Conical Inserts Research Articles

Experimental Investigation of Conical Spring Inserts on In-Tube Heat Transfer and Pressure Drop

Experimental Investigation of Conical Spring Inserts on In-Tube Heat Transfer and Pressure Drop

Precise control of discharge of spherical particles by cone valve configuration: Insert – Converging orifice

The effect of the size and shape of the insert (inverted cone, sphere) when placed axially above an orifice on the mass discharge rate (MDR) of monodisperse spherical particles from a cylindrical silo has been investigated through experiments and DEM simulations. MDR characteristics have been measured for various distances between the insert and the orifice.An important practical finding is that, within a specific range of placement distances, the MDR increases by approximately 10% when a conical insert is used, whereas no such effect was observed when a spherical insert was employed.It was observed that, in some cases, a slight increase in friction coefficient leads to an increase in MDR as result of alterations in the initial grain structure, facilitating faster discharge.In a quasi-2D configuration, significant changes in flow rate occur when the thickness exceeds the natural multiple of dp, allowing the next layer of particles to flow.

Effect of triangular perforated flat cone-shaped inserts on performance of double-tube heat exchanger

This study investigated the effect of triangular perforations with flat conical inserts in a double-tube heat exchanger. Triangular perforations with flat cone-shaped inserts were placed inside the inner tube to enhance the heat transfer coefficient. The experiments were conducted for a number of flat conical strips (m) and pitch ratios (P = p/di) for flows varying from Re = 3000 to 9000 at a constant attack angle (α = 20°). The results showed that a triangular perforation with flat cone-shaped inserts remarkably increases the heat transfer factor, in contrast to flat conical inserts. The rise in the coefficient of heat was attributed to the creation of turbulence and disturbance of the boundary layer caused by perforated inserts. Furthermore, it was observed that the heat transfer coefficient increased with the Reynolds number, indicating that the effect of the inserts was more significant at higher fluid velocities. Correlations were developed to compare and analyze the results of the Nusselt number and friction factor. The developed correlation results are in good agreement with the experimental results. The findings obtained from this study can be implemented to enhance the performance and optimize the design parameters of industrial heat exchangers.

Performance of TiO2 nanofluids on the efficiency of a parabolic trough collector using a corrugated tube absorber with conical strip inserts

The paper discusses how to improve the performance of a parabolic trough collector with a corrugated tube absorber and conical strip inserts by using (Titanium Oxide) TiO2/DI water nanofluids. To evaluate the performance of the proposed system, three different concentrations (0.1%, 0.2%, and 0.3%) of TiO2 nanofluid were used on a volume basis, and experiments were conducted using different mass flow rates (0.011, 0.012, 0.013, 0.014, and 0.015 kg/s) of the working medium. Using a 0.3% volume concentration of TiO2 nanofluid with the combination of a corrugated tube (pc = 8 mm and hc = 2 mm) and the conical strip insert (pi = 20 mm), the maximum collector efficiency of 61% was observed. Compared to the corrugated tube, the improved collector efficiency of the conical strip inserts of 20, 30, and 50 mm pitches were 10.9%, 7.8%, and 4.3% higher, respectively.

Granular stresses in granular flows subjected to different obstacles

Although the application and development of continuum approaches demonstrate immense promise to model granular flows, the assumption of isotropic stress state in a constitutive law needs to be carefully examined, especially for accurately modeling the kinematics and kinetics of obstructed granular flows. This paper investigates the effect of obstacles on granular stresses and stress ratios in 3D granular silo flows by using discrete element method (DEM). The adopted obstacles include a conical insert, disk insert, BINSERT, hollow cylinder insert and hollow silo insert, as well as the absence of any insert for comparison. A novel (simple but robust) method with ring measurement cells was proposed to determine average stress tensors for granular flows. An innovative slice method with null friction boundaries was also proposed to significantly reduce DEM computational time. The validity of the proposed DEM model was justified by a repose angle experiment and two numerical verification examples. Results reveal that the blocking effect from the obstacles and the hopper wall of the silos led to a significant increase in normal and shear stresses. The normal stresses exhibited slight anisotropy in steady and uniform granular flows, and resulted in a stress ratio of approximately 1.0, indicating an approximately isotropic stress state. Unlike the normal stresses, the shear stresses however showed strong anisotropy even in the steady and uniform regime. The obstructed granular silo flows exhibited strong anisotropy not only in normal stresses, but also in shear stresses. The stress ratio in the obstructed granular flows can appreciably deviate from unity, varying between 0.27 and 2.24. Moreover, the vertical stresses dominated the contact force transmission in the granular silo flows, and showed the formation of dynamic granular arching.

