[Gooserider]

TerraMex: No , i think you're wrong on several issues.
But i (and Blade does too) do appreciate the input. Let the hostility begin .

fair enough.

Quote: (GR)Your chart describes the dew point, or what temperature condesation will occur at if the air is FULLY SATURATED with moisture.
(TM)If it's fully saturated then it has a relative humidity of 100%. That's the definition of fully saturated.
That's not what the chart means. It means that at a given relative percentagem of humidity, to diferent temperatures, when the condensation will occur. It doesnt have to be fully saturated.

Hmmm, I didn't make myself very clear on that one. I should have said that at the dew point, the air immediately adjacent to the condensor would be saturated, assuming ambient temp and relative humidity as stated in the chart. In essence there is a mini-convection flow, where the air next to the condensor cools to the dew point where it reaches saturation, moisture condenses out and the air flows back into the ambient space, where it warms back up....

Quote: (GR) At least at the temperatures we are talking about (~10-60*C) cold air can hold less water vapour than hot air.
(TM)That's one of the main points. But it's harder for a cold air to release the one it has, if it's a low value of relative humidity, to another cold point (relative cold). The delta T needs a minimum value.

Sort of, but it's not a question of Delta T, but rather that cold air at a low relative humidity(RH) has a lower dew point.

Quote: (GR) Thus if you take a given volume of air, and evaporate a specific amount of water into it, when you heat the air, it's relative humidty will DROP, and so will the dewpoint. If you cool the air, then it's relative humidity goes UP, along with it's dewpoint.

(TM)If you have a given volume of air, with a given percentage of water vapor, if you evaporate an extra quantity of water vapor, then, for the same temperature, it will have a higher dew point. See the chart.

Correct, but not what I said... Assume a box full of dry air (0% RH) Evaporate water into it until saturation is reached. Measure the amount (mass) of water used. The amount of water needed to reach saturation will be a function of temperature, at lower temps less water is needed, at higher temp more water is.

Assume the box has been saturated (100% RH) at 20*C. If the temp is raised to 30*C, (and no more water is added) the relative humidity in the box would be less. If the temp is dropped to 10*C you will get condensation, and the air would still be at 100% RH.

(TM)When you increase the temperature , for the same humidity level the dew point will increase. This goes against what we want.
We want to remove some humidity and maintain a cool temperature. If a good deal will precipitate on the rad, then , the air (still relatively cool) that goes through the case will have less humidity and lower dew point. See the chart. And that's what we want.
But I'm assuming the rad is very efficient on doing that.

Agreed completely, except that I'm not sure the rad would do well enough.

{Cloud physics discussion clipped, IMHO we were both saying the same thing, I just wasn't getting as deep into the details...)

Quote: (GR)
Now as it applies to your design proposal, what you seem to be trying to do as I understand it, is cool the air entering the case, without changing the amount of water vapour that it's carrying other than possibly having some condensation on the incoming air radiator (which really won't help much).

(TM)Cool it and create condensation. Not one or two. Both. Both will change the dew point considerably (Bladerunner hopes). Assuming it can change by a large percentage, both the relative humidity and the temperature. But it's a big IF.

Well, cooling without condensation will RAISE the RH, and bring the dewpoint closer to the temperature of the cooled air. Cooling with condensation will lower the amount of water vapour in the cooled air, but that air will still have a high RH (because of it's low temperature) as long as it isn't warmed back up.

QuoteGR) Assumptions - per your previous posts, and my guestimates...
(TM)Wrong assumptions, assume BladeRunners numbers.
Assume a 20º C ambient , average.
8ºC or less at radiator (or even average 10ºC). No forced air.
The issue is how much the temperature drops as it passes the rad.
And how much a drop of relative humidity.

From one of BR's earlier posts in this thread (highlight added)

BladeRunner:
My system will be cooled by an underground tank the rad will do nothing for the cooling except raise the coolant temp a small amount before it goes back to the tank. At the moment all the blocks in my system add under 1C to the coolant temp in one pass. This might increase to 2C or 3C with Tecs. So if I add this air "conditioner" rad, in the loop, (after its been through the blocks), it will get around 3C warmer coolant than enters the PC, so about 12C is my guess.
The plan is to build an improved underground cooler that will cope with the Tec's and not heat up at all, (probably a large run of copper pipes buried instead of a tank). Assuming I can build a truly effective ground cooler this time, (and It's going to be very large trust me ), then it will return the coolant to the PC completely re-cooled to between 8C to 10C )

Thus, 10*C @blocks, 12*C at rad assuming conservative values for his numbers. (not that it makes a big difference)

Quote:
But wait! you say, wouldn't there also be condensation on the rad?
On the contrary, for me anyway, as stated. You misread. I stated condensation will occur, probably. Again, depends on the rad.

But honestly, if the rad reduced enough the temperature of the rising air, it will be suficient to avoid any type of condensation without tampering with the relative humidity. Given the chart that is.

And you forget that Bladerunner stated that the cooling loop will be cooling pelts, so the water wont be that cold, and the interior wont need very low temps.

My assumption was also that there would be condensation, but that the air coming out of the radiator would be cooled and still have a high RH because of it's low temperature, which would NOT be as low as the cold side of the pelts. Thus the CPU area could still be below the dew point which would not have dropped significantly.

In my proposed modification; which locates the rad > airbox > chimney assembly below the computer box, and supplying the airflow to it; I am assuming that the air would be cooled and condensed by it's passage through the rad, just as you are. I am also assuming some drain or equivalent to get rid of the condensate. But I am suggesting that the air should then pass through the chimney so that it is warmed back up to ambient (or slightly above, but not grossly so - this would need some design tweaking) thus greatly lowering it's RH, and therefore the dewpoint.

This is exactly the same process that a regular de-humidifier uses, except that it eliminates the fans and other motorized bits per the Zero-Fan-Zone spec.

I would be tempted to draw more ASCII art to show what I mean, but the new rev doesn't preserve it properly.

Gooserider