TXV-TEV from notes

  1. How much liquid and vapor passes through the TXV.
    • 75%liquid
    • 25% vapor
  2. what percentage of the compressor is low side, high side.
    • 90% low side
    • 10% high side
  3. 3 most popular types of metering devices
    • thermal expansion valve
    • automatic expansion valve
    • capillary type or bore tube
  4. Low side float is considered a txv, where is this located
    chiller barrel in an absorption system
  5. high side float is considered a txv, where is this located
    it is used in a hybrid chiller
  6. What is the job of the TXV
    • It meters the refrigerant to the evaporator
    • provides a pressure drop from the high side to the low side
    • lowers the boiling point
  7. The refrigerant temp has to be lower than what
    Than the load or product
  8. If the temp drops what else drops
  9. if the pressure rises what else rises
  10. Evaporator superheat is all about?
    • coil efficiency.
    • This is taken 6" from evaporator outlet.
    • this is what evaporator company's are looking for
  11. Where is evaporator superheat taken.
    6" from the evaporator outlet, also known as the suction line.
  12. Total superheat of the sytem is taken where.
    • 6" from the compressor inlet. 
    • this is what compressor company's are looking for.
  13. What is good superheat for?
    AC & High temp
    Medium temp
    Low temp
    Ice machine
    * unless otherwise spec by manufacturer
    • 15*F
    • 10*F
    • 5*F
    • 3*F
  14. What 3 pressures control the TXV.
    • Sensing bulb press = opening force
    • Evap press= closing force
    • Spring press=closing force
  15. What three components make up the power head.
    • Sensing bulb
    • transmission line
    • diaphragm
  16. Boiling off the refrigerant to soon = what.
    • Starved evaporator
    • high superheat
    • closed TXV
  17. not enough refrigerant is being boiled off = what
    • flooded evaporator
    • low superheat
    • opened TXV
  18. opening the txv will do what
    • Flood the evaporator 
    • lowering the superheat
    • lowering the subcooling
  19. closing the txv will do what
    • starve the evaporator  
    • raising superheat
    • raising subcooling
  20. 2 port txv is what kind
  21. 3 port txv is what kind
    • external.
    • are used on multiple circuits
  22. external txv compensate for pressure drop, where
    in the distributor
  23. internal txv are used where
    on a single circuit evaporator with less than 2 1/2 # across the evaporator
  24. external txv are used where
    on multiple circuit evaporator with more than 2 1/2 # across the evaporator
  25. TXV components
    • valve body
    • diaphragm
    • needle and seat
    • spring
    • adjustment and packing gland
    • sensing bulb and transmission line
  26. SAE stands for
    • Standard American Equipment.
    • Which is flared
  27. ODF stands for
    • outside diameter fitting.
    • which uses fittings or bolts
  28. The diaphram does what.
    • moves the needle in and out of the seat in response to the system requirements.
    • Flexes downward to open the valve
    • flexes upward to close the valve
  29. needle and seat does what?
    • controls the refrigerant flow through the valve.
    • needle is pushed in, the refrigerant flow will be reduced to the evaporator
  30. when the needle is closed?
    • the refrigerant flow will decrease.
    • the superheat will raise
  31. when needle is open
    • The refrigerant flow will increase.
    • The superheat will lower
  32. Turn the txv  closed or clockwise will
    • Restrict the refrigerant flow
    • increase the superheat
    • increase the subcooling
  33. Turn the txv open or counter-clock wise will
    • increase the refrigerant flow
    • decreasing the superheat
    • decreasing the subcooling
  34. low side pressure converted to a temperature
    boiling point
  35. high side pressure converted to a temp
    condensing temp
  36. how do you get internal compressor oil temp
    discharge line temp + 70*F
  37. high side pressure converted to a temp - 30*F
    ambient air
  38. high side pressure converted -
    liquid line temp = what
  39. low side pressure converted -
    suction line temp = waht
Card Set
TXV-TEV from notes
describe types of txv, operation,characteristic