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R.J. Jenkins

Bio: R.J. Jenkins is an academic researcher. The author has contributed to research in topics: Thermal conductivity measurement & Solar mirror. The author has an hindex of 2, co-authored 2 publications receiving 3223 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a high-intensity short-duration light pulse is absorbed in the front surface of a thermally insulated specimen, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera.
Abstract: A flash method of measuring the thermal diffusivity, heat capacity, and thermal conductivity is described for the first time. A high‐intensity short‐duration light pulse is absorbed in the front surface of a thermally insulated specimen a few millimeters thick coated with camphor black, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera. The thermal diffusivity is determined by the shape of the temperature versus time curve at the rear surface, the heat capacity by the maximum temperature indicated by the thermocouple, and the thermal conductivity by the product of the heat capacity, thermal diffusivity, and the density. These three thermal properties are determined for copper, silver, iron, nickel, aluminum, tin, zinc, and some alloys at 22°C and 135°C and compared with previously reported values.

3,471 citations

Journal ArticleDOI
TL;DR: An expression for the thermal efficiency of a surface used as a receiver for spacecraft solar-power generation is derived in terms of the solar absorptance, hemispherical emittance, and concentration ratio.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor, and the principles used are equally applicable to most good thermoeLECTric materials that could enable improvement of thermoelectedric devices from niche applications into the mainstream of energy technologies.
Abstract: Lead chalcogenides have long been used for space-based and thermoelectric remote power generation applications, but recent discoveries have revealed a much greater potential for these materials. This renaissance of interest combined with the need for increased energy efficiency has led to active consideration of thermoelectrics for practical waste heat recovery systems—such as the conversion of car exhaust heat into electricity. The simple high symmetry NaCl-type cubic structure, leads to several properties desirable for thermoelectricity, such as high valley degeneracy for high electrical conductivity and phonon anharmonicity for low thermal conductivity. The rich capabilities for both band structure and microstructure engineering enable a variety of approaches for achieving high thermoelectric performance in lead chalcogenides. This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor. While these strategies are well demonstrated in lead chalcogenides, the principles used are equally applicable to most good thermoelectric materials that could enable improvement of thermoelectric devices from niche applications into the mainstream of energy technologies.

1,243 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the thermoelectric transport properties of p-type PbTe:Na, with high hole concentrations of approximately 1020 cm−3, from room temperature to 750 K. The greatly enhanced Seebeck coefficient at these doping levels can be understood by the presence of a sharp increase in the density of states around the Fermi level.
Abstract: Thermoelectric transport properties of p-type PbTe:Na, with high hole concentrations of approximately 1020 cm−3, are reinvestigated from room temperature to 750 K. The greatly enhanced Seebeck coefficient at these doping levels can be understood by the presence of a sharp increase in the density of states around the Fermi level. As a result, the thermoelectric figure of merit, zT, reaches ∼1.4 at 750 K. The influence of these heavy hole carriers may contribute to a similarly high zT observed in related p-type PbTe-based systems such as Tl-doped PbTe and nanostructured composite materials.

613 citations

Journal ArticleDOI
TL;DR: In this article, the temperature distribution within a thin slab of material which has received a short pulse of energy on one surface, for the case in which energy loss at the surfaces (by radiation or convection) is not negligible.
Abstract: Equations are derived giving the temperature distribution within a thin slab of material which has received a short pulse of energy on one surface, for the case in which energy loss at the surfaces (by radiation or convection) is not negligible. An analysis of these equations indicates that measurement of thermal diffusivity by the pulse method should be feasible even when losses are so large that the maximum temperature of the far face is only 10 or 20% of the no‐loss value; this includes nearly all materials, and temperatures to 2500°K or higher.

562 citations

Journal ArticleDOI
TL;DR: A review of significant modeling works performed in the area with a focus on the characterization of the thermal runaway hazard and their relating triggering events is presented in this article, where progress made in models aiming at integrating battery ageing effect and related physics is also discussed.

554 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the flash technique for measuring thermal diffusivity for the case of a cylindrical-shaped specimen of radius r0 and thickness a to determine the effects of radiation at high temperatures, finite duration of the heat pulse, and the feasibility of low temperature measurements.
Abstract: The flash technique for measuring thermal diffusivity is analyzed for the case of a cylindrical‐shaped specimen of radius r0 and thickness a to determine the effects of radiation at high temperatures, finite duration of the heat pulse, and the feasibility of low temperature measurements. It is found that the flash diffusivity method is useful in two complementary limits: (1) pulse time τ short compared to the characteristic thermal response time tc, (2) τ/tc of the order 1 to 10. The former case corresponds to the original description of Parker, Jenkins, and Abbott, while the latter case is suitable at very low temperatures. Moreover, it is shown that there is an optimum specimen thickness a for a given material and pulse time τ, in the sense that a higher temperature can be reached before any corrections have to be made to the Parker et al. analysis.

512 citations