Double Exchanger Research Articles

Convective-radiative thermal investigation of a porous dovetail fin using spectral collocation method

An inverted or reversed trapezoidal profiled fin (dovetail fin) is a fin with an irregular cross-sectional area that is used for improved performance in double pipe heat exchanger applications. The current investigation focuses on the temperature distribution in an internal heat-generating longitudinal dovetail porous fin. A second-order ordinary differential equation (ODE) governs the heat transfer problem of a dovetail fin, and dimensionless terms are used to reduce it to a non-dimensional form. The resulting ODE is solved numerically using the spectral collocation method (SCM) via a local linearization strategy, and the temperature distribution in the dovetail profiled fin is discretized using Chebyshev-Gauss-Lobatto (CGL) collocation points and Chebyshev polynomials. The effect of various thermal parameters on the non-dimensional temperature profile and fin efficiency is graphically depicted for a fin with both convective and insulated tip conditions. As a result, for higher values of the convective-conductive and porosity parameter, the temperature in the dovetail fin distributes in a declining manner.

Influence of non-uniform magnetic field on the thermal efficiency hydrodynamic characteristics of nanofluid in double pipe heat exchanger

Enhancement of the heat transfer rate inside the double pipe heat exchangers is significant for industrial applications. In present work, the usage of non-uniform magnetic field on the heat transfer rate of the nanofluid flow streamed inside double pipe heat exchangers are comprehensively studied. Computational technique of CFD is used for the visualization of the nanofluid hydrodynamic in existence of the magnetic source. Influences of the magnetic intensity and nanofluid velocity on the heat transfer are also presented. Simple algorithm is used for the modeling of the incompressible nanofluid flow with addition of magnetic source. Presented results show that magnetic source intensifies the formation of the circulation in the gap of the inner tube and consequently, heat transfer is enhanced in our domain. Comparison of different geometries of tube reveals that the triangle tube is more efficient for improvement of the heat transfer of nanofluid flow. Our results indicate that heat transfer in the tube with triangular shape is more than other configurations and its performance is 15% more than smooth tube.

Experimental evaluation of heat transfer performance of double vertical coils and shell heat exchanger with altered inlet configuration under low-frequency ultrasound

The heat transfer and pressure drop of the water flow were investigated inside double vertical coils and a shell heat exchanger by altering the configuration of the inlet flow channel using two or four inlet ports under 28 kHz ultrasound. The inlet flow on the shell side was set at Reynolds numbers of 200, 400, or 600. The effects were examined of the altered position of activated ultrasonic transducers at P1–P9. The results showed that the Nusselt number on the shell side was enhanced by 11.6 % by modifying the inlet flow configuration from two to four channels. In addition, the heat transfer capability was boosted by approximately 9 % when the ultrasonic waves were irradiated into the heat exchanger. The relationship between effectiveness and the number of transfer units under ultrasound irradiation was also presented and discussed to simplify heat exchanger analysis. It showed that the waves enhanced the heat transfer capacity of the heat exchanger by up to 5.7 %. By altering the inlet configuration, the pressure drop on the shell side was reduced by 36.8–39.1 %, while ultrasonic waves only affected the pressure drop by less than 1 %. Using a performance evaluation criterion indicator, the performance of the ultrasonic heat exchangers could be improved by a maximum of 1.065 and 1.089 for two and four inlet ports, respectively. Additionally, the thermal efficiency of using ultrasound was evaluated, indicating that the ultrasonic effects resulted in a higher heat exchange performance than the supplied wave energy.

