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1.3 Main and sub unit's EEV control
(1) Main EEV control
Main EEV operates with fuzzy control rules to keep the degree of super Heat(Superheat) (about 3°C)at
the evaporator outlet stable during heating mode
The degree of Superheat = Tsuction - Tevaporation
Tsuction : temperature at suction pipe sensor(°C)
Tevaporation : evaporation temperature equivalent to low pressure(°C)
(2) Sub EEV control
Sub EEV operates according to the opening of main EEV, otherwise the opening range is limited by the
open degree of the main EEV
- Limited conditions : liquid back control, discharge temperature control etc.
(3) Subcooling EEV control(about 15°C)
Subcooling EEV works with fuzzy rules to keep the degree of Subcool at the outlet of subcooler during
cooling mode
The degree of Subcool = Tcondensation - Tliquid
Tliquid : temperature at outlet of subcooler(°C)
Tcondensation : condensation temperature equivalent to high pressure(°C)
(4) Avoiding excessive high discharge temperature : when main EEV opens some given opening (R22 :
1000pls, R410A : 800 pls) and discharge temperature is above 85°C in heating operation, subcooling
EEV may control the "subcooling out temperature-evaporating temperature" to be some given difference.
Function
INV C1 C2 C3
SUB1Main
(2) (2) The sequence of compressor operation for 2 unit system
1) Stage increasing situation
Inv → C2→ C1→ C3(full)
Inv → C3→ C1→ C2(full)
Full → C2→ C1→ C3
Full → C3→ C1→ C2
2) Stage decreasing situation
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