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Cooling Load
Cooling load is the rate at which sensible and latent heat must be removed from the space to maintain a constant space dry-bulb air temperature and humidity. Sensible heat into the space causes its air temperature to rise while latent heat is associated with the rise of the moisture content in the space. The building design, internal equipment, occupants, and outdoor weather conditions may affect the cooling load in a building using different heat transfer mechanisms. The SI units are watts. Overview The cooling load is calculated to select HVAC equipment that has the appropriate cooling capacity to remove heat from the zone. A zone is typically defined as an area with similar heat gains, similar temperature and humidity control requirements, or an enclosed space within a building with the purpose to monitor and control the zone's temperature and humidity with a single sensor e.g. thermostat. Cooling load calculation methodologies take into account heat transfer by conduction, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sensible Heat
Sensible heat is heat exchanged by a body or thermodynamic system in which the exchange of heat changes the temperature of the body or system, and some macroscopic variables of the body or system, but leaves unchanged certain other macroscopic variables of the body or system, such as volume or pressure. Usage The term is used in contrast to a latent heat, which is the amount of heat exchanged that is hidden, meaning it occurs without change of temperature. For example, during a phase change such as the melting of ice, the temperature of the system containing the ice and the liquid is constant until all ice has melted. The terms latent and sensible are correlative. The sensible heat of a thermodynamic process may be calculated as the product of the body's mass (''m'') with its specific heat capacity (''c'') and the change in temperature (\Delta T): : Q_ = m c \Delta T \, . ''Sensible heat'' and ''latent heat'' are not special forms of energy. Rather, they describe exchanges of hea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sol-air Temperature
Sol-air temperature (''T''sol-air) is a variable used to calculate cooling load of a building and determine the total heat gain through exterior surfaces. It is an improvement over: :\frac = h_o(T_o - T_s) Where: * q = rate of heat transfer * A = heat transfer surface area 2* h_o = heat transfer coefficient for radiation (long wave) and convection /m2K* T_o = outdoor surroundings' temperature °C* T_s = outside surface temperature °C The above equation only takes into account the temperature differences and ignores two important parameters, being 1) solar radiative flux; and 2) infrared exchanges from the sky. The concept of ''T''sol-air was thus introduced to enable these parameters to be included within an improved calculation. The following formula results: T_\mathrm = T_o + \frac Where: * a = solar radiation absorptivity (surface solar absorptance or the inverse of the solar reflectance of a material) * I = global solar irradiance (i.e. total solar radiation incident o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heating, Ventilation, And Air Conditioning
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 fresh ai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiant Heating And Cooling Systems
Radiant heating and cooling is a category of HVAC technologies that exchange heat by both convection and radiation with the environments they are designed to heat or cool. There are many subcategories of radiant heating and cooling, including: "radiant ceiling panels",ISO. (2012). ''ISO 11855:2012âBuilding environment design-Design, dimensioning, installation and control of embedded radiant heating and cooling systems''. International Organization for Standardization. "embedded surface systems", "thermally active building systems", and infrared heaters. According to some definitions, a technology is only included in this category if radiation comprises more than 50% of its heat exchange with the environment; therefore technologies such as radiators and chilled beams (which may also involve radiation heat transfer) are usually not considered radiant heating or cooling. Within this category, it is practical to distinguish between high temperature radiant heating (devices with em ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forced-air
A forced-air central heating 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 (vents) to a central air handler for re-heating. The supply plenum directs air from the central unit to the rooms which the system is designed to heat. Regardless of type, all air handlers consist of an air filter, blower, heat exchanger/element/coil, and various controls. Like any other kind of central heating system, thermostats are used to control forced air heating systems. Forced air heating is the type of central heating most commonly installed in North America. It is much less common in Europe, where hydronic heating predominates, especially in the form of hot-water radiators. Types Natural gas/propane/oil/coal/wood *Heat is produced via combustion of fuel. *A heat exchanger ke ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Inertia
