In drying casein the dryer is found to consume 4 m3/h of natural gas with a calorific value of 800 kJ/mole. If the throughput of the dryer is 60 kg of wet casein per hour, drying it from 55% moisture to 10% moisture, estimate the overall thermal efficiency of the dryer taking into account the latent heat of evaporation only.
Basis: 1 hour of operation