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Thermal System Design
ME 200 Thermal/Fluids Engineering
Unless otherwise noted, figures are from Stoecker, W.F., Design of Thermal Systems, 3rd 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 non-
participantsOmni, 1980
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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
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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
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Aircraft Development Cycle
Engineering Design Flow Diagram
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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 watervs.
?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
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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!
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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
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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
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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
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.
? ? ? ?? ?? ?3 2? P elevation rise =?gZ= 1000 kg/m 9.81 m/s 8 m 78.5 kPa?
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?Pump first cost (increases with ? P)?Piping first cost (decreases with ? P)?Operating cost (increases with ? P)
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Optimum System
