Problems
5 1
3.2. On a hot, humid day your skin surface can be at 36" C and covered
with perspiration. If the perspiration has the same vapor pressure as
pure water, what is the vapor pressure at your skin surface?
3.3. You decide to calibrate a relative humidity sensor at a value of 0.5 in
a 0.1 m
3 container. Assuming no water is adsorbed on the walls of
the container, how much liquid water must be evaporated into dry air
to achieve this humidity at container temperatures of 10 and 40" C?
3.4. The method in problem 3.3 is not very useful for calibrating humidity
sensors. A better method is to bubble air through water at controlled
temperatures. Suppose air is bubbled through water at 10" C, and
then passed into the container with the humidity sensor, which is at
20" C. What is the relative humidity of the air in the chamber? If the
air and humidity sensor were really at 2 1" C when you thought they
were at 20" C, how much error would this cause in your calibration?
3.5. If the outdoor minimum temperature were -15" C on a particular
day, estimate the relative humidity in a 22" C laboratory on that day.
3.6. The vapor pressure of the air you breathe out is the saturation vapor
pressure at body temperature (37" C). If the air you breathe in is at
20" C and 0.2 relative humidity, you take 15 breaths per minute, and
each breath has a volume of 1 liter, how many 250 ml. glasses of
water are required per day to replenish this water loss?
3.7. If air is at 15" C and 0.6 relative humidity, find the absolute humidity
(or vapor density), the specific humidity, and the mixing ratio.
5 1
3.2. On a hot, humid day your skin surface can be at 36" C and covered
with perspiration. If the perspiration has the same vapor pressure as
pure water, what is the vapor pressure at your skin surface?
3.3. You decide to calibrate a relative humidity sensor at a value of 0.5 in
a 0.1 m
3 container. Assuming no water is adsorbed on the walls of
the container, how much liquid water must be evaporated into dry air
to achieve this humidity at container temperatures of 10 and 40" C?
3.4. The method in problem 3.3 is not very useful for calibrating humidity
sensors. A better method is to bubble air through water at controlled
temperatures. Suppose air is bubbled through water at 10" C, and
then passed into the container with the humidity sensor, which is at
20" C. What is the relative humidity of the air in the chamber? If the
air and humidity sensor were really at 2 1" C when you thought they
were at 20" C, how much error would this cause in your calibration?
3.5. If the outdoor minimum temperature were -15" C on a particular
day, estimate the relative humidity in a 22" C laboratory on that day.
3.6. The vapor pressure of the air you breathe out is the saturation vapor
pressure at body temperature (37" C). If the air you breathe in is at
20" C and 0.2 relative humidity, you take 15 breaths per minute, and
each breath has a volume of 1 liter, how many 250 ml. glasses of
water are required per day to replenish this water loss?
3.7. If air is at 15" C and 0.6 relative humidity, find the absolute humidity
(or vapor density), the specific humidity, and the mixing ratio.