Question

A 40-cm-long, 800-W electric resistance heating element with diameter 0.5 cm and surface temperature 120°C is immersed in 75 kg of water initially at 20°C. Determine how long it will take for this heater to raise the water temperature to 80°C. Also, determine the convection heat transfer coefficients at the beginning and at the end of the heating process.

Answer 1

Answer: the convection heat transfer coefficient at the beginning of the heating process is approximately 5.137 W/(m^2K), and at the end of the heating process, it is approximately 6.103 W/(m^2K). The time required to raise the water temperature from 20°C to 80°C is approximately 23583.75 seconds (about 6.55 hours).

Step-by-step explanation:

Answer 2

The coefficients convection heat transfer of the beginning and the end of the heating process is 1590•909091 w/n2 x “ c