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鄭澤明29

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曾憲中、鄭澤明、李峰、陳易辰

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廢熱回收熱電轉換系統中的多孔性集熱器之熱傳特性實驗研究

Experimental Study of Heat Transfer Characteristics in the Porous Heat Absorber of Thermoelecteric Generator System for Wastem Heat Recovery

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Keywords：Heat transfer,porous materials,packed channel,brass beads

Abstract：本研究指在開發一種於車輛引擎廢熱回收轉換系統中的多孔性集熱器，以高效的集熱能力提昇廢熱回收熱能轉換系統的發電性能，將以實驗方法觀察充滿黃銅粒堆疊物之矩形通道在不對稱受熱下之熱傳特性，採用空氣為冷卻流體，多孔性材料係使用黃銅朱密實堆疊而成，黃銅珠粒徑(d)尺寸有2㎜、4㎜與6㎜等三種，測試通道寬度(W)固定為60㎜，變動參數為相對堆疊通道長度(L/d=5~60)、相對堆疊通道高度(H/d=1.67~15)、與雷諾數(=755~7921、38~2703)等。實驗結果指出，與通道水力直徑()相比較，紅銅珠粒徑(d)可能更適合做為整合堆疊通道熱傳數據的尺度參數;此外，粒子紐塞數()會隨著相對通道長度(L/d)減少而增加，但相對高度(H/d)對()的影響則不敏感；最後，本研究歸納所有實驗數據提出不同相對通道長度(L/d)、相對通道高度(H/d)與粒子雷諾數()下均適用之平均局部粒子紐塞數(與()之經驗修正式。

This study will develop a porous heat absorber used in the thermoelectric generator for the vchicle engine waste heat recovery.The high performance of the porous heat absorber may enhance the generating electricity of the thermoelectric generator.Hence,the heat transfer characteristics in the asymmetrically heated rectangular channels fully filled with porous materials will be investigated experimentally.Air was used as the coolant.The porous materials were packed by brass beads with average diameters(d) of 2,4 and 6 mm.The channel width (W)was fixed to be 60 mm.Variable parameters were the relative length of packed channel(L/d=5~60),the relative height of packed channel (H/d=1.67~15) and the Reynolds number (ReD=755~7921 and Redp=38~2703).The results indicated that the bead diameter(d),rather than the hydraulic diameter (Dh),may be a proper parabeter to generalize the data for heat transfer in a packed channel.Besides,the particle Nusselt number(Nudp)increased wih decreasing L/d,while the H/d was not sensitive to Nudp.Finally,the correlation of average and local particle Nusselt numbers(Nudp and Nudp.x)for various L/d,H/d and Redp were provided.

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