Indoor pool HVAC Engineering

[new2hvac]

There seem to be a lot of variables in indoor pool HVAC engineering. I'm trying to get a clear picture of what's involved. So far, I've identified the following and have questions associated with each...

1) Air temperature should be at or slightly higher than water temperature to minimize evaporation rates. I assume this will cause the vapor pressure of the air to be higher than that of the water. Will the evaporation rate continue to decline if the temp delta is even higher? Of course, increasing the air temp will decrease the RH so there must be a sweet spot.

2) Humidity level should be kept around 50%. This pool is in a very dry climate - near Denver. Some people tell me dehumidification will be required via refrigeration coils and others tell me the outside air should be sufficient. I also understand that a humidifier might be required at times. Of course, it depends on what the particular vendor is selling.

3) Between 4 and 6 air changes/hour is recommended by ASHRAE. This pool has some pretty extensive corrosion on the metal surfaces. It begins at around 8' above the water surface and worsens as you get closer to the pool. I've heard that evaporated, chlorinated water turns into hydrochloric acid as it condenses. Is this true? Is there anyway to address it? They are currently running 4.8 air changes/hour.

Thanks in advance!

 

[62hog]

If you are getting condensation on the walls, your RH is too high in the space, or the air is not being mixed properly to be destratified.

Are most of the problems you see occuring in the winter or during the summer?

Is the pool heated? (I would assume that it is, being in Denver.)

The best thing to do is talk with your local rep for a specialty pool space conditioning system, such as PoolPak. They can answer your questions much more efficiently, probably than you might be able to get here. (No offense intended to anyone here, but they are specialists.)

 

[IRstuff]

Your first item seems counter to what I would have thought.

Higher air temperatures support more net moisture in the air and would heat up the surface of the water and increase the evaporation rate.



TTFN

 

[ChasBean1]

New2 - a guy has a pretty good post here on this link:

http://van.hep.uiuc.edu/van/qa/sect...Evaporating_and_Condensing/20020321122324.htm

This is not a slam-dunk problem. It can be very complex and not answerable in a sound byte. As brief as possible response to each numbered issue:

1) See IRstuff's (no relation to HR Puff'n'stuff) post. I agree. Higher air temp = more evaporation for a given moisture content. Saturated (100% RH) air won't take additional water from the pool.

2) I can't say I really agree that RH level should be kept 50%. Definitely don't think you'd ever need a humdifier. The important thing is to keep the general air dewpoint below the surface temperature of surrounding walls & other stuff that's corroding.

3) The chloride ion stays in the water and concentrates during boiling or evaporation. The corrosion phenomenon you mention is probably related to condensation on wall surfaces (worst during cold weather). To help this, I would like to see as much baseboard radiative heat as possible to keep the walls warm at low points (best controlled on an OA temp reset schedule), closest to the pool.

 

[ChasBean1]

After saying that, splashing of the pool water is another story! All bets are off re: chloride corrosion...

 

[lilliput1]

Talk to indoor pool AC manufacturer's local rep (use Google to search the internet). They have design guides that would answere your questions. You can use air cooled pool AC with heat recovery used to preheat pool water prior to heating the pool water with a gas or electric heater. The heat recovered is rejected heat that is part of the condenser heat rejection. You also have to provide reheat, either hot water or electric. Use aluminum ductwork & route ductwork around the pool to blow from the perimeter inwards towards the pool center. Above the middle of the pool locate the exhaust air intake. The quideline will cover exhaust required & room ACPH. I can't recall specifics. It's been a while since I did the design. However it was value engineered out & the pool ended up not being enclosed. It still had water heating with gas but the pool is closed in the winter & the pool heating rarely used.

 

[hyahsa1]

what is our steps to design a sauna.

 

[guying]

Hi,
I have a similar problem. We are actually buildind a sport-centre in the middle of the Sahara desert (Tamanrasset). We did our calc for ventilation according to ASHRAE. The client claim that we have to consider the altitude in our calculation (1460 m) to consider the right rate of evaporation. Everybody we asked told us it would have no significant impact. The conditions are, outside air 40°C summer and 0°C winter. RH less than 15%. Pool 25 m X 12.5 m. Heated ventilation provide outside fresh air and extractors evacuate through the roof.
The altitude is 1460 m.
Can anyone tell me if altitude is a significant variable on the effectiveness of a system

 

[Rodale]

The air temperature should be "about" 2°F above the water temperature. If you live near a lake, as soon as the air temperatre drops below the water temperature you see "steam" rising off the water. The same thing happens in a pool.

Try looking at the

http://www.desert-aire.com/

They have pool dehumidification engineering literature.

Good luck

 

[HVAC68]

Evaporation loads in pools are significant relative to other load elements and may vay widely depending on pool features, the areas of wet deck, water temperature and activity level in the pool.

Please read the relevant details on "Natatoriums" in ASHRAE Applications Handbook - I have 1999 edition - the page reference is 4.6.



HVAC68