MEEN 315, SECTION 503
PRINCIPLES OF THERMODYNAMICS
Homework #1 Solutions
DUE September 8, 2009
Suppose you insert a capped bottle of soda (originally at 20° C) into a refrigerator at 3° C. If you make
the contents of the soda bottle your control system, are the contents a control volume or a control mass?
Does the system soda undergo a process? Does it undergo a cycle? Is the system open or closed? What
is the control system’s surroundings? Does anything cross the control surface? Is the control system
isolated? Suppose you were told the system underwent a “quasi-equilibrium process”; describe what that
would mean to the properties of the control system.
The control system is a closed system since mass does not transfer into or out of the control volume. This makes
it a control mass.
Yes, the soda bottle undergoes a cooling process as its temperature comes into equilibrium with the refrigerator
No, the soda bottle does not undergo a cycle, as it is not returned to an initial state.
The system is closed.
The control system’s surrounding is the refrigerator space.
Yes, heat energy crosses the control surface.
No, the control system is not isolated, since energy is transferred with the surroundings in the form of heat
If the system were to undergo a quasi-equilibrium process, that implies the process occurs slowly enough that
the properties of the system are uniform at each instant in time. There would be no spatial variations in
Identify the properties in the following list, provide the standard metric and English units, and state if
each is intensive, extensive, or not a property: P, F, V,
, T, m, L, t, and
P – Pressure, [kPa], [psi], intensive.
F – Force, [N], [lbf], not a property.
V – Volume, [m