MAE 334
Lab 3
If the apparatus were perfectly insulated, all of the mechanical work would go into
heating the cylinder. Actually, some heat is continually lost to the surroundings. If P is
the rate of mechanical work (in Watts) and Q is the rate of heat loss to the surroundings
(also in Watts), the calorimeter gains energy at a rate:
(1)
Q
P
dt
dE
−
=
For the calorimeter, the relationship between energy gain and temperature rise is
proportional to its thermal capacity:
dt
dT
cm
dt
dE
cal
=
(2)
Here, the thermal capacity in Joules per degree Celsius (J/C) is the product of the specific
heat of aluminum (
) and the mass of the calorimeter (
). Also, the heat loss to the
surroundings is proportional to the temperature difference between the cylinder and the
laboratory surroundings:
c
cal
m
(3)
)
(
lab
T
T
H
Q
−
=
where the overall convection factor H in Watts per degree Celsius (W/C) is the product of
the convective heat transfer coefficient (h) and the surface area of the calorimeter (A).
Thus,
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '09
 Heat, dt dt, calorimeter gains energy

Click to edit the document details