I have used the solar water heating module in RETScreen to get the monthly load which I have then fed back into eQUEST in a similar manor.
Brian Fountain
Here's how I do it: (geez it looks long now that I've written it, but it's really not bad and I feel it does a good job)
1. Determine your peak evaporation rate (lb/hr) for the pool(s) within the natatorium
a. Should be available from the pool designers or if not, see the Natatorium section in ASHRAE Handbook - HVAC Applications section 5 (Places of Assembly).
b. Values will depend largely on water temperature and peak "Activity Factor" expected, but ballpark values are
i. Lap pool: 0.05 lb/hr per ft? of water surface area
ii. Leisure pool: 0.2 lb/hr per ft? of water surface area (warmer than lap and higher activity factor (more splashing = more evaporation))
iii. Swirl or Hot Tub: 0.4 lb/hr per ft? of water surface area (hot, with jets)
2. Create a schedule to represent the pool evaporation rate during different usage scenarios (different activity factors, different evaporation rates).
a. I use three modes of operation:
i. Unoccupied and uncovered: approx. 0.3
ii. Occupied and low use: approx. 0.7
iii. Occupied and high use: 1.0
3. Create an Internal Energy Source within your natatorium space with the magnitude equal to the peak evaporation rate, but in Btu/hr (1000 Btu/lb of water evaporating), and make the load 100% latent, 0% sensible like so:
[cid:image001.png at 01CF4B57.31AE05C0]
4. Now create a process heating load on your heating water loop and apply the same schedule. The magnitude of the load is calculated as:
a. Pool water heat loss to evaporation (equal to evaporation "Internal Energy Source"), PLUS
b. Heating energy required to heat the makeup water from DCW inlet up to pool water temperature. This is accounting for heating the fresh water that is replacing the water lost due to evaporation (in the range of 140 Btu/hr per lb/hr of water depending on your makeup water and pool water temps)
c. Note that this assumes that 100% of the heat required for evaporation at the pool's surface is provided by the pool water's heat, where in reality it is expected that some component comes from the air, though I expect it is a small component.
5. Set min and max RH in your AHU and you're done.
And if you felt there was significant heat loss through the pool wall to the ground, you could add that in as well, though I think that it probably isn't when compared to the energy involved in evaporation.
We modeled the pools at the Rec Center at the University of Colorado in 1985 using DOE-2 using information from a booklet that Frances DeWinter developed at Atlas Corporation. In it was an equation for calculating the evaporation off the surface of the pool, and thus the latent load. I could scan the report and send it to you if you're interested. Also, the old version of the FCHART manual used to have equations for calculating the loses from exposed pools, which was also helpful.
Well, it's not EQuest, but it's on topic:
http://energyexperts.org/CalculatorsTools/PoolEnergyUseCalculator.aspx
Robert Wichert P.Eng. LEED AP BD&C
And once you have monthly numbers, yoiu can force feed it into eQuest as a gas Load.
I have used the solar water heating module in RETScreen to get the monthly load which I have then fed back into eQUEST in a similar manor.
Brian Fountain
Tom,
Here's how I do it: (geez it looks long now that I've written it, but it's really not bad and I feel it does a good job)
1. Determine your peak evaporation rate (lb/hr) for the pool(s) within the natatorium
a. Should be available from the pool designers or if not, see the Natatorium section in ASHRAE Handbook - HVAC Applications section 5 (Places of Assembly).
b. Values will depend largely on water temperature and peak "Activity Factor" expected, but ballpark values are
i. Lap pool: 0.05 lb/hr per ft? of water surface area
ii. Leisure pool: 0.2 lb/hr per ft? of water surface area (warmer than lap and higher activity factor (more splashing = more evaporation))
iii. Swirl or Hot Tub: 0.4 lb/hr per ft? of water surface area (hot, with jets)
2. Create a schedule to represent the pool evaporation rate during different usage scenarios (different activity factors, different evaporation rates).
a. I use three modes of operation:
i. Unoccupied and uncovered: approx. 0.3
ii. Occupied and low use: approx. 0.7
iii. Occupied and high use: 1.0
3. Create an Internal Energy Source within your natatorium space with the magnitude equal to the peak evaporation rate, but in Btu/hr (1000 Btu/lb of water evaporating), and make the load 100% latent, 0% sensible like so:
[cid:image001.png at 01CF4B57.31AE05C0]
4. Now create a process heating load on your heating water loop and apply the same schedule. The magnitude of the load is calculated as:
a. Pool water heat loss to evaporation (equal to evaporation "Internal Energy Source"), PLUS
b. Heating energy required to heat the makeup water from DCW inlet up to pool water temperature. This is accounting for heating the fresh water that is replacing the water lost due to evaporation (in the range of 140 Btu/hr per lb/hr of water depending on your makeup water and pool water temps)
c. Note that this assumes that 100% of the heat required for evaporation at the pool's surface is provided by the pool water's heat, where in reality it is expected that some component comes from the air, though I expect it is a small component.
5. Set min and max RH in your AHU and you're done.
And if you felt there was significant heat loss through the pool wall to the ground, you could add that in as well, though I think that it probably isn't when compared to the energy involved in evaporation.
Riley Beise, P.Eng., BEMP
Hello John,
We modeled the pools at the Rec Center at the University of Colorado in 1985 using DOE-2 using information from a booklet that Frances DeWinter developed at Atlas Corporation. In it was an equation for calculating the evaporation off the surface of the pool, and thus the latent load. I could scan the report and send it to you if you're interested. Also, the old version of the FCHART manual used to have equations for calculating the loses from exposed pools, which was also helpful.
Jeff S. Haberl, Ph.D.,P.E.,FASHRAE
One more thing...
If the pool is uncovered, the night sky radiation losses are not
insignificant. I believe that the "energyexperts" data takes this into
account.
Robert Wichert P.Eng. LEED AP BD&C