Double Tube Heat Exchanger Research Articles

Review on Thermal Performance of Nanofluids With and Without Magnetic Fields in Heat Exchange Devices

Addition of nanoparticles into a fluid can improve the heat transfer performance of the base fluid in heat exchangers. In this work, the preparation method and process of nanofluids are introduced, and thermal properties of nanofluids, such as thermal conductivity and viscosity, are discussed deeply. This paper summarizes various theoretical models of thermal conductivity and viscosity of nanofluids. A comprehensive literature survey on applications and limitations of nanofluids has been compiled. This paper also aims to review the natural and forced convective heat transfer characteristics of nanofluids with and without magnetic fields. The discussion for the natural convective heat transfer of nanofluids focuses on the heat transfer performance of non-conventional enclosures and electric heaters. The effects on heat transfer due to variations of heated walls are also investigated. Specific applications of nanofluids in a tube with trapezoidal ribs, double-tube heat exchangers, and plate heat exchangers have been reviewed and presented in a discussion about forced convective heat transfer. The previous results show that the inlet temperature of nanofluids obviously affects the heat transfer characteristics of double-tube heat exchangers, whereas a multi-walled carbon nanotube–water nanofluid shows significant advantages in plate heat exchangers. Finally, this paper studies natural convective heat transfer of magnetic fluids in a square cavity and forced convection heat transfer in a straight tube and a corrugated structure under the action of magnetic fields. It is found that the heat transfer performance of an Fe3O4–water nanofluid is enhanced when a magnetic field is applied to the corrugated plate heat exchangers, and the pressure drop can be reduced by around 10%. It is recommended that natural convection of magnetic fluids needs to be investigated experimentally in a real cavity and a corrugated channel under the influence of a magnetic field. In addition, studies of alternating magnetic field are recommended to reveal any improvements of thermal performance of magnetic fluids in heat exchange devices. This review puts forward an effective solution for improvement of the thermal performance of heat transfer equipment and serves as a basic reference for applications of nanofluids in heat transfer fields.

Performance of a Double‐Tube Heat Exchanger with Staggered Helical Fins

AbstractA novel double‐tube heat exchanger with staggered helical fins (DTHE‐SHF) is proposed. The mechanism of drag reduction and heat transfer enhancement was analyzed based on the theory of field synergy. Numerical simulations were conducted to study the thermal performance of the DTHE‐SHF. The effects of torsion angle and number of the SHF were investigated. The results indicated that, compared with the double tube heat exchanger with traditional straight helical fins (DTHE‐TSHF), the pressure drop of the DTHE‐SHF is reduced significantly, and the comprehensive performance of the DTHE‐SHF is improved by 10 %–30 %. The average synergy angle between the velocity field and the pressure field is optimized.

Heat transfer characteristics of PCM slurry using super-hydrophobic gel particles under laminar flow✰,✰✰

To prevent hydrophobic phase change materials (PCMs) from phase separation in water, a novel technique based on a super-hydrophobic gel, known as marshmallow-like gel, has been suggested as an effective solution. In this study, marshmallow-like gel particles, which only adsorb hydrophobic substances, were used as a carrier of a hydrophobic PCM (paraffin) to evaluate their heat transportation performance. The tetradecane-adsorbed marshmallow-like gel particles showed a latent heat of 123 kJ·kg–1, which is 56% of that of pure tetradecane (219 kJ·kg–1). Sodium carboxymethyl cellulose (CMC) was used as a dispersant for the superhydrophobic gel in water. An aqueous soliton of CMC (0.6 wt%) was used to prepare the slurry containing 10 wt% of tetradecane-adsorbed marshmallow-like gel particles. The heat transfer of the slurry under laminar flow was characterized, and experiments were performed in a homemade heat transfer apparatus based on a double-tube heat exchanger with an inner tube diameter of 8 mm. The heat transfer coefficient was compared with the results of the CMC solution without the particles. Due to the latent heat of tetradecane, the particles with hydrophobic PCM showed a positive effect on heat transfer characteristics. Additionally, an adequate model to describe the heat transfer under laminar flow was proposed using a modified Prandtl number to consider the effect of latent heat.

