• Support PF! Buy your school textbooks, materials and every day products Here!

Temperature(thermal radiation transfer)

  • Thread starter Ajwrighter
  • Start date
  • #1
42
0
1. A solid cylinder of radius r1 = 2.3 cm, length h1 = 4.2 cm, emissivity 0.88, and temperature 24°C is suspended in an environment of temperature 55°C. (a) What is the cylinder's net thermal radiation transfer rate P1? (b) If the cylinder is stretched until its radius is r2 = 0.52 cm, its net thermal radiation transfer rate becomes P2. What is the ratio P2/P1?



2. P1 = ([tex]\sigma[/tex]) ([tex]\epsilon[/tex]) A1(Tenv4 - T4)

A1 = 2([tex]\pi[/tex]) r12 + 2 ([tex]\pi[/tex]) r h




3. A1 = 9.393362*10-3m2
P1 = (5.67*10-8)(.88)(9.393362*10-3)((273+55)4-(273+24)4)) = 1.77W



I have (b) .. but for some reason (a) is wrong.. here is answer for (b) [tex]\frac{P2}{P1}[/tex] = 2.87
.
 
Last edited:

Answers and Replies

  • #2
42
0
Ok I just did it in mathmatica .. and it gave the same answer .. If
my intuition is incorrect then the only possible solution would be
that P1 is somehow =([tex]\sigma[/tex]) ([tex]\epsilon[/tex]) A1((24+273)4) ... but thats not how the question reads
 
  • #3
42
0
I asked a friend he agrees with me.. but are we both wrong? not sure why the answer is considered wrong
 
  • #4
42
0
had another person agree.. anyway I could get someone to review this problem and confirm?
 
  • #5
42
0
any attempts?
 
  • #6
42
0
ok I've resolved the problem. Both the book, and their online website have two distinct wrong equations to use.. The correct one would involve flipping the Tenv^4 with the T^4.. so it would read (T^4 - Tenv^4). So, I dub this problem as resolved in case anyone was interested.
 

Related Threads for: Temperature(thermal radiation transfer)

  • Last Post
Replies
14
Views
4K
Replies
2
Views
1K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
2
Views
460
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
2
Views
4K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
11
Views
610
Top