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The cross flow over the tube bank is extensively employed in the heat exchangers. The present study investigates the heat transfer and frictional losses of cross flowtube bank with solid and perforated splitter plates. The experimental data are collected for bare tube bank, tube bank with solid and perforated splitter plate by varying the splitter plate width ratio (Rw) and the perforation index (Pi) in the Reynolds number range of 10,500-40,500. The cylindrical tube bank with perforated splitter plate having (Rw) of 0.5 and (Pi) of 1.5 yields maximum thermal and hydraulic performance. [ABSTRACT FROM AUTHOR]

In the present research work, heat transfer and friction characteristics of in-line elliptical tubes are studied experimentally and numerically with the aiming to enhanced the thermal performance. The elliptical tubes with an aspect ratio (AR) of 0.35 and 0.50 and with circular tubes of the aspect ratio of 1 are selected for Reynolds number (Re) ranging from 5000 to 21000. The results indicate that the elliptical tube shows higher heat transfer rate with a significant reduction in the friction factor for the entire range of Reynolds number. The superior performance of the elliptical tube is often due to the aerodynamic cross-section profile of the tubes which promotes better heat transfer with a reduction in the frontal area of the tubes. The study is performed for the two different pitch to major axis ratios (PR) of 1.25 and 1.5, respectively. The results show that at a pitch ratio of 1.25 the elliptical tube with an aspect ratio of 0.50 leads to the superior heat transfer rate, while at pitch ratio of 1.50 elliptic tubes with an aspect ratio of 0.35 indicate better thermo-hydraulic efficiency relative to 0.50. [ABSTRACT FROM AUTHOR]

Heat transfer enhancement in heat exchanger by using passive approach has become a very versatile area of research for the researchers. Although very significant results has been achieved in the thermal performance of heat exchangers, especially in the range of lower Reynolds number, but still these passive approaches of heat transfer enhancement is not effective for the range of higher Reynolds number. In the present work the effect of 'perforated circular disk turbulators with and without twisted tape', on heat transfer, friction factor and thermal performance of heat exchanger is evaluated experimentally. The different geometrical parameters used for the experiment include fixed diameter ratio (0. 8), pitch ratios (1, 2, and 3), perforation index (0%, 8%, 16%, and 24%), fixed twist ratio (2) and fixed width ratio (0.4). The experiment is done in the range of Reynolds number lying from 6,500 to 26,500. On the basis of experimental observation, there is 2.2–3.54 times improvement in heat transfer and around 1.18–1.64 times improvement in thermal performance factor over smooth tube heat exchanger. [ABSTRACT FROM AUTHOR]

An experimental investigation has been carried out to study the effect of heat transfer and friction characteristics of air passing through a rectangular duct which is roughened by V-down perforated baffles. The experiment encompassed Reynolds number (Re) from 3800 to 19,000, relative roughness height (e/H) values of 0.285–0.6, relative roughness pitch (P/e) range of 1–4 and open area ratio values from 12% to 44%. The effect of roughness parameters on Nusselt number (Nu) and friction factor (f) has been determined and increase in heat transfer and friction loss has been observed for ducts having a roughened test plate. Maximum Nusselt number is observed for the relative roughness pitch ranging from 1.5 to 3 for flow and geometrical parameters under consideration. The experimental data have been used to develop Nusselt number and friction factor correlations as a function of roughness and flow parameters. [ABSTRACT FROM AUTHOR]

An experimental investigation has been carried out to study the heat transfer and friction factor characteristics of a V-down-perforated baffled roughened solar air heater duct. The roughened wall was uniformly heated and the rest three walls of the duct were kept insulated. Measurements have been carried out for the duct aspect ratio of 10, Reynolds number range of 3800–19,000, relative hole position range of 0.429–0.571, relative roughness pitch range of 2–4, and open area ratio range of 12–44%. The relative roughness height of 0.4 and angle of attack of 60° are kept constant during the entire experimentation. The heat transfer and friction factor data obtained were compared with the data obtained from a smooth duct under similar operating conditions. In comparison to the smooth duct the V-shaped perforated baffle roughened duct enhanced the Nusselt number and friction factor by 2.57 and 5.96 times, respectively. The thermohydraulic performance parameter is found superior for the open area ratio of 24% and relative roughness pitch of 2.5. [ABSTRACT FROM PUBLISHER]

A numerical investigation has been carried out for a range of flow and geometrical parameters in order to analyze the effect of transverse perforated baffles attached on the heated wall of rectangular duct on heat transfer and friction factor. An increase in heat transfer and friction loss over a smooth surface has been observed for duct having perforated baffles as a roughness element. Numerical results have been used to develop the Nusselt number and friction factor correlations as a function of flow and geometrical parameters for predicting performance of the system having investigated the type of roughness elements. [ABSTRACT FROM AUTHOR]

This paper presents results of a study of the performance of solar air heaters with V down perforated baffles as roughness on the air flow side of the absorber plate. Investigations have been carried out using a mathematical model to study the effects of ambient conditions, operating and design parameters on effective efficiency of such air heaters. The thermal and effective efficiencies differ only marginally at lower flow rates. With an increase in the flow rate, the difference between the thermal and effective efficiencies increases because of the increase in the pumping power. The results of the study are presented in the form of plots to show the effect of ambient, design and operating conditions on thermal and effective efficiency. [ABSTRACT FROM AUTHOR]