This example demonstrates the implementation of a building that has the following properties:

There are two rooms. (For simplicity, we only modeled two rooms, but more could be added.) Each room is modeled using a dynamic model for the heat transfer through the opaque constructions. The room roo1 has a south- and west-facing window, the room roo2 has a south- and east-facing window. The rooms are modeled as if they were in an intermediate floor, with the same temperature above and below the room. The rooms share one common wall. The north facing wall is modeled as a partition wall, i.e., both surfaces have the same boundary conditions. Weather data are used from Chicago.

There is a hydronic heating system with a boiler, a storage tank and a radiator with a thermostatic valve in each room. The supply water temperature setpoint is reset based on the outside temperature. A three-way-valve mixes the water from the tank with the water from the radiator return. The pump has a variable frequency drive that controls the pump head.

A finite state machine is used to switch the boiler and its pump on and off. The boiler and pump are switched on when the temperature at the top of the tank is less then 1 Kelvin above the setpoint temperature for the supply water temperature of the radiator loop. The boiler and pump are switched off when the temperature at the bottom of the tank reaches 55 degree Celsius. The state transition of the finite state machine is such that first the pump of the boiler is switched on. Ten seconds later, the boiler will be switched on. When the tank reaches its temperature, the boiler is switched off, and ten seconds later, the pump will be switched off.

The building has a controlled fresh air supply. A heat recovery ventilator is used to preheat the outside air. Each room has a model for the leakage of the facade. If supply and exhaust air are unbalanced, then the difference in air supply will flow through this leakage model.

The hydronic heating system is connected to an expansion vessel. Some medium models for water compute the density as a function of temperature, while others assume a constant density. If the density is modeled as a function of temperature, then the water volume will increase when heated, and the expansion vessel will accumulate the added volume. As the water cools, this volume will flow from the expansion vessel into the hydronic heating system. If the medium model assumes the density to be constant, then the expansion vessel provides a reference pressure for the hydronic heating system.

The cooling of the two rooms is controlled using the temperature of roo1. The set point for mechanical cooling is 25 degree Celsius, with a proportional band of 1 Kelvin.

If the room air temperature is above 22 degree Celsius, the free cooling is enabled by opening the bypass damper of the heat recovery. Free cooling is only allowed if the outside air temperature is above 16 degree Celsius and 1 Kelvin below the room air temperature.

The cooling control is implemented in the model Buildings.Examples.HydronicHeating.TwoRoomsWithStorage.CoolingControl.


Name Description
MediumA Medium model for air
MediumW Medium model
CoolingControl Controller for the free cooling and the mechanical cooling


Generated at 2021-02-24T01:59:16Z by OpenModelicaOpenModelica 1.18.0~dev-65-g9ac6586 using GenerateDoc.mos