The expansion valve is one of the four components of the refrigeration system, the composition is also an important component of the refrigeration apparatus, generally mounted between the reservoir and the evaporator cylinder. In the system responsible for the refrigerant evaporation pressure reduced from the condensing pressure, the liquid refrigerant expansion valve temperature and high pressure by throttling its temperature low-pressure wet steam, and then the refrigerant absorbs heat to achieve the cooling effect in the evaporator, the expansion valve valve flow is controlled by varying the degree of superheat of the evaporator end, to prevent the area of the evaporator utilized and knock phenomena. It mainly serves as a throttle to reduce and regulate the flow. It also has a wet compression and to prevent liquid slugging function and abnormal overheating.
1. The expansion valve characteristics
1, the expansion valve is advanced structure of the double balanced flow orifice.
2, the expansion valve superheat stable, so that the system is stable.
3, the expansion valve due to the use of bi-flow thermal expansion valve, the expansion amount of the refrigeration system Province valve, solenoid valve and check valve.
4, an expansion valve suitable for refrigeration, air conditioning and other operational needs.
5, an expansion valveBidirectional balance orifice, so that the degree of superheat still change as the condensing pressure or the pressure drop through the valve port varies.
6, the expansion valve evaporation temperature range: -40 ℃ to + 10 ℃.
7, the expansion valve is applied to R12, R22, R134a and other media.
2. The composition of the expansion valve
by the valve body of the expansion valve, bulb, balance tube composed of three parts.
1. Body
direction means for controlling the fluid pressure and flow
. Piping and valves is to media within the apparatus (liquid, gas, powder) or stop the flow, and means to control the flow rate.
2. Temperature bag
filling the bulb is in the saturated refrigerant liquid equilibrium, this portion of the refrigerant and the refrigerant in the system do not communicate. It is generally tied to the evaporator outlet pipe, the pipe in close contact with the superheated steam felt outlet temperature of the evaporator, because the refrigerant inside it is saturated, so passed to the saturation pressure at a temperature depending on the temperature of the valve body. When
bulb common cause failure
The expansion valve when the liquid supply system appears uneven expansion valve is closed or not small, superheat degree of supercooling phenomena such as incorrect. The reason is probably the bulb out of trouble.
1) fracture capillary bulb, so that filling was missing in the bulb, the leads can not perform correct signal to the thermal expansion valve mechanism.
2), temperature of dressing position is incorrect.
2, bulb failure approach
In general, temperature of the gas return pipe is mounted on the possible horizontal sections of the evaporator outlet, away from the compressor suction and adjacent to the evaporator, but not perpendicular installation. Since the sensitivity of the sensing bulb is mounted in an upper portion of the intake pipe may decrease reaction may cause excessive refrigerant evaporator, the sensing bulb is mounted at the bottom of the intake pipe will cause disorder of the liquid supply, because there is always a small amount of the liquid refrigerant flows to the position bulb mounted, leads to a rapid change of bulb temperature.
When installed, required temperature package wrapped copper, rust return pipe to the surface, if the steel surface coated with rust silver paint to ensure good contact with the bulb return pipe. Thermal package must be below the top of the valve diaphragm chamber, and a head to be placed horizontally bulb or downward, when the relative position of the chamber above the diaphragm, should be bent into a U-shaped capillary, so that the liquid entering the membrane the cavity sheet. In order to avoid sudden system shutdown, the refrigerant fluid or oil accumulated in the horizontal section of pipe bulb located affect the performance bulb, the tube sections after the bulb should be made
3. balancing pipe [123 ]
the balancing pipe connected at one end remote from the evaporator outlet is slightly bulb position, directly connected to the valve body by a capillary. Function is passed the actual pressure in the evaporator outlet to the valve body. There are two diaphragm valve body, the diaphragm moves upward refrigerant flow through the expansion valve under reduced pressure, to seek in the dynamic balance.
3. The expansion valve Category
1. From the point of view in a balanced manner, the expansion valve can be divided into the inner and outer balanced balanced two.
innerBalanced equilibrium pressure in the inlet of the evaporator take, is taken outside the balanced equilibrium pressure at the outlet of the evaporator. The balanced expansion valve is generally used in home air conditioners, automotive air-conditioning cooling capacity is generally relatively large, the pressure loss of the refrigerant in the evaporator is large, and therefore only the external balance.
2. From the point of view of the adjustment structure superheat, the expansion valve and redeployment into the modal type.
1) can only be adjusted within a modal installed before the air conditioning system, it has the advantage of smaller size, compact structure suitable for bulk styling products.
2) may induce a formula adjusted according to the situation at any time in the air conditioning system has great flexibility, but increases the size and weight of parts must be such that larger.
4. The method of adjusting the correct
(1) To adjust the thermal expansion valve, air conditioning and refrigeration must be confirmed due to the thermal expansion valve abnormality optimum operating point deviates due to, not because fewer freon dried filter clogging, the filter for other reasons, fans, etc. caused by the belt. At the same time, it is necessary to ensure the accuracy of the sampled signal bulb temperature sensing mounting position must be correct, may not be attached directly beneath the pipe, the pipe bottom in case the product oil factors correct temperature sensing bulb.
(2) adjusting the thermal expansion valve Note
The thermal expansion valve adjustment, it must be performed in the normal operating state of the refrigeration apparatus. Can not be placed due to evaporation surface pyrometer, may be utilized as the saturation pressure of the compressor suction pressure in the evaporator, the evaporation temperature of the look-up table approximate. A return pipe temperature measured by the temperature, and evaporatedComparative sent to check the degree of superheat temperature.
to adjust, if the degree of superheat was too small, the adjusting screw may be rotated clockwise (i.e., the spring force is increased, reducing the thermal expansion valve opening degree), the flow rate is reduced; conversely, if was too large degree of superheat, i.e., the liquid supply is insufficient, the adjustment screw can be rotated in the opposite direction (counterclockwise), the flow rate increases. Since the thermal expansion valve of the temperature sensing system of the actual work there is a certain thermal inertia, formed signaling delay, before proceeding next adjustment operation after the stable. Thus adjustment process must be patient and carefully adjusting the number of turns of screw rotation time should not be too fast. The digital thermometer probe is inserted into the evaporator return air inlet (corresponding to the temperature sensing package location) of the insulation;
(3) the step of adjusting the thermal expansion valve
1) stop. The gauge is connected to the three-way valve to the low pressure compressor.
2) power; more than 15 minutes so that the compressor runs into the steady state, the pressure and temperature display indication reaches a stable value.
3) reading out a digital thermometer temperature T1 corresponding to the measured pressure and gauge temperature T2, the degree of superheat is the difference T1-T2 two readings.