Heat Transfer Method Research Articles

Critical Review of Corrugation in Tubular Heat Exchangers: Focus on Thermal and Economical Aspects

AbstractHeat exchangers (HXs) are crucial in transmitting thermal energy in various industrial and domestic applications. Efforts to improve the design of HXs over the years have resulted in heat transfer enhancement with the penalty of pressure loss (∆P). Researchers have implemented various methods to enhance heat transfer. These methods have been categorized based on the need for external power. Active heat transfer methods require external energy, whereas passive heat transfer methods operate without an external power source. Increasing the effective surface area for heat transfer or inducing turbulence through surface alterations can improve passive heat transfer, leading to secondary flow. Of all the surface alterations, the corrugated tubes are particularly significant for enhancing the heat transfer in a turbulent flow, as they result in a reasonable increase in ΔP. Apart from an increase in ΔP, the initial cost of corrugated tube HX is higher than that of simple HX. Therefore, one should not write off the economic analysis of any passive enhancement technique. Various applications increasingly use corrugation in systems like the primary and secondary heat transport systems of nuclear reactors, refrigeration, and other industries. This paper critically reviews thermal investigations for improving heat transfer and a comprehensive economic analysis of corrugated tube HXs.

Physics-informed graph neural network based on the finite volume method for steady incompressible laminar convective heat transfer

Physics-informed graph neural network based on the finite volume method for steady incompressible laminar convective heat transfer

Multi-direct forcing immersed boundary method for modelling heat and mass transfer of dynamic particles in three-dimensional fluid–solid systems

Multi-direct forcing immersed boundary method for modelling heat and mass transfer of dynamic particles in three-dimensional fluid–solid systems

Study on the Effect of Local Heating Devices on Human Thermal Comfort in Low-Temperature Built Environment

Localized heating systems are an effective approach to improve thermal comfort while reducing energy consumption in a cold indoor environment. Furthermore, localized heating devices have found widespread application in the hot-summer and cold-winter zones of China. This study investigates the heating characteristics of the local heating device in a low-temperature environment, as well as its effects on subjective perception and physiological responses, and develops a personalized control system for the device based on the experimental findings. We conducted experimental tests and questionnaires in a test room with air temperature set at 12 °C and 14 °C and a relative humidity of 55%. A total of six experimental conditions were designed using five types of heating equipment (heating wrist straps, heating insoles, heating leg straps, warm air blower, electric radiant heater), each employing different heat transfer methods. The results demonstrate that the head, hands, legs, and feet are susceptible to feeling cold in a low-temperature environment, and the use of a warm air blower and electric radiant heater can significantly enhance the thermal sensation of these parts, improve thermal acceptability, and raise local skin temperature. The electrocardiogram data indicate that heart rate variability can be utilized to assess thermal sensation in a cold environment with localized heating. Additionally, the relationship between thermal response and skin temperature was investigated, leading to the development of a control strategy for the local heating device in a low-temperature conditions.

Comparison Between Numerical and Experimental Methodologies for Total Enthalpy Determination in Scirocco PWT

Arc-jet facility tests are critical for replicating the extreme thermal conditions encountered during high-speed planetary entry, where the precise determination of flow enthalpy is essential. Despite its importance, a systematic comparison of methods for determining enthalpy in the Scirocco Plasma Wind Tunnel had not yet been conducted. This study evaluates three experimental techniques—the sonic throat method, the heat balance method, and the heat transfer method—under various operating conditions in the Scirocco facility, employing a nozzle C configuration (10° half-angle conical nozzle with a 90 cm exit diameter). These methods are compared with computational fluid dynamics (CFDs) simulations to address discrepancies between experimental and predicted enthalpy and heat flux values. Significant deviations between measured and simulated results prompted a reassessment of the numerical and experimental models. Initially, the Navier–Stokes model, which assumes chemically reacting, non-equilibrium flows and fully catalytic copper walls, underestimated the heat flux. By incorporating partial catalytic behavior for the copper probe surface, the CFD results showed better agreement with the experimental data, providing a more accurate representation of heat flux and flow enthalpy within the test environment.

