Civil Engineering Reference
In-Depth Information
(b)
In solving every problem, be it of design or business, there are two approa-
ches, namely closed-ended approach and open-ended approach.
Closed-ended approach means that all the appropriate entries needed are
usually given and the results are generally unique and well-de
ned, so that the
solution to the given problem may be carried out to completion, thus obtaining
the
es the provided inputs and requirements.
Open-ended approach means that the entries may be vague or incomplete,
making it necessary to seek additional information or to accept approximations
and assumptions. Also, the results are not well-known or well-de
final result that satis
ned at the
beginning. A unique solution is generally not obtained and one may have to
choose from a range of acceptable solutions. In addition, a solution that sat-
is
es all the requirements may not be obtained, and it may be necessary to
relax some of the requirements to obtain an acceptable solution. Therefore, the
trade-offs generally form a necessary part of the solving process, and indi-
vidual judgment based on available information is needed to decide on the
final solution.
For both problems of design and business, the open-ended approach is
more frequent than closed-ended.
(c)
It is crucial to optimize the designed system or process, so that a chosen
quantity, known as the objective function, is maximized or minimized.
In a mCCHP system, it is necessary to seek an optimal design that will, for
instance, consume the least amount of energy per unit. This measure is closely
linked with the overall ef
ciency. In addition, by reducing the energy con-
sumed for removing a unit of thermal energy, a unique system is not obtained
and the design may vary over wide ranges, given in terms of the hardware as
well as the operating conditions. All these designs may be termed as
acceptable or workable because they satisfy the given requirements and
constraints. But only one of them is considered as optimal.
(d) Design process starts with a basic concept, and continues with modeling and
evaluating different alternatives, for selecting a
final one that meets the
requirements and constraints.
Before going into production, the system may be tested by carrying out a pro-
totype. This way, the design is directed at creating a new process or system.
In recent years, we have seen a tremendous growth in the development and use
of thermal systems in which
flow and transport of energy play a dominant role.
These systems arise in many diverse engineering
fluid
fields such as those related to
manufacturing, power generation, pollution, air conditioning. The survival and
growth of most industries today are strongly dependent on the design and opti-
mization of the relevant systems. It has become important to apply design and
optimization methods that traditionally have been applied to thermal systems and
processes. The design process must consider many arrangements and determine the
relevant characteristic parameters for all cases.
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