3. Cooling systems main equipment:
The main equipment's used in Cooling systems will include
the following:
• Chillers & Compressors.
• Cooling Towers.
• Air Handling Units or Fan Coil Units.
4. Chillers & Compressors:
• The compressor compresses the refrigerant gas, causing it to
become much warmer than the outside air. The refrigerant
enters the compressor on the "suction side" and after it leaves
the compressor, the refrigerant is referred to as "hot gas”.
5. •Chiller is a machine that removes heat from a liquid
via a vapour-compression cycle. This liquid can then
be circulated through a heat exchanger to cool
equipment.
•The Chillers have two principal types of chiller are
air-cooled and water cooled. Compared to water, air
is a poor conductor of heat and therefore air-cooled
chillers are larger and less efficient.
6. Cooling Towers:
• A cooling tower is a heat rejection device, installed outside of the
building envelope, through which condenser water is circulated.
Refrigerant in the refrigeration cycle is condensed in a
refrigerant-to-water heat exchanger. Heat rejected from the
refrigerant increases the temperature of the condenser water,
which must be cooled to permit the cycle to continue. The
condenser water is circulated to the cooling tower where
evaporative cooling causes heat to be removed from the water
and added to the outside air. The cooled condenser water is then
piped back to the condenser of the chiller.
7.
8. Air Handling Units & Fan Coil Units
• The AHU is a complex component of an HVAC system that has
many different parts used to complete its function. These include a
cooling coil, heating coil, blower, humidifier, filter, and damper to
deliver controlled temperature throughout a large building.
• It accomplishes many different tasks, including transporting
outside air as it is often connected directly to the ductwork
throughout the indoor space. As the air is pulled in, it passes over a
hot or cold coil before being blown out to begin circulation.
9.
10. FAN COIL UNIT:
• A fan-coil unit is a small-scale air handling unit with circulation fan,
cooling or heating coil, filter, and appropriate controls. It is
essentially a terminal device because it serves only one room or a
small group of rooms.
• Fan-coil control is typically achieved through control of water flow
through the coil.
• The most critical performance issue facing an all-water fan-coil
system is ventilation air. Fan-coil units installed on an exterior wall
can be equipped with an outdoor air connection so that ventilation
may be provided. Fan coils installed in interior zones can not easily
provide such outdoor air ventilation. An air-water fan-coil system
can overcome this constraint.
11.
12. Difference Between AHU and FCU
• AHU is generally a bigger system than FCU.
• AHU is more complex than the FCU and that AHU are
often used in bigger establishments or spaces.
• The AHU system usually channels air through ducts
whereas the FCU don’t have any ductworks.
• AHU system treats outside air while FCUs basically
recycle or re-circulates the air.
• AHU have sections for reheating and humidifying
whereas the FCU does not have any.
• FCU are often observed to be noisier than the AHU.
13. Working of HVAC system :
There are four main cycles in HVAC system.
• Refrigeration cycle
• Condenser water cycle
• Chiller water cycle
• Air cycle
14.
15. Refrigeration cycle :
Main parts of refrigeration cycle are :
• Compressor
• Shell and tube type condenser
• Expansion valve
• Shell and tube type chiller
16. • In refrigeration cycle compressor pumps high pressure high temperature vapour refrigerant
in shell and tube type condenser through discharge line.
• High pressure high temperature vapour refrigerant occupies the shell side of condenser.
Actually the condenser has two parts –
1. Shell side which is filled of vapour refrigerant.
2. Tube side which is filled of water.
• In condenser tube temperature of water is less than vapour refrigerant which results in heat
exchange between vapour refrigerant and water. Thus water absorbs the heat of vapour
refrigerant and its temperature falls down and it converts into liquid due to condensation.
• After condensation liquid refrigerant further proceeds to expansion valve through liquid line.
• Expansion valve decreases the pressure of refrigerant and low pressure low temperature
liquid refrigerant goes into tube side of chiller. Actually chiller also has two parts-
1. Shell side which is filled with water.
2. Tube side which is filled with low pressure , low temperature liquid refrigerant.
17. • The temperature of liquid refrigerant is less than water
which results in heat exchange between liquid refrigerant
and water and thus liquid refrigerant extract heat from
water. Hence liquid refrigerant vaporises and chiller water
gets cooled.
• The vaporised low pressure low temperature refrigerant
again reached to compressor through suction line. Thus
refrigeration cycle accomplished.
18. Condenser water cycle :
Main parts of condenser water cycle are :
• Condenser water pump
• Condenser
• Cooling tower
19. • In condenser water cycle condenser water pump sucks
the cooled water of cooling tower and sends into tube of
condenser.
• Cool water of condenser tube absorbs the heat of high
temperature high pressure refrigerant in shell part.
Thus refrigerant gets condensed but temperature of
water rises. So for the cooling of water it is supplied to
cooling tower.
• Further the cooled water gets collected into sump of
cooling tower through which it again reaches to
condenser water pump and thus condenser water cycle
accomplished.
20. Chilled Water Cycle :
Main parts of chilled water cycle are :
• Chilled water pump
• AHU ( Air Handling Unit )
• Expansion Tank
• Shell and tube type chiller
21. • In chilled water cycle chilled water pump sucks the cooled water of chiller and sends into
cooling coil of AHU.
• The blower of AHU sucks the return air of AHU room. Return air is warmer than cooling
coil hence cooling coil absorbs the heat of return air and temperature of water of cooling
coil rises.
• The return water of cooling coil for re-cooling is supplied to shell side of chiller.
• In tube side , chiller has low pressure low temperature liquid refrigerant which absorbs
the heat of return water of cooling coil in shell side and gets vaporizes.
• The re-cooled water again supplied to cooling coil of AHU through chilled water pump.
• The volume of chilled water in chiller gets decreases due to cooling and chiller needs extra
water to fulfill this requirement. This extra water is supplied from expansion tank. When
plant is closed the volume of water in chiller rises due to rise in temperature of chiller and
this extra volume of water is send to expansion tank.
22. Air Cycle :
Main parts of air cycle are :
• AHU
• Supply air duct
• Supply air diffuser
• Air conditioned room
• Return air diffuser
• Return air duct
• Fresh air duct
• AHU room
23. • In air cycle the blower of AHU sucks the return air of AHU
room which gets filtered through AHU’s filter and further gets
cooled by cooling coil of AHU.
• The blower pumps the cooled air into supply air duct. The
function of supply air duct is to supply the air into AC room
through supply air diffuser which spreads the air into room.
• The warm air of room is return through return air duct into
AHU room.
• The return air in AHU room has less % of oxygen. To maintain
oxygen % fresh air is supplied in AHU room through fresh air
duct. Thus mixture of return air and fresh air again sucked by
AHU and cycle is completed.
