A Numerical Analysis of Heat Transfer Enhancement by Turbulence Generated From Swirl Flow by Twisted Tape

2018 ◽  
Author(s):  
Muhammad Azmain Abdullah ◽  
M. Ruhul Amin ◽  
Mohammad Ali
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
External Surface ◽  
Swirl Flow ◽  
Surface Heat ◽  
Inlet Pressure ◽  
Twisted Tape ◽  
Twist Ratio

Heat exchangers are widely used in heating and cooling devices. The primary challenge is to improve the efficiency of the heat transfer equipment. Researchers have utilized various techniques to achieve this goal. Using twisted tapes could significantly increase the heat transfer rate from a circular surface due to turbulence generated from swirl flow. To enhance the heat transfer rate by twisted tape, two types of arrangements namely: (i) plain twisted tape and (ii) altered twisted tape geometries are used. These arrangements result in swirl flows. For improving heat transfer through swirl flow, some important parameters such as Reynolds number, external surface temperature, friction factor, inlet pressure, and surface heat flux are also considered. To identify the aftereffect of the velocity of inlet water, several parameters namely: (i) external surface temperature, (ii) inlet pressure, (iii) external surface heat flux and (iv) twist ratio are varied. A numerical modelling using k-ε method is performed to evaluate the effects of turbulence from the twisted tape on the heat transfer rate. The objective is to analyze the improvement of heat transfer effectiveness due to the swirl flow. The change in the values of the resulting Reynolds number by changing the inlet fluid velocity from 0.1 ms−1 to 0.7 ms−1 and rotational speed from 200 rpm to 600 rpm is studied. It is observed that for such changes heat transfer increases by 17 percent. It is also observed that heat transfer is directly proportional to inlet pressure and inversely proportional to the increment of twist ratio. The rate of heat transfer increased from 17 percent to 19 percent when the angular velocity of the twisted tape is changed from the 0 rpm to 600 rpm while the velocity of the water inside the pipe is held constant at 0.7 ms−1. Higher heat transfer rate is observed with high inlet pressure. Likewise, higher value of the Nusselt number is observed with higher rotational speed of the twisted tape and higher velocity at the pipe inlet. In addition, it is also observed that when the twist ratio is changed from 4 to 6, the rate of heat transfer is diminished by 6 percent.

Instantaneous Local Heat Flux Measurements in a Small Utility Engine

2009 ◽  
Author(s):  
Terry Hendricks ◽  
Jaal Ghandhi ◽  
John Brossman
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Surface Temperature ◽  
Heat Transfer Rate ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
Surface Heat ◽  
High Load ◽  
Flux Measurements

Heat flux measurements were performed in an air-cooled utility engine using a fast-response coaxial-type surface thermocouple. The surface heat flux was calculated using both analytical and numerical models. The heat flux was found to be a strong function of engine load. The peak heat flux and initial heat flux rise rate increase with engine load. The measured heat flux data were used to estimate a global heat transfer rate, and this was compared with the heat transfer rate calculated by a single-zone heat release analysis. The measured values of heat transfer were higher than the calculated values largely because of the lack of spatial averaging. The high load data showed an unexplainable negative heat flux during the expansion stroke while the gas temperature was still high. A 1D and 2D finite difference numerical model utilizing an adaptive timestep Crank-Nicholson (CN) integration routine was developed to investigate the surface temperature measurement. Applying the measured surface temperature profile to the 1D model, the resultant surface heat flux showed excellent agreement with the analytical inversion solution and captured the reversal of the energy flow back into the cylinder during the expansion stroke. The 2D numerical model was developed to observe transient lateral conduction effects within the probe and incorporated the various materials used in the construction and assembly of the heat flux sensor. The resulting average heat flux profile for the test case is shown to be slightly higher in peak and longer in duration when compared with the results from the 1D analytical inversion, and this is attributed to contributions from the high thermal diffusivity constituents in the sensor. Furthermore, the negative heat flux at high load was not eliminated suggesting that factors other than lateral conduction may be affecting the measurement accuracy.

scholarly journals Numerical Investigation of Heat Transfer and Friction Factor Characteristics in a Circular Tube Fitted with V-Cut Twisted Tape Inserts

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sami D. Salman ◽  
Abdul Amir H. Kadhum ◽  
Mohd S. Takriff ◽  
Abu Bakar Mohamad
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Investigation ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Twisted Tape ◽  
Maximum Heat ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Twist Ratio

Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y=2.93) and different cut depths (w=0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y=2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratioy=2.93and cut depthw=0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.

