Finned Tube Research Articles

Numerical study of the effect of a thin wire on the thermohydraulic performance in a plate fin-and-tube heat exchanger

A numerical study on the effect of a wire on the thermohydraulic performance in a plate-and-tube heat exchanger is performed with the Reynolds Averaged Navier-Stokes Equations approach. The heat exchanger is represented by a small finned tube bank with the implementation of periodic boundary conditions and symmetry conditions. The simulation models the turbulence with the Shear-Stress Transport model (SST k-ω). A benchmark case (without thin wire) is validated with PIV measurements of the horseshoe vortex and semi-empirical correlations for heat transfer. Then, twenty-four simulations are conducted at different dimensionless distances (1.0, 1.2, and 1.4) and angles (0, 15, 30, and 45°) of a thin wire. Predictions show that vortical structures around the thin wire contribute to an increase in thermohydraulic performance if the recirculation zones caused by thin wire do not affect the airflow patterns generated by finned tubes. However, the thermohydraulic performance decreases if airflow patterns are affected by the thin wire. Therefore, thin wire located at a dimensionless distance of 1.2 and angle of 15° generates a 5–6 % profit on the thermohydraulic performance with a pressure drop up to 73 Pa for Re = 2100.

Improvement of heating and cooling performance for thermoelectric devices in medical storage application

Thermoelectric devices provide several advantages over typical refrigeration systems, including compact size, quiet operation, minimal energy use, and environmentally friendly. By harnessing these benefits, we have developed a blood storage system that has the potential to transform the way blood products are preserved and safeguarded. Thermal performance was evaluated using a variety of scenarios, including thermal fin material and emissivity, voltage operation, heat sink type (I, U, O type), and tube load. This research used thermoelectric devices, Styrofoam materials, thermal fin and the heatsink to design the thermoelectric storage cabinet with heat insulation function. The aims to improve the performance of thermoelectric devices by optimizing the thermal fin design during heating/cooling storage mechanisms. Our findings emphasize the importance of thermal radiation, particularly in circumstances with low natural convection and high surface emissivity. Thermal performance is optimized when heating storage elements are incorporated into aluminum finned tubes and run at an input voltage of 8V in a 25 °C ambient temperature. In addition, using U-shaped cooling fins in cooling conditions results in superior cooling performance. The outcomes of this study highlight the possibility and potential benefits of using thermoelectric devices to heat and cool medical storage, notably blood storage applications. The insights gained here contribute to advancing the efficiency and sustainability of medical storage systems, ultimately benefiting healthcare and the environment.

Experimental correlation for external forced convection in non-standardized finned tubes perpendicular to the flow

Experimental correlation for external forced convection in non-standardized finned tubes perpendicular to the flow

Development of multi-module arranged in series using U-type longitudinal fin tube in thermal energy storage system

The performance of a thermal energy storage (TES) system for commercial applications can be improved using phase change materials (PCM). This study develops a vertical multi-module from a PCM for a TES system that achieves the same effect as a single-module by arranging multiple-modules in series as a U-type longitudinal fin tube to enhance the system's performance. The U-type longitudinal fin tube is designed to enhance heat transfer within the module, and a single-module is designed for multi-module applications. The TES system is analyzed to the average heat transfer rate, overall heat transfer coefficient, quantity of heat storage/release, and utilization ratio at different heat transfer fluid (HTF) flow rates, inlet and outlet temperatures and different number of modules. Consequently, the addition of several modules improves the thermal performance, and an increase in the HTF flow rate improves the average heat transfer rate. The overall heat transfer coefficient is used to analyze the thermal characteristics of the PCM. During the heat charging and discharging processes, the average heat transfer rates are 2.4 and 2.55 kW, respectively, and the quantities of heat storage and release are 5,153.59 and 4,771.79 kJ, respectively, for three modules. The overall heat transfer coefficient of the PCM exhibits similar results with an increasing HTF flow rate; it increases marginally from 42.25 to 45.8 and 9.9–10.8 W∙m−2∙K−1 as more modules are added. Further, the results of this study confirm that the relatively low HTF flow rates in the multi-module require the addition of several modules and that increasing the HTF flow rates limits the number of modules.

