Tube Arrangement Research Articles

Heat Transfer Performance Tests of a Circular-Fin Sodium-to-Air Heat Exchanger for Sodium-Cooled Fast Reactors

Shell and tube-type crossflow heat exchangers with circular fins are widely used in various industries, including nuclear power plants. This study focuses on the sodium-to-air heat exchanger, which is one of the key safety features in sodium-cooled fast reactors. Tube alignment inside the heat exchanger is important because it directly determines the performance. Although heat exchangers are generally designed to have staggered tube alignment, inevitable inline-aligned zones exist. Therefore, this paper proposes a hybrid tube alignment modeling approach that considers both staggered and inline tube heat transfer phenomena. The results of the hybrid model calculations are verified and validated with liquid sodium experiments. The hybrid approach to the tube arrangement reduced the temperature deviation between experimental and calculated values to a difference of 4.55% and 7.38% for both sodium and air sides, respectively, while for the heat transfer, the difference was 15.12% and 9.06% for sodium and air sides, respectively. The results of this study can also be used as a basis for the safety evaluation of nuclear reactors and licensing processes for sodium-cooled fast reactors. In addition, this study is limited not only to sodium heat exchangers but also to any serpentine tube arrangement or crossflow heat exchanger under high-temperature systems, such as concentrated solar power and thermal energy storage industries.

Heat Transfer and Flow Resistance in Crossflow over Corrugated Tube Banks

The engineering of tubes with surface corrugations is recognized as an effective method for enhancing heat transfer within the tube. Yet the impact of surface corrugation on the flow and heat transfer around the tube’s exterior remains inadequately explored. This study investigates the crossflow and heat transfer characteristics in banks of periodically inward-corrugated tubes using computational fluid dynamics. Numerical simulations were performed for both in-line and staggered tube arrangements, covering Reynolds numbers from 1000 to 10,000. The aim was to examine how various corrugation parameters affect heat transfer and flow dynamics in tube banks configured in both in-line and staggered layouts. The results show that the heat transfer and the pressure drop in crossflow across tube banks are substantially influenced by changes in corrugation parameters. Specifically, in the in-line arrangement, both the Nusselt number and Euler number decrease significantly as the corrugation height increases. In contrast, in the staggered arrangement, the Nusselt number and Euler number exhibit less variation in response to surface corrugation. A comparative analysis of performance criteria suggests that a staggered arrangement is more advantageous for improving thermal–hydraulic efficiency in crossflow through corrugated tube banks.

Gas-particle flow induced erosion of economizer in low-low temperature electrostatic precipitators: Numerical prediction and engineering application

In this work, the gas-particle flow and the induced erosion in the economizer region in low-low temperature electrostatic precipitator were investigated by CFD-DPM-EPM coupling approach. The results show that positioning the economizer on the vertical flue or employing a vertical tubes arrangement for the heat exchange tubes, utilizing a small expansion angle (less than 35°) in the expansion section, ensuring a more uniform distribution of inlet gas velocity and dust concentration, and incorporating short and densely positioned guide plates in the expansion section can effectively reduce erosion in the low-temperature economizer. The above results were applied to the economizer equipped with the low-low temperature electrostatic precipitator of a 1000 MW unit in a certain power plant, and the wear situation was significantly improved. The research findings can serve as a reference for diagnosing and analyzing erosion phenomena in low-temperature economizer, and can guide the improvement design to prevent erosion.

Energy and exergy analysis of a laboratory-scale latent heat thermal energy storage (LTES) using salt-hydrate in a staggered tube arrangement

The energy and exergy analyses were performed for a laboratory-scale latent heat thermal energy storage (LTES) using hexahydrate calcium chloride (CC6) as phase change material (PCM) in a staggered tube array configuration, placed horizontally. The PCM melting and solidification process within the tube array was investigated by performing a numerical analysis using transient two-dimensional Navier-Stokes equations and Realizable k-ɛ turbulence model to predict flow and heat transfer. The enthalpy-porosity technique was applied to model PCM melting and solidification. The accuracy of the numerical model was validated against experimentally obtained data where the numerically predicted and measured air temperature at the tube array outlet and PCM temperatures were compared. Additionally, the pressure drop in the array and the average peripheral heat transfer coefficient calculated from the numerical results were compared to the well-known Zukauskas correlation (Zu). The results show that the melting and solidification process of PCM in the tubes of the array is asymmetric in nature, with the PCM melting taking slightly longer compared to the solidification process. It was also observed that the energy quantity was higher compared to the exergy quantity, as exergy considers entropy generation and accounts for irreversibility within the system.

