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Posted By: mike7The various curves on the second graph show how the heat spreads through the ground in the course of a year. (The value of diffusivity used is 1.38E-7m2/s). The ripples have just about petered out after 4 metres, which is what I was expecting in my wee graph posted earlier.
Posted By: mike7There are 20 colours, each showing the temperature distribution at a particular time - the year is divided into 20 intervals, stated in seconds (!). The run starts with the temperature at +1 ie. top left, goes down to -1 at six months in, then back up to 1 again.The 4 metres figure depends on the particular diffusivity of the soil involved, so if the soil were more conductive or had lower specific heat the ripples would reach further.
Posted By: ralphdI think the best way to do PAHS is circulating water instead of air (given the much higher heat capacity of water). Instead of digging the pipes deep into the ground, I think insulating between the pipes and slab is better (easier to construct).
Posted By: djhThe motivation for digging is power transmission and hence energy storage capacity. From a square metre of surface, you can only push heat into it at a particular rate (power), given a limit on the temperature of the heat source. So that limits the total heat energy you can store over the summer.
Posted By: pmccAnd I like the idea that air can be managed passively or using minimal mechanical effort.
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