Heat transfre for a domestic radiator


by nickbone59
Tags: domestic, heat, radiator, transfre
nickbone59
nickbone59 is offline
#1
Aug5-07, 09:18 AM
P: 7
Any suggestions anyone??? Really struggling with this one !!
1. The problem statement, all variables and given/known data
A domestic radiator is 2.5 m long and 0.6m high and is sited in a room whose temperature is 14C. Hot water is circulating through the radiator at a temperature of 90c. The radiator is convecting heat from both sides but only radiating from one side. Given that the surface emissivity is 0.7, calculate the total heat transfer from radiator to the room.



2. Relevant equations
Stefan-Boltzmann Constant = 5.67x10^-8

Nu = 0.59(Gr.Pr)^0.25 for laminar flow (GR.Pr)<10^9
Nu = 0.129(Gr.Pr)^0.33 for turbulent flow (GR.Pr)>10^9
where,
Grashof no. Gr= ([tex]\rho[/tex]^2[tex]\beta(\theta[/tex]1-[tex]\theta[/tex]2)l^3)/[tex]\mu[/tex]^3

Nusselt No. Nu= hl/k

Prandtl No. Pr=Cp[tex]\mu[/tex]/k


3. The attempt at a solution

Q= [tex]\sigma\epsilon[/tex]A(T1^4-T2^4)

= 5.67x10^-8 x 0.7 x 1.5 x (1.736x10^10-6.785x10^9)

= 629.8W
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution
Phys.Org News Partner Science news on Phys.org
Cougars' diverse diet helped them survive the Pleistocene mass extinction
Cyber risks can cause disruption on scale of 2008 crisis, study says
Mantis shrimp stronger than airplanes
Astronuc
Astronuc is offline
#2
Aug5-07, 09:28 AM
Admin
Astronuc's Avatar
P: 21,637
Looks like you got the radiated heat correct. It would be preferable to include units with the numbers.

Now find the convective heat. One needs a formula for the convective heat transfer coefficient.


Register to reply

Related Discussions
Car radiator as a heat exchanger Engineering Systems & Design 13
Radiator Maxumum Heat Transfer Classical Physics 11
Heat recovery from car radiator. Engineering Systems & Design 36
Domestic USA good/bad General Discussion 7
Domestic fans....please help! General Discussion 4