RE: [EnergyPlus_Support] Re: Maximum Flow Rate Error

It is also could be the issue of the fluid speed limitation in coils. This links with the oil return process.

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Tuesday, May 26, 2015 10:47 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Re: Maximum Flow Rate Error

Very clear. Thank you again Jim!

On 26 May 2015 at 17:29, Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Santiago,
1. Too little flow or too much capacity will cause freezing unless the design is very specialized.
2. Very high flow will result in very little dehumidification or excessive pressure drop. Neither of these are big problems and may be exactly as intended by the design engineer. They're not "normal", however. Thus the warning.

On Tue, May 26, 2015 at 3:19 PM, Santiago Velez santiagogvelez@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Thanks Jim, spot on, like always.
I was wondering about actual physical limitations of Coil design, Why is this a 'normal' range?

1.¿what happens when there is very little flow and high rated capacity?
- Coil too big?
- Risk of freezing?
- bad Efficiency related to coil geometry.
2.¿What happens when flow is very high compared to rated what?
- Coil too small?
- bad Efficiency related to coil geometry.

I guess I can find answer to this questions in ASHRAE Handbooks.

Thanks!

On 26 May 2015 at 13:46, Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Santiago,

EnergyPlus "knows" that a DX coil operating outside of a certain airflow / watt of cooling range is not normal, so it gives a warning.
In recent versions of E+, an allowance can be made for DX coils serving DOAS systems. (Note the field that is 2nd to last in the image below)

It has been a while since I reviewed the definitions, so I cannot tell you at the moment more than the two middle values in the table below are the most frequent cause of warnings (4.027..., 6.041...)

I think that is is describe in detail within the Engineering Reference...

On Tue, May 26, 2015 at 12:14 PM, Santiago Velez santiagogvelez@xxxxxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Hi there, I see this warning very often. Is this 'flow rate per wat (m³/s.W)' range a technological limitation for coils?
Could not find anything about this in either I/O or Eng. Reference. Can anybody help me out of my ignorance in this area?

Regards,
Santiago.

2013-05-20 11:16 GMT-03:00 FrancescoP <direzionecontraria@xxxxxxxx>:

Hello, does that warning refer to a Coil:Cooling:DX:SingleSpeed ?
The warning massage concerns the ratio between the fields "Rated Air Flow Rate" and "Rated Total Cooling Capacity". If you are using the autosizing mode, you could see what "Rated Total Cooling Capacity" is calculated (e.g. in the .eio file) and then you could try imposing a value of the "Rated Air Flow Rate" in order to get a ratio between "Rated Air Flow Rate" and "Rated Total Cooling Capacity" that is in the acceptable range (the range should be indicated in the following part of the warning massage). Then you simulate again.
Best Regards
Francesco Passerini

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Ivan Mezzacapa <ivan_slip@...> wrote:
>
> Hi!
> my simulation gaves me this error.
> "Rated air volume flow rate per watt of rated totalcooling capacity is out of range"
> anyone nows how can i solve this?
> Thanks!
>
> Técg. Ivan Mezzacapa
> Projetista de Ar Condicionado / Consultor de Eficiência Energética em Ar Condicionado
> LinkedIN: http://www.linkedin.com/in/ivanmezzacapaFacebook: http://www.facebook.com/ivan.mezzacapaCelular: (11)9963-9326
>

--
James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l LinkedIn
The truth is still the truth, even if nobody believes it. A lie is still a lie, even if everyone believes it.

--
James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx

Website l LinkedIn
The truth is still the truth, even if nobody believes it. A lie is still a lie, even if everyone believes it.

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