TXV-TEV from notes

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How much liquid and vapor passes through the TXV.
- 75%liquid
- 25% vapor
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

pressure
if the pressure rises what else rises

temperature
Evaporator superheat is all about?
- coil efficiency.
- 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
Medium temp
Low temp
Ice machine
* unless otherwise spec by manufacturer
- 15*F
- 10*F
- 5*F
- 3*F
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.
- Sensing bulb
- transmission line
- diaphragm
Boiling off the refrigerant to soon = what.
- Starved evaporator
- high superheat
- closed TXV
not enough refrigerant is being boiled off = what
- flooded evaporator
- low superheat
- opened TXV
opening the txv will do what
- Flood the evaporator
- lowering the superheat
- lowering the subcooling
closing the txv will do what
- starve the evaporator
- raising superheat
- raising subcooling
2 port txv is what kind

internal
3 port txv is what kind
- external.
- 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
TXV components
- valve body
- diaphragm
- needle and seat
- spring
- 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

boiling point
high side pressure converted to a temp

condensing temp
how do you get internal compressor oil temp

discharge line temp + 70*F
high side pressure converted to a temp - 30*F

ambient air
high side pressure converted -
liquid line temp = what

subcooling
low side pressure converted -
suction line temp = waht

superheat

Author

salvatorefricano

295014

Card Set

TXV-TEV from notes

Description

describe types of txv, operation,characteristic

Updated

2015-02-12T04:38:07Z

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