2. • Why heat pump?
• Heat pump (HP) are the efficient means of serving heating and cooling.
• A underused technique in many countries.
• Major component is working medium.
• In the heating mode, heat is extracted from a natural or waste heat source
and transferred to the space.
• In cooling mode, heat is removed from space discharged to natural heat
sink.
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4. • The performance of refrigerators and heat pumps is
expressed in terms of the coefficient of performance (COP),
defined as
Notice COPR and COPHP can be greater than1.
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5. • This relation implies that COPHP >1 Since COPR is a positive
quantity.
• That is, a heat pump functions, at worst, as a resistance
heater, supplying as much energy to the house as it
consumes (i.e. 1 kWh electricity gives 1 kWh heat or cool).
• When this happens, the system normally switches to the fuel
(natural gas, propane, oil, etc.) or resistance-heating mode.
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6. There are four basic types of heat pumps:
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– air-to-air
– water-to-air
– water-to-water and
– earth-to air.
7. In air-to-air heat pump (ASHP)
– Heat is removed from indoor air and rejected to the outdoor
air of a building during cooling cycle.
– Reverse happens during heating (heat pump mode).
Water to air heat pump (WHP)
– Water replaces outdoor air as heat source or sink, depending
on heating or cooling mode.
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8. Geothermal heat pump (GHP)
– Use energy from ground soil or ground water as source or sink.
– In winter, heat pump transfers thermal energy from the ground to provide space
heating.
– In the summer the energy transfer process is reversed.
– GHP benefits from nearly constant ground temperature year round, which is higher
than winter air temperatures and lower than summer air temperatures.
– The energy efficiency of a GHP is higher than ASHP and even more than fossil fuel
furnace heating.
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9. • The primary difference between ASHP and
GHP is the investment in ground loop
• Cost-effectiveness of GHP depends upon
annual energy cost savings whether are high
enough for the extra cost of the ground loop.
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10. Solar-Assisted Heat Pump
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• A solar collector can improve the performance of liquid or air
system
• But it adds expenses.
• Low-temperature solar heat applied to one side of the heat-
pump system evaporates the low-pressure refrigerant liquid.
• The compressor then raises the pressure and temperature of
the vapour which, when it condenses, gives off heat at a higher
temperature than that at which heat was provided.
Solar-Driven Refrigeration Systems
– Ejector refrigeration system
– Vapour compression refrigeration system
