[esp-r] Re: Amount of energy that passes through the surfaces

[Achim.geissler]

Dear Eduardo

two thoughts: 

a) The two numbers you give differ by approx. 0.2 percent. I would not say
this is really far apart given that the approaches in calculation of the
heat loss are most likely quite different.

b) Have you tried to take the given "energy stored" into account in your
comparison?

I seem to remember that there is some information on the output in the
CookBook. Have you taken a look there?

Best
Achim



--------- Original-Nachricht --------
 Von: "Eduardo Goncalves" 
 An: "esp-r at lists.strath.ac.uk" 
 Betreff: [esp-r]  Amount of energy that passes through the surfaces
 Datum: 20/12/10 22:31
 
   Hello ESP-r world,
   I Hope you can help me,  I am trying to determine the amount of energy
that passes through a wall. I have a fairly simple model (square with 10x10
each side and 3m height). I have a basic control with 25 degrees the whole
summer (June till September), there are no internal gains from occupants or
lights and I want to know the amount of gain/loss through the walls.  Once
simulated, if I go through Enquire about/Zone Energy Balance/Integrated over
time/Gain-Loss I have the following results,                
                    Gain         Loss    Infiltration air load          
0.000       0.000    Ventilation air load            0.000       0.000  
 Uncontr`d casual Occupt         0.000       0.000    Uncontr`d casual
Lights         0.000       0.000    Uncontr`d casual Equipt        
0.000       0.000    Thermal bridge (linear)         0.000       0.000  
 Storage at air point            0.925      -0.977    Opaque surf convec:
ext       233.485     -16.093    Opaque surf convec: ptn       157.405    
-33.853    Transp surf convec: ext         0.000       0.000    Transp surf
convec: ptn         0.000       0.000    Convec portion of plant       
44.617    -385.509    Totals                        436.433    -436.433     
I suppose that the gains from the walls would be 233.485+157.405= 390.989
Whrs, and losses 16.093+33.853 = 49.946 Whrs. (there’s no other source
of internal gain in the model).  So far so good, nevertheless, if I go
through Surface energy balance/Integrated over time/Gain-Loss/All Items, I
get something like,                              Facing Teste            
Facing outside                            Gain       Loss         
Gain       Loss    Conductive flux     111853.23   -16240.70  1745485.50
-1842903.13   Convective flux       3598.84   -53664.82     1333.83
-3128152.00   Longwave rad int     15327.17   -60134.77         --         
--   LW rad ext >bldg          --         --     476125.97  -244280.39   LW
rad ext >sky           --         --          0.00 -2835801.50    LW rad ext
>grnd          --         --      27968.51  -643154.69   Shortwave
rad.           0.00        0.00  6443323.00        0.00   Occupt casual
gn         0.00        0.00         --          --    Lights casual
gn         0.00        0.00         --          --    Equipt casual
gn         0.00        0.00         --          --   Controled
casual         0.00        0.00         --          --    Heat
stored          15333.66   -16072.75   720997.19  -720940.69 
 Plant                    0.00        0.00        0.00        0.00  
 Totals              146112.91  -146113.05  9415234.00 -9415233.00     for
each surface of the model (4 walls, ceiling and pavement).   Having those
values for each surface, I sum the losses of the surface facing inside
(392043Whrs), which would be the convective heat that is transferred to the
zone, i.e., gain and losses that comes from the Zone energy balance, as
referred to initially (Gain 390,989 kWhrs, and losses 49946 Whrs). The
problem is that the results are very different (392043Whrs/390989kWhs), and
I don’t know why. My suppositions must be wrong.  How can I actually
get the amount of energy that passes through the walls (gains and losses)? 

   Thanks for your help  -- 
Eduardo Gonçalves
+ 351 913 310 390
  
 
  
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