Heat Loss Insulated Pipe Equation and Calculator

Heat Transfer Engineering

Equations and calculator to determine the conductive heat loss through a cylinder with multiple layers that may include a pipe wall insulation.

The temperature gradient within a homogeneous material results in an energy transfer rate within the medium which can be calculated with the following equation

Heat Loss equation eq. a

Insulated Pipe

The illustration above depicts a single-layer cylindrical wall of a homogeneous material with constant thermal conductivity and uniform inner and outer surface temperatures. At a given radius the area normal to radial heat flow by conduction is 2 Π r L, where L is the cylinder length. Substituting this into (eq. a) and integrating with q constant gives:

Delta tempaeratureeq. 0

or

Heat loass equation eq. 1

Multi Layer Pipe

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From (eq 1) the thermal resistance of the single cylindrical layer is [ ln (r2 / r1) ] / 2rkL. For a two-layered cylinder show below the heat transfer rate is,

Conductive Heat Flow = Overall Temperature Difference / Summation of Thermal Resistance's

Heat loss divided by length eq 2

or

Heat loss eq 3

Where:

k = thermal conductivity (Btu / h · in· °F)
ka = thermal conductivity inner wall (Btu / h · in· °F)
ka = thermal conductivity outer wall (Btu / h · in · °F)
L = length of cylinder and insulation layer (in)
q = conduction (Btu / h · °F)


The following is the original (pre-7/2016) equations and calculator:

ΔT = (TsEst - Ta)

hs = ΔT - Ds + ΔT2 + Ds2 - ΔT Ds

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User Reviews/Comments:

By: Carl Rowe - Jul 18, 2014
Could you please update these calculators/ formulas so that you can select in SI or enter in metric for active fields. it does show you what the conversion is but can you have it so it can do both.



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