奈米流體之混合散熱系統實驗平台建立與性能評估

Abstract

本研究主要設計一套混合散熱系統，利用比例閥控制兩邊流量，達到一組散熱系統同時可冷卻兩加熱源之目的，進而透過添加奈米碳管流體分析散熱效益評估。首先，建立一組混合散熱系統，系統元件(加熱水槽、水泵、熱交換器、比例閥及數位流量計)。本實驗使用兩加熱源總合為1kW、總流量分別為3、5及7L/min，利用比例閥電壓開度0.6-3V間進行閥門的變動，透過穩態實驗量測出適合兩加熱源之電壓開度及何種流量最適用混合散熱系統，最後選擇適合的開度及流量進行暫態實驗。再者，使用二階法配置出奈米碳管流體，並針對不同的溫度與濃度的熱傳導係數、密度、黏滯係數及比熱等基礎性質進行量測與分析，透過添加奈米碳管流體至混合散熱系統並與原流體-水進行散熱效益分析。各研究結果分別為:在遴選奈米碳管流體濃度實驗結果顯示0.125wt.%擁有最佳散熱效果；穩態實驗結果顯示不同的流量會使熱交換器熱交換量不同，而透過添加奈米碳管流體可提升10%的散熱量；在暫態實驗結果顯示奈米流體相較於水，擁有更佳的散熱效果，其散熱效益分別提升5~17%。本研究結果顯示使用奈米碳管流體運用在綠色動力的熱管理系統可有效縮減散熱器及水泵體積，對於電動車空間配置、續航力及省電之貢獻度將於未來進行驗證。This research mainly designs a hybrid heat dissipation system which uses a proportional valve to control coolant flow rates in two paths in order to cool dual power sources at the same time so that thermal efficiency of Carbon nanotubes/Water nanofluids (CNWNs) can be increased. First, an experimental platform is established for the assessment of the innovation. Mechanical elements (coolant, cooling system components) and electrical elements (actuators, sensors, data recorders, etc.) are included. This experimental employed two heating sources of total 1000W; the coolant flow rates are: 3, 5, and 7L/min.; the proportional-valve voltage is within 0.6-3V. Through steady state experimental results, we searched proper valve voltages and flow rates to keep two power sources at optimal operating temperatures. Then, we can further select best operations for the transient experiments. Second, we used two-step synthesis method for producing CNWNS. The experiments for thermal conductivity, density, viscosity, specific heat and heat dissapation performance at difference temperatures and concentrations were conducted for both bulk fluid (water) and CNWNS. Experimental results demonstrate that: (1)0.125wt.% CNWNS have optimal thermal efficiency; (2)for the steady-state experimental, different flow rates have difference heat exchange values and 10% efficiency was increased for CNWNS compared to water; (3)for the transient experiments, CNWNS have better thermal efficiency than water. The heat dissapation of CNWNS compared with water is increase for 5~17%. This research shows that using CNWNS can reduce the occupied volume of heat exchanger and pump of this green thermal management system.The contributions for space arrangement, traveling distance and energy reduction will be verified for Evs in the near future.