58
2 Environmental Conditions in the Mine
where
• q: Heat released per unit time (kJ s
−1 ).
• C: Fuel consumption (l s
−1 ).
• PC: Diesel fuel calorific value. An approximation may be 34,000–38,000 kJ l
-1
of fuel.
• E: Efficiency of combustion. In this case, the heat released is less than the theoretical heat due to dissociation and lack of oxygen. Combustion efficiency is around
90–97%.
Some authors suggest that the heat released by a diesel engine is between 2.8
and 3 kW per kW of the equipment’s effective power (Banerjee 2003; Calizaya and
Marks 2011). These values are based on a consumption of 0.24 kg of fuel per kW of
power, with a calorific value of 44 MJ kg
−1 (Vutukuri and Lama 1986).
The quantity of heat released and the increase in air temperature caused are not
directly correlated. This is because not all this heat will pass into the air, nor will all
of it be released at the same time. In fact, dissipation of the heat can be very slow.
This is why some authors fix this value at 0.9 kW (kW power )
−1 . The method proposed
by McPherson (1993a) to estimate air temperature increase due to working diesel
engines (based on hours as the time unit) is:
1. Approximate the total rate of heat flow (Eq. 2.17):
q T =
C PC
3600
(2.17)
where
• q T : Total heat released per unit time (kW),
• C: Fuel consumption (l h
−1 ), and
• PC: Diesel calorific value (kJ l
−1 ).
2. Subtract from the previous rate of heat flow, the rate of heat flow used to increase
the potential energy of bodies and fluids (Q p ) (Eq. 2.18):
q
T = q T − q p
(2.18)
3. Estimate the rate of latent heat flow by means of Eq. 2.19:
q L =
V H 2 O L H 2 O
3600
(2.19)
where
• q L : Latent heat per unit time (kW),
• V H 2 O : Water volume produced per unit time (l h
−1 ), and
2 Environmental Conditions in the Mine
where
• q: Heat released per unit time (kJ s
−1 ).
• C: Fuel consumption (l s
−1 ).
• PC: Diesel fuel calorific value. An approximation may be 34,000–38,000 kJ l
-1
of fuel.
• E: Efficiency of combustion. In this case, the heat released is less than the theoretical heat due to dissociation and lack of oxygen. Combustion efficiency is around
90–97%.
Some authors suggest that the heat released by a diesel engine is between 2.8
and 3 kW per kW of the equipment’s effective power (Banerjee 2003; Calizaya and
Marks 2011). These values are based on a consumption of 0.24 kg of fuel per kW of
power, with a calorific value of 44 MJ kg
−1 (Vutukuri and Lama 1986).
The quantity of heat released and the increase in air temperature caused are not
directly correlated. This is because not all this heat will pass into the air, nor will all
of it be released at the same time. In fact, dissipation of the heat can be very slow.
This is why some authors fix this value at 0.9 kW (kW power )
−1 . The method proposed
by McPherson (1993a) to estimate air temperature increase due to working diesel
engines (based on hours as the time unit) is:
1. Approximate the total rate of heat flow (Eq. 2.17):
q T =
C PC
3600
(2.17)
where
• q T : Total heat released per unit time (kW),
• C: Fuel consumption (l h
−1 ), and
• PC: Diesel calorific value (kJ l
−1 ).
2. Subtract from the previous rate of heat flow, the rate of heat flow used to increase
the potential energy of bodies and fluids (Q p ) (Eq. 2.18):
q
T = q T − q p
(2.18)
3. Estimate the rate of latent heat flow by means of Eq. 2.19:
q L =
V H 2 O L H 2 O
3600
(2.19)
where
• q L : Latent heat per unit time (kW),
• V H 2 O : Water volume produced per unit time (l h
−1 ), and