Adjusted system equipment sizing and Resolved nonlinear system warnings.

[GuowenLi-PhD]

Main changes:

1. Resized system equipment based on peak thermal loads:

• Boiler capacity = Peak heating load (4191kW) / Number of boiler (2)
• AHU fan pressure rise: to cover the maximum air system pressure drop (1.734 kPa)
• Chiller capacity = Peak cooling load (5500kW) / Number of chiller (3)
• Cooling tower (CT) is resized using the following procedure:

Q_cond = Q_eva*(COP_nominal+1)/COP_nominal where Q_eva is chiller capacity and Q_cond is cooling tower capacity
m_CW = Q_cond/cp/dTCW_nominal
P_CT_fan = 0.015*Q_cond which assumes the specific fan power (SFP) is 0.015kW per 1kW of CT heat rejected

• Resized designed nominal water mass flow rates of CHW, CW, and HW.
• Added a top-level sizing factor (alpha) of the overall system design capacity.

2. To avoid initialization failure, set initial economizer damper positions as open.
3. To avoid confusion, separated fan ON signals by occupied (always on) and unoccupied (conditional on).
4. Bounded the HW pump power output to non-negative values.

Simulation results are shown below:

• Annual out door air dry bulb temperature:

• Heating month (day 0 - 30):

• Shoulder month (day 60 - 90):

• Cooling month (day 190 - 220):

• One-year simulation:

The associated files of one-year simulation are attached.
dsin.txt
dslog.txt
dsfinal.txt

[GuowenLi-PhD]

Observation: After correcting the design hot water flow rates based on the reheat-valve-side calculation (refer to commit 7e201dc), there are no warning messages of hot water distribution system during simulation.
Note: Correct sizing procedures can help resolve nonlinear system simulation warnings or even failures.