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Determination of temperature of outer surface of a pipe when there is n
Atmospheric temperature tatm 40
Peak solar radiation E 1000
Emissivity ε 0.85
Pipe size Do
610
Thickness of the pipe t 5.8
Pipe inside diameter Di 598.4
Pipe outer surface area considering unit length Ao 1.9154
Equilibrium temperature of the pipe outer surface te 67
heat transfer coefficient of the pipe outer surface (h0) h=1.32(ΔT/D)1 4
h=1.24(ΔT/D)1/3
Total radiation incident on pipe surface E XD0X 1 610
radiation absorbed by the pipe surface Q=E XDO X1Xε 518.5
Radiation Heat Loss from the Pipe Surface Q 1 Q 1=σAo ε*(te+273)4-(tatm+273)
4347.5974864
Convective heat loss from the outer surface of the pipe Q 2 Q 2=h X Ao X(te-tatm) 176.0782287
Considering the inner surface of the pipe as insulated i.e no loss for conduction,
at Equillibrium
Q=Q 1 +Q 2
Q1+Q2 523.6757151
HENCE,SKIN TEMP WIILL BE ,say=67 DEG C
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water flow and when the inner surface of the pipe is insulated
0C
W/m2
Stephen boltzman constant σ 5.67E-08 W/m2K
4
conductivity for carbon steel K 60.5 W/mK
mm IS 3589
mm
mm
m20C Assumed;by trial and error
3.404728 (for laminar flow) W/m2K (refre page no.202, Heat and Mas
4.331246 (for turbulent flow) W/m2K
W Considering the upper half of the pipe surface in absorbing the radiation
watts l
watts
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s Transfer by C.P Arora)
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Determination of temperature of outer surface of the pipe when water is not fl
Atmospheric temperature tatm
Peak solar radiation E
Emissivity ε
Pipe size Do
Thickness of the pipe t
Pipe inside diameter Di
Pipe outer surface area considering unit length Ao
Equilibrium temperature of the pipe outer surface te
heat transfer coefficient of the pipe outer surface (h0) h=1.32(ΔT/D)1/4
h=1.24(ΔT/D)1/3
Total radiation incident on pipe surface E X D0 X1
total radiation absorbed by pipe surface E XDoX1 X ε
Radiation heat loss from the outer surface Q 1 Q 1=σεAo[(te+273)4-(tatm+2
convective heat loss from the outer surface of the pipe Q 2 Q 2=h X Ao X(te-tatm)
Q=Q 1+Q 2 412.9278823
Conduction heat loss 105.5721177
assume the temperature of inside surface of the pipe is ti 61.9945
Conduction heat loss Q cond 108.8396406
Now considering the Convection Heat transfer coefficient as h= h=1.32(ΔT/Di)1/4
h=1.24(ΔT/Di)1/3
Convection Heat loss from inner surface of the pipe is 107.4625195
Radiation heat loss+covection heat loss+conduction heat loss 521.7675229
HENCE,THE OUTSIDE SURFACE SKIN TEMP BECOMES 57 DEG C
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wing and cosidering heat transfer also from inner surface
400C
1000 W/m2
Stephen boltzman constant σ
0.85 conductivity for carbon steel k
610 mm IS 3589
5.8 mm
598.4 mm
1.9154 m2
620C Assumed;by trial and error
3.234798 (for laminar flow) W/m2K (refre page no.202,
4.048203 (for turbulent flow) W/m2K
610 W
518.5 W
73)4] 276.6174 W
136.3105 W
W
W0C CONSIDERING NO FLOW THROUGH THE PIPE
W
3.250362 (for laminar flow) W/m2K
4.073934 (for turbulent flow) W/m2K
Assumed heat trasfer due to convection will be 80% due to confined area
Assmed no heat trasfer due to radiation from inside surface
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5.67E-08 W/m2K
4
60.5 W/mK
Heat and Mass Transfer by C.P Arora)
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Determination of temperature of the outer surface of a pipe when
Atmospheric temperature tatm 400C
Peak solar radiation E 1000 W/m2
Emissivity ε 0.85
Pipe size Do 610 mm IS 3589Thickness of the pipe t 5.8 mm
Pipe inside diameter Di 598.4 mm
Pipe outer surface area considering unit length Ao 1.9154 m2
The temperature of water flowing inside the pipe tw 320C
radiation incident on the pipe surface Q=EεD0 518.5 watts
Equilibrium temperature of the pipe te 32.03330C Assumed;b
temperature of inner surface of the pipe is ti 320C
Heat loss due to the conduction from outer to inner surface
Q cond [2πkL(te-ti)/(ln(r0/ri)] 658.9746
Considering the convection as well as radiation loss from the atmosphere to pipe surface, we get
heat loss due to conduction from outer to inner surface=radiation incident on the pipe surface +covective heat
convective heat transfer coefficient h=1.32(ΔT/Di)1/4
Refer Page No.202, Haet and Mas
h=1.24(ΔT/Di)1/3
[2πkL(te-ti)/(ln(r0/ri)]=( EεD0)+(2πDo/2000) σεX(tatm+273)4-(te+273)
4)+hAo(tatm-te)
648.2912051
HENCE,THE SKIN TEMP WILL BE 32.09DEG C ,say=33 DEG C
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ater is flowing through the pipe.
Stephen boltzman constant σ 5.67E-08 W/m2K
4
conductivity for carbon steel k 60.5 W/mK
y trial and error
ain from atmosphere+ rediative heat gain from atmosphere
s Transfer by Dr. C.P Arora
