modelExponential
Extends from IBPSA.Fluid.Actuators.BaseClasses.PartialDamperExponential.
Information
This model is an air damper with flow coefficient that is an exponential function
of the opening angle. The model is as in ASHRAE 825-RP.
A control signal of y=0 means the damper is closed, and y=1 means the damper
is open. This is opposite of the implementation of ASHRAE 825-RP, but used here
for consistency within this library.
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 that
matches the damper resistance at y=0 and y=yL or y=yU and
y=1, respectively. In addition, the polynomials are such that
kd(y) is
differentiable in y and the derivative is continuous.
The damper characteristics kd(y) is then used to compute the flow coefficient k(y) as
k(y) = (2 ρ ⁄ kd(y))1/2 A,
where A is the face area, which is computed using the nominal
mass flow rate m_flow_nominal, the nominal velocity
v_nominal and the density of the medium. The flow coefficient k(y)
is used to compute the mass flow rate versus pressure
drop relation as
m = sign(Δp) k(y) √ Δp
with regularization near the origin.
ASHRAE 825-RP lists the following parameter values as typical:
| opposed blades | single blades | |
|---|---|---|
| yL | 15/90 | 15/90 |
| yU | 55/90 | 65/90 |
| k0 | 1E6 | 1E6 |
| k1 | 0.2 to 0.5 | 0.2 to 0.5 |
| a | -1.51 | -1.51 |
| b | 0.105*90 | 0.0842*90 |
References
P. Haves, L. K. Norford, M. DeSimone and L. Mei, A Standard Simulation Testbed for the Evaluation of Control Algorithms & Strategies, ASHRAE Final Report 825-RP, Atlanta, GA.
Revisions
-
March 22, 2017, by Michael Wetter:
Updated documentation. -
April 14, 2014 by Michael Wetter:
Improved documentation. -
September 26, 2013 by Michael Wetter:
Moved assignment ofkDam_defaultandkThetaSqRt_defaultfrominitial algorithmto the variable declaration, to avoid a division by zero in OpenModelica. -
December 14, 2012 by Michael Wetter:
Renamed protected parameters for consistency with the naming conventions. -
June 22, 2008 by Michael Wetter:
Extended range of control signal from 0 to 1 by implementing the function IBPSA.Fluid.Actuators.BaseClasses.exponentialDamper. -
June 10, 2008 by Michael Wetter:
Introduced new partial base class, PartialDamperExponential. -
June 30, 2007 by Michael Wetter:
Introduced new partial base class, PartialActuator. -
July 27, 2007 by Michael Wetter:
Introduced partial base class. -
July 20, 2007 by Michael Wetter:
First implementation.