Heat Transfer Augmentation in a Round Tube with 60o Winglet Pair Inserts

2014 ◽  
Vol 931-932 ◽  
pp. 1188-1192 ◽  
Author(s):  
Suriya Chokphoemphun ◽  
Pattarapan Tongyote ◽  
Pongjet Promvonge ◽  
Withada Jedsadaratanachai ◽  
Teerapat Chompookham
Keyword(s):  
Heat Transfer ◽  
Operating Conditions ◽  
Transfer Enhancement ◽  
Airflow Velocity ◽  
Tubular Heat Exchanger ◽  
Transfer Rates ◽  
Heat Transfer Augmentation ◽  
Thermal Enhancement ◽  
Constant Wall Heat Flux ◽  
Thermal Enhancement Factor

The experimental study on heat transfer enhancement in a tubular heat exchanger fitted with 60o winglet pairs is carried out by varying airflow velocity in turbulent region in the test section having a constant wall heat-flux. Effects of three blockage ratios (BR=e/D= 0.1, 0.15 and 0.2) and three pitch ratios (PR=P/D= 1, 1.5 and 2) of the winglet pairs on heat transfer rates in the terms of Nusselt number (Nu) and pressure loss in the form of friction factor (f) are examined. The experimental results illustrated that the tube with winglet pair insert provides the heat transfer rate higher than the smooth tube around 1.7 to 2.6 times, depending upon operating conditions. The thermal enhancement factor for using the winglet-pair turbulator is in a range of 1.03 - 1.31.

scholarly journals Assessment of Thermal Performance of Non-Conventional Grooved Stepped Shoe Ribs by CFD Technique

2019 ◽  
Vol 9 (2) ◽  
pp. 75-82
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Transfer Enhancement ◽  
Heat Transfer Augmentation ◽  
Thermal Enhancement ◽  
Staggered Arrangement ◽  
Extended Surface ◽  
Computational Fluid Dynamics Cfd ◽  
Conventional Type ◽  
Thermal Enhancement Factor

In improvement of the thermal performance there is necessity of the heat transfer augmentation. Heat transfer enhancement can be achieved with enlarged or extended surface, impeded boundary level, augmentation in the turbulence etc. It is desired to keep the size of heat exchanger compact for better working conditions. In the proposed work, we made the Computational Fluid Dynamics (CFD) analysis of the non-conventional type of ribs. In this work the non-conventional Stepped grooved shoe shaped ribs were studied by changing its geometry parameters like rib height (15, 20,22mm), thickness of the rib (4, 5,10 mm), and the ratio between these entities. The numerical analysis was done to study change in rate of heat transfer and pressure drop. The effects of variation in staggered arrangements and truncation gap on thermal performance were also studied. It was observed that providing staggered arrangement with truncation gap of 20 mm gives the optimum value of thermal enhancement factor of 1.33.

scholarly journals Effect of Conical Strip Inserts and ZrO2/DI-Water Nanofluid on Heat Transfer Augmentation: An Experimental Study

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4554
Author(s):  
Mohamed Iqbal Shajahan ◽  
Jee Joe Michael ◽  
M. Arulprakasajothi ◽  
Sivan Suresh ◽  
Emad Abouel Nasr ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Test Section ◽  
Volume Concentration ◽  
Swirl Flow ◽  
Performance Ratio ◽  
Transfer Rates ◽  
Heat Transfer Augmentation ◽  
Twist Ratio ◽  
Constant Wall Heat Flux

