If you were Registered and logged in, you could reply and use other advanced thread options
|
Posted by on June 16, 2005, 4:32 pm
>>
>>>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
|
|
Posted by SQLit on June 16, 2005, 5:06 pm
>
> >>
> >>>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.
|
|
Posted by DeserTBoB on June 17, 2005, 1:13 am
>IMO
>Coolers work fine until the dew point reaches 45 degrees. The weather man
>says 40 but that is way to clammy for me. <snip>
You're going the wrong way. Swampies work better the lower the dew
point. Out here, where subfreezing dew points are the norm, they work
better than mechanical refrigeration.
>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. <snip>
Up ducts, more properly barometric exhaust vents, hinder exhausting
air too much and maintain too high a static pressure to provide good
free air flow. The open window works better, and you can regulate
each room's temperature that way. If you live off of Van Buren,
you're screwed anyway; they'll just bust the door down.
>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. <snip>
No longer true. With synthetic pads, things have much improved with
cleanliness. The RotoBelt I mentioned earlier approachs 30% ASHRAE
rated pleated filter media in efficiency. The old dusty, stinky
"swampie house" should be a thing of the past, unless one uses an old,
traditional louvered box cooler.
>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. <snip>
Exactly. You cannot, in practice, use reciruclated air in an
adiabatic cooling system. With very low moisture content, you can get
away with it for awhile, but in most real life situations, it's only
good for a SHORT while. Other downside to that: anything ferrous
rusts...like it's in Georgia.
For reference: at my location, 75° dry bulb with 45-55% RH is the
norm during the hottest parts of the a 95° day with the dew point at
or below 35°. This is with a RotoBelt 4500 CFM model with the fan on
the low speed, approximately 1/6 HP. When the dry bulb rises above
about 95°, then I go to a full 4500 CFM, and it stays around 75° all
the way up to around 105°. After that, inside dry bulb increases
linearly with increase in outside dry bulb, and w begins to rise. I
just tough it out for an hour, and after sunset, it drops rapidly,
house is purged, all is chilly cool again.
I'll never go back to refrigeration in a desert area again. The old
timers had it right all along; abiabatic's the way to go. Side
benefit: I don't have that "desert rat" skin you see on people who
move up from LA and Orange County that only know how to use their AC.
I've seen the RH in such homes as low as 15%, which is almost
dangerous at those low temps.
dB
|
|
Posted by Rod Speed on June 17, 2005, 1:46 am
>>IMO
>> Coolers work fine until the dew point reaches 45 degrees. The
>> weather man says 40 but that is way to clammy for me. <snip>
> You're going the wrong way. Swampies work better the lower the
> dew point. Out here, where subfreezing dew points are the norm,
Yeah, they are here too.
> they work better than mechanical refrigeration.
Dunno about that, but they are certainly much better power consumption wise.
>> 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.
Thats trivially fixable, just put a decent security grill over the open
whatever.
>> Then came up ducts. <snip>
> Up ducts, more properly barometric exhaust vents, hinder exhausting
> air too much and maintain too high a static pressure to provide good
> free air flow. The open window works better, and you can regulate
> each room's temperature that way. If you live off of Van Buren,
> you're screwed anyway; they'll just bust the door down.
Nope, completely trivial to make it so they cant bust it down.
You only have to do that well enough so that its too much
trouble and they loot the neighbour's place instead.
And you can blow them away from behind the grille anyway.
>> 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. <snip>
> No longer true. With synthetic pads, things have much improved
> with cleanliness. The RotoBelt I mentioned earlier approachs 30%
> ASHRAE rated pleated filter media in efficiency. The old dusty,
> stinky "swampie house" should be a thing of the past, unless
> one uses an old, traditional louvered box cooler.
Mine gets dusty because I turn it off and open all
the patio doors up when its cool enough outside.
