**Related Resources: Heat Transfer Engineering Design**

### Heat Loss or Gain From Pipe Excel Spreadsheet Calculator

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Heat Loss or Gain From Pipe Excel Spreadsheet Calculator

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Calculate the Inside heat transfer coefficient

The formula depends on the flow region

For Laminar flow (Re < 2100) use Sieder and Tate

For this illustration, assume viscosity at wall = bulk viscosity

Laminar flow calculation N/A

For Transition flow (2100 <= Re <= 10000), use Hilpert correlation

For this illustration, assume viscosity at wall = bulk viscosity

It is NOT RECOMMENDED to be in the transitional region, and the correlation is iffy

Transitional flow calculation N/A

For Turbulent flow (Re>10000) use Sieder and Tate (same as Dittus-Boettler, but with viscosity correction)

For this illustration, assume viscosity at wall = bulk viscosity

Turbulent flow calculation 3,440

Note: alternative turbulent flow correlation from Gnielinski

Said to be valid from 3000 < Re < 5,000,000

Because the outside heat transfer coefficient will be so much less than the inside coefficient, it really doesn't make a practical difference if the calculation for inside coefficient is off

Calculate the outside heat transfer coefficient

The outside coefficient is calculated differently for the cases of wind or no wind

No wind = natural convection

Three temperatures to be concerned with, ambient (T4), surface (T3), and average T5 = (T4 + T3)/2

Since T3 is a function of the heat transfer, this is an interative calculation

First, assume a value for T3, the surface temperature

T3_assume

Calculate T5

T5

Get the properties of air for temperature T5

I did a simple linear regression of thermal conductivity for air at atmospheric pressure

MW

P

kair

cair

dair

muair

For no wind condition,

Beta

Gr

Prair

Nuair

Calculation for the case where wind is present

Note that for very low wind velocity (<0.5 m/s), use the greater of this calc or the no-wind calc

Rewind

B

n

Nuwind

Next, calculate the radiation loss

hrad

Add the convection and radiation heat transfer coefficients together

ho

Calculate surface temperatures and iterate until calculation = assumed

Calculate the overall heat transfer coefficient

U

Next, the heat loss through the wall

Q

Calculate the inside wall and surface temperatures based on the estimated surface temperature from above

T3calculated

Calculate the fluid temperature as it exits the pipe segment

Assumes constant properties and constant heat flux along pipe length

For significant temperature changes, divide pipe into segments and calculate sequentially

Reference:

Cao, Eduardo, Heat Transfer in Process Engineering, McGraw-Hill, 2010

Excel Calculator Credit:

Stephen Hall