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​​​​​Glossary of Terms: heat flow.

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 TI: Heat Flow


   FAQ Heat Flow.


Heat flow (measured in units of W/m or W/m²) is the movement of thermal energy whereby areas of high temperature become cooler and areas of low temperature become warmer.


Are heat flow and temperature change the same thing?

No. But the two are closely related. Temperature change only occurs when enough heat has flowed away from a pipe. In practice the temperature change of a flowing medium in pipework is small but no change in temperature does not however mean that there is no heat loss/gain.

Without pipe insulation a boiler or chiller must work harder to compensate for the heat lost/gained and so the difference in heat flow between an insulated and uninsulated pipe is an energy saving.


What thickness of insulation stops all heat flow?

Insulation can never eliminate heat flow entirely and there will always be some flow of heat through insulation - however thick it may be. Increasing thicknesses results in greater reductions but the law of diminishing returns makes each additional percentage reduction in heat flow increasingly expensive to achieve.


How is the thermal conductivity related to heat flow?

The thermal conductivity is a measure of how easily heat can pass through an insulation material. The heat flow through a material can be calculated using BS EN ISO 12241 - provided the thermal conductivity is known.




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