There is a significant enhancement of the heat transfer rate with the usage of nanofluid. This article describes a study of the combination of using nanofluid with inserts, which has proved itself in attaining higher benefits in a heat exchanger, such as the radiator in automobiles, industries, etc. Nanofluids are emerging as alternative fluids for heat transfer applications due to enhanced thermal properties. In this paper, the thermal hydraulic performance of ZrO2, awater-based nanofluid with various volume concentrations of 0.1%, 0.25%, and 0.5%, and staggered conical strip inserts with three different twist ratios of 2.5, 3.5, and 4.5 in forward and backward flow patterns were experimentally tested under a fully developed laminar flow regime of 0–50 lphthrough a horizontal test pipe section with a length of 1 m with a constant wall heat flux of 280 W as the input boundary condition. The temperatures at equidistant position and across the test section were measured using K-type thermocouples. The pressure drop across the test section was measured using a U-tube manometer. The observed results showed that the use of staggered conical strip inserts improved the heat transfer rates up to that of 130.5%, 102.7%, and 64.52% in the forward arrangement, and similarly 145.03%, 116.57%, and 80.92% in the backward arrangement with the twist ratios of 2.5, 3.5, and 4.5 at the 0.5% volume concentration of ZrO2 nanofluid. It was also seen that the improvement in heat transfer was comparatively lower for the other two volume concentrations considered in this study. The twist ratio generates more swirl flow, disrupting the thermal hydraulic boundary layer. Nanofluids with a higher volume concentration lead to higher heat transfer due to higher effective thermal conductivity of the prepared nanofluid. The thermal performance factor (TPF) with conical strip inserts at all volume concentrations of nanofluids was perceived as greater than 1. A sizable thermal performance ratio of 1.62 was obtained for the backward-arranged conical strip insert with 2.5 as the twist ratio and a volume concentration of 0.5% ZrO2/deionized water nanofluid. Correlations were developed for the Nusselt number and friction factor based on the obtained experimental data with the help of regression analysis.

FORCED CONVECTION BASED HEAT TRANSFER ANALYSIS OF SPHERICAL DIMPLE AND PROTRUSION SURFACE IN TURBULENT FLOW

2017 ◽  
Vol 41 (5) ◽  
pp. 771-786 ◽  
Author(s):  
Ashif Perwez ◽  
Shreyak Shende ◽  
Rakesh Kumar
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Vortex Flow ◽  
Rectangular Channel ◽  
Heat Transfer Analysis ◽  
Flow Structures ◽  
Transfer Enhancement ◽  
Heat Transfer Augmentation ◽  
Thermal Boundary Conditions

An experimental and numerical investigation is performed to study the effect of dimple and protrusion geometry on the heat transfer enhancement and the friction factor of surfaces with dimples and protrusions subjected to turbulent flow. The parameters used to compare the spherical dimples and protrusions are Nusselt Number, friction factor, and flow pattern. These parameters are obtained for a Reynolds number of 10500-60900. The spherical dimple results showed the greater heat transfer, which is about 6.97% higher and pressure loss which is 5.07% lower than the spherical protrusion. The realistic heat transfer augmentation capabilities of channels with dimples and protrusions can be studied from the experimental results. The comparison is made with respect to the smooth rectangular channel under the same flow and thermal boundary conditions. The numerical analysis is performed which shows the different vortex flow structures of the spherical dimples and protrusions channel.

scholarly journals Heat transfer enhancement of car radiator using aqua based magnesium oxide nanofluids

2015 ◽  
Vol 19 (6) ◽  
pp. 2039-2048 ◽  
Author(s):  
Hafiz Ali ◽  
Muhammad Azhar ◽  
Musab Saleem ◽  
Qazi Saeed ◽  
Ahmed Saieed
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Management ◽  
Heat Transfer Performance ◽  
Inlet Temperature ◽  
Fluid Temperature ◽  
Transfer Enhancement ◽  
Volumetric Concentration ◽  
Flow Rates ◽  
Transfer Rates

