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Dedicated Outdoor Air System
A dedicated outdoor air system (DOAS) is a type of heating, ventilation and air-conditioning (HVAC) system that consists of two parallel systems: a dedicated system for delivering outdoor air ventilation that handles both the latent and sensible loads of conditioning the ventilation air, and a parallel system to handle the (mostly sensible heat) loads generated by indoor/process sources and those that pass through the building enclosure. Background Traditional HVAC systems, such as variable air volume (VAV) systems serving multiple zones, have potential problems in terms of poor thermal comfort and possible microbial contamination. Depending on the environment and the parallel system involved, in a DOAS setup the outdoor air system will handle some of the sensible load in addition to the latent load, and the parallel system will handle the remaining sensible load. The main point of a DOAS system is to provide dedicated ventilation rather than ventilation as an incidental part of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DOAS System Installed At Green Building In India
doas (“dedicated openbsd application subexecutor”) is a program to execute commands as another user. The system administrator can configure it to give specified users privileges to execute specified commands. It is free and open-source under the ISC license and available in Unix and Unix-like operating systems. doas was developed by Ted Unangst for OpenBSD as a simpler and safer sudo replacement. Unangst himself had issues with the default ''sudo'' config, which was his motivation to develop doas. doas was originally developed by Ted Unangst and was released with OpenBSD 5.8 in October 2015 replacing sudo. However, OpenBSD still provides sudo as a package. Configuration Definition of privileges should be written in the configuration file, /etc/doas.conf. The syntax used in the configuration file is inspired by the packet filter configuration file. Examples Allow user1 to execute procmap as root without password: permit nopass user1 as root cmd /usr/sbin/procmap Allow mem ... [...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] |
Dew Point
The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will condense to form liquid water known as dew. When this occurs via contact with a colder surface, dew will form on that surface. The dew point is affected by humidity. When there is more moisture in the air, the dew point is higher. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed via deposition rather than condensation. In liquids, the analog to the dew point is the cloud point. Humidity If all the other factors influencing humidity remain constant, at ground level the relative humidity rises as the temperature falls; this is because less vapor is needed to saturate the air. In normal conditions, the dew point temperature will not be greater than the air temperatu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dry-bulb Temperature
The dry-bulb temperature (DBT) is the temperature of air measured by a thermometer freely exposed to the air, but shielded from radiation and moisture. DBT is the temperature that is usually thought of as air temperature, and it is the true thermodynamic temperature. It indicates the amount of heat in the air and is directly proportional to the mean kinetic energy of the air molecules. Temperature is usually measured in degrees Celsius (°C), kelvins (K), or degrees Fahrenheit (°F). Unlike wet-bulb temperature, dry bulb temperature does not indicate the amount of moisture in the air. In construction, it is an important consideration when designing a building for a certain climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologica .... Nall called it one of "the most important ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fire Suppression
Wildfire suppression is a range of firefighting tactics used to suppress wildfires. Firefighting efforts in wild land areas require different techniques, equipment, and training from the more familiar structure fire fighting found in populated areas. Working in conjunction with specially designed aerial firefighting aircraft, these wildfire-trained crews suppress flames, construct fire lines, and extinguish flames and areas of heat to protect resources and natural wilderness. Wildfire suppression also addresses the issues of the wildland–urban interface, where populated areas border with wild land areas. In the United States and other countries, aggressive wildfire suppression aimed at minimizing fire has contributed to accumulation of fuel loads, increasing the risk of large, catastrophic fires. History Australia Wildland fire, known in Australia as bush fire, has played a major role in Australia due to arid conditions. Notable fire services tasked with wildfire suppressio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dehumidification
A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons, or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses. Typical air conditioning systems combine dehumidification with cooling, by operating cooling coils below the dewpoint and draining away the water that condenses. Overview Dehumidifiers extract water from air that passes through the unit. There are two common types of dehumidifiers: condensate dehumidifiers and desiccant dehumidifiers, and there are also other emerging designs. Condensate dehumidifiers use a refrigeration cycle to collect water known as condensate, which is normally considered to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chilled Beam
