摘要
The nanofluid-based direct absorption solar collector(NDASC)ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid,reducing thermal resistance in the energy transfer process.However,further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures.Herein,this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400-600 K.When the nanofluid’s absorption coefficient reaches 80 m^(-1),the NDASC shows the optimal thermal performance,and the NDASC with local Sn-In_(2)O_(3) coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC.Furthermore,hybrid coatings with Sn In_(2)O_(3)/WTi-Al_(2)O_(3) are explored,and the optimal coverage angles are determined.The NDASC with such coatings shows a 10.22%-17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%-19.5% increase compared to the traditional surface-type solar collectors,demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.
纳米流体直接吸收式太阳能集热器可通过纳米流体直接吸收太阳辐射,从而降低能量传递过程中的热阻。然而,为了进一步提高集热性能需要抑制高温下纳米流体的热损失。本文提出了一种新型直接吸收式太阳能集热器,其中集热管的外表面覆盖有功能性光学涂层,并建立了三维计算流体动力学模型来研究400~600 K温度范围内收集器上的能量流分布。当纳米流体的吸收系数达到80 m^(-1)时,集热器呈现出最佳的集热性能。与原始集热器相比,具有局部Sn-In_(2)O_(3)涂层的集热器在400 K下的热效率可提高7.8%。此外,还探索了Sn-In_(2)O_(3)/WTi-Al_(2)O_(3)复合涂层的影响,并确定了最佳覆盖角。与原始集热器相比,该新型集热器的热效率可提高10.22%~17.90%;与传统的表面吸收太阳能集热器相比可提高7.6%~19.5%,证明了本文所提出的基于功能性光学涂层的集热器能量流控制策略的有效性。
基金
Project(52476095)supported by the National Natural Science Foundation of China
Project(kq2506013)supported by Changsha Outstanding Innovative Youth Training Program,China。
作者简介
Corresponding author:SUN Zhi-qiang,PhD,Professor,E-mail:zqsun@csu.edu.cn,ORCID:https://orcid.org/0000-0003-0518-3275;Corresponding author:ZHENG Nian-ben,PhD,Associate professor,E-mail:zhengnb@csu.edu.cn,ORCID:https://orcid.org/0000-0003-0518-3275。
