Heat Transfer In Exchanger Research Articles

Analyzing the effectiveness of heat transfer in a horizontal geothermal heat exchanger using numerical methods

Analyzing the effectiveness of heat transfer in a horizontal geothermal heat exchanger using numerical methods

Temperature-dependent matching of heat transfer and catalysis in cryogenic heat exchangers with ortho-para hydrogen continuous conversion

Temperature-dependent matching of heat transfer and catalysis in cryogenic heat exchangers with ortho-para hydrogen continuous conversion

Heat Transfer in Double Pipe Heat Exchangers with Small Tube Spacing

Abstract In this current work, the heat transfer in double pipe heat exchangers with small tube spacing is analysed. This type of heat transfer is generally described in many literary sources, however, in laminar flow, the resulting values of the theoretical equations differ. Moreover, the small spacing of the pipes can affect the fluid flow and subsequent heat transfer. The suitability of using available theoretical methods for the design of double pipe heat exchangers (the Stephan, VDI and Baehr methods) was evaluated. A series of experiments was carried out on a double pipe heat exchanger with a tube spacing of 1.4 mm. The experimentally determined value of the heat transfer coefficient was up to two times higher in comparison with the values calculated according to theoretical methods. The relative increase was more significant for the lower Reynolds number values. At the same time, the difference of the wall temperature along the circumference of the outer tube was detected. This phenomenon was theoretically analysed and can be explained by tube misalignment in the small tube spacing. The procedure of quantification of this effect was proposed. This effect may cause an inhomogeneity of the media flow and temperature distribution and, as a result, increase the performance of the heat exchanger by tens of percent.

Investigating the Effect of Heat Transfer Influenced by the Application of Wavy Corrugated Twisted Tape Inserts in Double Pipe Heat Exchangers

This study investigates the heat transfer and friction factor characteristics in a heat exchanger utilizing copper wavy (corrugated) twisted tape inserts. By inducing turbulent flow within the inner tube of the heat exchanger, these inserts generated increased turbulence, thereby enhancing heat transfer and causing a rise in pressure drop. The copper twisted tapes, with various twist ratios (TR=10.7, 8.5, 7.1), measured 1 meter in length and 14 mm in width. The heat exchanger's outer tube was made of mild steel, with an outer diameter of 0.0198 m and an inner diameter of 0.0142 m, while the inner tube was constructed of copper, with an outer diameter of 0.038 m and an inner diameter of 0.032 m. The overall length of the pipe-in-pipe heat exchanger was 1.4 m. Bulk mean temperatures were recorded at different positions for various water flow rates, and new correlations for the Nusselt number and friction factor were derived from the results for the twisted tape inserts. The Reynolds number ranged from 5000 to 17000. Comparative analyses revealed that the wavy twisted tape with a twist ratio of 7.1 provided the highest heat transfer rate, showing a 172% increase in the Nusselt number and a 32.11% increase in the friction factor relative to a smooth tube.

Entropy generation and thermal behavior of microchannel fitted with punched curved vortex generators

Utilizing curved vortex generators (VGs) has emerged as a promising way to improve heat transfer in heat exchangers. However, research on the placement of punched rectangular curved winglet VGs on two opposing heat transfer surfaces of microchannel heat exchangers is limited. Through experiments and simulations, the effects of five perforation positions and three pitches on fluid flow and heat transfer were examined. This analysis is performed in the turbulent flow regime (2500 < Re < 3500) and the governing equations are solved by using SST k-ω model, assuming that the fluid is incompressible, has constant thermal properties, and ignores the effects of thermal radiation and gravity. Metrics such as the Nusselt number ratio, friction coefficient ratio, secondary flow intensity, thermal enhancement factor, and entropy generation are used to analyze the flow dynamics of mixed vortices. The results indicate that different perforation positions significantly affect the vortex characteristics, altering heat transfer and pressure loss. Furthermore, the pitch of the VGs plays a crucial role in governing heat transfer and frictional losses. Specifically, the heat transfer rate increased by 12.1 % to 61.1 % compared to empty tubes, accompanied by a rise in pressure loss ranging from 50.6 % to 115.1 %. To validate the findings, the principle of entropy generation was utilized. Notably, under conditions of a Re of 2500, a perforation position proximal to the VG's leading edge (θ = +12°), and a pitch of 15 mm, a remarkable thermal enhancement factor of 1.29 was achieved.

