Components Automotive Air Conditioning Compressors parti 2

Components Automotive
Air Conditioning
Compressors

parti 2

 Rotary Vane - Panasonic:

Rotary vane compressors consist of a rotor with three or four vanes and a carefully shaped
rotor housing. As the compressor shaft rotates, the vanes and housing form chambers.
The R134a is drawn through the suction port into these chambers, which become smaller as
the rotor turns. The discharge port is located at the point where the gas is fully compressed.
The vanes are sealed against the rotor housing by centrifugal force and lubricating oil. The
oil sump and oil pump are located on the discharge side, so that the high pressure forces oil
through the oil pump and then onto the base of the vanes keeping them sealed against the
rotor housing.

During idle an occasional vane noise from the compressor may be heard. This is due to the
time taken for lubricating oil to circulate through the A/C system.

Compressors and Mount & Drive:
Mount & Drive
Consists of a bracket to mount the compressor to the engine, a belt idler pulley, compressor
drive belt and possibly and extra drive pulley for the crankshaft.
Compressor Mount

Manufactured of either plate, cast iron, steel or aluminium, this bracket should exhibit
excellent noise absorption qualities especially if using a piston type compressor.
Idler Pulley
A small pulley normally used in conjunction with a belt adjusting mechanism, also used when
a belt has a long distance between pulleys to absorb belt vibrations.
Drive Pulley
Some vehicles do not have an extra pulley to accommodate an A/C drive belt, in these
cases an extra pulley is bolted onto the existing crankshaft pulley.

Clutches:
Compressor Clutch
The clutch is designed to connect the rotor pulley  to the compressor input shaft when the field coil is energized. The clutch is used to transmit the power from the engine crankshaft to the
compressor by means of a drive belt. When the clutch is not engaged the compressor shaft does not rotate and refrigerant does not circulate the rotor pulley free wheels. The field coil is actually an electromagnet, once energized it draws the pressure plate towards it, locking the
rotor pulley and the pressure plate together causing the compressor internals to turn, creating
pressure and circulating refrigerant. 

 
Lubrication:

R134a is part of the air conditioners lubrication system. NEVER operate an A/C system
without refrigerant as there will be no lubrication for the compressor and internal damage will
occur.
Refrigerant oil is circulated around the A/C system saturated in the refrigerant.
Ariazone recomends PAOil as best automotive compressor lubricant.
PAOil is a Polyalpha Olefin, Not a PAG or an Ester. This is a fully synthetic oil,
carefully blended to be a superior oil. It is so good that it can be used in all
automotive compressors, whatever the brand. It's a non-agressive, safe oil
that won't effect seals or hoses and is compatible with other lubricants.
And it's non-hygroscopic.

Precautions when using PAG oil::
- Do not allow PAG oil to contact bare skin or vehicle paintwork.
- Flush skin immediately when using PAG oil.
- Avoid breathing PAG oil/R135a mixture.
- PAG oil is highly hygroscopic. Open containers only when ready to use. Cap container
immediately after use.

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Components Automotive Air Conditioning Compressors parti 1

Components Automotive
Air Conditioning
Compressors

parti 1

General:
There are various makes and types of compressors used in automotive air conditioning systems operating on R134a. The internal design could be Piston, Scroll, Wobble plate, Variable stroke or Vane. Regardless, all operate as the pump in the A/C system to keep the
R134a and lubricating oil circulating, and to increase the
refrigerant pressure and thus temperature.

Sanden - Wobble plate:

A reciprocating piston, fixed displacement compressor.The pistons are operated by a wobble plate, whichmoves them backwards and forwards in the cylinders. As the front shaft turns the wobble plate angle changes, causing the pistons to move in and out, pulling refrigerant vapor in through the suction side, compressing it and discharging this high pressure vapor into the condenser.

                                                                          

Scroll type - Sanden:

This compressor uses a unique design with two scrolls,one fixed and one is movable, both are inter-leaved. The movable spiral is able to ORBIT or oscillate without actually fully rotating. The movable scroll is connected to the input shaft via a concentric bearing. As the movable spiral oscillates within the fixed spiral, a number of pockets are formed between the spiral. As these pockets decrease in size the refrigerant is squeezed, the pressure increases and is discharged

 through a reed valve at the discharge port in the rearsection of the compressor.

