HIGH PRESSURE FOG COOLING - SYSTEM SIZING

But for those that wish to get an idea of how much fog generation is required, here is a very "general rule of thumb table." The first table is for naturally ventilated greenhouses houses and second table is for mechanically ventilated greenhouses.

NATURALLY VENTILATED GREENHOUSES:

If outdoor design temperature range is 75 to 85 deg. F. use 0.00016 USGPM/sq. ft.
If outdoor design temperature range is 85 to 95 deg. F use 0.0002 USGPM/sq. ft..
If outdoor design temperature range is 95 to 105 deg. F use 0.0003 USGPM/sq. ft.
If outdoor design temperature range is 105 to 115 deg. F use 0.0004 USGPM/sq. ft.

TABLE TWO - MECHANICALLY VENTILATED HOUSES:

If outdoor design temperature range is 75 to 85 deg. F. use 0.000018 USGPM/CFM
If outdoor design temperature range is 85 to 95 deg. F use 0.000025 USGPM/CFM.
If outdoor design temperature range is 95 to 105 deg. F use 0.000034 USGPM/CFM.
If outdoor design temperature range is 105 to 115 deg. F use 0.0000435 USGPM/CFM.

USGPM = united states gallon per min.
sq. ft.. = greenhouse area in sq. feet.
CFM = cubic feet of air flow of exhaust fans.

Rule of thumb Sizing.

A grower has a block of gutter connected greenhouse structures. There are 10 bays of 21' wide X 144 foot long houses. Each bay is provided with a 20,000 CFM exhaust fan. The outdoor air temperature seldom gets above 95 deg. F.

In table two for mechanically ventilated greenhouses the range for moisture addition is 0.000025 USGPM/CFM.

Therefore, the total fog system size would need be:

10 bays X 20,000 CFM X 0.000025 USGPM/CFM = 5 USGPM ( 18.92 liters/min ).
This provides the minimum pump capacity size.

And ..

to calculate the number of nozzles at 1000 PSI

5 gallons / 0.0225 = 222 nozzles (total )

Each nozzle is rated for 0.0225 GPM at 1000 PSI

And

if there is a desire to uniformly fog the house with one grid running down the length of each bay

=144 feet per each bay / (222 / 10 Bays ) = 6.48 feet on center nozzle spacing.

Use 6.5 foot nozzle spacing.

 

So there you have it. Basically you need a minimum pump capacity of 5 gallons and 10 fog grids each 144 feet long with nozzles spaced at 6.5 feet on center.

Now bear in mind this has been sized with the rule of thumb method ( ie: one air change per minute based on 8 foot height. ) For those with 12, 14 and 16 feet under the gutter heights .... well ..... you can certainly do a lot more fogging to reduce the temperatures and vapor deficit even more.

If you require further selection advise and information specific to your application please feel free to contact us.

  AGROPONIC INDUSTRIES LTD.
908 RANCHVIEW CRES. NW., CALGARY, ALBERTA, CANADA, T3G 1P9
ph (403)241-8234, fax (403)241-8234
Email: agropon@agroponic.com, ULR: agroponic.com

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