Experimental Analysis of Louvered Rectangular Leaf Type Inserts in a Circular Pipe to Enhance Heat Transfer Coefficient
01 Jan 2020-pp 933-950
TL;DR: In this article, the authors used aluminum inserts at different angles of 30°, 45°, 60°, 90°, and 90° to enhance the heat transfer rate of a horizontal circular tube.
Abstract: Passive heat transfer augmentation techniques, where inserts are employed in the flow passage to enhance the heat transfer rate, are advantageous as compared to active techniques because the insert manufacturing process is simple and these techniques can be easily used in an existing heat exchanger. An experimental investigation has been done by using louvered rectangular leaf type inserts by inserting it inside the horizontal circular tube. These louvered rectangular leaf type inserts were made up of aluminum material at different angles i.e. 30°, 45°, 60°, 90° respectively. Air was used as a working fluid which was passed through the circular pipe. Heat transfer rate was investigated using these louvered rectangular leaf type inserts into a plain tube. The results were further compared with those of plain tube to analyse the improvement of the heat transfer rate in presence of these inserts. Reynolds number considered for experimentation is in the range of 6000–11,000. After experimentation, it has been observed that the maximum experimental value of ‘h’ is 37.2859 W/m2K for 90° leaf angle. Also, the maximum experimental value of the Nusselt Number is 33.7478. For horizontal tube containing louvered rectangular leaf type inserts inclined at 90°, the heat transfer rate was increased by 3.9%, 16.19%, 85.28% and 70.81% for the velocity reading of 4.3 m/s, 5.6 m/s, 6.3 m/s and 7.3 m/s respectively as compared to that of plain tube.
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01 Nov 2004
TL;DR: In this paper, a review on progress with passive heat transfer augmentation is presented, where inserts are used in the flow passage to augment the heat transfer rate, where the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger.
Abstract: Heat transfer augmentation techniques (passive, active or a combination of passive and active methods) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air-conditioning equipment, refrigerators, radiators for space vehicles, automobiles, etc Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger In design of compact heat exchangers, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger working condition (both flow and heat transfer conditions) In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported The present paper is a review on progress with the passi
380 citations
TL;DR: In this paper, the effect of using louvered strip inserts placed in a circular double pipe heat exchanger on the thermal and flow fields utilizing various types of nanofluids is studied numerically.
166 citations
TL;DR: In this article, the authors investigated the effect of inserting a louvered strip into a concentric tube heat exchanger to generate turbulent flow which helped to increase the heat transfer rate of the tube.
134 citations
TL;DR: In this article, the effects of the conical ring turbulator inserts on the heat transfer rate and friction factor are experimentally investigated in a uniform heat flux tube by a passive method, several conical rings used as turbulators are mounted over the test tube.
126 citations
TL;DR: In this paper, the results obtained from experimental investigations of the augmentation of turbulent flow heat transfer in a horizontal tube by means of varying width twisted tape inserts with air as the working fluid are used.
Abstract: The present work shows the results obtained from experimental investigations of the augmentation of turbulent flow heat transfer in a horizontal tube by means of varying width twisted tape inserts with air as the working fluid. In order to reduce excessive pressure drops associated with full width twisted tape inserts, with less corresponding reduction in heat transfer coefficients, reduced width twisted tapes of widths ranging from 10 mm to 22 mm, which are lower than the tube inside diameter of 27.5 mm are used. Experiments were carried out for plain tube with/without twisted tape insert at constant wall heat flux and different mass flow rates. The twisted tapes are of three different twist ratios (3, 4 and 5) each with five different widths (26-full width, 22, 18, 14 and 10 mm) respectively. The Reynolds number varied from 6000 to 13500. Both heat transfer coefficient and pressure drop are calculated and the results are compared with those of plain tube. It was found that the enhancement of heat transfer with twisted tape inserts as compared to plain tube varied from 36 to 48% for full width (26mm) and 33 to 39% for reduced width (22 mm) inserts. Correlations are developed for friction factors and Nusselt numbers for a fully developed turbulent swirl flow, which are applicable to full width as well as reduced width twisted tapes, using a modified twist ratio as pitch to width ratio of the tape.
International Journal of Engineering, Science and Technology, Vol. 2, No. 6, 2010, pp. 107-118
114 citations