Learn the API 560 method for measuring and calculating the efficiency of a fired heater.

2. Tulsa Heaters Midstream 2
FiredHeaterEfficiency
“Why is the efficiency of my
fired heater important?”
Because inefficient heaters cost you money!

3. Tulsa Heaters Midstream 3
MeasuringFired
HeaterEfficiency
This guide will teach you the
process of measuring and
calculating your heater’s
efficiency – so you can
optimize your plant and
save money.
• Based on method outlined in API 560
Annex G
• Procedure intended for fired heaters
burning liquid or gaseous fuels. Not
recommended for solid fuels.

4. Whatdowemeanby“efficiency”?

5. Tulsa Heaters Midstream 5
ThermalVSFuelEfficiency
THERMAL EFFICIENCY
- total heat absorbed divided by total heat input
FUEL EFFICIENCY
- total heat absorbed divided by heat input derived
from the combustion of the fuel only
NOTE: this definition differs from the traditional definition of fired heater efficiency, which generally refers to fuel efficiency

6. Tulsa Heaters Midstream 6
EquipmentNeeded
• Temperature-measuring devices, such as
thermocouples or thermometers, to
measure the temperature of:
• Fuel
• Ambient air
• Atomizing medium (if applicable)
• Flue gas
• Thermal fluid
• Flue-gas analytical devices to measure
oxygen and combustible gases

7. Tulsa Heaters Midstream 7
BeforetheTest
Establish and maintain operating conditions
Select and calibrate instrumentation
Perform any re-rating necessary to account for
differences between design and test conditions
Ensure fuel is acceptable for the test
Ensure heater is operating properly with respect to
the size and shape of flame, excess air & draught

8. Tulsa Heaters Midstream 8
Testing
Test procedure:
Measurements:
• The heater shall be operated at a uniform rate throughout the test
• Data shall be taken at the start of the test, and every 2 hours thereafter
• The duration of the test shall extend until three consecutive sets of
collected data fall within the prescribed limits
• Fuel gas quantity and heating value
• Flue-gas temperature and composition analysis

10. Tulsa Heaters Midstream 10
Example
Hot oil heater for gas plant Ambient air temperature: 70°F
Relative humidity: 50%
Fuel gas composition (vol%):
• Nitrogen – 1.61
• Carbon dioxide – 0.15
• Methane – 98.17
• Ethane – 0.008
Fuel gas LHV
• 20,814 Btu/lb
Fuel gas HHV
• 23,115 Btu/lb
Fuel gas temperature
• 100°F
Fuel gas pressure
• 50 psig
Excess Oxygen: 3% (dry)
Radiation heat loss: 1.5%

11. Tulsa Heaters Midstream 11
ThermalEfficiency
Where:
ℎ 𝐿 lower heating value of the fuel (Btu/lb)
∆ℎ 𝑎 heat correction due to air (Btu/lb)
∆ℎ 𝑓 heat correction due to fuel (Btu/lb)
∆ℎ 𝑚 heat correction due to atomizing medium (Btu/lb)
ℎ 𝑟 assumed radiation heat loss (Btu/lb)
ℎ 𝑠 calculated stack heat loss (Btu/lb)
𝒆 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎
× 𝟏𝟎𝟎

12. Needtosolveforallvariables

13. Step1:
solve for heat loss through the stack (ℎ 𝑠)

14. Tulsa Heaters Midstream 14
CombustionWorksheet
Fuel
Component
Column 1
Volume
fraction
%
Nitrogen 1.61
Carbon
dioxide
0.15
Methane 98.17
Ethane 0.08
TOTAL -
Total per
pound of
fuel
-
Insert fuel composition into
combustion worksheet

15. Tulsa Heaters Midstream 15
CombustionWorksheet
Fuel
Component
Column 1
Volume
fraction
%
Column 2
Relative
molecular
mass
Column 3
(1x2)
Total
mass
(lb)
Column 4
Net
heating
value
(Btu/lb)
Column 5
(3x4)
Heating
value
(Btu)
Nitrogen 1.61 28.0 0.4508 - -
Carbon
dioxide
0.15 44.0 0.066 - -
Methane 98.17 16.0 15.70 21,500 337,704.80
Ethane 0.08 30.1 0.02 20,420 491.71
TOTAL - - 16.25 - 338,196.51
Total per
pound of
fuel
- - - - 20,814.55
(5)
Calculate total mass and
heating value of fuel

