Double Concentric Tube Research Articles

Experimental and numerical investigation on the thermal performance of triple tube heat exchanger equipped with different inserts with WO3/water nanofluid under turbulent condition

A novel curve tube design called Triple Tube Heat Exchanger was investigated to identify the thermofluidic characteristics in the current paper. This research analysis comprises of both computational fluid dynamics and experimental results. A three-dimensional computational fluid dynamics model was developed using Ansys R19.1 (fluent) research package, and the k-epsilon model is used to realize the thermofluidic characteristics. In this new design, an additional tube is introduced between a double concentric tube heat exchanger. The complete analysis is done under consideration of turbulent fluid to fluid heat transfer conditions. The influence of different thermal parameters such as overall heat transfer and effectiveness were the main points of research interest by using WO3/water nanofluid with different novel inserts like twisted tape, rib, and porous plate. The thermodynamic effect of nanofluid was considered under the concentration range of 0.5%–3.0%. The computational fluid dynamics method is used to simulate the process, and experimental data is used to validate it. The result shows that the maximum overall heat transfer rate and effectiveness were 1767.91 W/m2K, 1702.71 W/m2K, and 1.86, 1.79, respectively, at 1% optimized volume concentration with WO3/water nanofluid by using rib type insert during experimental and computational fluid dynamics methods, respectively. The maximum thermal performance factor by using nanofluid in the rib type insert was observed at 0.75. The study shows an enhancement of 11.84%, 12.38%, and 14.56%, 14.30% in overall heat transfer and effectiveness by using a rib-type insert for both experimental and computational fluid dynamics methods, respectively, in comparison to without using inserts. There was also a progressive decrement in friction factor during the increment in mass flow rates.

Experimental Investigation on Triple Concentric Tube Heat Exchanger with Helical Baffles

A heat exchanger is a device used to transfer thermal energy between two or more liquids, between a solid surface and a liquid, or between solid particles and a liquid at different temperatures and in thermal contact where shell and tube heat exchangers contain a large number of tubes packed in a jacket whose axes are parallel to those of the shell. Heat transfer occurs when one fluid flows into the pipes while the other flows out of the pipes through the jacket. In industry, three-tube heat exchanger tubes are used as condensers, evaporators, sub cooler, heat recovery heat exchangers, etc. The three concentric tube heat exchanger is a constructively modified version of the double concentric tube heat exchanger as an intermediate tube adds some advantages over the double tube heat exchangers in that it is larger tube surface area heat transfer per unit of length. In the present study, the triple tube heat exchanger is further modified by inserting helical baffle over the surface of one of the tubes and observed turbulence flow which may lead to high heat transfer rates between the fluids of heat exchanger. Further, the Reynolds number, Nusselt number, friction factor of the flow at different mass flow rates of the hot fluid while keeping a constant mass flow rate of cold and normal temperature fluids were calculated. It was found that as the mass flow rate of the fluid increases the Reynolds number increases, the turbulence in the flow will increase which will cause the intermixing of the fluid, higher the rate of intermixing, more will be the heat transfer of the system.

Characterization of the Heat Transfer Process in a Concentric Tube Heat Exchanger for 2-MW Gas Engine Waste Heat Recovery

The increase in the energy efficiency of internal combustion engines has taken great importance in recent years due to the need to reduce fuel consumption and environmental impact. In this study, a parametric study assisted by CFD simulation has been carried out using the open-source OpenFOAM®, applied to a heat exchanger composed by a double concentric tube. It is made of copper, and the transport fluids are exhaust gases and Theminol-75 thermal oil. A diverse group of geometric configurations has been performed by varying the basic parameters of the heat exchanger, and the results obtained has allowed finding a set of equations and curves, whose mathematical model reveals flow and heat transfer characteristics, such as the Reynolds number, the Nusselt number, and the convective heat transfer coefficient h. The equations obtained from the curves have a very high degree of acceptance within the limits of this study, allowing the geometrical parameters to be varied within the standards established for commercial copper pipes. The results obtained show a degree of accuracy of 93% between the limit values as well as for the flow regimes and physical states of the matter indicated.

Analysis of Shell and Double Concentric Tube Heat Exchanger Using CFD Application

This study focuses on CFD analysis in the field of the shell and double concentric tube heat exchanger. A commercial CFD package was used to resolve the flow and temperature fields inside the shell and tubes of the heat exchanger used. Simulations by CFD are performed for the single shell and double concentric tube.
 This heat exchanger included 16 tubes and 20 baffles. The shell had a length of 1.18 m and its diameter was 220 mm. Solid Works 2014, ANSYS 15.0 software was used to analyze the fields of flow and temperature inside the shell and the tubes. The RNG k-ε model was used and it provided good results. Coarse and fine meshes were investigated, showing that aspect ratio has no significant effect. 14 million elements were used in the mesh. A comparison was made between the profiles of temperature and velocity for the experimental and results of the model and it had an acceptable adaptation.