Investigations of protracted finned double pipe heat exchanger system for waste heat recovery from diesel engine exhaust

The need for energy and material savings, as well as environmental concerns, have helped to increase the demand for high efficiency heat exchangers in the modern era. In practice, a heat exchanger or the direct ejection of the hot working fluid is used to recover the waste heat from a heat engine or thermal power plant into the environment. Waste heat of a heat engine or power plant is recovered to the environment via a heat exchanger or by direct ejection from the hot working fluid. In many situations, waste heat recovery removes or greatly reduces the necessity for additional fuel energy input to achieve this goal. The double pipe heat exchanger equipment is taken in this research, heat from engine exhaust recovers due to its superior qualities. The design characteristics of the heat pipe will be changed in order to increase overall efficiency by studying the concepts of various authors. Different design parameters for a double pipe heat exchange system as well as different working fluid-flow rates are tested with the suggested device. Additionally, ANSYS performs CFD for the proposed heat exchanger system in order for the results to support the experimental findings.

Shell-side flow study and structural optimization of a double helical-like flow heat exchanger

A double helical-like flow heat exchanger model was built, its shell-side flow state was studied by the CFD method, and the difference in heat transfer performance between it and the torsional flow heat exchanger was compared. From the numer?ical simulation results, it is found that the heat transfer coefficient and pressure drop are improved by 7.07-8.93% and 15.50-18.22%, respectively at the same flow rate, and the comprehensive performance expressed as Nu/f 1/3 is improved by 21.84-24.08%. Using the orthogonal test method to optimize the shell-side struc?ture, it is found that the comprehensive performance is influenced by the two factors of spacing/groups and angle of baffles, and the influence of the deflection angle of two adjacent groups of baffles is very small, and the optimal structural combi-nation of comprehensive performance is 30-0-70/11 (the angle of baffles is 30?, the deflection angle of two adjacent groups of baffles is 0?, the spacing between two adjacent sets of baffles is 70 mm, and the number of baffle groups is 11). The reliability and feasibility of the simulation method were verified by experiments.

Hybrid CFD-ANN approach for evaluation of bio-inspired dolphins dorsal fin turbulators of heat exchanger in turbulent flow

The central aim of the present investigation is to evaluate the effects of bio-inspired Dolphin’s dorsal fin turbulators (DFTs) with a hybrid CFD-ANN approach in a counter flow double pipe heat exchanger. The DFT’s physical model is adapted from the infrared thermal image of a bottlenose dolphin dorsal fin. The effects of different influential parameters, such as the length scale (D) of DFTs including 4, 8, 12 mm and the number of turbulators (N) including 6, 10, and 14 are numerically examined at different Reynolds numbers. Also, using CFD data, the neural network is trained with great accuracy of R2 above 0.999. Important parameters such as Nu, f, Ɛ, NTU can be predicted in different conditions by the ANN method. This method greatly reduces the costs of CFD solutions, which is advantageous. The results indicate that the DFT's streamlined geometry could significantly reduce friction loss by streamlining the fluid flow. Also, colliding the fluid stream with the DFTs improves heat transfer by boundary layer destruction. The UA Ratio (UAR) of the Dolphin’s dorsal fin turbulator heat exchanger (DFTHE) to the simple heat exchanger (SHE) is between 1.02 and 1.74. Also, the ratio of Nu, Ɛ, NTU for the DFTHE to the SHE is equal to 2.48, 1.63, and 1.74, respectively.

Advanced solutions to improve heat recovery from wastewater in a double heat exchanger

Reducing energy consumption and CO2 footprint in existing buildings without requiring extensive construction work is one of the biggest challenges facing the globe today. Although heating contributes for the majority of energy use in buildings, residential hot water demand is also relatively high, particularly when daily usage is high and especially for certain applications. The use of technologies that recover energy from sources other than fossil fuels to heat water has grown crucial, and one such technology involves recovering thermal energy from wastewater. Typically, heat recovery from wastewater is made to collect any remaining energy from the hot drainage water, and this energy is then applied to heat pumps or to warm up incoming cold water. The paper presents numerical simulations using a SST k-ω turbulence model in order to compare a regular geometry of heat exchanger with a helicoidal one. The second one provides a more turbulent flow that allows an intensification of the outer flow, thus allowing the enhancement of the heat transfer from the inner heated flow to the outer flow.

