Insulated pipes

insulated pipes (called also preinsulated pipes) are widely used for district heating and hot water supply in Europe. They consist of steel pipe, insulation layer and outer casing. Main purpose of such pipes is to keep the temperature of the fluid in pipes. Usually it is the pre-heated water from district heating plants, that flows to households by "flow pipe" and flows back to heating plant by "return pipe". Most commonly used are insulated pipes with one pipe in insulation, but in 2000-ties in Europe it is becoming popular to use also two pipes with insulation in one casing.

As insulation usually is used polyurethane foam and it's variations, with heat conductivity coefficient λ=0,033-0,024 W/mK (called also thermal conductivity). Outer casing usually is high density polyethylene (HDPE). Production of preinsulated pipes for district heating in European Union is regulated by norm EN253. According to norm EN253:2003, pipes must be produced to work at constant temperature of flow water of 130°C for 30 years, keeping heat conductivity lower or equal to λ=0,033 W/mK. There are three insulation thickness levels.

Insulated pipelines usually are assembled from pipes of 6m, 12m or 16m in length, laid underground in depth 0.4-1.0m. Efficient working time of district heating pipelines networks is estimated as 25-30 years, after which they need to be re-built with new pipes.

4 major producers of preinsulated pipes in Europe are located in Denmark and Sweden.

ee also

* District heating
* Heat conduction
* Heat transfer
* Heat transfer mechanisms
* R-value
* Specific Heat
* Thermal bridge
* Thermal contact conductance
* Thermal diffusivity
* Thermal resistance in electronics
* Thermistor
* Thermocouple