Convection Heat Transfer In Cavity Flashcards
What are the reasons for convection heat transfer in cavities?
Natural convection currection will be set up if there is sufficient temperature in the air gap.
There should be little convection in gaps less that 25mm.
What is the aim of part L of the building regulations?
Reduce the consumption of fossil fuels. To reduce the production of CO2 for climate change.
How to balconies and other protrusions affect heat transfer.
Protrusions from the flat surface of the building increase the surface area and so increase the conductive heat transfer.
The corrected resistance is equal to the surface resistance multiplied by the projected area divided by the flat area.
Explain thermal bridging of a structure
If a structure is non homogenous the more conductive parts of the structure will create a thermally conductive bridge. To calculate this you average out the thermal resistance of the two substances weighted by area.
How do you calculate the U value for a sloping roof with a horizontal suspended ceiling?
Rt = Rsi + Rceiling + Ra + (Rroof + Rso)cos theta.
Explain how heat is lost from the ground
Heat loss from the ground is purely conductive and so is more steady that heat loss to the atmosphere. Heat moves slowly through the ground at lower levels.
