This model represents a cooling tower with variable speed fans.
If `closedCircuit`

is false, the model represents a
cooling tower filled with metallic packing, where the incoming
water is cooled by direct contact with humid air, by means of
evaporation. Dynamic models with `Mp > 0`

also
represent heat storage in the packing and heat transfer between the
packing and the evaporating water.

If `closedCircuit`

is true and `Mp = 0`

,
then the model represents a closed-circuit tower cooling an
external circuit, which is thermally connected through the 1D
distributed heat port `wallPort`

, representing the tube
external surface.

The heat transfer between the packing or the tube surface and
the evaporating water is computed by a specific heat transfer
coefficient, whose nominal value is `gamma_wp_nom`

, and
which varies with the `nu_l`

-th power of the liquid
flow.

The mass and heat transfer from the hot water to humid ambient air is modelled according to Merkel's equation: the driving force for heat and mass transfer is the difference between the specific enthalpy of saturated humid air at the water temperature per unit dry air mass, and the specific enthalpy of saturated humid air at the wet bulb temperature Twb per unit dry air mass. The dry and wet bulb temperatures of incoming air are given by the settings of the system object.

The 1D counter-current heat and mass transfer equations are
discretized by the finite volume method, with `N-1`

volumes; average quantities between volume inlet and volume outlet
are used to compute the driving force of the mass and energy
transfer.

Humid air is modelled as an ideal mixture of dry air and steam, using the IF97 water-steam model.

The hold-up of water in the packaging is modelled assuming a
simple linear relationship between the hold-up in each volume and
the corresponding outgoing flow, which is calibrated by the
`Mnom`

and `M0`

parameters. The energy
storage in the water hold-up and in the packaging is accounted
for.

The behaviour of the fan is modelled by kinematic similarity; the air flow is proportional to the fan rpm, while the consumption is proportional to the cube of the fan rpm.

Is it possible to neglect all dynamic behaviour and get a static
model by setting `staticModel=true`

.

Name | Description |
---|---|

Water | |

DryAir |

*28 Jul 2017*Francesco Casella:

First release.

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