF17-ARq8-YU17-516Jq8-TNGV17-6q8-FZGRFSSB17-S67100S69Q818951q8-QVGARGABP17-FFIq8-CCNs8-7ERIERfYVNAOZHUgs7-ZBPr7-5GITr7-8-out.jpg)
Sun, 03 Jan 2010 02:39:40 PST
Dr. John All has received a Fulbright scholarship to study and teach about climate control in Nepal. ... facebook.com.
