Barow
Civil/Environmental
- Jun 6, 2011
- 7
Hello again guys:
I'm having some difficulty with remembering some heat transfer concepts and I hope it is not an imposition to ask for a little bit of advise.I have a vessel or exposed pipe.... exposed to sunlight and the concern is that it can heat up to unacceptable conditions. I want to find out how much time it will take to heat up to upset conditions...or to prove that it won't ever because of maybe insufficient energy from sun to meet conduction rate?
+++++++++++++++
- I have calculated the amount of heat energy at upset condition for the contents of the vessel, = UpsetH.E (say UpsetH.E = 2000 Joules). I have also used Q= m*Cp*(T2-T1) for the metal to calculate the temperature differentials in the metal vessel need to achieve the UpsetH.E
a) Assuming the sunlight is the source of energy that will heat up the metal to upset conditions and I calculate that net flux density from sun (SunQQ" (Watts)) from the sunlight is .....say = SunQQ" = 20 Joules/second = 20 Watts
b) I have used formula for metal heat conduction Rate = k•A•(T1 - T2)/w.t (knowing all these values, conductivity, Area,wall, thickness e.t.c ) to calculate my heat transfer rate in Watts to the metal. Lets say, I find that my heat transfer rate = SteelRate = say 100 Joules/sec = 100 Watts
I want to intepret these results:
(i) Can I conclude that my upset condition cannot be reached because I have calculated a heat transfer rate of SteelRate = 100 Watts and I have only SunQQ" =20 Watts from my heat source (Sunlight). That is that the Sun's 20 Watts is insufficient transfer rate to get the vessel to heat up to Upset conditions ?
OR
(ii ) Can I say , irrespective of the heat trasfer rate in the metal, the effect of sun is cummulative and heat transfer will occure at the SunQQ =20 Watts and that I will reach my upset condition within a certain time .......given by 2000/20 = 100 seconds?. This is irrespective of my conduction rate?
I would really appreciate your answers
Thanks very much
I'm having some difficulty with remembering some heat transfer concepts and I hope it is not an imposition to ask for a little bit of advise.I have a vessel or exposed pipe.... exposed to sunlight and the concern is that it can heat up to unacceptable conditions. I want to find out how much time it will take to heat up to upset conditions...or to prove that it won't ever because of maybe insufficient energy from sun to meet conduction rate?
+++++++++++++++
- I have calculated the amount of heat energy at upset condition for the contents of the vessel, = UpsetH.E (say UpsetH.E = 2000 Joules). I have also used Q= m*Cp*(T2-T1) for the metal to calculate the temperature differentials in the metal vessel need to achieve the UpsetH.E
a) Assuming the sunlight is the source of energy that will heat up the metal to upset conditions and I calculate that net flux density from sun (SunQQ" (Watts)) from the sunlight is .....say = SunQQ" = 20 Joules/second = 20 Watts
b) I have used formula for metal heat conduction Rate = k•A•(T1 - T2)/w.t (knowing all these values, conductivity, Area,wall, thickness e.t.c ) to calculate my heat transfer rate in Watts to the metal. Lets say, I find that my heat transfer rate = SteelRate = say 100 Joules/sec = 100 Watts
I want to intepret these results:
(i) Can I conclude that my upset condition cannot be reached because I have calculated a heat transfer rate of SteelRate = 100 Watts and I have only SunQQ" =20 Watts from my heat source (Sunlight). That is that the Sun's 20 Watts is insufficient transfer rate to get the vessel to heat up to Upset conditions ?
OR
(ii ) Can I say , irrespective of the heat trasfer rate in the metal, the effect of sun is cummulative and heat transfer will occure at the SunQQ =20 Watts and that I will reach my upset condition within a certain time .......given by 2000/20 = 100 seconds?. This is irrespective of my conduction rate?
I would really appreciate your answers
Thanks very much