Optimization of Turbulent Flow Heat Transfer in a 3D Cubic Shell Heat Exchanger using Non-Mixture Multiphase Nanofluids

The present work investigates the turbulent flow heat transfer in a three-dimensional cubic shell and tube heat exchanger employing non-mixture multiphase nanofluid, specifically SiO₂-H₂O. Computational Fluid Dynamics (CFD) simulations were carried out to study the variation of both shell and tube inlet velocities and optimize the thermal performance of the exchanger. The Reynolds-averaged Navier-Stokes (RANS) solver and the k-epsilon turbulent model were employed, and the results were validated against experimental data and numerical results from the available literature. Key results showed that reducing the tube’s Reynolds number to 75% of the shell’s inlet velocity yields the highest total heat transfer rate of 26,692 Watt, marking an impressive 54% improvement over the baseline conditions. Lowering the tube inlet velocity improved the fluid residence time leading to enhanced heat absorption and higher performance. However, reductions in either fluid Reynolds number below 75% led to diminished heat transfer rates, attributed to reduced turbulent kinetic energy and less effective thermal mixing. These findings provide valuable insights into the role of nanofluids in boosting heat transfer efficiency, offering practical implications for industries seeking to enhance energy conservation and optimize thermal systems such as air conditioning and heating systems, thermal power plants, automotive and aerospace industries, as well as solar thermal power plants.

Performance Analysis of Corrugated Twisted Tape Inserts for Heat Transfer Augmentation

This study explores the impact of wavy corrugated twisted tape inserts on enhancing heat transfer and reducing pressure drop in a double pipe heat exchanger. Cu inserts with twist ratios of 3.2, 4.2, and 5.2 were used to create turbulence in the inner tube. Varying water flow rates and measuring bulk mean temperatures at different points revealed significant improvements in heat transfer over smooth tubes. The insert with a 3.2 twist ratio achieved the highest Nusselt number increase (185%) and a 36.33% rise in the friction factor. These results highlight the effectiveness of wavy corrugated twisted tape inserts for optimizing heat transfer, with a 3.2 twist ratio identified as the most effective. Across Reynolds numbers from 4000 to 18000, Nusselt number increases were 77.75% for a 5.2 twist ratio, 167% for a 4.2 twist ratio, and 185% for a 3.2 twist ratio. Friction factors rose by approximately 10.42% for a 5.2 twist ratio, 32.54% for a 4.2 twist ratio, and 36.33% for a 3.2 twist ratio, demonstrating the relationship between twist ratio, heat transfer enhancement.

Investigation of the insoluble impurities' impact on flow boiling heat transfer in aluminum microchannel heat exchangers

Microchannel flat-tube heat exchangers are known for their high heat transfer efficiency and compact size. In practical applications, the predominantly adverse influence of insoluble impurities on the condensation process necessitates further exploration into the underlying mechanisms affecting the flow boiling process. The effect of common insoluble impurities on the flow boiling of R410A refrigerant in a microchannel flat-tube heat exchanger has been investigated, and variation of the impurity volume fraction on heat transfer, mass transfer, pressure drop, and bubble formation are analyzed. Additionally, an adaptive modification method for the mass transfer factor is proposed. The numerical model of flow boiling heat transfer in a microchannel is validated through experimental data and empirical correlations. Thermo-hydraulic performance evaluation incorporates efficiency index and area goodness ratio metrics. Results reveal that the presence of insoluble impurities complicates the boiling heat transfer mechanism by influencing bubble evolution and multiphase flow patterns. Air impurities at a volume fraction not exceeding 5% prove beneficial for enhancing flow boiling efficiency in microchannels; however, a 38.5% decrease in efficiency index is observed with 1% oil impurities present. Optimal thermo-hydraulic performance is achieved with approximately 2%–3% water impurities.