Optimization-Inspired Pin-Fin Array for Supercritical Carbon Dioxide Recuperator

Additively manufactured heat exchangers are one possible route to cost-effective sCO2 power cycles. In this paper, experimental results are obtained for two helical pin fin tubes that were designed following parametric optimization of the fin array. Neither the numerical optimization nor the experimental testing have been previously reported in the literature. The two tube designs were, (1) the optimization inspired design, and (2) the optimization-inspired design with a fin diameter increased by a factor of 2. To characterize the print, the designs were scanned using X-ray computed tomography to measure feature sizes and heat transfer area. The optimization was conducted in a commercial, computational fluid dynamics code. The code solved the Reynolds Averaged Navier-Stokes (RANS) and energy equations with turbulence closure provided by the shear stress transport (SST) k-ω model. In the experiments, the Nusselt number augmentation was measured using the Wilson plot technique and the friction factor was determined with mass flow and pressure drop measurements. The experimental testing indicated that the optimization-inspired design had a friction factor that was four times less than the baseline tube design at equal Nusselt number. Additionally, the optimization-inspired design had a 14% improvement in Nusselt number, at equal friction factor, relative to the best performing computational fluid dynamics (CFD) trial points. Tube design (2), with the larger diameter pin fins, had similar performance, within experimental error, as the tube with the smaller diameter pin fins (1). Both tubes achieved overall fin array efficiencies near 1. A performance factor, V/V0, equal to the volume of the enhanced heat exchanger divided by the volume of the baseline (no-fins) heat exchanger, is recommended to quantify internal cooling performance. The experimental shell and tube heat exchanger, using the additively manufactured tube, is competitive with printed circuit heat exchangers in its pressure drop class and could be further improved by optimizing a shell-and-tube heat exchanger utilizing this heat transfer enhancement feature.

Performance comparison of inline and staggered integrally-molded spiral finned tubes for low-carbon emissions

The combined flue gas cooler with integrally-molded spiral finned (IMSF) tubes, which combines in-line and staggered tube bundles to leverage the performance advantages of different arrangement modes, has been proposed in this paper to simultaneously achieve heat transfer enhancement, ash deposition prevention, and wear resistance. The comprehensive performance including thermal–hydraulic, ash deposition, and wear performance of in-line and staggered IMSF tubes has not been reported and has been investigated with a multi-field coupled numerical model in this paper. Results show that for inline tubes, increasing the transverse pitch (PT) can reduce ash deposition and wear with slightly decrease in the thermal–hydraulic performance and increasing the longitudinal pitch (PL) can improve the thermal–hydraulic performance, with a significant increase in ash deposition when PL reaches to120mm, while for staggered tubes, decreasing the PT can enhance the thermal–hydraulic performance and reduce wear, with a sharp deterioration in ash deposition when the PT reaches 80 mm, and increasing the PL can decrease wear and has a minor impact on the thermal–hydraulic and ash deposition performance. Also, in the design of combined flue gas coolers, inline tubes should be placed at the front and two rows of dummy tubes placed before the inline tubes, and a larger PT and a moderate PL should be adopted to effectively reduces the overall tubes' wear and ash deposition; staggered tubes should be placed at the rear with an appropriate PT and a larger PL, enabling the full utilization of their excellent thermal–hydraulic performance while avoiding severe wear. This work can provide theoretical guidance and reference for the design and optimization of combined flue gas coolers to promote low-carbon emissions.

SRANS Simulation on a Helical-Segmented Finned Tube Bank

A numerical simulation on a six-row helical-segmented finned tube in a staggered layout is performed with the Reynolds Averaged Navier-Stokes (RANS) approach. The turbulence effect is represented with the k-ε RNG model, and a fixed temperature in each tube row considers the inside fluid temperature. The tube bank is represented by a small finned tube bank and a single interacted module. The small finned tube bank considers symmetry conditions on the sides of the computational domain. The single interacted module considers periodic boundary conditions for velocity, pressure, and temperature. Both simulations are compared to develop the basis of complex simulations such as repetitive finned tube modules. Average values on parallel planes to the streamwise direction for velocities, pressures, and temperatures are compared in both simulations. The comparative analyses show deviations lower than 11% for the velocity field, 12% for the pressure field, and 10% single for the temperature field. Therefore, results show an appropriate flow representation with periodic boundary conditions.

Performance analysis and effect of various material fin-perforations in a plate-finned heat exchanger

Finding increasingly efficient heat exchangers requires a critical task: the development of fin profiles for prolonged life of equipment. The present study uses numerical analysis for better plate-finned heat exchangers hydraulic and thermal performance. Fin patterns are used in the analysis to evaluate a four-tube in-line heat exchanger. The proposed approach involves use of simulation and numerical methods to solve the heat transfer problem on different materials and wind velocity data as boundary conditions for improved heat transfer. The Reynolds-Averaged Navier-Stokes (RANS) model will be used to correct the average turbulent air flow over finned tubes in three dimensions using the ANSYS-Fluent software. The evaluation plan compares the current findings with published Nusselt number empirical correlations for the justification. Finally, the presentation of a parametric study on the impact of fin perforation size and shape on different materials and the behaviour of fluid dynamics and heat transfer. Larger fin perforation sizes (circular, rectangle, rhombus, and ellipse shapes) are found to enhance the heat exchangers' overall PEC and thermal efficiency for sustainability of the thermal equipment. The comparison was made between non-perforated and perforated fin types. Ultimately, it was determined that the best option for plate fin heat exchangers is the circular type perforated fin. When compared to without perforated fins, the circular type perforated fin has a higher heat transfer coefficient. A circular perforated fin has high performance, and the rhombus type perforated fin has lower performance.

