Dear Mário,
Keep
in mind that you can define the boiler and chiller curves to be anything you
desire.
When
I said earlier that I would define the Boiler efficiency and Chiller COP =
1.0, I forgot to say that I would also define the curves so that the part load
efficiency was always a constant value which equals the peak efficiency.
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: EnergyPlus_Support@xxxxxxxxxxxxxxx
[mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Mário
Sent: Monday, May 17, 2010 5:43 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Re: Variable Volume Refrigerant System
Hello James
Thank you for your Input.
Based on tour idea, I think that the curve operation for the equipment is a
good idea, but what if the chiller and heat pump has similar operation curves
to those of the production equipment of the VRV…
I don´t know how the energy building certification work´s in your country but
in Portugal we use an asset rating in order to classify the building. For
example in the case of a office building the occupant loads are much smaller
then from the actual operation load (outside air include). This means that if
the HVAC in the builing is a VRF system you constantly will be be working with
the machines at very low load which means that the VRF is not beaming used at
it´s optimal working point.All this text has the conclusion that a water system
has the flexibility for load adaptation, which compared to the 14% minimum load
operation of the VRF system is good. (Just a though)
I´am going to think about your idea.
Thank you once again.
Mário Neves
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx,
"James V Dirkes II, PE" <jvd2pe@...> wrote:
>
> Dear Mário,
>
>
>
> I'm currently working on a VRF system and am modeling it this way:
>
>
>
> · The actual system uses Mitsubishi City Multi VRF units with heat
> recovery capability. I am not sure if this approach will work for other
> manufacturers of VRF systems.
>
> · My model uses water source heat pumps (WSHP) for each zone. These
> should capture the ability of the VRF system to "shift" energy
around when
> some zones are heating while others are cooling. The model is running
> without error, but I have not addressed the details of the energy portion
> yet. That part will go similar to the following…
>
> o The WSHP fans will be assigned power (efficiency and pressure rise) to
> match the VRF fans.
>
> o The WSHP heating and cooling coils will have a "simple" power
> consumption coefficient. If I can use 0 power, that will be best, since
the
> VRFs don't use power at each zone except for the fans. If I can't use 0
due
> to some E+ restriction, I'll probably make it equivalent to a COP as high
as
> possible and then report that energy in a Custom Meter and use a Custom
> Decrement Meter so it can be removed from the total electricity use.
>
> o The WSHPs have a gas boiler with efficiency of 1.0 for supplemental heat
> and an electric chiller with COP of 1.0 for supplemental cooling. The 1.0
> efficiency / COP values are used for simplicity so that energy used by the
> boiler and chiller is essentially the same as the load.
>
> o I will report the boiler and chiller energy and "post-process"
their
> energy using the manufacturer's part load efficiency equation. It occurs
to
> me just now that I may be able to apply curve values which mimic the
> manufacture part load performance and avoid the post processing….
>
>
>
> The Building Performance Team
> James V. Dirkes II, P.E., LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
>
>
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of Mário
> Sent: Sunday, May 16, 2010 4:12 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Variable Volume Refrigerant System
>
>
>
>
>
> Hello
> Does anyone have any ideas on how to model a variable volume refrigerant
> system, like a VRV or VRF system in which you have one exterior machine
> linked to vários interior terminal machines?
> Thank´s
> MN
>
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