Cooling Capacity of Air-Chiller Decrease as the Temperature Rises (hottest simulation day)

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Hello evryone,

I am modeling a real-case refrigerated warehouse that is composed of 13 zones, 12 walk-in coolers, and a loading zone.

I defined 2 refrigeration systems: the east and west systems.

Eastern System:

• All 6 eastern air-chillers with a cooling capacity of 32 kW each + Loading zone air-chiller with 20.9 kW
• 1 condenser
• 5 compressors of 28.4 kW each
• 1°C as setpoint

The same thing applies to the Westers System except for the Loading zone air-chiller.

I run the model on the hottest day of the year, where the maximum temperature reaches 43°C.

The problem is that the cooling capacity of the loading zone's air-chiller decries during the day from 11 a.m. to 18 (figure below), and I have no idea why.

Fig1: Loading Zone Total cooling Rate and Condencing Temperature

I thought that if the compressors work at maximum capacity and if the condensing temperature rises, maybe it affects the system cooling capacity, so I plotted the eastern compressor group power consumption (figure below), and the group is not working at maximum.

Fig2: Estern Compressors Power Consumption

...

I then added another compressor to the group + augmenting the air-chiller capacity from 20.6 kW to 32 kW, and the problem was solved, but the model is not representing the real-case warehouse.

Fig3: Loading Zone Total cooling Rate and Condencing Temperature after adding a compressor N° 6 and Changing the air-chiller cooling capacity

Fig4: Estern Compressors Power Consumption after adding a compressor N° 6 and Changing the air-chiller cooling capacity

What I did then was change the simulation day to a day less hot, and the problem was solved without adding a compressor or augmenting the cooling capacity of the air-chiller.

Fig5: Loading Zone Total cooling Rate and Condensing Temperature on a day less hot

I don't know why this problem occurs and why the compressors do not work at maximum (especially compressor 5 CP5) to cover cooling capacity.

Any advice or suggestions you could provide would be immensely helpful.

Thanks!