A comparative study of latent heat thermal energy storage (LTES) system using cylindrical and elliptical tubes in a staggered tube arrangement

Numerical analysis was performed to compare the thermal and hydraulic performance of the elliptical and circular tube geometries in the prototype-scale latent heat thermal energy storage (LTES) system. A staggered tube array configuration was used for the analysis where the tubes were placed horizontally. Commercial grade hexahydrate calcium chloride (CC6) was selected as a phase change material (PCM) due to its phase change occurring at room temperature. The study included a numerical analysis of the melting and solidification processes of the PCM within the tube array for both tube shapes, employing transient two-dimensional Navier-Stokes equations and a Realizable k-ɛ turbulence model to predict fluid flow and heat transfer. The enthalpy-porosity technique was used to model PCM melting and solidification. Numerical predictions indicate that the thermal performance for both tube shapes is almost indistinguishable during the melting and freezing processes. However, due to the aerodynamic shape of the elliptical tube, the pressure drop across the horizontal elliptical tube array is approximately 80% lower compared to that of the circular geometry. This reduced pressure drop implies that less pumping power will be required to achieve the desired flow rate across the tube bank, leading to economic advantages for the horizontal elliptical tube array. The proposed design can be used as a dry cooling technique employing an Air Cooled Condenser (ACC) in a thermal power plant.

3-D numerical simulation of the heat transfer of a fluidized bed with a horizontal tube bundle and Geldart D particles

In the present study, a numerical simulation is performed to analyse hydrodynamic and heat transfer of a fluidized bed in a vertical channel. As a novelty, MP−PIC method is applied to 3-D tube bundles immersed in a fluidized bed with Geldart D particles. The main results are compared and validated using the experimental results published in the literature.In both tube bundle distributions, the lowest heat transfer coefficients were obtained in the top region of the tube, which represents approximately 58% of the time average heat transfer coefficient of the surface tube. This behaviour differs at the bottom and sides, where particles are continuously being replaced by other particles, resulting in low particle volume fractions and higher heat transfer coefficients.Analysing each tube arrangement for the cases with the same gas velocity and particle diameter, the results numerically obtained were consistent with the experimental findings. The present study found that the time average heat transfer coefficient for the staggered arrangement was approximately 6%, 5% and 1.6% higher than that in-line, for the particle diameter of 1400, 1600 and 1850 μm, respectively. Some discrepancies can be highlighted when comparing the experimentally and numerically obtained time average heat transfer coefficients, with maximum differences close to 18%, which correspond to the cases with the highest gas velocity and particle diameter (1.71 m/s, 1850 μm).

Numerical study of the influence of amplitudes on heat transfer in a tube bundle

The objective of this study is to investigate the impact of different surface roughness levels on a staggered arrangement of tubes in a cross-flow configuration, with water as the fluid being used. The focus lies in comparing the data obtained from the rough surface configuration with that of a smooth cylinder reference point. To assist this comparison, a comprehensive two-dimensional computational fluid dynamics (CFD) model is created, which accurately represents the distinctive characteristics of each surface shape. This study also included modifying the Remax within a range of 10 000–16 000 and analyzing the outcomes of using four different tube types, each with different supernatant thicknesses labeled as [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] accordingly. Surprisingly, the tube with a 0.4 wave surface had significantly higher average Nusselt numbers (Nu) compared to the other tubes, indicating superior performance. The ideal tube design was found based on three main metrics: The performance evaluation criterion (PEC), the global performance criterion (GPC) and the average Nu. The performance metrics encompassed the PEC, GPC and the Colburn factor [Formula: see text]. The average Nu of the wavy_0.4 tube was higher than that of the SM by 31.66–32.54%, higher than that of the wavy_0.2 tube by 19.76–20.74%, and higher than that of the wavy_0.1 tube by 9.38–16.58%. According to the statistics, a heat exchanger that cools and has a wave with an amplitude of 0 is the most efficient choice for offshore energy systems. The smooth bundle tube (SBT) demonstrated the most significant increase in GPC, with values of 9.3–12.7% and 20.3–28.3% higher than those of wavy tubes with amplitudes of 0.1 and 0.2, respectively. In addition, correlations for the Nu are given, with results verified using empirical data from Balabani et al.

