Modelica: MixedAir heating/cooling load components calculation.

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Hi everyone,

I am trying to directly calculate the energy balance (sensible heating/cooling) for the air node in a MixedAir model to determine the exact heating/cooling load components.

To evaluate the heat balance, I considered the following key factors:

1) Internal Convective Heat Gain Rate

2) Surface Convection Rate

3) Outdoor Air Transfer Rate

4) System Air Transfer Rate

Based on this, I assumed the following balance equation:

System Air Transfer Rate = Internal Convective Heat Gain Rate + Surface Convection Rate + Outdoor Air Transfer Rate

Here is how I mapped these factors to the specific Modelica output variables in my model:

1. Internal Convective Heat Gain Rate: roo.air.QCon_flow

2. Surface Convection Rate: roo.air.convConExt.Q_flow + roo.air.convConExtWin.Q_flow + roo.air.convConWin.air.Q_flow + roo.air.convConBou.Q_flow

3. Outdoor Air Transfer Rate: roo.port[2].h_outflow * roo.port[2].m_flow

4. System Air Transfer Rate: preHea.Q_flow

I plotted the sum of the components (1 + 2 + 3) and compared it against the system air transfer rate (4) to verify the energy balance. However, the graphs do not perfectly match, and there is a noticeable discrepancy between the two.

Could anyone advise on what I might be missing? Thank you.

ps. I am attaching the .mat and csv result files. .mat file & result.xlxs