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A capillary tube mat is a flat composite structure of thin tubes (capillaries) with a distributor tube and a collector tube. The main applications include cooling ceilings (radiant cooling) and underfloor heating.
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The construction of the capillary tube mat models the networks of fine veins created by nature, which run under the skin (surface) of living creatures, and supply the organism with nutrients and also help heat regulation of the body. Capillary tube mats lay close beneath the surface in areas of rooms, and transport warm or cool water through them in order to control the temperature of the rooms. Since fluid always flows in parallel through many capillaries, similar to the veins under the skin of the body, the heat exchange with the environment is intense and energetically effective.
A room whose temperature is controlled by the use of capillary tube mats as a surface heat-exchanger requires flow temperatures for heating or cooling which need only be a few degrees away from the desired room temperature. At the same time, due to the large number of parallel capillary tubes, the drive energy required to maintain the flow is comparatively low. Due to the small distance of the capillary tubes to the surface of the room area, the system reacts very quickly. The temperature of the heating or cooling medium is given off very evenly and quickly to the environment due to the large number of capillary tubes. These two properties – very good heat transmission and low pressure loss – provide an advantage in terms of energy saving. In the broad definition of the terms of the technology, the capillary tube mat is a surface heat exchanger, and can be used for the transfer of heat between two media.
The typical capillary tube mat has capillary tubes with an external diameter of less than 5 mm. This makes the construction very flexible, and emphasizes the property of the "mat". The individual capillary tubes are arranged in a grid with a spacing of 10 to max. 50 mm from each other.
Capillary tube mats are usually made of plastic, such as polypropylene, which is frequently used in building for pipelines and in ventilation and air-conditioning equipment. This material and the small dimensions create the flexibility of the grid, and therefore the properties of the mat. The use of plastic in the manufacture of capillary tube mats, instead of copper or steel as in other cooling ceiling pipes, significantly reduces the costs. Since the capillary tubes are very thin-walled, the lower heat conductivity of the plastic compared to metals has no adverse effect on the heat transmission. Polypropylene is highly resistant to many chemicals (DIN 8078) and therefore very durable. Polypropylene is also very easy to recycle. Polypropylene is open to oxygen diffusion. This property requires that the capillary tube mats are always operated only in corrosion-protected pipe systems. This measure ensures the reliable function of the systems, and offers adequate protection against corrosion damage (corrosion and corrosion protection).
Capillary tube mats are produced by means of standard plastic-processing techniques such as extrusion, thermal plastic welding and injection molding.
The invention of capillary tube mats goes back to the year 1981, when the Berlin engineer Dipl.-Ing. Donald Herbst applied for his first patent for this technology (DE 31 24 048, registration date 15.06.1981, "Piping network for warm water surface heating of floors or walls"). During his many years of work on capillary tube mat technology, this was followed by a number of supplementary additional inventions/patents, which contributed to the continual further development of the manufacturing processes and applications of capillary tube mats. In the early years, the capillary tube mats were marketed under the brand "KaRo" (acronym of the German word "KapillarRohr" meaning capillary tube).
On the occasion of the 1984 International Building Exhibition in Berlin, the prize went to the draft of an energy-saving house produced by the architects of "Gerkan, Marg und Partner". Here capillary tube mats were used for the first time in a complex system in a residential building with a floor area of 1,200 m2.
Extensive scientific work by Prof. Dr. Mathias Fraaß (since 1991) and later by Prof. Dr. Bernd Glück (since 1994) created the necessary basic principles on the theory in the applications for capillary tube mats. Today capillary tube mats are installed worldwide. The annual production quantity is estimated at over 400,000 m2 (2010).
Capillary tube mats are used primarily in radiant cooling. Every type of cooling ceiling can be activated by capillary tube mats. In addition to plaster cooling ceilings with capillary tube mats, which require a plaster layer of less than 15 mm, capillary tube mats are also installed in metal cassette ceilings and in suspended plasterboard ceilings. The transmitted cooling performances for the different versions, at a temperature difference of 10 K between the average media temperature and the room temperature, lie between 65 and 90 W/m2. Capillary tube mats hanging freely in the room achieve cooling performances significantly in excess of 100 W/m2.