REVVING UP HEAT-TRANSFER PERFORMANCE OF DOUBLE PIPE HEAT EXCHANGER USING DIVERSE MOLAR Ag-GO HYBRID NANOFLUIDS: AN EMPIRICAL AND NUMERICAL STUDY USING CENTRAL COMPOSITE DESIGN

This study seamlessly integrates empirical and numerical approaches to enhance the efficiency of a double pipe heat exchanger (DPHX) using varied molar concentrations (0.03, 0.06, and 0.09 M) of Ag-doped GO hybrid nanofluids as the working fluids within the heat exchanger's annulus. Remarkable improvements in the heat exchanger's performance were achieved by increasing the molar concentration of Ag-GO hybrid nanoparticles, along with the Reynolds number (ranging from 250 to 1451) and the mass flow rate (ranging from 8 to 47 g/s) of the hybrid nanofluids. The utilization of a 0.09M Ag-GO hybrid nanofluid at a Reynolds number of 1451 and a flow rate of 47 g/s resulted in outstanding enhancements in heat-transfer coefficient (62.9%), and Nusselt number (33.55%) surpassing the base fluid. The empirical results of Nusselt number and heat-transfer coefficient were optimized and analyzed using the central composite design approach (CCD) with response surface method, incorporating the Graetz number, varied molar concentrations of Ag-GO, and thermal conductivity of the hybrid nanofluids as input factors. The optimized second-order polynomial quadratic equation model demonstrated excellent compatibility and optimal performance of the heat exchanger, supported by variance analysis. Additionally, CCD optimization confirmed a notable desirability function (0.99) and emphasized the significant influence of the input factors on the output responses. In conclusion, the Graetz number exhibited prominent influence among the input factors, alongside the molar concentration and thermal conductivity of hybrid nanofluids, effectively enhancing the performance of the DPHX.

Study on the simplified model of vertical double U-pipe ground heat exchanger

A simplified semi-analytical model of vertical double U-pipe ground heat exchanger was established. The validity of the established model is examined by contrasting the figured outcomes with experiment data, emulation results of 3-D numerical model and calculation results of infinite line-source model for different inlet boundary conditions and configurations. After one hour, the semi-analytical model?s relative error is less than 0.32% under the boundary condition of given inlet fluid temperature. Under the boundary condition of given total heat input rate, the semi-analytical model?s relative error after ten hours is less than 0.11%, while the infinite line-source model?s relative error is less than 0.60%. The semi-analytical model is in good agreement with experiment and numerical model, and has higher calculation accuracy than infinite line-source model.

Experimental and numerical analysis for the size, charging and discharging characteristics of a phase changing material as a thermal energy storage

Phase Change Materials (PCMs) can be utilised for thermal energy storage to close the gap between energy supply and demand, as the main drawback in solar thermal collectors is the absence of heat gain during night hours. The charging and discharging period of the PCM in the water storage needs to be examined and evaluated. One of the main difficulties to apply PCM in a solar thermal system is to identify its optimum size and observe its phase changing process. Therefore, numerical investigations were performed to identify the size of the PCM needed to accomplish a high performance system, which is done using the ANSYS FLUENT. In the present work the charging and discharging mechanism were covered and analysed numerically and experimentally. Moreover, several investigations were done to assess the PCMs characteristics and effect in the solar thermal application, which is by focusing on its selection, implementation technique and thermal conductivity. Numerical analyses were conducted via ANSYS Fluent and validated with experimental work. The most suitable PCM for the operating condition of a domestic solar thermal application was found to be paraffin wax. The optimum selection of the PCM was reached via CES Granta software and a constructed selection criterion. The implementation of the PCM in the solar thermal application was accomplished using the storage tank as a double pipe heat exchanger. Through the experimental analysis, the thermal conductivity enhancement is done by adding aluminium foam to the PCM, which indicates a significant effect on the performance of the charging and discharging period of the PCM. Numerical investigations were done on the material interface between the PCM and the water to observe its effect on the thermal conductivity. The material interface did not exhibit any significance on the thermal conductivity of the PCM. The optimum size of the PCM was attained using ANSYS fluent.

