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Equalising line on TEV

  • It is used in large evaporators , where pressure drop take place  at the end of evaporator ie, more than 0.3 bar
  • The pressure acting outsode the bellow from heat sensing bulb and capillary tube is total of the saturation pressure plus superheat . This pressure is trying to open the valve , overcoming the spring pressure.
  • The equilizing line has saturation pressure at the end of an evaporator coil acting from the bottom of the bellow ( diaphram ) . Hence the saturation pressure from equalizing line and capilliary tube is balancing each other.
  • The additional pressure from outside of bellow due to superheat is now reaponsible to open the expansion valve. By this arrangement , we are getting actual degree of superheat . Correct degree of superheat ensure that refrigerant is used efficiently and no liquid reaches to compressor  suction . Also evaporator shoulf not starved of  refrigerant.

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