3B SCIENTIFIC PHYSICS G U10050 Instrucciones De Uso página 6

3. Technical data
Motor-generator unit:
2-stage pulley:
Working piston:
Path of working piston:
Volumetric change:
Minimum volume:
Maximum volume:
Power of the Stirling motor:
Dimensions:
Weight:
4. Functioning principle
An ideal Stirling cycle has 4 phases (refer to Fig. 1):
Phase 1: Isothermal change of state, during which
the air expands at constant temperature.
Phase 2: Isochoric change of state, during which the
air cools at constant volume in the regene-
rator.
Phase 3: Isothermal change of state, during which
the air is compressed at constant tempera-
ture.
Phase 4: Isochoric change of state, during which the
air in the regenerator is heated back to its
initial temperature.
The process that takes place in the Stirling engine
only approximates to such an ideal cycle because in
fact the four phases overlap. Gas changes from hot to
cold while the expansion is still taking place and not
all the air will yet be in the colder part of the engine
while the compression phase is occurring.
Fig. 1 Functioning principle
(A: Displacement piston, B: Working piston)
max. 12 V DC
30 mm dia., 19 mm dia.
25 mm dia.
24 mm
⎛ ⎞
25 mm
⋅ π =
24 mm
⎜ ⎟ 12 cm
⎝ ⎠
2
32 cm³
44 cm³
1 W approx.
300x220x160 mm³ approx.
1.65 kg approx.
5.1 The Stirling Engine as a heat engine
•
Fill the methylated-spirit burner, place it in the
recess in the base-plate, twist out about 1-2 mm
of the wick, and ignite it.
•
Move the displacer piston to its farthest-back
3 position, and after a short heating-up time
(about 1-2 minutes) push the flywheel gently in
the clockwise direction (as seen from the motor-
generator unit) to set it turning (see Fig. 2).
•
If necessary, adjust the tension of the drive belt
by moving the motor-generator unit.
•
Turn on the filament lamp by moving the switch
to the "up" position.
•
Alternatively, connect an external load through
the 4 mm sockets and drive it by moving the
switch to the "down" position.
Speed without a load:
Speed with a generator as the load: 650 rpm approx.
Generator voltage:
Pressure difference:
5.2 The Stirling motor as a heat pump or refrig-
erator
Additional instruments needed:
DC Power supply 15 V, 1.5 A
or
DC Power supply 15 V, 1.5 A
Digital thermometer
•
Insert temperature sensors into the thermome-
ter sockets and connect them to a measuring in-
strument (see fig. 3).
•
Connect a DC voltage source through the 4 mm
sockets.
•
Adjust the voltage (maximum 12 V) and operate
the Stirling engine with the switch in the "down"
position.
•
Observe the increase or reduction in tempera-
ture.
In the refrigerator mode of operation, the flywheeI
rotates in the clockwise direction (as seen from the
motor-generator unit), whereas in the heat pump
mode it rotates in the anticlockwise direction.
•
To switch between the two modes of operation,
reverse the polarity of the connections.
Pressure difference:
Motor voltage:
Speed:
Temperature difference (with respect to 21° C):
Refrigerator:
Heat pump:
2
5. Operation
1000 rpm approx.
6 V DC approx.
+250 hPa / -150 hPa
U8521121-230
U8521121-115
+250 hPa / -150 hPa
-4 K (reservoir: +6 K)
+13 K (reservoir: -1 K)
U11818
9 V
600 rpm