Predicting Heat Transfer Enhancement with Twisted Tape Inserts Using Fuzzy Logic Techniques in Heat Exchangers

Fuzzy logic, introduced by Lotfi Zadeh in 1965, is a powerful method for modelling complex experiments. This study utilizes fuzzy logic to simulate and predict heat transfer in a double-pipe heat exchanger equipped with wavy inserts. The inserts, in the form of twisted tapes, have varying twist ratios (TR=9, 7, 6). The study investigates a range of Reynolds numbers (Re) from 6000 to 18000, with friction factors ranging from 0.03620 to 0.08231, and Nusselt numbers (Nu) between 66.13 and 253.28. The results for different twist ratios are compared to the ideal case. The experimental results indicate that the highest heat transfer occurs with a twist ratio of 6, leading to a significant increase of 162% in the Nusselt number and a 36.21% rise in the friction factor compared to the ideal scenario. In the fuzzy logic framework, the input variables are the twist ratio (Tr), temperature, and Reynolds number (Re), while the output variables are the friction factor (f) and Nusselt number (Nu). The study demonstrates that the Mamdani fuzzy inference system is an exceptionally effective tool for predicting experimental outcomes, given its low error rate. Upon analysing the data, it is observed that the graphs plotting the Nusselt number versus Reynolds number and friction factor versus Reynolds number, derived from both experimental data and the fuzzy logic model, exhibit nearly identical trends with a margin of error of just 3%. This high level of accuracy underscores the reliability of the fuzzy logic model in replicating the experimental results.

Design optimization of shell and tube type heat exchanger of G.A Siwabessy multi-purpose reactor cooling system

G.A Siwabessy multi-purpose reactor is a nuclear reactor that utilizes a controlled fission reaction (a chain reaction of atomic fission). The heat exchanger in the reactor cooling system plays a vital role in transfering heat from the primary coolant side to the secondary coolant side. Heat transfer coefficient (U) and heat transfer area (Ao) are two variables that have a huge influence on the success of heat transfer in a heat exchanger. The aim of this research is to compare the U and A values in two different ways, namely the full factorial method and the use of Heat Transfer Research Inc. (HTRI) software. The novelty of this research is the use of two different methods to check the U and A0 values of heat exchangers in nuclear reactors. In the calculation using the full factorial method, 4 independent variables with 3 levels were made, so 81 calculations were obtained. The most optimal calculation results are then validated with HTRI software. From the calculation results, it is known that the largest overall heat transfer coefficient (U) is 6531.60 W/m2 °C with a heat transfer area (Ao) of 584.47 m2 . The results of the validation with the HTRI software obtained an overall heat transfer coefficient (U) of 5045.10 W/m2 °C with a heat transfer area (Ao) of 574.19 m2 . There is a difference in value between the results of manual calculations and the results of the validations of the HTRI software which is made possible by a decrease in the performance of the heat exchanger.

Unveiling the underlying physics of two-phase boiling heat transfer enhancement through shearing of coalescing bubbles

The upcoming energy scarcity problem has driven research toward developing energy-efficient two-phase heat exchangers essential for various cooling applications. This research is rooted in the principles of pool boiling, essential for effective heat transfer in various heat exchangers. A well-known reported problem in heat exchangers is the dry-out phenomena of heated surfaces due to bubble coalescence. To tackle this undesirable problem, an innovative technique has been introduced in this study, which involves the shearing of bubbles through liquid jet impingement over the heated surface. The study has been carried out in a two-dimensional domain numerically, in the wall superheat range of 9–16 K. To study the underlying physics involved in this pool boiling phenomenon, the bubble dynamics parameters such as departure frequency, bubble diameter, cold spot (bubble base) temperature, and vapor volume fraction have been analyzed. The results show that with the jet shearing effect, a maximum enhancement of 25% in heat transfer rate is observed at higher wall superheat. The investigation also highlights that the liquid jet enhances vapor volume fraction, indicating enhanced steam generation, particularly an enhancement of 27% observed at elevated wall superheat. An early onset necking effect is also observed with the shearing effect, which leads to the formation of smaller bubbles with higher departure frequencies. This study is a benchmark to the fundamental physics of enhancing two-phase heat transfer through bubble shearing, offering promising insights for energy conservation in two-phase heat exchanger design, particularly within the context of pool boiling.

