thermal conductivity of soil (clay)

[onuigbo]

Can somebody tell me the thermal conductivity of soil or any approximate k-value for soil (clay).Is there any formula I could use to compute this, or any formula for the heat loss for buried pipes, given the depth of the pipe, pipe size and steam temperature.

We deliver steam as if your life depends on it.

 

[CarlB]

The Army Publication, "ARCTIC AND SUBARCTIC CONSTRUCTION: UTILITIES", at

http://www.usace.army.mil/publications/armytm/tm5-852-5/

has formula for heat loss from buried pipes and thermal conductivity values for various soils.

 

[quark]

ASHRAE handbook of HVAC systems and equipment deals with this in details.

The following approximate values can be considered if you don't have your soil analysis.

sand silt clay
moisture<4% 0.17 0.08 0.08
moisture4 to 20% 1.08 0.75 0.58
moisture>20% 1.25 1.25 1.25

Soil resistance(Rs) = ln[(d/ro)+((d/ro)[sup]2[/sup]-1)[sup]1/2[/sup]]/2PiKs for d/ro>1

and Rs = ln(2d/ro)/2PiKs

Where d is burial depth of pipe to the centerline in ft
ro is outer radius of pipe in ft
Ks is conductivity of soil in btu/hr.ft.F

Heat loss Q = (Tf-Ts)/R

Where Tf is fluid temperature and Ts is undisturbed soil temperature. For yearly average heatlosses, soil temperature can be approximated to the average dry bulb temperature.

Regards,