Multiple-Criteria Decision Analysis and characterisation of phase change materials for waste heat recovery at high temperature for sustainable energy-intensive industry

A latent heat storage system based on Phase Change Materials (PCMs) is proposed to increase the energy and environmental efficiency by recovering and storing waste heat from combustion gases or other surplus sources at in the energy-intensive industries (EII), currently unused. The final configuration design is specifically adapted to the plant operational requirements, by means of a methodology combining the search of the best conceptual design and a proper selection of core PCMs. To that end, a selection of suitable PCM is carried out by using characterisation techniques and thermal stability testing. Furthermore, relevant key factors are weighted by an in-house Multiple-Criteria Decision Analysis (MCDA) to define the most promising design options to be implemented in two plants belonging to the EII sector. For the ceramic sector, the design resulted in a shell-and-tube system with 1188 kg of a PCM melting at 885 °C and encapsulated in double concentric tubes, involving a storage capacity of 227 MJ. Similarly, 1606 kg of PCM, whose phase-change temperature is 509 °C, is selected for the steel sector providing a PCM-TES system capable to store 420 MJ.

Thermal Analysis and Performance Evaluation of Triple Concentric Tube Heat Exchanger

Triple concentric-tube exchanger (TCTHE) is an improved version of double concentric tube heat exchanger (DCTHE). Introducing an intermediate tube to a DCTHE provides TCTHE and enhances the heat transfer performance. Recognizing the need of experimental results, extremely scarce in the literature and essential to validate theoretical analyses, the aim of this work is to investigate thermal behavior of TCTHE. The present study includes design, development and experimental analysis of TCTHE for oil (ISO VG 22) cooling application required for industrial purposes. It comprises of water (cooling fluid) flowing through innermost tube as well as outer annulus and oil (hot fluid) flows through inner annulus. The experimental studies of the temperature distribution for three fluids along the length and heat transfer characteristics for TCTHE under insulated condition for counter current flow mode are carried out and discussed. The effect of change in oil (hot fluid) temperatures is analyzed keeping water inlet temperatures same at various operating conditions. The experiments have been conducted by varying flow rate of one of the fluids at a time and keeping other two fluid flow rates constant. The results are expressed in terms of temperature variation for all three fluids along the length. The effect of change in hot fluid inlet temperature is expressed in terms of heat transfer rate variation with respect to Reynolds number. The variation of non-dimensional parameters as temperature effectiveness and thermal conductance with respect to Reynolds number is also presented in this paper. Theoretical studies are carried out for evaluation of heat transfer rate using empirical correlations. Experimental validation is carried out for degree of cooling at different Reynolds numbers with theoretical analysis.

CFD Application on Shell and Double Concentric Tube Heat Exchanger

This work is concerned with the design and performance evaluation of a shell and double concentric tubes heat exchanger using Solid Works and ANSY (Computational Fluid Dynamics).
 Computational fluid dynamics technique which is a computer-based analysis is used to simulate the heat exchanger involving fluid flow, heat transfer. CFD resolve the entire heat exchanger in discrete elements to find: (1) the temperature gradients, (2) pressure distribution, and (3) velocity vectors. The RNG k-ε model of turbulence is used to determining the accurate results from CFD.
 The heat exchanger design for this work consisted of a shell and eight double concentric tubes. The number of inlets are three and that of outlets are also three for all the fluids that pass through the heat exchanger.
 A comparison was made for the numerical and experimental results and it was found that the percentage error for the hot oil outlet temperature was (6.8%) and the percentage error was (- 21%) for cold water outlet temperature.

Exergy analysis of double tube heat exchanger for parallel flow arrangement.

This paper presents the analysis of exergy according to second law of thermodynamics for a double concentric tube heat exchanger experimentally. For this purpose to study the heat exchange process between two fluid mediums separated by a solid partition for parallel flow arrangement, an experimental setup was fabricated as per designed considered to measured data. In this considered double concentric tube heat exchanger, hot water and cold water flowing through inner and outer tube respectively and heat exchange takes place from hot fluid medium to cold fluid medium. Here the wall tube conductive resistance is assumed as negligible. The investigation was performed for mass flow rate of cold water ranging from 0.0326 kg/s to 0.572 kg/s and mass flow rate of hot water ranging from 0.016 kg/s to 0.479 kg/s. The effects of various parameters such as rate of entropy generation, number of entropy generation, effectiveness of heat exchanger, and losses of exergy are observed by exergy analysis. The governing equations have been employed to solve analytically for obtaining the energy and exergy analysis parameters. It is expected that this study might be helpful for further related work.

Study and Analysis of Concentric Shell and Double Tube Heat Exchanger Using - Al 2 O 3 Nanofluid

Heat exchanger is an important device in the industry for cooling or heating process. To increase the efficiency of heat exchanger, nanofluids are used to enhance the convective heat . transfer relative to the base fluid. - Al2O3/water nanofluid is used as cold stream in the shell and double concentric tube heat exchanger counter current to the hot stream basis oil. These nanoparticles were of particle size of 40 nm and it was mixed with a base fluid (water) at volumeconcentrations of 0.002% and 0.004%. The results showed that each of Nusselt number and overall heat transfer coefficient increased as nanofluid concentrations increased. The pressure drop of nanofluid increased slightly than the base fluid because of the low concentration used.

