S3 Lec 2 (Condenser) Note

CONDENSER

FUNCTION• The function of the condenser is to transfer

heat that has been absorbed by the system to the air or water.

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.

CONDENSER

PURPOSE• The condenser is a heat exchanger in a

refrigerating system.• The condenser rejects heat which consists of

a. Heat absorbed by the evaporatorb. Heat from the energy input to the compressor

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 differenceb. Material of constructionc. Types and quality of cooling mediumd. Surface condition

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.

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.

CONDENSER

AIR COOLED CONDENSERa. Natural convection air

cooled condenserb. Forced convection air

cooled condenser

WATER COOLED CONDENSERa. Tube in tube condenserb. Shell and coil condenserc. Shell and tube condenser

CONDENSER

Fig 1: NATURAL DRAFT CONDENSER Fig 2: PLATE TYPE CONDENSER

CONDENSER

FORCED CONVECTION AIR COOLED CONDENSER

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.


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.


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.


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.


Natural-draft condensera. Natural convection air

cooled condenserb. Forced convection air

cooled condenser

Plate type condensera. Tube in tube condenserb. Shell and coil condenserc. Shell and tube condenser


DISADVANTAGESi. 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.

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.


• 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.


• 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.


• 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.


• 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.


• 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.


• 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.