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ing the heating of the kettle itself.

We must first heat the milk from 80°F to 212°F (sensible heating) and then evaporate off 0.25 x 1500 = 375 lb of water.

From Table 6.7, the specific heat of milk is 0.90 Btu/lb °F. The sensible heat requirement is, therefore,

In addition, we must provide the latent heat to vaporize 375 lb of water at 212°F. From Table 6.2, 970.3 Btu/lb is required. The total latent heat is, therefore,

375 x 970.3 = 363,863 Btu/batch and the total heat input is

363,863 + 178,200 = 542,063 Btu/batch

This heat must be supplied as the latent heat of 15-psig steam, which, from Table 6.2, is about 945 Btu/lb. The total steam requirement is, then,

542,063 Btu/batch

- = 574 lb of 15-psig steam per batch

945 Btu/lb

We could have also determined the startup requirement to heat the steel kettle, if we could estimate its weight, using the specific heat of 0.12 Btu/lb °F for steel, as shown in Table 6.7.

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