Analysis of the heat transfer in double and triple concentric tube heat exchangers

The tubular heat exchangers (shell and tube heat exchangers and concentric tube heat exchangers) represent an important category of equipment in the petroleum refineries and are used for heating, pre-heating, cooling, condensation and evaporation purposes. The paper presents results of analysis of the heat transfer to cool a petroleum product in two types of concentric tube heat exchangers: double and triple concentric tube heat exchangers. The cooling agent is water. The triple concentric tube heat exchanger is a modified constructive version of double concentric tube heat exchanger by adding an intermediate tube. This intermediate tube improves the heat transfer by increasing the heat area per unit length. The analysis of the heat transfer is made using experimental data obtained during the tests in a double and triple concentric tube heat exchanger. The flow rates of fluids, inlet and outlet temperatures of water and petroleum product are used in determining the performance of both heat exchangers. Principally, for both apparatus are calculated the overall heat transfer coefficients and the heat exchange surfaces. The presented results shows that triple concentric tube heat exchangers provide better heat transfer efficiencies compared to the double concentric tube heat exchangers.

Entransy Dissipation of Shell and Double Concentric Tubes Heat Exchanger

Entransy Dissipation of Shell and Double Concentric Tubes Heat Exchanger

Entransy dissipation of Shell and Double Concentric Tube Heat Exchanger Calculations and Analysis

Shell-and-double concentric tube heat exchanger is one of the new designs that enhance the heat transfer process. Entransy dissipation is a recent development that incorporates thermodynamics in the design and optimization of heat exchangers. In this paper the concept of entransy dissipation is related to the shell-and-double concentric tube heat exchanger for the first time, where the experiments were conducted using hot oil with temperature of 80, 100 and 120°C, flow rate of cold water was 0.667, 1, and 1.334 kg/m3 respectively and the temperature of inlet cold water was 20°C. The entransy dissipation rate due to heat transfer and to fluid friction or pressure drop was studied.

Optimisation of the design of shell and double concentric tubes heat exchanger using the Genetic Algorithm

This paper presents the use of Genetic Algorithm in the sizing of the shell and double concentric tube heat exchanger where the objective function is the total cost which is the sum of the capital cost of the device and the operating cost. The use of the techno-economic methods based on the optimisation methods of heat exchangers sizing allow to have a device that satisfies the technical specification with the lowest possible levels of operating and investment costs. The logarithmic mean temperature difference method was used for the calculation of the heat exchange area. This new heat exchanger is more profitable and more economic than the old heat exchanger, the total cost decreased of about 13.16 % what represents 7,250.8 euro of the lump sum. The design modifications and the use of the Genetic Algorithm for the sizing also allow to improve the compactness of the heat exchanger, the study showed that the latter can increase the heat transfer surface area per unit volume until 340 m2/m3.

Experimental studies of ignition and explosion in a water column bubbling with hydrogen and oxygen

A bubble column is constructed and fitted with five sets of igniters and pressure sensors to study the ignition and explosion of hydrogen/oxygen bubbles in water. Two pressure-resistant glass windows are also fitted in the central section of the column for visualization of the ignition. A loop is built to circulate water through the column. A double concentric tube is used to feed oxygen, hydrogen, and water. Ignitions at different locations, oxygen/hydrogen molar ratios and flow rate are also performed. The results find that significant overpressure is generated when large oxygen/hydrogen bubbles or slugs contacted the fusing Nichrome wire igniter. The explosion overpressure also causes strong pulsation of the liquid in the whole column. Finely disperse bubbles are however prone to ignition and do not produce any overpressure. Co-current flow of water helps to minimize the formation of large bubbles or slugs and provides a safer means for reacting hydrogen and oxygen. The results are expected to be useful for scaling up the direct synthesis of hydrogen and oxygen into hydrogen peroxide.

Determination of trace amounts of urea by using flow injection with chemiluminescence detection.

Reaction between urea and hypobromite in alkaline solution was found to produce chemiluminescence with a maximum wavelength at 510 nm. A simple chemiluminescence detection method was used for the determination of urea in human urine and natural aqueous samples, which combined this chemiluminescence reaction with a flow injection analysis system. The relative standard deviation for 5 x 10(-7) mol dm-3 urea is 1.9% (n = 6), and the detection limit is 9.0 x 10(-8) mol dm-3 (3Sr). As this chemiluminescence reaction is very fast, a double concentric tube mixer connected directly to the chemiluminescence cell was used to mix urea solution and hypobromite solution. Alkylamines, carboxylic acids and most amino acids do not interfere in the determination. Ammonium ion interferes, but the sensitivity for ammonium ion is only 1% of that for urea. The interference from ammonium ion was removed sufficiently by using an on-line cation-exchange column.