مطالعه عددي اثر دوران مانع مخروطي بر انتقال حرارت و جريان سيال در لوله مبدل حرارتي

Numerical study of the effect of rotating conical obstacle on heat transfer and fluid flow in a heat exchanger tube

ﺑﺮرﺳﻲ روشﻫﺎي اﻓﺰاﻳﺶ اﻧﺘﻘﺎل ﺣﺮارت در ﻣﺒﺪلﻫﺎي ﺣﺮارﺗﻲ در ﻃﻮل ﺳﺎلﻫﺎي ﮔﺬﺷﺘﻪ ﺑﻪ ﺧﺎﻃﺮ اﻫﻤﻴﺖ ﻣﻮﺿﻮع در ﺑﻬﻴﻨﻪﺳﺎزي و ﻛﺎﻫﺶ اﺛﺮات ﻣﺨﺮب زﻳﺴﺖﻣﺤﻴﻄﻲ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﻗﺮار ﮔﺮﻓﺘﻪ و ﻣﻮاﻧﻊ ﺑﺎ ﺷﻜﻞ ﻫﺎي ﻣﺨﺘﻠﻔﻲ ﺟﻬﺖ رﺳﻴﺪن ﺑﻪ ﺿﺮﻳﺐ ﻋﻤﻠﻜﺮد ﺣﺮارﺗﻲ ﺑﺎﻻﺗﺮ ﭘﻴﺸﻨﻬﺎد ﺷﺪه اﺳﺖ ﻟﺬا در ﻣﻄﺎﻟﻌﻪ ﺣﺎﺿﺮ اﺛﺮ دوران ﻣﺎﻧﻊ ﻣﺨﺮوﻃﻲ ﺑﺮ اﻧﺘﻘﺎل ﺣﺮارت درﻣﺤﺪوده ﻋﺪد رﻳﻨﻮﻟﺪز 4000 ﺗﺎ 24000 در داﺧﻞ ﻟﻮﻟﻪ ﺑﻪ ﻋﻨﻮان ﻳﻚ ﻣﻮﺿﻮع ﺟﺪﻳﺪ ﺑﺮرﺳﻲ ﻣﻲﮔﺮدد. ﺷﺒﻴﻪ ﺳﺎزي ﻋﺪدي ﺑﻪ ﺻﻮرت ﺳﻪ ﺑﻌﺪي و ﺑﺎ اﺳﺘﻔﺎده از ﻧﺮم اﻓﺰار اﻧﺴﻴﺲ ﻓﻠﻮﺋﻨﺖ اﻧﺠﺎم ﺷﺪه اﺳﺖ. ﻣﻘﺎﻳﺴﻪ ﻧﺘﺎﻳﺞ ﺑﻪ دﺳﺖ آﻣﺪه ﺑﺮاي ﻟﻮﻟﻪ ﺻﺎف و ﻫﻤﭽﻨﻴﻦ ﺗﺤﺮﻳﻚ ﺑﺎ ﻣﺎﻧﻊ ﻣﺨﺮوﻃﻲ ﺑﺎ ﻧﺘﺎﻳﺞ ﺳﺎﻳﺮ ﻣﺤﻘﻘﻴﻦ ﺗﻄﺎﺑﻖ ﺧﻮﺑﻲ ﻧﺸﺎن ﻣﻴﺪﻫﺪ. ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﻧﺘﺎﻳﺞ، اﻧﺘﻘﺎل ﺣﺮارت در ﺣﺪود 2/2–3/9 ﺑﺮاﺑﺮ در ﻣﻘﺎﻳﺴﻪ ﺑﺎ ﻟﻮﻟﻪ ﺳﺎده اﻓﺰاﻳﺶ ﻳﺎﻓﺘﻪ و ﻋﻤﻠﻜﺮد ﻛﻠﻲ اﻧﺘﻘﺎل ﺣﺮارت در ﻣﺤﺪوده 1/5-0/8 اﺳﺖ. ﻫﻤﭽﻨﻴﻦ ﺑﻴﺸﺘﺮﻳﻦ ﻣﻘﺪار اﻓﺰاﻳﺶ ﺿﺮﻳﺐ ﻋﻤﻠﻜﺮد ﺣﺮارﺗﻲ در اﺛﺮ دوران ﻣﺎﻧﻊ ﻧﺴﺒﺖ ﺑﻪ ﻣﺎﻧﻊ ﺛﺎﺑﺖ، 120% ﺛﺒﺖ ﮔﺮدﻳﺪ.

In the present numerical study, the effect of conical obstacle on heat transfer and pressure drop in turbulent flow inside a tube is investigated. Although the effect of different stationary obstacles on heat transfer and pressure drop has been investigated so far, the use of the rotating obstacle is a new issue. Rotating obstacles create powerful rotating flow and increase flow turbulence and vortices through the effective displacement of the fluid particles affects the heat transfer rate. Therefore, the present research investigates the effect of cone obstacle rotation speeds of 25, 50, 75, 100 on the flow characteristics and thermal performance coefficients of the shell-and-tube heat exchanger in the Reynolds number range 4000 to 24000. The results show that for all Reynolds numbers in rotational speed 50 rpm, the heat transfer coefficient reaches its maximum value, and no significant change is observed, with increasing rotational speed. Heat transfer is about 2.2-2.9 times increased compared to smooth pipe and the thermal coefficient performance is in the range of 0.5-1.8. The maximum thermal performance coefficients, using rotating obstacle in comparison to the obstacle stationary one, is 120%.