Tube Heat Exchanger Research Articles

Learning experimental data to predict fluid-elastic instability and optimize configuration of tube arrays

Fluid-elastic instability (FEI) poses a particularly significant challenge to the safety of steam generators, given its potential to cause substantial damage in short periods. The tube bundle system model is inherently complex, resulting in expensive costs for experiments and numerical simulations during the design process. In this study, a substantial volume of FEI experimental data, conducted by various scholars, was compiled to create FEI surrogate model. The accuracy and feasibility of this surrogate model were demonstrated and compared to experimental results. This work represents the pioneering reference on the optimization of tube array configurations, achieved by combining FEI deep neural network (DNN) surrogate model with genetic algorithm (GA). The design variables for optimization encompassed tube array configurations and structural parameters. The optimization objective is to achieve a tubular array structure exhibiting a higher critical velocity, Ur, enabling safe operation of the heat exchanger tube bundle across a wider range of flow rates without any FEI accident. The developed approach holds promise for data-driven FEI analysis and optimized tube bundle design, resulting in substantial time and cost savings. We publicly share all code implementations, and we believe that our efforts open a door for the surrogate-model-assisted structural optimization of tube arrays.

Performance enhancement of a fin and tube heat exchanger with the novel arrangement of curved winglets using a multi-objective optimization approach

The present study considers performing multi-objective optimization of a fin and tube heat exchanger to enhance its performance. For this, a group of three curved rectangular winglets, placed on alternate sides of the tube, are considered. Two different geometrical arrangements are analyzed. In the first case – referred to as case A – the distance between the three curved blades is varied in a way that the relative gap between the curved blades is the same. In the second case – referred to as case B – the distance between the three curved blades is held fixed at the entry section, but the relative gap is varied at the exit of the curved blades. The experiments are designed using the Latin hypercube sampling technique, and the responses against each set of design variables are calculated using computational fluid dynamics. The conservation equation for mass, momentum and energy are solved along with transition SST (a three equation) turbulence model considering a steady state formulation. The resulting data is used to train the artificial neural network that serves as a surrogate model for GA to generate the Pareto front points. Conclusive results indicate that the optimized models from both cases largely outperform compared to the previously reported studies. Furthermore, the performance of the case B variant is slightly better than for case A.

Numerical exploration of the impact of fluid type in a uniquely designed shell and spiral tube heat exchanger

Shell and spiral tube heat exchangers are widely favored in refrigeration and applications such as heat recovery systems, food processing, and heat storage. Researchers' primary focus is to discover a simple and cost-effective approach to improve the efficiency of heat exchangers. The research employed a specially designed shell and spiral tube heat exchanger to enhance efficiency. This research involved utilizing ANSYS FLUENT CFD software to analyze the thermodynamic efficiency and predict heat transfer in the specified converter. The analysis incorporated factors such as displacement velocity coefficient and friction coefficient. Researchers are focused on finding a simple and cost-effective approach to improve the efficiency of heat exchangers. Furthermore, the selection of nanohybrid fluids is a crucial factor influencing the thermohydraulic performance of shell and spiral tube heat exchangers. Among the three fluid nanohybrids chosen for simulation, the water nanohybrid exhibited superior temperature performance, surpassing all other liquids. Furthermore, the optimal thermal performance for the hybrid nanofluid was observed at φ1 = φ2 = 0.7.

Experimental and Comparative Heat Transfer Analysis of Heat Exchanger with Surface Modification

This research aims to enhance the heat exchanger performance by a surface modification approach. The shot peening effect on the heat transfer performance of shell and tube heat exchanger (STHE) is experimentally studied with different surface modifications of stainless steel (SS) tube-like plain SS tube, grinded surface and blast with copper, sand & iron surface. The effect of shot peening on the surface morphology of the SS outer surface is analyzed by scanning electron microscope, and it was found that the iron blast surface has a coarse grain structure. The optimum flow rate for STHE was experimentally studied by base SS tube, and its values are compared with analytical results of computational fluid dynamics and heat transfer research. The underwater medium maintained the higher and lower temperatures of 80 °C and 30 °C, respectively. Based on the logarithmic mean temperature difference, number of transfer units (NTU), overall heat transfer coefficient, effectiveness and exergy efficiency of SS and its modified surface are experimentally evaluated, and iron blasted surface offered maximum heat exchanger performance like 100% for Stanton number, 89% for Nusselt number, 89% for overall heat transfer coefficient, 89% for an NTU, 57% for effectiveness, and 148% for exergy efficiency, while compared to SS surface without modification.

