Modeling thermostat cycle operation in Airpak
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How we can simulate following problem in Airpak: Whenever the room temperature went above a certain value, Airpak turned off the heating air supply in the room. Likewise, if reached below a certain temperature, Airpak turned back on the heat. This way, one could see how long it took the room to heat up when air was on, or cool down when air was off. Here are a few guidelines that you might find useful. * Lets consider a Heating scenario. In reality the temperature control is accomplished by means of a thermostat. The heating system is ON. It shall turn OFF when the room temperature (thermostat temperature) reaches, let say, 30 C. Now the room loses energy (cooling) to the surroundings. The room shall keep losing energy until the room temperature (thermostat temperature) goes down to, lets say, 25 C. At this point, the heating system starts up again and the HEAT - COOL - HEAT cycle thus contiues. * The location of the thermostat can be defined as a point in Airpak. * Although this would be a transient solution, I would recommend the use of a steady state flow solution as a starting point for the transient. * While setting up the FIRST transient case (lets say, Heating), the key would be to specify the "Upper Limit" for Temperature (can be Pressure, Velocity and Species too) at the thermostat location (x, y, z) on the Solution/Monitor/ panel under "Solution Termination Criteria". * With this setting, the transient solution will automatically terminate when the temperature at the thermostat location crosses the "Upper Limit". * Next, the Cooling scenario needs to be set up. In this case, firstly modify the geometry (deactivate the fans/openings which are a part of the heating system) to represent the cooling scenario. Remesh the geometry (required due to deactivation of objects). Then under Solution/Monitor set a "Lower Limit" for temperature. Solve using "Interpolated Data Restart" option. Use the heating case solution id as the restart solution id. * With this setting, the transient solution will automatically terminate when the temperature at the thermostat location crosses the "Lower Limit". * I would repeat these cycles till the "Heating and Cooling Cycle Times" predicted by Airpak are not changing with successive cycles. |
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