Disclaimer: If you need a custom written term, thesis or research paper as well as an essay or dissertation sample, choosing Online Essay Help - a relatively cheap custom writing service - is a great option. Get any needed writing assistance at a price that every average student can afford A dome (from Latin: domus) is an architectural element similar to the hollow upper half of a sphere; there is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a blogger.com precise definition of a dome has been a matter of controversy and there are a wide variety of forms and specialized terms to describe them Radiant heating is a technology for heating indoor and outdoor areas. Heating by radiant energy is observed every day, the warmth of the sunshine being the most commonly observed example. Radiant heating as a technology is more narrowly defined. It is the method of intentionally using the principles of radiant heat to transfer radiant energy from an emitting heat source to an object
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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", [1] "embedded surface systems", [1] "thermally active building systems", [1] and infrared heaters. This article mainly addresses radiant heating and cooling with moderate source temperatures, phd thesis concrete slabs, used to heat or cool indoor environments.
Moderate temperature radiant heating and cooling is usually composed of relatively large surfaces that are internally heated or cooled using hydronic or electrical sources. For high temperature indoor or outdoor radiant heating, see: Infrared heater. For snow melt applications see: Snowmelt system, phd thesis concrete slabs. Radiant heating is a technology for heating indoor and outdoor areas, phd thesis concrete slabs.
Heating by radiant energy is observed every day, the warmth of the sunshine being the most commonly observed example. Radiant heating as a technology is more narrowly defined. It is the method of intentionally using the principles of radiant heat to transfer radiant energy from an emitting heat source to an object. Designs with radiant heating are seen as replacements for conventional convection heating as well as a way of supplying confined outdoor heating.
Radiant heating heats a building through radiant heat phd thesis concrete slabs, rather than conventional methods such as radiators mostly convection heating.
Mixed radiation, convection and conduction systems have existed since the Roman use of hypocaust heating. The internal air temperature for radiant heated buildings may be lower than for a conventionally heated building to achieve the same level of body comfort, when adjusted so the perceived temperature is actually the same. One of the key advantages of radiant heating systems is a much decreased circulation of air inside the room and the corresponding spreading of airborne particles.
Underfloor and wall heating systems often are called low-temperature systems. Since their heating surface is much larger than other systems, a much lower temperature is required to achieve the same level of heat transfer.
This provides an improved room climate with healthier humidity levels. The maximum temperature of the heating surface can vary from 29—35 °C 84—95 °F depending on the room type. Radiant overhead panels are mostly used in production and warehousing facilities or sports centers; they hang a few meters above the floor and their surface temperatures are much higher.
In the case of heating outdoor areas, phd thesis concrete slabs, the surrounding air is constantly moving. Relying on convection heating is in most cases impractical, the reason being that, once you heat the outside air, it will blow away with air movement.
Even in a no-wind condition, the buoyancy effects will carry away the hot air. Outdoor radiant heaters allow specific spaces within an outdoor area to be targeted, warming only the people and objects in their path. Radiant heating systems may be gas-fired or use electric infrared heating elements. An example of the overhead radiant heaters are the patio heaters often used with outdoor serving. The top metal disc reflects the radiant heat onto a small area, phd thesis concrete slabs.
Radiant cooling is the use of cooled surfaces to remove sensible heat primarily by thermal radiation and only secondarily by other methods like convection. There is a separate system to provide air for ventilationdehumidificationand potentially additionally cooling, phd thesis concrete slabs. Since the majority of the cooling process results from removing sensible heat through radiant exchange with people and objects and not air, occupant thermal comfort can be achieved with warmer interior air temperatures than with air based cooling systems.
Radiant cooling systems potentially offer reductions in cooling energy consumption. Radiant cooling may also be integrated with other energy-efficient strategies such as night time flushing, indirect evaporative coolingor ground source heat pumps as it requires a small difference in temperature between desired indoor air temperature and the cooled surface.
Fluorescent radiant cooling uses a coating that fluoresces in the infrared atmospheric windowa frequency range where the atmosphere is unusually transparent, so that the energy goes straight out to space, phd thesis concrete slabs. This can cool the heat-fluorescent object to below ambient air temperature, even in full sun. Early radiant cooling systems were installed in the late s and s in Europe [13] and by the s in the US, phd thesis concrete slabs.
Radiant cooling systems offer lower energy consumption than conventional cooling systems based on research conducted by the Lawrence Berkeley National Laboratory. While this research is informative, more research needs to be done to account for the limitations of simulation tools and integrated system approaches. Much of the energy savings is also attributed to the lower amount of energy required to pump water as opposed to distribute air with fans, phd thesis concrete slabs.
By coupling the system with building mass, radiant cooling can shift some cooling to off-peak night time hours, phd thesis concrete slabs. Radiant cooling appears to have lower first costs [16] and lifecycle costs compared to conventional systems. Lower first costs are largely attributed to integration with structure and design elements, while lower life cycle costs result from decreased maintenance.
Because of the potential for condensate formation on the cold radiant surface resulting in water damage, mold and the likeradiant cooling systems have not been widely applied. Condensation caused by humidity is a limiting factor for the cooling capacity of a radiant cooling system. The surface temperature should not be equal or below the dew point temperature in the space. An air temperature of 26 °C 79 °F would mean a dew point between 17 °C and 20 °C 63 °F and 68 °F.
While there are a broad range of system technologies, there are two primary types of radiant cooling systems. The first type is systems that deliver cooling through the building structure, usually slabs. These systems are also named thermally activated building systems TABS. Systems using concrete slabs are generally cheaper than panel systems and offer the advantage of thermal mass, while panel systems offer faster temperature control and flexibility.