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.

Simulation study on the effect of liquid ammonia spray on the heat transfer performance of multiple heat exchange tubes

Abstract In this paper, aiming at the problems of low heat transfer efficiency and uneven heat transfer of heat exchange tubes in refrigeration and air conditioning chillers, a liquid ammonia spray cooling method is proposed, and a flow and heat transfer model is established. The distribution of refrigerant droplets in the fluid domain and the heat transfer on the surface of the heat exchange tube are simulated under different spray speeds, spray directions, and double nozzle sprays. The results show that with the increase of spray velocity, the heat transfer performance of heat exchange tubes decreases first and then increases. The effect of spray velocity on the heat transfer performance of each row of heat exchange tubes is not consistent. The farther away it is from the nozzle, the greater the speed corresponding to the peak value of the heat transfer performance improvement of the heat exchange tube will be; the spray direction (gravity) has little influence on the heat transfer performance of the heat exchange tube, which is within 5.1%. Compared with single-nozzle spray, double-nozzle spray greatly improves the heat transfer performance of multi-row heat exchange tubes.

Modelling the Relationship between Water Jetting Parameters and Material Failure in Heat Exchanger Tubes

The Zeeland-Flemish region has a robust process industry where heat exchangers (HEX) are essential for managing heat transfer. However, Fouling in HEX occurs when deposits of contaminants form on surfaces affecting heat transfer. HEX maintenance/cleaning can harm the material of construction (MoC). This study explores how altering Water Jetting (WJ) parameters affects MoC failure mechanisms. This knowledge can optimize processes to prevent unwanted MoC failure while achieving desired fouling control. In this study, a three-factorial experiment was designed to investigate how increased water pressure and flow rates impact the structural health of copper used in HEX tubes during WJ cleaning. Then, we compared these results with experiments using steel as the MoC. Statistical and mathematical analysis were employed to understand the effect of process parameters on damage mechanisms and identify the most influential parameter. For copper samples, we observed that higher water pressure consistently increased damage across all flow rates, following a linear trend of α_p =0.001(gm loss/gm sample. Kpsi). Flow rate's impact on damage exhibited logarithmic behavior, which can be split into two ranges. At low to medium flow levels, increased flow rates raised damage at a rate of α_f =0.007(gm loss/gm sample. gpm). However, at high flow rates, the increase in flow had no effect on the damage as it was attributed solely to pressure. Comparing steel and copper at high pressure levels, it was found that steel experienced a lower linear increase in damage, β_f =0.0036(gm loss/gm sample. gpm), compared to α_f for copper. These results offer insights for optimizing water jetting cleaning processes to minimize material damage during HEX maintenance, enhancing overall efficiency.

Vibration-Enhanced Heat Transfer Analysis and Improvement of Spiral Elastic Tube Heat Exchanger

Using the fluid–solid coupling approach in fluid-induced vibration studies, the effect of flow-induced vibration on a heat exchanger is investigated. This paper analyzes the impact of flow parameters for shell fluid on heat transfer characteristics enhanced by the vibration of a spiral elastic tube bundle (SETB). Improvement schemes for heat exchangers are also proposed, and they are studied and compared. The results show that there is a positive correlation between the inlet velocity and the heat transfer coefficient of the SETB heat exchanger. As the inlet velocity rises to 0.9 from 0.3 m/s, the Nusselt number of the hollow SETB heat exchanger under vibration conditions is increased by 153.10, 45.55, and 26.73% sequentially. The vibration generated by impacting the elastic element during fluid flow can improve the Nusselt number effectively. As the flow velocity increases to 0.9 from 0.3 m/s, the flow-induced vibration enhances the Nusselt number of the hollow SETB heat exchanger by 2.13, 1.53, 1.05, and 0.89%. When the inlet flow velocity of fluid is in the range of 0.3–0.9 m/s, under the same flow velocity, same pressure drops, and same pumping power conditions, the performance of the improved heat exchanger is greater than that of the SETB heat exchanger before the structural improvement.

