Evaporative cooler question

If the house is airtight, once you reach 60% RH you won't be able to evap any more water (if you want to mainintain 60%) , so how will you cool it.

Evap cooling and airtight are not compatible.

Even though it is an open system, evap is mych more energy efficient compared to AC.

Mark

Reply to
Mark
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Please note the exhaust fan in series with the 54% humidistat.

Nick

Reply to
nicksanspam

You are just not getting it. The air out of a roof mount is often already near the 54% level. Wasting more electric trying to squeeze a little more cooling out of a given volume of air is not cost effective.

Then there is a question of what type of pads are you suggesting. The traditional Aspen shaving or other synthetic pads that are one or two inches thick? Or the more efficient (and expensive types) that are 4 to 8 inches thick?

The beauty of an evaporative cooler is being able to live differently than living with refrigeration You can leave your windows open and operative devices such as ovens as much as you like. Regardless the humidity level is often regarded as too high.

Anyway, any savings in minimal. Are you suggesting changing life style to save two or three gallons of water a day so we can keep our pool full and pour a couple thousand gallons a day on the lawn to keep it looking nice?

Refrigeration is still the preferred method of cooling.

How to improve refrigeration efficiency is where your efforts should be applied. One way is to use an evaporative cooled air to cool the condenser coils. One that has been around for a long time used copper condenser coils and sprayed water directly on the coils. Commercial users often use pools with cooling towers for cooling their freon.

And the building industry is looking hard at ways to make homes energy efficient in the SW:

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Reply to
Rich

I'd say the same.

Indoor evaporation is equivalent, with improvements.

None whatsoever.

Nonono. That is ugly.

Would you have any evidence for this article of faith?

Nick

Reply to
nicksanspam

No. Cooling only at night cuts water use by about half,

4.3 vs 8.0 gallons for this small well-insulated house. 20 GH=98'house conductance (Btu/h-F) 30 TAM=106'max air temp (F) 40 TAA=91.1'average air temp (F) 50 WA=.00384'average humidity ratio 60 TC=80'comfort temp (F) 70 WC=.012'comfort humidity ratio 80 PC=60*.075*(WC-WA) 90 FOR H=0 TO 23 STEP 2 100 TA=TAA+(TAM-TAA)*SIN(2*PI*H/24)'outdoor temp (F) 110 CFM=GH*(TA-80)/(1000*PC-(TA-80))'exhaust airflow (cfm) 120 IF CFM
Reply to
nicksanspam

So what? That is a piddling savings. Families use much more than that just flushing the toilets not to talk about watering the lawns and keeping swimming pools, golf courses, football fields etc. etc. You are going to be running the inside cooler more and use more electric. Running a fan all night is more wastefull than using 4 gallons of water.

Now if you want to really save you should set your home thermostat at 62 for the winter.

And again the main reason we even use evaporative cooling is because we can keep the windows open. Refrigeration is so much more comfortable. The people of Phoenix have both. They use the swamp cooler until the humidity gets too high. Faith has nothing to do with it. It is living in comfort. Anytime the humidity gets more than 30% we get uncomfortable as we are not used to it. Since it is so hot outside we get used to heat and tend to set our thermostats higher than people from the east find comfortable. The same goes for humidity. We are used to the hot dry outside air and humid is not comfortable.

Reply to
Rich

For this small well-insulated house.

Keep up. In this model, the fan only runs 0.65 hours per night.

I'm typing naked at the keyboard in a 39.5 F room.

Nick

Reply to
nicksanspam

If you have never lived in a house with an evap cooler, then you have no idea what you are talking aobut.

Mark

Reply to
Mark

So? With water at about $2 a thousand you are saving at least 25 cents a month!!

So? In the SW water costs an average of about $2 a thousand. Power costs over 8 cents per KW. Using your numbers, running the fan, you will save about 0.8 cents worth of water per night and the fan must be 100 watts or less just to break even. Water is more plentiful than electric power.

Can you bring it around to using more water and less electric? Preferably with refrigeraton cooling.

Reply to
Rich

That may increase a lot when present interstate agreements expire.

Your arguments might be a lot more persuasive if you were to learn the difference between power and energy.

Keep up. The 90 watt fan would use 32 Wh/night, ie about

8 cents/month for this small well-insulated house.

Nick

Reply to
nicksanspam

That is what I am trying to get through to him. Reminds me of a brilliant engineer we once hired. He could solve the most difficult differential equations. Problem was he could not build anything.

For comfort I myself would prefer refrigeration but for our lifestyle the cooler is preferable. We like to have our windows open and like the air movement. The significantly lower cost is another advantage. The malls and other stores have refrigeration but I note that the big box stores like Lowes, Home Depot, SAMS, and COSTCO all use evaporative coolers. Can you imagine the complaints they would get from their customers if they let the humidity get up to the 54% level?

Reply to
Rich

Rich wrote: ...

That's a false economy...water is less plentiful in actual terms, in the West.

