It gives information about Heating systems – warm air systems, hot water systems, steam heating systems, panel and central heating systems, Heat pump circuit and Heat sources for heat pump.

1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423 603
(An Autonomous Institute, Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Department of Mechanical Engineering
Subject:- Heating, Ventilation and Air
Conditioning (ME 411)
B.Tech.Mechanical
Purushottam W. Ingle
Assistant Professor

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3. • Heat pump is refrigerant cycle utilizing heat source like atmosphere,
sea etc.
• Heat pump exchanges heat with two sources, sink and atmosphere.
• To produce heating effect Q2, extra work is supplied along with heat
taken Q1 from atmosphere.
• High temperature high pressure refrigerant is made to flow through
the condenser, condenser in this case is fitted inside the room,
condenser reject heat to the room and room get heated.
• Then refrigerant get condensed, this condensed refrigerant is
throttled in expansion device before entering into evaporator.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

4. • The evaporator is fitted outside the room, where it takes the heat
from source, which is at 5 degree Celsius as shown, so here
refrigerant get evaporated, this low temperature low pressure
refrigerant comes to the compressor for compression, this completes
the cycle.
• So in short here the condenser is placed inside the room, and
evaporator is placed outside the room.
• In cold region or countries when the atmospheric temperature is less
than the comfort temperature, here heat pump is used.
• In cold countries, near about for 7 to 8 months, the atmospheric
temperature is lower than the comfort temperature.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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7. • Heat pump is used as a year round air conditioner.
• In cooling cycle, we requires cooling, there is a inside coil and outside
coil, the refrigerant from inside coil or evaporator goes to the
compressor, then from compressor it goes to the outdoor unit or coil
which acts as a condenser. Here refrigerant get condensed.
• Then the condensed refrigerant is expanded by using expansion
device.
• This cycle is required for summer condition.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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10. • During winter condition, with the help of some mechanism the
reversing valve is changed, the outdoor unit or coil is connected to
suction line.
• Outdoor unit is acts as an evaporator, the low pressure low
temperature refrigerant comes to the suction line, the compressor
compresses it to required pressure.
• Then HP HT refrigerant from compressor is goes to the indoor unit or
coil, condenser, it dissipates heat to the air and get condensed when
the temperature is less than the comfort condition.
• Then cycle repeats.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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13. Air to Air fixed air circuit
• Air circuit remains same and refrigerant changes its direction.
• Total 8 valves are provided, depending upon operation, four valves are
opened and four valves are closed.
• For cooling modes, valves 1,2,3,4 are opened.
• for heating mode, valves 5,6,7,8 are opened.
• For cooling mode, high pressure, high temperature refrigerant from
compressor is made to flow through outdoor unit through valve 1, the
refrigerant is condensed, and is then flow through expansion valve, as valve 2
is open.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

14. • Refrigerant is then expanded, its pressure and temperature
decreases, as valve 3 is opened, the refrigerant now flows through
conditioned coil, it absorbs heat from the surrounding air, cools the
surrounding air and it is called cooling application.
• Now valve 4 is opened, the refrigerant is returned to the compressor.
• During heating mode valves 5,6,7,8, are opened.
• The high temperature high pressure refrigerant is made to flow
through conditioned coil, through valve 5, it rejects heat to the
surrounding, surrounding air becomes hot.
• Now refrigerant get condensed, 6 valves is opened, it goes to
expansion valves, then goes to the outdoor coil through valve 7.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

15. • Then refrigerant absorbs heat from the surrounding air and gets
evaporated.
• Now evaporated refrigerant goes to the compressor again through
valve 8 and cycle continues.
• So here air does not change its direction, only the refrigerant changes
its direction.
• That’s why it is called fixed air circuit.
• This system is used for small residential appications.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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17. Air to Air fixed refrigerant Circuits
• Here air changes its direction, refrigerant doesn't change its direction
• From the evaporator low temperature low pressure refrigerant enters into
the compressor, it compressed to required pressure, then it goes to the
condenser, condensation takes place and then expansion.
• The partition is provided as shown, four plate type baffles are provided,
during cooling operation, the baffles A,B,C, D are opened.
• The air form the conditioned space comes in contact with the evaporator
coil, air get cooled, then the cooled air supplied to the conditioned space,
because G ,H are closed so air flows from A to B.
• Now since C, D are opened, the outside air flows over the condenser takes
heat from refrigerant, then the outside air flows through D to environment.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