Experimental Analysis of Double Pipe Heat Exchanger with V-cut Twisted Tape Inserts using PCM Dispersed Nanofluids

The performance of a double tube heat exchanger with V-cut twisted tape inserts (VCTT) and phase change material (PCM) dispersed nanofluid is investigated experimentally. The three water-based Al2O3, PCM, and Al2O3+PCM nanofluid with different concentrations (0.01-0.1% vol.) are used. The impacts of different geometric parameters, i.e., twist ratio (TR), depth ratio (DR) and width ratio (WR) of VCTT inserts on Nusselt number (Nu), friction factor (f) and entropy generation are examined. The outcomes expose that Nu and f increase as particle concentration increases and twisting ratio decreases. A higher Nu and f are generated by a higher DR or a lower WR. In all cases, the entropy generation of nanofluid is found to be lower than that of water. For all working fluids, a rise in TR, a fall in DR, and a rise in WR increases overall entropy generation.

Thermal Performance Analysis of Triple Heat Exchangers via the Application of an Innovative Simplified Methodology

Despite the double tube heat exchangers, in the triple tube heat exchangers, there are three fluids, and the methodology based on the assessment of the logarithmic mean temperature difference is no longer applicable. Moreover, in triple tube heat exchangers, there are two overall heat transfer coefficients dependent on each other. As such, it is necessary to solve them simultaneously, thus making the evaluation of the thermal performance of triple tube heat exchangers more complex compared to double tube heat exchangers. Among the proposed approaches in the literature to solve this issue, one of the most powerful and commonly adopted in several engineering applications is the parameter estimation procedure. Nevertheless, for the specific implementation examined in our analysis, a thorough numerical model of the triple tube heat exchanger was required to apply the inverse procedure properly. Furthermore, it is mandatory to measure the temperature of the three fluids at the inlet and outlet sections. In so doing, the inverse procedure can be successfully applied to the characterisation of triple tube heat exchangers tested in well-equipped research labs; however, its application to heat transfer devices operating in industrial facilities can be difficult. In order to overcome this limitation, an innovative parameter estimation technique that enables the evaluation of the thermal performance of this type of heat transfer devices is presented. The suggested methodology is based on a simple model of the triple tube heat exchanger in which an equivalent double tube heat exchanger is considered, thus requiring only four temperature measurements. The results obtained by applying this simplified methodology are numerically validated and compared to those obtained using a comprehensive model.

Numerical analysis on heat transfer performance of industrial double-tube heat exchanger using CNT: Newtonian/non-Newtonian hybrid nanofluids

Numerical analysis on heat transfer performance of industrial double-tube heat exchanger using CNT: Newtonian/non-Newtonian hybrid nanofluids

Simulation study on the effect of fins on the heat transfer performance of horizontal dual-inner-tube latent thermal energy storage heat exchangers

Compared with the traditional horizontal double-tube heat exchangers, the horizontal dual-inner-tube latent thermal energy storage (LTES) heat exchangers can effectively shorten the melting time of the phase change materials (PCMs). This paper analyzed the liquid phase distribution, temperature field, melting rate and heat storage about finless horizontal dual-inner-tube latent thermal energy storage heat exchangers during the melting, and researched the effects of the fin position and number on melting progress and heat storage performance. The results showed that compared with the variation of fin number, the reasonable fin arrangement is better to improve heat transfer performance, and the heat transfer performance reaches to the optimal value when the single fin is placed at the bottom of the lower tube, which can shorten the melting time by 23.91% compared with the finless condition, but the increase of fin number on the basis of the optimal single fin arrangement only shortens the melting time by 1,2%. Additionally, it also obtained that the time of the high melting rate reduces by 9.14% when the fin is installed in the middle of the exchangers body, which weakens the effect of strengthening heat transfer. These results indicate that the less fins, if the arrangement is designed properly, can be as efficient as more fins in horizontal dual-inner-tube LTES heat exchangers.

