Numerical Investigation of Heat Transfer Performance of Various Coiled Square Tubes for Heat Exchanger Application (original) (raw)
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International Journal of Heat and Mass Transfer
The present article reports on experimental investigation of heat transfer and pressure drop characteristics of multi tubes in tube helically coiled heat exchanger. The study aims to investigate the effects of heat exchanger geometric parameters and fluid flow parameters; namely, number of inner tubes, annulus hydraulic diameter, Reynolds numbers and input heat flux, on performance of the heat exchanger. Different coils with different numbers of inner tubes, namely, 1, 3, 4 and 5 tubes, were tested. Results showed that: (a) coil with three inner tubes has bitter heat transfer characteristics as compared with other coils, (b) coils with 3 and 4 inner tubes, respectively, have higher values of h A h (the parameter used to measure performance and compactness of compact heat exchanger) as compared to other coils, (c) for all coils and at the tested ranges of Reynolds number and heat flux, input heat flux has no effect on heat transfer coefficients, and (d) pressure drop increases with increasing
Heat transfer performance of non-circular coiled tubes - Research summary, challenges and directions
INTERNATIONAL JOURNAL OF AUTOMOTIVE AND MECHANICAL ENGINEERING
Coiled tubes have been widely used in major industries due to their high heat transfer, ease of manufacturing and compactness. Numerous studies have been conducted experimentally and numerically to evaluate the heat transfer performance of coiled tubes. A majority of these studies were focused on circular tubes, while only limited studies were concerned on non-circular tubes. Recently, a series of computational studies have been conducted in our research group to investigate the flow characteristic and heat transfer performance of non-circular coiled tubes. Several key parameters affecting flow behavior and heat transfer performance have been evaluated and examined. The heat transfer performance is numerically evaluated and compared by utilizing the concept of Figure of Merit (FoM). The paper is intended to provide an essential summary of these numerical studies with the aim of providing a general overview of the advantage and drawbacks of non-circular coiled tubes in thermal engineering applications. Challenges and directions of the research will also be discussed. In general, it is revealed that heat transfer improvement in the coiled tube is followed by increasing pumping power. Moreover, with a more complex coiled geometry proposed, the processes of manufacturing the tube and creating the computational domain will become major issues in non-circular coiled tube studies. In addition, more studies on the application of coiled tubes used for heat exchanger and chemical reactor are expected to increase in the future, especially in the micro or nanoscale.
International Journal of Advance Research and Innovative Ideas in Education, 2021
The Heat exchanger is a device which used to transfer heat from one fluid to another through a solid medium or interface. There is various type of heat exchanger available. In this research shell and helical coil tube type heat exchanger is selected. Our objective was to change the mass flow rate to enhance the efficiency of the heat exchanger. An Interstitial Oscillating Flow in tubes is selected for the investigation. Design of new shell and tube heat exchanger is done using standard designing procedure and 3D modeling is done in ANSYS. Finite Element Analysis software ANSYS Workbench 18.0 is used to perform CFD analysis under a standard working condition to find performance parameter. We found that the Interstitial Oscillating Flow provides more effective heat exchange due to increase in the convective surface. The computational fluid dynamics (CFD) model equations are solved to predict the hydrodynamic and thermal behaviour of the exchanger. The geometry of the problem and meshing of it have been made in and the models have been solved by ANSYS Workbench. CFD models or packages provides the contours and data which predict the performance of the heat exchanger design and are effectively used because it has ability to obtain optimal solutions and has work in difficult and hazardous conditions.
