Specific Heats of Gases

Specific heat is the heat needed to increase the unit weight of material via Btu/lb F (British thermal units per pound degree Fahrenheit). Specific heats of gases are needed to create connections between temperature and enthalpy of gas. Because most of materials fluctuate in pressure and volume together with variance in temperature, the specific heat of gases could be on possibly constant pressure or on constant volume.

In both solids and liquids there may be minimal variation if they're cooled or heated; on the contrary, the volume and pressure of gases can change and sizable. For that reason, there isn't any distinction in specific heats intended for liquids and solids and, in contrast to for the specific heats of gases are various on consistent volume Cv or on consistent pressure Cp.

Consistent pressure Cp is usually greater as compared to consistent volume Cv through the quantity of heat needed to perform expansion. Figure 1 shows the values of Consistent pressure Cp at consistent atmospheric pressure pertaining to a variety of steam and gases. Immediate values will probably be various from these. Pertaining to k value of diatomic gases in which k=Cp/Cv, is definitely 1.4, and k value of monatomic gases is 1.66.

Figure 1: Specific Heats of Gases Diagram
(Source: Book-Boiler for Power and Process-Kumar Rayaprolu)

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Gas Fired Boiler

Gas fired boiler is a boiler which uses gas as its fuel. Gas fired boiler consists of some important components such as flame ignition, gas metering system, air compressor, air piping, gas piping, burner nozzles, and the others. Combustion process of gas fired boiler should be maintained and operated properly to produce efficient combustion result.

The following below are several certain things which are related to gas fired boiler that must obtain specific consideration:

• The pressure of gas is important to effective combustion and good burner procedure. Abnormal pressure might result in excessive amount of carbon dioxide (CO), fuel-rich combustion, and high accumulation of soot which may decrease the efficiency of steam boiler. The troubles in gas pressure might be started from imbalances supply of gas pressure, unclean regulator of gas pressure or boiler regulator may be is not working. 

• Burner of gas fired boiler having NOx settings must has damper to adjust combustion process and the circulation of flue gas to comply with the signs from control room. The remainder of NOx and burner settings must be modified for highest NOx control at optimum performance and lowest unstable organic substance or carbon dioxide production.

• The burner operations procedure must be managed for maximum efficiency based on recommendations of boiler maker. Flame recognition units must be controlled to let lowest excessive air operation correctly.

• The air/fuel ratio must be controlled to get the best effective operation of gas fired boiler. Adjustments could be various for base-loaded boilers as in contrast to a boiler which employs load swings through a warming up or practice load. Boilers owning swinging loads may possibly not be ready to run on decreased excess air control.

• The procedure of air handle damper must be tested to ensure that it’s reacting correctly to indicators from control room.

• The nozzle of gas pressure must be proper.

• The functioning of control valve in gas flow setting must be tested to ensure that it is reacting to indicators from control room.

• Gas fired boiler which has more than one burner must has design setting operation of burner for highest efficiency in which load conditions do not need utilization of all burners forever but may be design system need some of them to be used.

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