CFD analysis for absorber tube of a solar water heater collector

In this work, CFD analysis of smooth absorber fin tube and screw absorber fin tube used in solar water heater collector is considered and compared. Three-dimensional numerical CFD model simulations were performed using flow simulation in COMSOL Multiphysics software. A flat absorber wing tube made of different materials (Stainless steel, Iron, Copper, Aluminum) is evaluated. At the same time, different water inlet velocities were tested. Various velocities such as 0.01 m/s, 0.02 m/s, 0.025 m/s, 0.035 m/s have been simulated and here the inlet velocity of 0.2 m/s is close to optimal for the given size, the outlet velocity at this velocity is suitable for direct consumption.

Fast dynamic analysis of damaged 1D periodic waveguides

We extend the Bloch wave-based reduced order models in the Wave Finite Element Method (WFEM) framework for fast wave-damage interaction analysis. It aims at fault detection and diagnosis of periodic structures. A finned tube heat exchanger, which can be seen as a 1D system, is used as a numerical application. Reduced model results and performance are compared to a standard WFEM model. Diffusion curves are obtained more than a hundred times faster with the proposed scheme, moving toward massive generation of wave-damage scenarios and indicators to perform damage detection.

Entropy generation and thermodynamic analysis of pool boiling heat transfer on doubly enhanced tubes

To improve the efficiency of the heat exchanger tube, one smooth tube and four doubly enhanced tubes (EX1, EX2, EX3 and EX4) have been investigated for the pool boiling heat transfer experiments in this paper. The indicate that the pool boiling heat transfer coefficient of the doubly enhanced tubes increased visibly with the augmentation of heat flux through the bubble behavior. Heat transfer reinforcement effect of the doubly enhanced tubes are significantly better than that of the smooth tube. Additionally, pool boiling heat transfer coefficient can be further enhanced by raising the saturate temperature. Entropy generation minimization analysis demonstrates that the heat transfer characteristics of like T-shaped tubes (EX1 and EX2) are superior to that of low fin tubes (EX3 and EX4). Particularly, tube EX1 exhibits higher pool boiling heat transfer efficiency. It is observed that a reasonable fin pitch is more advantageous for improving heat transfer characteristics. The utilization of entropy generation minimization analysis provides theoretical support for the design and optimization of doubly enhanced tubes.

Computational Analysis of Pulsating Pipe Flow for Heat and Flow Characteristics Enhancement

To increase the performance of the thermal and flow devices with respect to the heat and flow characteristics in a pipe, different techniques are widely used such as modification in the fluid flow and modifications in the pipe geometries. Several boosting modified tubes, including a finned tube, a tube with ribs, a tube with spirally roughened walls, a corrugated tube, a fluted tube, a helical tube, an elliptical axis tube, and others, act to increase the turbulence in fluid flow and are the examples of modifications in the geometries. As compared to the modification in the pipe geometries with modification in the fluid flow, the fluid flow modifications attract more cost and most are the techniques are not so economical. In the current paper, the comparative analysis is studied between the simple pipe and pipe with dimples for heat and flow characteristics enhancements with the help of computational techniques. For pipe with dimples, the results were more satisfying as compared with the simple pipe. The maximum velocity build-up in the dimple pipe was 0.753m/s whereas in the simple pipe it was 0.604m/s, , that means there is a 24.66% increase in velocity in dimple pipe as compared with simple pipe. Also, vorticity was found to be more in the dimple pipe and which was 126000/s as compared with simple pipe 389/s , which means more than 100% increase in the vorticity. Heat transfer enhancement in the dimple pipe was observed in terms of an increase in the temperature and found to be a maximum of 418 K as compared with simple pipe only 409 K,which means that there is a 17.60% increase in the temperature in the dimple pipe. The computational study concludes that there were enhancements in the heat and flow characteristics of fluid flow in the dimple pipe as compared with the simple pipe.

