Helical Fins Research Articles

Numerical investigation of the geometric parameters effect of helical blades installed on horizontal geo heat exchanger

In this study, we investigate the enhancement of horizontal geothermal heat exchangers equipped with helical fins on the pipe's exterior and internally ribbed turbulators. Our approach focuses on the interplay between geometry and thermal efficiency through innovative design modifications. Utilizing the finite element method, three-dimensional numerical simulations assessed the effects of varying geometric parameters such as the diameter and thickness of the fins. Our findings indicate significant increases in heat transfer efficiency with the addition of helical fins; specifically, increasing the fin diameter from 5 mm to 10 mm results in a 15 % increase in the heat transfer rate, while doubling the fin thickness from 2 mm to 4 mm enhances the rate by 10 %. These improvements are due to the expanded surface area facilitating greater heat exchange. Optimization using the desirability function approach yielded models with high performance, achieving desirability scores of 0.9879 for outlet temperature and 0.9534 for the heat transfer coefficient. This reflects the effective tuning of geometric parameters to maximize thermal performance. The study also introduces two predictive mathematical models for the outlet temperature and convective heat transfer coefficient of the U-shaped pipe equipped with these enhancements. These models, derived from extensive numerical data, provide practical tools for future design and operational applications of geothermal heat exchangers. This research advances the design and operational efficiency of geothermal heat exchange systems, establishing new benchmarks for thermal efficiency in the field with actionable insights and robust mathematical tools.

Thermal performance improvement for parabolic trough solar collectors integrated with twisted fin and nanofluid: Modeling and validation

The low thermal efficiency of parabolic trough solar collectors (PTSCs) is a major drawback that has hindered their development as a viable renewable energy resource. Among the available methods to enhance the thermal performance of PTSCs, installing internal fins within the collector tube is one of the most reliable, economical, and straightforward passive techniques. However, while internal fins can significantly improve thermal performance in turbulent flows, they also lead to a substantial increase in pumping work. Here, we demonstrate that with an optimal design of helical fins, the thermal efficiency of PTSCs can be improved without causing significant pressure losses through the receiver tube. The results proved that higher thermal efficiency and lower pressure losses were achieved when annular fins are replaced by an axial helical insert. Installation of a helical fin with 4 turns and a height of 4 mm led to a 4.5 % increase in thermal efficiency (η) while raising the friction factor (f) by 30 %. Optimal performance was observed with helical fins having 10 turns. For instance, at Re = 105, switching from 16 to 4 turns of 8 mm helical fins resulted in η and Nu enhancements, and f reduction of 1.6 %, 33 % and 64 %, respectively. While these changes were 2.0 %, 55 % and 54 % when n reduced from 16 to 10.

Flow and Heat Transfer Experimental Study for 3D-Printed Solar Receiving Tubes With Helical Fins at Internal Surface

Abstract 3D-printing technology was applied to fabricate novel solar thermal collection tubes that have internal heat transfer enhancement fins and external surfaces with high solar absorptivity and low emissivity due to the ability to use different materials in one tube. Helical fins were selected to introduce circumferential flow and thus minimize the circumferential temperature difference of the tube that receives sunlight on one side. The structures of the helical fins were previously optimized from computational fluid dynamics (CFD) analysis with the objective of low entropy production rate by looking for high heat transfer coefficient and relatively lower pressure loss. High-temperature alloy, Inconel-718, was used to 3D print the tubes, which can resist corrosion for the potential application of molten chloride salts as heat transfer fluid. Experimental tests were carried out using water as the heat transfer fluid with the high heat flux provided by a tubular furnace heater. The tested Reynolds number ranges from 3.9 × 103 to 6.1 × 104. Heat transfer coefficients of up to 2.8 times that of the smooth tube could be obtained with the expense of increased pressure loss compared to that of the smooth tube. The total system entropy generation can be significantly reduced due to the benefit of heat transfer enhancement that is greater than the expenses of the increased pressure loss. The experimental results of the 3D-printed heat transfer tubes confirmed the CFD-based results of fin optimization. The novel heat transfer tube is recommended for application in concentrating solar power systems.