Review on Factors Affecting Efficiency of Shell and Tube Heat Exchanger

Heat exchanger is one amongst promising thermal device in which heat transfer takes place between hot fluid and cold fluid. Among various classifications of warmth exchangers, the main focus was shown by researchers on indirect contact type compact heat exchangers. Among them the shell and tube device belongs to fluid to fluid type heat transfer device. Main applications of shell and tube device feed device in process industries, refineries, chemical plants and power plants. Usually the analysis of shell and tube heat exchangers are divided into two parts namely shell side and tube side analysis. Shell side analysis is easy and doesn't involve much modification. Whereas the tube side analysis is complex and it's done by varying baffle design and elevation with regard to arrangements of tubes. The most disadvantage of shell and tube device is pressure drop which occur at the end of tubes. To overcome this problem, drilled cylindrical copper block has been introduced to switch the tube part through which the new fluid flows and therefore the cold fluid is circulated through the shell. With this design modification, the effectiveness, mass rate, overall heat transfer co efficient are simulated and analysed.

Thermal hydraulic performance of a tubular heat exchanger with in‐line perforated baffle with shutter type saw tooth turbulator

AbstractThis experimental investigation aimed to analyze the impact of a unique design of swirl generator airflow on the performance of a tubular heat exchanger operating with axial flow. To conduct the experiment, we utilized a custom‐built apparatus containing eight sawtooth air deflectors with differing space height ratios (e/h). These deflectors were oriented in a uniform manner (shutter type) and positioned at various inclination angles. Circular baffle plates, housing these deflectors, were equidistantly spaced at different pitch ratios. The arrangement of tubes within the heat exchanger remained constant throughout the study, while the Reynolds number ranged from 16,000 to 30,000. In addition, a consistent heat flux condition was maintained on the surface of the tubes. The research outcomes indicated that incorporating a deflector baffle plate with an inclination angle of 30°, an e/h ratio of 0.4, and a pitch ratio of 1.2 led to an average increase of 1.36 in the thermal enhancement factor when compared to a heat exchanger lacking a baffle plate, tested under similar conditions.

Prediction of optimal dimensions and arrangements of circular tubes of a fin and tube heat exchanger for an improved thermal-hydraulic performance

In the present work, the thermal-hydraulic performance of a fin and tube compact heat exchanger (FTHE) with different spatial arrangements of tubes and variations of tube diameter is investigated numerically. The three types of spatial arrangement of the tubes, namely inline, staggered row (SR), and staggered column (SC) arrangements, and five different tube diameters starting from Dc = 6.51 mm to Dc = 10.51 mm considered with a constant increment of 1 mm, are investigated for the augmentation of the heat transfer. The entire analysis is conducted under the low inlet velocity ranging from 0.7 m/s to 1.1 m/s. The results indicate that FTHEs (flow-through heat exchangers) have better thermal-hydraulic performance when arranged in staggered column configurations compared to inline and staggered row arrangements. However, it was observed that the pressure drop increased in staggered column arrangements compared to inline and staggered row arrangements. The performance ranking method MOORA is applied to optimize the spatial arrangements of tubes. The study’s findings suggest that the performance of FTHE is better in the case of staggered column arrangements, which offer a fair agreement with performance evaluation criteria (PEC3 = Q/(Pf +Pp )). After achieving the staggered column arrangement as an optimum spatial arrangement of the tubes, the influence of tube diameter on the performance of FTHEs is investigated for this arrangement only. The findings indicate that when the tube diameter is increased, there is a corresponding increase in both the characteristics like heat transfer coefficient and the pressure drop penalty. The performance ranking method MOORA is applied to get an optimum tube diameter, which is cross-checked by the TOPSIS method. Based on PEC3 and two optimization approaches, MOORA and TOPSIS, it is revealed that a larger tube diameter leads to better overall performance of the FTHEs.

