[esp-r] Re: Emissvity and airflow network

[Jon Hand]

answers below ::
________________________________________
From: esp-r-bounces at lists.strath.ac.uk [esp-r-bounces at lists.strath.ac.uk] On Behalf Of HUA SUO [surano1505 at hotmail.com]
Sent: 26 November 2012 23:52
To: esp-r at lists.strath.ac.uk
Subject: [esp-r]  Emissvity and airflow network

Hello ESP-r esperts, Could someone help me with the following questions?
1.       About the emissivity ,In material database, we are provided with “Emissivity out” “ Emissivity in”  choices. I made a small test , for a given material on a given surface, If I only reduce “ Emissivity out” , the simulation results remains the same. If I only reduce ” Emissivity in”, leaving “Emissivity out” the same as before, in result analysis the longwave radiation to sky will be reduced, while the temperature for this surface increases. Does this mean that if I change the “ Emissivity in” , “ Emissivity out “will be automatically changed as the same value of “ Emissivity in”? What can I do if I want to simulate an external Low-E coating to reduce the longwave to sky?

:: material surface properties are applied in the zone construction file for the outside layer of the construction (where the outside property
::  of the material is used and for the inside layer of the construction where the inside properties of the material are used.
:: you can double check this by using the model QA reporting facility

2.       About the airflow network .I coupled the simulation with an airflow network .However I found that the ambient temperature from the output of .mfr is half an hour “earlier” respect to the output of .res. While on the contrary I found when I inquire the heat storage in the air , the output from .res is half an hour “earlier” respect to the calculation from the .mfr output(I made the calculation based on the output from .mfr). I run the simulation 1 step per hour with hourly result integration.

:: a 1 hour timestep is a VERY LONG TIME for a model with a flow network.  Most people would be running assessments at
:: a shorter timestep (say 5 or 10 minutes).  The time shift - is that looking at a graph or is it looking at timestep reports?

3.   Something very strange. I have an airflow network including an fixed temperature node  with heating setpoint at 18 degree. It works well when I set this fixed temperature node to be 20 degree ,but when I changed it to be 50 degree, there is no flow anymore .This is the only parameter I changed. Why? I appreciate if someone could give me a hand, also I can send you the model I made.

:: does it work at 30C or 40C?
:: an alternative is to create a separate zone to act as a mixing box (~1.5m cube) and apply a zone control to that
:: to maintain some temperature(s) and include it in the flow network so that air enters the mixing box, is tempered
:: and then is moved into the occupied space.  
:: -Jon Hand

Best Regards,


Suo Hua

Ph.D Student in Tecnologia e Progetto per l'Ambiente Costruito/Technology and Design for Environment and Building

Il Dipartimento B.E.S.T.Dipartimento di Scienza e Tecnologie dell’Ambiente Costruito/ The Department of Building Environment Science & Technology

Politecnico Di Milano

Email:hua.suo at mail.polimi.it<mailto:Email%3Ahua.suo at mail.polimi.it>