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S3 Lec 2 (Condenser) Note


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Semester 3
CB303 Ventilation and Air Conditioning
Lec 2 (Condenser)

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S3 Lec 2 (Condenser) Note

  1. 1. CONDENSER FUNCTION • The function of the condenser is to transfer heat that has been absorbed by the system to the air or water.
  2. 2. CONDENSER PURPOSE • Thus the purpose of the condenser in the refrigeration system is to remove heat from the refrigerant vapor leaving the compressor (or generator in case of absorption system) so that the refrigerant will condense to its liquid state. • This liquid refrigerant will then be able to achieve the refrigerating effect in the evaporator.
  3. 3. CONDENSER PURPOSE • The condenser is a heat exchanger in a refrigerating system. • The condenser rejects heat which consists of a. Heat absorbed by the evaporator b. Heat from the energy input to the compressor
  4. 4. CONDENSER PURPOSE • The condenser is one of the important part of the refrigeration system. • The rate of heat transfer in condenser depends upon: a. Temperature difference b. Material of construction c. Types and quality of cooling medium d. Surface condition
  5. 5. CONDENSER OPERATION • Refrigerant always leaves the compressor at a temperature well above its saturation (condensing) temperature. • The refrigerant is thus in a superheated state. • In the first part of the condenser, sensible heat is removed. • The vapor is cooled to its saturation temperature.
  6. 6. CONDENSER OPERATION • After this, latent heat is removed when the vapor is cooled. • The size of the condenser is such that, the refrigerant leaving the condenser is a saturated liquid at the condensing temperature. • In number of cases, the condenser heat transfer surface area is great enough so that the liquid refrigerant is subcooled before it leaves the condenser. • The heat removed in the condenser is called the HEAT OF REJECTION.
  7. 7. CONDENSER AIR COOLED CONDENSER a. Natural convection air cooled condenser b. Forced convection air cooled condenser WATER COOLED CONDENSER a. Tube in tube condenser b. Shell and coil condenser c. Shell and tube condenser
  10. 10. AIR COOLED CONDENSER OPERATION • This is the condenser in which the removal of heat is done by air. • These condensers are the most popular type used on small commercial and domestic refrigeration and air conditioning units. • They consist of steel or copper tubing through which the refrigerant flows. • Tubes are usually provided with plate type fins to increase the surface area for heat transfer.
  11. 11. AIR COOLED CONDENSER OPERATION • Except for very small domestic units, which depends on gravity air circulation, heat transfer is efficiently accomplished by forcing large quantities of air through a condenser assembly. • The quantity of air circulated is usually 30m3 /min/ton or refrigeration.
  12. 12. AIR COOLED CONDENSER OPERATION • There are two types of natural draft air-cooled condensers. • The TUBE and FIN type shown in figure 1 and the plate type as shown in figure 2. • The FIN spacing is quite wide to reduce dust clogging.
  13. 13. AIR COOLED CONDENSER OPERATION • The fin spacing is wide to reduce clogging (TERSUMBAT) of condenser by dust. • The condenser with single row of tubing (BARISAN TIUB TUNGGAL) provide the most efficient heat transfer. • In small capacity refrigeration, single row condensers are used. • Like domestic refrigerators, freezers, water cooler etc. • The circulation of air over an air cooled condenser may be either by natural convection or by action of a fan or blower.
  14. 14. AIR COOLED CONDENSER Natural-draft condenser a. Natural convection air cooled condenser b. Forced convection air cooled condenser Plate type condenser a. Tube in tube condenser b. Shell and coil condenser c. Shell and tube condenser
  15. 15. AIR COOLED CONDENSER DISADVANTAGES i. It operates at a higher condensing temperature than a water cooled condenser. The higher condensing temperature causes the compressor to work more. ii. Large condensing surface is required for air cooled condenser as the air quantity circulated over the condenser is low.
  16. 16. NATURAL CONVECTION AIR COOLED CONDENSER • In this type of condenser, the heat transfer from the coil to the air is by natural convection. • This type of condensers have very limited us. • They are not capable of dissipating (MELEPASKAN)large quantities of heat because of the slow air movement over their surface. • Because of this, relatively large surface are required as compared to forced convection condensers.
  17. 17. NATURAL CONVECTION AIR COOLED CONDENSER • This condenser is manufactured economically. • It requires little maintenance. • It is commonly used in domestic refrigerators. • Fin spacing, if provided, is too wide in this type of condenser. • This is to reduce the possibility of the condenser being foulded with dirt and lint wide fin spacing also reduces, the resistance offered to free air circulation.
  18. 18. NATURAL CONVECTION AIR COOLED CONDENSER • This type of condenser is quite compact and easy to install and mount. • Cleaning of tubes are quite simple. • By lowing air over the finned surface. • This type on condenser require no water and present no problem of freezing in cold weather.
  19. 19. NATURAL CONVECTION AIR COOLED CONDENSER • Serious compressor problems can result if the condenser gets dirty. • The dirt will reduce the heat transfer rate and the compressor head pressure can rise to damaging levels. • The condenser can usually be cleaned with a brush and vacuum cleaner easily. Use: • These types of condensers are used only in small capacity applications such as domestic refrigerators, freezers, water cooler, and room air conditioner.
  20. 20. FORCED CONVECTION AIR COOLED CONDENSER • In this condenser, fan is used to force the air over condenser coils to increase the heat transfer capacity. • The propeller type fan or the centrifugal type fan may be used to move the air. • The type of fan used depends on design factors such as air resistance, noise level, space requirements etc.
  21. 21. FORCED CONVECTION AIR COOLED CONDENSER • The forced air type of air cooled condenser is more practical for larger capacities than the natural draft type condenser. • Air cooled condensers have the peculiar distinction (PERBEZAAN YANG PELIK) of being able to deliver increased capacity when it is not required. • An air cooled condenser is designed sufficiently (CUKUP) large to reject the required amount of heat when the outside air design temperature is actual outside air design temperature.
  22. 22. FORCED CONVECTION AIR COOLED CONDENSER • When outside air temperature drops, the condenser is able to reject more heat. • The cooling load in this case is less. • But the condenser is able to reject more heat. • This can create a problem on systems. • The refrigerant system will have to run even when the outside air temperature has dropped significantly.