Invertis Journals of Science & Technology

Arun Kumar ¹, B. N. Agrawal ², Nitin Kumar ¹

Affiliations
1 NGF College of Engineering and Technology, Palwal, Haryana, IN
2 Delhi College of Technology and Management, Palwal, Haryana, IN

Abstract

Zinc oxide and many other materials have long been used in thermoelectric devices for Waste heat recovery to convert heat into electricity. The performance of these materials depends on the figure-of-merit ZT (=S2σ T/κ), where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the temperature. The study focused on the doping mechanisms of ZnO with Aluminum, and then the thermoelectric properties of ZnO doped with aluminum by spark plasma sintering technique. For Al-doped ZnO, the spark plasma sintering technique used to prepare samples from precursors canceled at various temperatures. I take these samples for study for doping mechanism in different material. For Al, doped ZnO, the spark plasma sintering conditions together with the micro structural evolution and thermoelectric properties of the samples were studied in detail. Moreover, nano composite approaches have been used to study the thermoelectric properties of other material systems such as Zinc oxide and half-Heusler phases. We observed a significant improvement in peak ZT of nano structured n-type HH compound 0.8 to 1.0 respectively. Here we studied only n-type HH compounds. The improvement of figure of merit is mainly due to the reduction of thermal conductivity. This nanostructure approach is applicable to many other thermoelectric materials that are useful for automotive, industrial waste heat recovery, space power generation and many other fields.

Keywords

Heusier Phases, Doping Mechanism and Thermoelectric Devices.

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Yogesh ¹, Ashok Kumar ², Arun Kumar ³

Affiliations
1 Satya College of Engineering and Technology, Palwal (Haryana), IN
2 Applied College of Management and Engineering, Palwal (Haryana), IN
3 Ratan Institute of Technology and Management, Palwal (Haryana), IN

Abstract

The effect of roughness on pressure drop and heat transfer in circular tubes has been extensively studied in literature. The pioneering work of Nikuradse (1933) established the sand grain roughness as a major parameter in defining the friction factor during laminar and turbulent flows. Recent studies have indicated a transition to turbulent flows at Reynolds number values much below 2300 during single-phase flow in channels with small hydraulic diameters. In the present work, a detailed experimental study is undertaken to investigate the roughness effects in small diameter tubes. The roughness of the inside tube surface is changed by etching it with an acid solution.

Keywords

Roughness Effects, Reynolds Number and Acid Solution.

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