Unsteady state heat transfer Flashcards
Heat transfer in real life is…
in unsteady state
Thermal capacity of a wall determines how
quickly heat will pass through
How does thermal mass apply in summer heat?
High vs low thermal mass
High thermal mass = Less heat loss
Low thermal mass = Hot house during day and cold house during night
Which has more dampening? High or low thermal mass walls?
High thermal mass
Time lag - Definition and significance
The time delay in temperature.
A high thermal conductivity = Shorter time lag
High density and high thermal capacity = longer time lag
Time lag in a wall construction is affected by
- Thermal conductivity
- Density
- Thermal Capacity of the materials
Sol-air temperature
Outside air temperature which, in the absence of solar radiation, would give the same temperature distribution and rate of heat transfer through a wall (or roof) as exists due to the combined effects of the actual outdoor temperature distribution plus the incident solar radiation
What is Admittance?
Rate of heat flow through the internal surface of a structure when the indoor environmental temperature changes based on a 24-hour cycle
Unit of Admittance
W/m2k
