Wednesday, March 21, 2007

HW #2, P8- Relative Humidity and Fogged Glasses - 5 pts

Please post any questions or discussion related to this problem as comments on this message. Feel free to answer other students' questions. I will check the blog M-F and once on the weekend.
Dr. B

2 comments:

Anonymous said...

other than by stating the equation for relative humidity, i have no clue as to how to approach this question. please help. thanks!

Dr. B said...

y:
The key to this problem is to assume that the glasses are at 10oC when they come in from the outdoors and to recognize that if the dew point of the indoor air is GREATER THAN 10oC, then when the humid air hits the cold glasses, water will condense onto the glasses and they will "fog". Since the glasses did not actually fog, we know that the dew point temperature of the humid air in the house is LESS THAN 10oC. So, we can calculate Tdew of indoor air at hr = 55% and compare to 10oC to see if the 55% relative humidity is possibly correct in light of the fact that the glasses did not fog.