Demonstration of long-term cyclic sorption of ammonia in modified expanded graphite-calcium chloride composites for practical applications

The long-term viability of the ammonia‑calcium chloride (NH3−CaCl2) pair in commercial adsorption refrigeration systems faces challenges due to the disintegration of calcium chloride (CaCl2) during multiple ammonia sorption cycles. To address this issue, we conducted a comprehensive study, starting from lab-scale investigations to experiments with full-scale commercial refrigeration systems. We prepared three calcium chloride–expanded graphite (CaCl2:EG/4:1) composite samples (labelled B1, B2, and B3) with varying water content (20–45% by weight), and also used a conventional CaCl2-activated carbon-white cement composite (CaCl2:AC:WC/16:4:1, sample A). The composites were coated over fin tubes wrapped around with wire mesh for this purpose. These composites were tested for structural integrity over 300 continuous cycles in a customized constant-volume single fin-tube adsorption/desorption bed. While all samples initially exhibited similar sorption capacity ∆χof≈0.6−0.7kgNH3/kgCaCl2, sample A experienced a significant deterioration of approximately 60% in capacity within 300 cycles due to agglomeration and volumetric expansion. In contrast, the EG-based samples demonstrated remarkable stability, with B3 maintaining ∆χ≈0.57kgNH3/kgCaCl2 even after 800 cycles. We applied B3 in a 2 TR adsorption refrigerator that uses biomass as fuel to demonstrate <15% cooling power attenuation even after prolonged operation over 800 cycles in practical scenarios. We believe these engineering interventions are necessary to encourage the broader adoption of ammonia-based adsorption refrigeration systems, which are a sustainable choice due to their zero global warming and ozone depletion potentials.

Adsorbent beds packed in triply periodic minimal surface-derived structures and their performance in adsorption desalination/cooling systems

The present study aims at improving the performance of adsorption desalination/cooling systems (ADCs) by packing the adsorbent materials inside triply periodic minimal surface (TPMS) structures. In that respect, solid and sheet types of metallic networks-based TPMS (e.g., Gyroid and Diamond) were addressed to improve the performance of ADCs. Using CFD simulations, the TPMS structures were compared to the finned tube-packed adsorbers based on specific daily water production (SDWP) and specific cooling power (SCP). The computational model was developed and hence verified using the most relevant literature. The influence of heat transfer area, effective thermal conductivity, effective diffusivity, and tortuosity on SDWP and SCP was investigated for the TPMS-derived and finned tube structures. Those structures were also examined using variant porosity levels. The results indicated that increasing TPMS porosity resulted in lower SDWP and SCP; however, TPMS still attained an improvement in SDWP and SCP compared to finned tube adsorbers. At a porosity of 0.8, SDWP of 10.4 m3/ton was attained by the sheet network of Diamond, which was 19.4% superior to that of the finned tube structure. At a porosity of 0.2, the sheet network of Diamond attained SDWP and SCP of 20.1 m3/ton and 627.4 W/kg, respectively.

Flow-Thermal-Strength Analysis of the Finned Tube Heat Exchanger Operation

Ensuring the safety and adequate service life of thermal power equipment, in addition to the need to maintain the required operating parameters, are among the most important issues related to the heat exchanger operation. This also applies to heat exchangers with extended surfaces, which are usually achieved by finned tubes. They are typically used where heat is exchanged between working fluids characterized by quite different properties, such as gas-water or air-coolant fluids. The high parameters of these fluids (temperature, pressure), occasionally their aggressiveness, and often the salts they contain, causing fouling of surfaces, can be the cause of failures. Among the most common are tube failures, which can lead to severe consequences. The developed methodology of coupled flow-thermal and strength analysis was used in exemplary calculations for a two-pass, two-row combustion gas - water heat exchanger with finned elliptical tubes. The reason for choosing such a design, was the fact of having failure data for two similar designs. This allowed verification of the correct operation of the developed methodology and redesign the heat exchanger manifold to ensure better flow distribution in a tubular space and better stress distribution.

Numerical investigations on thermal-hydraulic characteristics of finned tube heat exchangers considering thermal contact resistance

To elucidate the impacts of thermal contact resistance (TCR) on the finned tube heat exchanger, a method of equivalent heat conductivity was employed to model the TCR. Comparative analysis of the thermal-hydraulic characteristics of different finned tube banks was conducted. The comprehensive performance criterion considering the impacts of thermal contact resistance was developed based on the application scenario. Without accounting for the TCR, the thermal-hydraulic performance of high frequency resistance welded spiral finned tube (HWSFT) bank is almost same as that of integral spiral finned tube (ISFT) bank. The H-type finned tube (HFT) bank has 10.9% smaller comprehensive performance criterion, 10.3% lower heat transfer area performance and 19.0% higher compactness than the ISFT bank. The fin efficiency reduces significantly for a larger TCR. With considering the TCR, the HWSFT bank and HFT bank have 38.0% and 54.3% smaller comprehensive performance criterion, 37.9% and 53.7% lower heat transfer area performance, 32.6% and 36.8% lower compactness than the ISFT bank, respectively. The ISFT has great improvement of comprehensive performance compared with welded finned tubes due to the elimination of TCR.