16. Tulsa Heaters Midstream 16
CombustionWorksheet
Fuel
Component
Column 1
Volume
fraction
%
Column 2
Relative
molecular
mass
Column 3
(1x2)
Total
mass
(lb)
Column 4
Net
heating
value
(Btu/lb)
Column 5
(3x4)
Heating
value
(Btu)
Column 6
Air
required
(lb air/lb)
Column 7
(3x6)
Air
required
(lbs)
Column 8
CO2
formed
(lbs CO2/lb)
Column 9
(3x8)
CO2
formed
(lbs)
Column 10
H2O
formed
(lbs H2O/lb)
Column 11
(3x10)
H2O
formed
(lbs)
Column 12
N2
formed
(lbs N2/lb)
Column 13
(3x12)
N2
formed
(lbs)
Nitrogen 1.61 28.0 0.4508 - - - - - - - - - -
Carbon
dioxide
0.15 44.0 0.066 - - - - - - - - - -
Methane 98.17 16.0 15.70 21,500 337,704.80 17.24 270.79 2.74 43.04 2.25 35.34 13.25 208.12
Ethane 0.08 30.1 0.02 20,420 491.71 16.09 0.39 2.93 0.07 1.80 0.04 12.37 0.30
TOTAL - - 16.25 - 338,196.51 - 271.18 - 43.11 - 35.38 - 208.42
Total per
pound of
fuel
- - - - 20,814.55 - 16.69 - 2.65 - 2.18 - 12.83
(5) (7) (9) (11) (13)
Calculate products of
combustion for fuel

17. Tulsa Heaters Midstream 17
CompletedCombustionWorksheet
Fuel
Component
Column 1
Volume
fraction
%
Column 2
Relative
molecular
mass
Column 3
(1x2)
Total
mass
Column 4
Net
heating
value
(Btu/lb)
Column 5
(3x4)
Heating
value
(Btu)
Column 6
Air
required
(lb air/lb)
Column 7
(3x6)
Air
required
(lbs)
Column 8
CO2
formed
(lbs CO2/lb)
Column 9
(3x8)
CO2
formed
(lbs)
Column 10
H2O
formed
(lbs H2O/lb)
Column 11
(3x10)
H2O
formed
(lbs)
Column 12
N2
formed
(lbs N2/lb)
Column 13
(3x12)
N2
formed
(lbs)
Nitrogen 1.61 28.0 0.4508 - - - - - - - - - -
Carbon
dioxide
0.15 44.0 0.066 - - - - - - - - - -
Methane 98.17 16.0 15.70 21,500 337,704.80 17.24 270.79 2.74 43.04 2.25 35.34 13.25 208.12
Ethane 0.08 30.1 0.02 20,420 491.71 16.09 0.39 2.93 0.07 1.80 0.04 12.37 0.30
TOTAL - - 16.25 - 338,196.51 - 271.18 - 43.11 - 35.38 - 208.42
Total per
pound of
fuel
- - - - 20,814.55 - 16.69 - 2.65 - 2.18 - 12.83
(5) (7) (9) (11) (13)

18. Tulsa Heaters Midstream 18
RelativeHumidity
Correction for relative humidity:
where:
𝑃vapor vapor pressure of water at ambient temperature
(from steam tables)
𝑃air 14.696 psi
=
𝑃vapor
𝑃air
×
𝑅𝐻
100
×
18
28.85
moisture in air

19. Tulsa Heaters Midstream 19
RelativeHumidity
Correction for relative humidity:
where:
𝑃vapor vapor pressure of water at ambient temperature
(from steam tables)
𝑃air 14.696 psi
=
𝑃vapor
𝑃air
×
𝑅𝐻
100
×
18
28.85
moisture in air
=
0.364
14.696
×
50
100
×
18
28.85
= 0.0077 lbs of moisture per lb of air (a)

20. Tulsa Heaters Midstream 20
RelativeHumidity
Correction for relative humidity:
where:
𝑃vapor vapor pressure of water at ambient temperature
(from steam tables)
𝑃air 14.696 psi
=
𝑃vapor
𝑃air
×
𝑅𝐻
100
×
18
28.85
moisture in air
=
0.364
14.696
×
50
100
×
18
28.85
= 0.0077 lbs of moisture per lb of air (a)
=
air required
1 − moisture in air(a)
(7)
= 16.82 lbs of wet air per lb of fuel
=
16.69
1 − 0.0077
(b)

