Experiment Study On Heat Transfer Performance For Adsorbent Of Composite Nano-sio₂

Adsorption refrigeration system is a kind of environmentally friendly refrigeration system, which can be driven directly by low grade energy such as solar energy and industrial waste heat. It has a lot of advantage, such as simple structure, no moving element, no noise and good shock resistance etc, and it has been well studied on many aspects. However, the practical use was limited due to the low overall system efficiency, in which the pair of refrigerants was the most significant. Large absorption chillers size and low efficiency of the overall system were result of poor adsorption properties and thermal conductivity. Therefore, the development of new efficient absorption of the workers was particularly important. Based on the excellent absorption performance and low thermal conductivity of Nano-SiO₂, adding high thermal conductivity materials were raised in this paper to improve its thermal conductivity. The main results of the work and innovation are as follows:(1) In order to improve the thermal conductivity of Nano-SiO₂, high thermal conductivity additives such as graphite and silicon carbide, PVA used as binder and different forces exerted on the sample were employed to consolidate Nano-SiO₂.(2) Thermal conductivity of Nano-SiO2 was measured with steady-state plate method in this paper. The principles and methods of the experiment were discussed. Formulas considering and ignoring the sample's side cooling were raised. The results were discussed.(3) To choose suitable measuring parameters, corresponding mathematical model based on the thermal conductivity measuring device was founded, and some important elements related to thermal conductivity measurement were simulated, such as environment temperature, heat source temperature, thickness of the sample etc. It was found that, side dissipated heat increased not only absolutely but also relatively to total heat transfer with heat source temperature and thickness of the samples increasing, or environment temperature and sample's heat conductivity decreasing.(4) The results show that graphite impact on thermal conductivity performance of the composite material greater, which was followed by binder, silicon carbide and curing density (related to pressure). The higher the graphite content, the greater the measurement results of samples' thermal conductivity. The impact of silicon carbide was the first increasing and then decreasing, which can be seen from the trend chart of the factors. So the best ratio of SiC should be 10:1.