• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.3
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• pp.122-129
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• 2014

In order to extract shaft power from thermal energy in a R134a Rankine cycle as waste heat recovery system of a passenger car, a scroll expander has been designed. Algebraic spiral is adopted as the base curve for scroll wrap profile in the compact scroll design. About 19% reduction in scroll diameter is accomplished when compared to the conventional involute scroll. Performance analysis on the designed scroll expander shows that the expander efficiency is 85.5% at the vehicle speed of 120 km/hr and it decreases to 67.2% at 60 km/hr, provided that the scroll clearance is kept at 10 ${\mu}m$. The expander can produce shaft power equivalent to about 13~14% of the driving power within the speed range of 60~120 km/hr.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.151-157
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• 2014

An algebraic scroll expander has been fabricated and tested in a R134a Rankine cycle with heat source of 20 kW. For the operating conditions of 20~26 bar and $90{\sim}93^{\circ}C$ at the expander inlet and 8~9 bar at the outlet, the expander produced the shaft output power of about 0.6~0.7 kW in the operating speed range of 1500~2000 rpm. These correspond to the expander efficiency of 40~45%. The volumetric efficiency increased with increasing of the expander speed, reaching to 80% at 2000 rpm. Comparing to numerical simulation results, mechanical efficiency from the test data was found to be considerably low by as much as 30%, indicating that reduction in the frictional loss should be made to improve the scroll expander efficiency.

• Journal of Educational Research in Mathematics
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• v.26 no.2
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• pp.309-331
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• 2016

Australian Curriculum Assessment and Reporting Authority(ACARA) was founded by Australian federal government in 2009. Leading under ACARA, national education curriculum development was propelled. Also from 2014 they gradually extended enforcement of new curriculum by a Reminder about new syllabus implementation (2013.01.29.). The research result of Australia's curriculum, and textbook shows that students repeat, and advance the same contents under spiral curriculum as they move to higher grade. They actively use digital technology, and also puts emphasis on practical context such as Money & financial mathematics. On the level of difficulty, or quantity aspect, Korea handles relatively advanced contents of 'number and operation' or 'Letters and Algebraic Expressions' domain than Australia. However on statistics domain, Australia not only puts more focus on practical stats than Korea, but also concerns as much on both various and qualitative terms Australia doesn't deal with formal concept of 'function'. However, they learn the wide concept of function by handling various graphs. This shows Australia has a point of similarity, and also difference to Korea on various angles.