Reply to
Duane Bozarth

Should have said cheaper. Point is that the little used by coolers is insignificant compared by that used for irrigation. The fountains of Las Vegas do not present a conservation theme either. I have not checked lately but for quite some time the government was paying farmers and supplying water to irrigate land and raise cotton in AZ and paying farmers in the east not to raise it.

Reply to
Rich

My point is that under present policies, water costs are artificially low in much of the West, which you have just reinforced... :)

And, it's absolutely impossible to justify all of US ag policy, just as it is any other area of US policy owing (in large part) to the conflicting interests that compete to build it...so it's futile to even start discussion.

I wasn't arguing, just pointing out a situation as one who lives where long-term water is a major issue...

Reply to
Duane Bozarth

terms,

Me too (for the past 45 years watching the population grow and grow), presently on the upper end of the Colorado river. The CO reservoirs might even get full this year. But Mead and Powell is something else.

Reply to
Rich

becuase

electricity...

Like I said before, if you got a rock bin or storing ice we have some valid thermal capacitance. Typical house, no.

How many hours at 77,78, and 79 :)

60C0.075(0.012-0.00384)

Okay it's a column of mercury. Usually with heat transfer equations when you use differentials it is fine to use F or C, but when you are multiplying and dividing you usually require absolutes as in the empirical exponential one in program line 50. It looked like you were multiplying by degrees F with the .566

I lost my entire library recently to a flood and I cannot check all the formulae you are quoting,

You are assuming 0.012. You are not proving. I think in arid regions with evap cooling indoor RH will be lower. The indoor condition will have to be very close to the same wet bulb as the ambient.

complete

You will find that the room temp will rise above 80.

Adding sensible and latent heat to air, is sort of like horizontal and vertical vector components on a right angled triangle. The problem is the angle of the resultant is fixed with evaporative cooling.

I think you will have problems coming up with 0.0012 unless it is for internal latent gains such as from occupants, or the fact that your design emulates a sauna. Don't forget sensible gains from occupants as well.

You use round numbers here, but get very particular elsewhere, especially in the empirical formulae. Why alter physical properties such as the specific heat of air or the heat of evaporation of water?

You keep talking about super insulated homes, massive thermal storage. My argument is evaporative cooling is high airflow per unit cooling. You fictitious numbers do not change this. You are merely shaving the load.

Most of the heat comes from the fluid inside the bottle. The evaporating water draws heat from the remaining liquid water which cools off and draws most of its heat from the bottle.

Now of course the slab is insulated. I have seen a lot of insulated slabs in northern homes with radiant floor heat. You keep changing the house parameters, but evaporative cooling is still high airflow per unit cooling.

I guess its going to be the wetted ceiling slab next. You can model the maximum size water droplets that surface tension will allow on the underside of the ceiling without it raining indoors. Then you can eliminate the ceiling fans and take advantage of the heat stratification. It would the 8th wonder of the world, one up on the Hanging Gardens of Babylon. You can name it the Inverted Pool of Pine :)

stratify

Let's see, 106 degree outdoor air is going to enter a room. Is it better not to control and remove the sensible heat from this room air first before it creates discomfort or to walk around on a wet floor?

Treating the air first before it can add its heat to the space is like getting a vaccine to prevent a disease. Trying to deal with it later, is like going to the hospital to be healed.

Again, people don't live in averages and not every home has both parents working and the kids in daycare. People are at home on weekends. I would still like to see you show how your 'comfort' conditions will exist following psychrometric rules. It all revolves around wet bulb temperatures.

Reply to
Abby Normal

...

We (as in KS) has been fight w/ CO (and, to a lesser degree, NE) over the Arkansas, N Platte, and Republican Rivers for about that long....KS won a Supreme Court decision about two or three years ago regarding how much upstream states could (legally) siphon off prior to the crossing of state lines...CO has yet to even come close to meeting the mandates so that the Arkansas (closest river of any size to us) is now (and has been for ~20 years or so) dry most of the time at the CO/KS border and the Cimarron hasn't flowed out of NM for about twice that. Although it was always a case where there may not have been surface water all the time, until about the mid-60's there was always enough that a simple hand hole scooped in the bed would raise water--now it's bone dry and grown over until about 100 miles east of us...

Reply to
Duane Bozarth

Yeah, I know. However, the Arkansas drainage area has been the deepest drought area of the state and unfortunately being on the eastern slope it is not an area that ever gets a lot of moisture. This year I think they are well above normal so it should start to flow again. And NM is the same. Those streams can not be depended on to continuously supply significant water. Sooner or later farm irrigation is going to have to end or the country is going to have to get rid of a lot of people.

The Aquifers in NE are being pumped dry but the farms continue to drill deeper and deeper.

The Colorado river is something else. That is the area with the heaviest snow but is a major supply for many states but it too can not be considered much more as a source of water for agricultural irrigation.

Reply to
Rich

Concrete stores about 25 Btu/F-ft^3, so a 1200 ft^2 x 4" thick slab has C = 25x1200x4/12 = 10000 Btu/F of valid thermal capacitance, or more, if it's in contact with soil with no insulation beneath.

The house needs 24h(91-80)128 = 34K Btu/day of cooling, no?