Numerical analysis of the heat transfer and pressure drop of a wavy fin and Kammtail tube condenser: An investigative study

The aim of this study was to numerically investigate the factors affecting the air-side performance of an innovative condenser for a domestic refrigerator. Novel condenser with a smooth Kammtail tube form was investigated due to delaying flow separation. For the first time in the literature, the kammtail form was used instead of round or ellipse geometry in a finned tube heat exchanger, and the advantages of this form was demonstrated both experimentally and numerically. This study incorporated design parameters such as air velocity (0.5, 0.7, 1 m/s), number of tube rows (4 or 5), tube arrangement (inline, staggered), fin pitches (5, 7, 10, 5–7, 5–10, 7–10 mm), and fin arrangement (homogeneous or hybrid). The findings indicated that, for identical fin types and fin surface areas, the proposed Kammtail shape of 3 × 6 mm exhibited 19% lower pressure drop and 9% higher heat-transfer coefficient compared to the original circular tube profile. Furthermore, decreasing the fin pitches resulted in a 32.9–97% increase in static pressure drop, while the heat-transfer coefficient decreased by about 4.7–11.7%. The examination of two new designs revealed a marked reduction of 7–20.4% in the static pressure drop, a decline in air flow rate of 30%, an increase in heat transfer of 5.6–12.2%, and a corresponding decrease in the volume of the condenser of 20%. The numerical results of this study are in good agreement with experimental results, with deviations of less than 10%.

Dynamic evaluation of ash deposition behavior and parametric study using an inverse distance weighted interpolation dynamic mesh method

Ash deposition is a critical issue concerning the energy utilization and safety operation of heat exchangers. Efficient dynamic evaluation of deposition morphology and reasonable structural parameters contribute to the deposition prediction and the improvement of deposition resistance. In this work, a transient deposition model is established to investigate the dynamic deposition behavior and comprehensive performance. To realize the real-time update of deposition layer morphology, a simple and easy-to-implement dynamic mesh smoothing method based on inverse distance weighted (IDW) interpolation is proposed and then validated by experiments. The effect of the deposition layer dynamic evolution on the particle impact characteristics and the thermal-hydraulic performance of tube bundles is highlighted. In addition, parametric studies are performed on the tube arrangement to obtain the optimal comprehensive performance design. The results show that the angles and velocities of particles impacting the first tube and downstream tubes present a triangular distribution and a butterfly-shaped spatial distribution, respectively. Due to the guidance of the deposition layer on the trajectory of gas and ash particles, the particle impact region on the windward side is more concentrated when using the dynamic mesh model, and the entrainment of small-sized particles is intensified. Besides, the rise in longitudinal spacing significantly exacerbates the deposition and heat transfer deterioration. According to the comprehensive evaluation, the case at SL /D = 2.5 exhibits a higher deposition resistance and heat transfer performance. These results can provide more realistic predictions and indications in practical thermos-equipment design.

Effects of electronic expansion valve tube arrangement on reduction of two-phase refrigerant throttling noise

The two-phase throttling noise in electronic expansion valves (EEVs) of a multi-split air conditioner may exhibit different intensities due to the variable EEV tube arrangements. The purpose of this study is to experimentally investigate the influence of EEV tube arrangement on the throttling noise, and to find a suitable tube arrangement for noise reduction. A throttling noise testing rig is constructed to investigate the influence of tube arrangement including the inclination angle of inlet tube and the refrigerant flow direction. The test conditions for tube arrangement include an inlet tube inclination angle of 0°–90° as well as the flow direction from tube P (parallel to the valve needle direction) to tube V (vertical to the valve needle direction) and from tube V to tube P; and the test conditions for refrigerant include a mass flow rate of 30–90 kg h−1 and an inlet quality of 0.02–0.4. The experimental results show that, the increase of inlet tube inclination angle may weaken the throttling noise, and the sound pressure level (SPL) of throttling noise is decreased by 20.1 % as the inlet tube inclination angle increases from 0° to 90°; and the refrigerant flow direction from V–P (tube V to tube P) instead of P–V (tube P to tube V) may attenuate the throttling noise. The tube arrangement with inlet tube inclination angle of 90° and flow direction from V–P is suggested for minimizing the throttling noise in multi-split air conditioners.

