Another confirmation that counter-current logarithmic mean is upper bound and a note on approximations

详细信息    查看全文

• 作者：Ahmed I.A. Salama ; ^{ahmed.salama@nrcan-rncan.gc.ca} ; ^{salama@nrcan.gc.ca}
• 关键词：Co-current HEX ; Counter-current HEX ; Heat exchanger (HEX) ; Heat exchanger network (HEN) ; HEN analysis ; HEN synthesis ; HEN optimization ; Logarithmic-mean-temperature-difference (LMTD) method ; Logarithmic-mean-temperature-difference (¦¤TLM) ; Minimum rule (M
• 刊名：Computers and Chemical Engineering
• 出版年：2013
• 出版时间：10 January, 2013
• 年：2013
• 卷：48
• 期：Complete
• 页码：154-164
• 全文大小：1225 K

文摘

The paper presents modifications on published demonstration that the counter-current logarithmic-mean-temperature-difference (¦¤T_LM) is upper bound compared with the co-current ¦¤T_LM. In the published demonstration, an approach was proposed but it suffered from wrong assumption. In this paper, corrections to the wrong assumption and a property of a curve derived from the ¦¤T_LM curve have been used to propose another demonstration that counter-current ¦¤T_LM is upper bound. Optimization problems have been formulated to verify the proposed developments and demonstrate the results obtained.

A class of ¦¤T_LM approximations including two accurate approximations proposed by the author are discussed. The selected approximations are designated as Underwood's class. This class generates accurate results over the problem temperature-difference-ratio range and has the advantage of direct use of the heat exchanger (HEX) terminal temperature differences.