Impacts of Adding Porous Media and Phase Change Material on Performance of Solar Water Distiller System Under Iraq Climatic Condition: An Experimental Study

ABSTRACTThis current investigation involves an experimental inspection of adding porous medium and phase change material (PCM) above the absorber surface to enhance the performance of a single slope and single basin solar water distiller system. To demonstrate the effectiveness of adding porous medium and PCM, the performance of the modified system and conventional system is compared under similar operating conditions. The system that uses porous medium and PCM is called MSS‐FPP, whereas the conventional system is called MSS‐F. Rectangular fins are fixed above the absorber plate for both models. For MSS‐FPP model, three different types of porous medium (stones, nuts, and black glass balls) are used in addition to paraffin wax filled inside circular tubes as a PCM. The data are collected in November and December 2023 in Mosul City, Iraq. The experiments are carried out under different water depths. The findings confirm that the performance of MSS‐FPP model is better than MSS‐F model by 41.32% (for water depth 3 cm) and 30.61% (for water depth 5 cm). The results also indicated that the water productivity of MSS‐FPP model is higher than MSS‐F model by 41.67% (for water depth 3 cm) and 30.65% (for water depth 5 cm). For MSS‐FPP model, the maximum water productivity and efficiency are obtained when using black glass balls as compared to nuts and stones types, where the highest water temperature and water productivity values are found equal 54°C and 1.01 kg/m2 for water depth 3 cm. The enhancement in the performance of modified solar water distiller system (MSS‐FPP) shows that using a porous medium and PCM has considerable impacts on the evaporation rate, heat exchange, and rate of heat transfer.

Entropy optimization in ternary hybrid nanofluid flow over a convectively heated bidirectional stretching sheet with Lorentz forces and viscous dissipation: A Cattaneo–Christov heat flux model

Bidirectional stretching sheet models can represent surfaces in heat exchangers where fluids flow under continuous deformation. Ternary hybrid nanofluids could be employed in these systems to increase heat transfer rates between fluids in heat exchangers and improve the efficiency of energy conversion processes. In this work, we explore the novel application of a ternary hybrid nanofluid (water with titanium dioxide, cobalt ferrite, and magnesium oxide nanoparticles) for enhanced heat transfer in heat exchangers modeled by a bidirectional stretching sheet. This approach offers a potential advancement over traditional nanofluids (with one or two nanoparticles). Furthermore, we present a comprehensive analysis that incorporates ohmic heating, Cattaneo–Christov heat flux, thermal radiation, viscous dissipation, and irreversibility. The governing equations are transformed into a system of nonlinear ordinary differential equations using appropriate similarity transformations and then solved using the bvp4c solver, a MATLAB built-in function. This study's findings reveal that the Eckert number and radiation parameter increase fluid temperature, while the thermal relaxation parameter leads to a reduction in the temperature of the fluid. It is detected that an increase in magnetic field parameter and volume fraction of [Formula: see text] results in a decline of the skin friction factors in both directions. It is revealed that there is a reduction in the Nusselt number with the rise in Eckert number ([Formula: see text]), and the same number declines at a rate of 0.8252 when [Formula: see text]. It is noticed that the skin friction coefficient declines at a rate of 0.62179204 (in case of x-direction) and 0.621791816 (in case of y-direction), respectively, when the values of magnetic field parameter lie between 0 and 3.5. Furthermore, it is noticed that an upsurge in thermal relaxation parameter results in a fall in the temperature of the fluid.

