Pumping Units; Pumping Unit With Flow Control Configuration; Pumping Unit With Constant Pressure Control - Carel humiFog multizone User Manual

4.1 Pumping unit with flow control
configuration
humiFog controls the humidification and/or cooling capacity by
continuously controlling the atomised water flow-rate across a wide
range of modulation.
This configuration is used in the following applications:
•
humidification and/or adiabatic cooling (direct) in an AHU;
•
humidification and indirect adiabatic cooling in an AHU with heat
recovery unit (one atomisation system at a time atomises the water). In
this case, a zone electrical panel will be required, see the next chapters
for further information.
humiFog is fitted with an inverter to continuously and precisely control
the speed of the pump and, consequently, the flow-rate.
The outlet pressure is kept within the optimum water atomisation limits
by the range of modulation of the pump speed and control of the
number of nozzles that atomise the water.
In detail, the nozzles must be supplied at a pressure in the range from
25 to 70 bars, to ensure that the droplets generated have an average
equivalent diameter of 10-15 μm.
Based on the flow-rate of water to be atomised, humiFog will activate the
number of nozzles that ensures the pressure is within the range indicated
above.
It is clear that if the required flow-rate is low, just a few nozzles will be
needed to atomise the water; if the request increases, the increase in
flow-rate will cause an increase in pressure that, if it exceeds 70 bars, will
activate other atomising nozzles, consequently decreasing the pressure
and returning it within the range of optimum values. Similarly, if the
humidification request decreases, the flow-rate and thus the pressure will
decrease and, if the latter falls below 25 bars, some nozzles will be closed
so that the pressure returns within the optimum atomisation range.
This is possible because the nozzles are assembled into groups of up to
four, with different capacities; when suitably activated, these guarantee
continuous modulation of the flow-rate across a wide range, nominally
from 14 to 100% of the maximum flow-rate, with a pressure from 25 to
70 bars.
The groups of nozzles are normally configured when selecting the
humiFog system, and the procedure is clearly described in the documents
supplied with the water distribution system (rack).
The pumping unit in the flow control configuration can only be used for
single-zone applications: one pumping unit supplies just one zone at a
time. Multizone configurations are not possible.
The flow control configuration guarantees maximum humidification and
adiabatic cooling precision as capacity is controlled continuously and
across a wide range.
4.

PUMPING UNITS

4.2 Pumping unit with constant pressure
The humiFog controller manages the water pressure generated to ensure
it remains at a constant level, typically 70 bars.
This configuration is used in the following applications:
•
humidification and/or adiabatic cooling (direct) in an AHU (the flow
control configuration is recommended);
•
humidification and indirect adiabatic cooling in an AHU fitted with
heat recovery unit (the two distribution systems can atomise water at
the same time);
•
humidification and/or adiabatic cooling (direct) in an industrial
environment;
•
humidification and/or adiabatic cooling (direct) in multiple zones,
whether AHUs, AHUs fitted with heat recovery units, industrial
environments, or any combination of these.
Note that in the case of humidification and/or cooling adiabatic directly
into rooms, constant pressure control is preferred over flow control: as
the droplets are atomised directly into the environment, to minimise the
space required for evaporation, the smallest possible diameter should
be achieved and therefore the water must be atomised at maximum
pressure. This is represented by constant pressure control, which
maintains the pressure at 70 bars.
humiFog is fitted with an inverter to control the speed of the pump and
maintain the pressure at the rated value set by parameter, typically 70
bars.
The humiFog system will be made up of a pumping unit (master) that
also controls its own zone, as well as a series of zone electrical panels
(slaves) corresponding to the number of remaining zones.
Note that for humidification and indirect adiabatic cooling in an AHU
fitted with heat recovery unit (the two distribution systems may atomise
the water at the same time) a zone panel (slave) will be required.
The water distribution system/systems have nozzles organised into
groups, called steps, which in general each have different capacities.
Based on the flow-rate of water to be atomised in one or more zones, the
humiFog system will activate the required steps until the nozzles atomise
the required quantity of water. Each zone can have up to 6 modulation
steps.
The groups of nozzles are normally configured when selecting the
humiFog system, and the procedure is clearly described in the documents
supplied with the water distribution system (rack or room distribution
and atomisation system)
Constant pressure control rationalises operation of the humiFog pumping
unit as, despite the lower precision, it can treat a number of zones at the
same time without installing a pumping unit for each AHU or industrial
environment.
21
control
"humiFog multizone - pumping unit"
ENG
+0300066EN - rel. 1.2 - 10.12.2015