[ heat transfer ]
process . This results in a minimum achievable process temperature of 29 ° C .
Fogging system
The highest ambient temperatures normally occur only over a relatively short period of time each year ( except for tropical regions ). Nevertheless , this design point determines the overall size of the AFC . And this results in an installation that is oversized for most of the time . A clever solution to this problem is the use of a fogging system . Hundreds of small nozzles are installed below the AFC tube bundle . Very pure water ( demineralised-water quality or at least soft water with inlet pressure between 3 and 5 bars ) is atomized and sprayed into the air stream , evaporating before it enters the tube bundle . While the water evaporates , it cools down the air before entering the tube bundle . This principle is also called adiabatic cooling .
By using a fogging system , the inlet air temperature can be reduced by as much as 10 ° C ! Such a reduction in design ambient air temperature has a dramatic impact on the size of the AFC . Because ultra-pure water is used and evaporated before entering the bundle , there are no issues with corrosion or fouling . Kelvion Thermal Solution provides these systems , including the pump skid and process control to ensure proper humidification . As part of the detailed thermal design , data is provided about the water usage as a function of the ambient temperature . Of course , when the temperature gets below the design ambient air temperature , no water is used at all .
So , when could the use of a fogging system be beneficial ? Fogging is efficient for ambient temperatures above 25 ° C and humidity below 70 %. It is meant to be used during the hot season , at the hottest hours of the day when humidity is low .
Adiabatic pads
Ambient air passing through the wetted adiabatic pad increases in relative humidity , cooling the entering air ’ s dry-bulb temperature towards the entering air ’ s wet-bulb temperature . The lower dry-bulb temperature exiting the adiabatic pad is referred to as the depressed dry bulb .
Spray nozzles under the tube bundle
16 Hydrogen Tech World | Issue 6 | October 2022