Question

A moist air mixture with a dry bulb temperature of 48°C, a relative humidity of 40 percent, and a total pressure of 160 kPa is contained in a rigid vessel having a volume of 1.65 m. The air is cooled until the dry bulb temperature reaches 23°C. Determine the amount of heat transferred, the final pressure of the air, and the amount of water vapor condensed during the process.

Answer 1

To determine the amount of water that must condense out of the air, we can use the concept of dew point and saturation vapor density. By comparing the initial and final temperatures, we can calculate the amount of water that condenses out of each cubic meter of air. The initial and final saturation vapor densities can be obtained from Table 13.5.

Step-by-step explanation:

In order to calculate the amount of water that must condense out of each cubic meter of air, we need to use the concept of dew point. The dew point is the temperature at which air becomes saturated and can no longer hold all of its water vapor, resulting in condensation. By comparing the initial and final temperatures and using the saturation vapor density values from Table 13.5, we can calculate the amount of water that condenses out of the air.

Using the formula:

Water condensed = initial vapor density - final vapor density

we can substitute the initial vapor density from the saturation density at the initial temperature and the final vapor density from the saturation density at the final temperature. By solving this equation, we can find the amount of water that must condense out of each cubic meter of air.

In this case, the initial temperature is 25.0°C and the final temperature is 15.0°C. We can find the initial and final saturation vapor densities from Table 13.5. By substituting these values into the formula, we can calculate the amount of water that condenses out of each cubic meter of air.