[esp-r] difference between TRNSYS and ESP-r load value

[NALIN SWAROOP]

Hello all

I have modeled a (50*15*27) 42 zone building in both TRNSYS 16 and ESP-r
11.6 but large differences are coming in cooling load values, for TRNSYS
it is around 1400 GJ annual load but for ESP-r it is around 2200 GJ annual
load, at first I thought I made some mistake in modeling and construction
parameters for both softwares, but I have checked many times and all the
details of geometry, heat transfer coefficients, glazing data,construction
data and weather data are exactly same and I need to come up with an
explanation as to why these differences are coming.
I have seen the ANSI/ASHRAE standard 140-2001 which compares bestcases for
different simulation softwares and I have tried to benchmark it and the
results match with those given in the standard but the problem is as I go
on increasing the zones,increase the size of the model add glazings the
total value of heating and cooling loads vary a lot.
Also I found one peculiar thing that in TRNSYS if I model a room with
three glazing orientations i.e west, east, north-south. I get maximum load
value for east side window and minimum for north-side but if same room I
model in ESP-r I get maximum load value for north-south side I dont why this
difference is there I am using the same weather file.
At last I want to know if some study has been done which gives the
mathematical differences between TRNSYS and ESP-r and tells the effect of
these mathematical differences through an example model, all I know is
ESP-r takes the rigorous heat balance approach and TRNSYS models its long
wave, short wave radiation and convection through star network system.
Sorry to bother you all with a long question
Nalin

Regards

Nalin