Surface Environment, Mine Ventilation and Underground Hazards · Mine Ventilation · 2 marks · Numerical answer
An underground AC plant needs 250 US gpm of water at 7°C; 15.85 US gpm equals 1 L/s. Ice at 0°C (latent heat 334 kJ/kg) is mixed with 20°C water (specific heat 4.18 kJ/kg°C) and transported adiabatically. Find ice demand in tonnes/hour, to two decimals.
Total delivered mass flow is 250/15.85=15.77287 kg/s, taking water density as 1 kg/L. If mi is ice flow and M total flow, heat balance is (M−mi)4.18(20−7)=mi[334+4.18×7]. Rearranging gives mi/M=4.18×13/(334+4.18×20)=0.1301245. Ice flow is about 2.0524 kg/s, or 7.39 tonnes/hour. Melted ice is part of the final delivered water.
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