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The article describes an activity program which asks students to establish planetary categories through conclusions drawn from an analysis of planetary data.

The article focuses on the effectiveness of a guided walk through a scale model of the solar system in Henry Ford Community College (HFCC) in Dearborn, Michigan. The authors say that guided walk through the model for instruction of the relative scales of sizes and distances in the solar system shows actual student participation as compared to lectures. They add that those students who joined the walk gain the highest percentage of correct responses to each item on the given test.

Among the critical elements of a thermoacoustic device are its internal heat exchangers. This work quantifies the behavior of actual heat exchangers in situ in an operating thermoacoustic refrigerator. Each heat exchanger consisted of a specified arrangement of metal in contact both with oscillating gas adjacent to a thermoacoustic stack and also with water bearing tubes. Measured quantities were the temperature Ts of the adjacent end of the stack, the temperature Tw of the water flowing through the tubes, the change of water temperature δT between tube inlet and outlet, and the water flow rate. The heat-transfer rate Q was determined from the latter two quantities. The overall heat-transfer conductance G, defined by G=Q/(Ts-Tw), is determined by three quantities: the gas-to-metal temperature drop, the fin efficiency, and the metal-to-water temperature drop. Raw experimental results will be presented for several gas-side heat-exchanger geometries, including copper screen, reticulated aluminum foam, and bundled copper tubes. Where possible, comparisons will be made to simple theoretical expectations. [ABSTRACT FROM AUTHOR]

A thermoacoustic refrigerator was built to explore scaling to large heat flux. The refrigerator was constructed according to a modular design so that various stack, heat exchanger, and resonator sections are easily interchangeable. The resonator is driven by a commercial 10-in. woofer. Initial tests, using pure helium gas as the working fluid and steel honeycomb (0.8-mm cell) for the stack, pumped 60 W of heat against a 10 °C temperature gradient. Measurements of heat flux and efficiency will be reported as functions of stack structure (e.g., pore size and shape) and will be compared with theoretical predictions. [ABSTRACT FROM AUTHOR]