On the Holway-Weiss debate: Convergence of the Grad-moment-expansion in kinetic gas theory

Zhenning Cai; Manuel Torrilhon

doi:10.1063/1.5127114

Gas Heat Conduction in Evacuated Flat-Plate Solar Collectors: Analysis and Reduction

Journal of Solar Energy Engineering ◽

10.1115/1.2847807 ◽

1995 ◽

Vol 117 (3) ◽

pp. 229-235 ◽

Cited By ~ 10

Author(s):

T. Beikircher ◽

N. Benz ◽

W. Spirkl

Keyword(s):

Heat Conduction ◽

Flat Plate ◽

Pressure Range ◽

Gas Pressure ◽

Loss Reduction ◽

Stationary Heat ◽

Conduction Loss ◽

Flat Plate Solar Collector ◽

Gas Conduction ◽

Kinetic Gas Theory

In stationary heat-loss experiments, the thermal losses by gas conduction of an evacuated flat-plate solar collector (EFPC) were experimentally determined for different values of interior gas pressure. The experiments were carried out with air and argon in the pressure range from 10−3 to 104 Pa. For air, loss reduction sets in at 100 Pa, whereas at 0.1 Pa heat conduction is almost completely suppressed. Using argon as filling gas, gas conduction is reduced by 30 percent (compared to air) at moderate interior pressures of 1000 Pa. With decreasing pressure this reduction is even greater (50 percent reduction at 10 Pa). A theory was developed to calculate thermal losses by gas conduction in an EFPC: Fourier’s stationary heat conduction equation was solved numerically (method of finite differences) for the special geometry of the collector. From kinetic gas theory a formula for the pressure dependency of the thermal conductivity was derived covering the entire pressure range. The theory has been validated experimentally for the gases air and argon. Calculations for krypton and xenon show a possible gas conduction loss reduction of 60–70 percent and 75–85 percent (with respect to air, depending on gas pressure), corresponding to a reduction of the overall collector losses of up to 40 percent.

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PENGGUNAAN LEMBAR KERJA PESETA DIDIK (LKPD) UNTUK MENINGKATKAN KETERAMPILAN BERFIKIR FLEKSIBEL PADA MATERI FISIKA DITINJAU DARI PERBEDAAN GENDER DI SMA NEGERI 11 BANDA ACEH

Jurnal Ilmiah Didaktika ◽

10.22373/jid.v18i1.3088 ◽

2018 ◽

Vol 18 (1) ◽

pp. 77

Author(s):

Nurul Fajri Saminan ◽

Mahyana Mahyana

Keyword(s):

Gender Differences ◽

Thinking Skills ◽

Female Group ◽

Thinking Skill ◽

Design Data ◽

Student Work ◽

Male And Female ◽

Flexible Thinking ◽

Kinetic Gas Theory ◽

Banda Aceh

A study has been conducted on the use of Student Work Sheets (LKPD) to improve Flexible thinking skills in terms of gender differences. The research was conducted at SMAN 11 Banda Aceh. Flexible thinking is the ability to generate varied answers or ideas and can see a problem from different perspectives. LKPD is a sheet containing tasks that are usually in the form of instructions and steps to complete the task. Both classes are male and female class using LKPD method. The method used is one-group pretest posttest design. Data collection is done by technique of description test that is to measure Flexible thinking skill. The results showed that there were differences in the increase of male and female group of students to Flexible thinking skill with the use of LKPD on kinetic gas theory material with significance value 0,05 and Fhitung (1,85)

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