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I need to find heat loss from the greenhouse. I know how to find heat loss through the walls and roof , but what about soil ? how to find amount heat conductivity loss to the soil ? I would be gratefull for the any reference/method/ article or etc.

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  • $\begingroup$ If you can do conductivity for walls etc then ground is just different materials... $\endgroup$ – Solar Mike May 10 '18 at 7:48
  • $\begingroup$ @SolarMike the thing is, in case of walls I know the external temperature (dT). But for the soil I dont. $\endgroup$ – Oleg Khegay May 10 '18 at 8:18
  • $\begingroup$ So it depends on country / climate, where I am the average ground temperature varies between 5 to 10 degrees annually - research for your country / location... $\endgroup$ – Solar Mike May 10 '18 at 9:37
  • $\begingroup$ I'd be astonished if there weren't tables of soil thermal conductivity for different soil types, water content, etc. on the interwebz $\endgroup$ – Carl Witthoft May 10 '18 at 16:56
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    $\begingroup$ @OlegKhegay You cannot just stick a thermometer in the ground? $\endgroup$ – paparazzo May 10 '18 at 21:00
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Easy answer: Net heat loss averaged over day/night is zero because the heat that's transmitted into the soil when the greenhouse is hot is stored in the soil and returned to the greenhouse when the greenhouse becomes colder than the soil.

Hard answer suggestion: This problem is called "One-dimensional transient heat conduction in semi-infinite body". Semi-infinite because the ground is infinitely deep in the downwards direction but not in the upwards direction. It's time dependent. The rate of heat loss will go down as it progresses because the ground becomes hotter. You can write and solve the DEs by hand if you wanted a hard exercise in calculus. Here's somebody's working: https://www.thermalfluidscentral.org/encyclopedia/index.php/One-dimensional_transient_heat_conduction_in_semi-infinite_body

Whiteboard lecture video: https://www.youtube.com/watch?v=X8ofOO-iHhk

Practical answer: I would use Finite Element Analysis (FEA) which does all that math for you. Download some FEA software and use time dependent or transient heat transfer analysis. This will also allow you to model 2D and 3D effects like heat flow around the edges. The two 1D suggestions above are not strictly correct because of lateral heat flow under the ground but the bigger the greenhouse, the more accurate the 1D approximation is.

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  • $\begingroup$ thank you for the answer. Could you say, if Solidworks can help me for solving such kind of problems in the better way than Ansys ? or solidworks is served for different tasks ? $\endgroup$ – Oleg Khegay May 13 '18 at 5:55
  • $\begingroup$ Yes, SolidWorks Simulation can do that just as well as Ansys for a simple task like this. I think SolidWorks Simulation is a little easier if you're not familiar with either. $\endgroup$ – user1318499 May 14 '18 at 7:39

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