Improving the performance of a shell and tube latent heat thermal energy storage through modifications of heat transfer pipes: A comprehensive investigation on various configurations

The modification of the geometric configurations of heat transfer pipes in shell and tube Latent Heat Thermal Energy Storage (LHTES) systems not only enhances the melting process of the phase change material (PCM) but also improves the overall performance of these systems. This study aims to investigate ways to enhance the performance of LHTES systems by employing heat transfer pipes with various fin and twisted tape arrangements in a horizontal orientation. The Finite Volume Method and Enthalpy-Porosity method are employed to simulate the melting process. Stearic acid is used as the PCM material, while water serves as the heat transfer fluid. Eight different geometric configurations are modelled in the LHTES system: base case, horizontal fins, vertical fins, helical fins, horizontal tape, vertical tape, twisted tape and helical fins with twisted tape. The results show that within the time range of 0 and 29 min, the combined configuration of helical fins with twisted tape consistently demonstrates the fastest melting process. After 29 min, the configuration with vertical fins exhibits a marginally faster melting process than the combined configuration of helical fins with twisted tape. The configurations involving tapes also contribute to accelerated melting, although to a lesser extent than those with fins. Particularly, twisted tape proves highly effective in facilitating faster melting. The complete melting process times for configurations with vertical fins, helical fins, and combined helical fins with twisted tape are 38.7 %, 23.5 % and 32.7 % faster compared to the base case which is ∼69 min. Among the configurations, using tapes results in higher flow resistance and surface area compared to the base case. The attractive features of these configurations make them ideal for creating efficient and space-saving energy storage systems. This study provides crucial insights into essential heat and mass transfer processes, which can be leveraged to develop advanced LHTES systems for enhanced performance and sustainable energy solutions.

Influence of variable gravity on the phase change material for enclosed vertical channels with helical fins

This study numerically investigates the influence of variable gravity on the melting behaviour of a phase change material (PCM- paraffin wax RT27) contained within an enclosed vertical channel under different gravity conditions, specifically those found on the Earth, the Moon, and under the microgravity environments. Furthermore, the impacts of incorporating various number of helical fins within the PCM unit under different gravitational conditions are assessed for the first time. The findings indicate that the melting efficiency of PCM is considerably affected by the reduced gravity conditions, due to changes in the natural convection, velocity, and temperature; the melting time is twice as long under the moon-gravity conditions and sixfold longer under the microgravity conditions compared to the earth-gravity. It is also observed that reduced efficiency can be remedied by the insertion of fins into the PCM unit. The breakdown of the natural convection vortices with different number and orientation of fins expedites the melting process for all gravity conditions thus leading to improved performance in melting and energy storage.

1D modelling of a latent heat thermal energy storage prototype using boiling water as heat transfer fluid

This paper presents a numerical model to simulate the thermohydraulic behaviour of a shell-and-tubes Latent Heat Thermal Energy Storage (LHTES) during discharging period, involving a boiling heat transfer fluid (HTF). It is based on a 1D homogeneous approach for the HTF (water) and a 1.5D approach for the phase-change material (sodium nitrate) allowing calculation times significantly shorter than those of CFD. This approach has been validated with experimental data in a previous study for a LHTES with a monophasic HTF. The two highlights of this paper are as follows: On the one hand, computational fluid dynamics has been used to develop equivalent homogeneous materials for PCM side, integrating the thermal properties of the phase-change material and the helical and longitudinal fins present in the LHTES. On the other hand, the model uses the asymptotic correlation of Steiner and Taborek to describe boiling heat transfers and usual correlations for single phase heat transfers. The paper focuses on the validation of the model against experimental data from the InPower project. The prototype is a 340 kWh storage that has been tested under different conditions. The model reproduces the total energy retrieved during a system discharge with relative error of 8.5% and an absolute mean error of 8.23 kW on outlet power. The main weakness of the model is the homogeneous model for the HTF that generates error in water level and local temperatures.