Procedures for Determining Surface Heat Flux Using Thin Film Gages on a Coated Metal Model in a Transient Test Facility

1988 ◽  
Vol 110 (2) ◽  
pp. 242-250 ◽  
Author(s):  
J. E. Doorly
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Rate ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
Turbine Blades ◽  
Surface Heat ◽  
Test Facility ◽  
Coated Metal

The paper describes how thin film surface heat flux gages may be used to measure surface heat transfer rate to enamel-coated metal turbine blades. Flexible methods, which are also computationally efficient, for obtaining the heat transfer rate are described. Experimental results, using the new coated metal turbine blades and processing techniques, in a stationary transient cascade facility are given, and are shown to agree well with results using the existing method for gages on single-layer substrate blades. The application of the gages for measuring highly unsteady heat transfer is also discussed.

scholarly journals Augmentation of Heat Transfer in a Duct with Rotating Turbulator using Al2o3 Nanofluid

2019 ◽  
Vol 8 (3) ◽  
pp. 3059-3062
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Twist Ratio ◽  
Al2o3 Nanofluid

The heat transfer enhancement is one of the essential factors to be considered in the design of heat exchangers. The rate of heat transfer can be enhanced by inserting and modifying the geometric configuration of the turbulators in the tube of heat exchangers. In our present work we conducted the experiment to investigate the rate of heat transfer enhancement in a tubular in a heat exchanger by using rotating twisted tape turbulator of twist ratio 3.27 using water and Al2O3 nanofluid as a testing fluid at the flow rate of 1, 2, and 3 LPM. The range of Reynolds number used is 2000<Re<10000, the heat transfer rate calculated for each case of rotating TTT with the speed of 0 to 300 RPM with the step of 100 RPM. The obtained results are compared between water and Al2O3 nanofluid, with and without rotating TTT. From the comparisons, it was found that the TTT with U-cut and the use of Al2O3 nanofluid gives the better rise in the heat transfer rate of about 39.63%. The augmented rate of heat transfer is due to the more turbulence when the rotating TTT is used and replacing the water with nanofluid as the testing fluid which of high thermal properties.

Experimental Investigation of Effect of Different Types of Surfactants and Jet Height on Cooling of a Hot Steel Plate

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Satya V. Ravikumar ◽  
Jay M. Jha ◽  
Soumya S. Mohapatra ◽  
Surjya K. Pal ◽  
Sudipto Chakraborty
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nonionic Surfactant ◽  
Heat Transfer Rate ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
Steel Plate ◽  
Surface Heat ◽  
Initial Surface ◽  
Different Types

Heat transfer studies of a hot AISI 304 stainless steel plate by water jet impingement with different concentrations of three different types of surfactants have been investigated. The study involves a square plate of 100 mm × 100 mm surface area and 6 mm thickness with three subsurface thermocouples positioned at various locations inside the plate. The influence of jet height has been studied by varying the distance between the nozzle and plate from 200 mm to 600 mm. The results show that the heat transfer rate is found to increase with the jet height up to 400 mm and thereafter decreases due to capillary instability of liquid jet. Based on the maximum surface heat flux obtained for a particular nozzle height of 400 mm and an initial surface temperature of 900 °C, further experiments have been carried out with different types of surfactants. The types of surfactants used in the experimental study are anionic surfactant (sodium dodecyl sulphate, SDS), cationic surfactant (cetyltrimethylammonium bromide, CTAB) and nonionic surfactant (Polyoxyethylene 20 sorbitan monolaurate, Tween 20). During cooling, the transient temperature data measured by thermocouples have been analyzed by inverse heat conduction procedure to calculate surface heat flux and surface temperatures. The increase in surface heat flux has been observed with increasing concentration of surfactants and it has been found to be limited to a particular concentration of surfactant after which further increase in concentration leads to decrease in heat flux. Use of surfactant added water minimizes the surface tension and promotes better spreadability of coolant on the test specimen by reducing the solid–liquid contact angle. The maximum heat transfer rate has been found by using nonionic surfactant additive which can primarily be attributed to its lesser foam formability nature.

scholarly journals Nanofluid Flow on a Shrinking Cylinder with Al2O3 Nanoparticles

Mathematics ◽  
2021 ◽  
Vol 9 (14) ◽  
pp. 1612
Author(s):  
Iskandar Waini ◽  
Anuar Ishak ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Friction Factor ◽  
Surface Heat Flux ◽  
Transfer Rate ◽  
Surface Heat ◽  
Al2o3 Nanoparticles ◽  
Nanofluid Flow ◽  
Curvature Parameter ◽  
Over Time

This study investigates the nanofluid flow towards a shrinking cylinder consisting of Al2O3 nanoparticles. Here, the flow is subjected to prescribed surface heat flux. The similarity variables are employed to gain the similarity equations. These equations are solved via the bvp4c solver. From the findings, a unique solution is found for the shrinking strength λ≥−1. Meanwhile, the dual solutions are observed when λc<λ<−1. Furthermore, the friction factor Rex1/2Cf and the heat transfer rate Rex−1/2Nux increase with the rise of Al2O3 nanoparticles φ and the curvature parameter γ. Quantitatively, the rates of heat transfer Rex−1/2Nux increase up to 3.87% when φ increases from 0 to 0.04, and 6.69% when γ increases from 0.05 to 0.2. Besides, the profiles of the temperature θ(η) and the velocity f’(η) on the first solution incline for larger γ, but their second solutions decline. Moreover, it is noticed that the streamlines are separated into two regions. Finally, it is found that the first solution is stable over time.