Experimental study of fluid flow properties in spiral tube heat exchanger with varying insert shape over spiral tube profile

Experimental and computational analysis is carried out for analyzing the effect of different shapes of inserts. The inserts used are conical inserts, hemispherical shape insert, helical insert and these are mounted over cascaded spiral copper tube heat exchanger. The performance characteristics and fluid flow characteristics are studied for turbulent-counter flow and the fluid is water. Experimentation carried out for cold water at 304 K and hot water at 333 K and the rate of fluid flow for cold water inside spiral tube is 0.725 to 2.955 L/min. The hot water flows at 333 K with fluid rate of flow 4.025 L/min horizontally across outer shell. The comparative study of different shapes of insert with rate of fluid flow and Reynolds number is considered ranging from 4236 to18545. The study stated that the helical type insert gives promising and significant improvement by 18.5 % more than spiral tube without insert, 15.5 % more than conical insert and 11.5 % more than hemispherical shape insert for thermal performance under turbulent-counter flow. The minimum and maximum values obtained from the study for h htr , Nu, f, effectiveness N.T.U and ɳ tp varies from 1298.5 to 3541.6, 88.28–160, 0.0438–0.0306, 0.89–0.59, 2.51–1.24 and 2.41–1.31 respectively. The maximum optimum value is obtained for performance factor (ɳ tp ) is 1.51 for Reynolds number ranging 13,322 for helical insert of 2 mm diameter and 10 mm pitch distance.

NUMERICAL STUDY OF THERMOHYDRAULIC PERFORMANCE IN HEAT EXCHANGER WITH CONICAL TUBES INSERTS AND CU-WATER NANOFLUID

This study aims to improve the heat transfer performance of heat exchangers significantly by increasing the turbulence zone and the flow vortices via in-pipe equipment. The Transition k-kl-omega model was selected as the turbulence model to simulate the thermohydraulic performance of incomplete conical equipment when Re is set between 5000 and 15000. Cu-Water is considered to be the base fluid. The accuracy of the simulation results has been demonstrated by comparing them with experimental formulas and existing experimental results. In this study, a numerical simulation was used to examine the effect of geometric factors of the in-pipe equipment and the volume fraction of nanoparticles on its thermal-hydraulic performance. It was demonstrated that heat transfer capacity in pipes with new inlet pipes is increased more than in conventional circular pipes. In the absence of nanoparticles, the optimal conditions were found for Re = 15000, S = 1, n = 0, in which case the Nusselt number was 314.04, and the coefficient of friction was 6.56. Accordingly, the new tube has a significant performance potential, increasing the Nusselt number by about three times that of the smooth tube.

Heat Transfer Studies on Solar Parabolic trough Collector Using Corrugated Tube Receiver with Conical Strip Inserts

