[esp-r] Re: Night-time ventilation

[Aizaz Samuel]

A very simple way of setting up an MVHR in a flow network is to make a 
mixing box zone and supply all fresh air from that. Then supposing the 
MVHR is 80% efficient set up the room extracts to extract 80% to the 
mixing box. This ensures 80% of heat is extracted and supplied to the inlet.

Not too clever if you are looking for an exact representation though.

-Aizaz


On 18/06/13 21:44, Matthew Wright wrote:
> Thanks Achim,
>
> 1) I set a door to have a constant input at different constant volume
> flows, and inspected the back pressure, (below 1m./s wind day selected)
> which allows one to measure the q50 for the model. I then had set size
> cracks and adjusted their size to hit the target q50.(!)
>
> 2) MVHR = Mechanical Ventilation Heat Recovery in the British market, as
> far as my experience goes.
>
> Thanks again,
>
> Matt Wright
>
>
> On 18/06/2013 20:29, Achim Geissler wrote:
>> Hi Matt
>>
>> some quick thoughts:
>> 1) that would also be my approach without any detailed knowledge on existing "real leaks". If, for example, the building has a wooden roof and is otherwise mainly made of concrete, I would probably put more leaks in the roof and then think about how the cellar (simple windows?) is connected internally to the rest of the building. Also, leakage paths inside lightweight walls (think of plumbing etc) are often found. The ESP-r model is then a series of cracks and small openings, yes.
>>
>> 2) I am not entirely sure what a "MVHR" is, but the heat recovery you describe would work, yes. You could "tune" it by adapting the heat transfer coefficients of the thin wall. There is a heat recovery flow component, I think (there definitely should be a heat recovery plant component, I am quite sure).
>>
>> Best
>> Achim
>>
>>
>>
>> On Jun 18, 2013, at 6:23 PM, Matthew Wright <matthew.wright at c4ci.eu> wrote:
>>
>>> Hi Achim, Jon (and all),
>>>
>>> I have successfully modelled using air-flow networks, as I am interested in
>>> overheating in residential (and therefore often natural airflow) situations.
>>>
>>> However, I have two questions
>>>
>>> 1) When modelling air permeability in such a way that I could relate it to
>>> real world pressurisation (q50) tests, I used a set of external wall
>>> 'cracks', which linked to the air flow network. Is there an easier way of
>>> doing this?
>>> 2) If I wish to model an MVHR unit, is there a plant option or air network
>>> option that I could use? If one doesn't exist, how do I go about creating
>>> it?
>>> For example, would the model work if I physical recreated the heat exchanger
>>> as two zones with a thin wall between, etc?
>>>
>>> Any indication of where to look for helpful examples or 'buttons to push'
>>> would be good.
>>>
>>> Regards
>>>    
>>> Matt
>>>    
>>>
>>>
>>> -----Original Message-----
>>> From: esp-r-bounces at lists.strath.ac.uk
>>> [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Achim Geissler
>>> Sent: 17 June 2013 18:12
>>> To: Archontiki, M.
>>> Cc: esp-r at lists.strath.ac.uk
>>> Subject: [esp-r] Re: Night-time ventilation
>>>
>>> Dear Maria
>>>
>>> there are four methods for ventilation simulation in ESP-r:
>>> a) via operations file, use "infiltration" for night time ventilation (note
>>> that "ventilation" in the operations files means "between zones", not
>>> to/from the ambient),
>>> b) by AIM ("air infiltration model" - I don't know anything about this, as I
>>> have never used it),
>>> c) via an external data file "tdf" and
>>> d) via an air flow network.
>>>
>>> The latter is the most sophisticated and takes the most "setting up" work
>>> (and likely the most knowledge of "what you are doing") - if your study is
>>> really focussing on night time ventilation, then this may be the best bet -
>>> you can open and close windows and doors via control, the actual air
>>> movement is calculated based on temperature differences (stack) and wind
>>> velocities.
>>>
>>> "a)" is quickly set up (by schedule in "operations file" menu") but has the
>>> significant drawback that the air changes are fixed by you and need not have
>>> any bearing on actual flows possible at any given time. "c)" is in effect a
>>> variant of "a)", however you can use smaller time steps ("a)" allows only
>>> hourly changing values). You could also use measurement values, with "c)".
>>>
>>> Hope that helps a bit.
>>>
>>> Regards
>>> Achim
>>>
>>>
>>> On Jun 17, 2013, at 6:01 PM, "Archontiki, M." <m.archontiki at student.tue.nl>
>>> wrote:
>>>
>>>> Dear all,
>>>>
>>>> Could please somebody give me a hint on how to import night time
>>> ventilation during cooling period? I have defined the infiltration and
>>> ventilation flow values for certain periods and I would like to have
>>> increased flow rates during non occupied hours, in the cooling months. I
>>> show the thermostatic control option but it applies to all day types and
>>> periods. Thank you in advance.
>>>> Kind Regards,
>>>> Maria Archontiki
>>>>
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>>>>
>>> achim.geissler at intergga.ch
>>>
>>>
>>>
>>>
>>>
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>> achim.geissler at intergga.ch
>>
>>
>>
>>
>>
>
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