PASCO TD-8564 THERMAL EFFICIENCY APPARATUS - Manual (Page 11)

012-05443A Thermal Efficiency Apparatus
7
to the hot reservoir when no load is present. Since, while
there is no load, the hot reservoir is maintained at an
equilibrium temperature, the heat put into the hot reser-
voir by the heating resistor must equal the heat radiated
and conducted away from the hot reservoir. So measuring
the heat input when there is no load determines the heat
loss due to radiation and conduction. It is assumed this
loss is the same when there is a load and the heat engine
is operating.
Heat Pumped from the Cold Reservoir
When the Thermal Efficiency Apparatus is operated as a
heat pump, conservation of energy yields that the rate at
which heat is pumped from the cold reservoir, P
C
, is equal
to the rate at which heat is delivered to the hot reservoir,
P
H
, minus the rate at which work is being done, P
W
(Figure 3).
Figure 7: No Load
The work can be measured directly but the heat delivered
to the hot reservoir has to be measured indirectly. Notice
that when the heat pump is operating, the temperature of
the hot reservoir remains constant. Therefore, the hot
reservoir must be in equilibrium and the heat delivered to
it must equal the heat being conducted and radiated away.
So a measurement of the heat conducted and radiated
away at a given temperature difference will also be a
measurement of the heat delivered to the hot reservoir.
The heat conducted and radiated is measured by running
the device with no load and measuring the heat input
needed to maintain the temperature of the hot side
(Figure 7).
Ω
Power
Supply
T
C
T
H
Conducted
Power
P
H
(open)
V
V
A
Conducted
Power
T
H
T
C
P
W
Engine
Power
Supply
V
A
V
Ω
Figure 6: Heat Engine With A Load