An Experimental Study of Heating Heavy Fuel Oil by Hot Air using Helical Fins in a Double-Pipe Heat Exchanger

In present work, the effect of helical fins with height 20 mm and pitch 100 mm on the performance of the double pipe heat exchange investigated experimentally. The heat exchanger had been chosen as a heat recovery device in bricks factory to recover heat from exhaust gases to preheat the heavy fuel oil. Air had been chosen as a hot gas instead of furnace exhaust gases because of the similar thermal properties and it flows in the inner pipe with different velocity (20, 27, and 34) m/s and inlet temperature (200, 225) °C while, heavy fuel oil enters shell side with counter flow at mass flow rates (0.06, 0.08, and 0.1) kg/s and constant inlet temperature of 40 °C. Both of pipes and helical fins are made from stainless steel. The experimental results show that increasing Reynolds number from 139139 to 333934 led to increase heat transfer rate, oil outlet temperature, overall heat transfer coefficient and effectiveness of heat exchanger with (8%, 4%, 5% and 5%) respectively while, increasing oil mass flow rate from (0.06 to 0.1) kg/s cause decreasing oil outlet temperature and effectiveness of with (10% ,14%) respectively. The results shown the double pipe heat exchanger with helical fins produce heat transfer rate and oil outlet temperature higher than smooth double pipe heat with average 15% and 8.6%, as well as increasing Nusselt number, Overall heat transfer coefficient and effectiveness of heat exchanger with average 26%,15% and 13% respectively. The results clear that, for 225°C exhaust air and velocity 27 m/s, the application of double pipe with helical fins by preheat heavy fuel oil could reduce the viscosity and reduce electric power required and save 1.69 MW annually for one factory.

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.

Effect of internally mounted helical fins on the separation performance of a cylindrical gas-solid cyclone separator

In this study, an innovation was made by adding helical fins on the vortex finder of a cylindrical gas-solid cyclone separator, and the effect of this structural improvement on the separation performance was analyzed based on the flow field characteristics. The results show that both cyclones with and without helical fins exhibit a separation efficiency of almost 100% for particles larger than 5 ?m. As the inlet velocity increases, the effect of adding helical fins on the overall separation efficiency decreases, with a relative deviation of only 0.16% at an inlet velocity of 27 m/s, while it becomes increasingly effective in reducing energy consumption, with a pressure drop of 25.33%. The mechanism of the overall performance improvement lies in the fact that the helical fins change the flow field distribution in the cyclone, where the turbulence intensity in the vortex finder is significantly reduced, the tangential velocity of the external vortex is decreased, and the pressure gradient is reduced. The purpose of this paper is to provide new ideas for the optimal design of the internal components of the cyclone separator.

Thermal performance enhancement in the receiver part of solar parabolic trough collectors

In this study, CFD analysis for thermal performance of absorber tube with inner helical axial fins which is used in solar PTC collector is considered and compared. Three-dimensional numerical model simulations were performed using flow and heat transfer interfaces in COMSOL Multiphysics software. Water is used as heat transfer fluid and copper was chosen as receiver tube material. Sun's radiation is considered as constant at around (Io=1000 W/m2) and concentration ratio is C=60. Inlet velocity of heat transfer fluid is changed from 0.2ms to 0.2 4 ms in order to define its magnitude with the length of absorber tube. Electrical analog method is utilized for mathematical modeling to evaluate heat losses through the absorber tube. Variations of surface and fluid temperature are determined to investigate the receiver which shows better performance in the given boundary conditions. In the discussion section of the article, temperature variation of the receiver tube and HTF during this process is presented.

