ဒါကေတာ့DVMမွာပါဝင္တ့ဲ အစိတ္အပိုင္းအခ်ဳိ႔နဲ႔ အလုပ္လုပ္ပုံေတြပါ။
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The need for head pressure control
Refrigeration systems are designed around certain criteria:
- Evaporator-compressor capacity;
- Type of refrigerant used;
- Evaporator temperature;
- Condensing temperature;
- Total system pressure drop;
- Pressure drop across the TX valve; and
- Liquid temperature.
Let’s look at a system with a capacity of 12,000 Btuh, R-22, 20°F evaporating temperature, 110° condensing temperature, 50-psi system pressure drop (including distributor pressure drop), and 100° liquid temperature.
Convert the condensing and evaporator temperatures to pressures and we get 226 over 43, which is 183-psi pressure difference from high side to low side. Then subtract for system pressure drop of 50 psi, which is 35 psi for the distributor and 15 psi for system components and line pressure drop.
This leaves us with a net pressure drop across the TX valve of 133 psi and makes the TX valve selection a 1-ton externally equalized valve. This delivers approximately 1.06 tons with no correction for liquid temperature, as the liquid temperature will be approximately 100°.
This makes a perfect match to evaporator capacity at the design conditions of 90° ambient with a 20° condensing temperature difference.
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Shut off valves
Filter Driers
Filter driers are devices used in a HVAC system that are a combination of filter and dryer (or drier). A filter is used to remove any particle such as dirt, metal or chips from entering the refrigerant flow control. The refrigerant flow control device could be thermostatic expansion valve or simply a capillary tube.
The filter is sometimes also referred to as a strainer. It is critical that these particles are filtered out and prevented from going into the metering device. It can cause blockage to the passage flow of the refrigerant in the expansion valve and cause improper operation to the system.
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Solenoid valve
A solenoid valve is an electromechanically operated valve. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports. Multiple solenoid valves can be placed together on a manifold.
Solenoid valves are the most frequently used control elements in fluidics. Their tasks are to shut off, release, dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast and safe switching, high reliability, long service life, good medium compatibility of the materials used, low control power and compact design.
Besides the plunger-type actuator which is used most frequently, pivoted-armature actuators and rocker actuators are also used.
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Moisture and Liquid Indicator
The Sporlan See•All Moisture and Liquid Indicator combines the two functions of moisture and liquid indication into a single economical product. It takes the guess work out of servicing refrigeration and air conditioning equipment. The See•All assists the technician in determining the state of the circulating refrigerant at a particular location and if a safe moisture level exists in the system. Excessive moisture in refrigerant systems can cause unwanted chemistries such as hydrolysis of lubricants and other materials, corrosion of metals, copper plating, ice formation at the meeting device and a chemical change in the motor insulation of a hermetic compressor.
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