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simplest HVAC system

asked 2015-03-08 13:25:22 -0500

vibra gravatar image

updated 2015-03-08 16:22:55 -0500

I want to build a simplest hvac system in energy plus with constant air temperature and constant air flow rate. Is it possible? Can I use ZoneHVAC:IdealLoadsAirSystem to build it?

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ZoneHVAC:IdealLoadsAirSystem is the simplest HVAC system in EnergyPlus. The next simplest might be the ZoneHVAC:PackagedTerminalAirConditioner. Are you looking for a central air system that serves several zones? If the system supplies constant air volume and constant temperature, how are the temperatures of the zone controlled to a set-point? Do you need reheat coils as well?

Neal Kruis gravatar image Neal Kruis  ( 2015-03-08 16:32:58 -0500 )edit

Thank you for your reply, Neal. This is my idea: when temperature is greater than 24C, Cooling start with constant T (15C) and constant flow rate. When temperature is lower than 20C, Heating start with constant T (27C) and constant flow rate.
I'm using energy+ for parameter optimization. So I hope the HVAC model could be as simple as possible.

vibra gravatar image vibra  ( 2015-03-09 11:32:39 -0500 )edit

So you want a system that cycles on and off to meet the zone setpoint? Why is it important that the airflow rate and temperature are constant?

Neal Kruis gravatar image Neal Kruis  ( 2015-03-09 12:37:16 -0500 )edit

Yes.I'm trying to identify the building as a black box. The HVAC system could be considered as input to the system. I need to know what exactly the value of the input is.

vibra gravatar image vibra  ( 2015-03-09 15:10:40 -0500 )edit

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answered 2015-03-09 15:29:20 -0500

Your best bet would probably be ZoneHVAC:PackagedTerminalAirConditioner with a Fan:OnOff. You can use this system to provide a set flow rate and temperature for cooling and heating operation, and it will cycle on and off to meet the load in the zone.

This is more complex than ZoneHVAC:IdealLoadsAirSystem because it requires fan, heating coil, cooling coil, and outdoor air mixing objects. I suggest looking at an example file to see how this object is used if you aren't familiar yet with how it works with the other objects.

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Thanks. I'm looking into the example file. I also have another question. I want to change the initial condition of the simulation. (like the indoor temperature at the very beginning) But I found this from the documentation:

EnergyPlus “runs” the first day of the environment (starting with a set of hard-coded initial conditions) until the loads/temperature convergence tolerance values are satisfied or until it reaches “maximum number of warmup days.

Does it mean there is no chance I can modify the initial condition?

vibra gravatar image vibra  ( 2015-03-10 01:32:19 -0500 )edit

@vibra this is an excellent question! You should post it as a new question so that other people with the same question can find it too.

Neal Kruis gravatar image Neal Kruis  ( 2015-03-10 10:05:47 -0500 )edit

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Asked: 2015-03-08 13:25:22 -0500

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Last updated: Mar 09 '15