.Buildings.Examples.Tutorial.Boiler

Information

This package contains examples with step-by-step instructions for how to build a system model for a boiler with a heat load as shown in the figure below. The pressure drops of the individual flow branches and the temperatures correspond to design conditions. The heating system shall be designed to provide 20 kW, which is the load needed at -10°C outdoor temperature. This load already takes into account the heat required for air infiltration and ventilation. Using this load and the temperatures shown in the schematic drawing, the nominal mass flow rates of the individual flow branches should be computed. From 8:00 to 18:00, there is an internal heat gain of 4kW, which should not be accounted for when sizing the system.

The room volume is 180m³. To approximate the thermal storage effect of furniture and building constructions, the heat capacity of the room should be increased by a factor of three. (Modeling a detailed room heat transfer as implemented in Buildings.ThermalZones.Detailed is out of scope for this tutorial.)

The space heating shall be switched on if the outdoor temperature is below 16°C and the room temperature is below 20°C. It shall be switched off if either the outdoor temperature is above 17°C or the room temperature is above 21°C.

The model consists of

1. a room with a heating load, approximated as steady-state heat transfer with the environment,
2. a heating loop with a constant bypass and a three-way valve, which is modulated to track the room temperature set point, and
3. a boiler loop with constant mass flow rate, boiler on/off control and control valve to ensure a minimum return water temperature.

To explain the implementation of this model, the model has been created in the following stages:

1. Buildings.Examples.Tutorial.Boiler.System1 implements the room model without any heating.
2. Buildings.Examples.Tutorial.Boiler.System2 adds a radiator that is fed with water at a constant temperature and flow rate. The pump is switched on and off depending on the room temperature.
3. Buildings.Examples.Tutorial.Boiler.System3 adds the boiler circuit with open loop control for the boiler and the mixing valves.
4. Buildings.Examples.Tutorial.Boiler.System4 adds closed loop control for the boiler and the pumps.
5. Buildings.Examples.Tutorial.Boiler.System5 adds closed loop control for the two valves.
6. Buildings.Examples.Tutorial.Boiler.System6 replaces the constant outdoor temperature with weather data from a file, and changes the valve control from P-control to PI-control.
7. Buildings.Examples.Tutorial.Boiler.System7 replaces the boiler and pump control using a state machine.

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