Chapter 1, Problem 1.68P

Following the hot vacuum forming of a paper-pulpmixture, the product, an egg carton, is transported on aconveyor for 18 s toward the entrance of a gas-firedoven where it is dried to a desired final water content.Very little water evaporates during the travel time.So, to increase the productivity of the line, it is proposed that a bank of infrared radiation heaters, whichprovide a uniform radiant flux of $\text{5}000\text{ W}/{\text{m}}^{\text{2}}$ , beinstalled over the conveyor. The carton has an exposedarea of $0.0{\text{625 m}}^{\text{2}}$ and a mass of 0.220 kg, 75% of which is water after the forming press.

The chief engineer of your plant will approve the purchase of the heaters if they can reduce the water contentby 10% of the total mass. Would you recommend thepurchase? Assume the heat of vaporization of water is $h_{fg}=2400\text{kJ}/\text{kg}$ .