December 14th, 2017 | Posted in Air Cleaners
When sizing a kitchen exhaust pollution control unit, we typically recommend about 2,000 CFM per full size industrial electrostatic cell. Then to achieve higher airflows, we will add more cells in various configurations to maintain 2,000 CFM or less per cell. If you look at the single cell efficiencies graph below, you can see efficiencies graphed for several airflows. If a higher efficiency is required, we will recommend a lower CFM per electrostatic cell to achieve that efficiency.
There are applications where there is no room to keep adding cells next to each other to achieve the required efficiency. In these applications, we recommend using two electrostatic cells in tandem that we call a double pass configuration to increase the efficiency. The graph below for double pass cell efficiencies shows that you can run a set of electrostatic cells in double pass configuration to push the airflow up about 37% to 2,750 CFM. Another reason that we would recommend a double pass configuration is if the area where the PCU is going to be installed is near a neighborhood that is very sensitive to the emissions of the kitchen exhaust. Ultimately with double pass configuration, we can boost efficiency, add backup particulate collection, and increase particle holding capacity in the system with only slightly increasing airflow resistance.
Since the airflow resistance of a single cell is very low compared to alternative media filters, adding a second electrostatic cell in a double pass configuration still maintains a very low pressure drop. Also, the benefit of the electrostatic cells is the airflow resistance doesn’t increase much at all as the electrostatic cells load. The last two graphs show airflow resistance through a single and double pass cell at various airflows and comparing the airflow resistance of an electrostatic to a comparable media filter.
Read more about electrostatic precipitators check out our earlier blog Comparing Commercial Kitchen Exhaust Systems.
Note: Data above is compared to a double stack of industrial size cells compared to a 24” x 24” x 21” 10 pocket MERV 15 filter.