21. Tulsa Heaters Midstream 21
RelativeHumidity
Correction for relative humidity:
where:
𝑃vapor vapor pressure of water at ambient temperature
(from steam tables)
𝑃air 14.696 psi
=
𝑃vapor
𝑃air
×
𝑅𝐻
100
×
18
28.85
moisture in air
=
0.364
14.696
×
50
100
×
18
28.85
= 0.0077 lbs of moisture per lb of air (a)
=
air required
1 − moisture in air(a)
(7)
= 16.82 lbs of wet air per lb of fuel
=
16.69
1 − 0.0077
(b)
= lbs wet air per lb of fuel(b)
– air required(7)
= 0.1295 lbs of moisture per lb of fuel (c)
= 16.82 – 16.69

22. Tulsa Heaters Midstream 22
RelativeHumidity
Correction for relative humidity:
where:
𝑃vapor vapor pressure of water at ambient temperature
(from steam tables)
𝑃air 14.696 psi
=
𝑃vapor
𝑃air
×
𝑅𝐻
100
×
18
28.85
moisture in air
=
0.364
14.696
×
50
100
×
18
28.85
= 0.0077 lbs of moisture per lb of air (a)
=
air required
1 − moisture in air(a)
(7)
= 16.82 lbs of wet air per lb of fuel
=
16.69
1 − 0.0077
(b)
= lbs wet air per lb of fuel(b)
– air required(7)
= 0.1295 lbs of moisture per lb of fuel (c)
= H2O formed(11)
+ lbs of moisture per lb of fuel(c)
+
atomizing steam
= 2.31 lbs of H2O per lb of fuel (d)
= 2.17 + 0.1295 + 0
= 16.82 – 16.69

23. Tulsa Heaters Midstream 23
ExcessAir
Correction for excess air:
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
lb excess air
per lb of fuel
NOTE: If oxygen samples are extracted on a dry basis, a value of zero shall be inserted for line (e) where
a value is required from lines (c) and (d). If oxygen samples are extracted on a wet basis, the
appropriate calculated value shall be inserted.

24. Tulsa Heaters Midstream 24
ExcessAir
Correction for excess air:
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
lb excess air
per lb of fuel
NOTE: If oxygen samples are extracted on a dry basis, a value of zero shall be inserted for line (e) where
a value is required from lines (c) and (d). If oxygen samples are extracted on a wet basis, the
appropriate calculated value shall be inserted.
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
(13) (9) (d)
(c)
(7)
=
(28.85 × 3)(
12.83
28
+
2.65
44
+
0
18
)
20.95 − 3[ 1.6028 ×
0
16.69
+ 1]
= 2.50 lbs of excess air per lb of fuel (e)

25. Tulsa Heaters Midstream 25
=
lb of excess air per lb of fuel
air required
× 100
ExcessAir
Correction for excess air:
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
lb excess air
per lb of fuel
NOTE: If oxygen samples are extracted on a dry basis, a value of zero shall be inserted for line (e) where
a value is required from lines (c) and (d). If oxygen samples are extracted on a wet basis, the
appropriate calculated value shall be inserted.
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
(13) (9) (d)
(c)
(7)
=
(28.85 × 3)(
12.83
28
+
2.65
44
+
0
18
)
20.95 − 3[ 1.6028 ×
0
16.69
+ 1]
= 2.50 lbs of excess air per lb of fuel (e)
(7)
(e)
=
2.50
16.69
× 100
= 14.98 lbs excess air (f)

26. Tulsa Heaters Midstream 26
=
lb of excess air per lb of fuel
air required
× 100
ExcessAir
Correction for excess air:
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
lb excess air
per lb of fuel
NOTE: If oxygen samples are extracted on a dry basis, a value of zero shall be inserted for line (e) where
a value is required from lines (c) and (d). If oxygen samples are extracted on a wet basis, the
appropriate calculated value shall be inserted.
=
(28.85 × %O2)(
N2 formed
28
+
CO2 formed
44
+
H2O formed
18
)
20.95 − %O2[ 1.6028 ×
lbs H2O
lbs air required
+ 1]
(13) (9) (d)
(c)
(7)
=
(28.85 × 3)(
12.83
28
+
2.65
44
+
0
18
)
20.95 − 3[ 1.6028 ×
0
16.69
+ 1]
= 2.50 lbs of excess air per lb of fuel (e)
=
percent excess air
100
× lbs moisture per lb fuel + lb H2O per lb fuel
(7)
(e)
=
2.50
16.69
× 100
= 14.98 lbs excess air (f)
(f)
(c) (d)
=
14.98
100
× 0.1295 + 2.31
= 2.33 total lbs H2O per lb of fuel (corrected for excess air) (g)

