Improving Heat Dissipation and Temperature Uniformity in Radiative Cooling Coating

Abstract

Heat dissipation has become a key issue in electronic devices with high integration and miniaturization. As an effective way of heat transfer, radiative cooling has aroused a great attention in these devices. However, heat dissipation based on radiative cooling coating is limited by the poor heat spreading and temperature nonuniformity. Herein, a synergic augment strategy of excellent thermal conduction and strong thermal emission is proposed to improve the heat dissipation and temperature uniformity of radiative cooling coating. By the strategy, a composite coating consisting of poly(vinylidene fluoride‐co‐hexafluoropropene) and graphite is designed. It is shown via experiment that heat dissipation in composite coating is enhanced by 7% during daytime. A large temperature reduction of about 15.5 °C is obtained at the surface of the heat source with a composite coating during daytime. The temperature difference of the surface for composite coating within 2 °C demonstrates that the temperature uniformity of radiative cooling coating is improved.

Switchable Radiative Cooling from Temperature-Responsive Thermal Resistance Modulation

“…36 However, for the much lower contact pressure (64 Pa), a considerable calculation error will be induced by the Mikic elastic model. Thus, we employed an empirical equation, eq 6, 25 to estimate the thermal resistance. The thermal conductivity of glass for the calculation is 1.08 W•m −1 •K −1 at room temperature based on the measured specific heat capacity (Figure 5e,f, Supporting Information).…”

“…In the SW, measurement is taken by a spectrophotometer (Agilent Cary-5000) with an integrating sphere of DRA2500 along with barium sulfate solid that is selected as a standard, and in the IR region, a Fourier transform infrared spectrometer (Vertex 80v) is employed to characterize the RCC’s reflectance with a gold film used as a reflectance standard. As an important parameter to judge the radiative cooling capacity of the coating, solar reflectance ( R̅ solar ) and infrared emission (ε̅ atw ) calculated by eqs and where λ is the wavelength, I solar (λ) is the AM1.5 standard solar spectrum, ρ solar (λ) is the solar spectral reflectance in the solar band, E λ, T (λ) is the blackbody spectral radiative intensity at 25 °C, ρ atw (λ) is the spectral reflectance at atmospheric transmittance window (8–13 μm), and τ atw (λ) is the spectral transmittance at 8–13 μm, where τ atw (λ) is assumed as zero.…”

Functional Radiative Cooling: Basic Concepts, Materials, and Best Practices in Measurements

“…Generally, the pores within polymers serve as light scattering entities because of the mismatch in the refractive index (as compared with the polymer matrix); therefore, refractive index modulation of the pores allows for the control of the solar spectral regime. Among a wide range of polymers, porous poly­(vinylidene fluoride-hexafluoropropylene) (P­(VdF-HFP)) has been frequently utilized in RC. ,− For example, Wang et al reported a temperature adaptive RC device using a combination of porous P­(VdF-HFP) and thermochromic microcapsules. Here, the color of the thermochromic microcapsules fades (high reflectance state) from the initial rose red (low reflectance state) upon reaching the critical temperature of ∼33 °C as shown in Figure b .…”

Supplementary document for Inverse design, fabrication, and tolerance to extreme environments of radiative cooling coating - 5477376.pdf

“…As for the discriminant condition of sifting, net radiative cooling power (∆𝑄) was chose to sift the optimal preparation preparation condition. Net radiative cooling power of PVDF-HFP coatings is calculated by the following Equations (1-8) [2,3]:…”