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Glossary - Low Temperature District Heating

Low Energy Buildings, 4G, 4th Generation District Heating, Energy Planning, Futurism, Low Temperature Operation, Low Grade, Distribution Network, Branched Network, Piping Systems, Termis Screen Shot, 7T, Danish Cases, Danish Heat Supply Act, Radiator Performance, Bölgesel Isıtma Sistemleri, Renewable Energy Sources, Kentsel Dönüşüm, Lystrup, Danish Cases
Low Temperature District Heating Systems, the 4th generation (4G) district heating technology, are superior with their low degrees of temperature that is commonly with 55°C of supply and 25°C return. In this blog post, the terminology commonly used in the field of low temperature district heating systems is published to keep the consistency/standardization of the terms. Some being newly famous with the low temperature upgrade, though most are already common in the field of District Heating technology. Links for the original document which this blog post based on are provided at the bottom of the page.

Description of the Terms 

Low Temperature: Excessively low temperature supply of about 50°C to the heated space
Low Energy: Used for district heating systems operating at low temperatures.
Low grade: Surplus heat at low temperatures which it is hard to exploit.
Heat carrier medium: A medium consisting of a fluid used to transport heat in such a way that a change in enthalpy occurs through an endothermic reaction that takes place, for example at the heat source, and an exothermic reaction, for example one of positive effect for consumers.

Pipe Network: A closed circuit of several pipes connected to each other hydraulically for the purpose of circulating a heat carrier medium from a heat source to consumers.
Node: A junction of several pipes or a sign for heat consumers.
Leaf node: A node without any successor node (also used as end-node/end consumer).
Root node: A node without any predecessor node, in reference to a heat source.
Pipe segment: A short segment of pipe that connects a node to a succeeding node, in the order from root node to leaf node.
Route: A sequence of pipe segments extending from a root node to a respective leaf node.
End-user connection: A service pipe that provides the means of circulation taking place within a district heating network, used for in-house installation.
Network layout: The shape of a pipe network with respect to the interconnections between the pipes.
Branched network: The tree-like formation of a network providing a unidirectional flow from the root node to the leaf nodes.
Looped network: The looped formation of a network shaped in the form of closed paths composed of pipe segments, in which each heat-demanding node has a number of alternative paths for the flow to be supplied by one of the neighboring nodes.
Supply line: A pipe line employed to deliver the heat carrier medium after its enthalpy has increased at the heat source (Also known as feed line -especially in Denmark-).
Return line: A pipe line employed to transfer the medium back to the heat carrier medium after its enthalpy has been released through heat consumption by the in-house installations of consumers.
Single pipe: An insulated type of pipe used in district heating networks, the pipe being protected or shielded by an insulating casing.
Twin pipe: An insulated type of pipe used especially in district heating networks, involving two pipes, both of the same diameter, protected overshielded by an insulating casing.

Pump Station: A major facility in a district heating network, one that provides the difference in pressure difference required to circulate a heat carrier medium.
Pressure drop: A loss in pressure during circulation of the heat carrier medium through the pipe network involved, one due to frictional forces (also termed as pressure loss).
Head lift: The maximum amount of pressure the pump can provide, the measure of it being given as the vertical lift of the medium.
Booster pump: A small-scale facility a network is equipped with, one located close to the consumers, for the purpose of providing an increase in the pressure of the supply line, in addition to the residual pressure capacity from the main pump station.
Holding pressure: A certain minimum amount of pressure maintained in the heat carrier medium during its circulation, in order to prevent the risk of cavitation.
Pressure gradient: A physical quantity representing the rate of change in pressure with respect to the length of the pipe segment or segments to which it is applied.

Substation: An in-house installation at a consumer site that conveys the heat content to be used in the space heating of a house and in the production of domestic hot water
Buffer tank: A small-scale tank used for the storage of heat in a substation, one that stores heat content from the district heating network during off-peak times of day for it to be used for in-house heat needs at peak times (also termed as storage tank).
Thermostatic valve: A self-regulating valve used in connection with in-house heating systems, one that regulates the flow of an in-house heat carrier medium in accordance with the heat demand rate.
Bypass valve: A self-regulating valve used in connection with a district heating network, its transmitting the supply-heat carrier medium, when its temperature be degraded, to the return line, to then be circulated to the heat source.

Heat Demand: The heat energy requirement of a consumer site.
Heat load: The heat energy that needs to be conducted by a district heating pipe network.
Simultaneity factor: A factor reducing the effect on the estimated heat load through taking advantage of the asynchronous heat use by multiple consumers, since use of heat by different consumers involved occurs neither all at the same time nor at the same rate.
Heat load duration: A decrescent way of showing heat loads together with their duration of occurrence during the period of a year with respect to a given district.
Heat load factor: The ratio of any particular heat load to the peak heat load rate.
Heat density: A physical quantity representing the unit of overall heat load per area of the land on which the district heating network is employed.

Please cite to: Tol, Hakan İbrahim, PhD Thesis, 2015, District heating in areas with low energy houses - Detailed analysis of district heating systems based on low temperature operation and use of renewable energy.

This PhD thesis and other publication of the author can be reached from:
ResearchGate (Click!)
DTU Employer Page (Click!)
Google Scholar (Click!)
LinkedIn (Click!)

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