Enhancement of Double-Pipe Heat Exchanger Effectiveness by Using Water- CuO

This study utilized Nanofluid as a cold fluid in evaluating the counter flow double tube heat exchanger, which was one meter long, had an outer diameter of 19 mm, and an inner diameter of 9.5 mm made from copper. Water was the basic fluid, with the size of 40 nm and a volume concentration of (0.5%) and (1%), respectively, of CuO nanoparticles being added. At 2 L/min and 4 L/min and 6 L/min, the Nanofluid flows inside the inner tube. At 20°C, the Nanofluid enters the heat exchanger. The flow of hot water into the heat exchanger is 4 L/min through an annular space with an entry temperature of 65 °C. to achieve better heat exchanger performance, the experimental results will be compared to those obtained when using pure water. The improvement in performance with Nanofluid as a working fluid was discovered during experiment analysis. (40%) maximum heat exchanger effectiveness obtained at Nanofluid flow rate of 2 L/min has (0.5%) volume concentration ,effectiveness (54%) at (1%) a volume concentration.

Experimental analysis on heat exchanger using Al2O3-CuO hybrid nano coolant

This research work gives the insight on heat transfer performance of nano coolants using hybrid nanoparticles Al2O3-CuO in mixture ratio 20:80, 50:50, 80:20 respectively, at 0.1 vol% of 5 liter base fluid (mono ethylene glycol (MEG)+ deionized water (DW)) on a double pipe shell and tube heat exchanger. Nanoparticles were prepared using ball milling, magnetic stirring and ultra-sonication. The average diameter of crystallites of hybridized nanoparticles was in the range of 25 nm to 35 nm, determined using an X-ray diffractometer. Specific heat capacity, density and kinematic viscosity were determined using differential scanning calorimetry, Redwood viscometer and precision balance, respectively. Modifications were done on the cold side of the heat exchanger by installing a tank at the top for the nano coolant. The flow rates on cold fluid side was fixed to 1.2 L/min and hot fluid side varied from 0.6 L/min to 1.2 L/min operated on both, parallel flow and counter flow arrangement. Coolant sample 80:20 (Al2O3:CuO) amongst all the samples possessed highest rate of effectiveness with an increment of 35% when compared to traditional sample DW + MEG and also with water. Highest logarithmic mean temperature difference (LMTD) and overall heat transfer coefficient (OHTC) were observed for the above sample. Smidgen amount of agglomeration had been observed while conducting the experiment.

Heat transfer analysis of double tube heat exchanger with wavy inner tube

The effect of the design on the heat transfer is numerically investigated by using the wavy inner tube in a double-pipe heat exchanger. A wavy inner tube was used in the design to give a turbulent effect to the fluid along the inner tube of a double tube heat exchanger. In numerical study, ANSYS 12.0 Fluent code program was used, and the basic protection equations were solved for steady-state, 3-D and turbulent flow conditions. The study was examined at Reynolds numbers ranging from 2700-5300. The obtained results were compared with the experimental data performed under the same conditions. As a result of this comparison, after it was seen that the results obtained from the numerical analysis and the experimental results were compatible with each other, the wave number of the inner tube was increased and analyzed with the ANSYS fluent code program. When the data obtained as a result of the analyzes were evaluated, it was seen that the highest heat transfer was obtained from the 16 wave tube heat exchanger, which has the highest number of waves and under counter flow conditions. The increase in heat transfer increased by 270% compared to the straight tube.

A Simple Solution for Heat Transfer in a Triple Tube Heat Exchanger

Triple tube heat exchangers in general perform better when compared to double tube heat exchangers, mainly because they improve the heat transfer due to the passage of additional fluid and also of its larger heat transfer area per length unit. Nevertheless, for triple tube heat exchangers, the analytical solutions available in the literature are limited to specific boundary conditions or are cumbersome. Therefore, this work aims to obtain a compact form of the analytical solution, suitable for co-current and counter-current flow arrangements. The solution form is developed based on a solution from literature for a co-current moving bed heat exchanger model, through analogies with triple tube heat exchangers. From the solution form, explicit expressions for the crossover points are also obtained. For a better understanding of the underlying physics, a scale analysis is performed. When compared to experimental data and more complicated solutions from literature, the obtained results presented good agreement.