                                                                   

 Compression Cycle:

Variable stroke - Harrison V5:

The Delphi (Harrison) V5 compressor is a non-cycling variable displacement compressor.
The compressor varies displacement to control capacity to meet A/C system demand at all
operating conditions. The compressor features a variable angle wobble plate in five (V5)
cylinder axial piston design.
Displacement is controlled by a bellows actuated control valve located in the rear cylinder
head. This control valve senses and responds to the system suction pressure or A/C system
demand. Through regulation of compressor crankcase pressure, the wobble plate angle, and
therefore compressor displacement is variable.
In general, the compressor discharge pressure is much greater than the compressor
crankcase. Which is greater than or equal to the compressor suction pressure. At maximum
displacement, compressor crankcase pressure is equal to the compressor suction
pressure. At reduced or minimum displacement, the compressor crankcase pressure is
greater than the suction pressure.

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Automotive Air Conditioning System types A/C System with

Automotive
Air Conditioning

System types

 A/C System with

 

 A/C System with: Thermal Expansion Block Valve, Serpentine Condenser,
Serpentine Evaporator:

Note: 

Temperatures shown are examples only :

 

 A/C System with: Expansion Valve, Parallel Flow Condenser, Plate and Fin Evaporator:

A/C System with: Orifice Tube, Accumulator, Parallel Flow Condenser
Plate and Fin Evaporator

 Dual A/C System with: Externally Equalized Expansion Valves (x2),
Serpentine Condensers in series (x2),
Serpentine Evaporator in parallel (x2),
Electrical Refrigerant Flow Shut Off Valves.

 >

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Automotive Air Conditioning Principles of Air Conditioning

 Automotive
Air Conditioning
Principles of Air Conditioning

High pressure side:

Low pressure R134a vapor entering the compressor is compressed to become high
 pressure/temperature R134a vapor. This is then circulated along with lubricant oil to the
condenser. As the high pressure/temperature vapor travels through the condenser, heat is
released to the cooler ambient air passing over the condenser tubes condensing the vapor into a liquid. This high pressure/temperature liquid then travels through the filter drier onto the expansion valve where a small variable orifice provides a restriction against which compressor pushes.

Low pressure side:

Suction from the compressor pulls the high pressure/temperature liquid R134a through
small variable orifice of the TX valve and into the low-pressure side of the A/C system.
The R134a is now under low pressure/temperature vapor where heat from the cabin being blown over the evaporator coil surface is absorbed into the colder low pressure refrigerant The R134a is then pulled through the evaporator and into the compressor. The A/C cycle begins again as the R134a vapor is compressed and discharged under pressure.

Heat transfer:

R134a in the LOW-PRESSURE side is COLD and can absorb large quantities of heat from
the air moving over the evaporator. R134a in HIGH-PRESSURE side is HOT and the cooler ambient air moving over thecondenser can absorb the heat from it.

Summary:

- When the R134a pressure is low, the R134a  temperature is low.

- When the R134a pressure is high, the R134a temperature is high.

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Automotive Air Conditioning R134a Properties

 Automotive
Air Conditioning
R134a Properties

R134a Properties:

Since 1993 the Automotive industry of developed countries has started to use a non-ozone-depleting refrigerant HFC 134a (hydrofluorocarbon), its chemical name being Tetra Fluoroethane. We commonly refer to this refrigerant as R134a
<
R134a was selected as a replacement refrigerant for R12 (Dichlorodifluoromethane)
because R12 containing chlorine has a major effect to ozone layer depletion.

R134a and water have the same abilities to change the state, but R134a can do this more
rapidly and at much lower temperature than water. At anytime above -26.3 C, R134a
change its state, becoming a vapor and absorb large quantities of heat from inside the
vehicle. This is what creates the cooling effect you feel inside the vehicle.

R134a is stored in containers under high pressure. If it is released into the atmosphere, it
will boil at -26.3 C.

Refrigerant R134a:

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Automotive Air Conditioning The ozone layer

 Automotive
Air Conditioning
The ozone layer

The ozone layer:

Ozone (O ) is formed in upper atmosphere (stratosphere), approximately 10 to 50 km above the earth surface.
This layer acts as a shield that protects the earth's surface from harmful ultra violet radiation coming from the sun.

The chlorine contained in CFC's rise into the ozone layer and destroys the ozone molecule O .
Depletion of the ozone layer can be catastrophic to human life causing problems such as:
- Skin cancer
- Eye cataracts
- Reduced immunity to disease
- Damage to crops
- Reduced aquatic life

Background:

-1974 - It was first recognized that the use of chlorofluorocarbons (CFC's) was potentially having a detrimental effect on the ozone layer.
-1987 - The Montreal protocol was adopted. This protocol called for restrictions on the manufacture
and usage of CFC's to 1986 levels. From 1987 manufacturers could only produce the same
quantities as produced in 1986.
-1990 - A second Montreal protocol meeting was held and recommended a total phaseout of ozone depleting refrigerant by the year 2000.
-2000 - Total phaseout of CFC's.

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