In thermodynamics, a material's thermal effusivity, thermal inertia or thermal responsivity is a measure of its ability to exchange thermal energy with its surroundings. It is defined as the square root of the product of the material's thermal conductivity (\lambda) and its volumetric heat capacity (\rho c_p). :e = \sqrt The SI units for thermal effusivity are \sqrt / (), or, equivalently, / ( \sqrt). Thermal effusivity is a parameter that emerges upon applying solutions of the heat equation to heat flow through a thin surface-like region. It becomes particularly useful when the region is selected adjacent to a material's actual surface. Knowing the effusivity and equilibrium temperature of each of two material bodies then enables an estimate of their interface temperature T_m when placed into thermal contact. :T_m = \frac Specialty sensors have also been developed based on this relationship to measure effusivity. Thermal effusivity and thermal diffusivity are related quan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ASHRAE
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE ) is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration (HVAC&R) systems design and construction. ASHRAE has over 57,000 members in more than 132 countries worldwide. ASHRAE's members are composed of building services engineers, architects, mechanical contractors, building owners, equipment manufacturers' employees, and others concerned with the design and construction of HVAC&R systems in buildings. The society funds research projects, offers continuing education programs, and develops and publishes technical standards to improve building services engineering, energy efficiency, indoor air quality, and sustainable development. History ASHRAE was founded in 1894 at a meeting of engineers in New York City, formerly headquartered at 345 East 47th Street, and has held an annual meeting since 1895. Until 1954 it was known as the Ame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy Conversion Efficiency
Energy conversion efficiency (''η'') is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radiation), or heat. The resulting value, ''η'' (eta), ranges between 0 and 1. Overview Energy conversion efficiency depends on the usefulness of the output. All or part of the heat produced from burning a fuel may become rejected waste heat if, for example, work is the desired output from a thermodynamic cycle. Energy converter is an example of an energy transformation. For example, a light bulb falls into the categories energy converter. \eta = \frac Even though the definition includes the notion of usefulness, efficiency is considered a technical or physical term. Goal or mission oriented terms include effectiveness and efficacy. Generally, energy conversion efficiency is a dimensionless number between 0 and 1.0, or 0% to 100%. Ef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plug Load
Plug load is the energy used by products that are powered by means of an ordinary AC plug (e.g., 100, 115, or 230 V). This term generally excludes building energy that is attributed to major end uses (HVAC, lighting, water heating, etc.) Definitions Plug loads are often synonymous with terms such as "receptacle loads", "miscellaneous loads", "unregulated loads", or "process energy/loads." While many building codes/standards haven't defined "plug loads" specifically, they have defined these related terms, which are usually broader energy use categories. "Process energy" is defined as energy consumed in support of a manufacturing, industrial, or commercial process other than conditioning spaces and maintaining comfort and amenities for the occupants of a building. It typically includes office and general miscellaneous equipment, computers, elevators and escalators, kitchen cooking and refrigeration, laundry washing and drying, lighting exempt from the lighting power allowance, and o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lighting Power Density
Lighting Power Density (LPD) is a lighting power requirement defined in North America by the American National Standards Institute (ANSI), American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), and the Illuminating Engineering Society of North America (IESNA) Lighting subcommittee. Lighting Power Density technically represents the load of any lighting equipment in any defined area, or the watts per square foot The square foot (plural square feet; abbreviated sq. ft, sf, or ft2; also denoted by '2) is an imperial unit and U.S. customary unit (non- SI, non-metric) of area, used mainly in the United States and partially in Canada, the United Kingdom, Bang ... of the lighting equipment. However, in the lighting industry it is often associated with the lighting power allowance (LPA) permitted by the building energy code in question. The Oregon Department of Energy defines lighting power density as "The maximum allowable lighting density permitted by th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
European Standard
European Standards (abbreviated EN, from the German name ("European Norm")) are technical standards which have been ratified by one of the three European standards organizations: European Committee for Standardization (CEN), European Committee for Electrotechnical Standardization (CENELEC), or European Telecommunications Standards Institute (ETSI). All ENs are designed and created by all interested parties through a transparent, open, and consensual process. European Standards are a key component of the Single European Market. They are crucial in facilitating trade and have high visibility among manufacturers inside and outside the European territory. A standard represents a model specification, a technical solution against which a market can trade. European Standards must be transposed into a national standard in all EU member states. This guarantees that a manufacturer has easier access to the market of all these European countries when applying European Standards. Member count ... [...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] |
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