Enhancement of heat transfer of double tube heat exchanger with inner twisted spiral tube

Enhancement of heat transfer of double tube heat exchanger with inner twisted spiral tube

Experimental study of heat transfer and pressure drop analysis of the air/water two-phase flow in a double tube heat exchanger equipped with dual twisted tape turbulator: Simultaneous usage of active and passive methods

In this paper, simultaneous use of active and passive methods for enhancing the thermal performance of a double-tube heat exchanger was investigated. This was done by injecting air bubbles into the working fluid and utilizing a dual twisted tape turbulator. Effects of these two procedures on the Nusselt number and pressure drop were evaluated when applied simultaneously. We further studied the effect of cold water flow rate on thermal parameter. The results indicated that the Nusslte number increases with the decrease of turbulator ratio and increases with the increase of bubble injection flow rate, cold water flow rate and the Reynolds number. The findings further showed that the simultaneous use of the two methods could increase the Nusselt number by 98–114%, 3–14%, and 20–39% compared to the cases with a simple tube heat exchanger, a turbulator-equipped heat exchanger (without bubble injection), and a heat exchanger with bubble injection (without turbulator), respectively.

An advanced turbulator with blades and semi-conical section for heat transfer improvement in a helical double tube heat exchanger

An advanced turbulator with blades and semi-conical section for heat transfer improvement in a helical double tube heat exchanger

A Numerical Study for a Double Twisted Tube Heat Exchanger

The thermal and fluid physiognomies of a double twisted tube heat exchanger was examined numerically. Twisted engineering is a wide-use method to improve heat transfer in heat exchangers. A counter-flow mode utilizing hot water in the inner tube and cold air in the outer tube was considered. This study aims to progress the thermal performance of the double tube heat exchanger by using twisted tubes instead of plane tubes. The heat exchanger was (1m) length, outer diameter (0.05m) and inner diameter (0.025m), both with a thickness (0.004m). It was tested for different values of twist ratios (Tr= 5, 10, and 15 respectively) and Reynolds numbers (Re=5000 to 30000). The Navier - Stockes and energy equations besides the turbulence model in demand for modelling this physical problem. ANSYS Fluent code was used for the numerical simulation. The results showed that the twisted tube heat exchanger showed increasing heat transfer compared with a plain tube heat exchanger. It was found that the cold outlet temperature, pressure drop and effectiveness are increased as the twist ratio increases.

A comparative study between the effect of swirl flow and axial flow on the rate of diffusion controlled corrosion in a double tube heat exchanger

ABSTRACT The rate of diffusion-controlled corrosion of an annulus under swirl flow was studied by measuring the limiting current of the cathodic reduction of potassium ferricyanide depolarizer in the presence and absence of polyox WSR-301 drag-reducing polymer. It was found that the rate of diffusion-controlled corrosion of the inner cylinder of the annulus increases with increasing swirl flow solution velocity and decreases with increasing the active height of the cylinder. The data in the absence of polymer (blank solution) under swirl flow were fitted by a dimensionless equation. The importance of this equation in predicting the rate of diffusion-controlled corrosion and the corrosion allowance during the design of the swirl flow equipment was highlighted. For a given set of conditions, the rate of accelerated swirl flow corrosion was much higher than that of axial flow. Drag reducing polymer was found to inhibit the rate of diffusion-controlled corrosion by a maximum of 23%, if other benefits of the polymer are considered such as the decrease in the shear stress and the associated decrease in the erosion-corrosion tendency besides the decrease in pressure drop and pumping power requirement it may be concluded that the use of drag-reducing polymers in industry is worthwhile.