>> 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. <snip>
> Exactly. You cannot, in practice, use reciruclated air in an
> adiabatic cooling system. With very low moisture content,
> you can get away with it for awhile, but in most real life
> situations, it's only good for a SHORT while. Other
> downside to that: anything ferrous rusts...like it's in Georgia.
> For reference: at my location, 75° dry bulb with 45-55% RH is the
> norm during the hottest parts of the a 95° day with the dew point at
> or below 35°. This is with a RotoBelt 4500 CFM model with the fan
> on the low speed, approximately 1/6 HP. When the dry bulb rises
> above about 95°, then I go to a full 4500 CFM, and it stays around
> 75° all the way up to around 105°. After that, inside dry bulb
> increases linearly with increase in outside dry bulb, and w begins
> to rise. I just tough it out for an hour, and after sunset, it drops
> rapidly, house is purged, all is chilly cool again.
I usually turn it off in the early evening because its too cool for me.
But then I like it warmer than most and dont
turn it on until the inside temp is about 88F
> I'll never go back to refrigeration in a desert area again.
I might add it, but just for winter heating
and the very ocassional high humidity days.
> The old timers had it right all along; abiabatic's the way to go.
> Side benefit: I don't have that "desert rat" skin you see on
> people who move up from LA and Orange County that only
> know how to use their AC. I've seen the RH in such homes as
> low as 15%, which is almost dangerous at those low temps.
No it isnt.
|
|
Posted by DeserTBoB on June 17, 2005, 1:02 am
On 16 Jun 2005 16:32:15 -0400, nicksanspam@ece.villanova.edu wrote:
>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. <snip>
Nice theorhetical, but putting into practice in a wood frame
apartment's a little difficult.
>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. <snip>
Again, the numbers work on that, but adapting it to exising
households?
>
>>It's essential for effective adiabatic cooling to maintain positive
>>static pressure...
>
>I disagree. <snip>
Ah, here's were experience takes precidence. If you use the
already-named Essick RotoBelt with a polyplastic endless belt of
filter media, the filtration efficiency (assuming both pad gearmotors
are operating, e.g., max cooling mode) exceeds ASHRAE 30% filter
specifications. Old-time Excelsior pads provided filtration from low
flying birds and scant little else, and added the enjoyment of mold
and mildow, something a belt type media has no problem with. Added
benefit is that the pads are continuously cleaned each trip through
the sump...but I digress.
If you want ASHRAE 30% filtration and want maximum air flow, you must
have some positive static pressure in the conditioned space.
>
>>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. <snip>
Trust me, having worked in Sacramento more than a few times...swampies
do NOT work effectively there on a typical delta summer's day! You
cite the average, but the peak is what is of concern. Also, the
average moisture statistics for that area are misleading; relative
humidity in that area makes wide swings during the day.
>
>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. <snip>
Nice theorheticals, but it won't work in practice. Neither will a
portable swampie. If she's up toward Auburn, or up further north,
say, Tehama or Williams, she's got a chance with adiabatic. If she's
in downtown Sac, or going west toward Davis the Carquinez Straits,
it's refrigeration all the way, most of the time, until you get as far
west as, say, Martinez.
Theorhetical numbers are cute. Experience and metrics are better.
dB
|
Page 1 of 4 1 2 3 > last >>
| Similar Threads | Posted | | swamp cooler leaking hot air | January 9, 2006, 7:16 pm |
| Swamp cooler questions | March 10, 2006, 5:05 pm |
| Swamp Cooler to Refrigeration A/C | March 10, 2006, 10:54 pm |
| Swamp cooler question | April 1, 2006, 11:34 am |
| Pseudo Swamp Cooler | May 8, 2006, 1:14 pm |
| swamp cooler pan is leaking | May 16, 2006, 1:26 am |
| algea in swamp cooler | May 22, 2006, 8:35 pm |
| Re: Swamp Cooler Algae | August 30, 2006, 8:56 pm |
| Re: My swamp cooler / box fan . . . review | August 15, 2007, 5:51 am |
| Swamp cooler question | June 2, 2008, 2:26 pm |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap