[scottlawsonbc]

I am a student who has been working on a project for some months now. Unfortunately I can't fully reveal the details of the prototype I am working on, but I can offer this.

My device involves the dew point of water in a sealed environment. The dew point of a parcel of air is dependent on the temperature and relative humidity of the parcel. It can be calculated using a dew point calculator. Basically I can seal a container with X% relative humidity and X temperature and be able to calculate exactly what point that water vapour will condense.

The problem is, my device works, but needs to be scaled down and the absolute humidity (total moles of water available) isn't high enough. Water vapour simply doesnt make up enough of the air to work at lower dew points.

I know that water vapour makes up roughly ~1-2% of dry air. I am trying to get that percentage much much higher, without affecting the dew point. In other words, given a constant volume, if I need a dew point at say, 4 degrees C, I need the yield of absolute humidity to increase.

Air is a mixture of many gasses, nitrogen, oxygen etc etc. Water vapour is just one of these. Is it possible to replace the other gasses in the system with almost 100% water vapour, but keep it at the same partial pressure as the 2% water vapour? Would this keep the dew point constant, but increase the condensation yield?

If it is possible to do this, another problem is having a method capable of achieving this in a labratory setting, but without expensive equipment. I need to be able to do this with relatively inexpensive instruments (not costing $1000+ dollars).

As I said earlier, my device works, but I am missing that last drop of water I need to make it really work. I can't reveal what I need the water vapour for but it basically comes down to me needing a box the size of an altoids tin to be able to condense as much water vapour as possible, at low dew points.

I would appreciate any help in coming up with a method for doing this.

[Borek]

Is it possible to replace the other gasses in the system with almost 100% water vapour, but keep it at the same partial pressure as the 2% water vapour?

Not clear to me what you mean, but if I understand you correctly - no. If you replace a gas with water, partial pressure of water must go up.

[scottlawsonbc]

Is it possible to replace the other gasses in the system with almost 100% water vapour, but keep it at the same partial pressure as the 2% water vapour?

Not clear to me what you mean, but if I understand you correctly - no. If you replace a gas with water, partial pressure of water must go up.

Sorry, I got this wrong. I mean that if I create a 100% water vapour environment, at the same atmospheric pressure as a mixed system (say, 1atm of pressure), could I increase the specific humidity without having to raise the dew point?

[Borek]

Still not clear to me what you trying to do. Dew point is a function of partial pressure of water. If you do anything that will change partial pressure of water, you will change the dew point.