The heat transfer characteristics of the working fluid passing through the absorber of a solar parabolic trough collector (SPTC) can be enhanced by the creation of a turbulence effect. Therefore, a novel idea was implemented by introducing a corrugated tube (CT) absorber instead of a plain tube absorber in a solar parabolic trough collector. The heat transfer enhancement was improved further through the use of conical strip inserts inside the corrugated tube absorber of the SPTC. A corrugated tube (CT) receiver with a pitch of 8 mm and corrugation height of 2 mm was used with three different pitches of conical strip inserts (pitch pi = 20 mm, 30 mm and 50 mm) for the analysis of the thermal performance of the SPTC. Initially, experiments were conducted in a plain tube and corrugated tube receiver at different mass flow rates. The convective heat transfer rate was increased for all the configurations of the conical strip inserts. The SPTC performance was good for the combination of the corrugated tube (pc = 8 mm and hc = 2 mm) and the conical strip insert I3 (pi= 20 mm). The experimental results showed that the maximum achieved Nu value, friction factor, instantaneous efficiency and thermal efficiency of the CT-I3 were 177%, 38%, 26.92% and 9% compared to the plain tube under the same working conditions.

Influence of Radial Flows on Power Density and Gas Stream Pressure Drop of Tubular Solid Oxide Fuel Cells

The development of solid oxide fuel cells (SOFCs) for powering vehicles requires high power densities. The radial flows generated by the insert structures in SOFC fuel channels could improve the power density by facilitating the fuel to enter the porous anode for electrochemical reactions. In this paper, we developed a 2D axisymmetric numerical model to examine the influence of a convergent conical ring insert on the flow and mass transfer characteristics in a tubular SOFC. The mass transfer conductance of fuel was analyzed and proposed to quantify the performance of different insert designs. The effects of the radius and offset angle of the convergent conical ring insert were examined and analyzed. We demonstrate that increasing the insert radius could increase the fuel mass transfer conductance and effectively improve the net output power of the tubular SOFC by 12% while the offset angle of the inserts exhibits a negligible impact on the fuel mass transfer conductance. Increasing the offset angle could help reduce the gas-phase pressure drop in fuel channels by 42%. The present study helps improve our understanding of the relationship between fuel mass transfer conductance and electrochemical reactions. It also proposes channel design methods based on mass transfer conductance for high-power-density solid oxide fuel cells.

Performance analyses and heat transfer optimization of parabolic trough receiver with a novel single conical strip insert

Parabolic trough collectors are the crucial component of the concentrated solar power plant, which can meet heat demand and mitigate energy shortages. However, their operation suffers from defects of high local temperature and poor wall temperature uniformity. To alleviate this issue, an enhanced parabolic trough receiver (PTR) with a novel single conical strip insert is proposed and numerically investigated in detail. Furthermore, the effects of structural parameters of the conical strip on the enhanced PTR are investigated, and multi-objective optimization is conducted to determine the optimal parameters. Finally, the performance of the optimal enhanced PTR is evaluated under different operating conditions. The results show two symmetrical longitudinal vortices are formed in the absorber tube due to the guidance of the conical strip, which is beneficial to enhancing fluid mixing and heat transfer. Accordingly, the temperature uniformity of the absorber tube and the actual efficiency are effectively improved. Compared to the smooth PTR, the tube wall temperature is dropped by up to 168 K, and the actual efficiency is improved by 3.3% at most. Moreover, the entropy generation and exergy destruction are reduced by 22.2%–49.3% and 30.6%–45.9%, respectively. This research may guide designing the PTR for efficient and safe operation.

