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Unformatted text preview: Chapter 2 Basic Concepts of Thermodynamics Chapter 2 BASIC CONCEPTS OF THERMODYNAMICS Systems and Properties 2-1C The radiator should be analyzed as an open system since mass is crossing the boundaries of the system. 2-2C A can of soft drink should be analyzed as a closed system since no mass is crossing the boundaries of the system. 2-3C Intensive properties do not depend on the size (extent) of the system but extensive properties do. State, Process, Forms of Energy 2-4C In electric heaters, electrical energy is converted to sensible internal energy. 2-5C The forms of energy involved are electrical energy and sensible internal energy. Electrical energy is converted to sensible internal energy, which is transferred to the water as heat. 2-6C The macroscopic forms of energy are those a system possesses as a whole with respect to some outside reference frame. The microscopic forms of energy, on the other hand, are those related to the molecular structure of a system and the degree of the molecular activity, and are independent of outside reference frames. 2-7C The sum of all forms of the energy a system possesses is called total energy . In the absence of magnetic, electrical and surface tension effects, the total energy of a system consists of the kinetic, potential, and internal energies. 2-8C The internal energy of a system is made up of sensible, latent, chemical and nuclear energies. The sensible internal energy is due to translational, rotational, and vibrational effects. 2-9C Thermal energy is the sensible and latent forms of internal energy, and it is referred to as heat in daily life. 2-10C 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. 2-11C A process during which a system remains almost in equilibrium at all times is called a quasi- equilibrium 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. 2-12C 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. 2-13C The state of a simple compressible system is completely specified by two independent, intensive properties. 2-14C Yes, because temperature and pressure are two independent properties and the air in an isolated room is a simple compressible system....
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- Spring '08