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# Calculation of heat loss from pipes

section
Length
section
m
Outside
diameter
of pipe
mm
Thickness
wall
pipe
mm
Material
pipes
Thickness
insulation
mm
λi
insul.
W/m²°C
tw
water
°C
ta
air
°C
b
coef.
support

+ More sections

Calculate the actual heat loss from the pipeline by taking into account the temperatures of the hot water and air surrounding the pipeline, the thickness and properties of the thermal insulation, and in the absence of insulation, determine the heat loss through an open pipeline with the help of this online tool. This program is based on the algorithm of heat passing through a cylindrical wall to provide the most accurate calculation of the actual heat loss from the pipeline.

## Method for Calculating Heat Losses from the Pipe

The value of heat losses from the pipeline section in one hour, W:

Q = b · l · q

• b - The coefficient takes into account heat losses due to supports, connections, and fittings. It is equal to 1.2 for steel pipelines with DN < 150 mm, 1.15 for DN ≥ 150, and 1.7 for non-metallic pipes. Note: The calculation is carried out without considering the coefficient 'b' if it is not specified in the table.
• l – section length, m;
• q – heat loss from one meter of pipe in one hour, W/m.

q = k · 3.14 · ( tw - ta )

• tw – water temperature in the pipeline, °C;
• ta – the temperature of the air surrounding the pipeline, °C;
• k – linear heat transfer coefficient, W/m°C;

k = 1 / ( ( 1/2λp ) · ln( Dop / Dip ) + ( 1/2λi ) · ln( Doi / Dii ) + 1/( αi · Doi ) )

• λp – coefficient of thermal conductivity of the pipe material, W/m²°C;
• λi – coefficient of thermal conductivity of thermal insulation, W/m²°C;
• Dip, Dop – inner and outer diameters of the pipe, respectively, m;
• Dii, Doi – inner and outer diameters of the insulation, respectively, m;
• αi - coefficient of heat transfer on the outer surface of thermal insulation, W/m²°C;

Interestingly enough, if you perform thermal insulation of the pipe with an insulation layer equal to the pipe's inner diameter, heat loss from one meter of pipes of all diameters from DN15 to DN150 will be the same!

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