Thermal performance promotion of a novel double-tube heat exchanger by helical fin with perforations

Double-tube heat exchangers are widely used in many fields. A novel double-tube heat exchanger with a perforated helical fin on the annulus side is proposed in this paper for thermal performance promotion. The effect of different perforation diameters ranging from 0 to 12 mm on the fluid flow and heat transfer are numerically studied under a turbulent state with Re ranges between 4000 and 16,000. The results showed that perforation diameter has a significant influence on the thermal performance. There exists an optimum perforation diameter for the best thermal performance. The largest value of Nu in the helical finned annulus increases by 20.2% by perforation, while the corresponding f only increases by 11.0% compared with the normal helical finned configuration without perforation. The thermal performance evaluation factor JF is also improved by up to 16.1% compared with the helical finned configuration without perforation, and is increased by 48.6% compared with the smooth annulus. Correlation formulas of f, Nu, and JF are fitted and the deviations are within ±4%, ±9%, and ± 5% for f, Nu, and JF, respectively. Perforated helical fin is an efficient annular-side heat transfer enhancement technology that can be applied to the optimized design of double-tube heat exchangers.

Thermal performance enhancement in an indirect solar greenhouse dryer using helical fin under variable solar irradiation

In this study, the effect of helical fins on the thermal performance of the greenhouse solar dryer with solar air heater under non-uniform thermal radiation has been analyzed. This article is written with the aim of investigating various parameters, including the type of helical fin (CASE A to CASE D), pitch of the helical fin (170 mm to 320 mm), mass flow rate (0.01, 0.013, 0.015 kg/s) and variable solar irradiation (10:00 AM to 14:20 PM). The 3D simulation was performed using the finite volume method (FVM) in ANSYS-Fluent software under k-ε RNG turbulent modeling. The results demonstrate that using four helical fins inside the tube increases the outlet temperature by 5.22 % at 10:00 AM. Compared to the simple model. Increasing the flow rate cause less opportunity for heat transfer rate from the solid surface to the airflow, so the outlet temperature decline by 19 % when the air flow rate rise to 0.015 kg/s. In the flow rate of 0.01 kg/s, by decreasing the pitch of the helical fin from 320 mm to 170 mm, the greenhouse outlet temperature rises by 3.01 %. Unexpectedly, changes in solar irradiation at different flow rates do not exhibit a linear correlation with thermal efficiency. Nevertheless, the highest achievable thermal efficiency of 61.30 % occurs at 13:00 with an airflow rate of 0.015 kg/s.

Thermal characteristics of a small-scale medium- and high-temperature latent heat storage system at different inlet flow rates and their influencing factors

This study investigates the impact of heat transfer fluids (HTFs) operational parameters on latent heat storage (LHS) systems, focusing on medium and high-temperature storage. A small-scale, visualized setup with a compact shell-and-tube heat exchanger, featuring helical fins, was constructed to enhance heat exchange. Dense thermocouples and flow meters recorded temperature and flow data of the phase-change material (solar salt) and HTF (heat transfer oil) during charging and discharging cycles, enabling detailed thermal analysis.Results show that higher HTF flow rates significantly reduce cycle time. Increasing the flow rate from 15 to 35 L/min decreased the discharging time from 176.5 to 146.4 min, a 17 % reduction, and improved energy injection/extraction efficiency. Lower rates, however, stabilize energy output and slightly increase cycle efficiency (from 51.58 % at 15 L/min to 52.45 % at 35 L/min). Additionally, the study identified a correlation between storage temperatures and flow rates: higher temperatures boost the efficiency of high flow rates in reducing melting time, while lower temperatures enhance the positive effects of low flow rates on circulation efficiency. These findings provide essential guidance for parameter selection in LHS system engineering applications.

Impact of Built‐in Helical Fins on the Performance of Oil‐Gas Cyclone Separators

AbstractAn improved design was proposed by incorporating helical fins onto the vortex finder, and the impact on the comprehensive performance of the oil‐gas cyclone separator was analyzed based on flow field characteristics. The results revealed that the integration of helical fins led to a slight enhancement in the overall separation efficiency and a significant reduction in pressure drop, thus contributing to the decrease of energy consumption in industrial processes. The orthogonal experimental design (OED) method was utilized for the discussion and optimization of five structural parameters related to the helical fins. This study provides new insights for the design of internal components of oil‐gas separators.

