Temperature Trapping: Energy-Free Maintenance of Constant Temperatures as Ambient Temperature Gradients Change

Abstract

It is crucial to maintain constant temperatures in an energy-efficient way. Here we establish a temperature-trapping theory for asymmetric phase-transition materials with thermally responsive thermal conductivities. Then we theoretically introduce and experimentally demonstrate a concept of an energy-free thermostat within ambient temperature gradients. The thermostat is capable of self-maintaining a desired constant temperature without the need of consuming energy even though the environmental temperature gradient varies in a large range. As a model application of the concept, we design and show a different type of thermal cloak that has a constant temperature inside its central region in spite of the changing ambient temperature gradient, which is in sharp contrast to all the existing thermal cloaks. This work has relevance to energy-saving heat preservation, and it provides guidance both for manipulating heat flow without energy consumption and for designing new metamaterials with temperature-responsive or field-responsive parameters in many disciplines such as thermotics, optics, electromagnetics, acoustics, mechanics, electrics, and magnetism.

Negative Energy Consumption of Thermostats at Ambient Temperature: Electricity Generation with Zero Energy Maintenance

“…Let us consider a one-dimensional case for steadystate heat conduction. In this case, a tripartite structure with a centrosymmetric-logistic-function form of the thermal conductivities of parts A and B could be used for temperature trapping [29]; see Fig. 1 and B have a steep but inverse change around this critical temperature.…”

“…In the past ten years, transformation thermotics has flourished and become a useful tool to control the flow of heat with high efficiency . In light of temperaturedependent transformation thermotics (for which thermal conductivities are a function of temperature) [26,27], the concept of an energy-free thermostat was theoretically proposed and experimentally demonstrated in 2016 [29]. This thermostat keeps a specific region at constant temperature (without the need to consume additional energy) even when ambient temperature gradients change greatly.…”

“…The underlying mechanism can be understood by a temperature-trapping theory established in Ref. [29]. Based on Fourier's law of heat conduction and the continuity equation of heat flow, the temperaturetrapping theory crucially depends on two structures with * jphuang@fudan.edu.cn asymmetric transitions between good and bad heat conductors.…”

Theory of transformation thermal convection for creeping flow in porous media: Cloaking, concentrating, and camouflage

“…Regarding the thermal conduction, it has been extensively studied by developing the theories of transformation thermotics since 2008 [1][2][3][4][5][6][7][8][9][10]. As a result, some novel thermal metamaterials like thermal cloaks [1][2][3][4][5][6][7][8][9][10], thermal concentrators [3], thermal rotators [3], thermal camouflage [8], and macroscopic thermal diodes [9] have been theoretically designed and/or experimentally realized, which pave a new way to control the conduction of heat.…”

A Brief Review on Thermal Metamaterials for Cloaking and Heat Flux Manipulation

“…Then, a theoretical analysis about nonlinear thermal effects in metamaterials (nonlinear thermotics) is discussed in refs. [137–139]. In Figure , a switchable thermal cloak is shown .…”