W = Work required Q = Heat to be pumped taken at T2 T1, T2 = Absolute temperature levels
If T0 is the ambient temperature, the following equation describes the ideal freezing process:
If 50% of the water from a 3.5% NaCl solution is removed as pure water, the concentrated waste contains 7% NaCl. The minimum (theoretical) energy requirement for such a process is about 6.3 kWh per 1000 gal. Actual values are far higher because of process inefficiencies.
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