In this study,the primary objective was to enhance the hydrothermal performance of a dimpled tube by addressing areas with low heat transfer compared to other regions.To accomplish this,a comprehensive numerical inves...In this study,the primary objective was to enhance the hydrothermal performance of a dimpled tube by addressing areas with low heat transfer compared to other regions.To accomplish this,a comprehensive numerical investigation was conducted using ANSYS Fluent 2022 R1 software,focusing on different diameters of dimples along the pipe’s length and the distribution of dimples in both in-line and staggered arrangements.The simulations utilized the finite elementmethod to address turbulent flowwithin the tube by solving partial differential equations,encompassing Re numbers spanning from 3000 to 8000.The study specifically examined single-phase flow conditions,with water utilized as the cooling fluid.The results of the investigation indicated that increasing the Reynolds number resulted in higher average Nusselt numbers,pressure drops,the overall performance criterion,and a reduction in average thermal resistance across all models analyzed.Notably,both proposedmodels demonstrated improved heat transfer when compared to the conventional model.Out of all the models evaluated,the tube featuring staggered dimples(Model B)demonstrated the most notable improvement in the Nu number.It exhibited an enhancement of approximately twice the value compared to the conventional model.The mean thermal resistance for the tube with dimples in the staggered arrangement(Model B)is 0.0057 k/W,compared to 0.0118 k/W for the traditional model.The maximum overall performance criterion for Model-A-and Model-Bis 1.22 and 1.33,respectively.展开更多
Heat transfer enhancement in vertical tubes plays an important role on the thermal performance of many heat exchangers and thermal devices.In this work,laminar mixed convection of airflow in a vertical dimpled tube wa...Heat transfer enhancement in vertical tubes plays an important role on the thermal performance of many heat exchangers and thermal devices.In this work,laminar mixed convection of airflow in a vertical dimpled tube was numerically investigated.Three-dimensional elliptical governing equations were solved using the finite-volume technique.For a given dimpled pitch,the effects of three different dimple heights(h/D=0.013,0.027,0.037) have been studied at different Richardson numbers(0.1,1.0 and 1.5).The generated vortex in the vicinity of the dimple destructs the thermal boundary layer and enhances the heat transfer.Therefore,lower wall temperature is seen where the dimples are located.Fluid flow velocity at the near-wall region significantly increases because of buoyancy forces with the increase of Richardson numbers.Such an acceleration at the near-wall region makes the dimples more effective at higher Richardson number.Using a dimpled tube enhances the heat transfer coefficient.However,the pressure drop is not important.For instance,in the case of Ri=1.5 and h/D=0.037,20% gains in the heat transfer enhancement only costs2.5% in the pressure loss.In general,it is recommended using a dimpled tube where the effects of buoyancy forces are important.展开更多
文摘In this study,the primary objective was to enhance the hydrothermal performance of a dimpled tube by addressing areas with low heat transfer compared to other regions.To accomplish this,a comprehensive numerical investigation was conducted using ANSYS Fluent 2022 R1 software,focusing on different diameters of dimples along the pipe’s length and the distribution of dimples in both in-line and staggered arrangements.The simulations utilized the finite elementmethod to address turbulent flowwithin the tube by solving partial differential equations,encompassing Re numbers spanning from 3000 to 8000.The study specifically examined single-phase flow conditions,with water utilized as the cooling fluid.The results of the investigation indicated that increasing the Reynolds number resulted in higher average Nusselt numbers,pressure drops,the overall performance criterion,and a reduction in average thermal resistance across all models analyzed.Notably,both proposedmodels demonstrated improved heat transfer when compared to the conventional model.Out of all the models evaluated,the tube featuring staggered dimples(Model B)demonstrated the most notable improvement in the Nu number.It exhibited an enhancement of approximately twice the value compared to the conventional model.The mean thermal resistance for the tube with dimples in the staggered arrangement(Model B)is 0.0057 k/W,compared to 0.0118 k/W for the traditional model.The maximum overall performance criterion for Model-A-and Model-Bis 1.22 and 1.33,respectively.
文摘Heat transfer enhancement in vertical tubes plays an important role on the thermal performance of many heat exchangers and thermal devices.In this work,laminar mixed convection of airflow in a vertical dimpled tube was numerically investigated.Three-dimensional elliptical governing equations were solved using the finite-volume technique.For a given dimpled pitch,the effects of three different dimple heights(h/D=0.013,0.027,0.037) have been studied at different Richardson numbers(0.1,1.0 and 1.5).The generated vortex in the vicinity of the dimple destructs the thermal boundary layer and enhances the heat transfer.Therefore,lower wall temperature is seen where the dimples are located.Fluid flow velocity at the near-wall region significantly increases because of buoyancy forces with the increase of Richardson numbers.Such an acceleration at the near-wall region makes the dimples more effective at higher Richardson number.Using a dimpled tube enhances the heat transfer coefficient.However,the pressure drop is not important.For instance,in the case of Ri=1.5 and h/D=0.037,20% gains in the heat transfer enhancement only costs2.5% in the pressure loss.In general,it is recommended using a dimpled tube where the effects of buoyancy forces are important.