27. Tulsa Heaters Midstream 27
StackLoss
Component
Column 1
Component formed
(lb per lb of fuel)
Carbon dioxide 2.65
Water vapor 2.33
Nitrogen 12.83
Air 2.50
Total 20.31
(9) from combustion worksheet
(13) from combustion worksheet
(g) from excess air worksheet
(e) from excess air worksheet

28. Tulsa Heaters Midstream 28
StackLoss
Component
Column 1
Component formed
(lb per lb of fuel)
Column 2
Enthalpy at T
(Btu/lb formed)
Carbon dioxide 2.65 100
Water vapor 2.33 192
Nitrogen 12.83 120
Air 2.50 110
Total 20.31 -
Exit flue-gas temperature, 𝑇𝑒: 500°F
Values taken from enthalpy
tables in API 560, Figures G.6
and G.7 for each flue-gas
component

29. Tulsa Heaters Midstream 29
StackLoss
Component
Column 1
Component formed
(lb per lb of fuel)
Column 2
Enthalpy at T
(Btu/lb formed)
Column 3
Heat content
(Btu/lb of fuel)
Carbon dioxide 2.65 100 265.31
Water vapor 2.33 192 446.72
Nitrogen 12.83 120 1,539.27
Air 2.50 110 274.98
Total 20.31 - 2,526.28
Exit flue-gas temperature, 𝑇𝑒: 500°F
ℎ 𝑠 = heat content at 𝑇𝑒 = 2,526.28 Btu/lb of fuel

30. Step2:
solve for additional heat losses

31. Tulsa Heaters Midstream 31
ThermalEfficiency
Where:
ℎ 𝐿 lower heating value of the fuel (Btu/lb)
∆ℎ 𝑎 heat correction due to air (Btu/lb)
∆ℎ 𝑓 heat correction due to fuel (Btu/lb)
∆ℎ 𝑚 heat correction due to atomizing medium (Btu/lb)
ℎ 𝑟 assumed radiation heat loss (Btu/lb)
ℎ 𝑠 calculated stack heat loss (Btu/lb)
𝒆 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎
× 𝟏𝟎𝟎

32. Tulsa Heaters Midstream 32
HeatLosses
Heat loss due to air:
∆ℎ 𝑎 = 𝑐 𝑝a × (𝑇𝑎 − 𝑇𝑑) × ( 𝑚 𝑎 𝑚 𝑓)
where:
𝑐 𝑝a specific heat of air
𝑇𝑎 temperature of air (°F)
𝑇𝑑 temperature of design air (°F)
𝑚 𝑎 𝑚 𝑓 the sum of 𝑚 𝑎 and 𝑚 𝑓, expressed as
pounds of air per pound of fuel (from
lines (b) and (e) on the excess air and
relative humidity work sheet)
= 𝑐 𝑝a × (𝑇𝑎 − 𝑇𝑑) × ( 𝑚 𝑎 𝑚 𝑓)
= 0.24 × (70 − 60) × (16.81 + 2.50)
∆ℎ 𝑎 = 46.37 Btu/lb

33. Tulsa Heaters Midstream 33
HeatLosses
Heat loss due to fuel gas:
∆ℎ 𝑓 = 𝑐 𝑝fuel × (𝑇𝑓 − 𝑇𝑑)
where:
𝑐 𝑝fuel specific heat of fuel gas
𝑇𝑓 temperature of fuel gas (°F)
𝑇𝑑 temperature of design fuel gas (°F)
= 𝑐 𝑝fuel × (𝑇𝑓 − 𝑇𝑑)
= 0.587 × (100 − 60)
∆ℎ 𝑓 = 23.47 Btu/lb

