NATURAL VENTILATION

Natural ventilation-

Mine Airflow caused by pressure difference between upcast & downcast shaft [Because of unequal densities of weight of air].

CASE -1 : Shaft at unequal Height.

Fig -1

• Summer - Outer air is warmer than mine air.(CE length Warmer then FA)

• FB has high density air then CD(Fig 1)

• AB - Downcast , CD - Upcast.(Fig-1)

Fig -2

• Winter - Outer air is colder(denser) than mine air .

• CE column length is colder than AF.(Fig-2)

• CD - Downcast, AB - Upcast(Fig-2).

CASE -2 : Shaft at equal height.

Flow of air will occur with difference in density or temperature of air or both between two shaft .

Factor Affecting NVP:

1. Changes of surface Temperature.

2. Effect of fan - NV happens as the Upcast air warmer and lighter then Downcast air , this is superimposed on air flow produced by fan.

• In winter - NVP assist fan .

• In summer - NVP is reduced and oppose Fan flow.

3. Flow of water in shaft.

4. Firedamp at one shaft.

5. Leakage of air from d/c to u/c.

6. Cool air circulation through d/c shaft.

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