A forced convection heat transfer in ducts (circular, triangular, rectangular) cross sections and (1m) length with hydraulic diameter (0.1m) filled with porous media (glass spheres 12 mm diameter) is investigated experimentally at constant heat flux from the wall (1070W/m²) with Reynolds number range of (12461-2500). Comparison was made between three ducts for local temperature distribution and local Nusselt number). The experimental results showed the effect of Reynolds number and cross section on the temperature profile and local Nusselt number,also empirical correlations for average Nusselt number and Peclet number were obtained for three ducts.
This prospective study was designed to experimentally investigate the effects of inserting copper mesh in fully developed turbulent flow on the flow and heat transfer characteristics. Experimental work includes designing and manufacturing the test section of rectangular duct with dimensions of (30*3*40 cm) with aspect ratio and hydraulic diameter of 10 and 5.45 mm respectively. A constant heat flux ranged (1.5*102 – 1.8*102 W/m2) was applied to the lower surface of duct with Reynolds number range (3.3*104 – 4.8*104). The porosity rang of (0.98 – 0.99). Also, the effects of porous height ratio (full and partial filling) were considered and considered air as working fluid. The results indicate that inserting mesh wire leads to enhance heat transfer coefficient and increase pressure drop. Taken together, these results show that the obtained values of performance enhancement criteria (PEC) ranged (1.01 -1.98 ), the enhancement in heat transfer coefficient is 315% duo to wire mesh insert. Also, from obtained results empirical correlation for friction factor and Nusselt number were suggested.
An experimental and theoretical study of free convection heat transfer for a cylinder placed in an iron test section of dimensions (0.2x0.2x0.2 m3), the test section filled with saturated porous material glass balls (5 mm), and the air is the working fluid with Raleigh number (7692.6 ≤ Ra ≤ 17654). The circular cylinder heater (D = 0.015 m, L = 0.2 m) is heated electrically, made of Copper and located in different positions (in X & Y direction). The theoretical part includes solving the free convection heat transfer using the ANSYS program (fluent). The experimental and theoretical results showed that the surface temperature values around the cylinder perimeter when changing its position within the test section are changing as moving up and down where the effect of buoyancy force appears. The maximum difference between the upper and lower position at the experimental result is 7.22%, and the average Nusselt number increases with Raleigh number and heat flux. Also, the experimental results showed that the use of porous material significantly improves the heat transfer by 48.6%. The maximum percentage change between the experimental and theoretical results is 5.46%. Moreover, experimental correlations were achieved, and a comparison was performed between the present results with the previous studies and it gives a good agreement.
This work presents experimental investigation of flow and heat transfer characteristics for entry length of turbulent flow in a rectangular duct fitted with porous media and air as the working fluid. Rectangular duct (300×30 mm) with a hydraulic diameter (54.54 mm) was subjected to constant heat flux from lower surface (1.5 ×102 –1.8 ×102 w/m2) and Reynolds number ranged (3.3x104 up to 4.8x104). Copper mesh inserts (as porous media) with screen diameter (54.5 mm) for vary distance between two adjacent screens of (10 mm), (15 mm) and (20 mm) in the porosity range of (0.98 - 0.99) are considered for experimentation. The effect of porous height ratio (full and partial) are also considered. It is observed that the enhancement of heat transfer by using mesh inserts when compared to a plain surface is more by a factor of (2.2) times where the skin fraction coefficient is about (5) times. An Empirical correlation for Nusselt number and friction factor are developed for the mesh inserts from the obtained results.
Estimating the heat loss encountered in many situations with a hot surface buried in a permeable material greatly contributes to the energy conservation and cost analysis of numerous engineering systems. An experimental study was conducted on the natural convection heat transfer from a triangular prism positioned in a 0.2 m2 test section filled by 3 mm glass spheres as a porous material. The air is the working fluid used in the study with the Darcy-Raleigh number (0.1224≤ Ra* ≤ 0.2712). The triangular prism heater (having face side (c) = 0.026 m and L = 0.2 m) is made of copper that is heated electrically and immersed in the porous material at three different depth to radius ratios (h/R=3.5, 10, and 16.5). The results manifested that the peripheral surface temperature around the triangular prism rises with a rise in the h/R ratio and an increase in the heat flux. The mean Nusselt number is proportional to the heat flux and Darcy-Raleigh number. Empirical correlations were obtained from the experimental results, and the differences between measured and estimated values never exceeded ∓ 2.7.
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