1. 3. Cooling a. Introduction 1) Definition reduce temperature of air entering greenhouse Why? –Reduce stress –Uniformity –Better growth

2. 2) Types of systems a) refrigeration system b) evaporative cooling pad and fan high pressure mist - fog b. Evaporative/cooling

3. Evaporative cooling 1) Principal –Energy Required –H2O (liquid) + Warm air (energy) > H2O (gas) + cooler air –1000 BTU to change 1 lb liquid H2O to gas (water vapor)

5. 2) Factors determining cooling –Temperature: outside air –Relative humidity: outside air –Temperature: inside air –air movement –shading –structure –Covering Evaporative Cooling

6. c. Pad and fan system –80% to 90% of difference between wet and dry bulb –Temp increases from inlet to outlet –higher moisture (outside) reduces temp decrease

7. 80% to 90% of difference between wet and dry bulb Cooling efficiency

8. 1) design of system pad and fan system –Equipment Separate house Ridge and furrow –Fan and pad size fans, same as for ventilation –pads, based on fan size and material

9. 2)Important points in operation –Eliminate leaks through pads around pads other areas –Uniform wetting holes clogged Detergent –Algae CuSO4 d. Unit coolers

10. e. High pressure mist - fog –Small droplets Nozzles –150-200 psi up to 500 psi –special pump –Problems salt deposits poor air movement

11. Fog evaporative cooling

12. Compare pad and fan to fog cooling