Heat flow visualization during mixed convection within entrapped porous triangular cavities with moving horizontal walls via heatline analysis

2017 ◽  
Vol 108 ◽  
pp. 468-489 ◽  
Author(s):  
Monisha Roy ◽  
Pratibha Biswal ◽  
S. Roy ◽  
Tanmay Basak
Keyword(s):  
Heat Flow ◽  
Mixed Convection ◽  
Flow Visualization

scholarly journals Optimisation of the Geometric Parameters of Longitudinally Finned Air Cooler Tubes Operating in Mixed Convection Conditions

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 111
Author(s):  
Piotr Kopeć ◽  
Beata Niezgoda-Żelasko
Keyword(s):  
Heat Flow ◽  
Mixed Convection ◽  
Optimal Solution ◽  
Finned Tube ◽  
Geometric Parameters ◽  
Maximum Efficiency ◽  
Minimum Mass ◽  
Maximum Heat ◽  
Air Cooler ◽  
Finned Surface

The results of optimisation calculations presented in the article are related to longitudinally finned tubes of a heat pump evaporator operating under natural wind-induced flow of outdoor air conditions. The finned surface is characterised by an unusual, wavy fin shape. The article presents the methodology applied to seeking optimal geometric parameters of the finned tube in which thermal calculations were performed by modelling a mixed convection process on the finned surface using the finite volume method. In the case of maximising the heat flow with the minimum mass of the fins, the optimal solution was dominated by the minimum mass of the fins and thus geometric parameters correspond to the number of fins n = 6, fin height h = 0.065 and fin thickness s = 0.0015 m. Optimisation calculations made for maximum efficiency of the exchanger at constant mass indicated that the tube with ten fins (n = 10) with a height of h = 0.11 m and a thickness of s = 0.0018 m allowed maximum heat flow at the assumed mass of the fins in the exchanger tube model. The article proposes a simplified method of determining the optimal geometric parameters of the profile for any mass and maximum thermal efficiency.

Numerical heat flow visualization analysis on enhanced thermal processing for various shapes of containers during thermal convection

2019 ◽  
Vol 30 (7) ◽  
pp. 3535-3583 ◽  
Author(s):  
Leo Lukose ◽  
Tanmay Basak
Keyword(s):  
Finite Element ◽  
Heat Flow ◽  
Flow Visualization ◽  
Thermal Processing ◽  
Bottom Wall ◽  
Heat Distribution ◽  
Content Type ◽  
Class 1

Purpose The purpose of this paper is to study thermal (natural) convection in nine different containers involving the same area (area= 1 sq. unit) and identical heat input at the bottom wall (isothermal/sinusoidal heating). Containers are categorized into three classes based on geometric configurations [Class 1 (square, tilted square and parallelogram), Class 2 (trapezoidal type 1, trapezoidal type 2 and triangle) and Class 3 (convex, concave and triangle with curved hypotenuse)]. Design/methodology/approach The governing equations are solved by using the Galerkin finite element method for various processing fluids (Pr = 0.025 and 155) and Rayleigh numbers (103 ≤ Ra ≤ 105) involving nine different containers. Finite element-based heat flow visualization via heatlines has been adopted to study heat distribution at various sections. Average Nusselt number at the bottom wall ( Nub¯) and spatially average temperature (θ^) have also been calculated based on finite element basis functions. Findings Based on enhanced heating criteria (higher Nub¯ and higher θ^), the containers are preferred as follows, Class 1: square and parallelogram, Class 2: trapezoidal type 1 and trapezoidal type 2 and Class 3: convex (higher θ^) and concave (higher Nub¯). Practical implications The comparison of heat flow distributions and isotherms in nine containers gives a clear perspective for choosing appropriate containers at various process parameters (Pr and Ra). The results for current work may be useful to obtain enhancement of the thermal processing rate in various process industries. Originality/value Heatlines provide a complete understanding of heat flow path and heat distribution within nine containers. Various cold zones and thermal mixing zones have been highlighted and these zones are found to be altered with various shapes of containers. The importance of containers with curved walls for enhanced thermal processing rate is clearly established.

Experimental Analysis of Opposing Flow in Mixed Convection in a Channel With an Open Cavity Below

2005 ◽  
Author(s):  
Oronzio Manca ◽  
Sergio Nardini ◽  
Kambiz Vafai
Keyword(s):  
Reynolds Number ◽  
Mixed Convection ◽  
Flow Visualization ◽  
Vortex Structure ◽  
Open Cavity ◽  
Forced Flow ◽  
Heated Wall ◽  
Heated Plate ◽  
Thermal Plume ◽  
Recirculation Flow

In this paper mixed convection in an open cavity with a heated wall bounded by a horizontal unheated plate is investigated experimentally. The cavity has the heated wall on the opposite side of the forced inflow. The results are reported in terms of wall temperature profiles of the heated wall and flow visualization for Reynolds number (Re) from 100 to 2000 and Richardson number (Ri) in the range 4.3–6400; the ratio between the length and the height of cavity (L/D) is in the range 0.5–2.0 and the ratio between the channel and cavity height (H/D) is equal to 1.0. The present results show that at the lowest investigated Reynolds number the surface temperatures are lower than the corresponding surface temperature for Re = 2000, at same the ohmic heat flux. The flow visualization points out that for Re = 1000 there are two nearly distinct fluid motions: a parallel forced flow in the channel and a recirculation flow inside the cavity. For Re = 100 the effect of a stronger buoyancy determines a penetration of thermal plume from the heated plate wall into the upper channel. Moreover, the flow visualization points out that for lower Reynolds numbers the forced motion penetrates inside the cavity and a vortex structure is adjacent to the unheated vertical plate. At higher Reynolds number the vortex structure has a larger extension at same L/D value.

Role of heatlines on thermal management during Rayleigh-Bénard heating within enclosures with concave/convex horizontal walls

2017 ◽  
Vol 27 (9) ◽  
pp. 2070-2104 ◽  
Author(s):  
Pratibha Biswal ◽  
Tanmay Basak
Keyword(s):  
Heat Flow ◽  
Flow Visualization ◽  
Numerical Solutions ◽  
Fluid Velocity ◽  
Content Type ◽  
Bénard Convection ◽  
Benard Convection ◽  
First Time ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Purpose This study aims to carry out the analysis of Rayleigh-Bénard convection within enclosures with curved isothermal walls, with the special implication on the heat flow visualization via the heatline approach. Design/methodology/approach The Galerkin finite element method has been used to obtain the numerical solutions in terms of the streamlines (ψ ), heatlines (Π), isotherms (θ), local and average Nusselt number ( Nut¯) for various Rayleigh numbers (103 ≤ Ra ≥ 105), Prandtl numbers (Pr = 0.015 and 7.2) and wall curvatures (concavity/convexity). Findings The presence of the larger fluid velocity within the curved cavities resulted in the larger heat transfer rates and thermal mixing compared to the square cavity. Case 3 (high concavity) exhibits the largest Nut¯ at the low Ra for all Pr. At the high Ra, Nut¯ is the largest for Case 3 (high concavity) at Pr = 0.015, whereas at Pr = 7.2, Nut¯ is the largest for Case 1 (high concavity and convexity). Practical implications The results may be useful for the material processing applications. Originality/value The study of Rayleigh-Bénard convection in cavities with the curved isothermal walls is not carried out till date. The heatline approach is used for the heat flow visualization during Rayleigh-Benard convection within the curved walled enclosures for the first time. Also, the existence of the enhanced fluid and heat circulation cells within the curved walled cavities during Rayleigh-Benard heating is illustrated for the first time.

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