[esp-r] Re: R: Mean Radiant Temperature; esp-r Digest, Vol 22, Issue 15
Paul Strachan
paul at esru.strath.ac.uk
Thu May 22 23:03:49 BST 2008
Dear Francesco,
As far as I can ascertain from the ESP-r code, the MRT calculation does
not take account of emissivity. The default MRT is simply the area
weighted surface temperatures (subroutine MOMNRD in temps.F in esrures).
It is possible to specify MRT calculations at specific points in the
zone (using sensor "cubes"), in which case the calculation includes
viewfactors and 4th power radiant exchange (subroutine SENMRT in temps.F
in esrures) - but again emissivity is not included. Although rather
out-of-date in terms of the user interface, the following publication on
the ESRU website gives the basis of the method for user-defined
positions for MRT sensors: http://www.esru.strath.ac.uk/Documents/ESPmrt.pdf
Regards
Paul
Francesco Frontini wrote:
> Dear Jon,
> Ok,
> but where I can found the fomula used by ESP-r for the MRT calculation?
> Best regards
> Francesco
>
> -----Messaggio originale-----
> Da: esp-r-bounces at lists.strath.ac.uk
> [mailto:esp-r-bounces at lists.strath.ac.uk] Per conto di
> esp-r-request at lists.strath.ac.uk
> Inviato: martedì 20 maggio 2008 13.00
> A: esp-r at lists.strath.ac.uk
> Oggetto: esp-r Digest, Vol 22, Issue 15
>
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> Today's Topics:
>
> 1. Mean Radiant Temperature (francesco.frontini at polimi.it)
> 2. Re: Mean Radiant Temperature (Geissler Achim)
> 3. R: Mean Radiant Temperature (Francesco Frontini)
> 4. Re: R: Mean Radiant Temperature (Geissler Achim)
> 5. Re: R: Mean Radiant Temperature (Jon Hand)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 20 May 2008 08:45:52 +0200
> From: francesco.frontini at polimi.it
> Subject: [esp-r] Mean Radiant Temperature
> To: esp-r at lists.strath.ac.uk
> Message-ID: <20080520084552.y2yaryo9kcs880ks at webmail.polimi.it>
> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
> format="flowed"
>
> Dear All,
> I have a question about MRT.
>
> We want to assess the impact on the operative temperature in an office if we
> use an internal blind with a low-emissivity coating (0,5 emissivity for
> indoor-facing surface) instead of 0.9 emissivity.
> We made two different simulation: static (with WIS program) and Dynamic
> (ESP-r).
>
> The results from WIS and from ESP-R for the blind surface temperature are
> consistent (blind temperature about 5K higher for the low-emissivity blind).
> However, the mean radiant temperature at a position close to the blind (0.5
> m in ESP-R) is lower for the high-emissivity blind than the low-emissivity
> blind with the ESP-R calculation.
> Could you please send me the formula that ESP-r uses for the MRT
> calculation? Is there any approximation that would not be appropriate for
> low-emissivity surfaces?
>
> I model the double glazing fa?ade with the internal blind like a single
> construction (no air-ventilation between the glass and the blind). I set the
> U-value for each fa?ade construction (it is similar but not identical for
> the two different solutions, U=0,985+-0,005, obtained from the WIS
> calculation), and the g-value. What changes in the model is the emissivity
> of the indoor-facing surface of the blind
> (e=0,9 for the first case and e=0,5 for the second one!), whereas the
> solar-optical properties remain the same for the two blinds. In the WIS
> model, the emissivity of the two blind surfaces is specified separately.
> For both blinds, the emissivity of the outdoor-facing surface in the WIS
> model is 0.9.
>
>
> Looking forward to your answer and thanking you for your help.
> Any advice and help on this will be much appreciated.
