應用熱管於儲能系統之研究

Application of Heat Pipe in Energy Storage System

陳柏任(Bo-Ren Chen)

指導教授 ： 陳希立

國立臺灣大學/工學院/機械工程學研究所/博士(2007年)

https://doi.org/10.6342/NTU.2007.00773

摘要

本文主要目的是分別提出應用熱管於不同儲能系統之新型設計：過冷式儲冰空調系統、兩相密閉熱虹吸管太陽能集熱器及相變散熱模組，並以實驗測試的方式針對各系統在不同操作條件下的性能進行探討，本研究亦利用熱力電阻電容模式做為理論性能分析工具，模擬各系統在不同設計下的運轉狀況，進而提出有效的性能提昇設計。
過冷式儲冰空調系統以兩相密閉熱虹吸管作為儲冰槽的熱傳元件，利用融冰過程對管路內冷媒進行過冷，可增加系統28 %的冷凍能力及8 %的性能係數，並可使冷房溫度維持恆定，而儲冰槽的熱力電阻電容模型理論分析結果顯示，增加熱管內部工作流體（R-22）薄膜冷凝面積及儲能物質（水）的熱交換面積，皆可提昇儲冰槽的儲冰速率，其中以同時實施前述兩種改善設計的提升效益最高，可減少25 %的儲冰時間。
兩相密閉熱虹吸管太陽能集熱器利用工作流體（酒精）的池沸騰與薄膜冷凝等熱傳機制進行能量傳遞，可降低集熱板溫度以及系統熱損失進而提升系統性能，本研究集熱器之特徵效率較傳統者平均值高出18 %，在集熱器理論性能改善分析結果中，將鰭片管數目加倍或增加50 %的工作流體熱傳導係數，可分別提昇3 %與4 %的儲熱效率，若以在集熱器銅管內壁增加燒結體並降低工作流體充填量做為改善策略，則可增加6 %的儲熱效率。
利用儲能系統概念所開發的相變散熱模組則可應用於電子元件散熱領域，在元件發熱率變動下，採用相變材料（二十三烷）做為儲能物質，可較採用不具相變能力者（水）節省46 %的風扇耗電，相變散熱模組理論性能分析結果顯示，在增加散熱鰭片數目、提高相變材料與熱管間熱傳面積及相變材料熱傳導係數等改善設計中，以提高三倍相變材料熱傳導係數者可降低5.5 oC電子元件溫度震盪，具有最佳散熱性能提昇效果。

關鍵字

熱管 ； 兩相熱紅吸管 ； 儲冰空調 ； 太陽能集熱器 ； 相變材料 ； 電子散熱

並列摘要

This dissertation experimentally and theoretically investigates the thermal performances of three innovative energy storage system designs which are subcooled ice storage air-conditioning system, two-phase thermosyphon solar water heater and phase change material (PCM) cooling module. Theoretical models are developed to simulate the thermal characteristics of the systems with various design modifications by employing thermal resistance-capacitor model (RC model) in this research.
The subcooled ice storage air-conditioning system adopts an ice storage tank as a subcooler which utilizes the superior heat transfer characteristics of two-phase closed thermosyphon (with R-22 as working fluid) and eliminates the drawbacks found in conventional systems. The subcooler is effective to enhance 28 % more cooling capacity and 8% higher coefficient of performance (COP) by the subcooling process. The theoretical analysis result shows that the ice storage tank reduces 25 % of charging time by both increasing film condensation area in the fin tubes and heat transfer area between the fin tubes and energy storage material (water).
The proposed two-phase thermosyphon solar water heater absorbs and transfers thermal energy by conducting boiling and condensation mechanisms with working fluid of ethyl alcohol inside. The system thermal efficiencies are experimentally verified from the hourly, daily, and long-term test. The two-phase thermosyphon can effectively reduce heat loss and provide 18 % higher system characteristic efficiency than that of the conventional systems. The simulation results show that the system achieves 3 % and 4 % greater charge efficiency as fin tubes number becomes twice and thermal conductivity of working fluid is 50 % higher, respectively. Six percent enhancement is obtained when wick structure are installed in the thermosyphon within lower working fluid fill ratio.
The PCM cooling module applies energy storage concept in the system design. The device can shift peak heating power of the electronic component by storing or releasing the thermal energy. The performance testing results demonstrates that the cooling module lessens 46 % of the fan power consumption with PCM (tricosane) rather than water as energy storage material in the storage tank. The RC model analysis is performed to simulate the heater temperature variation for the case of oscillating heating power. The thermal performance can be enhanced with a larger fin area, higher PCM thermal conductivity, or increase of the area between the PCM and heat pipe. The maximum heater temperature decreases from 67.7 oC to 52.7 oC as the PCM thermal conductivity is treble.

並列關鍵字

Heat Pipe ； Two-Phase Thermosyphon ； Ice Storgae Air-Conditioning System ； Solar Water Heater ； Phase Change Material ； Electronic Cooling

參考文獻

55 CALMAC, 1994, An Introduction to Off-Peak Air Conditioning for Commercial Application, CALMAC, U.S.A.

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