The focus of this research paper is on the application of water based MgO nanofluids for thermal management of a car radiator. Nanofluids of different volumetric concentrations (i.e. 0.06%, 0.09% and 0.12%) were prepared and then experimentally tested for their heat transfer performance in a car radiator. All concentrations showed enhancement in heat transfer compared to the pure base fluid. A peak heat transfer enhancement of 31% was obtained at 0.12 % volumetric concentration of MgO in basefluid. The fluid flow rate was kept in a range of 8-16 liter per minute. Lower flow rates resulted in greater heat transfer rates as compared to heat transfer rates at higher flow rates for the same volumetric concentration. Heat transfer rates were found weakly dependent on the inlet fluid temperature. An increase of 8?C in inlet temperature showed only a 6% increase in heat transfer rate.

scholarly journals Thermal performance in a tubular heat exchanger with deltawinglets

2018 ◽  
Vol 192 ◽  
pp. 02062
Author(s):  
Pattarapan Tongyote ◽  
Pongjet Promvonge ◽  
Nattawoot Depaiwa ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Thermal Characteristics ◽  
Test Tube ◽  
Turbulent Regime ◽  
Airflow Rate ◽  
Tubular Heat Exchanger ◽  
Experimental Heat ◽  
Constant Wall Heat Flux

The paper presents an experimental heat transfer enhancement study in a tubular heat exchanger fitted with delta-winglets. The experimental work was conducted by varying the airflow rate in the test tube having a constant wall heat-flux for turbulent regime, Reynolds number (Re) from 5200 to 23,000. Effects of three pitch ratios (PR=P/D=1.5, 2.0 and 3.0) and two attack angles, α = 45° and 60°, of the winglets at a single blockage ratio (BR=b/D = 0.15) on thermal characteristics are examined. The experimental results show that the winglet-inserted tube yields, respectively, the heat transfer, friction factor and thermal performance in the form of TEF around 1.99–4.08, 4.9–14.3 times higher than the plain tube and 0.85–1.85, depending on the operating condition.

Heat Transfer Enhancement in Annular Shear-Thinning Flows Over a Sudden Pipe Expansion

2017 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Power Law ◽  
Shear Thinning ◽  
Diameter Ratio ◽  
Transfer Enhancement ◽  
Heat Transfer Augmentation ◽  
Prandtl Numbers ◽  
Power Law Index ◽  
The Impact

Heat transfer enhancement in suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid is studied within the steady laminar flow regime. Conservation of mass, momentum, and energy equations, along with the power-law constitutive model are numerically solved. The impact of inflow inertia, annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers, is reported for: Re = {50, 100}, k = {0, 0.5, 0.7}; n = {1, 0.8, 0.6}; and Pr = {1, 10, 100}. Heat transfer enhancement downstream of the expansion plane, i.e., Nusselt numbers, Nu, higher than the fully developed value, in the downstream pipe, is observed only for Pr = 10 and 100. Higher Prandtl numbers, power-law index values, and annular diameter ratios, in general, reflect a more dramatic heat transfer augmentation downstream of the expansion plane. Heat transfer augmentation for Pr = 10 and 100, is more dramatic for suddenly expanding annular flows, in comparison with suddenly expanding pipe flow. For a given annular diameter ratio and Reynolds numbers, increasing the Prandtl number from Pr = 10 to Pr = 100, always results in higher peak Nu values, for both Newtonian and shear-thinning non-Newtonian flows.

Heat Transfer Enhancement Using Shaped Polymer Tubes: Fin Analysis

2004 ◽  
Vol 126 (2) ◽  
pp. 211-218 ◽  
Author(s):  
Zhihua Li ◽  
Jane H. Davidson ◽  
Susan C. Mantell
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Transfer Rate ◽  
Polymeric Materials ◽  
Transfer Enhancement ◽  
Transfer Rates ◽  
Shaped Tube ◽  
Polymer Tubes

