By Josh Perry, Editor
[email protected]

Simulations based on the elastocaloric effect (ECE) performed at Agência FAPESP, a research facility in São Paulo, Brazil, revealed that mechanical strain in carbon nanotubes causes them to extract heat more efficiently and increases their potential for electronics cooling.

Study shows that mechanically stretched carbon nanotubes extract heat efficiently and could be used to cool flexible electronic devices. (Wikimedia Commons)

The study was based on simulations from 2016 that showed carbon nanotubes had a temperature variation of up to 30°C when under strain, according to a report from FAPESP. In this study, researchers expanded the simulations to a complete thermodynamic cycle. Researchers studied the impact of strain and release.

“The performance coefficient is defined as the heat extracted by a system from a given region divided by the energy expended to do so,” the report continued. “In the case of a household refrigerator, for example, it shows the amount of heat extracted by the appliance from the internal environment in proportion to the electricity consumed. The best household refrigerators have performance coefficients on the order of 8, meaning they transfer eight times more thermal energy from inside to outside than the amount of electricity extracted from the supply grid to perform the exchange.”

Simulations showed coefficients of 4.1 and 6.5 for the carbon nanotubes, which, combined with the ability of the material to stretch as much as 20 percent, increases its potential viability for creating nanoscale electronics.

The research was recently published in Annalen der Physik. The abstract stated:

“Vapor?compression dominates the market for refrigeration devices due to low cost and relatively high efficiency. However, the most efficient vapor refrigerants are either ozone depleting or global warming substances. Solid?state cooling is a young field of research with promising results toward the development of new, efficient, and environment friendly technology for a new generation of refrigeration devices.

“One of these methods is based on the so?called elastocaloric effect (ECE), which consists of a temperature variation of a system in response to the application of adiabatic stresses. Although most of the literature describes the study of ECE solid?state cooling based on materials undergoing phase?transitions, a study recently predicted that carbon nanotubes (CNTs) present ECE as large as 30 K for 3% of strain.

“This motivates research toward the development of nanorefrigerators. As nobody knows the efficiency of such an ECE?based CNT nanorefrigerator, here, significantly high coefficient of performance values of 4.1 and 6.5, and extracted heat per weight as large as 40 J g⁻¹ are reported for a zigzag CNT nanorefrigerator operating in an Otto?like thermodynamic cycle. This efficiency is shown to overcome that of some other ECE materials.”