Joule heating, also called resistive or ohmic heating, is the process by which electrical current passing through a conductor dissipates energy as heat. The flash Joule heating dossier reproduces a Nature Reviews Clean Technology review that cites the relation Q ∝ I²Rt and credits the discovery to James P. Joule's 1841 paper "On the production of heat by voltaic electricity" in Proc. R. Soc. Lond., which appears in the review's reference list.
Joule heating in personal thermal management
Joule heating is the active warming mechanism available to the conductive nanowire network in this source. Because the AgNW coating forms an electrically conductive network, connecting the cloth to a power source such as a battery allows it to generate heat resistively, complementing the passive radiative insulation.
According to the phys.org account of the study, the researchers demonstrated that as little as 0.9 V can safely raise clothing temperature to 38 °C, which is 1 °C higher than the human body temperature of 37 °C.
The carbon nanotube cloth tested by the same team is also conductive and therefore suitable for Joule heating, but its high emissivity makes it a poor body-heat reflector. This separates the two functions: conductivity enables active heating, while low emissivity enables passive reflection.
The modeled energy comparison in the source is based on this active mode: an average person is said to require 367 W of heating power, versus 12 W for the AgNW clothing when actively operating.
Relevance to flash Joule heating
Flash Joule Heating (FJH) is the direct application of Joule heating to a feedstock: the sample itself is the resistor, so heat is generated internally rather than transferred from an external element. The dossier contrasts this with indirect Joule heating, where a resistance furnace generates heat that must then be conducted into the load, incurring transfer losses. The review excerpt claims approximately 100% sample heating efficiency for the direct configuration.
The same principle underlies Flash Sintering (Field-Assisted Sintering), where an electric field and current densify ceramic powders, and the various metallurgical reduction processes in the dossier's patent list.
Related pages
Flash Joule Heating (FJH) · James P. Joule · Flash Sintering (Field-Assisted Sintering) · agnw-cloth · cnt-cloth · personal-thermal-management
Source notes & attribution
- Po-Chun Hsu, et al., "Personal Thermal Management by Metallic Nanowire-Coated Textile," Nano Letters , DOI 10.1021/nl5036572, 2014.
- Lisa Zyga, "Super-insulated clothing could eliminate need for indoor heating," phys.org, Jan 08, 2015.
- James P. Joule, "On the production of heat by voltaic electricity," Proc. R. Soc. Lond. , 1841 (as cited in the Rex Research flash Joule heating dossier).
- Rex Research flash Joule heating dossier (rexresearch/13e1b9f8c2f1b561.md).
- https://rexresearch.com/cuinanoagwire/cuinanoag.html
- https://rexresearch.com/FlashJouleHeating/FlashJouleHeating.html