Experimental and numerical studies on capture of SO3 aerosols from flue gas using finned tube condenser with vortex generators

A heterogeneous condensation device of finned tube condenser equipped with vortex generators has been proposed for capturing SO3 aerosols and moisture from saturated flue gas. An original numerical model for simulating the growth and capture behavior of SO3 aerosols was proposed and verified. The simulation results show that the mean diameter and capture efficiency all increase gradually along the mainstream direction. The VGs can induce a large number of low-velocity recirculation zones on the fin surface, thereby promoting the agglomeration and deposition of SO3 aerosols. The experimental results show that the maximum number and mass capture efficiencies reached 81.1% and 40.1% respectively at SO3 concentration of 30 mg/m3. Besides, the rear end of the condenser has the smallest condensate volume and the lowest condensate pH value, which makes this part more susceptible to corrosion. Moreover, the effects of main parameters were also explored to provide references for engineering applications.

OPTIMALIZATION OF INTEGRAL FIN TUBE IN OUTSIDE CONDENSATION BASED ON FLOODING ANGLE

Increasing heat transfer in condensation for low surface tension fluid is dominated by using extended area (fin). One of the extended area on pipe is integral fin tube. Designing of integral fin tube should be conducted due to generate optimal condition such as designing fin spacing. Fin spacing has significantly impacted to heat transfer enhancement. Whereas the material of pipe is copper since has higher heat conductivity than others and fluid working is methanol. To predict optimal geometry of integral fin tube is conducted by using mathematical simulation by dividing area into flooded and unflooded. The active area or unflooded area represents the heat transfer area adn enhancement. In this experiment is found that the optimum fin spasing is 1 mm

Hydraulic Expansion Joint Contact State of Heat Exchanger Based on New Contact Area Measurement Method

The contact state of a seamless internal threaded copper tube and an aluminium foil fin not only affects the heat transfer efficiency of a tube–fin heat exchanger but also seriously affects its service life. In this study, hydraulic expansion technology was used to connect the copper tube with an internal thread with a 7 mm diameter to the fin of the heat exchanger. The influence of the expansion pressure and pressure holding time on the contact state was analysed through experiments and finite element simulation, and the variation law of the two on the contact state was obtained. The contact state was characterised by the contact gap and contact area. In order to obtain the specific contact area value, a new method of measuring the contact area was developed to reveal the variation in contact area between the copper tube and the fin after expansion. The results show that the contact gap decreases with an increase in expansion pressure, while the pressure holding time remains the same. The contact area increases with an increase in expansion pressure, and the rate of increase slows. When the expansion pressure is 18 MPa, the average contact gap is approximately 0.018 mm. When the expansion pressure reaches 16 MPa, the contact area ratio is 91.0%. When the expansion pressure increases to 18 MPa, the contact area ratio only increases by approximately 0.6%. Compared with the influence of the expansion pressure on the increase in contact area, the influence of the pressure holding time on the contact area is lower.

Coupled heat transfer analysis of U-type tube module of LNG ambient air vaporizer under dry conditions

Liquefied natural gas (LNG) ambient air vaporizer (AAV) utilizes renewable aerothermal energy from ambient air to regasify LNG, which is usually chosen as the first choice in gas stations. Its gasification efficiency depends on the heat transfer performance of U-type finned tube which is composed of multiple straight finned tubes connected in series by U-bends. This paper developed a two-way coupled heat transfer model of AAV U-type module considering the conjugated interaction between different fluid domains and the phase interactions during the vaporization process of LNG. Experiments were conducted to validate the numerical model, and the results are in good agreement. The coupled heat transfer analysis indicates that mutually interference of the heat transfer process between two adjacent finned tubes in a U-type tube module occurs and gets more obvious as closer to the entrance of LNG. The heat flux of the inner tube surface decreases along the flow direction of LNG on the whole, yet there exists an obvious drop on the inner surface of the U-bend due to lack of fins. Besides, the heat transfer performance of the vertical straight finned tube is superior to U-type tube, and the difference is more obvious with higher LNG velocity.