Final answer:
To determine the heat transfer necessary to maintain constant temperature in a tank of water when half the mass is withdrawn, one must use the latent heat of vaporization at 120°C along with the volume of the tank and the specific volume of saturated water at 120°C.
Step-by-step explanation:
To calculate the heat transfer when a 0.18-m³ rigid tank filled with saturated liquid water at 120°C has half of its mass withdrawn and is kept at constant temperature, we need to use properties of water at this temperature. To maintain the temperature of the remaining water while half the mass is withdrawn, the latent heat of vaporization must be transferred to the water, because as the water is withdrawn, some of it will vaporize to maintain constant pressure.
First, we must find the mass of the water in the tank using the specific volume of saturated liquid water at 120°C. Next, we determine the amount of heat required using the latent heat of vaporization.
However, the question does not provide the specific properties of the water (specific volume and latent heat of vaporization) at 120°C, which are necessary to perform the calculation. Assuming the student has access to these properties from a steam table or database, they can perform the calculation with the following steps:
Find the specific volume of saturated liquid water at 120°C.
Calculate the mass of the water in the tank using the tank volume and the specific volume of the water.
Determine the mass of water remaining after half is withdrawn.
Use the latent heat of vaporization of water at 120°C to calculate the heat transfer needed to account for the mass that vaporizes to maintain constant pressure.