Estimate the depth in moist soil at which the annual temperature variation will be 10% of that at the surface.
GIVEN
Moist soil
FIND
The depth in moist soil at which the annual temperature variation will be 10 per cent of that at the surface
ASSUMPTIONS
Conduction is one dimensional
The soil has uniform and constant properties
Annual temperature variation can be treated as a step change in surface temperature with a 6 month
response time
SKETCH
The geometry of this problem is a semi infinite solid as covered in Section 3.4. The transient temperature for a change in surface temperature is given by
Where Ti is the temperature of the soil until the surface temperature is increased to Ts. For an annual
temperature variation of less than 10% of that of the surface
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