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Chap 10. Temperature

Chap 10. Temperature. Temperature and Heat Units Thermal Properties of Water Movement of Heat Energy Biological Influence of Temperature Dew Point and Frost Thermal Belt and Temperature Inversion Temperature Control for Crop Protection Controlled Environment Agriculture (CEA).

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Chap 10. Temperature

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  1. Chap 10. Temperature Temperature and Heat Units Thermal Properties of Water Movement of Heat Energy Biological Influence of Temperature Dew Point and Frost Thermal Belt and Temperature Inversion Temperature Control for Crop Protection Controlled Environment Agriculture (CEA)

  2. Heat of Vaporization • Heat is absorbed from surrounding when water evaporates • Heat of vaporization = 970 BTU per lb of water evaporated • Greenhouse cooling by the pad-and-fan evaporative system

  3. Pad-and-fan evaporative cooling system • Evaporative pad on one side wall and fans mounted on the other side wall • Flow of cooled air from pad area to fan area (one air exchange/min) • Maximum distance from pad to fan = 200 feet • Temperature differential (∆T) between pad and fan areas is usually 7 oF • Greenhouse air can be cooled down to the wet-bulb temperature Cool-cell pad Exhaust fans mounted on the side wall

  4. Psychrometric Chart • Illustrates the thermal properties of air • Dry-bulb temperature • Air temperature of sensible heat • measured by dry-bulb thermometer • Wet-bulb temperature • Temperature of an aspirated thermometer • measured with the bulb encased in a water • saturated wick Measure the room temperature Dry-bulb temp: ________oF Wet-bulb temp: ________oF

  5. Greenhouse Cooling with High-Pressure Fogging System • Use high-pressure (1000 psi) to generate fog (size 25-40 µ diam) • Use stainless steel pipe to prevent corrosion problem • Use low-salinity de-ionized water to prevent clogging of nozzles • More efficient in cooling the ambient air where it is needed • Less disease and algae problem, compared to misting system • Cost of installation high Summer cooling of greenhouse with fogging system High-pressure fogging

  6. Heat of Fusion • Heat is released to surrounding when water freezes • Heat of fusion is used to protect citrus fruits from freezing

  7. Heat of fusion from ice formation protects citrus crops exposed to freezing temperature in Florida

  8. Overhead water sprinkling on citrus crops in Florida to save them from freezing

  9. Transfer of Heat Energy

  10. Temperature Influence in Biological System

  11. Cell Damage by Low Temperature • Ice crystals rupture cell walls • Intracellular or intercellular event • Leakage of cell contents • Readily occurs in tender plants • Influence of “extensin” on cell wall Ice crystals Cell wall ruptures Extensin (rupture-resistant)

  12. Cryogenic Storage • Liquid nitrogen (-196 oC, -320 oF) • Permanent storage of pollen, seed, meristems

  13. Thermal Belt • Good site for locating an orchard • Usually on a sloped hill side • North-facing slope is better the south-facing slope cold warm warm cold warm slope warm slope Normal Condition Temperature Inversion

  14. Peach orchard located on a thermal belt, Western Slope, Colorado

  15. Fruit growing area in Oregon

  16. Grape orchards (vinyards) in Napa Valley, California Frost damage in vinyards is not as severe in other orchards because flowering of grapes occurs after shoot emergence

  17. Prevention of frost damage by movement Windmills and helicopters are used to mix the air to prevent frost damage on fruit crops during temperature inversion

  18. Use of Plastic Mulch

  19. Strawberry Production in California

  20. Frost Damage on Strawberry Plants in California A B Normal Damaged B. Crop failure often results from freezing of flower parts that are delicate and fragile. Stigmas and anthers are easily damaged by light freeze and become incapable of pollination and fertilization. A. Freezing of leaves is often initiated by the presence of ice nucleating active (INA) bacteria that secrete proteins that act as primers for ice crystal formation

  21. Ice Nucleating Active (INA) Bacteria on Strawberries • INA bacteria secrete protein on the leaf • Protein serves as a primer for ice crystal formation • Mutant INA bacteria secrete defective proteins (ice-) • Mutant proteins are incapable of forming Ice crystals Wild type INA bacteria Mutant type INA bacteria defective protein Ice crystals formed on the leaf → frost damage No ice crystals formed on the leaf → no frost damage

  22. Smudging in a fruit orchard to prevent frost injury

  23. Plant Growing Structures Controlled Environment Agriculture (CEA) Cold Frames Hotbeds Cloches and Plastic Tunnels Greenhouses Shade and Lath Houses

  24. Cold Frame

  25. Cloches or Hotbeds

  26. Use of Hotcaps for Vegetable Production

  27. Standard Peak Greenhouses

  28. Gutter-connected Standard Peak Greenhouses

  29. Construction of a Modern Greenhouse

  30. Quonset House

  31. Air Inflated plastic greenhouses

  32. Air Inflated Greenhouse with no internal support structure

  33. Geodesic Dome Greenhouse

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