ANFIS based effectiveness and number of transfer units predictions of MWCNT/water nanofluids flow in a double pipe U-bend heat exchanger

In this study, the heat transfer coefficient, Nusselt number, effectiveness and number of transfer units of water mixed multi-walled carbon nanotubes nanofluids passes through a tube-in-tube heat exchanger was experimentally investigated. Investigations were performed in the operating conditions of Reynolds number ranging from 3500 to 12000 and volume concentrations ranging from 0% to 0.3%, respectively. The obtained four parameters were predicted using adaptive neuro fuzzy inference system (ANFIS). The Reynolds number and particle volume loadings are the input data in artificial neural network analysis and heat transfer coefficient, Nusselt number, effectiveness and number of transfer units is output or target. The Nusselt number, heat transfer coefficient, effectiveness, and number of transfer units was enhanced to 31.3%, 44.17%, 2.51% and 2.76% at φ = 0.3% and at a Re of 10005, against base fluid. Implementation of ANFIS with various quantities of neurons in the mid layer provides 1–10−6 with the correlation coefficient (R2) of 0.9978, and 0.9998 and root mean square error of 0.0018581, and 0.0014159 for heat transfer coefficient and Nusselt number, respectively. The above developed structure has been successful in predicting 96% of variation in all the parameters.

Experimental and Numerical Investigation of the Effect of Rotational Flow on Heat Transfer in a Concentric Double Pipe Heat Exchanger

Experimental and Numerical Investigation of the Effect of Rotational Flow on Heat Transfer in a Concentric Double Pipe Heat Exchanger

Thermal performance analysis of a double pipe heat exchanger using biosynthesised silicon carbide and carbon nanotubes

ABSTRACT A nanofluid is a solution of nanoparticles with diameters fewer than 100 nanometers suspended in a base fluid such as water, ethylene glycol, or oil. In the nanofluid, these nanoparticles are suspended. The goal of this research is to look at the functioning of a twin-pipe heat exchanger that uses counter flow arrangements and two different nanofluids as cooling fluids. Alkaline water is a basic fluid made up of silicon carbide (SiC) and carbon nanotubes (CNT). The goal of this research was to see how different compositions of SiC and CNT nanoparticles dispersed in water affected the heat transfer capacities of a twin pipe heat exchanger developed with a counterflow arrangement. The flow rate of the nanofluid and the particle volume concentration of alkaline water were (0.02) and (0.04), respectively. Fluids with constant intake temperatures of 60°C for water and 30°C for nanofluid flow at the same input velocity via a heat exchanger. Both fluids are traveling at the same rate. According to the findings, nanofluid absorbs more heat than water at a range of flow speeds. Because of the improved thermal properties of nanoscale fluids, this results in increased thermal efficiency in heat exchangers.

Applications of distributed fiber Bragg gratings to the measurements of in-tube fluid temperature distribution

The temperature distribution information of the two-phase fluid inside a tube can effectively reflect the heat transfer of the fluid, which is the key information in the study of the heat transfer of flowing fluid in a tube. This article aims to develop a method for measuring the temperature distribution of fluid inside a tube based on distributed fiber Bragg gratings (DFBGs). It is more convenient than traditional measurement methods using thermocouples that are impossible to be installed to the inner tube of a double tube heat exchanger. By using a stainless steel seamless tube, ϕ1.0 × 0.2 mm in size, and a hose to seal and protect the optical fiber with Bragg grating sensors inside, we successfully shielding the stress effects from the thermal effects, and also enhance the durability of the fiber. Since the seal leads to extra thermal resistance to the DFBGs, obtaining the response performance of the sealed DFBGs to a temperature change is essential for reliable applications. The performance characterization shows that the temperature measurement repeatability of the sealed DFBGs is within 0.2 °C for a period up to 35 months. The time constants of the DFBGs are not longer than 0.25 s, capable of measuring the temperature oscillations with frequency less than 2 Hz. Comparison with commercial thermocouples supports the feasibility and the reliability that the sealed DFBGs can be used as temperature sensors. To obtain the equivalent thermal conductivity between the tube that sealed the fiber and the fiber, κ¯air, the response to a temperature jump was also calculated based on a simplified model, which can comprehensively reflect the heat transfer of the air inside the sealed tube and provide the reference for design optimization of a sealed FBG for dynamic measurements. Finally, the capillary tube with sealed DFBGs was placed in the condenser tube of a two-phase circulation loop to exhibit the feasibility of the steady and dynamic temperature distribution measurements of the fluid inside a tube.