High Temperature Endurance of FRP Composites With Polymeric Thermal Barrier Coatings

2010 ◽  
Author(s):  
Edwin Igiede ◽  
Patrick F. Mensah ◽  
Stephen Akwaboa
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Temperature ◽  
Internal Energy ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Surface Heat ◽  
External Boundary ◽  
Temperature Dependent ◽  
Composite Pipe

High Temperature exposure and the corresponding thermo-mechanical behavior of cylindrical polymer composite pipe using CFD simulation has been investigated in this study. The software FLUENT was employed for the analysis of heat transfer, by coupling equations of energy and motion. Analysis was done based on applied external boundary temperature profile, change in internal energy, the total surface heat flux and surface heat transfer rate in order to evaluate the extent of thermal damage. FLUENT compatible program written in C++ language in the form of user define functions (UDF) has been developed and used to specify the time dependent heat flux generated temperature as well as temperature dependent thermal properties of density, thermal conductivity and specific heat. Available furnace test experimental data from (ASTM 1173-95) database were used as outer surface boundary condition in the model setup by developing it into UDF correlation equations. The outputs of the FLUENT simulations are predictions of transient temperature distribution through the thickness of the pipe wall that were then used in evaluating the thermal stresses of the composite pipe. Validation of the simulation results is done with existing data available in the literature. Using the wall generated temperatures, internal energy, the rate of change of the temperature dependent properties and the heat transfer rate, the thermal endurance of each of the coatings materials has been predicted in this work. At the same time knowledge of the thermal performance of these materials is essential for the optimum design of protection based on the composite application.

Enhancement and Prediction of Heat Transfer Rate in Turbulent Flow Through Tube With Perforated Twisted Tape Inserts: A New Correlation

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
J. U. Ahamed ◽  
M. A. Wazed ◽  
S. Ahmed ◽  
Y. Nukman ◽  
T. M. Y. S. Tuan Ya ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Circular Tube ◽  
Twisted Tape ◽  
Pumping Power ◽  
Plain Tube ◽  
Flow Through

An experimental investigation has been carried out for turbulent flow in a tube with perforated twisted tape inserts. The mild steel twisted tape inserts with circular holes of different diameters (i.e., perforation) are used in the flow field. An intensive laboratory study is conducted for heat transfer and pressure drop characteristics in the tubes for turbulent flow with various airflow rates. Heat transfer and pressure drop data are engendered for a wide range Reynolds number (1.3×104–5.2×104). Tube wall temperature, pressure drop, air velocity, and its temperature are measured both for plain tube and for tube with perforated twisted tape inserts. Heat transfer coefficients, Nusselt number, pumping power, and heat transfer effectiveness are calculated for both cases. Experimental results showed that perforated twisted inserts of different geometry in a circular tube enhanced the heat transfer rate with an increase in friction factor and pumping power for turbulent flow. The pumping power, heat transfer coefficient, and effectiveness in the tube with the twisted tape inserts are found to increase up to 1.8, 5.5, and 4.0 times of those for the plain tube for same Reynolds number, respectively. Finally, a correlation is developed for prediction of the heat transfer rate for turbulent flow through a circular tube with perforated twisted tape inserts.

Heat Transfer Enhancement in a Tube Fitted With Twisted Tape Swirl Generator

2010 ◽  
Author(s):  
Smith Eiamsa-ard ◽  
Panida Seemawute ◽  
Khwanchit Wongcharee
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Working Fluid ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Flow Friction ◽  
Friction Heat ◽  
Swirl Generator ◽  
Twist Ratio ◽  
Plain Tube

Flow friction, heat transfer and thermal performance characteristics in a tube fitted with peripherally-cut twisted tape (PT) have been experimentally investigated. The twist ratio (y/W) of twisted tape was varied from 3 to 5 while the depth of peripheral cut ratio (d/W) and the width of peripheral cut ratio (w/W) were both kept constant at 0.22. The experiments were conducted for the Reynolds number ranging from 5100 to 19,700, using water as a working fluid. The plain tube and the tube equipped with the typical twisted tape (TT) with three different twist ratios (y/W = 3, 4 and 5) were also tested for comparison. The obtained results reveal that the use of PT enhances Nusselt number up to 211% and 138% compared to those of the plain tube and the tube with TT, respectively. It is also found that heat transfer rate increases with decreasing twist ratio. Additionally, the performance evaluation to assess the real benefits in using the PT as heat transfer enhancer has also been determined.

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