The slab can provide that with a 34K/C = 3.4 F temperature swing, plus a smaller amount that comes from the slab airfilm resistance: when it's 106 F outdoors, the house needs (106-80)128 = 3328 Btu/h of cooling. A dry slab with a U1.1 radiation conductance under slow-moving air from a ceiling fan with a U1.5 convection conductance can provide

3328 Btu/h of cooling with a 3328/1200/(U1.1+U1.5) = 1.1 F slab-air temperature difference. To keep the house 80 F all day, the slab has to start the day at 80-1.1-3.4 = 75.5 F.

More. It's a sine wave. With some indoor evaporation at night, the fan can be a lot smaller.

Sorry to hear that. It's mostly just "Ohm's law for heatflow." Line 50 below is an approximation for the ("Hg) vapor pressure of water at temp Ta (F). It's close to the numbers you'd find in table 3 in chapter 6 of your ASHRAE HOF, if you still had one.

50 PS=EXP(17.863-9621/(TA+460))'outdoor vapor pressure at 100% RH

I'm not sure what you are getting at, Abby. We evaporate water inside a house, with an exhaust fan that turns on when the indoor RH reaches

54%. The outdoor air is much drier. What's to prove? Would we need to prove that a house with an AC and an 80 F thermostat setting is 80 F indoors? We might wonder if the AC has sufficient capacity...

Why do you think that? Perhaps you imagine that an indoor wet surface will just stay wet, without evaporating any water. I used a simple ASHRAE swimming pool formula. A ft^2 of wet surface at temp Tw in air with Pa "Hg loses 100A(Pw-Pa) Btu/h by evaporation, where Pw is the saturation vapor pressure at Tw. It's a little surprising that this formula doesn't include the air temp, but it's well-known and often used. An airtight house with an indoor humidity source will eventually have 100% RH indoor air...

Brrr. Why can't it be warmer than 65 F? Especially if the water only turns on when the room temp reaches 80 F, using a thermostat?

Why would you say that? Conservation of energy (energy in = energy out, over a day) says otherwise.

I don't understand that. Perhaps it has more to do with a box on the roof than this indoor scheme.

Why would you say that, exactly? We can always add more details, but that won't change the performance much, IMO.

That's true, traditionally.

In what ways are they fictitious? OK, it's a tiny house. We could scale it up and add lots of air leaks and remove the insulation and thermal mass :-)

I'd say we are discussing more than that.

Of course. I didn't see that.

Or on dry soil.

Sometimes, as potential improvements arise.

By tradition.

Nonono. Cool floor, warm low-e ceiling.

Not a good idea, IMO.

The floor should never be "wet," and the house should never admit

106 outdoor air. I wonder if Fu-Tung Cheng's fancy concrete floors
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are porous to water or water vapor.

Is indoor evaporation at night like Mother Theresa?

Nick

Reply to
nicksanspam

Evaporative cooling works on a constant wet bulb temperature. You need to research this. Whether it is done realistically by blowing hot dry air through a wetted media or blowing hot dry air, down from the ceiling to a wet floor.

saturation vapor

I even lost my Dectron Manuals in the flood. They taught ASHRAE!

Evaporative cooling works on a constant wet bulb temperature.

Try this, evaporate so much water into the air that the room goes to

71F db/ 65 wb. Then turn off the water and seal off everything. Let sensible heat gain warm air to 80F @ 54%.

Constant wet bulb.

Or let room go to 91.1F db / 65 wb. Then shut off water and let sensible heat warm air to 100F. Turn the water back on until you get

80F @54% RH.

Evaporative cooling works under a constant wet bulb temperature. Check out the slope of a wet bulb line.

storage.

It's true period.

bottle

So you are now cooling an insulated slab. You are trying to reason that evaporating water water all night now cools this slab off so when you blow hot air down with your ceiling fans all day, it cools this air. By the time the occupants who are not home all day get home the air has cooled to 80?

They come home and flood the floors so they have a cool home when they get up for breakfast?

Let's recommend concrete partition walls, concrete cabinets and no baseboard trim. Gives some more thermal capacitance and not a source of food for mold. :)

You are unsuccesfully trying to be non-traditional. Evaporative cooling works, by depressing the dry bulb temperature of flowing air, to be cooler than the desired space temperature you wish to maintain.

You add humidity directly to the air through a wetted media. You depress the air temperatue of the supply to be cool enough below the setpoint temperature to offset the sensible heat coming into the space. It will be a small temperature differential compared to DX cooling and it will have a high airflow per unit cooling.

Wetting a floor slab, can probably give an average dry bulb temperature that falls in the comfort range, but the process to get there will take occupants through discomfort of overly high humidity or dry bulb temperature to get there.

It is also impractical, unhealthy and dangerous to keep wetting a floor slab.

Inverted Pool of Pine needs no fan :)

concrete will be pourous but hopefully the insulation that you are now using under your slab is a vapour barrier. If not maybe the excess water being used would naturally irrigate a ring of lush vegetation around the house to reduce the solar gain you have been neglecting.

later,

Its like praying for it to cool off.

Reply to
Abby Normal

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