Artificially roughened solar air heating technology – A comprehensive review

• Various artificial roughness geometries used by various researchers have been reported in current review article. • Nu and f have been calculated for the twelve roughness geometries, and a comparison has been made to opt for the best roughness among them. • At Re = 24,000 perforated V-shape baffles gave the highest Nu compare to other roughness geometries, it has Nu 6.5 times higher than the smooth SAH. • Similarly, at Re = 24,000f for protrusion roughness has been found to have the lowest value of f compared to the other roughness geometries. For various heating applications like space heating, timber seasoning, food drying, HVAC processes, water desalination processes, etc., where a low to medium heating source is required, the solar air heater is the most promising device to supply the appropriate heated working fluid with least possible cost of heating processes. Over the years, the improvement in the performance of the SHAs has become a fascinating area of research. The thermal efficiency of SAH is low because the boundary layer generation on the absorber plate causes resistance to heat transmission. Artificial roughness is the most efficient technique to break the laminar boundary layer, hence improving heat transmission. In this paper, various artificial roughness geometries used by various researchers have been reported. Based on the correlations and optimum parameters for the respective roughness provided by the respective authors, Nu, f, and thermohydraulic performance parameter have been calculated for the eleven roughness geometries using Microsoft excel 2021, and a comparison has been made to opt for the best roughness among them. At Re = 24,000, internal conical ring obstacles with impinging jets give the highest Nu compared to other roughness geometries; which has Nu 4.89 times higher than the smooth SAH. Similarly, at Re = 24,000, f for discrete reverse NACA 0040 profile roughness has been found to have the lowest value of f compared to the other roughness geometries, and it has f as 1.32 times higher compared to the smooth SAH. Thermohydraulic performance parameter ( η ) was found highest for perforated conical disc inserts with helical corrugations roughness at R e < 16000 and lowest for perforated delta roughness at Re > 16000 . The thermohydraulic performance parameter ( η ) has a maximum value of 2.440 for a hybrid broken arc with staggered ribs roughness at Re = 24,000. It has been noted that tremendous numerical and experimental work has been reported in the literature. In this study, key findings are discussed, the influence of the various roughness parameters on heat transmission and pressure drop are summarized, and recommendations are also provided for future research.

Heat transfer investigations of in-line conical strip inserts using MWCNT/water nanofluid under laminar flow condition

The compound technique employed in forced convection system has proved the enhanced heat transfer through nanofluid and conical strip inserts in order to fabricate effective and reliable compact heat exchangers. In this investigation, Multi Walled Carbon Nanotubes (MWCNT)/De-ionized (DI) water nanofluid efficiently prepared and tested for three various concentrations (φ = 0.1, 0.25, and 0.5%) by two step method. MWCNT/DI water nanofluids through conical strip insert for three pitch ratios, Y = 2.5, Y = 3.5, and Y = 4.5 in a tube is experimentally studied for heat transfer and pressure drop, in the range of Reynolds number 540–2150 under constant wall heat flux. The higher volume fraction nanofluid φ = 0.5% and DI water with conical strip inserts were numerically studied. The contours of turbulence intensity, temperature, and pressure depict the flow phenomenon and heat transfer for in-line conical strips for the pitch ratios of 2.5, 3.5, and 4.5. As a consequence of local disturbance induced by these conical strips inserts intricacies, turbulence intensity increases along the test section. Simultaneously increase in fluid viscosity of MWCNT/DI water nanofluid enhances momentum and thermal diffusion. The result shows that the average deviations for Nusselt number is5% and friction factor is 9.1% between experimental and numerical results for the pitch ratio 2.5 at 0.5% volume fraction (VF) of MWCNT/DI water nanofluid. Nanofluid exhibits better performance than base fluid also conical inserts prompts higher Nusselt number ratio of 145%. This specifies MWCNT/DI water nanofluid with complex geometry of inserts could augment heat transfer considerably along with descent pressure drop. The obtained result shows that numerical readings are in good agreement with experimental readings. Even, the thermal performance factor found to be more than unity for all the cases, particularly it reveals that 1.90 and 2.01 for experimental and numerical results respectively for the pitch ratio 2.5 at 0.5% VF of nanofluid.

Investigating thermal performance of combined use of SiO2-water nanofluid and newly designed conical wire inserts

BackgroundThe combined use of augmentation methods plays a significant role to enhance the thermohydraulic performance of thermal systems. This experimental study explores the thermohydraulic performance of a heat exchanger tube with the combined use of SiO2-water nanofluids and newly designed conical wire inserts. MethodsIn this study, a new wire coil insert with different properties from those previously proposed was created. The newly designed inserts were placed in a tube at five distances ranging from 0 to 33.6 mm and SiO2-water nanofluids were used at four volume concentrations (0.5–1.25%). The two step method was used to prepare nanofluids and the experiments were conducted in turbulent flow. Significant findings: The highest heat transfer performance was obtained in the conical wire inserts with pitch ratio of 0, and the least friction loss was obtained in the conical wire inserts with pitch ratio of 4. The best Performance Evaluation criteria was 1.75 at Reynolds number of 3338 and volume concentration of 1.25% for conical wire inserts with pitch ratio of 0. Moreover, the use of nanofluids provided a remarkable heat transfer rate with increased Reynolds number at high volume concentrations, whereas nanofluids at low volume concentrations slightly affected the heat transfer rate and pressure drop. The combination of two techniques presented a promising option for improving the hydrothermal qualities of the heat exchanger.

