Modeling simple fans and fan-heaters in Openstudio

Hi, I have modelled a unit apartment with 190 units in Openstudio which don't have any central HVAC systems. I need to model simple fan (20-60w usual electric desk fan) for summer as well as fan-heater (1500-2400w usual electric fan-heaters) for winters for each unit. I have used "CV unit heater elec" as the heater but as you know it's a fan coil and I am not sure if it can properly simulate fan heaters.

Comments

@Graphus what simulation tool are you using? Please mention it in the title or body of your post, as well as add a tag so that others can provide better help.

Also, what makes a fan-heater different from a unit heater?

Aaron Boranian (2024-07-02 08:41:34 -0500) edit

@Boranian Thanks for the reply. Well, I thought CV unit heaters are water-based fan coils and the efficiency and energy consumption might be different to a simple fan heater? But I would proceed if they are the same, only I couldn't find a reference for the air flow rate and air pressure of a simple fan heater. Any help? Also, can you please let me know if summer fan can also be modelled in OS and if you can address Airflow and Airpressure for them as well? I need to check Fan impact on thermal comfort.

Graphus (2024-07-15 22:03:12 -0500) edit

add a comment see more comments

Hi Graphus,

To your first question, are you just trying to capture the energy from running the fan? If so, I'd recommend adding it as an electric load, and giving it a schedule that has it turning on and off at the times you're expecting throughout the year. Since desk fans are usually driven by occupant behavior, you could look at using a schedule that follows occupancy loads or just use something as simple as the fans running all day and turning off at night. If you're just trying to capture energy, then using the power draw from the outlet will capture everything.

As for the space heater, the CV unit heater elec is what you want. Notice that after adding the heater to the zone and clicking it to edit it, even though the OS:ZoneHVAC:UnitHeater section mentions water coil info, if you scroll down there isn't a water coil object associated with the unit heater. You could hard size the Maximum Hot Water Flow Rate input to zero if that would make you feel better, but there isn't a water coil that can actually supply heat. The unit heater only has OS:Fan:ConstantVolume and OS:Coil:Heating:Electric objects that you can configure for it. TheUnitHeater objects in EnergyPlus and OpenStudio can take a few different forms, which is why you get some input overlap. I would recommend hard sizing the Nominal Capacity for the electric heater rather than relying on autosize for your use case. It sounds like these are imitating heaters that plug into walls, so choosing a fixed value for the unit heater makes the most sense.

Hope that helps a bit!