Innovative rotary friction welding of heat exchanger tube nozzles on high pressure headers

This paper describes an innovative application, driven by an industrial requirement for an alternative welding process to submerged arc welding of header heat exchanger tube nozzles, of an automated friction hydro-pillar processing (FHPP) welding platform (WeldCore©). This was the first successful application of rotary friction welding of heat exchanger tube nozzles to high pressure-headers used in the high-pressure heaters of a boiler on a 609 MW steam turbo-generator unit. The FHPP WeldCore platform allows highly time- and cost-effective welding and repair of high temperature, high pressure power plant using a procedure that was approved in the 2015 ASME Boiler and Pressure Vessel Code, Supplement 3 as Code Case 2832 (WPS qualification for Friction Taper Hydro-Pillar (FTHP) welding). This certification opened the way to using FHPP welding for repair and refurbishment of power generation and high temperature process plant. After completing the welding of 448 nozzles onto each of two HP headers, all welds were found to be defect-free using ultrasonic testing, and test nozzle welds passed the weld qualification procedure required by industry.

Experimental Analysis of Heat Transfer Enhancement in Double Tube Heat Exchanger with Air Injection

Double-tube heat exchangers are frequently utilized due to their low assemble and maintenance cost. In order to extract a large amount of thermal energy at minimum time and cost, an active method of air bubble injection was developed to increase the heat transfer rate through vertical double-tube heat. The current study explores the influence of air bubble injection on the thermal efficiency of vertical double tubes at counter flow. There were two main modes were adopted to conduct the experiments. The first mode was done without air injection (single phase). In the second mode, the air was injected into the heat exchanger's outer tube through a ring tube into the annular side of the heat exchanger. Cold water flow rate was ranged as (3, 3.5, 4, 4.5, 5 LPM) with 17°C temperature, while hot water was kept constant at (3LPM) with inlet temperature 70°C, and air was injected with (0.5, 1, 1.5, 2 LPM). Results found that overall heat transfer was enhanced by (41%), NTU (49%), effectiveness enhanced by (44%) and Nusselt number (45.2%).

Role of various influencing parameters on high temperature fretting behaviour of different tribopairs in liquid lead

The increasing interest in liquid metal cooled nuclear reactors provides technical and scientific challenges such as the understanding, prevention, and prediction of the degradation of materials in liquid lead. Critical components include the fuel rods, heat exchanger tubes, and pump impellers. These functional elements are exposed to mechanical loading (up to 40 MPa), high temperatures (450–550 °C), and fluid-induced vibrations (up to 25 Hz). Under such conditions, fretting wear occurs between e.g., the spacer wire and the outer surface of the fuel or heat exchanger tubes. This work is aimed to establish a laboratory-scale fretting wear test setup and develop test methodology to enable systematic material characterisation in liquid metal environments. The results obtained by using the described methodology indicate that adhesive wear is the dominant degradation mechanism, and 316L stainless steel shows a higher coefficient of friction but a lower wear volume/tribolayer volume compared to 100Cr6 bearing steel. These results are in agreement with those reported in open literature and demonstrates the suitability of the presented method for conducting fretting tests and analysis for various materials and contact configurations in liquid lead environment.

Field test on thermal control for bridge piers on plateau through energy pile

This study presents a sustainable thermal control method (energy pile technology) for bridge piers in high-altitude regions, addressing the challenges posed by temperature variations in mass concrete structures. The proposed method involves integrating various heat exchange tubes within the pile foundation, pile cap, and bridge pier concrete to harness shallow geothermal energy. This paper summarizes failure cases of bridge structures due to the impact of thermal loads. Through three field tests on a plateau, the feasibility and practicality of the energy pile technology are verified. The system exhibits promising results, achieving a maximum temperature difference reduction of 3.9°C and a reduction of 53.4%. Furthermore, the method has effectively reduced the expansion strain on the sunny side of the bridge piers, with a maximum reduction of up to 44.4%. Importantly, the energy pile technology has minimal impact on the pile foundation, with negligible constrained stress variation. The study evaluates the heat exchange efficiency and energy efficiency of the energy pile-based system, reporting stable heat exchange rates and a comprehensive Coefficient of Performance (COP) reaching up to 4.0. The findings highlight the potential of this sustainable temperature control methodology to enhance the resilience and longevity of critical infrastructure in challenging climates.

An investigation of the thermo-hydraulic performance of a novel double tube heat exchanger with variable cross-section inner tube for trans-critical CO2 cycle

