Relative Humidity and Vaporization

In summary, the problem involves calculating the amount of water needed to saturate air at 98.6 degrees F, assuming all moisture is exhaled, and the heat loss in kilocalories. Using the given information and equations, it can be determined that 14,400 liters of air are breathed per day, and the saturation vapor pressure at 20 degrees C is 16.3 g/m cubed. The heat loss in kilocalories is also calculated. The final solution involves finding the molecular mass and partial pressure, and using the ideal gas law to determine the volume increase of the air after saturation.
  • #1
klutchshot
2
0

Homework Statement



If a person breathes 10 liters per minute of air at 68 degrees F and 50% relative humidity, how much water per day must the internal membranes supply to saturate the air at 98.6 degrees F. (assume all the moisture is exhaled) If each gram of water extracts 580 calories as it is vaporized, how much daily heat loss in kilocalories (food calories) does this represent? (Saturation vapor pressure at 20 degrees C is 16.3 g/m cubed and at 37 degrees C is 44.0 g/m (grams per cubic meter)


Homework Equations



What I have done...

l0 liters / min = 600 l / hr = 14,400 l /day

68 F = 20 C & 98.6 F = 37 C

580 cal / g @ 20 C = 25520 cal/m or 25.520 kcal / m

580 cal / g @ 37 C = 10034 cal / m or 10.034 kcal / m

*water has about 1000 grams in a liter*

Inhale 50% of 17.3 = 8.65 g/m

Exhale 100% of 44 g/m

Relative Humidity = content of moisture / capacity

The Attempt at a Solution



I converted most of the equations above so I can use the right units without converting later on.

I know the volume needed to so call humidify the air is 44 - 8.65 since you half the inhaled air which results in 35.35.

I think I use molecular mass * partial pressure ( not sure what it is ) / ( R * Temp in Kelvins )

I find R with

PV / nT = R

Do I only have 1 atm of pressure and 1 mol?

Any guidance is great - thanks.
 
Physics news on Phys.org
  • #2
The saturation var pressure @ 20 degrees is 16.3 and not 17.3.
the rest of your calculations are OK.

Because you heat the air it expands. I think it expands after saturating it, so you
don't have to calculate the volume increase.
 
  • #3
The problem gives it to be 17.3 g / m

=/

But interesting idea for the Volume thanks.
 

1. What is relative humidity?

Relative humidity is the amount of water vapor present in the air compared to the maximum amount of water vapor that the air can hold at a particular temperature and pressure. It is expressed as a percentage and is an important factor in determining the comfort level and potential for precipitation in a given area.

2. How is relative humidity measured?

Relative humidity is typically measured using a device called a hygrometer. This instrument uses a combination of temperature and pressure sensors to determine the amount of water vapor in the air. The resulting measurement is then compared to the maximum amount of water vapor that can be held at that temperature and pressure to calculate the relative humidity percentage.

3. What factors affect the relative humidity?

The relative humidity is affected by the temperature and pressure of the air, as well as the amount of water vapor present. As temperature increases, the air can hold more water vapor, leading to a decrease in relative humidity. Conversely, as temperature decreases, the air can hold less water vapor, leading to an increase in relative humidity. Changes in pressure can also impact the amount of water vapor that the air can hold.

4. What is vaporization?

Vaporization is the process by which a liquid is converted into a gas or vapor state. This occurs when the temperature of the liquid reaches its boiling point and enough energy is added to overcome the attractive forces between the liquid molecules. Vaporization can occur naturally through evaporation or artificially through methods such as boiling or using a vaporizer.

5. How does relative humidity affect vaporization?

The relative humidity can affect the rate of vaporization. When the relative humidity is low, there is less water vapor present in the air, so the air can absorb more moisture from the liquid, leading to a faster rate of vaporization. When the relative humidity is high, the air is already saturated with water vapor, so the rate of vaporization will be slower. This is why clothes dry faster on a dry, low-humidity day compared to a humid day.

Similar threads

  • Introductory Physics Homework Help
Replies
3
Views
916
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
4K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
24
Views
2K
  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
2K
Back
Top