hajdu HP-TOWER HPT200 Manuel De Mise En Service, D'opération Et D'entretien page 73

2 – first heat exchanger located in the water tank
of the water heater: heat exchange between
the cooling fluid and the sanitary water to be
heated up takes place along its surface. As in
this phase, the physical state of the warm coo-
ling gas changes and it condenses into liquid
form, while transferring its heat to the water,
this heat exchanger is defined as condenser.
3 – expansion valve: a device which lets the coo-
ling fluid pass through itself, as soon as its
pressure and temperature decrease, there-
by perceivably following the expansion of the
liquid as a result of the increase of the pipe
cross-section above the valve.
4 – second heat exchanger located in the up-
per part of the water heater with its sur-
face increased by the addition of fins. The se-
cond heat exchanger performs heat exchange
between the cooling fluid and the free source
or the environmental air drifted artificially by a
special fan in the proper way. As in this phase,
the cooling fluid evaporates and extracts heat
from the environmental air, this heat exchan-
ger is defined as an evaporator.
As heat energy is able to flow from a higher tem-
perature level to a lower temperature level exclusi-
vely, the temperature of the cooling agent located
in the evaporator (4) has to be lower than the environmental air acting as free source,
and at the same time, in order to transfer heat, the temperature of the cooling agent
located in the condenser (2) has to be higher than the water to be heated in the tank.
The temperature difference within the heat pump circuit is produced by the compres-
sor (1) and the expansion valve (3) located between the evaporator (4) and the conden-
ser (2), due to physical characteristics of the cooling fluid.
The efficiency of the heat pump circuit is measured by the coefficient of performance
(COP). COP is the ratio of energy received by the appliance (in this case, the heat trans-
ferred to the water to be heated) and the electric power used (by the compressor and
the supporting equipment of the appliance). The COP may change, subject to the type
of the heat pump and the applicable operational conditions. Example: A value of 3 for
COP means that the heat pump transfers 3 kWh heat to the material to be heated after
every 1 kWh electricity used, from which 2 kWh is extracted from the free source. The
rated COP values of the HPT200(C) heat pump water heater are listed in table 1.1.-1
containing the technical specifications.
In relation with characteristics of typical heat pump cycle temperatures, the cooling
Figure 3.2.-1.
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