The use of polymer tubes for heat exchanger tube bundles is of interest in many applications where corrosion, mineral build-up and/or weight are important. The challenge of overcoming the low thermal conductivity of polymers may be met by using many small-diameter, thin-walled polymer tubes and this route is being pursued by industry. We propose the use of unique shaped tubes that are easily extruded using polymeric materials. The shaped tubes are streamlined to reduce form drag yet the inside flow passage is kept circular to maintain the pressure capability of the tube. Special treatment is required to predict convective heat transfer rates because the temperature distribution along the outer surface of the shaped tubes is nonuniform. The average forced convection Nusselt number correlations developed for these noncircular tubes can not be used directly to determine heat transfer rate. In this paper, heat transfer rates of shaped tubes are characterized by treating the tubes as a base circular tube to which longitudinal fin(s) are added. Numerical solution of an energy balance on the fin provides the surface temperature distribution and a shaped tube efficiency, which can be used in the same manner as a fin efficiency to determine the outside convective resistance. The approach is illustrated for three streamlined shapes with fins of lenticular and oval profile. The presentation highlights the effects of the geometry and the Biot number on the tube efficiency and heat transfer enhancement. Convective heat transfer is enhanced for the oval shaped tube for 2000⩽Re⩽20,000 when Bi<0.3. For polymeric materials, the Biot number in most applications will be greater than 0.3, and adding material to the base tube reduces the heat transfer rate. The potential benefit of reduced form drag remains.

Heat Transfer in Annular Shear-Thinning Non-Newtonian Flows Over a Sudden Pipe Expansion

2016 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Power Law ◽  
Shear Thinning ◽  
Wall Heat Transfer ◽  
Transfer Enhancement ◽  
Transfer Rates ◽  
Newtonian Flows ◽  
Prandtl Numbers ◽  
Annular Pipe

Non-isothermal suddenly expanding annular pipe flows of a shear-thinning non-Newtonian fluid are numerically studied within the steady laminar flow regime. The power-law constitutive equation is used to model the shear-thinning rheology of interest. A parametric study is performed to reveal the influence of annular-nozzle-diameter-ratio, k, power-law index, n, and Prandtl numbers over the following range of parameters: k = {0, 0.5}; n = {1, 0.6}; and Pr = {1, 10, 100}. Heat transfer enhancement, i.e., wall heat transfer rates higher than the fully developed ones downstream of the expansion plane, is observed only for Pr = 10 and 100. In the case of Pr = 1, wall heat transfer rates monotonically increase to the fully developed value. Higher Pr, k, and n values, in general, result in more significant heat transfer enhancement downstream of the expansion plane. Further, shear-thinning non-Newtonian flows display two local peak wall heat transfer rates, in comparison with only one peak value in the case of Newtonian flows.

Visualization of the Heat Transfer Enhancement During Condensation in a Microfin Tube

2006 ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Luca Doretti ◽  
Simone Mancin ◽  
Luisa Rossetto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Saturation Temperature ◽  
Flow Patterns ◽  
Operating Conditions ◽  
Vapor Quality ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Plain Tube ◽  
The Heat Transfer Coefficient

Microfins tubes are largely used in refrigeration industry for in-tube refrigerant condensation, because of the heat transfer enhancement when compared to equivalent smooth tubes under the same operating conditions. But not much evidence about the effect of microfins on the condensation flow patterns is available in the open literature. There is agreement in the open literature that the mechanisms of heat transfer are intimately linked with the prevailing two-phase flow regime. The present authors have recently measured the heat transfer coefficient during condensation of R410A in a microfin tube. The heat transfer enhancement in this tube can be experimentally evaluated by comparing those coefficients to the ones measured by Cavallini et al. (2001) in a plain tube, at the same operating conditions. The same operative conditions (saturation temperature, vapor quality and mass flux), occurring during the heat transfer measurements, were reproduced in a different section for visualization of flow patterns during condensation of R410A. The flow visualization has been carried out both in the plain tube and in the microfin tube. The objective of the present paper is to present the heat transfer enhancement during condensation of R410A and to show the flow visualized at the same operating condition for both the smooth and the microfin tube, aiming to link the heat transfer enhancement to the flow pattern variation.

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