Numerical Investigation of Nanofluid-based Flow Behavior and Convective Heat Transfer Using Helical Screw

Numerous industrial and home users have made use of heat transfer devices for the purpose of heat conversion and recovery. For the past half-century, engineers have worked tirelessly to perfect a heat exchanger design that cuts down on power use without sacrificing performance. Most methods of improving heat transfer work by either increasing the effective heat transfer surface area or creating turbulence, which results in lower thermal resistance. In this study, CFD was used to simulate Al2O3 and CuO nanoparticles in the adsorber tube of a parabolic solar collector with N=1 and N=2 turbulators at Re=20000, 60000, and 100000, respectively, and a turbulence strength of 5%. The turbulence strength was calculated as 5% of the total energy of the particles. Heat conduction is improved by the presence of nanoparticles in the base fluid. Therefore, nanofluids are candidates for alternative methods of heat transfer. Torsional turbulator models with N=2 have a greater output temp than those with N=1 because N=2 models have a higher practical heat level. The intake temp is raised from 35 to 46 degrees Celsius thanks to the presence of CuO nanoparticles in the two turbulator adsorber tubes that are close to one another. The Reynolds number invariably makes the Nusselt number higher. In addition, the Nusselt number demonstrates that there are a greater number of CuO nanoparticle models than Al2O3 nanoparticle models. In addition, CuO nanoparticles are more effective than Al2O3 at lowering pressure. When compared to the N=2 dual-turbulator mode, the N=1 single-turbulator mode has 34% more conflict. PECs are greater for models with two turbulators. Over a wide range of Reynolds numbers, the thermal PEC for N=2 models were 12 percentage points higher than that of N=1 models. CuO nanofluid receivers are superior to Al2O3 ones in their ability to convert solar energy into thermal energy. The two-turbulator model with a Reynolds number of 100,000 that uses CuO nanoparticles achieves the maximum thermal efficiency.

Types of Cooling Towers: A Review

Cooling towers are indispensable in dissipating heat from industrial processes and HVAC systems, hence playing a significant role in operational efficiency and sustainability. This review describes the classification of cooling towers based on airflow mechanisms, methods of heat transfer, and applications. This study highlights recent developments in hybrid cooling systems that combine wet and dry cooling technologies for improved water conservation and thermal efficiency. Through the analysis of recent developments in the domain, this work describes innovative design considerations that optimize thermal performances by including environmental concerns; designs that are in the counterflow and crossflow configuration. These insights underline continuous improvements within cooling tower technologies in light of evolving industrial and ecological demands.

Experimental study of pool boiling characteristics for non-azeotropic mixtures n-pentane / n-hexane on microstructure surfaces

Mixed alkanes are widely used as refrigerants in applications such as natural gas liquefaction, especially in the Floating Liquefied Natural Gas (FLNG) process. To elucidate the mechanisms underlying the weakening of phase transition in mixed refrigerants and to develop enhanced heat transfer methods, a pool boiling experimental setup is established in this study to investigate the boiling heat transfer characteristics of n-pentane/n-hexane mixtures on three different microstructure surfaces. By combining visual observation of bubble dynamics with analysis of the effects of composition conditions, micro-surface geometry, and wall heat flux conditions on the boiling heat transfer characteristics, it is revealed that the heat transfer coefficient (HTC) on the pyramid surface and the cylindrical surface, compared to the smooth surface, maximum increase by up to 345 % and 203 %, respectively. Compared with pure components, the mixture with a mass fraction of 0.5 n-pentane shows the greatest heat transfer deterioration. Microstructure surfaces significantly enhanced the HTC of the mixed refrigerants. Additionally, the microstructures activate more nucleation sites and higher bubble departure frequency. The guiding effect of the pyramid surface effectively decreases the possibility of bubble aggregation under high Eo and Ga numbers, thereby delaying the formation of mushroom bubbles. Therefore, the pyramid surface shows its advantages at different component ratios. The HTC correlations for pure and mixed refrigerants are developed. The predictions for pure and mixed refrigerants HTCs agree with most of the experimental data with a deviation of ±10 % and ±25 %, respectively.

Research on oil-water mixed-phase flow measurement method based on heat transfer method

Oil-water two-phase flow at oilfield wellheads is a common occurrence in distribution. This paper proposes using a heat transfer method to accurately measure and monitor the total fluid volume at the wellhead. To achieve this, thermal sensors of types PT1000 and PT20, which are suitable for measuring oil-water mixed flow, are first designed. The feasibility and linearity of the sensors are simulated and calculated. Secondly, the heat transfer coefficient is computed using experimental methods and a functional relationship between the heat transfer coefficient and the flow rate is derived. Finally, the calculated results demonstrate the feasibility of using the heat transfer method to measure oil-water two-phase flow. If the water-liquid ratio (WLR) is known, the flow rate can be calculated through the functional relationship between the heat transfer coefficient and the flow rate. This method can improve the accuracy of estimating the flow rate.

