.IBPSA.Fluid.Actuators.Dampers.Exponential .IBPSA.Fluid.Actuators.Dampers.ExponentialThis 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 |
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.
kDam_default and
kThetaSqRt_default from initial algorithm
to the variable declaration, to avoid a division by zero in
OpenModelica.