34. Tulsa Heaters Midstream 34
HeatLosses
Heat loss due to atomization medium:
∆ℎ 𝑚 = ∆𝐸 × ( 𝑚 𝑠𝑡 𝑚 𝑓)
where:
∆𝐸 enthalpy difference
𝑚 𝑠𝑡 mass of steam (lb)
No atomization steam in this case.
∆ℎ 𝑚 = 0

35. Tulsa Heaters Midstream 35
RadiationLosses
Heat loss due to radiation:
ℎ 𝑟 = ℎ 𝐿 × %radiation loss ℎ 𝑟 = 20,814 × 0.015
ℎ 𝑟 = 312.24 Btu/lb

36. Step3:
solve for thermal and fuel efficiencies

37. Tulsa Heaters Midstream 37
ThermalEfficiency
Where:
ℎ 𝐿 20,814 Btu/lb
∆ℎ 𝑎 46.37 Btu/lb
∆ℎ 𝑓 23.47 Btu/lb
∆ℎ 𝑚 0 Btu/lb
ℎ 𝑟 312.24 Btu/lb
ℎ 𝑠 2,526.28 Btu/lb
𝒆 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎
× 𝟏𝟎𝟎

38. Tulsa Heaters Midstream 38
ThermalEfficiency
Where:
ℎ 𝐿 20,814 Btu/lb
∆ℎ 𝑎 46.37 Btu/lb
∆ℎ 𝑓 23.47 Btu/lb
∆ℎ 𝑚 0 Btu/lb
ℎ 𝑟 312.24 Btu/lb
ℎ 𝑠 2,526.28 Btu/lb
𝒆 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎
× 𝟏𝟎𝟎
𝒆 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎
× 𝟏𝟎𝟎
𝒆 =
)𝟐𝟎, 𝟖𝟏𝟒 + 𝟒𝟔. 𝟑𝟕 + 𝟐𝟑. 𝟒𝟕 + 𝟎 − (𝟑𝟏𝟐. 𝟐𝟒 + 𝟐, 𝟓𝟐𝟔. 𝟐𝟖
𝟐𝟎, 𝟖𝟏𝟒 + 𝟒𝟔. 𝟑𝟕 + 𝟐𝟑. 𝟒𝟕 + 𝟎
× 𝟏𝟎𝟎
𝒆 = 86.4%

39. Tulsa Heaters Midstream 39
FuelEfficiency
Where:
ℎ 𝐿 20,814 Btu/lb
∆ℎ 𝑎 46.37 Btu/lb
∆ℎ 𝑓 23.47 Btu/lb
∆ℎ 𝑚 0 Btu/lb
ℎ 𝑟 312.24 Btu/lb
ℎ 𝑠 2,526.28 Btu/lb
𝒆 𝒇 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳
× 𝟏𝟎𝟎

40. Tulsa Heaters Midstream 40
FuelEfficiency
Where:
ℎ 𝐿 20,814 Btu/lb
∆ℎ 𝑎 46.37 Btu/lb
∆ℎ 𝑓 23.47 Btu/lb
∆ℎ 𝑚 0 Btu/lb
ℎ 𝑟 312.24 Btu/lb
ℎ 𝑠 2,526.28 Btu/lb
𝒆 𝒇 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳
× 𝟏𝟎𝟎
𝒆 𝒇 =
𝒉 𝑳 + ∆𝒉 𝒂 + ∆𝒉 𝒇 + ∆𝒉 𝒎 − (𝒉 𝒓 + 𝒉 𝒔
𝒉 𝑳
× 𝟏𝟎𝟎
𝒆 𝒇 =
)𝟐𝟎, 𝟖𝟏𝟒 + 𝟒𝟔. 𝟑𝟕 + 𝟐𝟑. 𝟒𝟕 + 𝟎 − (𝟑𝟏𝟐. 𝟐𝟒 + 𝟐, 𝟓𝟐𝟔. 𝟐𝟖
𝟐𝟎, 𝟖𝟏𝟒
× 𝟏𝟎𝟎
𝒆 𝒇 = 86.7%

41. * Based on $2.75/MMBtu gas price

42. Tulsa Heaters Midstream 42
Conclusion
Knowing how to check your heater’s efficiency gives you the
knowledge and power to improve your facility and optimize
your heater. As we have seen, improving efficiency can help
save your facility a lot of money.
What are you waiting for? Go check and start saving now!

43. Tulsa Heaters Midstream 43
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