生物质基纳米流体的可控合成及其强化传热性能研究

As a rich resource, the utilization technology of biomass has become one of the research focuses in the relevant field. Controllable synthesis of high thermal conductivity nanofluid from biomass (rich in silicon dioxide) is a new technology of biomass resource utilization. .On the base of experimental method combined with characterization, the project explores the synthesis rules of high-thermal-conductivity nanofluids (SiO2 nanofluids) derived from biomass. Through adjusting the raw material granularity, pretreatment method and heat treatment conditions (two-step heat treatment), the structure of biomass based nano-SiO2 is adjusted. And based on characterization methods, the influence of treatment conditions on the SiO2 structure is revealed. In terms of SiO2 structure and preparation process, controllable synthesis of nanofluids is obtained. Nano-SiO2 obtained is applied to the preparation of stable nanofluids by a two-step method. The conductivity of SiO2 nanofluids under different conditions is test by using transient hot wire method, revealing the influence rules. Furthermore, the heat transfer performance of biomass based SiO2 nanofluids is test and the characteristic equations of the heat transfer are built. The result is utilized to optimize the synthesis method of biomass-based nanofluids. The objective of the present project aims to provide empirical correlations and theoretical guidance to develop a high-thermal-conductivity nanofluids derived from biomass.

生物质能资源丰富，其开发利用技术是该领域的研究热点。以富含SiO2生物质为原料,可控制备高导热性纳米流体是生物质资源利用的一项新技术。.本项目拟采用实验联合表征的分析方法深入探究生物质高导热性纳米流体（SiO2纳米流体）的合成规律。通过调控原料粒度、预处理工艺和热处理条件（两步热处理工艺）三个方面调控生物质基纳米SiO2结构，联合多种表征手段揭示处理条件对生物质基纳米SiO2结构的影响机制；从原料SiO2的结构和制备工艺两个方面调控SiO2纳米流体导热系数，获得稳定生物质基SiO2纳米流体的制备方法；采用瞬态热线法测试纳米流体的导热系数，揭示生物质基纳米流体的导热系数影响规律；最后，探索生物质基纳米流体的强化传热性能，建立传热性能特征方程，优化生物质基纳米流体的合成方法。研究成果拟为制备基于生物质的高导热纳米流体提供经验公式和理论指导。

生物质能资源丰富，其开发利用技术是该领域的研究热点。本项目采用热处理法从多种富硅生物质中提取高纯度介孔SiO2，研究了酸处理浓度对SiO2纯度的影响规律，采用酸洗焙烧后获得SiO2的纯度达到99.538%，产率为15.0%，相应的比表面积为335 m2/g，孔体积为0.41 cm3/g，平均孔径为4.9 nm；接着采用CO2预热解法和KNO3溶解法对SiO2进行孔道调控，联合多种表征手段对SiO2结构进行表征，发现通过CO2预热解法进行孔道调控，SiO2在2.5 nm附近出现了新孔，而KNO3溶解法可以有效地扩大孔径，当采用0.01mol/L KNO3浸渍SiO2并焙烧扩孔时，平均孔径增加到9.13 nm；基于瞬态热线法，搭建并优化纳米流体导热系数测量装置，采用两步法制备SiO2-DW纳米流体，测试纳米流体的导热系数，发现SiO2-DW纳米流体的导热系数高于经验公式的预测值；将SiO2-DW应用于小通道波纹管中，研究纳米流体浓度、脉动波频率、振幅、雷诺数等参数对管内对流换热系数的影响，以稻壳二氧化硅为原料制备的SiO2/DW纳米流体为换热介质，在Re=385、f=0.67 Hz、振幅为A15时，换热增加率最大可以达到143%，表明稻壳SiO2-DW纳米流体具有广泛的应用前景。