[Equest-users] modeling an indoor pool in eQuest

[Brian Fountain]

Good morning Matthew,

There are a few considerations when modelling pools in eQUEST.

Pool water heating -

This piece might be the most straightforward.  The pool water heating requirements will be modelled as a peak flow and schedule as a direct load on either a hot water loop or a DHW Loop where it will be part of the building DHW energy as an end use.  The peak flow and schedule here will be determined as the greater of the pool water evapouration or the make-up water if there is greater make up flow due to water per swimmer requirements.  If the pool water heating is added as a direct load to a hot water loop, it will show in the “equipment” end use.  Generally, where building boilers are used to provide pool heating along with space heating, my practice is to create a secondary pool hot water loop to the main hot water loop as it makes isolating and reviewing the pool heating easier in the PS-D and PS-H reports of the .sim.  A dedicated primary hot water loop for pool is appropriate when the pool heating equipment is dedicated and/or when heat is recovered from the pool air handling equipment.

Conditioning the pool air space -

In order to model the dehumidification of the pool zone, you will need to impose the latent load caused by pool evapouration.  There are a few sources for the calculation of evapouration from pools.  I recommend  "Methods for Calculation of Evaporation from Swimming Pools and Other Water Surfaces," ASHRAE Transactions, vol. 120, part 2, 2014 which is available from the author’s website here: https://mmshah.org/publications.html (item 23).  However you determine the evapouration rate, you will impose it on the space as an “Internal Energy Source” on the “Equipment” Tab of the pool space.  The “Input power” will be the peak evapouration with a sensible HG ratio of 0 and a latent HG ratio of 1.  I have been using the latent heat of evapouration of 1,046 BTU/lbm of water evapourated for an 84°F pool.  Depending on your pool surface area and temperature, activity factor and the natatorium air conditions, I expect your peak evapouration to be in the range of 150,000 to 500,000 BTU/hr.  A schedule is required for the occupied and unoccupied evapouration taking the pool activity factor into consideration.  Given that the energy for heating of the water evapourated is covered in the pool water heating above – I recommend setting the Source Type for the evapouration to Process – that way it is not “double counted” on the utility bill.
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Dehumidification is achieved by setting the maximum humidity keyword in the air handling system serving the pool area.  Note that the space temperature of the pool air volume is often kept higher than the rest of the building and will need to be set appropriately.  The ventilation rates will be set for dehumification requirements.  Heat recovery from the dehumiditication system is common with condenser energy often being used to preheat outdoor air as well as heating the pool water.  Personally, I have not had good success using the DX waste heat keywords to transfer condenser heat to a DHW loop.  My practice has been to use a heat recovery chiller to do the heat recovery to a hot water loop.  Note that the heat recovery chiller keywords are not recovering heat to the hot water loop in DOE-2.3 so I recommend DOE-2.2 for pool modelling (at least if you have heat recovery to the pool water heating).  A heat recovery chiller can recover to either a HW or a DHW loop.  If you use a DHW loop, you will have to reduce the loop delta-T to below 70F or eQUEST will throw an error.

Cheers,

Brian

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Brian Fountain
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From: Equest-users <equest-users-bounces at lists.onebuilding.org> On Behalf Of Matthew Yarmon via Equest-users
Sent: August 20, 2020 10:39 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] modeling an indoor pool in eQuest

CAUTION: EXTERNAL SENDER
Hello,

I am looking for general guidelines on how to model an indoor pool in eQuest, including energy requirements to heat the pool water, and energy requirements to heat/cool/dehumidify the air. If anyone has any resources to point me towards, that would be greatly appreciated. The pool in question is located in northern Alberta, where the temperature dips to as low as -22 °F in winter. The pool has two small windows.  Its roof is part of the building envelope, but its walls are not - the walls are adiabatic.

Thanks,
Matthew
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