In this paper, we describe the possibility of using the energy of a compressed air flow, where cryogenic temperatures are achieved within the flow behind the nozzle, when reaching a critical flow in order to maximize the energy gained. Compared to the energy of compressed air, the energy obtained thermoelectrically is negligible, but not zero. We are therefore primarily aiming to maximize the use of available energy sources. Behind the aperture separating regions with a pressure difference of several atmospheres, a supersonic flow with a large temperature drop develops. Based on the Seebeck effect, a thermocouple is placed in these low temperatures to create a thermoelectric voltage. This paper contains a mathematical-physical analysis for proper nozzle design, controlled gas expansion and ideal placement of a thermocouple within the flow for best utilization of the low temperature before a shockwave formation. If the gas flow passes through a perpendicular shockwave, the velocity drops sharply and the gas pressure rises, thereby increasing the temperature. In contrast, with a conical shockwave, such dramatic changes do not occur and the cooling effect is not impaired. This article also contains analyses for proper forming of the head shape of the thermocouple to avoid the formation of a detached shockwave, which causes temperature stagnation resulting in lower thermocouple cooling efficiency.

Department of Electrical and Electronic Technology Brno University of Technology 61100 Brno Czech Republic

Institute of Scientific Instruments of the CAS Královopolská 147 61264 Brno Czech Republic

Zobrazit více v PubMed

Barnhart C.J., Benson S.M. On the importance of reducing the energetic and material demands of electrical energy storage. Energy Environ. Sci. 2013;6:1083–1092. doi: 10.1039/c3ee24040a. DOI

Salga J., Hoření B. Tabulky Proudění Plynu. UNOB; Brno, Czech Republic: 1997.

Compressible Aerodynamics Calculator. [(accessed on 14 April 2018)]. Available online: http://www.dept.aoe.vt.edu/~devenpor/aoe3114/calc.html.

Daněk M. Aerodynamika a Mechanika Letu. VVLŠ SNP; Košice, Slovak Republic: 1990. p. 83.

Jirků T., Fiala P., Kluge M. Magnetic resonant harvesters and power management circuit for magnetic resonant harvesters. Microsyst. Technol. 2010;16:677–690. doi: 10.1007/s00542-010-1045-5. DOI

Fiala P., Drexler P., Nespor D. Principal tests and verification of a resonance-based solar harvester utilizing micro/nano technology. Microsyst. Technol. 2014;20:845–860. doi: 10.1007/s00542-013-2063-x. DOI

Neděla V. Ph.D. Thesis. Brno University of Technology; Brno, Czech Republic: 2006. Detekce Signálních Elektronů v Prostředí Vysokého Tlaku Plynů Environmentálního Rastrovacího Elektronového Mikroskopu.

Maxa J., Bílek M., Hlavatá P., Vyroubal P., Lepltová K. Comparisons Using Methods of Continuum Mechanics and Monte Carlo at Differentially Pumped Chamber. Adv. Mil. Technol. 2016;11:143–150. doi: 10.3849/aimt.01120. ISSN 1802–2308. DOI

Maxa J., Neděla V. The Impact of Critical Flow on the Primary Electron Beam Passage through Differentially Pumped Chamber. Adv. Mil. Technol. 2011;6:39–46.

Yang M.-Z., Wu C.-C., Dai C.-L., Tsai W.-J. Energy Harvesting Thermoelectric Generators Manufactured Using the Complementary Metal Oxide Semiconductor Process. Sensors. 2013;13:2359–2367. doi: 10.3390/s130202359. PubMed DOI PMC

Dejč M.J. Technická Dynamika Plynů. SNTL; Prague, Czech Republic: 1967.

Uruba V. Turbulence. Faculty of Mechanical Engineering, Czech Technical University in Prague; Prague, Czech Republic: 2009.

Brer D.W., Pankhurst R.C. Pressure-Probe Methods for Determining Wind Speed and Flow Direction. Her Majesty´s Stationery Office; London, UK: 1971.

Škorpík J. Proudění Plynů a par Tryskami. Transformační Technologie; Brno, Czech Republic: 2006.

Maxa J., Neděla V., Jirák J., Vyroubal P., Hladká K. Analysis of gas flow in a secondary electron scintillation detector for ESEM with a new system of pressure limiting apertures. Adv. Mil. Technol. 2012;7:111–116.

Vyroubal P., Maxa J., Neděla V., Jirák J., Hladká K. Apertures with Laval Nozzle and Circular Orifice in Secondary Electron Detector for Environmental Scanning Electron Microscope. Adv. Mil. Technol. 2013;8:59–69. ISSN 1802–2308.

Danilatos G. Velocity and ejector-jet assisted differential pumping: Novel design stages for environmental SEM. Micron. 2012;43:600–611. doi: 10.1016/j.micron.2011.10.023. DOI

Thevenin D., Janiga D. Optimization and Computational Fluid Dynamics. Springer; Berlin/Heidelberg, Germany: 2008.

Moran M., Shapiro H. Fundamentals of Engineering Thermodynamics. 3rd ed. John Wiley & Sons, Inc.; New York, NY, USA: 1996.

Baehr H. Thermodynamik. 14th ed. Springer; Berlin/Heidelberg, Germany: 2009.

Flow Past a Cone. [(accessed on 29 May 2021)]; Available online: https://www.grc.nasa.gov/WWW/k-12/airplane/coneflow.html.

CFD Analyses of Density Gradients under Conditions of Supersonic Flow at Low Pressures

Mathematical-Physics Analyses of the Nozzle Shaping at the Aperture Gas Outlet into Free Space under ESEM Pressure Conditions

The Impact of Nozzle Opening Thickness on Flow Characteristics and Primary Electron Beam Scattering in an Environmental Scanning Electron Microscope

Impact of Supersonic Flow in Scintillator Detector Apertures on the Resulting Pumping Effect of the Vacuum Chambers

Slip Flow Analysis in an Experimental Chamber Simulating Differential Pumping in an Environmental Scanning Electron Microscope

Application of Prandtl's Theory in the Design of an Experimental Chamber for Static Pressure Measurements