0
1.1kviews
Write Short note on types of condensers and evaporator.
1 Answer
1
15views

THE CONDENSER

  • Heat exchange surface that rejects system heat
  • Rejects sensible heat
    • De-superheating vapour refrigerant from the compressor
    • Subcools refrigerant at the outlet of the condenser
  • Rejects latent heat during the condensing process
  • The greatest amount of heat is transferred during the change of state
  • Condenser is on the high pressure side of the refrigeration system

TYPES

WATER-COOLED CONDENSERS

  • More efficient than air-cooled condensers
  • Water temperature can be maintained
  • Water temperature directly affects system pressures
  • Three types of water-cooled condensers
    • Tube within a tube condenser
    • Shell and coil condenser
    • Shell and tube condenser

TUBE WITHIN A TUBE CONDENSER

  • Heat exchange takes place between the fluids in the inner and outer tubes
  • Refrigerant flows in the outer tube
  • Water flows in the inner tube
  • Refrigerant and water flow in opposite directions to maximize the heat transfer rate
  • Depending on the construction, the condenser can be cleaned mechanically or chemically

MECHANICALLY CLEANABLE CONDENSERS - Tube within a tube condenser has end flanges - Flanges are removed to access the water circuit - The refrigerant circuit remains sealed while the water circuit is open - The mechanically cleanable tube-in-tube condenser is more costly than the chemically cleanable version of the condenser

SHELL AND COIL CONDENSERS

  • Coil of tubing enclosed in a welded shell
  • Water flows through the coll
  • Refrigerant from the compressor is discharged into the shell
  • The shell also acts as the receiver
  • When refrigerant comes in contact with the cold coll, It condenses and falls to the bottom

SHELL AND TUBE CONDENSERS

  • Can be cleaned mechanically
  • Compressor discharge gas is piped into the shell
  • Water flows through the tubes in the condenser
  • The ends of the shell are removed for cleaning
  • The shell acts as a receiver
  • Refrigerant circult is not disturbed when the ends of the shell (water boxes) are opened
  • Most expensive type of condenser
  • This condenser must be cleaned chemically

Evaporators

  • IT IS A COMPONENT OF A REFRIGERATION SYSTEM
  • IT IS USED TO EXTRACT HEAT FROM THE CHAMBER WHERE
  • TEMPRATURE MAINTAINESS IS REQUIRED.
  • NO WORK IS ABSORBED OR SUPPLIED
  • NO CHANGES IN KINETIC ENERGY AND POTENTIAL ENERGY

    Types

SHELL AND COIL TYPE EVAPORATOR

  • These are of smaller capacity than the shell and tube chillers.
  • These are made from one or more spiral shaped bare tube coils enclosed during a welded steel shell.
  • It is usually dry expansion type with the refrigerant flowing within the tube and chilled liquid within the shell. In some cases the chiller operates in flooded mode also with refrigerant within the shell and chilled water flowing thorough the spiral tube.
  • The water within the shell gives an outsized amount of thermal storage capacity called hold-up capacity. It is used for cooling beverage in chrome steel tanks to maintain sanitary conditions. It is also utilized in bakeries and photographic lab.

DOUBLE PIPE TYPE EVAPORATOR

  • This consists of two concentric tubes, the refrigerant flows through the annular passage while the liquid being chilled flows through the tube in counter flow.
  • The inner tubes undergo the headers and are connected together by 180° bends. The refrigerant side is welded hence there is minimum possibility of leakage of refrigerant.
  • These could also be utilized in flooded also as dry mode. This needs more room than other designs. Shorter tubes and counter flow gives good heat transfer coefficient.

BAUDELOT TYPE EVAPORATORS

  • This type of evaporator consists of an outsized number of horizontal pipes stacked one on top of other and connected together by headers to form single or multiple circuits.
  • The refrigerant is circulated inside the tubes either in flooded or dry mode. The liquid to be chilled flows during a thin layer over the outer surface of the tubes. The liquid flows down by gravity from distributor pipe located on top of the horizontal tubes.
  • The liquid to be chilled is hospitable atmosphere i.e. it is at air pressure and its aeration may happen during cooling. This is often widely used for cooling milk, wine and for chilling water for carbonation in bottling plants.

DIRECT EXPANSION FIN AND TUBE TYPE EVAPORATOR

  • These evaporators are used for cooling and dehumidifying the air directly by the refrigerant flowing within the tubes.
  • Almost like fin-and-tube type condensers, these evaporator consists of coils placed during a number of rows with fins mounted there on to extend the warmth transfer area.
  • Tubes with individual spiral straight fins or crimpled fins welded and are utilized in some applications like ammonia.

PLATE SURFACE EVAPORATORS

These are also called as bonded plate or roll-bond type evaporators. Two flat sheets of metal (usually aluminum) are embossed in such a fashion that when these are welded together, the embossed portion of the 2 plates makes a passage for refrigerant to flow. This sort is used in household refrigerators

PLATE TYPE EVAPORATORS

  • These evaporators are widely used in dairy plants for chilling milk, in breweries for chilling beer.
  • These evaporators consist of a series of plates (normally made from stainless steel) between which alternately the milk or beer to be cooled and refrigerant flow in counterflow direction.
Please log in to add an answer.