Capillary tube mats are also used for thermal building component activation. In contrast to conventional concrete core activation, the capillary tubes used in thermal building component activation lie about 5 mm close under the ceiling surface. This arrangement ensures a fast reaction and a high transmission performance of up to 90 W/m2 (at 10 K temperature difference, see above), and also uses the concrete mass as a thermal accumulator. Capillary tube mats can be used for the construction of very thinly built-up heating surfaces as underfloor or wall heating. A layer thickness of less than 15 mm is quite feasible. Capillary tube mats are also used as compact collectors for the exploitation of geothermal energy in heat pump plants. The extractor surface can be reduced in size through the use of capillary tube mats. In the processing and manufacturing industry, capillary tube mats are already in use for the temperature control of things such as acid baths.
In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics.
In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The measure is therefore equally relevant for lowering energy bills for heating in the winter, for cooling in the summer, and for general comfort.
A heat pipe is a heat-transfer device that employs phase transition to transfer heat between two solid interfaces.
Solar water heating (SWH) is heating water by sunlight, using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential and some industrial applications.
A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and solar towers or non water heating devices such as solar cooker, solar air heaters.
Electric heating is a process in which electrical energy is converted directly to heat energy. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that converts an electric current into heat. The heating element inside every electric heater is an electrical resistor, and works on the principle of Joule heating: an electric current passing through a resistor will convert that electrical energy into heat energy. Most modern electric heating devices use nichrome wire as the active element; the heating element, depicted on the right, uses nichrome wire supported by ceramic insulators.
Displacement ventilation (DV) is a room air distribution strategy where conditioned outdoor air is supplied at a low velocity from air supply diffusers located near floor level and extracted above the occupied zone, usually at ceiling height.
Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat technologies include renewable biofuels, solar heating, geothermal heating, heat pumps and heat exchangers. Insulation is almost always an important factor in how renewable heating is implemented.
Underfloor heating and cooling is a form of central heating and cooling that achieves indoor climate control for thermal comfort using hydronic or electrical heating elements embedded in a floor. Heating is achieved by conduction, radiation and convection. Use of underfloor heating dates back to the Neoglacial and Neolithic periods.
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms, for example, incandescent light bulbs get hot, a refrigerator warms the room air, a building gets hot during peak hours, an internal combustion engine generates high-temperature exhaust gases, and electronic components get warm when in operation.
Seasonal thermal energy storage (STES), also known as inter-seasonal thermal energy storage, is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever needed, such as in the opposing season. For example, heat from solar collectors or waste heat from air conditioning equipment can be gathered in hot months for space heating use when needed, including during winter months. Waste heat from industrial process can similarly be stored and be used much later or the natural cold of winter air can be stored for summertime air conditioning.
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 and displacement.
A solar combisystem provides both solar space heating and cooling as well as hot water from a common array of solar thermal collectors, usually backed up by an auxiliary non-solar heat source.
An infrared heater or heat lamp is a heating appliance containing a high-temperature emitter that transfers energy to a cooler object through electromagnetic radiation. Depending on the temperature of the emitter, the wavelength of the peak of the infrared radiation ranges from 750 nm to 1 mm. No contact or medium between the emitter and cool object is needed for the energy transfer. Infrared heaters can be operated in vacuum or atmosphere.
A snowmelt system prevents the build-up of snow and ice on cycleways, walkways, patios and roadways, or more economically, only a portion of the area such as a pair of 2-foot (0.61 m)-wide tire tracks on a driveway or a 3-foot (0.91 m) center portion of a sidewalk, etc. It is also used to keep entire driveways and patios snow free in snow prone climates. The "snow melt" system is designed to function during a storm to improve safety and eliminate winter maintenance labor including shoveling, plowing snow and spreading de-icing salt or traction grit (sand). A snowmelt system may extend the life of the concrete, asphalt or under pavers by eliminating the use of salts or other de-icing chemicals, and physical damage from winter service vehicles. Many systems are fully automatic and require no human input to maintain a snow/ice-free horizontal surface.
Soldering is a process of joining two metal surfaces together using a filler metal called solder. The soldering process involves heating the surfaces to be joined and melting the solder, which is then allowed to cool and solidify, creating a strong and durable joint.
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, 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.
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", "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 are usually not considered radiant heating or cooling. Within this category, it is practical to distinguish between high temperature radiant heating, and radiant heating or cooling with more moderate source temperatures. This article mainly addresses radiant heating and cooling with moderate source temperatures, 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.
Heating films are a method of electric resistance heating, providing relatively low temperatures over large areas. Heating films can be directly installed to provide underfloor heating, wall radiant heating and ceiling radiant heating.