My swamp cooler / box fan . . . review

[Tockk]

I bought one of these a while ago:

about 1/3 off, and it's been rainy and humid here in the Dallas area for the past while. Haven't had the chance to use it until yesterday, when it was hot and 33% humidity (according to the TV weatherman).

I fired it up, and used a thermometer to read the temperature of air going in vs. air coming out. In my apartment, it read 95 degrees going in to the fan, and 84 coming out of the fan. Not bad. As far as ability to cool a room, well, it's limited. I have two windows seperated by about 6 feet of wall space. I put the cooler-fan in front of one window, and I have another fan in the other window that pushes the air to the outside. It's pretty good if you get right in front of the airflow, but anywhere else in the room, you won't feel much relief. It's also somewhat noisy; it took a little getting used to on the slow speed. I doubt most people would want to deal with the high speed--too noisy.

At night, it dropped the temperture 10 degrees F, from 90 F to 80 F.

All in all, it's ok . . . I've gotten used to sleeping in 80 degree heat (no covers), and it provided sufficient relief to give a restful night sleep. What's nice is the $$$ I saved from not running the AC. Using this thing for 30 days will save me around $2 a night, or $60 a month. It'll pay for itself in less than 2 months, and it'll be gravy after that.

It holds a few gallons of water, which isn't enough for an 8 hour run. I'll probably add a 5 gallon water bottle held upside down, with a feeder tube so that it fills up the fan's resovoir when it runs low. That ought to fix that problem . . .

If it starts to rain again like it had been up through July, I'll just use the fan by itself, and that should be ok.

--Just some notes on this thing . . . FYI . . .

[nicksanspam]

for about 1/3 off, and it's been rainy and humid here in the Dallas area for

The ASHRAE 55-2004 comfort standard says that's very hot, with a predicted mean vote of 3.07 on a scale of -3 (very cold) to 0 (perfectly comfortable) to +3 (very hot.)

T (C) RH% Clo PMV PPD%

35 33 .5 3.07171 99.38564

The standard predicts that 99.38564% of people surveyed would be dissatisfied.

The web site says it moves 415 cfm, and 1 Btu/h can cool 1 cfm about 1 F and 1000 Btu can evaporate 1 pound of water, so you were cooling the air by about 415(95-84) = 4565 Btu/h with about 4.565 pounds per hour of water.

With an outdoor vapor pressure Po = 0.33e^(17.863-9621/(460+95)) = 0.559 "Hg (using a Clausius-Clapeyron approximation--ask Caryn), and humidity ratio wo = 0.62198/(29.921/Po-1) = 0.00185 pounds of water per pound of dry air (1 ft^3 of 70 F air weighs 0.075 pounds), 4.565 = 60x415x0.075(wi-wo) makes wi = 0.014295 and Pi = 0.6877 "Hg with a 57.6% RH indoors, which would be a lot more comfy:

T (C) RH% Clo PMV PPD%

28.88889 57.6 .5 .8197596 19.1735

Only 19.1735% of the people would be dissatisfied.

If you could evaporate 6 vs 4.565 pounds of water per hour, you could lower the outdoor air temp to 80.5 F with wi = 0.01506 and a 66.3% RH, which would be even more comfy:

T (C) RH% Clo PMV PPD%

26.94445 66.3 .5 6.351899E02 5.083534

The ASHRAE comfort zone is defined by -0.5 < PMV < 0.5. They also limit the humidity ratio to 0.0120 max, so wi = 0.014295 is outside the zone, even though the calc below suggests it would be close to perfectly comfortable, with 5.083534 Per cent of People Dissatisfied. (You can't please everyone with one condition.)

You may be cooling more outdoor air than you need.

You might enjoy moving the cooler into the room and only running it when the room temp rises to 80.5 F with a thermostat, and only running the fan when the room RH rises to 66.3%, with a humidistat, eg this one:

If you are only cooling the room and C cfm of outdoor air with P pounds of water per hour, and the room thermal conductance is (say) 50 Btu/h-F,

1000P = (95-80.5)(50+C) and P = 60C0.075(wi-wo) make P = 1.73 lb/h and C = 120 cfm, so the 3.25 gallon reservoir would last 3.25x8.33/1.73 = 15.6 hours. 50 CLO =.5'clothing insulation (clo) 60 MET=1.1'metabolic rate (met) 70 WME=0'external work (met) 80 TA=(80.5-32)/1.8'air temp (C) 90 TR=TA'mean radiant temp (C) 100 VEL=.5'air velocity 120 RH=66.3'relative humidity (%) 130 PA=0'water vapor pressure 140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa 150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa 160 ICL=.155*CLO'clothing resistance (m^2K/W) 170 M=MET*58.15'metabolic rate (W/m^2) 180 W=WME*58.15'external work in (W/m^2) 190 MW=M-W'internal heat production 200 IF ICL

[Vic Dura]

On 15 Aug 2007 05:51:58 -0400, [e-mail] wrote Re Re: My swamp cooler / box fan . . . review:

Seems like a 5000 BTU window a/c would work better and be cheaper.

[me]

my thoughts as well

I&#39;ve seen that size as cheap as $100

[Tockk]

Wow . . . now that&#39;s what I call a post . . . Thanks,

--Tock

[Abby Normal]

Am I reading you correct that you are finally using outside air?

[Abby Normal]

Nick has been learning evaporative cooling for a couple years online now, he may understand it one day yet :-)

[Abby Normal]

Nope was the original poster using the outside air. Nick still cannot grasp the inherent flaw with using evaporative cooling on return air.