Correlations on heat transfer rate and friction factor of a rectangular toothed v-cut twisted tape exhibiting the combined effects of primary and secondary vortex flows

It is generally recognized that the heat transfer rate can be improved using active, passive and compound methods. The use of twisted tape inserts in a pipe flow is one of the passive methods. The influence of swirl flow, primary and secondary vortex flow generated due to twist in tape, v-cut on the tape, and the teeth on the v-cut respectively on Nu (heat transfer rate), f (friction factor), and CPE (criterion for performance evaluation) of an inserted toothed v-cut twisted tape is investigated in this study. Experiments were carried out on a double pipe heat exchanger using water as the working medium for a Reynolds number range of 6000–13,000, with the uncertainty analysis of the relevant parameters taken into account. The correlations for Nu and f in terms of factors such as Re (Reynolds number), Pr (Prandtl number), b/c (ratio of depth of v-cut to width of cut), and e/c (ratio of depth of teeth on v-cut to depth of v-cut) are also developed using regression analysis. The results of correlations lie within ±10% for Nu whereas within ±15% for f. The investigations show that the inclusion of teeth on the v-cut develops a secondary vortex flow which further enhances the Nu (though not up to the comparable magnitudes of the primary vortex) and is capable of minimizing the percent decrement of heat transfer rate with increasing depth of cut at higher Re. The friction factor increased up to 7.7 times for e/c ratio equals 0.14 (depth of the tooth to depth of the v-cut) in comparison to the plain tube, while the increase in heat transfer rate for the same was 84% for Re = 6000.

Dynamic viscosity analysis of hybrid nanofluid MWCNT- Al2O3/engine oil using statistical models with evaluating its performance in a double tube heat exchanger

Dynamic viscosity analysis of hybrid nanofluid MWCNT- Al2O3/engine oil using statistical models with evaluating its performance in a double tube heat exchanger

Predicting the thermal performance of double pipe heat exchanger using the generalized regression neural network model

A heat transfer device in which heat exchange takes place between two fluids at different temperatures. The performance of any heat exchanger is evaluated by its heat transfer rate. Such heat transfer rate directly depends on the difference in temperature between two fluids and the mass flow rate. In this study, an attempt has been made to predict the rate of heat transfer between two fluids and the exit temperature using the generalized regression neural network (GRNN) model. For this, two GRNN models are designed using 15 real-time experimental datasets among which the GRNN-1 model is effectively designed to predict the exit temperature of both the hot and the cold fluids flowing through the heat exchanger with an accuracy of 97.48%. Similarly, the GRNN-2 model is designed to predict the rate of heat transfer between the fluids with an accuracy of 94.04%.

