[TRNSYS-users] Questions about VENTILATION Type & HVAC components

[David BRADLEY]

Chou,
   My apologies for the delay in getting back to you.


> 1. As you mentioned in the first simulation with Type 56----to get a 
> basic idea of how much energy the building will consume, use the 
> VENTILATION Type with outside air and use the COOLING Type to define 
> set up temperature. I set the VENTILATION Type with the conditioned 
> air (temperature 16C), I think the cooling load will change, but the 
> results don't change significantly (<10%). Also in the VENTILATION 
> Type, I wonder the air change rate refers to the fresh air or the 
> mixed air (flow of fresh + return air) if the VENTILATION is set up as 
> outside.
Type56's VENTILATION is quite simple; it is just an air flow rate 
(specified in air changes in v16, and specified as either an air change 
rate or a mass flow rate in v17) with the temperature and RH that you 
specify. There is no assumption at all about whether it is outside air 
or return air. From your description of adding a VENTILATION type with a 
temperature of 16C, my guess is that your cooling load was reduced by 
adding a cool stream of air to the room (provided that your room 
setpoint is above 16C of course). The size of the reduction would depend 
upon how much air you added. If you specified a small amount of air, the 
reduction would be small. If you specify the conditions of the 
VENTILATION types as "outside" then Type56 simply adds the quantity of 
air that you specified and uses the ambient conditions that it already 
knows from the ambient temperature and RH inputs to the Type. In this 
case, you are adding only the flow of fresh air. In order to add a mixed 
flow, you would have to specify the air change rate of the mixed flow 
and the conditions of the mixed flow, probably as additional INPUTS to 
Type56.
> 2. In the file of BALANCE summary, the BAL_ENERGY is supposed to be 
> zero, according to the Manual. However my results indicate that this 
> item is up to 10^6 kJ, and it doesn't equal to the sum of the other 
> items. And there is not too much details about it on the manual.
I would need to take a look at the input file in order to determine 
whether or not this is expected.
> 3. I try to use Type 53 + Type 52 as the AC components of the Type 56, 
> But when I run the model, an error occurs, which says,
>
> TRNSYS Message 350: Unable to open the file associated with an 
> ASSIGNED logical unit number. Please check the statement and make sure 
> that the file exists at the specified location. Reported information: 
> Logical Unite=36, FileName=.
>
the fact that the filename is blank in the error message is probably an 
indication that you didn't specify a performance data file for Type53. 
Try opening Type53 and selecting the "External Files" tab to make sure 
that a file is referenced. An example file can be found in:

.Trnsys17\Examples\Data Files\Type53-ParallelChillers.dat. If you are 
using Trnsys16, I can send you a copy of the file.

Kind regards,
  David

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

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