THERMODYNAMICS CONCEPT AND BASIC INFORMATION


1-15C The radiator should be analyzed as an open system since mass is crossing the boundaries of the system.

1-16C A can of soft drink should be analyzed as a closed system since no mass is crossing the boundaries
of the system.

1-17C Intensive properties do not depend on the size (extent) of the system but extensive properties do.

1-18C For a system to be in thermodynamic equilibrium, the temperature has to be the same throughout
but the pressure does not. However, there should be no unbalanced pressure forces present. The increasing
pressure with depth in a fluid, for example, should be balanced by increasing weight.

1-19C A process during which a system remains almost in equilibrium at all times is called a quasiequilibrium
process. Many engineering processes can be approximated as being quasi-equilibrium. The
work output of a device is maximum and the work input to a device is minimum when quasi-equilibrium
processes are used instead of nonquasi-equilibrium processes.

1-20C A process during which the temperature remains constant is called isothermal; a process during
which the pressure remains constant is called isobaric; and a process during which the volume remains
constant is called isochoric.

1-21C The state of a simple compressible system is completely specified by two independent, intensive
properties.

1-22C Yes, because temperature and pressure are two independent properties and the air in an isolated
room is a simple compressible system.

1-23C A process is said to be steady-flow if it involves no changes with time anywhere within the system
or at the system boundaries.

1-24C The specific gravity, or relative density, and is defined as the ratio of the density of a substance to
the density of some standard substance at a specified temperature (usually water at 4°C, for which ρH2O =
1000 kg/m3). That is, SG = ρ / ρ H2O . When specific gravity is known, density is determined from
ρ = SG×ρ H2O .

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