Answer:
Ts = 413.66 K
Explanation:
given data
temperature = 20°C
velocity = 10 m/s
diameter = 5 mm
surface emissivity = 0.95
surrounding temperature = 20°C
heat flux dissipated = 17000 W/m²
to find out
surface temperature
solution
we know that here properties of air at 70°C
k = 0.02881 W/m.K
v = 1.995 ×
m²/s
Pr = 0.7177
we find here reynolds no for air flow that is
Re =
Re = ![\frac{10*0.005}{1.99*10^{-5}}](https://tex.z-dn.net/?f=%5Cfrac%7B10%2A0.005%7D%7B1.99%2A10%5E%7B-5%7D%7D)
Re = 2506
now we use churchill and bernstein relation for nusselt no
Nu =
= 0.3 + ![\frac{0.62 Re6{0.5}Pr^{0.33}}{[1+(0.4/Pr)^{2/3}]^{1/4}} [1+ (\frac{2506}{282000})^{5/8}]^{4/5}](https://tex.z-dn.net/?f=%5Cfrac%7B0.62%20Re6%7B0.5%7DPr%5E%7B0.33%7D%7D%7B%5B1%2B%280.4%2FPr%29%5E%7B2%2F3%7D%5D%5E%7B1%2F4%7D%7D%20%5B1%2B%20%28%5Cfrac%7B2506%7D%7B282000%7D%29%5E%7B5%2F8%7D%5D%5E%7B4%2F5%7D)
h =
0.3 + ![\frac{0.62*2506{0.5}0.7177^{0.33}}{[1+(0.4/0.7177)^{2/3}]^{1/4}} [1+ (\frac{2506}{282000})^{5/8}]^{4/5}](https://tex.z-dn.net/?f=%5Cfrac%7B0.62%2A2506%7B0.5%7D0.7177%5E%7B0.33%7D%7D%7B%5B1%2B%280.4%2F0.7177%29%5E%7B2%2F3%7D%5D%5E%7B1%2F4%7D%7D%20%5B1%2B%20%28%5Cfrac%7B2506%7D%7B282000%7D%29%5E%7B5%2F8%7D%5D%5E%7B4%2F5%7D)
h = 148.3 W/m².K
so
q conv = h∈(Ts- T∞ )
17000 = 148.3 ( 0.95) ( Ts - (20 + 273 ))
Ts = 413.66 K
Explanation:
( Check attachment for the design )
When capacitor is charging
![V_{c} = V_{cc} ( 1- e^{\frac{t}{Rc} })](https://tex.z-dn.net/?f=V_%7Bc%7D%20%3D%20V_%7Bcc%7D%20%28%201-%20e%5E%7B%5Cfrac%7Bt%7D%7BRc%7D%20%7D%29)
At
t = ![t_{0}](https://tex.z-dn.net/?f=t_%7B0%7D)
becomes ![\frac{2V_{cc} }{3} = V_{cc} ( 1- e^{\frac{-t0}{Rc} } )](https://tex.z-dn.net/?f=%5Cfrac%7B2V_%7Bcc%7D%20%7D%7B3%7D%20%20%3D%20V_%7Bcc%7D%20%28%201-%20e%5E%7B%5Cfrac%7B-t0%7D%7BRc%7D%20%7D%20%29)
![\frac{e^{t0} }{Rc} = 3](https://tex.z-dn.net/?f=%5Cfrac%7Be%5E%7Bt0%7D%20%7D%7BRc%7D%20%3D%203)
![T_{0} = 1.1 Rc](https://tex.z-dn.net/?f=T_%7B0%7D%20%3D%201.1%20Rc)
![T_{0} = 12 = 1.1 Rc](https://tex.z-dn.net/?f=T_%7B0%7D%20%3D%2012%20%3D%201.1%20Rc)
Rc = 10.909
So , Assume R = 10 MΩ
C = 1.0909 μ F
True
Use a file comb or wire brush to clear the clog...