Homework SourseWater is to be boiled at sea level in a 30cmdiameter mechani
Water is to be boiled at sea level in a 30-cmdiameter mechanically polished AISI 304 stainless steel pan placed on top of a 3-kW electric burner. If 60 percent of the heat generated by the burner is transferred to the water during boiling, determine the temperature of the inner surface of the bottom of the pan. Also, determine the temperature difference between the inner and outer surfaces of the bottom of the pan if it is 6 mm thick. (ks.s = 14.9 W/m-K)
Solution
Answer :
Power supplied = 3 kW
Power transferred to the water during boiling = 60% of 3 kW = 1.8 kW
To convert water into steam, heat supplied = Q = mL, where L = Latent heat of vaporization.
“The specific latent heat of vaporization is the amount of heat required to convert unit mass of a liquid into the vapour without a change in temperature.\"
For water at its normal boiling point of 100 ºC, the latent specific latent heat of vaporization is 2260 kJ.kg-1. This means that to convert 1 kg of water at 100 ºC to 1 kg of steam at 100 ºC, 2260 kJ of heat must be absorbed by the water.
Assume a time period of 1 s.
Then, 1.8*1 = m*2260
Therefore, m = 1.8/2260 = 7.97*10-4 kg/s = 0.797 grams/s
