Thermal System Design
ME 200
Thermal/Fluids
Engineering
Unless otherwise noted, figures are from Stoecker, W.F., Design of
Thermal Systems, 3 rd edition, McGraw-Hill, Inc., 1989.
Stages of a Project
? Enthusiasm
? Disillusionment
? Panic
? Search
for the guilty party
? Punishment of the innocent party
? Fame and honor for the nonparticipants
Omni, 1980
1
What is Design?
? ABET:
“The process of devising a system, component,
or process to meet desired needs. It is a
decision-making process (often iterative), in
which the basic sciences, mathematics, and
engineering sciences are applied to convert
resources optimally to meet a stated objective.”
Thermal-Fluids Design
Design associated with principles of
thermodynamics, heat transfer, and fluid
mechanics
? Hardware: fans, pumps, compressors,
engines, heat exchangers, turbines,
reactors, pipes
? Systems: power generation, refrigeration,
air conditioning, electronics cooling, fluids
transport, and food, chemical, and
process industries
?
2
Basic Course Topics
? Analysis,
selection, and modeling of
thermal/fluid equipment
? System simulation
? System optimization
? Basics of economics
? Optimization using exergy
Some ME 200 applications
? Fluids:
design and modeling of
piping networks
? Thermodynamics: modeling and
optimization of a refrigeration
system
? Heat Transfer:
design/modeling/optimization of an
electronic module cooling system
3
Aircraft Development Cycle
Engineering Design
Flow Diagram
4
Need/Opportunity
? Make
sure that this statement
describes the need, not a possible
solution.
? For example:
? City
officials want to enlarge a reservoir
to store larger quantities of water
vs.
? City officials need more water during
certain times of the year
Probability of Success
?
?
Need to choose success criteria
For example, a 10% rate of ROI for a 5-year plant life
5
Market Analysis
?
Higher volume means lower price because cost
is lower (usually) in a large plant
Technical Design
? This
is what we’re focusing on in this
class!
6
Feasibility
? Is
the project even possible?
Infeasibility can be caused by
? Lack
of investment capital
? Lack of land or labor
? Unfavorable zoning regulations
? Safety codes or other laws
?A
project may be feasible but
uneconomical.
Research and Development
? This
may occur in many phases of
design.
? It
could be the source of the idea.
? It may be involved in the first technical
design iteration or in later iterations as
new designs are chosen or the original
one is improved
7
Other important factors
? Relevant
codes, standards, laws
? Interference with other systems
? Liability – written documentation of
everything is important!
? Environmental concerns
? Safety and reliability
? Disposal/recycling
What constitutes a workable system?
?A
workable system
? Meets
system requirements, such as
maintaining a refrigeration room at the
required temperature
? Has acceptable life an maintenance
costs
? Abides by constraints such as size,
noise, pollution, effects on other
systems
8
Workable vs. Optimum System Example
?
?
Pump and piping must be selected to convey 3
kg/s of water over distance of 250 m and an
elevation rise of 8 m.
To design a workable system
? P ?elevation rise ?=?gZ= ?1000 kg/m 3 ??9.81 m/s 2 ??8 m ? ? 78.5 kPa
Estimate a 100 kPa pressure drop due to pipe friction.
Pick a pump that meets this 179 kPa pressure drop while
delivering 3 kg/s.
Choose a pipe size that results in 100 kPa pressure drop or
less over a 250 m length. A 2-in pipe meets this
specification.
?
But will this be the optimum system? Probably
not.
Optimum System
? Optimize
life-cycle cost.
? Assume that installation and
maintenance costs are the same for
all cases and thus can be ignored.
? Three main costs
first cost (increases with ? P)
? Piping first cost (decreases with ? P)
? Operating cost (increases with ? P)
? Pump
9
Optimum System
10