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NORA Oilheat Technicians Manual

Chapter 7 Combustion Chapter 7 Combustion Heat Energy to Load 119,000 Btuh Heat Energy Loss Up Chimney (Stack Loss) 21,000 Btuh Heat Energy Chapter 7—Combustion 7-3 Combustion theory As a technician, you have an obligation to assure the equipment you are working on is operating at peak performance levels. Understanding combustion theory is the basis for adjusting oilburners for safe, clean, reliable, and economical operation. Combustion is a controlled chemical reaction Three things are needed to make a fire: oxygen, ignition, and fuel. When heating oil is burned, the chemical energy in the fuel is converted to heat. The oxygen required for combustion comes from the air that is delivered by the oilburner fan. The spark delivered by the electrodes provides the heat needed to start the combustion process. The heat from the spark vaporizes the oil droplets delivered by the nozzle then lights the vapor on fire. If the conditions for combustion are right, this process continues until all the droplets vaporize and burn completely and cleanly within the combustion zone. Combustion is the rapid oxidation of any material that will combine readily with oxygen. The resulting flame contains the hot gases produced when the hydrogen and carbon in the fuel react and combine with the oxygen in the air. This reaction creates light, and releases large quantities of heat. This heat from the combustion gases is extracted by the heat exchanger in the furnace, boiler, or water heater, and heats the air, water, or steam we use for space and domestic water heating. Every gallon of oil contains about 140,000 Btus per gallon. A Btu is the energy required to raise one pound of water one degree Fahrenheit—about the amount of energy contained in a birthday candle flame. In a typical oil-fired appliance, every gallon of oil burned puts about 119,000 Btus into the building and about 21,000 Btus go up the chimney. Figure 7-1. Heating oil is 85% carbon and 15% hydrogen. These fixed ratios of hydrogen and carbon in the fuel combine with a specific quantity of oxygen to form combustion gases. Therefore a precise Figure 7-1: Heat loads, heat loss Heat to Load = Heat Energy Input - Stack Loss Input 140,000 Btuh


NORA Oilheat Technicians Manual
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