Double tube heat exchangers (DTHE) is one of the most significant components in the trans-critical CO2 cycle system, whose performance significantly affects the efficiency and compactness of the system. This work aims to improve the heat transfer performance of CO2 at supercritical pressure in DTHE. In this paper, the cylindrical inner tube of traditional DTHE is changed into the diverging/converging tube as an innovative design without increment of its heat transfer areas. The thermal–hydraulic performance of traditional DTHE with uniform cross-section inner tube (UIT), DTHE with diverging (DIT)/converging (CIT) inner tube were numerically investigated by using SST k-ω turbulence model. The results show that under the same operating conditions, the DIT and CIT can effectively enhance the heat transfer compared with the UIT. Utilization of DIT and CIT instead of UIT, the maximum increase of the total heat transfer coefficient are 27.3 % and 24.2% can be obtained, respectively. However, the pressure drop of DIT and CIT also increases accordingly. The performance evaluation criterion (PEC) of DIT is always greater than 1, and the maximum is 1.16. In most cases, the PEC of CIT is greater than 1, but with the increase of SCO2-side mass flow rate, it gradually decreases to less than 1. The comprehensive performance of DIT is the best. The heat transfer mechanism is analyzed from the aspects of flow field distribution, thermos-physical property and field synergy theory. The large turbulent kinetic energy near the wall, high thermal conductivity and large specific heat of SCO2 in the tube are the main reasons for the enhanced heat transfer of DIT and CIT. Finally, the influence of SCO2-side pressure and mass flow rate on local heat transfer coefficient hCO2 in DIT are also further studied. This study can provide some guidance for the design and optimization of DTHE.

Experimental study on the scaling law of the heat exchange tube surface in the process of low-temperature single-effect distillation of high-mineralized mine water

High-mineralized mine water, due to its characteristics such as high mineralization degree, will have scaling phenomena on the surface of the heat exchange tube during the desalination treatment process, resulting in a reduction in the water production efficiency of the equipment and affecting the normal operation. To reduce the cost of water production and improve the service life of distillation equipment, this paper independently designs and builds a low-temperature single-effect distillation high-mineralized mine water experimental system to study the influence of operating parameters (temperature, spray density, concentration ratio, and system pressure) on the scaling law on the surface of the heat exchange tube. The distribution and characteristics of scale deposits on the surface of the heat exchange tube are analyzed through the growth rate and microscopic morphology of the scale deposit. The results indicate that the scaling on the surface of the titanium plate is mainly in the needle-like and rod-like morphology of CaCO3 aragonite, and a small amount of CaSO4 and calcite are generated with the increase of temperature. It was found that within the range of spray density from 0.0509 kg/(m·s) to 0.0625 kg/(m·s), concentration ratio from 2.3 to 2.7, and system pressure at 36.3 kPa, it is beneficial to the evaporation heat transfer of the heat exchange tube and the reduction of scaling generation. At the same time, it is found that the scaling of the first row of heat exchange tubes is mainly within the range of circumferential angle from 0 to 100 degrees, and the scaling of the second row and the third row of heat exchange tubes is mainly within the range of circumferential angle from 110 to 170 degrees. The research results of this paper provide support for the design and operation of the low-temperature multi-effect treatment system for mine water in engineering, promote the process of zero discharge of high-mineralized mine water in Xinjiang, China, and improve the resource utilization rate of high-mineralized mine water.

Numerical investigation of thermal-hydraulic performance enhancement in helical coil heat exchangers with twisted tube geometries

This numerical study examines the thermal-hydraulic performance of helical coil heat exchangers (HCHEs) using twisted tubes versus conventional circular tubes. The effects of Reynolds number (Re = 10,000 to 100,000), pitch length (11, 7.2, 5.5, 3.6 mm), and twisted tube orientation (co-current, counter-current) on heat transfer efficiency and pressure drop were investigated. The results show that higher Reynolds numbers can reduce the Resistance factor by approximately 25 % and improve heat transfer by approximately 35 %. An optimal pitch length of 5.5 mm was found to balance enhanced heat transfer and manageable pumping costs. Twisted tubes demonstrate significant performance advantages at lower Re, with 20–33 % higher Performance Evaluation Criterion (PEC) values compared to circular tubes. However, the benefit diminishes at higher Re, with less than 10 % PEC increase. Implementing counter-current twisted tube configurations leads to approximately 13 % higher Nusselt number and 11 % higher Resistance factor, resulting in a 10 % overall PEC improvement. These findings highlight the superior thermal-hydraulic performance of twisted tubes in HCHE applications, especially at lower Reynolds numbers. Future work could explore different fluids, advanced optimization, energy analysis, cost assessment, and additional geometric parameters to further enhance twisted tube heat exchanger design and performance.

