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3. Cooling

3. Cooling. a. Introduction 1) Definition reduce temperature of air entering greenhouse Why? Reduce stress Uniformity Better growth. 2) Types of systems a) refrigeration system b) evaporative cooling pad and fan high pressure mist - fog b. Evaporative/cooling.

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3. Cooling

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  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)

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

  5. 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

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

  7. 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

  8. Important points in operation • Eliminate leaks • through pads • around pads • other areas • Uniform wetting • holes clogged • Detergent • Algae • CuSO4 d. Unit coolers

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

  10. Fog evaporative cooling

  11. Compare pad and fan to fog cooling

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