Modeling the interaction between powder particles and laser heat sources

This study investigates the spheroidization of titanium Ti-6Al-4V powder particles using numerical models developed in Abaqus and OpenFOAM. Spherical particles are crucial in powder-based additive manufacturing due to their superior flowability, packing density, and mechanical properties, enhancing printing precision and the quality of final products. While conventional techniques such as gas atomization and plasma spheroidization have been extensively researched, the potential of laser spheroidization remains underexplored. To address this gap, detailed numerical analyses of laser spheroidization were conducted, modeling heat transfer from the laser to powder particles using a transient uncoupled heat transfer method with latent heat considerations, while particle deformation was simulated with a phase-fraction-based interface-capturing approach integrated with Navier-Stokes equations. The results, validated against analytical models, indicate that particles within the 20–80 μm range experience optimal spheroidization within a 0.005-second residence time under laser heating, with particles smaller than 30 μm reaching evaporation temperatures of 5,000°C, while larger particles reshape without evaporating under a typical heat flux of 94 MW/m2 (1.8 kW laser power). This study demonstrates that laser spheroidization of Ti-6Al-4V powder can potentially increase powder yield by 10%, offering higher power density and shorter melting times compared to plasma spheroidization, thus presenting a more efficient alternative for achieving spherical particles of specific sizes.

Thermal model to investigate temperature distribution with a hollow notched K-wire for bone drilling

K-wire drilling is commonly used in orthopedic surgeries, generating significant heat that can lead to bone thermal osteonecrosis. To understand the heat propagation and thermal damage region, a mathematical model of the negative rake angle on the hollow notched K-wire was established. Subsequently, a theoretical model of the shear angle for this negative rake angle was proposed. Based on these models, a comprehensive theoretical model of the heat flux was derived. The accurate heat flux was determined using the theoretical values, and experimental temperature data through inverse heat transfer method (IHTM). This heat flux was then applied in a finite element analysis to simulate the heat transfer process and identify thermal damage regions under different drilling conditions. Results showed that the thermal damage region of bone with a solid K-wire, hollow notched K-wire without cooling, with air cooling, and with water cooling were approximately 6.4 mm, 3.2 mm, 2.6 mm, and 4.8 mm in width, respectively, and 6.79 mm, 6.45 mm, 6.39 mm, and 6.58 mm in depth, respectively. This study demonstrates that the hollow notched K-wire with air cooling is a potential solution to reduce the thermal damage region, thereby accelerating patient recovery.

Enhancing heat and mass transfer in MHD tetra hybrid nanofluid on solar collector plate through fractal operator analysis

Improved solar heat transfer methods are needed for the widespread use of solar energy. Due of their exceptional thermal characteristics, nanofluids have received a great deal of interest in this field. This research examines the use of tetra hybrid nanofluids in solar applications, with an emphasis on heat and mass transport properties. Due to their advantageous thermal characteristics, these nanofluids are well-suited for solar power production and other thermal applications. Accurate results for velocity, concentration, and temperature profiles are produced thanks to the model's use of fractal fractional derivatives and the Crank-Nicholson method for obtaining numerical solutions. In order to learn how different variables affect heat transport, parametric experiments are performed. The results show that tetra hybrid nanofluids greatly improve heat transfer performance over standard nanofluids. This improvement helps flat-plate solar collectors absorb more sunlight and increase their overall efficiency. The rate of mass transfer between phases may be quantified in the design and research of chemical reactors using the Sherwood number, an important quantity in chemical engineering. Its value is shown in a number of processes, including extraction, distillation, and catalytic reactions.

Thermal analysis of a reflection mirror by fluid and solid heat transfer method.

High-repetition-rate free-electron lasers impose stringent requirements on the thermal deformation of beamline optics. The Shanghai HIgh-repetition-rate XFEL aNd Extreme light facility (SHINE) experiences high average thermal power and demands wavefront preservation. To deeply study the thermal field of the first reflection mirror M1 at the FEL-II beamline of SHINE, thermal analysis under a photon energy of 400 eV was executed by fluid and solid heat transfer method. According to the thermal analysis results and the reference cooling water temperature of 30 °C, the temperature of the cooling water at the flow outlet is raised by 0.15 °C, and the wall temperature of the cooling tube increases by a maximum of 0.5 °C. The maximum temperature position of the footprint centerline in the meridian direction deviates away from the central position, and this asymmetrical temperature distribution will directly affect the thermal deformation of the mirror and indirectly affect the focus spot of the beam at the sample.