Performance characteristics of a thin‐layered radial porous burner with different strategies for fuel‐air mixture supply

A recent surge of interest is focused on developing radiant burners that may replace traditional open flame burners because of their ability to interchangeably use a wide range of fuels with improved emissions and the overall efficiency of combustion appliances. This research focuses on identifying conditions under which a radiant burner with a thin‐layered radial porous emitter operates in the internal combustion mode with increased radiation efficiency alongside decreased noise and NOx emission. The way the fresh mixture distributes over the cylindrical cavity of the emitter is the main factor affecting the burner performance. Two strategies for fuel‐air mixture supply were considered: (i) co-axial feed of turbulent flow through the open end of the cylindrical emitter using a divergent annular nozzle; (ii) distributed radial feed of laminar flow through a thin‐layered conical porous insert located inside the cavity of the emitter. The burner performance (radiation efficiency, NOX, and noise emissions) was experimentally studied in the ranges of thermal power of 4.0–9.1 kW and equivalence ratio of 0.5–1.0, which corresponds to the range of the emitter temperature from 500 to 1190 K. It was established that the distributed radial feed of fresh mixture dramatically reduced the noise emission, markedly improved the uniformity of the emitter temperature, and slightly increased the radiation efficiency of the burner. The improved combustion performance makes the thin‐layered radial porous burners relevant for application in domestic heating appliances.

A review study on the performance enhancement of solar parabolic trough receiver by various passive techniques

This is a new era where the world’s energy consumption is so high and is likely to increase over 60% of current consumption by the year 2030. Therefore, renewable energy should be used most frequently. The most preferred alternative to fossil fuels is solar energy but converting solar energy into usable form is the most challenging part. The conversion to thermal energy is the one option. In the area of solar thermal power generation, a solar parabolic trough (SPT) collector is an effective method. Also, the use of passive methods to enhance the thermal performance of these parabolic trough receivers is currently the researcher’s interest This review study is focused on different types of geometrical modification (Artificial roughness) used to enhance the thermal performance of SPT receivers. Based on the extensive study it has been found that conical strip insert is a very broad field for research as it can enhance the thermal performance up to 5–10 times. Also there are parameters associated with the conical strips like shape, pitch, angle of twist, slant angle, geometry angle, etc. which can contribute to better performance when used in SPT receiver.

Effect of various inserts on flow behavior of Fe2O3 beads in a three-dimensional silo subjected to cyclic discharge- Part I: Exploration of transport properties

Optimizations of uniform velocities and residence times of oxygen carriers in chemical looping reactors are key factors. This study firstly applies inserts to improve the flow performance of Fe2O3 beads in an actual 3D reactor. This study proposes a novel DEM approach with null friction boundaries to investigate transport properties of Fe2O3 beads in a reactor with inserts subjected to cyclic discharge. Six inserts were analyzed, e.g., conical insert, disk insert, BINSERT, hollow cylinder insert, and hollow silo insert, as well as no inserts for comparison, respectively. Results revealed that the flow of Fe2O3 beads in the 3D silos with the conical insert, disk insert, and BINSERT exhibited superior uniform velocity profiles. Furthermore, the corresponding granular temperatures and residence times were evener. The installation of these three inserts is more conducive to the uniform discharge of the Fe2O3 beads within a looping reactor.

