Bob Yirka is a writer for Phys.org.

Heat flow shown to be more efficient when temperature is oscillating than when static
Left: the L=30cm tall aspect ratio G=D/L=1 RBC cell with 28 mm thick top and bottom plates D=30cm in diameter made of thermally annealed copper of thermal conductivity λp=2210Wm−1K−1 and thermal capacity cp=0.144Jkg−1K−1 at THe=(TT+TB)/2≈5K , where TT and TB are typical temperatures of the top and bottom plates. From the top plate, most of the heat is removed via the heat exchange chamber to the liquid He vessel above it. The top plate temperature TT(t) is roughly set by pressure in the heat exchange chamber and more precisely tuned and modulated by the uniformly distributed heater glued in the spiral grove on the upper side of the top plate. A similar heater delivers either steady or harmonically modulated heat to the bottom plate. The temperature of the convective flow at locations as shown (distances in millimeters) is probed by small Ge sensors (numbered 1–12) and that of the plates by the finely calibrated Ge sensors Tt1, Tt2, Tb1, and Tb2 embedded in them; see the photograph in the top right, showing their positions and the spiral heater grove. Credit: Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.128.134502

A team of researchers from the Institute of Scientific Instruments working with a colleague from Charles University in the Czech Republic have shown that heat flows more efficiently when the temperature of the material through which it is flowing changes. Two years ago, a theory about heating and cooling helium in a container was proposed by the group in their paper published in the journal Physical Review Letters.

An example of heat flow was shown in 1916 by physicist John William Strutt. He put a heated coil below the fluid and a cooling plate on top. The liquid rose and fell in the container. The effect can be seen in the action of lava lamps. Two years ago, a team at the University of Twente proposed that the heat coming from the base would be more efficient if it moved. This theory has been shown to be correct by the researchers.

The work involved creating a container with a heating device at the bottom that could move through a temperature range. They put a cooling device on top. They used a gas instead of a liquid. They carried out their experiments under cooler temperatures. To learn more about the impact of such oscillations on the heat flowing through the system, they conducted multiple runs.

They found that the heat source was more efficient than they had predicted. The destabilization of the liquids in the chamber is thought to be the reason for the improvement in efficiency.

More information: P. Urban et al, Thermal Waves and Heat Transfer Efficiency Enhancement in Harmonically Modulated Turbulent Thermal Convection, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.128.134502 Journal information: Physical Review Letters

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Citation: Heat flow shown to be more efficient when temperature is oscillating than when static (2022, April 27) retrieved 27 April 2022 from https://phys.org/news/2022-04-shown-efficient-temperature-oscillating-static.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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