Heat Transfer Y2 Flashcards
(9 cards)
1
Q
Transient Conduction 1D Wall Method
A
- Set x=0 on the opposite side to T∞, x=L for exposed face
- For Fo > 2 (Apparently??) use i = 1, get ζ and C coefficients from Table
- Ti is initial temperature
2
Q
Internal Flow Method for finding h
A
- Find Reynolds Number (using diameter)
- Look in FB to see if it’s turbulent or laminar
- Check the entry length makes the question valid (FB equation)
- Get the Nusselt number from FB depending on isothermal or “isoflux” condition
- Get h from Nusselt number Nu = hL/k
3
Q
Log-Mean Temperature
(For uniform surface temperature, internal flow)
A
ΔTlm = (ΔT₀ - ΔTi) / ln(ΔT₀ / ΔTi)
4
Q
Hydraulic Diameter - Characteristic flow length for non-circular pipes
A
D = 4 Ax / P
(P is perimeter, A is cress-sectional area)
5
Q
How to use log-mean temperature for heat power
Internal flow with uniform surface temperature only
A
q = L P h ΔTlm
6
Q
Heat capacity rates Cc & Ch
A
Cc = mdotc * CP,c
etc…
7
Q
Heat exchange powers for a heat exchanger
A
q = Cc (Tc,o - Tc,i)
q = Ch (Th,i - Th,o)
8
Q
Internal flow transfer power q for constant q”
A
Mdot * CP ( Tm,o - Tm,i )
9
Q
Thermal Diffusivity, α
A
α = k/ρc