A fast quadrupole-based analytical model for solving transient heat transfer in ventilated double-skin walls and assessing their energy saving potential

This research proposes a fast and accurate method for modeling transient heat transfer in ventilated double-skin façades (VDFs) with forced ventilation to predict their energy-saving potential. Using the thermal quadrupole formalism, the method solves the VDF problem in the Laplace domain while considering the full transient nature of the heat transfer; the only approximation is in space. The solution involves obtaining a general transfer function that predicts heat transfer rates or air temperatures at ventilated cavity's exit. The quadrupole method is validated against computational fluid dynamic numerical simulations conducted under similar meteorological, design and boundary conditions. A very good agreement was found (less than 3 % average deviation) with a significant reduction in computation time (less than 3s against 6h for CFD calculations). The model is computationally efficient and can consider important factors such as the opacity of the walls, construction materials, and air cavity design parameters. Finally, the model allows the assessment of the energy-saving potential of VDFs under various scenarios compared to conventional systems, which helps contributing to more sustainable building design practices. The energy efficiency of a VDF configuration was compared against a conventional wall system. Energy savings of 8.4 and 5.2 % were obtained, in cold and hot climates respectively.

Numerical simulation and experimental study on guidance performance of hypersonic seeker under aerodynamic optical transmission effects.

When a hypersonic seeker flies at high speed within the atmosphere, intense interaction with the incoming flow gradually develops into a complex turbulent flow field. This interaction results in complex thermal responses at the seeker window, causing aerodynamic optical effects such as image shift, jitter, and blur of the target image, thereby restricting the seeker's detection capability and accuracy. This paper uses a numerical simulation model for the guidance performance of a hypersonic seeker under aerodynamic optical transmission effects. The study focuses on an ellipsoidal seeker, with its supersonic flight simulation on the basis of the Reynolds-Averaged Navier-Stokes (RANS) equations to get a non-uniform gradient flow field. The correctness of the flow filed results can be verified by wind tunnel experiments. The transient temperature field of the seeker is solved using an unsteady thermal conduction-radiation coupled fluid-solid heat transfer method. Finally, the guidance performance of the hypersonic seeker under aerodynamic optical effects is predicted using the ray tracing method, which employs wavefront aberration, point spread function, degraded images, and image shift.

Heat and mass transfer performance of multi-solute electroplating wastewater in spray evaporation separation process

Electroplating wastewater is complex in composition and contains many harmful substances. Based on the single droplet heat and mass transfer method, a one-dimensional mathematical model for the evaporation separation heat and mass transfer process of multi-solute electroplating wastewater is established. In order to validate the model, the experimental system of evaporation separation tower is established, and Nusselt numbers corresponding to metal ion solutions are fitted, reliabilities of models are also verified. The maximum relative errors of mathematical models are within 10.0 %. In addition, effects of the type and concentration of metal ions and air inlet temperature on heat and mass transfer characteristics of spray separation tower are investigated. Experimental results show that when the wastewater inlet concentration is the same, the improvement effects of increasing air inlet temperature on evaporation and separation performance from high to low are ZnCl2, CuCl2, and NiCl2 solutions. When the air inlet temperature increases from 90 °C to 130 °C, the evaporation speed of ZnCl2, CuCl2 and NiCl2 solutions increase by 90.3 %, 84.3 % and 45.7 %, respectively. When the air inlet temperature is the same, with the increase of wastewater inlet concentration, the evaporation separation performance of electroplating wastewater in descending order is ZnCl2, CuCl2, and NiCl2 solutions.

Progress in theory and simulations of lattice Boltzmann method for heat transfer enhancement on phase change

As a general phenomenon in science and engineering, phase change has appeared and been applied in many aspects. However, there is a sufficient necessity to enhance the heat transfer in the phase change process due to the low heat transfer efficiency of the phase change material. In order to improve the efficiency of heat transfer during the phase change process, theory and numerical simulations based on computational fluid dynamics, especially the lattice Boltzmann (LB) method, are reviewed. The LB method has become a strong numerical method for heat and mass transfer and fluid dynamics because of its mesoscopic nature and a series of unique merits brought by this nature. In this article, progress in theory and simulations of the LB method for heat transfer enhancement on phase change is reviewed. This review first introduces the basic theories and models of the LB method for flow field and temperature field. Afterward, the development of the LB models for tracing the phase interface is reviewed. The application of the LB method for phase change and investigations of the heat transfer enhancement in the phase change process are also discussed. Finally, future developments in the LB method for phase change problems are prospected.

