Water is boiled at 1 atm pressure in a 20-cm-internal diameter polished copper pan on an electric range. If it is observed that the water level in the pan drops by 8.00 cm in 15 minutes, determine the inner surface temperature of the pan.

11.3298W

Explanation:

The rate of heat transfer is determined from the enthalpy of vaporization at the give pressure obtained and the mass flow rate. The mass flow rate is determined from the volume of the boiled water, the given time interval and the specific volume of the saturated liquid.

Given that

1atm as the atmospheric pressure

Internal diameter = 20cm = 0.2m

Time = 15mins = (15×60)secs

Latent heat of vaporization (hevap) = 2256.6

Q = mh(evap)

= m/∆t . hevap

= V/αliq∆t ×h(evap)

D^2π∆h/4αliq ∆t × hevap

= 0.2^2 ×π×0.8×2256.5/4×0.001043×15×60

=0.04×3.142×0.08×2256.6/2.00256

= 22.68876/2.00256

Q = 11.3298W

c. magnitude and direction