Thermal Expansion Block Valve

 

Thermal Expansion Block Valve

 

 Thermal Expansion Block Valve

The block valve differs from the previously

mentioned expansion valve in that it has four

passages, although the basic operation is

exactly the same. Operation of the block

valve is still via refrigerant

expansion/contraction within a diaphragm

(11), but not sensed through separate tube

(capillary tube). It is sensed by changes in

the refrigerant temperature and pressure

passing from the evaporator outlet through

the block valve.

As the refrigerant from the outlet side of the

evaporator passes over the sensing element

(12), expansion or contraction of the

refrigerant takes place causing the activating

pin (8) to move the ball valve (6) away or

closer to the metering orifice. This allows

more or less refrigerant to enter the

evaporator coil inlet.

 

1. From Filter Drier

2. To Evaporator Inlet

3. From Evaporator

4. To Compressor

5. Metering Orifice

6. Ball

7. Spring

8. Activating Pin

9. Refrigerant

10. Pressure Compensation

under Diaphragm

11. Metallic Diaphragm

12. Sensing Element

 

 

 

Pressures in control

As shown in the illustration, the block valve

controls refrigerant flow by using a system of

opposing pressures which we will call:

F1 - Temperature sensing

This is a sealed diaphragm and sensor

containing refrigerant. As refrigerant leaving

the evaporator coil outlet passes over

sensing element (12) the refrigerant (9)

above the diaphragm (11) expands moving

pin (8) downwards pushing ball valve (6)

away from the metering orifice (5).

F2 - Pressure compensation

This is a passage (10) in the block valve

outlet side where refrigerant can build up

under the diaphragm (11) to act as an

opposing pressure to help regulate the

amount of refrigerant into the evaporator coil

inlet side.

F3 - Pressure spring

This spring (7) is located under the ball valve

(6) and acts as an opposing force trying to

move the ball valve towards the metering

orifice (12) and to reduce refrigerant flow to

the evaporator coil inlet.

 

kandi younes

... Résuméabuiyad

COMPONENTS AIR CONDITIONING Expansion Valves

 

 COMPONENTS AIR CONDITIONING Expansion Valves

 

 

Thermal Expansion Valves

Refrigerant flow to the evaporator must becontrolled to obtain maximum cooling,

while ensuring that complete evaporation  .of the liquid refrigerant takes place. This is  

 accomplished by the thermal expansion ,

valve (TXV).

Pressures in control

As shown in the illustration, the TXV

controls the refrigerant flow by using a

system of opposing pressures which will

call:

F1 - Temperature sensing capillary tube

Sealed tube filled with refrigerant. This

refrigerant is also filled above the

diaphragm (7). The capillary tube sensing

bulb (3) is attached to the evaporator

outlet tube surface.

F2 - Pressure compensation tube

This is a hollow tube connected to the

evaporator outlet tube and senses the

pressure of the R134a refrigerant leaving

the evaporator coil. (Other TX valves may

not use this tube as pressure is provided

internally within the valve).

F3 - Pressure spring

This spring (6) is located under the ball

valve (5).

 

Operation

Open

When the evaporator outlet tube

temperature increases, the refrigerant (3)

in the capillary tube expands, forcing the

diaphragm (7) downwards and thus

pushing pin (A) also downwards causing

the ball valve (5) to move away from the

metering orifice (4), allowing more R134a

to enter the evaporator inlet side.

Closed

As the evaporator outlet tube becomes

cooler, the refrigerant in the capillary tube

(3) contracts. Forces F2 and F3 cause the

diaphragm (7) and pin (A) to move upward

allowing the ball valve to move towards the

metering orifice (4), restricting the R134a

flow. The outlet tube gets warmer and the

process starts over.

 

 kandi younes

... Résuméabuiyad