18. • All above is for cooling mode.
• For heating mode, E,F,G,H are opened, from the conditioned space,
the air is made over the condenser, air becomes warm and warm air
is supplied to the conditioned space.
• The outside air flows over the evaporator coil, evaporation takes
place, and the air passed to the atmosphere through G.
• In this case A,B,C,D are closed.
• Here the refrigerant doesn’t change its direction, but air changes.
• So here heat is taken form the air in evaporator and is given to the air
from condenser so called as Air to Air heat pump.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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20. Air to water design
• Here heat is taken from air and is given to water during winter
season.
• Valve 1,2,3,4 are opened during summer season and valve 5,6,7,8 are
opened during winter season.
• So in cooling mode 1,2,3,4 are opened, so here high pressure high
temperature refrigerant from compressor goes to the outdoor coil
through valve 1, it gives its heat to the atmospheric air, so because of
rejection of heat refrigerant get condensed.
• Now valve 2 is opened, so condensed refrigerant is made to flow to
expansion valve, then through 3 it flows to the heat exchanger, where
it absorb heat from the water, so water get cooled.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

21. • This cooled water is supplied to the storage tank, and it is pumped to
the air conditioning coil, it takes heat from the air, and water get
heated.
• This warm water again dissipates heat to the refrigerant.
• This is all about cooling mode.
• So refrigerant get evaporated now, valve 4 is opened goes to the
compressor.
• So this completes the cycle for cooling mode.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

22. 1
• For heating mode valve 5,6,7,8 are opened.
• High temperature, high pressure refrigerant is passed through valve 5,
is made to flow through the heat exchanger, it reject heat to the
water and water get heated.
• The hot water is circulated through the conditioning coil and it reject
heat to the air, and air get heated.
• Now due to rejection of heat in heat exchanger, refrigerant get
condensed, after condensation, valve 6 is opened.
• The refrigerant get expanded in expansion valve, now valve 7 is
opened, it enters into the outdoor unit, refrigerant absorbs heat from
the surrounding air.
P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
9/4/2023

23. • Compressor add heat in that again, and then further this combined
heat through refrigerant is passed to heat exchanger.
• This heat of refrigerant in heat exchanger is exchanges with water and
cycle continues.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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25. • Same circuit diagram is used as that used in air to water.
• Here During cooling mode 1,2,3,4 valves are opened and for heating
mode valve 5,6,7,8 are opened.
• Here water is used for exchanging the heat, otherwise remaining
operation is same.
• In this case heat is taken from water and is given to air directly.
• It is called water cooled air conditioning system.
• It is suitable for packaged air conditioner, not for central AC.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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27. • For cooling mode, valve 1,2,3,4 are opened, conditioner coil acts as
an evaporator, now warm water from conditioner coil through valve 1
made to flow through the evaporator, water dissipates heat to the
refrigerant.
• Refrigerant get evaporated, and water get cooled. This cooled water is
again recirculated to the conditioner coil through valve 2, pumped to
the conditioner coil.
• This is the cooling circuit where the conditioner coil acts as a cooling
coil.
• Now pump P2 pumps the water from source or river, flowing through
3.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

28. • This water is circulated through the condenser, so it absorbs heat
from the refrigerant, and refrigerant get condensed.
• This water is then drain back to river or source through valve 4.
• During heating mode, valve 5,6,7,8 are opened.
• Hot water is made to flow through the conditioner coil, so room air
get heated, now the warm water is made to flow to the condenser
through 5, it takes heat from refrigerant.
• Again warm water is circulated to conditioned coil to heat air through
valve 6.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

29. • Now water from source is pumped through valve 7 to exchange heat
in evaporator, so here refrigerant takes heat from water and get
evaporated.
• Then cooled water is now goes to the water source through valve 8.
• So here heat is taken from the water in evaporator and it is given to
the water in condenser.
• So it is called water to water heat pump.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

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31. • At some location water used may not pure, so here hard water may
be available, if hard water is used, it may causes some corrosion
problem, may be scaling problem occurs.
• To avoid this some special anticorrosion liquid is used.
• Again here for cooling mode 1,2,3,4 are opened.
• For heating mode 5,6,7,8 are opened.
• During cooling mode condenser water exchange heat with outdoor
unit, and evaporator water exchanges heat with indoor unit.
• During heating mode, condenser water exchanges heat with
conditioner coil and evaporator water exchanges heat with outdoor
unit.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon