Webster University Operations And Supply Chain Management Assignment Help - the engineer

Question - In analyzing the performance of a thermal system, the engineer must be able to identify the relevant
heat transfer processes. Only then can the system behavior be properly quantified. For the following
systems identify the pertinent processes, designating them by appropriately labeled arrows on a
sketch of the system. Answer additional questions that appear in the problem statement.
(a) Identify the heat transfer processes that determine the temperature of an asphalt pavement on a
summer day. Write an energy balance for the surface of the pavement.
(b) Microwave radiation is known to be transmitted by plastics, glass, and ceramics, but to be
absorbed by materials having polar molecules such as water. Water molecules exposed to micr ...Read More owave
radiation align and reverse alignment with the microwave radiation at frequencies up to 10 9 S -I,
causing heat to be generated. Contrast cooking in a microwave oven with cooking in a conventional
radiant or convection oven. In each case what is the physical mechanism responsible for heating the
food? W hich oven has the greater energy utilization efficiency? Why? Microwave heating is being
considered for drying clothes. How would operation of a microwave clothes dryer differ from a
conventional dryer? W hich is likely to have the greater energy utilization efficiency and why?
(d) Consider an incandescent light source that consists of a tungsten filament enclosed in a gas-filled
glass bulb. Assuming steady-state operation with the filament at a temperature of approximately 2900
K, list all the pertinent heat transfer processes for (i) the filament and (ii) the glass bulb.
(e) There is considerable interest in developing building materials that have improved insulating
qualities. The development of such materials would do much to enhance energy conservation by
reducing space heating requirements. It has been suggested that superior structural and insulating
qualities could be obtained by using the composite shown. The material consists of a honeycomb,
with cells of square cross section, sandwiched between solid slabs. The cells are filled with air, and
the slabs, as well as the honeycomb matrix, are fabricated from plastics of low thermal conductivity.
For heat transfer normal to the slabs, identify all heat transfer processes pertinent to the performance
of the composite. Suggest ways in which this performance could be enhanced.
(f) A thermocouple junction (bead) is used to measure the temperature of a hot gas stream flowing
through a channel by inserting the junction into the mainstream of the gas. The surface of the channel
is cooled such that its temperature is well below that of the gas. Identify the heat transfer processes
associated with the junction surface. Will the junction sense a temperature that is less than, equal to,
or greater than the gas temperature? A radiation shield is a small, open-ended tube that encloses the
thermocouple junction, yet allows for passage of the gas through the tube. How does use of such a
shield improve the accuracy of the temperature measurement?
(g) A double-glazed, glass fire screen is inserted between a wood-burning fireplace and the interior of
a room. The screen consists of two vertical glass plates that are separated by a space through which
room air may flow (the space is open at the top and bottom). Identify the heat transfer processes
associated with the fire screen. ...Read Less

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