>
> Francesco Frontini
>
>
>
>
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 20 May 2008 09:22:39 +0200
> From: "Geissler Achim" <Achim.Geissler at josef-gartner.ch>
> Subject: [esp-r] Re: Mean Radiant Temperature
> To: <francesco.frontini at polimi.it>, <esp-r at lists.strath.ac.uk>
> Message-ID:
> <5410907208A9F149ADB6E44744892B3C45EBE8 at sgartgum1.gart.intra>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear Francesco,
>
>
>> We want to assess the impact on the operative temperature in an office
>> if we use an internal blind with a low-emissivity coating (0,5
>> emissivity for indoor-facing surface) instead of 0.9 emissivity.
>> We made two different simulation: static (with WIS program) and
>> Dynamic (ESP-r).
>>
>
>
>> The results from WIS and from ESP-R for the blind surface temperature
>> are consistent (blind temperature about 5K higher for the
>> low-emissivity blind).
>>
> That is good news.
>
>
>> However, the mean radiant temperature at a position close to the blind
>> (0.5 m in ESP-R) is lower for the high-emissivity blind than the
>> low-emissivity blind with the ESP-R calculation.
>>
>
> As the mean radiant temperature is defined by view factors and surface
> temperature, only, all is well, no? The low-e blind has a higher
> temperature, thus I would expect the mean radiant temperature close to the
> blind to be higher. That is what you seem to have obtained as result?
>
> Best regards,
> Achim
>
>
>
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 20 May 2008 10:35:15 +0200
> From: "Francesco Frontini" <francesco.frontini at polimi.it>
> Subject: [esp-r] R: Mean Radiant Temperature
> To: "'Geissler Achim'" <Achim.Geissler at josef-gartner.ch>,
> <esp-r at lists.strath.ac.uk>
> Message-ID:
>
> <!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAABgAAAAAAAAAru7KqoPmvUiwJBhxMD9pLMKAAAAQ
> AAAAq+fYsqTr4E+5QjbiDeTAbQEAAAAA at polimi.it>
>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear Achim
> Yes I have obtained a MRT, close to the blind, higher for the solution with
> low-e blind (that has a higer surface temperature). But for my opinion the
> MRT has to take into account not only the view factor and the temperature of
> the surface but also the emissivity. For that reason I'm also supposing that
> with a low emmissivity also the MRT should be low (for exemple if the view
> factor is the same: 43,88?x0,9>48.21?x0,5! Where the formula is
> (T1(?C)blind)*(emissivity(1))>(T2(?C)blind)*(emissivity(2))!!!). It's not
> correct?
>
> Best regards,
> Francesco
>
> -----Messaggio originale-----
> Da: Geissler Achim [mailto:Achim.Geissler at josef-gartner.ch]
> Inviato: marted? 20 maggio 2008 9.23
> A: francesco.frontini at polimi.it; esp-r at lists.strath.ac.uk
> Oggetto: RE: [esp-r] Mean Radiant Temperature
>
> Dear Francesco,
>
>
>> We want to assess the impact on the operative temperature in an office
>> if we use an internal blind with a low-emissivity coating (0,5
>> emissivity for indoor-facing surface) instead of 0.9 emissivity.
>> We made two different simulation: static (with WIS program) and
>> Dynamic (ESP-r).
>>
>
>
>> The results from WIS and from ESP-R for the blind surface temperature
>> are consistent (blind temperature about 5K higher for the
>> low-emissivity blind).
>>
> That is good news.
>
>
>> However, the mean radiant temperature at a position close to the blind
>> (0.5 m in ESP-R) is lower for the high-emissivity blind than the
>> low-emissivity blind with the ESP-R calculation.
>>
>
> As the mean radiant temperature is defined by view factors and surface
> temperature, only, all is well, no? The low-e blind has a higher
> temperature, thus I would expect the mean radiant temperature close to the
> blind to be higher. That is what you seem to have obtained as result?
