An Experimental Study on Heat Transfer Enhancement for Porous Heat Exchange in Rectangular Duct

Abstract

Forced convection heat transfer of air in porous rectangular duct was investigated experimentally. The pad consist of (zig-zag) metallic wire mesh insert with two different porosities () namely (0.97) and (0.99) .The experiments were carried out for Reynolds number (7682,12497 and 17323) and constant heat flux (192,297 and 422 W/m 2) .The results indicated that Nusselt number was increased with increasing Reynolds number and heat flux but decreased with increasing pad porosity .The Nusselt number in the porous duct was increased up to (144%) for (=0.97) and (72%) for (=0.99) when compared to clear duct at the same tested condition. For optimization between heat transfer enhancement and pad weight added into clear duct , it is found that [ (Nu porous-Nu clear) / weight of pad ] equal to (84.34) and (40.49) for (=0.99 and =0.97) respectively and this is good improvement in heat transfer through porous rectangular duct and reducing size and weight of original duct. Keywords: Porous rectangular duct , Heat transfer , Wire mesh insert. ‫دراﺳﺔ‬ ‫ﻣﺴﺎﻣﻲ‬ ‫ﺣﺮاري‬ ‫ﻟﺘﺒﺎدل‬ ‫اﻟﺤﺮارة‬ ‫اﻧﺘﻘﺎل‬ ‫ﻟﺰﯾﺎدة‬ ‫ﺗﺠﺮﯾﺒﯿﺔ‬ ‫ﻓﻲ‬ ‫ﻣﺴﺘﻄﯿﻞ‬ ‫ﻣﺠﺮى‬ ‫اﻟﻤﻘﻄﻊ‬ ‫اﻟﺨﻼﺻﺔ‬ ‫دراﺳﺘﮫ‬ ‫ﺗﻢ‬ ‫اﻟﻤﻘﻄﻊ‬ ‫ﻣﺴﺘﻄﯿﻞ‬ ‫ﻣﺴﺎﻣﻲ‬ ‫ﻣﺠﺮى‬ ‫ﺧﻼل‬ ‫اﻟﻤﺎر‬ ‫ﻟﻠﮭﻮاء‬ ‫اﻟﻘﺴﺮي‬ ‫ﺑﺎﻟﺤﻤﻞ‬ ‫اﻟﺤﺮارة‬ ‫اﻧﺘﻘﺎل‬ ‫اﻟﺒﺤﺚ‬ ‫ھﺬا‬ ‫ﻓﻲ‬ ‫ﻋﻤﻠﯿﺎ‬. ‫ﻣﻦ‬ ‫اﻟﺤﺸﻮة‬ ‫ﺗﺘﻜﻮن‬ ‫ﻣ‬ ‫ﻣ‬ ‫ﻣﻌﺪﻧﻲ‬ ‫ﺳﻠﻜﻲ‬ ‫ﺸﺒﻚ‬ ‫ﺘ‬ ‫ﺑﯿﻦ‬ ‫ﺗﺘﺮاوح‬ ‫ﺑﻤﺴﺎﻣﯿﺔ‬ ‫ﻌﺮج‬) 0.97 ، 0.99. (‫رﯾﻨﻮﻟﺪز‬ ‫ﻟﺮﻗﻢ‬ ‫اﻟﺘﺠﺎرب‬ ‫اﺟﺮﯾﺖ‬ Re) () 17323 , 12497 , 7682 (‫ﺣﺮاري‬ ‫وﻓﯿﺾ‬ ‫ﺛﺎﺑﺖ‬) q () 422 , 297 , 192 ‫واط‬ / ‫م‬ 2. (‫ﻧﺴﻠﺖ‬ ‫رﻗﻢ‬ ‫ان‬ ‫اﻟﻨﺘﺎﺋﺞ‬ ‫ﺑﯿﻨﺖ‬) Nu (‫رﻗﻢ‬ ‫ﺑﺰﯾﺎدة‬ ‫ﯾﺰداد‬ ‫رﯾﻨﻮﻟﺪز‬) Re (‫اﻟﺤﺮاري‬ ‫واﻟﻔﯿﺾ‬) q (‫اﻟﺤﺸﻮة‬ ‫ﻣﺴﺎﻣﯿﺔ‬ ‫ﺑﺰﯾﺎدة‬ ‫ﯾﻘﻞ‬ ‫وﻟﻜﻦ‬). (‫ﻟﻠﻤﺠﺮى‬ ‫ﻧﺴﻠﺖ‬ ‫رﻗﻢ‬ ‫ﺑﻤﻘﺪار‬ ‫ﯾﺰداد‬ ‫اﻟﻤﺴﺎﻣﻲ‬) 144 % (‫ﻋﻨﺪ‬) =0.97 (‫و‬) 72 % (‫ﻋﻨﺪ‬) =0.99 (‫ﻣﻘﺎرﻧﺘﮫ‬ ‫ﻋﻨﺪ‬ ‫اﻧﺘﻘﺎل‬ ‫ﻓﻲ‬ ‫اﻟﺰﯾﺎدة‬ ‫ﺑﯿﻦ‬ ‫اﻟﻤﻔﺎﺿﻠﺔ‬ ‫وﻣﻦ‬ ‫اﻟﺘﺸﻐﯿﻠﯿﺔ‬ ‫اﻟﻈﺮوف‬ ‫ﻧﻔﺲ‬ ‫ﻋﻨﺪ‬ ‫اﻟﺤﺸﻮة‬ ‫ﻣﻦ‬ ‫اﻟﺨﺎﻟﻲ‬ ‫اﻟﻤﺠﺮى‬ ‫ﻣﻊ‬ ‫ان‬ ‫وﺟﺪ‬ ، ‫اﻟﺨﺎﻟﻲ‬ ‫اﻟﻤﺠﺮى‬ ‫اﻟﻰ‬ ‫اﻟﻤﻀﺎﻓﺔ‬ ‫اﻟﺤﺸﻮة‬ ‫ووزن‬ ‫اﻟﺤﺮارة‬)] Nu ‫ﺧﺎﻟﻲ‬-Nu ‫ﻣﺴﺎﻣﻲ‬ / (‫اﻟﺤﺸﻮة‬ ‫وزن‬ ‫اﻟﻤﻀﺎﻓﺔ‬ [ ‫ﯾﺴﺎوي‬) 84.34 (‫و‬) 40.49 (‫ﻣﺴﺎﻣﯿﺔ‬ ‫ﻋﻨﺪ‬) 0.99 (‫و‬) 0.97 (‫اﻟﺘﻮاﻟﻲ‬ ‫ﻋﻠﻰ‬ ‫و‬ ‫ﯾﻌﺘﺒﺮ‬ ‫ھﺬا‬