10K. Maximum Temperature in Above Ground Lines Using Equation 10.59 Back to Main
This
page is used to determine the maximum temperature in above ground lines. The maximum temperature of the fluid in the line
is the result of gain of daytime heat from the sun by radiation and the
corresponding loss by convection to the air.
The relative rate of these would determine the rate of heating with
distance. The temperature depends on
time of day, atmospheric conditions, air temperature, wind velocity, color and
character of pipe surface, and flow rate and properties of fluid in pipe. The maximum line temperature may be
estimated by Equation 10.59.
Where: T =
max temp of fluid, °F
R = solar radiation absorbed, Btu/ft²
= air film coefficient for convection,
Btu/hr-ft2-°F
p =
3.1416
= ambient air temperature, °F
Equation
10.59 shows the maximum temperature possible with the sun directly overhead, a
clear sky and a long enough line to achieve thermal equilibrium between
radiation energy gain and convection loss.
In a typical case, the rise in temperature above ambient will not exceed
10 - 16°C [18 - 30°F].
To
calculate the maximum temperature, Pipe Surface Type must be determined. Choose
Highly oxidized steel, Oxidized, Normal, Bright, Aluminum paint, or White paint
by clicking on and shading the circle provided for that selection.
Once
the Pipe Surface Type has been chosen the Ambient temperature and Wind velocity
of the air must be entered into their entry spaces. To do so use the mouse to
click the curser in the entry spaces and input the data. Once this has been
done, select Run to execute the
solution.
Ambient
temperature is the temperature of the air surrounding the pipe.
Wind
velocity is the rate of the airflow around the surrounding the pipe. The wind velocity is used to estimate the
value of .