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Guidelines for Climate Control of Temperature and Humidity in Greenhouses

  • Climate control in a greenhouse is based on the principle of the exchange of energy between the air and the fog moisture supplied by the NaanDanJain Fogger.

  • One calorie is the amount of heat necessary to raise the temperature of 1 cm3 of water by 1C.

  • The conversion of water from liquid to vapor absorbs heat from the surrounding air, at a rate of 590 calories/1 gram of evaporated water (1 cm3). This process lowers the air temperature.

  • Efficient installation and operation can reduce the temperature in the greenhouse by 4 to 6C, depending on the environmental conditions.

  • Efficiency of the cooling system depends on two environmental factors:
    - External temperature
    - External humidity

Essential conditions for efficient cooling with the NaanDanJain Fogger are

  • An efficient ventilation system which continuously introduces external dry air into the greenhouse to replace the humid air.

  • Pulse operation of the fogging system, to minimize the amount of water that may settle on the foliage.

What is the importance of the droplet size created by the NaanDanJain Fogger?

  • With a 7 l/h nozzle at 4 kg/cm, the average fog droplet is 90 microns. These droplets evaporate without wetting the leaves or greenhouse floor.

Spacing Design

Type Fogger Configuration Nozzle Flow Rate Spacing Precipitation Rate
Between Laterals On the line
Fogger T 7.0 x 2 14 3.0 1.5 3.1
Cross 7.0 x 4 28 3.0 3.0 3.1
Super Fogger T 6.5 x 2 13 3.0 1.5 2.9
  • The foggers should be installed in as high as possible, with minimal height being 3.0 m. The nozzles should be situated perpendicularly to the main line.

  • Operating pressure: 4.0 kg/cm² at the fogger.


How much water is needed to cool a greenhouse?

  • In our experience, a fog precipitation of 3 to 3.5 mm/h is suitable in the majority of cases (3 mm/h = 30 m3/h per ha.)

Water Consumption

(meter cube per hectare per 10 hour/day)

Nozzle l/hr Model configuration Net precipitation,
(l/hr/m² for various spacing & pulses)
3.0 x 1.5 m 3.0 x 3.0
Fogger
    1:5* 1:10 1:15 1:5 1:10 1:15
Blue 7.0 x 2 T 0.62 0.31 0.21      
Blue 7.0 x 4 cross       0.62 0.31 0.21
Water consumption m³/ha/day (10 hour)   62 31 21 62 31 21
Super Fogger
6.5 x 2 T 0.58 0.29 0.19 * On: Off pulse ratio
Example: ratio 1:5
The system will operate only fifth of the time so the actual precipitation will be only 20%, or 10% for ratio 1:10
Water consumption m³/ha/day (10 hour)   58 29 19

Cooling

  • The pulse duration should be as short as possible, between 1 to 3 sec. (Under certain conditions, longer durations can be considered).

  • The interval between fogging pulses should be based on the factors of humidity, temperature levels, greenhouse ventilation and height of the foggers.

Initial guide (pulse of 2.0 sec)

  • Fine tuning is recommended to be done according to local conditions.

Outside relative
humidity (%)
Interval (Sec.) Replenish moisture (l/ha)
30 15 4100
40 25 2500
50 25 2500
60 30 2100


Cooling and Humidifying cannot be conducted simultaneously.

Humidification

  • In the event that the humidity level needs to be increased then the ventilation system must be shut down. The duration of the fogging process should be as short as possible (1.0 second).

  • The intervals between fogging pulses will vary according to the minimal relative humidity required.

  • During the morning, when temperatures rise and humidity decreases, the humidity sensor will cause the fogging system to operate.

Humidity Interval Duration
30 - 40% 60 sec 1 sec
40 - 50% 90 sec 1 sec
50 - 60% 120 sec 1 sec

Spraying

  • In the event that the humidity level needs to be increased then the ventilation system must be shut down. The duration of the fogging process should be as short as possible (1.0 second).

Water Quality

  • In order to avoid clogging by carbonates or the accumulation of salt deposits on the leaves, it is recommended to avoid irrigation with hard or saline water. Rainwater, soft water or osmosis-treated water is the most suitable.

Optional Nozzles

Colour blue orange red black
Flow rate l/h at 4.0 bar 7.0 14.0 21.0 28.0
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