CEMP-E
TI 810-32
10 January 2002
APPENDIX C
CONDENSATION LOAD CALCULATIONS (NORMAL)
Step #1 Determine the heat loss per foot of line.
Q = 2? (Tst - Tout)/(ln(ro/ri )/kp + ln(rio /ro) /kin + 1/3r io)
Assumptions. This equation models an insulated pipe surrounded by air. The convective
resistance between the insulation and the outside of the pipe is assumed to be negligible. Also,
the convective heat transfer coefficient outside of the insulation is assumed to be 3 BTU/hr-ft2
deg. F.
Step #2 Determine the flow of condensate from the heat loss calculated in step #1.
m = Q/(hst - hcon)
Step #3 Multiply the flow rate per foot, calculated in step #2, by the total number of feet of steam
line that slopes toward the trap in question. The result is the minimum flow capacity of the trap.
where:
Q
= heat loss per foot of pipe; Btu/hr-ft
Tst
= temperature of steam; deg. F
Tout
= temperature of ambient conditions; deg. F
ro
= outside pipe radius; feet
ri
= inside pipe radius; feet
rio
= outside insulation radius; feet
kp
= thermal conductivity of pipe; Btu/hr-ft- deg. F; (26 Btu/hr-ft-deg. F for steel)
kin
= thermal conductivity of insulation; Btu/hr-ft- deg. F * (see table below)
m
= mass flow rate of condensate; lbm/hr-ft
hst
= enthalpy of saturated steam; Btu/lbm
hcon
= enthalpy of condensate; Btu/lbm
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\ *K-value (Btu/hr-ft-deg. F /1/
Insulation Type
400 deg. F
300 deg. F
200 deg. F
Mineral Fiber
0.034
0.029
0.024
Calcium Silicate
0.042
0.038
0.035
C-1
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