Soil temperature below a tank. 1

[FWilson]

I need to predict the temperature of soil 24" below a constant 185 deg F. tank bottom. I can estimate soil type and water content. Any ideas on how to approximate the temperature?

 

[COEngineeer]

Would it be that significant that you cant just assume it is 185 F also?

 

[civilperson]

In time, the constant temperature will achieve equilibrium with the soil. 185 F is probably that equilibrium at any distance less than the radius from the center.

 

[CarlB]

The path of heat flow through the soil under the tank will be downward at the tank, turn outward, then up. Tubes of equal heat flow spread out further from the tank. Sort of like a groundwater flow net under a dam we learned at school, except 3d. The rate of change in temperature with distance along this path decreases away from the tank. If the tank has a 5' radius, there could be a lot of temperature change over the 2'. At 50' radius, not so much.

 

[BigInch]

What is the soil temperature without the tank there. There should be a temperature at around 8-10 ft depth that is constant throught the whole year. Heat flow will be radial at the edges to the surrounding soil, however at the center of the tank heat flow will be down and disipating into the soil.

At 24" depth anywhere under the tank, it should quickly arrive at almost the same tank temperature.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[fratrowie]

if its necessary for you estimate the temperature, find a portion in the side of the tank in considerable depht with the same properties (soil type, water content) of depth in question and investigate...


fratrowie

 

[BigInch]

If its not built yet, investigating is a problem. Much easier to write a spreadsheet to do 2D heat transfer.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[JoeTank]

Many years ago I heard a co-worker state that he had performed a detail thermal analysis of several problems like yours and concluded that the bulk temperature of the tank product would penetrate about one-half of the tank diameter into the soil at the centerline of the tank. I don't know the details of the soil or water table, but I do recall that the steady state conditions took many months of continuous service to achieve that result.

Joe Tank

 

[BigInch]

See item number 61 here,

http://irc.nrc-cnrc.gc.ca/pubs/cbd/index_e.html

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[FWilson]

Thanks everyone, this information allows me to estimate as I needed to do.