Effect of various inserts on flow behavior of Fe2O3 beads in a three-dimensional silo subjected to cyclic discharge- Part II: Exploration of internal dynamic properties

This paper investigates internal dynamical properties of Fe2O3 beads in 3D silos subjected to cyclic discharge by using discrete element modeling. The effect of inserts on the internal dynamic properties was explored. Six types of inserts, including the absence of inserts for comparison, were adopted in this study: conical insert, disk insert, BINSERT, hollow cylinder insert and hollow silo insert. Results reveal that the installation of inserts affects wall tractions, solid volume fraction and coordination number, depending on insert geometry and placement position. The gradients in the wall tractions are larger in the hopper region than in the cylindrical region. The hollow cylinder and hollow silo inserts separate the granular flows, leading to smaller solid fractions and exhibiting more uneven distributions in coordination number. The silos with conical and disk inserts generally show larger coordination numbers than the other silos. The effect of inserts on friction mobilization is markedly limited.

Conical Spring Inserts Effect on the Thermo- hydraulic Characteristics in Circular Copper Tube

Experimental and numerical investigation was conducted to study the thermo-hydraulic characteristics in circular tube fitted with conical spring inserts. The dimensions of circular copper tube are 100cm, 2.2cm and 2.4 cm which represent the length, inner and outer diameters respectively. The length of insert was 15cm, while the conical spring has 16mm diameter gradually decreases to 6mm with the length and the pitch between the coils was 20mm. The diameter of wire used to fabricate the conical spring insert was 4mm. Those inserts were arranged into eight categories (A1 to A8). In the numerical part, the governing equations were solved by using commercial ANSYS-Fluent package (2019 R3) with the assistance of solid works and Gambit software program. The finite volume approach was used in solving the equations to predict the pressure flow, heat transfer and temperature distribution along the tube. Experimental work included design and built a test platform for the experimental measurements. The aim of experimental study was to predict the behavior of heat transfer and pressure in the tube with two cases, plain tube and inserted tube at the effect of different parameters. All experimental tests were conducted at turbulent flow fully developed. The range of Reynolds number and heat flux were (3542-7522) (4549-10576 W/m^2) respectively. The results showed that the best augmentation in heat transfer was by using a category A5 of conical spring insert compared with plain tube. Results show good agreement between the numerical and experimental results with an error of 8%. Also results showed that the Nusselt number increases as the Reynolds number increasing.

Thermo-Fluidic Modelling of a Heat Exchanger Tube with Conical Shaped Insert having Protrusion and Dimple Roughness

In the present work, thermo-fluidic behavior of a heat exchanger tube with conical shaped insert has been investigated with the help of finite volume method. To enhance the heat transfer rate, two different types of roughness has been used in conical insert i.e. protrusion and dimple roughness. A three-dimensional computational model with RNG turbulence model is used for the simulation and it has been performed for three different diameters (3 mm, 6 mm and 9 mm) and two different pitch space (120 mm and 180 mm) for both protrusion and dimple roughness. The present model has been validated with Dittus-Boelter equation and with Blasius equation for Nusselt number and friction factor, respectively. For a constant heat flux of 1200 W/m2, effect of roughness, diameter and pitch on Nusselt number and friction factor has been predicted for Reynold number range of 5000 to 30000. From the result, it is found that, the protrusion shaped roughness has better thermal performance factor than dimple shape and diameter of 6 mm has performed better than 3 mm and 9 mm for both the cases of roughness due to favorable flow dynamics.

Heat transfer enhancement and entropy generation analysis of a tube with perforated conical inserts

ABSTRACT The present study examines the flow and thermal characteristics of a tube containing perforated conical inserts by varying the Reynolds number in the range of 4000–20000. The perforated conical insert having (d/D) ratio of 0.3, (p/D) ratio of 2, (x/L) ratio of 0.25, and N = 6 showed the minimum entropy generation. Second law analysis showed that the solid inserts of a lower pitch to diameter ratio are suitable to transfer high energy transfer at lower Reynold’s number, whereas the perforated conical inserts are found to be effective at higher Reynolds numbers. Empirical correlations are developed for solid and perforated conical inserts.