Numerical study on the influence of flow direction and fluid type on heat transfer and pressure drop in a two-tube spiral heat exchanger with innovative conical turbulators

In this research, numerical analysis will be conducted on the thermal and hydraulic performance of a spiral two-tube heat exchanger. The study employs an innovative turbulator design with curved outer blades and a semi-conical section with two openings. Numerical simulations were conducted using the commercialized Finite Volume Method (FVM) program, ANSYS FLUENT 18.2. The finite volume method was employed to analyze thermal and fluid equations and parameters. A comparison was made between two distinct flow directions, namely positive and negative currents, utilizing a comprehensive range of three working fluids. The numerical findings indicate that employing counter-current flow with a Water/MOS2−Fe3O4 fluid nanohybrid results in superior endothermic performance. These results indicate that a maximum thermal efficiency improvement of roughly 17.54 % and 8 % can be achieved by using the counterflow configuration with the nanohybrid fluid Water/MOS2−Fe3O4 at a mass flow rate of m˙ = 0.008 kg/s, in comparison to alternative models. Furthermore, the results showed that the Water/MOS2−Fe3O4 fluid nanohybrid performs better than the Ag-HEG/Water nanohybrid fluid when used in counterflow and parallel flow configurations, starting at a Reynolds number of 600. With a counterflow configuration in the two tubes, the Water/MOS2−Fe3O4fluid nanohybrid achieves the highest thermal performance coefficient in the two-tube heat exchanger.

Comparative Study of Heat Transfer and Flow Friction in Plate Heat Exchangers with CarboxyMethyl Cellulose and Sodium Alginate

Abstract: Study of Plate heat exchanger (PHE) with power law fluid is a very interesting topic now a days as there is improvement of thermal performance of heat exchanger. Power law fluids show complex flow behavior due to its rheological properties. The parameters which differ these power law fluids from Newtonian fluids are rheological properties like flow behavior index and power law index. Hence flow behavior index and power law index are the two parameters which affect the heat transfer rate. Now to enhance rate of heat transfer we should know how Nusselt number changes with change in flow behavior index and power law index. Hence the aim of present study was to observe how Nusselt number and friction factor changes with change in flow behavior index and power law index. For this purpose thermal performance of PHE have been studied with CorboxyMethyl Cellulose (CMC) and sodium alginate as a cold fluids. Comparison of Nusselt number and friction factor of CMC and sodium alginate have been done. It was observed that Nusselt number for CMC solution was more compared to sodium alginate solution with less friction factor than sodium alginate.

Thermal energy transfer for green urban development: numerical investigation on the heat transfer and flow noise in heat exchangers with different helical and segmental baffles

Thermal energy transfer for green urban development: numerical investigation on the heat transfer and flow noise in heat exchangers with different helical and segmental baffles

Experimental Analysis on Using Nanoparticles to Improve Heat Transfer in Compact Heat Exchangers

Compact heat exchangers are now essential parts of many industrial processes that aim to reduce their environmental impact and increase energy efficiency. The experimental inquiry presented in this paper aims to improve the performance of heat transfer in compact heat exchangers by adding nanoparticles to the fluid used for heat transfer.A range of experiments were carried out with different nanoparticle concentrations, flow rates, and temperatures to evaluate the effects of nanofluids.To explore the effects on heat transfer enhancement, a variety of nanoparticle materials, including graphene oxide, copper oxide, titanium dioxide, zinc oxide, and aluminum oxide, were dispersed in the base fluids. According to experimental data, adding nanofluids significantly improved heat transfer performance; these nanofluids demonstrated greater heat transfer coefficients than conventional heat transfer fluids.

