Valves and Metering Devices

Pregunta	Respuesta
what are the basics of a metering device?	Provides small opening, or orifice, through which only a small amount of refrigerant can flow at one time.
Name 6 types of metering devices?	1. Capillary tube 2. TXV 3. Automatic expansion valve (AXV) 4. Electronic expansion valve 5. low side float (LSF) 6. High Side Float (HSF)
Name the main two types of fixed metering devices.	1. Capillary tube 2. Fixed orifice
What appliance is commonly used with cap tubes?	Refrigerators and window AC units
What application uses fixed orifice?	Residential splits and heat pumps
Describe a cap tube?	a length of tubing with a small and precisely form inside diameter.
What defines the performance of a cap tube?	- tube length - Inside diameter - number of turns
Where is the cap tube usually attached?	Between the evap and the liquid line.
How is the cap tube usually positioned?	A portion of it is positioned so a portion of it is in contact with the suction line.
Why is the cap tube positioned that way?	This causes the cap tube to transfer some of it's heat to the suction line (super heat and subcooling created with transfer)
With a cap tube system, what happens to the high and low side once the compressor shuts off?	both pressures equalize
What is a static condenser?	Condensers that do not have a fan, rely on convection to cool it off.
common cause of cap tube failure?	- Bent - crimped - plugged
When replacing a cap tube it is good practice to replace what?	Filter Drier
What is a fixed orifice?	Small fitting with a small hole that fits between the inlet and outlet.
How does the Thermostatic expansion valves work?	Adjust refrigerant flow rate to compensate for varying loads.
How does a sensing bulb function?	It is filled with a volatile fluid, and pressure inside the bulb change with the temp of the evap outlet.
What is refrigerant vapor that forms in the evap due to a sudden drop in pressure between high and low side of the system called?	Flash Gas
Difference in temperature between the evap inlet and the sensing bulb is called?	Super Heat
Turning the TXV adjustor clockwise will do what?	increase spring tension.
Turning the TXV adjustor counter clockwise will do what?	decrease spring tension.
When a TXV is going too far in one direction and then over correcting and returning too far in the other direction is called what?	Hunting
The bottom of the TXV diaphgram is exposed to what?	The pressures at the evap inlet.
The top of the TXV diaphgram is exposed to what?	to the sensing bulb pressures
Which sensing bulb is uses the same refrigerant as the system?	Liquid Charged - Gas charged Sensing bulb
Which sensing bulb is uses the different refrigerant as the system?	Liquid cross charged sensing bulb and gas cross charged.
Which sensing bulb contains two substances?	Adsoprtion Gas cross charged sensing bulb.
What does the adsoption bulb contain?	- Non condensing gas (carbon dioxide) - Carbon, silica gel or charcoal.
What splits the flow of refrigerant into several paths to reduce pressure drops in the evap?	Distributors
Which metering device is controlled by low side pressure?	Automatic expansion valve
if an AXV is not equipped with ______ it will not equalize the high and low side during off cycle.	Bypass or Valve Bleeder.
Which metering device uses an electric operator instead of a diaphragm power assembly.	Electronic Expansion Valves.
What metering device uses a flooded system?	Low side float
Do Pressures balance on a LSF during off cycle?	No.
What metering device regulates refrigerant flow into the evap based on volume of a certain liquid receiver?	High Side Float.
Which Valve type is used to deliver discharge vapor into an externally equalized TXV during off cycle and suction vapor during on cycle?	Bypass valve.
How many inputs and output do bypasses have?	Bypass valve has one input valve and two output valves.
Which valve is frequently used in heat pumps?	Reversing valves
Which valve is commonly installed between the suction line and the compressor inlet to prevent compressor overloading?	Pressure Regulating valve
what prevents high pressure vapor and refrigerant oil from backing up into the evap during off cycles?	Check Valves

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	Creado por Maroun Nasr hace más de 10 años