The document discusses different types of heat pumps, including air source heat pumps (ASHP), water source heat pumps (WSHP), and geothermal heat pumps (GHP). It explains that heat pumps use a vapor compression cycle and reversible components to provide both heating and cooling. For ASHP, heating and cooling is done by extracting or rejecting heat from outdoor air. WSHP use water as the heat source/sink, which is more efficient than air. GHP absorb or reject heat from underground, eliminating the need for boilers or cooling towers. The document provides details on the working, design considerations, advantages and limitations of each type.

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Heat Pumps
Prepared by
WS ATKINS - Bangalore

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Objective
 The objective of this presentation is
to give basic idea on Heat Pump
system.
 This covers the general types of Heat
Pumps and its working and design
procedure.

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Vapor compression cycle
Heat pumps use the same
vapor compression cycle
principle, but they have
additional components
that enable them to
pump heat in either
direction, such that the
same equipment unit
can provide cooling or
heating.

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 The two added components that
make heat pumps fully reversible
are:
1) A 4-way reversing valve
2) Bi directional expansion valve

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Heat Pump – General Diagram

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Types of heat pumps
 Air source heat pumps
 Water source heat pumps
 Ground source heat pumps

7. WS ATKINS (India) Pvt. Ltd.
Air Source Heat Pumps (ASHP)

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Air Source Heat Pumps-ASHP
 In ASHP, the outdoor coil rejects heat to
outdoor air when in the cooling mode and
extracts heat from outdoor air when in the
heating mode.
 Most residential applications consist of an
indoor fan-coil unit, either vertical or
horizontal, and an outdoor fan coil unit.
 The compressor is usually located in the
outdoor.
 Electrical heaters are commonly included
in the indoor unit to provide heat during
defrost cycles and during periods of high
heating demand that cannot be satisfied
by the heat pump alone.

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Working mode of Air source Heat pumps

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Selecting a Air Source Heat Pump

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Advantages & Limitations of ASHP
 Advantages
 Suitable especially in a warm climate.
 Compared to electrical heating, this may save up
to 30% of annual heating bill.
 Operating cost for summer cooling is similar to
Central air conditioning
 Limitations
 Usually electric resistance strips to further warm
the building supply air after it leaves the indoor
coil.
 Moisture in the outdoor may freeze on the out
door coil if its temp. drops below 32°F. To over
come this heat pump will periodically enter a
defrost cycle.

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Selecting a ASHP
Energy efficiency rating
The most efficient heat pumps have a HSPF
(Heating seasonal Performance factor) of
between 8 and 10 & SEER (Seasonal energy
Efficiency Ratio) of between 14 and 18.
Sizing
Over sizing causes the heat pump to start and stop
more frequently, which is less efficient and harder
on the components than letting it run for longer
cycles.

13. WS ATKINS (India) Pvt. Ltd.
Water Source Heat Pumps
(WSHP)

14. WS ATKINS (India) Pvt. Ltd.
Water Source Heat Pumps (WSHP)
 A WSHP is a single package reverse cycle heat pump that
uses water as the heat source when in the heating mode
and as the heat sink when in the cooling mode.
 Water is a much more efficient heat energy transfer
medium than air, due to its much higher specific heat.
 The water supply may be a recirculating closed loop, a well,
a lake, or a steam.
 Main components of the system
1)Compressor
2)Refrigerant to water heat exchanger
3)Refrigerant to air heat exchanger
4)Refrigerant expansion devices
5)Refrigerant reversing valve
6)Boiler and
7) cooling tower

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Working Principle
 WSHP use a boiler as a heat source during
winter and an evaporative cooling tower to
reject heat during the summer. This is
some times referred to as a boiler/tower
system.
 The water loop temperature is maintained
between 60° and 90° F. When the loop
temperature falls below 60° F boiler adds
heat and exceeds 90° F the cooling tower
rejects heat.

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Water source Heat Pump System

17. WS ATKINS (India) Pvt. Ltd.
Heating & Cooling mode of Water source
Heat Pump

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Advantages and limitations of WSHP
 Advantages
It is best applied to buildings that have simultaneous
Cooling and Heating loads.
They can accommodate simultaneous calls from zones
requiring heating and cooling.
WSHP systems generally cost less to install than central
built-up systems.
 Limitations
Requires higher maintenance costs than conventional air
side systems.
Shorter replacement life because of continuous fan and
compressor operation during heating and cooling mode.
Creates noise since the compressor and fan are commonly
located close to the zone occupant.

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Geothermal Heat Pumps (GHP)

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Geothermal (Ground Source) Heat
pumps-GSHP
 Geothermal energy is the thermal
energy within the earth’s crust.
 In GSHP heat is absorbed from or
rejected to the ground, and the
external energy needed to operate a
boiler or cooling tower is eliminated.

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GSHP-Cooling mode

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Types of Geothermal Heat pump
systems
 Closed loop systems
Ground Coupled Heat pumps (GCHP)
 Horizontal system
 Vertical system
Surface water Heat pumps (SWHP)
 Pond/lake System
 Open loop systems
 Well water heat exchanger (GWHP)

23. WS ATKINS (India) Pvt. Ltd.
Ground Coupled Heat Pumps (GCHP)
 Vertical GCPH (from ASHRAE)
Piping material: HDPE
Dia. of pipe: 0.75 to 1.5 in
Bore depth: 50 to 600 ft
Heat rate: 15 to 25 W per foot
Horizontal GCPH
Depth of trench: 4 ft
 Vertical GCPH in UK
Piping material: HDPE
Boreholes Dia.: 100mm to 150mm
Bore depth: 15m to 120m

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Bore length
 Flow rate should be sufficient to
provide a differential loop
temperature of 6 to 12° F
General equation to find bore length

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 Rearranged equation for bore length
The required length for heating
The required length for cooling

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 Where

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 Selection of Bore Length
Select bore length larger of the two lengths Lc
and Lh
If Lc > Lh select Lc. Oversized coil is beneficial
during heating season.
or select shorter Lh along with a cooling tower to
compensate for undersized coil.
If Lh > Lc select Lh. Oversized coil is beneficial in
cooling mode.
 Selection of entering temperature twi
Compromise between first cost and efficiency
Select twi to be 20 to 300 F higher than tg in
cooling and 10 to 200 F lower than tg in heating.

28. WS ATKINS (India) Pvt. Ltd.
 Advantages
 GHP’s use only 25% to 50% less electricity than
convectional heating or cooling systems.
 GHP’s can provide excellent zone space
conditioning parts of home to be heated or cooled
to different temperatures.
 GHP systems have the lowest CO2 emissions of
all technologies analyzed and the lowest overall
environmental cost.
 No need for a highly specialized chiller technician
or boiler operator.
 Less maintenance due to absence of boiler and
cooling tower.
 Highly durable piping (30 to 50 years).
 No harmful chemicals.
 No central system to fail or shut down the entire
building.

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References:
 ASHRAE Hand book, Applications,
Geothermal energy, chapter-32.
 ASHRAE Hand book, Equipments, Unitary
Air conditioners and Unitary Heat Pumps,
chapter-45.
 http://www.geo4va.vt.edu/A3/A3.htm
 Wattmaster, Heat pump design
catalog

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Thank you