Abstract:

Significance Maintaining personal thermal comfort is crucial to personal health. Current thermal management technologies including heating, ventilation and air conditioning (HVAC) can satisfy thermal comfort by indirectly changing the ambient temperature. However, the substantial energy consumption and greenhouse gas emission make them difficult to meet the requirement of sustainable development. More importantly, the indiscriminate space thermal management technologies cannot meet the personal customized requirements. As a result, the concept of personal thermal management draws research attention, considering that human body is an excellent radiator. The personal thermal management fabrics can achieve local and efficient temperature control by regulating the heat transfer pathway between human body and environment (convection, conduction, radiation and sweat), avoiding massive electric energy wasting on space heating and cooling. The radiative thermal management fabrics can selectively regulate the absorption/reflection/transmission of solar and mid-infrared radiation, helping to maintain the thermal comfort of human body while substantially reduce the energy consumption of active heating and cooling. This thermal management strategy with zero energy consumption is of great significance for energy saving and carbon reduction.
Progress At present, radiative thermal management fabrics can be roughly divided into radiative cooling fabrics, i.e. radiative heating fabrics and dual-mode radiative thermal management fabrics according to their spectrum design, and the radiative cooling fabrics can be divided into three categories, namely mid-infrared high transparency, mid-infrared selective emission and mid-infrared non-selective emission. For radiative-cooling fabrics, wearing such fabrics can greatly reduce the energy consumption of air conditioners while maintaining the same thermal comfort. Similarly, the radiative heating fabrics absorb solar energy while reducing the radiative heat dissipation of the human body, thus meeting the thermal comfort in the cold environment, and greatly reducing the energy consumption of active heating equipment. The dual-mode thermal management fabric overcomes the contradiction between the fixed spectral design and the dynamic environment, which is conducive to the adaptive thermal management.
Conclusion and Prospect Although great progress has been achieved in the research of single mode or dual mode radiative thermal management fabrics, there are still some problems to be solved so as to bridge the gap between scientific research and practical application. (1) Neither single nor dual mode thermal management fabrics can achieve continuous adjustment of spectral emissivity/absorptivity, so they cannot achieve continuous temperature modulation, which is difficult to meet precise personal thermal comfort. (2) Large area preparation of radiative thermal management fabric is not equivalent to mass preparation. Therefore, the low-cost continuous fabrication of radiative thermal management fabric is of practical significance for its commercialization. (3) Considering that color is the inevitable requirement of the garment industry, the current radiative thermal management fabrics still face the contradiction between color and selective spectrum. Therefore, under the premise of meeting the requirement of selective spectrum, simplifying the preparation method and reducing the preparation cost are helpful to popularize the application of colored radiative thermal management fabrics. (4) The functional materials used in the radiative thermal management fabric reduce the wearing comfort. Thermal management performance and wearability should be considered at the same time in the design of fabrics.

Key words: functional fabric, passive personal thermal management, radiative thermal management fabric, zero energy consumption, spectral design