A Review of Thermochemical Energy Storage Systems for District Heating in the UK

Thermochemical energy storage (TCES) presents a promising method for energy storage due to its high storage density and capacity for long-term storage. A combination of TCES and district heating networks exhibits an appealing alternative to natural gas boilers, particularly through the utilisation of industrial waste heat to achieve the UK government’s target of Net Zero by 2050. The most pivotal aspects of TCES design are the selected materials, reactor configuration, and heat transfer efficiency. Among the array of potential reactors, the fluidised bed emerges as a novel solution due to its ability to bypass traditional design limitations; the fluidised nature of these reactors provides high heat transfer coefficients, improved mixing and uniformity, and greater fluid-particle contact. This research endeavours to assess the enhancement of thermochemical fluidised bed systems through material characterisation and development techniques, alongside the optimisation of heat transfer. The analysis underscores the appeal of calcium and magnesium hydroxides for TCES, particularly when providing a buffer between medium-grade waste heat supply and district heat demand. Enhancement techniques such as doping and nanomaterial/composite coating are also explored, which are found to improve agglomeration, flowability, and operating conditions of the hydroxide systems. Furthermore, the optimisation of heat transfer prompted an evaluation of heat exchanger configurations and heat transfer fluids. Helical coil heat exchangers are predominantly favoured over alternative configurations, while various heat transfer fluids are considered advantageous depending on TCES material selection. In particular, water and synthetic liquids are compared according to their thermal efficiencies and performances at elevated operating temperatures.

Prediction of heat exchanger efficiency using laminar heat transfer in swirling flow of radiated graphene oxide with nano fluid additives using machine learning technique

Nanotechnology has recently led to new possibilities for enhancing heat transfer in heat exchangers. The remarkable thermal characteristics of graphene oxide (GO)-based nanofluids with nanoscale additions have garnered significant attention in particular. When nanofluids and intricate flow patterns are involved, traditional analytical models frequently fail to appropriately forecast the efficiency of heat exchangers. Analyzed the phenomenon of laminar heat transfer in a heat exchanger that has a swirling flow of fluid dynamics, and pressure drop, and predicted the condensation heat transfer coefficient (HTC) of LHT. The functionalized radiated GO was chosen as nanomaterials in the present for the Pre-processing of Data Methods for managing outliers by machine learning (ML) models, like the CLAHE algorithm. The logarithmic mean temperature difference (LMTD) can be used to determine the temperature driving power for heat transfer within a heat exchanger. The Dynamic Smagorinsky Model (DSLM) and Wall-Adapting Local Eddy-viscosity (WALE) Model are turbulence models primarily designed for capturing turbulent behavior in fluid flows. The Kern technique and Hagen–Poiseuille equation are used for the pressure drop and pumping power needed in a shell and tube in laminar flow through a microtube based on Levenberg–Marquardt and Momentum Algorithm to predict Nusselt number and pressure drop in heat exchangers. The prediction sensitivity of the HTC by an LHT-trained ML model is used to evaluate the performance. The ML methods may be effectively used to forecast and maximize heat exchanger performance in the setting of laminar heat transfer in radiated GO nanofluid swirling flows. The accuracy score of 99%, demonstrating its exceptional predictive capabilities and results has great potential to improve energy efficiency, save operating costs, and advance sustainable practices in various industrial applications.

Numerical Analysis and Design for Thermal Efficiency Optimization using Al2O3 Nanofluids in Shell and Tube Heat Exchangers

In this study, the efficacy of aluminum oxide (Al2O3) nanofluids at a 2% concentration for enhancing heat transfer in shell and tube heat exchangers is evaluated. By employing SOLIDWORKS for the innovative design and Computational Fluid Dynamics (CFD) for simulation, an improvement in heat transfer efficiency over traditional hot water systems is identified. Emphasizing the unique properties of Al2O3 nanofluids in augmenting heat transfer rates, the role of advanced CAD and simulation tools in engineering practices is highlighted. Results confirm nanofluids' benefits in improving thermal management systems, indicating their potential to decrease energy consumption and operational costs. Furthermore, the exploration of a novel design for heat exchangers, inspired by but distinct from existing market standards, suggests new avenues for the application of nanofluids in various industrial settings, marking a step towards more energy-efficient technologies.