Internally and externally TXVs are available for pressure compensation structures. For pressure compensation TXV equalized allowing the pressure on the low and high sides of the system to equalize in compressors outside the loop. This strategy allows die compressor in the unloaded state, reducing its starting torque requirement, and the motor current. This allows the use of less expensive, starting torque motors in many refrigeration applications.
These valves begin to equalize the pressure between the high and low sides die system, as only die compressor cycles off. The rising of the pressure in the evaporator, it causes the needle to move in the direction of the seat, stopping die refrigerant flow. When this occurs, the pressure equalization feature is enabled, needle-opens a spring-loaded shotgun port. When this opens the passage, die system of high and low side pressure quickly equalized. Die when starting the compressor, the evaporator pressure decreases, initiating flow through TXV seat and closing die bleed port. This allows TXV to function normally. Leveling the pressure of the expansion valve has been designed for use in smaller air conditioning and heat pumps with up to 4 tons (14 IcW) cooling capacity. Another type of pressure equalization TXV has a small drilled hole that is constantly open during startup and shutdown cycles die compressor systems.
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