Evaporative cooler modelling

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Dear All,

I am modelling Indirect-Direct Evaporating cooling system with *constant
volume *and *continuous *setting. The minimum and maximum supply flow ratio
is *1. *The OA fraction is also 1.

The pump & secondary kW value is *0.00015 kW / cfm. *This parameter is used
for space cooling.

With the above settings, energy consumption for *ventilation fan* is
constant. However, the *space cooling energy consumption *is *different *for
each month. The screenshot is as follows:

[image: Inline image 1]

Why the space cooling energy consumption is *not same for all months *even
when constant value of 0.00015 kW / cfm is given as input?

Kindly guide about this.

Thank you

Regards,

Prasad S Wani

via Equest-users's picture
Joined: 2016-07-15
Reputation: 400

Hi Prasad,

More or less energy must be spent to handle the calls for cooling in your model, as occurring. The varying weather conditions & internal loads result in that otherwise constant volume system needing to cycle its cooling-associated energies (i.e. the water pump/sprayer) more/less often.

Note also that for evaporative cooling, even if you had zero fluctuations in heating loads to reject from the building, another factor is the varying exterior relative humidity, which will increase/decrease the effective heat rejection rate.

I anticipate through custom hourly reports you might be able to visualize/plot ventilation fan vs. evaporator cooling energies and find where one is constant/regular the other does correlate with the relative heating loads for the spaces conditioned.

Does that make sense?

~Nick

[cid:image001.png at 01D2E8E1.756366E0]
Nick Caton, P.E., BEMP
Senior Energy Engineer
Regional Energy Engineering Manager
Energy and Sustainability Services
Schneider Electric

D 913.564.6361
M 785.410.3317
F 913.564.6380
E nicholas.caton at schneider-electric.com

15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States

[cid:image002.png at 01D2E8E1.756366E0]

via Equest-users's picture
Joined: 2016-07-15
Reputation: 400

Hi Wani,

I believe that the HVAC system has to meet the cooling load as per the
weather condition mainly.

Supposedly the weather conditions are hot in the month of April to July,
henceforth more energy consumption in cooling to meet the demand as per the
requirements.

The fan is constant volume hence constant energy consumption for all the
months.

The cooling consumption mainly depends on the following factors:

1. Type of HVAC system.

2. Fan conditions

3. Weather conditions.

4. Building envelope u values and SHGC.

5. Various Air-side HVAC Cooling inputs.

Thanks,

Sharad.Kumar.

India.

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Prasad Wani via Equest-users

*Sent:* Thursday, June 15, 2017 8:15 AM
*To:* equest-users at lists.onebuilding.org
*Subject:* [Equest-users] Evaporative cooler modelling

Dear All,

I am modelling Indirect-Direct Evaporating cooling system with *constant
volume *and *continuous *setting. The minimum and maximum supply flow ratio
is *1. *The OA fraction is also 1.

The pump & secondary kW value is *0.00015 kW / cfm. *This parameter is used
for space cooling.

With the above settings, energy consumption for *ventilation fan* is
constant. However, the *space cooling energy consumption *is *different *for
each month. The screenshot is as follows:

[image: Inline image 1]

Why the space cooling energy consumption is *not same for all months *even
when constant value of 0.00015 kW / cfm is given as input?

Kindly guide about this.

Thank you

Regards,

Prasad S Wani

______________________________________________________________________
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via Equest-users's picture
Joined: 2016-07-15
Reputation: 400