Radiant cooling from a slab can be delivered to a space from the floor or ceiling. Since radiant heating systems tend to be in the floor, the obvious choice would be to use the same circulation system for cooled water. While this makes sense in some cases, delivering cooling from the ceiling has several advantages. First, it is easier to leave ceilings exposed to a room than floors, increasing the effectiveness of thermal mass.
Floors offer the downside of coverings and furnishings that decrease the effectiveness of the system. Second, phd thesis concrete slabs, greater convective heat exchange occurs through a chilled ceiling as warm air rises, leading to more air coming in contact with the cooled surface.
Cooling delivered through the floor makes the phd thesis concrete slabs sense when there is a high amount of solar gain from sun penetration, because phd thesis concrete slabs cool floor can more easily remove those loads than the ceiling, phd thesis concrete slabs. Chilled slabs, compared to panels, offer more significant thermal mass and therefore can take better advantage of outside diurnal temperatures swings, phd thesis concrete slabs.
Chilled slabs cost less per unit of surface area, phd thesis concrete slabs, and are more integrated with structure. The modular nature of ceiling panels offers increased flexibility in terms of placement and integration with lighting or other electrical systems, but are less efficient than chilled beam systems. Lower thermal mass compared to chilled slabs means they can't easily take advantage of passive cooling from thermal storage, phd thesis concrete slabs, but controls can more quickly adjust to changes in outdoor temperature.
Ceiling panels are very suitable for retrofits because they can be attached to any ceiling. Chilled ceiling panels can be more easily integrated with ventilation supplied from the ceiling. The operative temperature is an indicator of thermal comfort which takes into account the effects of both convection and radiation, phd thesis concrete slabs. Operative temperature is defined as a uniform temperature of a radiantly black enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual nonuniform environment.
With radiant systems, thermal comfort is achieved at warmer interior temp than all-air systems for cooling scenario, and at lower temperature than all-air systems for heating scenario. Based on a large study performed using Center for the Built Phd thesis concrete slabs 's Indoor environmental quality IEQ occupant survey to compare occupant satisfaction in radiant and all-air conditioned buildings, both systems create equal indoor environmental conditions, including acoustic satisfaction, with a tendency towards improved temperature satisfaction in radiant buildings.
The radiant temperature asymmetry is phd thesis concrete slabs as the difference between the plane radiant temperature of the two opposite sides of a small plane element. As regards occupants within a building, thermal radiation phd thesis concrete slabs around the body may be non-uniform due to hot and cold phd thesis concrete slabs and direct sunlight, bringing therefore local discomfort.
The norm ISO and the ASHRAE 55 standard give the predicted percentage of dissatisfied occupants PPD as a function of the radiant temperature asymmetry and specify the acceptable limits. In general, people are more sensitive to asymmetric radiation caused by a warm ceiling than that caused by hot and cold vertical surfaces.
The detailed calculation method of percentage dissatisfied due to a radiant temperature asymmetry is described in ISO While specific design requirements will depend on the type of radiant system, a few issues are common to most radiant systems. Radiant cooling systems are usually hydroniccooling using circulating water running in pipes phd thesis concrete slabs thermal contact with the surface.
Typically the circulating water only needs to be 2—4 °C below the desired indoor air temperature. Depending on the position phd thesis concrete slabs the pipes in the building construction, hydronic radiant systems can be sorted into 4 main categories:. The norm ISO [24] focuses on embedded water based surface heating and cooling systems and TABS. Phd thesis concrete slabs on construction details, this norm distinguishes 7 different types of those systems Types A to G.
Radiant systems are associated with low-exergy systems. dispersed energy that has little ability to do useful work. Both heating and cooling can in principle be obtained at temperature levels that are close to the ambient environment.
The low temperature difference requires that the heat transmission takes place over relative big surfaces as for example applied in ceilings or underfloor heating systems. These sources can lead to important savings in terms of primary energy use for buildings. Some well-known buildings using radiant cooling include Bangkok's Suvarnabhumi Airport[26] the Infosys Software Development Building 1 in Hyderabad, IIT Hyderabad[27] and the San Francisco Exploratorium.
Heat radiation is the energy in the form of electromagnetic waves emitted by a solid, phd thesis concrete slabs, liquid, or gas as phd thesis concrete slabs result of its temperature. People, equipment, and surfaces in buildings will warm up if they absorb thermal radiation, but the radiation does not noticeably heat up the air it is traveling through. Some heat is also removed by convection because the air temperature will be lowered when air comes in contact with the cooled surface.
The heat transfer by radiation is proportional to the power of four of the absolute surface temperature. The emissivity of a material usually written ε or e is the relative ability of its surface to emit energy by radiation. A black body has an emissivity of 1 and a perfect reflector has an emissivity of 0. In radiative heat transfer, a view factor quantifies the relative importance of the radiation that leaves an object person or surface and strikes another one, considering the other surrounding objects.
In enclosures, radiation leaving a surface phd thesis concrete slabs conserved, therefore, the sum of all view factors associated with a given object is equal to 1. In the case of a room, the view factor of a radiant surface and a person depend on their relative positions.
As a person is often changing position and as a room might be occupied by many persons at the same time, diagrams for omnidirectional person can be used. Phd thesis concrete slabs time τ95aka time constantis used to analyze the dynamic thermal performance of radiant systems.
It is not affected by pipe diameter, room operative temperature, supply water temperature, and water flow regime. From Wikipedia, the free encyclopedia.
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