Boiling heat transfer of R32 and R22 in spiral corrugated tube with a vertical groove

In this paper, a three-dimensional steady-state boiling model of the spiral corrugated tube with a vertical groove is established by ANSYS Fluent 18.0. The model is a double tube structure, the water flow in the outer tube, the refrigerant flow in the inner tube, and the inner tube is a new type of spiral corrugated tube with a vertical groove inside the groove. Firstly, the physical properties difference between R32 and R22 is analyzed. Subsequently, the boiling heat transfer characteristics of R22 and R32 in the vertical groove inner spiral corrugated tube with different pipe diameters are studied, including the velocity of the inner pipe, the Reynolds number of the outer pipe, and the saturation temperature. Therefore these studies have laid the foundation for the application of R32 in double-tube heat exchangers.

Evaluation and Improvement of PCM Melting in Double Tube Heat Exchangers Using Different Combinations of Nanoparticles and PCM (The Case of Renewable Energy Systems)

In this work, the melting process of phase change material (PCM) in double tube heat exchangers was investigated and evaluated through the use of different combinations (1, 2, 3% Nano-Enhanced PCM and 1, 3, 5% Nano-HTF) of GQD, as well as SWCNT nanoparticles and PCM (RT82). In this study, the effect of three different methods, namely the dispersion of nanoparticles in PCM (nano-enhanced PCM), the dispersion of nanoparticles in HTF (nano-HTF), and the simultaneous dispersion of nanoparticles in PCM and HTF (nano-enhanced PCM, nano-HTF) concerning the nanoparticles participation in the thermal energy storage system in a double tube heat exchanger was evaluated. Other effective factors, such as the inlet fluid temperature, different Reynolds numbers, fin as well as new parameter of pipe, and fin thickness were also evaluated. The results showed that the highest effect of different parameters on the PCM melting process was related to the 1% nano-HTF and 3% nano-enhanced PCM nanoparticles of SWCNT, which decreased the PCM melting rate by about 39%. The evaluation of the effect of pipe and fan thickness also showed that the melting rate improved by 31% through reducing the thickness of the HTF fin and pipe. In general, the current study followed two purposes first, to examine three methods of the dispersion of nanoparticles in the thermal energy storage system; second, to reduce the thickness of the tube and fin. Findings of the study yielded positive results.

Turbulent heat transfer enhancement in tubular heat exchangers with different twisted tape inserts

Experimental and numerical analyses are carried out to investigate the influence of twisted tape inserts on the heat transfer and the flow behavior in double tube heat exchangers. First, all the performance factors, namely the Nusselt number, friction factor, and thermal performance factor, were studied for a basic heat exchanger (BHE). Afterwards, twisted tapes with three different twist ratios (7.5, 6, and 4.5) were inserted inside the inner tube of the BHE, which resulted in three different modified heat exchangers (MHEs). For the numerical study, a 3D numerical model is developed with the k-ε RNG turbulent model to visualize the flow and the heat transfer behavior inside the heat exchangers. In both studies, turbulent flow field is maintained, ranging Reynolds number from 15000 to 50000. From the experimental result, an enhanced heat transfer, characterized by the performance factors, is found for all the MHEs compared to the BHE. The most enhanced thermal performance factor is achieved for the MHE with the lowest twist ratio. Finally, a good agreement between obtained numerical and experimental results reveals that the present numerical model can reliably predict the flow and heat transfer behavior in double tube heat exchangers.

Numerical analysis of turbulence-inducing elements with various geometries and utilization of hybrid nanoparticles in a double pipe heat exchanger

This paper aims to numerically investigate the effects of turbulence-inducing elements with various geometries in a double pipe Heat Exchanger (HEX). The water is considered as a working fluid and the flow is turbulent. Also, CFD simulation has been carried out by finite volume method within commercial software. In the first section, the various geometries, including smooth tube, corrugated tube, tube with spherical elements, and a tube with axial fins, are evaluated. Subsequently, the heat transfer characteristics of two various hybrid nanoparticles comprise Ag-MoS2 and Fe3O4-SiO2, are compared. Ultimately, the optimized geometry has been selected for adding hybrid nanoparticles of Ag-MoS2 to enhancing heat transfer performance. The obtain results indicate that the double tube heat exchanger with the spherical elements has the best thermal performance. In addition, with changing the Reynolds number from 4000 to 13,000 in the optimized model with Ag-MoS2 1%, the convective heat transfer coefficient enhances 62.21%.