本文以實驗方法與數值逆算法來預測於不同鰭片間距及外界風速下，四支圓管為同線排列與交錯排列之板鰭管式熱交換器的平均熱傳係數與等溫平均熱傳係數。此四支圓管可能有不同的溫度，因此鰭片上之熱傳係數可能為不均勻分佈，故於進行數值逆算法之前，整個鰭片將先被分割成數個小區域，且每個小區域上之平均熱傳係數假設為一未知的常數。而後，本文以有限差分法配合最小平方法、外界空氣溫度量測值及鰭片溫度量測值之逆算法來求得本文結果。結果顯示於自然對流條件下，平均熱傳係數及等溫平均熱傳係數會隨著鰭片間距增加而增加，並且會逐漸趨近某一固定值。於強迫對流條件下，平均熱傳係數及等溫平均熱傳係數會隨著外界風速及鰭片間距的增加而增加。其他重要的發現為於第二排圓管後方之小區域的熱傳係數一般皆會比其他區域的值低，此乃由於此下游區域會有低速的尾流區發生所致。另外，交錯排列之板鰭管式熱交換器的平均熱傳係數及等溫平均熱傳係數均較同線排列的高，此意味著交錯排列之板鰭管式熱交換器具有較佳的散熱效果。為了證明本文結果之可靠性，本文之等溫平均熱傳係數值將與目前存在之經驗公式或商業計算流體力學軟體所求得之結果相比較。此外，本文也利用商用軟體Icepak配合本文之實驗數據來求得鰭片間之流場流動情形及鰭片上各量測點的溫度值。

The present study applies the experimental and numerical inverse methods to predict the average heat transfer coefficient and heat transfer coefficient under the isothermal situation on a vertical square fin of the four-tube plate finned-tube heat exchangers for in-line and staggered arrangements and various fin spacings and air velocities. These tubes may not have the same temperature in the present study. Due to the non-uniform distribution of the heat transfer coefficient, the whole plate fin is divided into several sub-fin regions before performing the inverse scheme, and the average heat transfer coefficient on each sub-fin region is assumed to be unknown. Later, the inverse scheme of the finite difference method in conjunction with the Least squares scheme and experimental measured temperatures is applied to determine the present results. Results show that the average heat transfer coefficient and isothermal heat transfer coefficient in nature convection increase with increasing the fin spacing. These values can respectively approach their corresponding asymptotic values obtained from a single square fin as fin spacing grow to infinity. However, the average heat transfer coefficient and isothermal heat transfer coefficient in force convection increase with increasing the fin spacing and air velocity. Other important findings are that the average heat transfer coefficients in the upstream and wake fin regions of the second row may be generally lower than those on other sub-fin regions. It must be noted that the staggered arrangement exhibits higher average heat transfer coefficient than the in-line. This implies that the staggered plate finned-tube heat exchangers have a better heat dissipation. In order to validate the accuracy and reliability of the present results, the isothermal heat transfer coefficient values are compared with those obtained from the existing correlations or computational fluid dynamics commercial code. Besides, the present study also applies the commercial software, Icepak, in conjunction with the present experimental data to obtain the inter-fin flow field of the plate finned-tube heat exchanger and temperature measurements at various measurement locations of the fin.

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