Thermal System Design Pdf

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

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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 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

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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 ?

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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

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Optimum System

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