>
> Best regards,
> Achim
>
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 20 May 2008 11:33:33 +0200
> From: "Geissler Achim" <Achim.Geissler at josef-gartner.ch>
> Subject: [esp-r] Re: R: Mean Radiant Temperature
> To: "Francesco Frontini" <francesco.frontini at polimi.it>,
> <esp-r at lists.strath.ac.uk>
> Message-ID:
> <5410907208A9F149ADB6E44744892B3C45EC09 at sgartgum1.gart.intra>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear Francesco,
> the definitions I know of for mean radiant temperature do not take
> emissivity into account. The interesting question probably is, is the
> measure "MRT" useful for environments with large differences in emissivity?
> Of course, for radiation heat transfer, the emissivity is important (that is
> what I think you want to describe?).
> I would assume that the definition of MRT is based on the "normal" case,
> that all surfaces of an indoor space have an emissivity of approx. 0.9.
> Thus, the description of the radiative surroundings by temperature alone is
> sufficient.
> For your case, you may need to define a "new" MRT - maybe more a "mean
> radiant heat exchange" type of coefficient (or try PPD / PMV calculations,
> however, these also use standard mean radiant temperature for their
> calculation).
> Regards,
> Achim
>
>
>
>> -----Original Message-----
>> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-
>> bounces at lists.strath.ac.uk] On Behalf Of Francesco Frontini
>> Sent: Tuesday, May 20, 2008 10:35 AM
>> To: Geissler Achim; esp-r at lists.strath.ac.uk
>> Subject: [esp-r] R: Mean Radiant Temperature
>>
>> Dear Achim
>> Yes I have obtained a MRT, close to the blind, higher for the solution
>> with low-e blind (that has a higer surface temperature). But for my
>> opinion the MRT has to take into account not only the view factor and
>> the temperature of the surface but also the emissivity. For that
>> reason I'm also supposing that with a low emmissivity also the MRT
>> should be low (for exemple if the view factor is the same:
>> 43,88?x0,9>48.21?x0,5! Where the formula is
>> (T1(?C)blind)*(emissivity(1))>(T2(?C)blind)*(emissivity(2))!!!). It's
>> not correct?
>>
>> Best regards,
>> Francesco
>>
>> -----Messaggio originale-----
>> Da: Geissler Achim [mailto:Achim.Geissler at josef-gartner.ch]
>> Inviato: marted? 20 maggio 2008 9.23
>> A: francesco.frontini at polimi.it; esp-r at lists.strath.ac.uk
>> Oggetto: RE: [esp-r] Mean Radiant Temperature
>>
>> Dear Francesco,
>>
>>
>>> We want to assess the impact on the operative temperature in an
>>> office if we use an internal blind with a low-emissivity coating
>>> (0,5 emissivity for indoor-facing surface) instead of 0.9 emissivity.
>>> We made two different simulation: static (with WIS program) and
>>> Dynamic (ESP-r).
>>>
>>> The results from WIS and from ESP-R for the blind surface
>>> temperature are consistent (blind temperature about 5K higher for
>>> the low-emissivity blind).
>>>
>> That is good news.
>>
>>
>>> However, the mean radiant temperature at a position close to the
>>> blind
>>> (0.5 m in ESP-R) is lower for the high-emissivity blind than the
>>> low-emissivity blind with the ESP-R calculation.
>>>
>> As the mean radiant temperature is defined by view factors and surface
>> temperature, only, all is well, no? The low-e blind has a higher
>> temperature, thus I would expect the mean radiant temperature close to
>> the blind to be higher. That is what you seem to have obtained as result?
>>
>> Best regards,
>> Achim
>>
>>
>>
>> _______________________________________________
>> esp-r mailing list
>> esp-r at lists.strath.ac.uk
>> http://lists.strath.ac.uk/mailman/listinfo/esp-r
>>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 20 May 2008 11:36:21 +0100
> From: Jon Hand <jon at esru.strath.ac.uk>
> Subject: [esp-r] Re: R: Mean Radiant Temperature
> To: "Geissler Achim" <Achim.Geissler at josef-gartner.ch>, "Francesco
> Frontini" <francesco.frontini at polimi.it>,
> <esp-r at lists.strath.ac.uk>
> Message-ID:
> <B94620A0857DFE4DB194C4A2DBDC088F8B5FD6 at BE-SCAM2.ds.strath.ac.uk>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> There is a radiant asymmetry report as part of the comfort report and I
> think that will be taking account of the emissivity.
