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Night ventilation - Page 4

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Posted by daestrom on November 26, 2006, 6:10 pm
 


Yes, but apparently your GW-BASIC can't.  I don't see any
statement/calculation that supports your claim that it's in there and I
missed it.  I'll repeat my previous question, please "Identify the line of
code that considers solar input in your original listing" that considered
solar heat gain.



When the model 'reasonably' reflects reality.  Since you included electrical
heat gain, you must have the opinion that it's 'significant'.  Yet you don't
seem to grasp how it's variation over the day/night cycle would affect the
outcome.  Simple experimentation with the model (I suggested one 'profile'
you might try, it wouldn't take more than two lines of code to add) would
reveal just how important the profile might be.

A famous quote, "All models are wrong, however some models are useful."  But
to be useful, it should predict real-world results with reasonable accuracy.
That means when you remove the line 180 to get the 'non-ventilated' version,
if your model is any good it would be predicting the actual, historical
indoor air temperature swings.  Some how, I think your model's predictions
of 92+ F all day/night are not at all correct.  Ergo, your model needs more
refinements before it can produce useful data.

Instead, you seem to "pick and choose" what factors to include (when
heating, you consider animal and solar gain, when cooling you don't??).  Do
you have any data that swayed your decisions, or is it just 'gut feeling'?
Or perhaps you just left them out because you 'reinvent the wheel' with each
new program you write?  When challenged about what choices you've made, you
try to deflect them with, "Where should we stop...."  As if to say, "Well we
can't model everything, so I had to draw the line somewhere."  But why did
you draw it 'there'?  Like I said before, Garbage-In/ Garbage-Out.

Of course, some programming languages would make it easier to re-use code.
So your models could be refined over time to include more and more effects
without having to 'start from scratch' each time (and risk leaving out
important factors).  Then you could just use site-specific and
house-specific data to adjust the refined model to a new calculation.


Changing the subject?  You chose cooling in July.


It would seem the burden of proof is on you to demonstrate your ventilation
idea.  Your model is not proof.  You compared your ventilation mode with
zero ventilation.  Put four 'double-hung' windows (say, an opening of 30" x
30" each) on the first floor and four more on the second floor (two facing
the breeze, two on the leeward side of each floor), and a 3 mph breeze into
your model (without the ventilation scheme) and run it.  Shut them in the
morning when outdoor temperature rises above room temperature, and re-open
them in the evening when outdoor temperature drops.  Let us see how the
temperatures fair compared to just your ventilation scheme.  Keep all the
other factors the same so we can see what the results are of comparing just
windows versus your 'ventilation' idea.

daestrom


Posted by nicksanspam on November 26, 2006, 6:47 pm
 


I suggest you look again.

Nick


Posted by Jeff on November 27, 2006, 12:51 pm
 nicksanspam@ece.villanova.edu wrote:


   I don't see it either. All I see is an outdoor temperature and
internal heat from electrical use.

   I rarely read the code you post (programmers hate "GOTO"), but I did
this time to see what all the fuss was about.

   Jeff


Posted by nicksanspam on November 27, 2006, 12:54 pm
 

I suggest you look again.

Nick


Posted by Jeff on November 27, 2006, 7:21 pm
 nicksanspam@ece.villanova.edu wrote:

   Has anybody ever told you that you can be completely maddening.

   You've taken the time to comment the code and it is only handfull of
lines.

20 PI=4*ATN(1)
30 W=2*PI/24'angular freq (radians)
40 C200'house thermal mass (Btu/F)
50 G0'house conductance to outdoors (Btu/h-F)
60 AV=4'vent area (ft2)
70 HV'vent height difference (feet)
80 ECON`0'internal electrical use (kWh/month)
90 DGAIN412*ECON/30'internal heat gain (Btu/day)
100 HGAIN=DGAIN/24'internal heat gain (Btu/h)
110 TRp.2'average July temp in Rochester NY (F)
120 FOR D= 1 TO 10'simulate for 10 average days
130 FOR H=0 TO 23
140 Tp.2+(80.7-70.2)*SIN(W*H)'outdoor temp (F)
150 Q=HGAIN+(T-TR)*G'heatflow from walls into room (Btu)
160 IF T>TR THEN CFM=0:GOTO 190'no venting
170 CFM.6*AV*SQR(HV*(TR-T))'vent airflow (cfm)
180 Q=Q-CFM*(TR-T)'lower heat gain by venting
190 TR=TR+Q/C'new house temp (F)
200 IF D AND H MOD 2 = 0 THEN PRINT T,TR,CFM
210 NEXT H
220 NEXT D

There is no solar heat gain. Only an HGAIN derived from kWHr consumption
and a heat derived from house conductance and proportional to the
difference between indoor and outdoor temperature. Pwerhaps you have no
windows or you are considering that solar heat gain is factored in here:

140 Tp.2+(80.7-70.2)*SIN(W*H)'outdoor temp (F)
150 Q=HGAIN+(T-TR)*G'heatflow from walls into room (Btu)

or here:

80 ECON`0'internal electrical use (kWh/month)

But that would appear to be a poor assumption and is not noted as such.
  You may be right, but the current conventional wisdom is that you've
gone off your rocker on this and you are being unresponsive.

   Jeff


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