الفرق بين تكييف السيارات القديمة والحديثة والمنزل

[basselelsaedy]

بعد التحية
هل ينفع اركب تكيف مكروباص على سيارة 5 راكب صغيرة لزيادة التبريد وشكرا للرد؟

[basselelsaedy]

ممكن اعرف ما هو ابرد فريون ممكن اشحن بية السيارة فية ابرد من فريون 22 مثلاا؟

[mbx4e]

Evaporator controls
Evaporator controls are used to control the temperature of the evapora-
tor by regulating the flow of refrigerant through the evaporator. (Of course,
the evaporator temperature is also controlled by the cycling of the compres-
sor, which indirectly controls the flow of refrigerant through the evaporator.)
Evaporator controls are used mainly on older U.S.-built vehicles with com-
pressor which run constantly. Evaporator controls are seldom found on mod-
ern U.S. vehicles, or on any European or Japanese vehicles.
Evaporator controls help prevent freezing and help keep the air condi-
tioning system operating efficiently. As already noted, the flow of refrigerant
through the evaporator is the key to the efficient operation of an air condi- Heating and air conditioning
tioning system. Sometimes, under certain operating conditions, the conden-
sation which forms on the outside of the evaporator may freeze, which can
block the evaporator fins, and reduce the airflow through the evaporator.
This reduces the evaporator's cooling ability, and thus the cooling efficiency
of the system.
The most commonly used evaporator controls include the:
Suction throttling valve (STV)
Pilot Operated Absolute Suction Throttling Valve (POA STV)
Valves-In-Receiver (VIR)
Evaporator-Equalized Valves-In-Receiver (EEVIR)
Evaporator Pressure Regulator (EPR) valve
Suction Throttling Valve (STV)
The suction throttling valve (STV) was used on some early expansion
valve type air conditioning systems to control the refrigerant flow leaving the
evaporator. In an air conditioning system that uses an STV, the compressor
is running constantly as long as the system is switched on. A typical STV
opens or closes in response to refrigerant pressure to keep the pressure in
the evaporator within a predetermined range. This maintains the evaporator
temperature at a level that ensures efficient operation of the air conditioning
system without allowing the evaporator to freeze up.
Pilot Operated Absolute Suction Throttling Valve
(POA STV)
Most modern STVs are of the pilot operated absolute (POA) type. A POA
STV (see illustration) is really nothing more than a spring-loaded valve, con-
trolled by an evacuated bellows and needle valve assembly inside a housing.
The valve operates independently of atmospheric pressure, and is unaf-
fected by changes in altitude. By providing an opposing force to evaporator
pressure, the valve can maintain the evaporator pressure with a high degree
of accuracy (within a 1 psi range).
As long as the evaporator pressure remains above a predetermined level,
the POA STV remains open to allow refrigerant t o flow freely out of the evap-
orator. When the pressure drops below the predetermined level, the valve
loses, and the refrigerant flow from the evaporator is restricted. The pres-
sure in the evaporator then increases, which raises
the temperature and prevents icing on the outside of
the evaporator. The opening and closing cycle of the
valve continues as long as the compressor is run-
ning.
Valves-In-Receiver (VIR)
The valves-in-receiver (VIR) unit (see illustra-
tion) combines the functions of an expansion valve,
a POA STV and a receiver/drier into one assembly.
The VIR is usually installed near the evaporator. In a
VIR unit, the temperature-sensing bulb and capillary
tube for the expansion valve are eliminated because
the diaphragm end of the expansion valve is directly
exposed t o the refrigerant vapor entering the VIR as-
sembly from the evaporator outlet.
Evaporator-Equalized
Valves-In-Receiver (EEVIR)
The evaporator-equalized valves-in-receiver
(EEVIR) unit is a modified version of the VIR. It has a
redesigned expansion valve in order t o eliminate
temperature fluctuations in the system which occur
under certain operating conditions. The expansion
valve is also modified so that it is always partly open
instead of completely closed. This helps t o prevent
freezing at the expansion valve (which will block the
flow of refrigerant and prevent the system from op-
erating).
Evaporator Pressure Regulator
(EPR) valve
The evaporator pressure regulator (EPR) valve
(see illustration) is usually installed at the inlet port
of the compressor. The valve maintains the evapora-
tor outlet pressure within predetermined limits. An
EPR valve performs the same function as the STV.
Typical Evaporator Pressure Regulator (EPR) valve
Driveability controls
An air conditioning compressor takes a significant amount of power to
run (on average, somewhere between 10 and 1 5 horsepower), and the effect
of compressor operation, in conjunction with other demands placed on the
engine, can impose loads which reduce vehicle performance. This is a signif-
icant problem on vehicles with small capacity engines.
Driveability controls are used to control the operation of the compressor
to relieve the load on the engine under conditions when driveabllity may suf-
fer. These controls don't usually affect the cooling performance of the air
conditioning system. On most modern vehicles equipped with engine man-
agement systems, the compressor clutch is controlled by the electronic con-
trol unit (ECU) or the powertrain control module (PCM). The compressor is
controlled in accordance with the information received from the various en-
gine management system sensors, to ensure that the driveability of the vehi-
cle doesn't suffer. This reduces the need for separate driveability controls.
Typical driveability controls include the:
Time delay relay
Wide-open throttle switch
Closed throttle switch
Low vacuum switch
Power steering pressure switch
Power brake switch
Engine coolant high temperature switch
Constant run relay
Compressor delay timer
Anti-dieseling relay
High-pressure relief valve

[الايطالى الصغير]

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هو ده المفيد

ومشكورين على الموضوع الجامد فعلا




ربنا يجازيكم عنا خير

[Ahmed AlGamal]

ايه المواضيع الجامدة ده ... ماشاء الله

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