- #1
sci0x
- 83
- 5
- Homework Statement
- Water in an insulated hot water tank is maintained at 80 degrees C. The external area of tank is 35m2. Calculate heat loss by i) convection ii) radiation
- Relevant Equations
- Q=UAdT
This is a past exam paper Q.
I think i might be missing info though.
For i) i use q=UAdT
A= 35m2
dT= (80-20)
They haven't given U but if i know answer should be 1,050W
So if i set U to 0.5
(0.5)(35)(60)
= 1050W
Am i missing something or could I calculate U with the info given?
Also ii)
Use stefan-boltzmann eq:
P = E(Stefan constant)(Area)(T^4 - T^4 in kelvin)
I don't have E the emissivity coefficient
Stefan constant is 5.67 x 10-8
80 degrees in K is 353.15
20 degrees in K is 293.15
P=E(162107.003)
The answer should be 643W
Can i calculate radiation from info given?
I think i might be missing info though.
For i) i use q=UAdT
A= 35m2
dT= (80-20)
They haven't given U but if i know answer should be 1,050W
So if i set U to 0.5
(0.5)(35)(60)
= 1050W
Am i missing something or could I calculate U with the info given?
Also ii)
Use stefan-boltzmann eq:
P = E(Stefan constant)(Area)(T^4 - T^4 in kelvin)
I don't have E the emissivity coefficient
Stefan constant is 5.67 x 10-8
80 degrees in K is 353.15
20 degrees in K is 293.15
P=E(162107.003)
The answer should be 643W
Can i calculate radiation from info given?