Numerical Simulation of Heat Transfer Enhancement of a Heat Exchanger Tube Fitted with Single and Double-Cut Twisted Tapes

Numerical Simulation of Heat Transfer Enhancement of a Heat Exchanger Tube Fitted with Single and Double-Cut Twisted Tapes

Numerical investigation of the effect of fluid nanohybrid type and volume concentration of fluid on heat transfer and pressure drop in spiral double tube heat exchanger equipped with innovative conical turbulator

Spiral heat exchangers in the heat transfer field have attracted researchers' attention due to their better heat transfer characteristics. This review discusses the increase in efficiency of this type of converter. to better understand the efficiency of the intended spiral exchanger, thermal efficiency (performance evaluation criteria) was chosen as the performance index in the present work, and the simulations were carried out in a calm regime (200<Re<800) and for two positive and negative flows and using three types of fluids. This study aims to conduct a numerical analysis of the impact of nanohybrid fluid type and fluid volume concentration on heat transfer and pressure drop in a spiral double-double-tube exchanger incorporating a conical turbulator. Computational fluid dynamics was employed in the study. The problem is tackled using ANSYS FLUENT 18 to conduct CFD simulations utilizing the finite volume method. The numerical findings indicate that employing countercurrent flow and a nanohybrid fluid of Water/MoS2–Fe3O4 significantly impacts overall performance, potentially boosting the spiral heat exchanger's efficiency by 8 %. The findings indicated that raising the volume concentration of the nanohybrid fluid Water/MoS2–Fe3O4 from 0.3 % to 0.5 % and 0.7 % leads to a notable enhancement in the thermal efficiency of this converter type. The converter achieves its peak efficiency at Reynolds number 200 when using the nanohybrid fluid Water/MoS2–Fe3O4, resulting in a 4 % and 17 % increase in thermal performance compared to the other two concentrations.

Numerical Research on Aerosol Transport and Deposition Inside a Heat Exchanger Tube Based on Lagrange Methodology

Numerical Research on Aerosol Transport and Deposition Inside a Heat Exchanger Tube Based on Lagrange Methodology

Experimental study of solid particles in thermal energy storage systems for shell and tube heat exchanger: Effect of particle size and flow direction

The solid particle thermal energy storage method offers cost-effective, simple, and high-temperature suitable solutions. It effectively resolves chemical compatibility and thermal stress issues in shell-and-tube heat exchangers. This work studies the quartz sands' particle sizes and flow direction's impact on heat exchanger performance. The results show that heat conduction and natural convection heat transfer mechanisms exist on the particle side. Flow direction minimally affects charge/discharge time and stored energy but significantly impacts delivered/recovered energy and exergy and energy and exergy efficiencies. Optimal performance is achieved when HTO enters from the top during charging and from the bottom during discharging, creating a transparent thermal gradient of “Top Temperature High, Bottom Temperature Low”. This distribution minimizes natural convection losses, resulting in a 15–17 % increase in energy efficiency and an 11–13 % increase in exergy efficiency compared to reverse flow. Smaller particles show slightly faster temperature rise due to lower energy storage density. Large and medium particles perform well, achieving energy efficiencies of 81.5 % and 81.0 % and exergy efficiencies of 62.1 % and 61.8 %, respectively. Small particles have an energy efficiency of 79.0 % and an exergy efficiency of 60.4 %, possibly due to higher porosity and increased heat losses.

Comprehensive corrosion failure analysis of HAl77-2 alloy tubes serving in a low temperature multi-effect distillation plant: From feature analysis to corrosion mechanisms

Premature perforation and leakage of HAl77-2 alloy heat exchanger tubes occurs after 2.5 years of service in the largest low temperature multi-effect distillation (LT-MED) plant in China. The root reasons of perforation and leakage of tubes were investigated through macroscopic morphology, chemical composition, metallographic structure, seawater quality, flowing simulation and microstructure characterization. The results show that the HAl77-2 alloy tubes with perforation leakage meet the standard requirements. And the failure of the tubes was mainly attributed to the synergistic effect of serious pitting corrosion and stress cracking caused by the high fluid pressure and polluted seawater with Fe2+/Fe3+, sulfide and NH4+. Especially, the velocity and pressure spatial distribution of liquid film on the outside of horizontal tubes well verified the interesting observation that corrosion pits concentrating in one strip on the top of the tube. Moreover, corrosion mechanism was proposed that the loose corrosion products of Cu2S, FeS and Cu2(OH)3Cl lead to the formation of some defect points on the homogeneous protective Cu2O layer. For these defect points, the direct expose of the alloy matrix to corrosive substances such as Cl− and NH4+, significantly accelerates the dissolution of Cu in form of CuCl2− and Cu(NH3)2+ from the alloy. Finally, the tube occurs pitting corrosion and even perforates under the strong hydraulic erosion after long-terms of operation.