Investigations on tube in tube metal foam heat exchanger

The heat transfer equipments with higher heat transfer ability are needed in several industrial applications. With conventional methods, size of the device increases and it becomes bulky. With the use of metal foam, it is possible to attain large ratios of surface to volume. Therefore, using metal foam in heat exchanging devices is crucial. The main reason behind the use of metal foam over conventional method is its weight-saving and impact-absorbing structures. Insertion of metal foam in heat exchangers for various applications can lead to greater effectiveness and heat transfer enhancement. It has been observed that very few researchers have participated in the area of double tube heat exchangers (DTHE) having annular spaces filled with metal foam. The present work deals with numerical and CFD analysis of double tube heat exchanger (DTHE) with metal foam having different pore densities differing from 10 PPI to 50 PPI & performance evaluation of the same by taking hot water stream and cold water stream as working fluids. The modelling was created in Creo & simulation was done with k-omega (2 equation) viscous model in Ansys fluent flow. In the present work, double tube heat exchanger was considered in counter flow mode with inner sided tube (Stainless Steel) ID 9.5 mm & OD 12.7 mm and outer sided tube (Galvanized Iron) ID 28 mm & OD 33.8 mm. For fully developed turbulent flow, total length was considered as 1.5 m. The water streams through inner tube and annular space were flowing at uniform and constant flow rates of 2 lpm and 10 lpm respectively. Hot water and cold water inlet temperatures were taken at 800c & 300c respectively. For the analysis nickel metal foam with 10 PPI to 50 PPI with 0.9 porosity was inserted in the annular spaces of DTHE. For different pore densities comparative analysis was done. It was found that with rise in pore density of metal foam heat transfer rate (HTC) and pressure drop increased for both numerical & mathematical results. CFD simulation results were in good agreement with results obtained from empirical correlations taken from literature.

Mathematical and Experimental Analysis of an Internally Finned Double Pipe Heat Exchanger for Coupling of Solid Oxide Fuel Cell Cathode Exhaust Heat and Vapor Absorption Refrigeration System on Refrigerated Trucks

Abstract Solid oxide fuel cells (SOFCs) generate electricity with high quality waste heat which if harnessed and used as energy source for vapor absorption refrigeration systems (VARS) will address the emission issues related to refrigerated transport infrastructure. The temperature range of the heat source required at the desorber of the VARS is between 120 °C and 200 °C, while SOFCs cathode exhaust heat temperatures are 600 °C and above. Therefore, an internally finned double pipe heat exchanger (DPHX) was used in this study with thermal oil as the coupling fluid to experimentally couple the SOFC cathode exhaust heat with the VARS indirectly. The experimental setup mimics a 5 kWe SOFC stack. Results showed that 1.84 kW of heat was recovered at a cathode exhaust flowrate of 24.64 L s−1 resulting in a heat exchanger effectiveness of 12.22% and overall heat transfer coefficient of 60.15 W m−2 K−1. The recovered 1.84 kW of heat are able to power a single effect VARS on board a small, refrigerated truck to supply 1 kW of cooling load. Results also revealed an exchanger effectiveness and overall heat transfer coefficient increase by 70.2% and 19.4%, respectively, at a reduced exhaust flowrate of 7.347 L s−1. Further improvement of 81.1% and 39.22%, respectively, of exchanger effectiveness and overall heat transfer coefficient was achieved at 4.653 L s−1 exhaust flowrate.

Experimental study on heat transfer augmentation in a double pipe heat exchanger utilizing jet vortex flow

AbstractThis paper examines experimentally the effect of jet vortex technology on enhancing the heat transfer rate within a double pipe heat exchanger by supplying the heat exchanger with water at different vortex strengths. A vortex generator with special inclined holes with different inlet angles was designed, manufactured, and integrated within the heat exchanger. In this study, four levels of Reynolds number for hot water in the annulus (Reh) were used, namely, 10,000; 14,500; 18,030; and 19,600. Similarly, four levels of Reynolds number for cold water in the inner tube (Rec) were used, namely, 12,000; 17,500; 22,500; and 29,000. As for the inlet flow angle (θ), four different levels were selected, namely, 0°, 30°, 45°, and 60°. The temperature along the heat exchanger was measured utilizing 34 thermocouples installed along the heat exchanger. It was found that increasing the inlet flow angle (θ) and/or the Reynolds number results in an increase in the local Nusselt number, the overall heat transfer coefficient, and the ratio of friction factor. It is revealed that the percentage increase in the average Nusselt number due to swirl flow compared to axial flow was 10%, 40%, and 82% for an inlet flow angle of 30°, 45°, and 60°, respectively.