DESIGN & OPEN-ENDED PROBLEMS
1. An advertisement describes a portable heater claimed to cut home heating bills by up to 50%. The heater is said to be able to heat large rooms in minutes without having a high outer-surface temperature, reducing humidity and oxygen levels, or producing carbon monoxide. A typical deployment is shown in Fig. P2.10D. The heater is an enclosure containing electrically-powered quartz infrared lamps that shine on copper tubes. Air drawn into the enclosure by a fan flows over the tubes and then is directed back into the living space. According to the advertisement, a heater capable of heating a room with up to 300 ft2 of floor area costs about $400 while one for a room with up to 1000 ft2 of floor area costs about $500. Critically evaluate the technical and economic merit of such heaters. Write a report including at least three references.
2. An inventor proposes borrowing water from municipal water mains and storing it temporarily in a tank on the premises of a dwelling equipped with a heat pump. As shown in Fig. P2.11D, the stored water serves as the cold body for the heat pump and the dwelling itself serves as the hot body. To maintain the cold body temperature within a proper operating range, water is drawn from the mains periodically and an equal amount of water is returned to the mains. As the invention requires no net water from the mains, the inventor maintains that nothing should be paid for water usage. The inventor also maintains that this approach not only gives a coefficient of performance superior to those of air-source heat pumps but also avoids the installation costs associated with ground-source heat pumps. In all, significant cost savings result, the inventor says. Critically evaluate the inventor's claims. Write a report including at least three references.
3. Due to their zero ozone depletion and low global warming potential natural refrigerants are actively under consideration for commercial refrigeration applications (see box in Sec.3.4). Investigate the viability of natural refrigerants in systems to improve human comfort and safeguard food. Consider performance benefits, safety, and cost. On the basis of your study, recommend especially promising natural refrigerants and areas of application where each is particularly well suited. Report your findings in a PowerPoint presentation.
4. Some oil and gas companies use hydraulic fracturing to access oil and natural gas trapped in deep rock formations. Investigate the process of hydraulic fracturing, its benefits, and environmental impacts. On this basis, write a three-page brief for submission to a congressional committee considering whether hydraulic fracturing should continue to be exempt from regulation under the Safe Drinking Water Act. The brief can provide either objective technical background to inform committee members or take a position in favor of, or against, continuing the exemption.
5. Passive solar heating may become more effective in coming years through incorporating phase-change materials (PCMs) into building materials. Investigate incorporation of phase-change materials into products used by the building industry to enhance passive solar heating. For each product, determine the PCM type, melting point, and accompanying phase-change enthalpy. Discuss how the PCM affects performance of the building material and how this benefits space heating. Prepare a 25-minute PowerPoint presentation suitable for a high school chemistry class based on your findings. Include at least two instructional aides to enhance your presentation.
6. Generation of electricity by harnessing currents, waves, and tides is being studied across the globe. Electricity can be generated from currents using underwater turbines, as illustrated in Fig. P4.4D. Electricity also can be generated from the undulating motion of waves using tethered buoys. Like means can be used to generate power from tidal movements. Although currents and waves have long been used to meet relatively modest power needs, many observers today are thinking of large-scale power generation systems. Some see the oceans as providing a nearly unlimited renewable source of power. For a site in China coastal waters, estuaries, or rivers, critically evaluate the viability of currents and/or waves for large-scale power generation by 2025. Consider technical and economic factors and effects on the ecosystem. Write a report including at least three references.
7. For a refrigerator in your home, dormitory, or workplace, use a plug-in appliance load tester (Fig. P5.4D) to determine the appliance's power requirements, in kW. Estimate annual electrical usage for the refrigerator, in kW ? h. Compare your estimate of annual electricity use with that for the same or a similar refrigerator posted on the ENERGY STAR® website. Rationalize any significant discrepancy between these values. Prepare a poster presentation detailing your methodologies and findings.
8. Over the years, claimed perpetual motion machines have been rejected because they violate physical laws, primarily the first or second laws of thermodynamics, or both. Yet, while skepticism is deeply ingrained about perpetual motion, the ATMOS clock is said to enjoy a nearly unlimited operational service life, and advertisements characterize it as a perpetual motion clock. Investigate how the ATMOS operates. Provide a complete explanation of its operation, including sketches and references to the first and second laws, as appropriate. Clearly establish whether the ATMOS can justifiably be called a perpetual motion machine, closely approximates one, or only appears to be one. Prepare a memorandum summarizing your findings.
9. A technical article considers hurricanes as an example of a natural Carnot engine: K. A. Emmanuel, "Toward a General Theory of Hurricanes," American Scientist, 76, 371-379, 1988. Also see Physics Today, 59, No. 8, 74-75, 2006, for a related discussion by this author. U.S. Patent (No. 4,885,913) is said to have been inspired by such an analysis. Does the concept have scientific merit? Engineering merit? Summarize your conclusions in a memorandum.
