Sources of heat

From ventilation Book

1. Name: A bubakar alghotv Reg. # : 13pwmin0679 Semester: 8 th Presentation : Sources of heat of mines.

2. Sources of heat There are eight potential sources of heat in mines These are

3. Adiabatic compression in shafts and near vertical openings Rock surrounding openings Metabolism in human beings Machinery and lights Oxidation Blasting Rock movement Head losses in air flow

4. Adiabatic compression in shafts and near vertical openings. Air entering a mine through a shaft is compressed and heated as it flows downward If no interchange in the heat content of the air takes place in the shaft,the compression occurs adiabatically(heat is constant).

5. Rock surrounding openings. The temperature of subsurface rock rises steadily with depth.(geothermal gradient) The age of rock,the formation and their properties determine the gradient. Heat inflow into the mine workings from the surroundings is a complex mechanism. Mine water is also a profile source of heat in mining workings.

6. Metabolism in human beings. Chemical and oxidation processes within the human body, termed metabolism, produce much waste heat. This is liberated from the human body into the ambient air by convection, radiation etc. The amount of heat liberated depends upon the man,s activity and environmental conditions.

7. Machinery and lights. Essentially all the inefficiency of power operated machines underground constitutes an addition of heat to the mine air, since the power losses are converted directly or indirectly to heat through friction. The heat produce by the mine lighting system and individual cap lamps is generally small, although essentially the entire electrical energy consumption of lights is converted into heat.

8. Oxidation. Oxidation processes involving the mineral and timber in mines contribute heat to the mine air. In coal mine, this may constitute 80% to 85% of the total load. In ore mines having a high sulfide content, the addition of heat may also be very great. The amount of heat generated by oxidation is difficult to determine.

9. Blasting. Since over half of the energy created by the detonation of a high explosive is liberated in the form of heat. Blasting is usually a very significant cause of temperature rise in the mine air. The exact amount of heat added to the mine air cannot be calculated directly, since some is absorbed by the rock.

10. Rock movement. Movement of ground due to the geologic causes or mining subsidence is another heat source which is difficult to determine. Caving or collapse of waste is the most common cause of heat liberation due to ground movement. Some theoritical determinations have indicated that in coal mines, rock movement may account for about 10% of the total heat produced.

11. Head losses in air flow. All friction and shock losses which must be overcome in mine air flow, convert energy into heat. Essentially all the static horsepower of moving air is converted into heat.

12. Thank you