functionexponentialDamper
Damper opening characteristics for an exponential damper
Extends from Modelica.Icons.Function.
Information
This function computes the opening characteristics of an exponential damper.
The function is used by the model BuildingSystems.Fluid.Actuators.Dampers.Exponential.
For yL < y < yU, the damper characteristics is
kd(y) = exp(a+b (1-y)).
Outside this range, the damper characteristic is defined by a quadratic polynomial.
Note that this implementation returns sqrt(kd(y)) instead of kd(y). This is done for numerical reason since otherwise kd(y) may be an iteration variable, which may cause a lot of warnings and slower convergence if the solver attempts kd(y) < 0 during the iterative solution procedure.
Inputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | y | Control signal, y=0 is closed, y=1 is open | |
| Real | a | Coefficient a for damper characteristics | |
| Real | b | Coefficient b for damper characteristics | |
| Real | cL | Polynomial coefficients for curve fit for y < yl | |
| Real | cU | Polynomial coefficients for curve fit for y > yu | |
| Real | yL | Lower value for damper curve | |
| Real | yU | Upper value for damper curve |
Outputs
| Type | Name | Default | Description |
|---|---|---|---|
| Real | kThetaSqRt | Square root of loss coefficient, sqrt(pressure drop/dynamic pressure) |
Revisions
-
April 14, 2014 by Michael Wetter:
Improved documentation. -
July 1, 2011 by Michael Wetter:
Added constraint to control input to avoid using a number outside0and1in case that the control input has a numerical integration error. -
April 4, 2010 by Michael Wetter:
Reformulated implementation. The new implementation computessqrt(kTheta). This avoid havingkThetain the iteration variables, which caused warnings when the solver attemptedkTheta < 0. -
June 22, 2008 by Michael Wetter:
First implementation.