Numerical investigation of battery thermal management by using helical fin and composite phase change material

Li-ion batteries have become an indispensable part of modern life thanks to their portability, energy density, fast charge-discharge capability and various application areas. The thermal performance of the PCM promising method for battery thermal management systems (BTMS) is limited due to weak thermal conductivity property. The aim of this study is to investigate the contribution to the performance of BTMS by using innovative helical fins to improve the heat transfer performance of PCM due to its low thermal conductivity. Besides, the study includes composite phase change material (CPCM) due to advantages in practice such as form stability, mechanical behavior and higher thermal conductivity compared to PCM. In this scope, a hybrid system including helical fin and CPCM, paraffin-based expanded graphite (EG), is numerically investigated to ensure thermal control of a Li-ion battery in this study. Results shows that safe operating time is prolonged by increasing the widths and the number of rounds of the helical fin. However, the contribution of the EG fractions on the BTMS is ordered as an EG fraction of 12 % > 6 % > 20 % > 0 % due to a balance between the thermal conductivity and the latent heat property. The longest safe operating time is obtained by using Fin_W6-NR3 for EG fraction of 12 % in the CPCM as 9316 s corresponding to 244.0 % higher than the case of EG = 0 % and no fin used.

Helical Fins for Concentrated Solar Receivers: Design Optimization and Entropy Analysis

Abstract Concentrated solar power (CSP) with thermal energy storage (TES) has the potential to achieve grid parity. This can be realized by operating CSP systems at temperatures above 700 °C with high-efficiency sCO2 power cycles. However, operating CSP systems at such temperatures poses several challenges, among which the design of solar receivers to accommodate increased thermal loads is critical. To this end, this work explores and optimizes various swirl-inducing internal fin designs for solar receiver tubes. These fin designs not only improve the thermal performance of receiver tubes but also levelize temperature unevenness caused by non-uniform thermal loading. In this work, the geometric parameters of the fin designs are optimized to maximize the Nusselt number with a constraint on the friction factor. This optimization, however, is computationally intensive, requiring hundreds of simulation calls to computational fluid dynamics (CFD) models. To circumvent this problem, surrogate models are used to approximate the simulation outputs needed during the optimization. In addition, this study also examines the fin designs from an entropy generation perspective. To this end, the entropy contributions from thermal and viscous effects are quantitatively compared while varying the operational Reynolds number.

Thermal storage performance of latent heat thermal energy storage device with helical fin under realistic working conditions

Latent heat thermal energy storage has garnered increasing interest and development as a significant technique for recovering waste heat. In this research, the latent heat thermal energy storage device with helical fin is proposed and its thermal storage performance is also investigated by numerical simulation. First, assorted helix pitches (400 mm, 200 mm, 100 mm and 50 mm) and fin numbers are taken into account to investigate the thermal storage performance with various fin parameters. Then, four types of nanoparticles (SiC, TiO2, CuO and Al2O3) are dispersed into the phase change material to address the inherent defect of poor thermal conductivity of phase change material. Afterwards, several realistic working circumstances, including four inclination angles (θ = 0°, 30°, 60° and 90°) and eight oscillating inlet temperatures among which the frequencies are 1 Hz, 2.5 Hz, 5 Hz and 10 Hz, and amplitudes are 0.25, 0.5, 1 and 2, are selected to explore the impact on melting process. The results indicate that shortening helix pitch and increasing fin number can accelerate the melting rate, while the selection of these two parameters needs to consider the thermal storage performance and the processing difficulty as a whole. Furthermore, the selection of nano phase change materials needs to balance the relationship between thermal storage rate and capacity. Compared to the complete melting time when the device is placed vertically, the complete melting time is reduced by 14.3% when the device is placed horizontally. Utilizing the oscillating inlet temperature reduces the complete melting time by at least 21.2% compared to using the steady inlet temperature. When the frequency value is increased from 1 to 10, the complete melting time is only reduced by 3.4%. Complete melting time of the amplitude of 2 is 12.9% shorter than that of the amplitude of 0.25.

