[TRNSYS-users] Possible cause of mismatch between simulated room air temp from TRNSYS 17 and the experiment

[asmin aryal]

I did some experiments with the air handling unit to cool the experimental
room. I used the experimental data and simulated the room in TRNSYS 17. I
am simulating the same experimental room condition in type 56 with the type
508 a cooling coil with type 689 heat pipe around it.

The simulation I run was from the experimental data from approximately 2
days with 1 minute simulation time step. The experiment started on 26
October and ended on 28 October. So I set up the simulation start time at
13:09 p.m. October 26, 2020(432789 min) and end time as 28 October 23:59
(436320 minutes). I tried to match the particular date for the experiment
so that the Julian date will be the same and the calculation for the
radiation processor will match. Can I just start the simulation from 1 to
the end of the minute instead of giving a particular time on a daily
basis?

My inputs are experimental data from the weather station, chiller water
supply temperature, and mass flow rate. I wanted to compare the air
temperature inside the room from the simulation and the experiment. *The
room air temperature is not matching. I do not know why it is not matching.* I
also noticed that the air temperature has a high influence on the initial
value. Changing the initial value changes the room air temperature.

When I compare the experimental value of total radiation on north, south,
east, and west walls to the ones produced by the simulation via radiation
processor type 16i, they are almost the same. The cooling load of the
cooling coil from the simulation as compared to the experiment are
comparable.

I have used return air from the room (Temp, RH) from type 56 and connected
them to inlet air temp and RH of heat pipe inlet 1. The output of heat pipe
inlet 1 is connected to the type 508a cooling coil. The output of the
cooling coil is connected to the air temperature, relative humidity, and
airflow of the inlet 2 of the heat pipe. The output of the heat pipe is
connected to the inputs of the ventilation manager. I have created input
for the ventilation type manager to supply airflow(in terms of mass flow
rate), the temperature of the air supplied, and relative humidity in type
56 and connected it to the output from the heat pipe.

I have supplied experimental data for the mass flow rate and the supply
temperature of the fluid to type 508a with the help of type 9e.

I used type 9e to supply the weather data obtained from the weather station
(global radiation and diffused radiation Dry bulb temp, Relative humidity,
sky temperature, humidity ratio, ground reflectance), from the weather
station.  I have connected type 9e to radiation processor type 16i
to compute radiation on tilted surfaces i.e radiation on all the facades.

I used SketchUp to create the building model and I input all the things
that according to the experiment.


Looking forward to your invaluable comments and help.

Sincerely,

Ashmin Aryal
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