International Communications in Heat and Mass Transfer, 2002
The purpose of thii study was to determine the relative advantage of using a helically coiled heat exchsnger versus a stmiglt tube heat exchanger for heating liquids. The pktic~lar diieratce in this study compared to other similar studies was the boundary conditions fbr the helical coil. Most studies focus on constsnt wall tempera&e or constant heat flux, whereas in this study it wrs a fluid-to-fluid heat exchanger. Results showed that the heat transfer coeflicient was eftbcted by the geometry of the heat exchmger and the teqwature of the water bath surrounding the heat exchanger. Ah tests were petfamed in the transitional and ttnbulert regimes. 0 2002
2015
Despite numerous studies of shell and helically coiled tube heat exchangers, a few investigations on the heat transfer and flow characteristic consider the geometrical effects like coil pitch. Moreover, this scarcity is highlighted for the shell side of this type of heat exchangers. This study reports experimental and Computational Fluid Dynamics (CFD) investigations on heat transfer and flow characteristics of a shell and helically coiled tube heat exchanger. The experiments were carried out using a helically coiled tube, which was placed in a cylindrical shell. Hot and cold water were used as the process fluids on the tube and shell side, respectively. The CFD modeling technique was employed to describe the experimental results, fluid flow pattern, and temperature profiles as well as dead zones in the heat exchanger. Quantitative predicted results of CFD modeling show a good agreement with the experimental data for temperature. The effect of the coil pitch on heat transfer rate wa...
Numerical Investigation of Thermal-Flow Characteristics in Heat Exchanger with Various Tube Shapes
Applied Sciences, 2021
In this study, eight configurations of oval and flat tubes in annular finned-tube thermal devices are examined and compared with the conventional circular tube. The objective is to assess the effect of tube flatness and axis ratio of the oval tube on thermal-flow characteristics of a three-row staggered bank for Re (2600 ≤ Re ≤ 10,200). It has been observed that the thermal exchange rate and Colburn factor increase according to the axis ratio and the flatness, where O1 and F1 provide the highest values. O1 produces the lowest friction factor values of all the oval tubes at all Re, and F4 gives 13.2–18.5% less friction than the other tube forms. In terms of performance evaluation criterion, all of the tested tubes outperformed the conventional circular tube (O5), with O1 and F1 obtaining the highest values. The global performance criterion of O1 has been found to be 9.6–45.9% higher as compared to the other oval tube geometries at lower values of Re, and the global performance criter...
JSME International Journal Series B, 2005
In the present study, new experimental data on the heat transfer characteristics and the performance of a spirally coiled heat exchanger under sensible cooling conditions is presented. The spiral-coil heat exchanger consists of a steel shell and a spirally coiled tube unit. The spiral-coil unit consists of six layers of concentric spirally coiled tubes. Each tube is fabricated by bending a 9.27 mm diameter straight copper tube into a spiral-coil of five turns. The innermost and outermost diameters of each spiral-coil are 67.7 and 227.6 mm, respectively. Air and water are used as working fluids in shell side and tube side, respectively. A mathematical model based on the conservation of energy is developed to determine the heat transfer characteristics. There is a reasonable agreement between the results obtained from the experiment and those obtained from the model and a good agreement for the high air mass flow rate region. The results obtained from the parametric study are also discussed.
— In heat exchangers various active and passive techniques have been used over plain tubes to enhance heat transfer. Twisted tube is a passive technique. Presently twisted tubes are limited to shell and tube type long and straight passage applications. The main aim of this study is to determine its feasibility for use in applications like automobile radiators, air conditioners or similar type of multi pass applications. In present study, twisted tube is compared with plain tube in multiple tube pass (4 passes) of 0.3 m length each pass for four flow rates of 1.5 lpm, 1.37 lpm, 0.5 lpm and 0.24 lpm resulting in Reynolds number of Re 625 to 7000 covering turbulent and laminar range. The comparison is done analytically, experimentally and numerically. The results showed that for the given mass flow rates and inlet temperature, the performance of plain tube is better than twisted tube in low flow rates.For high Reynolds number range the performance of twisted tube is better, the reason is attached flow through tubes. Thus this study concludes that for multi pass configuration one should always select twisted tubes according to the required flow rate. Index Terms— heat transfer coefficient, multipass heat exchanger, plain tube, Reynolds Number, synergy angle, Twisted tube heat exchanger, temperature difference. —————————— ——————————