>
> There is an esp-r model which deals with a heated ceiling panel and location
> specific comfort for a patient in a bed which needs to be added as an
> exemplar model.
>
> -Jon Hand
>
>
> -----Original Message-----
> From: esp-r-bounces at lists.strath.ac.uk on behalf of Geissler Achim
> Sent: Tue 5/20/2008 10:33 AM
> To: Francesco Frontini; esp-r at lists.strath.ac.uk
> Subject: [esp-r] Re: R: Mean Radiant Temperature
>
> Dear Francesco,
> the definitions I know of for mean radiant temperature do not take
> emissivity into account. The interesting question probably is, is the
> measure "MRT" useful for environments with large differences in emissivity?
> Of course, for radiation heat transfer, the emissivity is important (that is
> what I think you want to describe?).
> I would assume that the definition of MRT is based on the "normal" case,
> that all surfaces of an indoor space have an emissivity of approx. 0.9.
> Thus, the description of the radiative surroundings by temperature alone is
> sufficient.
> For your case, you may need to define a "new" MRT - maybe more a "mean
> radiant heat exchange" type of coefficient (or try PPD / PMV calculations,
> however, these also use standard mean radiant temperature for their
> calculation).
> Regards,
> Achim
>
>
>
>> -----Original Message-----
>> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-
>> bounces at lists.strath.ac.uk] On Behalf Of Francesco Frontini
>> Sent: Tuesday, May 20, 2008 10:35 AM
>> To: Geissler Achim; esp-r at lists.strath.ac.uk
>> Subject: [esp-r] R: Mean Radiant Temperature
>>
>> Dear Achim
>> Yes I have obtained a MRT, close to the blind, higher for the solution
>> with low-e blind (that has a higer surface temperature). But for my
>> opinion the MRT has to take into account not only the view factor and
>> the temperature of the surface but also the emissivity. For that
>> reason I'm also supposing that with a low emmissivity also the MRT
>> should be low (for exemple if the view factor is the same:
>> 43,88?x0,9>48.21?x0,5! Where the formula is
>> (T1(?C)blind)*(emissivity(1))>(T2(?C)blind)*(emissivity(2))!!!). It's
>> not correct?
>>
>> Best regards,
>> Francesco
>>
>> -----Messaggio originale-----
>> Da: Geissler Achim [mailto:Achim.Geissler at josef-gartner.ch]
>> Inviato: marted? 20 maggio 2008 9.23
>> A: francesco.frontini at polimi.it; esp-r at lists.strath.ac.uk
>> Oggetto: RE: [esp-r] Mean Radiant Temperature
>>
>> Dear Francesco,
>>
>>
>>> We want to assess the impact on the operative temperature in an
>>> office if we use an internal blind with a low-emissivity coating
>>> (0,5 emissivity for indoor-facing surface) instead of 0.9 emissivity.
>>> We made two different simulation: static (with WIS program) and
>>> Dynamic (ESP-r).
>>>
>>> The results from WIS and from ESP-R for the blind surface
>>> temperature are consistent (blind temperature about 5K higher for
>>> the low-emissivity blind).
>>>
>> That is good news.
>>
>>
>>> However, the mean radiant temperature at a position close to the
>>> blind
>>> (0.5 m in ESP-R) is lower for the high-emissivity blind than the
>>> low-emissivity blind with the ESP-R calculation.
>>>
>> As the mean radiant temperature is defined by view factors and surface
>> temperature, only, all is well, no? The low-e blind has a higher
>> temperature, thus I would expect the mean radiant temperature close to
>> the blind to be higher. That is what you seem to have obtained as result?
>>
>> Best regards,
>> Achim
>>
>>
>>
>> _______________________________________________
>> esp-r mailing list
>> esp-r at lists.strath.ac.uk
>> http://lists.strath.ac.uk/mailman/listinfo/esp-r
>>
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