Determination of temperature of outer surface of a pipe when there is no water flow Atmospheric temperature
tatm
Peak solar radiation Emissivity Pipe size Thickness of the pipe Pipe inside diameter
E ε Do t Di
1000 0.85 610 5.8 598.4
Pipe outer surface area considering unit length
Ao
1.9154
Equilibrium temperature of the pipe outer surface
te
heat transfer coefficient of the pipe outer surface (h0)
40
67
h=1.32(ΔT/D)
1/4
h=1.24(ΔT/D)
1/3
Total radiation incident on pipe surface radiation absorbed by the pipe surface
E XD0X 1
Radiation Heat Loss from the Pipe Surface Q1
Q1=σAo ε*(te+273)4-(tatm+273)4] 347.5974864
Convective heat loss from the outer surface of the pipe Q2
Q2=h X Ao X(te-tatm)
610 518.5
Q=E XDO X1Xε
Considering the inner surface of the pipe as insulated i.e no loss for conduction, at Equillibrium Q=Q1 +Q2 Q1+Q2 HENCE,SKIN TEMP WIILL BE ,say=67 DEG C
523.6757151
176.0782287
ere is no water flow and when the inner surface of the pipe is insulated 0
C
W/m2 mm mm mm m2 0 C
W
watts watts
2 4 5.67E-08 W/m K 60.5 W/mK
Stephen boltzman constant conductivity for carbon steel
σ K
3.404728 (for laminar flow)
W/m2K
(refre page no.202, Heat and Mass Transfer by
4.331246 (for turbulent flow)
W/m2K
IS 3589
Assumed;by trial and error
Considering the upper half of the pipe surface in absorbing the radiation
l
eat and Mass Transfer by C.P Arora)
Determination of temperature of outer surface of the pipe when water is not flowing and coside Atmospheric temperature
tatm
Peak solar radiation Emissivity Pipe size Thickness of the pipe Pipe inside diameter
E ε Do
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)
t Di
1/4
h=1.24(ΔT/D)1/3
Total radiation incident on pipe surface total radiation absorbed by pipe surface
E X D0 X1
Radiation heat loss from the outer surface Q1
Q1=σεAo[(te+273)4-(tatm+273)4]
convective heat loss from the outer surface of the pipe Q2
Q2=h X Ao X(te-tatm)
E XDoX1 X ε
Q=Q1+Q2
412.9278823
Conduction heat loss assume the temperature of inside surface of the pipe is ti
105.5721177 61.9945
Conduction heat loss Qcond
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
is not flowing and cosidering heat transfer also from inner surface 0 40 C
1000 0.85 610 5.8 598.4
W/m2 mm mm mm
1.9154 m2 0 62 C
Stephen boltzman constant σ conductivity for carbon steel k IS 3589
Assumed;by trial and error 3.234798 (for laminar flow)
W/m2K
4.048203 (for turbulent flow)
W/m2K
610 W 518.5 W
73)4-(tatm+273)4]
276.6174 W 136.3105 W
W W 0 C
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
(refre page no.202, Heat and Mass Tra
2 4 5.67E-08 W/m K 60.5 W/mK
page no.202, Heat and Mass Transfer by C.P Arora)
Determination of temperature of the outer surface of a pipe when water is 0 40 C
Atmospheric temperature
tatm
Peak solar radiation
E
1000 W/m
Emissivity Pipe size Thickness of the pipe Pipe inside diameter
ε Do
0.85 610 mm 5.8 mm 598.4 mm
Pipe outer surface area considering unit length
Ao
The temperature of water flowing inside the pipe
tw
radiation incident on the pipe surface
Q=EεD0
Equilibrium temperature of the pipe
te
temperature of inner surface of the pipe is
ti
t Di
2
IS 3589
1.9154 m2 0 32 C 518.5 watts 0 32.0333 C 0 32 C
Assumed;by trial and e
Heat loss due to the conduction from outer to inner surface Qcond
[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 heatgain from at h=1.32(ΔT/Di)1/4