A chilled beam is a type of radiation/convection HVAC system designed to heat and cool large buildings through the use of water. This method removes most of the zone sensible local heat gains and allows the flow rate of pre-conditioned air from the air handling unit to be reduced, lowering by 60% to 80% the ducted design airflow rate and the equipment capacity requirements. There are two types of chilled beams, a Passive Chilled Beam (PCB) and an Active Chilled Beam (ACB). They both consist of pipes of water (fin-and-tube) that pass through a heat exchanger contained in a case suspended from, or recessed in, the ceiling.Price, 2011, ''Engineer's HVAC Handbook'', p. 1067, ''2012 ASHRAE Handbook HVAC Systems and Equipment'', ASHRAE, 2012, p. 20.9, As the beam cools the air around it, the air becomes denser and falls to the floor. It is replaced by warmer air moving up from below, causing a constant passive air movement called convection, to cool the room.Hamilton and Watkins, 2009, p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leadership In Energy And Environmental Design
Leadership in Energy and Environmental Design (LEED) is a green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council (USGBC), it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighborhoods, which aims to help building owners and operators be environmentally responsible and use resources efficiently. By 2015, there were over 80,000 LEED-certified buildings and over 100,000 LEED-accredited professionals. Most LEED-certified buildings are located in major U.S. metropolises. LEED Canada has developed a separate rating system adapted to the Canadian climate and regulations. Some U.S. federal agencies, state and local governments require or reward LEED certification. This can include tax credits, zoning allowances, reduced fees, and expedited permitting. Studies have found that for-rent LEED office spaces generally have higher rents and occupancy rates an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fan Coil Unit
A fan coil unit (FCU), also known as a Vertical Fan Coil-Unit (VFC), is a device consisting of a heat exchanger (coil) and a fan. As part of an HVAC system found in residential, commercial, and industrial buildings using ducted split air conditioning or with central plant cooling, a fan coil unit is often connected to ductwork and a thermostat to regulate the temperature of one or more spaces as well as assisting the main air handling unit for each space if used with chillers. The thermostat controls the fan speed and/or the throughput of water to the heat exchanger using a control valve. Owing to their simplicity and flexibility, fan coil units can be more economical to install than ducted 100% fresh air systems (VAV) or central heating systems with air handling units or chilled beams. Various unit configurations are available, including horizontal (ceiling mounted) or vertical (floor mounted). Noise output from FCUs, like any other form of air conditioning, is princip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Pumps
A heat pump is a device that can heat a building (or part of a building) by transferring thermal energy from the outside using a refrigeration cycle. Many heat pumps can also operate in the opposite direction, cooling the building by removing heat from the enclosed space and rejecting it outside. Units that only provide cooling are called air conditioners. When in heating mode, a refrigerant at outside temperature is being compressed. As a result, the refrigerant becomes hot. This thermal energy can be transferred to an indoor unit. After being moved outdoors again, the refrigerant is decompressed — evaporated. It has lost some of its thermal energy and returns colder than the environment. It can now take up the surrounding energy from the air or from the ground before the process repeats. Compressors, fans, and pumps run with electric energy. Common types are air-source heat pumps, ground-source heat pumps, water-source heat pumps and exhaust air heat pumps. They are al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiant Cooling
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 11855:2012—Building 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 emi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Standard Cubic Feet Per Minute
Standard cubic feet per minute (SCFM) is the molar flow rate of a gas expressed as a volumetric flow at a "standardized" temperature and pressure thus representing a fixed number of moles of gas regardless of composition and actual flow conditions. It is related to the mass flow rate of the gas by a multiplicative constant which depends only on the molecular weight of the gas. There are different standard conditions for temperature and pressure, so care is taken when choosing a particular standard value. Worldwide, the "standard" condition for pressure is variously defined as an absolute pressure of 101,325 pascals (Atmospheric pressure), 1.0 bar (i.e., 100,000 pascals), 14.73 psia, or 14.696 psia and the "standard" temperature is variously defined as 68 °F, 60 °F, 0 °C, 15 °C, 20 °C, or 25 °C. The relative humidity (e.g., 36% or 0%) is also included in some definitions of standard conditions. In Europe, the standard temperature is mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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