Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

11.6 Heating Values of Fuels 335

11.6 Heating Values of Fuels

As engineers you need to know what the heating value of a fuel means. Why? Where does the energy

that drives your car come from? Where does the energy that makes your home warm and cozy dur-

ing the cold winter months come from? How is electricity generated in a conventional power plant

that supplies power to manufacturing companies, homes, and offices? The answer to all of these ques-

tions is that the initial energy comes from fuels. Most conventional fuels that we use today to gener-

ate power come from coal, natural gas, oil, or gasoline. All these fuels consist of carbon and hydrogen.

When a fuel is burned, whether it is gas, oil, etc., thermal energy is released. The heating value

of a fuel quantifies the amount of energy that is released when a unit mass (kilogram

or pound) or a unit volume (cubic meter or cubic foot) of a fuel is burned. Different fuels have dif-

ferent heating values. Moreover, based on the phase of water in the combustion product, whether

it is in the liquid form or in vapor form, two different heating values are reported. The higher heat-

ing value of a fuel, as the name implies, is the higher end of energy released by the fuel when the com-

bustion by-products include water in liquid form. The lower heating value refers to the amount of

energy that is released during combustion when the combustion products include water vapor. The

typical heating values of liquid fuels, coal, and natural gas are given in Tables 11.12 through 11.14.

TABLE 11.12 Typical Heating Values of Standard Grades of Fuel Oil and Gasoline

Grade No. Density (lb/gal) Heating Value (Btu /gal)

1 6.950 to 6.675 137,000 to 132, 900

2 7.296 to 6.960 141,800 to 137,000

4 7.787 to 7.396 148,100 to 143,100

5L 7.940 to 7.686 150,000 to 146,800

5H 8.080 to 7.890 152,000 to 149,400

6 8.448 to 8.053 155,900 to 151,300

Gasoline 6.0 to 6.2 108,500 to 117,000

Source:American Society of Heating, Refrigerating, and Air-Conditioning Engineers.

TABLE 11.13 The Typical Heating Value of Some Coal

Coal from County Higher Heating

and State of Value (Btu /lbm)

Musselshell, Montana 12,075

Emroy, Utah 13,560

Pike, Kentucky 15,040

Cambria, Pennsylvania 15,595

Williamson, Illinois 13,710

McDowell, West Virginia 15,600

Source:Babcock and Wilcox Company,Steam: Its Generation

and Use.

TABLE 11.14 The Typical Higher Heating Value of Natural Gas

Heating Value

Heating Value (Btu /ft^3 ) @ 60F

Source of Gas (Btu /lbm) and 30 inHg

Pennsylvania 23,170 1129

Southern California 22,904 1116

Ohio 22,077 964

Louisiana 21,824 1002

Oklahoma 20,160 974

Source:Babcock and Wilcox Company,Steam: Its Generation and Use.

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