General information Useful calculation data
7
Terms
Units
Definitions
A
m 2
Area of heating surface
C p
kJ / kg °C
Specific heat capacity of substance
T 1
°C
Initial (or inlet) temperature of substance
T 2
°C
Final (or outlet) temperature of substance
T a
°C
Ambient temperature
T 1 + T 2 2
T m
°C
Mean temperature of heated substance
T s
°C
Steam temperature
Temperature rise of heated substance T 2 - T 1
°C
D T
°C
Temperature difference between steam and substance at start-up T s - T 1
D T s
Mean temperature difference between steam and substance at any heat load
AMTD = Arithmetic Mean Temperature Difference AMTD = T S - T M
7.5 27
°C
D T m
(T S - T 1 ) - (T S - T 2 ) Ln [(T S - T 1 ) / (T S - T 2 )]
LMTD = Logrithmic Mean Temperature Difference LMTD =
f
dimensionless
Insulation factor
H
hours
Time in hours
h fg
kJ / kg
Enthalpy of evaporation
K vr
m
3 / h bar
The required capacity index
K vs
m
3 / h bar
The valve capacity index (full open valve)
Table continued on next page
TI-GCM-13 CM Issue 3
Page 3 of 4
Heating formulas
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