Because thermodynamic systems are conventionally defined so that no bulk
quantities of matter are transported across their boundaries by stream flow, no energy
crosses the system boundary in the form of internal energy carried by a flowing fluid. With
the system defined in this way the only energy to cross its boundary because of the flow
process is that of work measured by the product of the pressure external to a fixed mass
system in a stream conduit and the volume change it induces in this system. In the case of
diffusion mass transport, as discussed in section 15, the system does not have a fixed mass
but the entire change associated with the diffusion mass transport is given by work
evaluated by computing the product of an external chemical potential and a specific
transported mass change within the system. As a result the combination of heat, work, and
any energy transport by non-thermodynamic carriers includes all the energy in transition
between a system and its surroundings. Energy by non-thermodynamic carriers is that
transported by radiant heat transfer, X-rays, gamma radiation, nuclear particles, cosmic
rays, sonic vibration, etc. Energy of this type is not usually considered as either heat or
work and must be evaluated separately in system where it is involved. Energy transport by
nuclear particles into a system ultimately appears as an increase in thermal energy within
the system and is important in thermodynamic applications to nuclear engineering.
In every application of thermodynamics, however, it is essential that we account for
all the energy in transition across the system boundary and it is only when this is done that
the laws of thermodynamics can relate this transported energy to changes in properties
within the system. In the processes we will discuss, heat and work together include all the
transported energy.
quantities of matter are transported across their boundaries by stream flow, no energy
crosses the system boundary in the form of internal energy carried by a flowing fluid. With
the system defined in this way the only energy to cross its boundary because of the flow
process is that of work measured by the product of the pressure external to a fixed mass
system in a stream conduit and the volume change it induces in this system. In the case of
diffusion mass transport, as discussed in section 15, the system does not have a fixed mass
but the entire change associated with the diffusion mass transport is given by work
evaluated by computing the product of an external chemical potential and a specific
transported mass change within the system. As a result the combination of heat, work, and
any energy transport by non-thermodynamic carriers includes all the energy in transition
between a system and its surroundings. Energy by non-thermodynamic carriers is that
transported by radiant heat transfer, X-rays, gamma radiation, nuclear particles, cosmic
rays, sonic vibration, etc. Energy of this type is not usually considered as either heat or
work and must be evaluated separately in system where it is involved. Energy transport by
nuclear particles into a system ultimately appears as an increase in thermal energy within
the system and is important in thermodynamic applications to nuclear engineering.
In every application of thermodynamics, however, it is essential that we account for
all the energy in transition across the system boundary and it is only when this is done that
the laws of thermodynamics can relate this transported energy to changes in properties
within the system. In the processes we will discuss, heat and work together include all the
transported energy.
No comments:
Post a Comment