[esp-r] Re: Some bugs in subsys.F ?

[Ferguson, Alex]

Greetings from windy Ottawa!
 
I'm the author of recent changes [r6485] to subsys.F that alter use of
the PREC5N variables. In this revision, I modified MZVNT to allow more
flexibility in specifying infiltration air flow. These changes permit
switching from one air flow computation method to another (AIM-2,
scheduled flow and air-flow network) mid-simulation depending on the
operating conditions in the building. 
 
Prior to r6485, ESP-r held air infiltration and ventilation flow
conductance in the CVIN and CVVN arrays, in common PREC5N.  By default,
ESP-r assumes that the air flow rates are specified by hourly schedules
in the .opr file. CVIN and CVVN thus contain up to 72 separate flow
rates for each zone: one for each hour (1-24) in each of the three day
types (weekday/Saturday/Sunday). The routine MZVENC establishes values
CVIN and CVVN prior to commencing simulation using the static air change
rates specified in the .opr file.  During the simulation, ESP-r reads
the infiltration and ventilation data for the current hour and day type
from these arrays.
 
Rather than create a specific data structure, the air flow network
exploited the same variables for imposing network-computed infiltration
and ventilation flows on the building thermal model. There two
deficiencies with this approach:

*	
	It's cumbersome. Because CVIN and CVVN are designed to hold
hourly schedules, the air-flow network had to locate the correct array
location (that is, the current day type and hour) to save the data in,
even though these parameters had no relevance to the air-flow network
computation. This not only requires extra code; it also obfuscates the
purpose of the CVIN/CVVN arrays.
*	
	It erases the original schedules held in CVIN and CVVN.  These
arrays are populated prior to simulation by routine MZVENC. By
repurposing them, the air flow network overwrites the original flow
schedules with time-step computed values. This prevents re-imposing the
.opr schedules mid-simulation-a key objective in our work. 

For these reasons, I elected to revise routines MZVENT and MFLW2B to use
dedicated variables when imposing infiltration and ventilation on the
building thermal domain.  I introduced a new common block AfnToBldData
common for this purpose. 
 
Regarding your observations Sara, I'm not sure I understand your
comments. When the opr schedule or AIM-2 models are in effect,
ventilation is still governed by the hourly ventilation schedule-and
therefore should be established via CVVN as per line 1769. I'm also
unsure what you're suggesting regarding line 1897. The if statement has
two clauses: bAFN = TRUE for air flow networks, and an else clause
otherwise. Am I missing something?
 
Thanks,
 
- Alex 
Alex Ferguson
Housing, Buildings and Communities Group
CanmetENERGY
Natural Resources Canada
P:+1 613 995 3294
F:+1 613 996 9909
Alex.Ferguson at NRCan-RNCan.gc.ca


 
 
 
 

________________________________

From: Joe Clarke [mailto:joe at esru.strath.ac.uk] 
Sent: April 28, 2011 12:02
To: core_developers at espr.list.cvsdude.com
Subject: Re: AW: Some bugs in subsys.F ?


Dear All

In relation to Sara's recent post below, I have made changes to ESP-r to
enable the coupling of non-air flow networks to building models to allow
the use of ESP-r's building-side features in plant modelling. I use the
variables in common PREC5N extensively. The changes are at present
resident in my branch and not yet integrated in development_branch.

Regards,

Joe




	I want to only give a heads up in a mistake occurred in
development_branch which should be fixed. It reflected in commit log
6618. Since the fluid flow network solver no longer changes the PREC5N
variables and data is stored in the dedicated AfnToBldData common
variables, the calculation of CV1, CV2 and other related parameters
there for AIM2 in subsys.F should be changed (line 1769 in
development_branch). Using the current version cannot calculate CVVF in
the mode of AIM2 or OPR, so they have to be changed (which you can see
in commit log 6618). 
	
	Another issue is in CVVFM modification line 1902. The if
statement which is in line 1897 is wrong, it doesn't account for other
type of air flow network which should consider them. It is also
reflected in commit log 6618.
	
	Best Regards,
	
	Sara Nikoofard
	Room C254A, Department of Mechanical Engineering, 
	Dalhousie University, Halifax, NS
	Phone: (902)494-3165
	email: s.nikoofard at dal.ca
	


-- 
Professor J A Clarke                email: joe at esru.strath.ac.uk
ESRU, Dept. of Mechanical Eng.           phone: +44 141 548 3986
University of Strathclyde                  fax: +44 141 552 5105
Glasgow G1 1XJ, UK                 http://www.esru.strath.ac.uk/
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