wrote in message
...
DeserTBoB wrote:

Ragnarkar wrote:

I've just moved to the central valley of California and will be here
for at most 2-3 more years... I'm wondering if it's worthwhile to
invest in a portable swamp cooler...

Sure. Turn it on with a thermostat when the room temp reaches 80, and
turn on a window exhaust fan with a humidistat when the RH reaches
65%...

Too muggy, and too complex.

Well, the ASHRAE 55-2004 comfort standard says 80 F with w = 0.012 is
comfortable, and 80 F at 100% RH makes Pw = 1.033 "Hg, and w = 0.012
makes Pa = 0.566 "Hg, and Pa/Pw = 0.55, so I shoulda said 55%. IMO,
a thermostat and a humidistat and a small exhaust fan are not "too
complex." For "less complex," with no portable swampie, we might
evaporate P = 0.1A(Pw-Pa) lb/h of water from an A ft^2 floorslab
automatically dampened with a solenoid valve scrounged from an old
washing machine and a thermostat to make 1000P Btu/h of cooling.

This is more efficiently done at night, storing coolth in the slab, with
a 58.1 F average daily min and a 93.2 F average daily max in Sacramento
in July, then stirring cool air up into the room with a ceiling fan
to keep the room air 80 F when it is occupied during the day, with no
external ventilation. We can store 100K Btu of coolth in a 10K Btu/F
4" x 1200 ft^2 slab with a 10 F temp swing.

It's essential for effective adiabatic cooling to maintain positive
static pressure...

I disagree.

maintain a good inside air velocity

V = 0.5 vs 0.1 m/s can raise the comfort zone to 82.9 F with w = 0.0121.

and assure quick air exchange.

Removing the water vapor takes C cfm of exhaust air, where
P = 60C0.075(Wc-Wa) = 4.5C(0.012-0.0087) = 0.01485C, ie C = 67.3P
on an average 75.7 F July day in Sacramento.

With a 66.9 F average night temp, moving 100 cfm of outdoor air through
a 70 F house would provide about 100(70-66.9) = 310 Btu/h of cooling.

Evaporating 0.01485x100 = 1.485 lb/h of water would provide another
1485 Btu/h, for a total of 1795 Btu/h, with A = 10x1.485/(1.033-0.0566)
= 32 ft^2 of floorslab, approximately. A 90 watt $55 Lasko 2155A 16"
2470 cfm window box fan could provide 44.3K Btu/h (3.7 tons) of cooling
with 36.7 pounds of water per hour evaporating from a 700 ft^2 slab.

Nick

IMO
Coolers work fine until the dew point reaches 45 degrees. The weather man
says 40 but that is way to clammy for me.

Down sides are
Need to exchange the air constantly. Older homes in Phoenix always had a
window or door open. Now that is a burgerlers dream. Then came up ducts.

Since they are using outside air all of the dirt and crap in the air is
flushed in to the pan. Cooler homes are dustier.

As for the portable models. As long as you are exchanging the air they work.
Put one in a garage in the back corner and turn it on. It will start re
cycling the humid air and then it gets uncomfortable in a hurry,,,, for me
at least.