A pseudo-density conjugate heat transfer method and its application to simulating the quasi-steady temperature field of a compressor cylinder

The substantial disparity in time scales between heat conduction and convection requires extremely tiny time steps in simulations, leading to significant computational demands when using current-tightly coupled methods to solve the temperature field of cylinders at the quasi-steady stage. A new pseudo-density method is proposed to accelerate the heat conduction rate. The influence of solid density on transient temperature under the periodic third-type boundary conditions is analyzed in a one-dimensional model by analytical methods and verified in a three-dimensional structure by numerical methods. It is found that reducing solid density can accelerate the heat conduction rate and increase the fluctuation amplitude of solid temperature. Therefore, a variable pseudo density is adopted for solids in the simulation of the transient heat transfer characteristics between the compressed gas and the cylinder. The results show that the pseudo-density method provides similar computational accuracy to the current tightly coupled methods, but at significantly lower computational cost. The fluctuation amplitude of the cylinder's temperature decreases rapidly in the wall thickness direction. The distribution of the convective heat transfer coefficient on the inner wall of the cylinder is extremely transient and highly non-uniform, which is consistent with the distribution of gas velocity near the cylinder wall.

Mechanistic impact of Stern bilayer-based electrolysis on the enhancement of pool boiling heat transfer

Pool boiling is a heat transfer method that utilizes phase change for efficient heat transfer, and enhancing its heat transfer intensity and understanding the mechanism is of great practical significance for refrigeration and microelectronics thermal management. This study employs experimental methods to innovatively use ionic surfactant modification on heating surfaces, building on the basis of strengthening heat transfer by generating hydrogen bubbles through water electrolysis to increase nucleation sites on the heating surface. The Stern double layer formed on the heating surface is utilized to control the growth rate and quantity of hydrogen bubbles, thus achieving controllable nucleation density on the heating surface. The study examines its impact on heat transfer efficiency and the onset of nucleate boiling (ONB). Results indicate that electrolysis can increase nucleation sites at low heat fluxes, thereby enhancing heat transfer. Using a CTAB solution at a concentration of 3200 ppm with an electrolytic current of 0.08A, under the Stern potential at saturated adsorption, the heat transfer coefficient increased by up to 3.16 times. Additionally, the superheat at ONB decreased from 12.6 K to 4.4 K under boiling heat flux. Therefore, utilizing electrolysis with the addition of surfactants to enhance rapid cooling of high-temperature surfaces provides a novel engineering application approach.

Study on freezing separation process through observing microstructure of NaCl solution ice

Freezing desalination is a method to purify saline water. Researchers believe that the salt inclusions distributed inside ice affect the sea ice salinity, but there is not sufficient visualized proof that has been obtained via direct and non-destructive experiments to support this view. Even less study has been carried out on the salt inclusion distribution inside ice below the eutectic temperature. In this paper, a NaCl solution ice sample was prepared with the original mass concentration of 3 wt% using unidirectional heat transfer method. The freezing temperature was −24 ℃, which is lower than −21.2 ℃, the eutectic temperature of NaCl solution. Micro-CT device was used to scan the upper, middle and lower parts of a 3 wt% NaCl solution ice sample and the 5-layer U-Net architecture in DL (deep learning) module of the Dragonfly program was used to segment images to extract the information of interest. The image characteristics of salt inclusions and air bubbles inside the ice were obtained. Very high salt inclusion area proportion was found in the surface layer images of the sample with the maximum area proportion of about 43%. Experiments were also carried out to measure the salinity distribution inside the same solution ice samples. It was found that in the surface and bottom ice layers, the salinity is higher than that of the original solution. In the experiments, for the layers cut from the top and bottom of the 3 wt% NaCl solution ice sample, each of them possesses 10% of the solution ice sample mass, their salinities were 4.28 wt% and 5.41 wt%, respectively. Comparing the measurement results with the micro-CT image processing results, it was found that the variation tendency of the area proportion of salt inclusions is consistent with that of the ice layer salinity. The combination of micro-CT technology with DL image processing method has been proved an effective way to visualize and analyze quantitatively the internal structure of salt solution ice. Then, three NaCl solution samples that have the original mass concentrations of 3 wt%, 6 wt% and 9 wt%, and a pure water sample were frozen under the same conditions. The middle parts of the four ice samples were scanned and the obtained micro-CT images were processed. It can be found that in the middle parts of the three NaCl solution ice samples, the area proportions of salt inclusions increase from top to bottom and are positively correlated with the original salinities of the solution ice. The factors affecting air bubble distribution are more complex than that affecting salt inclusion distribution.