Steam at 100°C enters a radiator and leaves as water (at 80°C).Take the heat of vaporization to be 540 cal/g.Of the total energy given off as heat, what percent arises from the cooling of the water?

Question

Quizplus · Accepted Answer

The energy given off as heat includes both the heat of vaporization and the heat released from cooling the water from 100°C to 80°C. The heat of vaporization accounts for the majority of the energy released. The specific heat of water is approximately 1 cal/g°C, so cooling water from 100°C to 80°C releases 20 cal/g. Compared to the 540 cal/g for vaporization, the cooling contributes a small fraction: (20 / (540 + 20)) * 100% = 3.6%.

Steam at 100°C Enters a Radiator and Leaves as Water