TXV-TEV from notes
Card Set Information
TXV-TEV from notes
txv expansion devices
describe types of txv, operation,characteristic
How much liquid and vapor passes through the TXV.
what percentage of the compressor is low side, high side.
90% low side
10% high side
3 most popular types of metering devices
thermal expansion valve
automatic expansion valve
capillary type or bore tube
Low side float is considered a txv, where is this located
chiller barrel in an absorption system
high side float is considered a txv, where is this located
it is used in a hybrid chiller
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
The refrigerant temp has to be lower than what
Than the load or product
If the temp drops what else drops
if the pressure rises what else rises
Evaporator superheat is all about?
This is taken 6" from evaporator outlet.
this is what evaporator company's are looking for
Where is evaporator superheat taken.
6" from the evaporator outlet, also known as the suction line.
Total superheat of the sytem is taken where.
6" from the compressor inlet.
this is what compressor company's are looking for.
What is good superheat for?
AC & High temp
* unless otherwise spec by manufacturer
What 3 pressures control the TXV.
Sensing bulb press = opening force
Evap press= closing force
Spring press=closing force
What three components make up the power head.
Boiling off the refrigerant to soon = what.
not enough refrigerant is being boiled off = what
opening the txv will do what
Flood the evaporator
lowering the superheat
lowering the subcooling
closing the txv will do what
starve the evaporator
2 port txv is what kind
3 port txv is what kind
are used on multiple circuits
external txv compensate for pressure drop, where
in the distributor
internal txv are used where
on a single circuit evaporator with less than 2 1/2 # across the evaporator
external txv are used where
on multiple circuit evaporator with more than 2 1/2 # across the evaporator
needle and seat
adjustment and packing gland
sensing bulb and transmission line
SAE stands for
Standard American Equipment.
Which is flared
ODF stands for
outside diameter fitting.
which uses fittings or bolts
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
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
when the needle is closed?
the refrigerant flow will decrease.
the superheat will raise
when needle is open
The refrigerant flow will increase.
The superheat will lower
Turn the txv closed or clockwise will
Restrict the refrigerant flow
increase the superheat
increase the subcooling
Turn the txv open or counter-clock wise will
increase the refrigerant flow
decreasing the superheat
decreasing the subcooling
low side pressure converted to a temperature
high side pressure converted to a temp
how do you get internal compressor oil temp
discharge line temp + 70*F
high side pressure converted to a temp - 30*F
high side pressure converted -
liquid line temp = what
low side pressure converted -
suction line temp = waht