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IMPROVED MODELS FOR COLD UNITS

IMPROVED MODELS FOR COLD UNITS. L. De Wet. THE DYNAMIC MODEL. Adds timing of exposure to Ta in a cycle Based on experimental results Superior – negating effect of high day Ta Positive effect of moderate Ta in chilling cycle Disadvantage – requires complex computerisation.

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IMPROVED MODELS FOR COLD UNITS

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  1. IMPROVED MODELS FOR COLD UNITS L. De Wet

  2. THE DYNAMIC MODEL • Adds timing of exposure to Ta in a cycle • Based on experimental results • Superior – negating effect of high day Ta • Positive effect of moderate Ta in chilling cycle • Disadvantage – requires complex computerisation

  3. POSITIVE UTAH CHILL MODEL(PCU) • Not as good as Dynamic model, but better than Utah model • Carry-over effect of negating Ta –deleted • PCUs for any area in SA in Table 2 • Optimal Ta range = Tmn between 0 oC and 7 oC

  4. Table 2: PCU estimation table for any station in SA, determined by using sine curve for heating cycle, followed by log cooling cycle

  5. PCU • PCU useful especially when time is limited and when hourly data is not available • Good estimations for both cold and warmer areas • Can be used for areas of similar latitude • Table 2 can be modified for higher and lower latitudes (diff day lengths) • Estimation of daily chilling possible (using Table 2) – no waiting for hourly data

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