Chapter 10K

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 .

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