Influence of using nanofluid and phase change material on the performance of a solar thermal panel to provide the required energy of an office building in a mine

This paper examines the effect of using fins installed on tubes placed under a solar panel (SOP) numerically. The SOP is employed to generate electricity and hot water in a mine. The helical fins are mounted around the tubes under the SOP. By changing the cross-section of the fins, unsteady simulations are performed. Besides, OM37 phase change material (PCM) is utilized under the SOP and the tubes are placed inside the PCM. Alumina water nanofluid (NFD) flows inside the tubes, which are analyzed in two phases. The results show that for models M1 and M2 in 1500s, the use of tubes with a DIT of 5 mm under the SOP leads to a decrease in the SOP's average temperature of 8.58 and 8.24° respectively. The use of model M2 results in a lower outlet temperature (T-O) of the NFD when the tube DIT is 3 mm. Model M1 leads to a lower NFD T-O most of the time. Using the designed solar system can provide 56% of the hot water needed in the hot seasons and 18% of the hot water needed in the cold seasons for the building placed inside the mine.

Investigation of solar Photovoltaic cell utilizing hybrid nanofluid confined jet and helical fins for improving electrical efficiency in existence of thermoelectric module

One of the choices for improving the productivity of a PVT solar unit is selecting a more effective cooling unit. To reach the better configuration of cooling technique, the circular tube has been equipped with helical fins in current study. Also, the confined jet has been considered in the bottom of the PVT system. The existence of a thermoelectric layer under the Tedlar layer makes the electrical performance increase. The testing fluid consists of the mixture of water and ND-Co3O4. The regime of flow in both duct and heat sink is laminar and the properties of testing fluid were predicted according to homogeneous mixture. The validation step showed that present code has good accuracy with published experimental data. Among various scrutinized configurations of fins, the best performance obtained for the case with four fins and nine revolutions. Although such configuration makes the overall efficiency to increase about 9.12%, it should be evaluated in view of pressure drop with calculating performance evaluation coefficient (PEC). The value of PEC of best case is about 5.4 which means that it is logical to use such configuration. Combining the jet with the best configuration of cooling duct makes the temperature uniformity and overall performance to increase about 62.38% and 10.58%.

Influence of heat transfer fluid on thermal performance improvement of latent heat storage unit with helical fins

The helical fins can improve the hampering effect of classical fins on the convection flows of latent heat storage units (LHSU) as an innovative design, but their thermal performance improvement was largely affected by the operational conditions of heat transfer fluid (HTF), especially for fluid temperature and velocity. Based on this, an experimental system was established to measure thermal performance of latent heat storage units with perforated and solid helical fins (PHF-LHSU and SHF-LHSU). Two inlet temperatures were considered as 65 °C and 75 °C in the charge process and 20 °C and 30 °C in the discharge process, while three velocities were employed as 0.5 L/min, 1.0 L/min and 1.5 L/min. Experimental results showed PHF-LHSU exhibited the higher thermal performance than SHF-LHSU, especially in temperature response and average Nusselt number. Increasing HTF temperature from 65 °C to 75 °C increased melting rate, the average heat flux, Nusselt number and thermal efficiency by 25.4%–31.6%, 65.9%–70.6%, 15.9–25.9% and 9.7%–11.6% in the charge process, while reducing HTF temperature from 30 °C to 20 °C lowered the solidifying rate, the average heat flux and thermal efficiency by 39.3%–47.4%, 52.5%–56.6%, and 30.7%–35.3% in the discharge process. The HTF velocity had the certain effects on thermal properties and with the HTF velocity increasing from 0.5 L/min to 1.5 L/min, the thermal efficiency was increased by 3.9%–4.7%.