Heat Dissipation of Transparent Graphene Defoggers

Abstract

In spite of recent successful demonstrations of flexible and transparent graphene heaters, the underlying heat‐transfer mechanism is not understood due to the complexity of the heating system. Here, graphene/glass defoggers are fabricated and the dynamic response of the temperature as a function of input electrical power is measured. The graphene/glass defoggers reveal shorter response times than Cr/glass defoggers. Furthermore, the saturated temperature of the graphene/glass defoggers is higher than for Cr/glass defoggers at a given input electrical power. The observed dynamic response to temperature is well‐fitted to the power‐balance model. The response time of graphene/glass defogger is shorter by 44% than that of the Cr/glass defogger. The convective heat‐transfer coefficient of graphene is 12.4 × 10−4 W cm−2 °C−1, similar to that of glass (11.1 × 10−4 W cm−2 °C−1) but smaller than that of chromium (17.1 × 10−4 W cm−2 °C−1). The graphene‐based system reveals the lowest convective heat‐transfer coefficient due to its ideal flat surface compared to its counterparts of carbon nanotubes (CNTs) and reduced graphene oxide (RGO)‐based systems.

Relationship between Material Properties and Transparent Heater Performance for Both Bulk-like and Percolative Nanostructured Networks

“…For a given combination of electrical and thermal properties the steady state temperature increase is set by balance of Joule heating and heat dissipation and can be controlled via the voltage. Such devices are important for a number of applications from defogging of windows or mirrors 21 to performance optimisation of liquid crystalline displays via temperature control 31 to art conservation.…”

“…19,20 However, more recently, attention has turned to using nanostructured transparent conductors as transparent heaters. [21][22][23][24][25][26][27][28][29][30] Transparent heaters are simply conducting films which are thin enough to be transparent but can be heated up on application of a voltage. For a given combination of electrical and thermal properties the steady state temperature increase is set by balance of Joule heating and heat dissipation and can be controlled via the voltage.…”

Observation of convection phenomenon by high-performance transparent heater based on Pt-decorated Ni micromesh

“…The Ni-based micromesh film without Pt-decoration reaches the steady-state temperature of 160 • C. Meanwhile, the steady-state temperature of the Nibased micromesh film decorated with Pt for 180 s reaches to 200 • C. After the metallic mesh film is heated by Joule heating, the heat dissipates by conduction through the substrate, and by convection and radiation to the air. 24 The heat lost by conduction and radiation is negligible compared to the convective heat loss, because of the low thermal-conductivity substrate and the low emissivity of the electrode material. Thus, it is presumed that air convection is the main path of heat dissipation for the Ni-based micromesh films.…”

“…Thus, it is presumed that air convection is the main path of heat dissipation for the Ni-based micromesh films. 24,25 The convective heat power loss is expressed by 24,25 …”

Highly flexible, stretchable, patternable, transparent copper fiber heater on a complex 3D surface

“…Above all, the most critical issue is the limited power (P) that can be supplied to such materials. This severely restricts the maximum attainable temperature (T s ), since T s ∝ P. For example, the temperature ranges of graphene heaters, silver nanowire heaters, and heaters utilizing hybrid materials combining graphene and silver nanowires are 100-206°C, [19][20][21] 48-160°C, [22][23][24][25][26][27] and up to 225°C, 28,29 respectively.…”