10. Ocean thermal energy conversion (OTEC) power plants generate electricity on ships or platforms at sea by exploiting the naturally occurring decrease of the temperature of ocean water with depth. One proposal for the use of OTECgenerated electricity is to produce and commercialize ammonia in three steps: Hydrogen (H2) would first be obtained by electrolysis of desalted sea water. The hydrogen then would be reacted with nitrogen (N2) from the atmosphere to obtain ammonia (NH3).
Finally, liquid ammonia would be shipped to shore, where it would bereprocessed into hydrogen or used as a feedstock. Some say a major drawback with the proposal is whether current technology can be integrated to provide cost-competitive end products. Investigate this issue and summarize your findings in a report with at least three references.
11. The maximum entropy method is widely used in the field of astronomical data analysis. Over the last three decades, considerable work has been done using the method for data filtering and removing features in an image that are caused by the telescope itself rather than from light coming from the sky (called deconvolution). To further such aims, refinements of the method have evolved over the years. Investigate the maximum entropy method as it is used today in astronomy, and summarize the state-of-the-art in a memorandum.
12 In recent decades, many have written about the relationship between life in the biosphere and the second law of thermodynamics. Among these are Nobel Prize winners Erwin Schrodinger (Physics, 1933) and Ilya Prigogine (Chemistry, 1977). Contemporary observers such as Eric Schneider also have weighed in. Survey and critically evaluate such contributions to the literature. Summarize your conclusions in a report having at least three references.
13 Elementary thermodynamic modeling, including the use of the temperature-entropy diagram for water and a form of the Bernoulli equation has been employed to study certain types of volcanic eruptions. (See L. G. Mastin, "Thermodynamics of Gas and Steam-Blast Eruptions," Bull. Volcanol., 57, 85-98, 1995.) Write a report critically evaluating the underlying assumptions and application of thermodynamic principles, as reported in the article. Include at least three references.
14 Consider the feasibility of using biomass to fuel a 200-MW electric power plant in a rural area in your locale. Analyze the advantages and disadvantages of biomass in comparison with coal and natural gas. Include in your analysis material handling issues, plant operations, environmental considerations, and costs. Prepare a PowerPoint presentation of your recommendations.
15 Silicon is one of earth's most abundant elements. Yet demand for the pricey high-purity form of silicon required to make solar cells has risen with the growth of the solarphotovoltaic industry. This, together with limitations of the energy-intensive technology customarily used to produce solargrade silicon, has led many to think about the development of improved technologies for producing solar-grade silicon and using materials other than silicon for solar cells. Investigate means for producing solar cells using silicon, including conventional and improved methods, and for producing cells using other materials. Compare and critically evaluate all methods discovered based on energy use, environmental impact, and cost. Prepare a poster presentation of your findings.
16 The Annual Energy Outlook with Projections report released by the U.S. Energy Information Administration projects annual consumption estimates for various fuel types through the next 25 years. According to the report, biofuels will play an increasing role in the liquid fuel supply over that time period. Based on technologies commercially available or reasonably expected to become available in the next decade, identify the most viable options for producing biofuels. Compare several options based on energy return on energy invested (EROEI), water and land requirements, and effects on global climate change. Draw conclusions based on your study, and present your findings in a report with at least three references.
17 Investigate the following technologies: plug-in hybrid vehicles, all-electric vehicles, hydrogen fuel cell vehicles, diesel-powered vehicles, natural gas-fueled vehicles, and ethanol-fueled vehicles, and make recommendations on which of these technologies should receive national research, development, and deployment support over the next decade. Base your recommendation on the result of a decision matrix method such as the Pugh method to compare the various technologies. Clearly identify and justify the criteria used for the comparison and the logic behind the scoring process. Prepare a 15-minute briefing and an executive summary suitable for a conference with your local government.
18 High-performance aircraft increasingly feature electronics that assist flight crews in performing their duties and reducing their fatigue. While these electronic devices improve aircraft performance, they also add greatly to the thermal load that must be managed within the aircraft. Cooling technologies currently used on aircraft are approaching their limits and other means are being considered, including vapor-compression refrigeration systems. However, unlike cooling systems used on earth, systems employed on aircraft must meet rapidly changing conditions. For instance, as onboard electronic devices switch on and off, the energy they emit by heat transfer alters the thermal load; additionally, the temperature of the air outside the aircraft into which such waste heat is discarded changes with altitude and flight speed.
Accordingly, for vapor-compression systems to be practical for aircraft use, engineers must determine if the systems can quickly adapt to rapidly changing thermal loads and temperatures. The object of this project is to develop the preliminary design of a bench-top laboratory set-up with which to evaluate the performance of a vapor-compression refrigeration system subject to broadly variable thermal inputs and changing ambient conditions. Document your design in a report having at least three references.