Duct properties and parent airway (rock) properties?

[Fred_K]

Hi there!

Hoping to clear up my confusion.

When I build a duct, I can select a duct heat transfer preset (thermal conductivity, etc.). How is this considered in Ventsim?

The reason I'm asking is because as far as I can tell from the property window, ducts are treated as individual airways in their own right and appear to take on some properties from the parent drift, including the thermal properties of the rock and the VRT.

Is this correct? Are the duct properties considered in the background somewhere? How should I be thinking about this? 

Best regards,

Fred

[Martin Griffith]

Hi Fred, 

Thanks for your question. Although you can see thermal properties for the duct, such as VRT in the airway Edit Box, these are not used. When you build a duct, Ventsim remembers it's a duct and does not add any geothermal heat from the duct. 

In the Duct Builder Box you will see the duct heat transfer preset option, with thermal conductivity etc. This is to model the heat transfer between the air inside the duct and the air outside the duct. If you have high temperature outside the duct, this can heat up the air inside the duct. This heat transfer does not happen by default; it can also increase the time it takes for your Heat Simulation to converge. But if this heat transfer is something of interest to you, then you can select a Duct Heat Transfer preset and Ventsim will model it. There is also a setting in the Heat Settings that lets you toggle this effect on and off for the whole model. There are also properties in the Heat category that will show you the amount of heat transfered, which will also appear in a path graph generated from the Measuring tool. 

There is more of an explanation here: