Idiomas disponibles
Idiomas disponibles
At equal time intervals, note the operating
time, power consumption and water temper-
atures.
Abort the measurement, at approx. 10°C in
the left reservoir
From the measured values, an overall efficiency
can be calculated for the course of the experi-
ment and a partial efficiency for each time inter-
val.
Q
c
m
2
η
co
P
t
P
c = specific heat capacity of water and
m = mass of water
8.2 Mollier diagram
An ideal cycle can be represented by a Mollier
diagram by measuring pressures p(3) and p(4)
before and after the expansion valve and the tem-
perature T(1) before the compressor:
T(1) and p(4) determine point 1 of the Mollier di-
agram (see Fig. 5). The intersection of the corre-
sponding isentropes with the horizontal line p(3)
= constant defines point 2. The intersection of the
horizontal with the line representing the boiling
point gives point 3, then a perpendicular down to
the horizontal p(4) = const. provides point 4.
Additionally, measuring temperatures T(2), T(3)
and T(4) provides an extra insight into the pro-
cesses taking place inside the heat pump:
The temperature T(4) measured externally is in
agreement with the overall temperature read from
the temperature scales of the corresponding ma-
nometer to within the precision of the equipment.
This temperature scale is based on the curve rep-
resenting work done by the refrigerant. The meas-
urement therefore shows that the refrigerant be-
yond the expansion valve is in a mixture of liquid
and gaseous states.
The externally measured temperature T(3), how-
ever, differs from the temperature read from the
manometer on the high-pressure side. The refrig-
erant at this point contains no gas content. It is
entirely liquid.
The following equipment is recommended for tak-
ing external measurements (see section 4. ac-
cessories):
Temperature sensor NTC
with measurement terminal
VinciLab
Coach 7 License
8.3 Theoretical efficiency
The theoretical efficiency of the ideal cycle can
be calculated from specific enthalpies h
T
2
t
1021797
1021477
, h
1
2
h
, which can be read directly from the Mollier di-
3
agram:
q
h
2
th
w
8.4 Mass flow rate of refrigerant
Once the enthalpies h
are known as well as the amount of heat ΔQ
plied to the water reservoir in a time interval Δt,
then it is possible to estimate the mass flow rate
of the refrigerant.
m
Q
2
t
t
h
Fig. 6
Energy monitor
The following values can be read on the display
of the energy meter:
Electrical voltage
Electrical current
Electrical power
Electrical energy
To reset the electrical energy to zero, press the
small button to the right of the display with a
pointed object as follows:
Hold it for about 4 seconds until the electrical
energy value flashes, then press it again
briefly.
The display can be tilted to make it easier to read.
Mollier diagrams for a refrigerant are often use to
demonstrate the operating cycle for a compres-
sion heat pump. They plot the pressure p against
the specific enthalpy h for the refrigerant (en-
thalpy is a measure of heat content in the refrig-
erant and always increases with increasing pres-
sure and gas content).
and
6
h
2
3
h
h
2
1
and h
for the ideal cycle
2
3
1
h
2
3
9. Energy monitor
Unit: Volt
Unit: Ampere
Unit: Watt
Unit: watt-hour
10. Mollier diagram
sup-
2