NuScale-like SMR Model Development and Applied Safety Analyses with the Code Chain Serpent-DYN3D-ATHLET

NuScale is an integral pressurized water reactor (iPWR) operated with light water driven by natural circulation through two helical coil steam generators (HCSGs). This work reports the safety analyses of a boron dilution and steam line break accidental sequences in a developed plant computational model based on the specifications from the Final Safety Analysis Report (FSAR). Multi-physics calculations are performed with the code chain Serpent-DYN3D-ATHLET. A state-of-the-art multi-dimensional vessel topology is developed with ATHLET for the accurate representation of flow and temperature fields, as well as spatial core power distribution. The static calculation results show agreement with the reference values from the FSAR. The boron dilution sequence shows a homogeneous core power excursion by the boron feedback, and the reactor is tripped upon “high pressurizer pressure” signal. During the steam line break sequence, the affected HCSG depressurizes rapidly and the reactor is tripped upon “low main steam pressure” signal. None of the transients violate safety margins. The adopted 3-D vessel modelling approach and applied multi-physics calculations are able to capture both transient physics within the reactor domain, and conclude that symmetric arrangement of the HCSG tubes enhance coolant mixing and prevent a heterogeneous core power excursion.

Meristoderes zmaj sp. n., a new species of Kinorhyncha (Cyclorhagida: Echinoderidae) from the Adriatic Sea

Abstract A new species of the cyclorhagid genus Meristoderes is described. Meristoderes zmaj sp. n. is distinguished from its congeners by its unique arrangement of spines and tubes. It possesses acicular spines on segments 4, 6 and 8 in middorsal position and on segments 6–9 in lateroventral position; and tubes on segment 2 in subdorsal, midlateral and ventrolateral position, on segment 5 in lateroventral position and on segment 10 in laterodorsal position. With the formal description of M. zmaj sp. n., the number of species within the genus is increased to 10. In addition, the appearance of a new species and its accompanying fauna within the North-Eastern Adriatic Sea fauna, extensively studied by Kinorhyncha taxonomists, is discussed.

A PARAMETRIC AND COMPARATIVE STUDY ON BARE-TUBE BANKS AND NEW CAM-SHAPED TUBE BANKS FOR WASTE HEAT RECOVERY APPLICATIONS

The present study numerically examines the effects of tube diameter (12 to 35 mm), arrangement, pitch-to-diameter ratio (1.25 to 2.5), length (300 to 1500 mm), and passage number (1-4 passes) on the thermofluidic characteristics of cross-flow tube bundles. Especially, five new cam-shaped tubes are proposed in comparison with the conventional round tube. The air temperatures at the cold and hot side inlets are kept constant at 25°C and 600°C, respectively. The numerical method is verified by the existing experimental results. The findings show that a cam-shaped tube with an equal diameter (Cam_1818) is a promising tube for tube bundles, which apply in waste heat recovery. Indeed, it can offer the same minimum gap as that of the round tube; however, it improves the total thermal resistance up to about 28% and enhances the heat-transfer rate up to an average of 42.3% compared to that of the round tubes at the same pumping power.

A New Insight into Finding the Efficient and Reliable Number and Arrangement of Tubes inside a Shell and Tube Latent Heat Storage Unit

A New Insight into Finding the Efficient and Reliable Number and Arrangement of Tubes inside a Shell and Tube Latent Heat Storage Unit

Erosion wear analysis of heat exchange surfaces in a falling particle-based concentrating solar power system

Next generation concentrating solar power (CSP) plants that use solid particles as the heat transfer and storage medium provide opportunities for higher temperature operation, higher efficiency, and lower levelized cost. However, falling particles over component material surfaces can cause significant erosion, severely limiting the performance and operational service life of the components. An understanding of the particle erosion wear of heat transfer surfaces is imperative for designing components and operating conditions to minimize wear. Considering a shell-and-tube heat exchanger configuration, this study presents a computational analysis coupling falling particle flow around heat exchanger tubes and particle-scale erosion of the tube surfaces governed by the Finnie model. Several tube arrangements, particle flow and geometric parameters, and tube material parameters are systematically investigated for their effects on the erosion rate spatially and with time. Parameters that influence the erosion depth, the cumulative mass loss rate and the maximum erosion rate are elucidated. The results of the study may be used to help identify locations that experience the most erosion and devise ways for targeted erosion mitigation.

Thermal optimization of inter-stage heat exchangers distribution in a three-stage cascading pulse tube cooler

The cascading pulse tube cooler (CPTC) with a transmission tube has the advantages of high efficiency by energy recovery and high reliability by introducing no extra moving parts to the system and can provide cooling capacity at different cooling temperatures. The efficiency of CPTC still needs further improvement to meet the requirement of superconducting cooling and other applications. As there are 3 heat exchangers (HXs) in each stage of CPTC, it’s essential to analyze the losses inside the HXs and optimize the distribution of HXs in CPTC. In this paper, the numerical simulation is conducted to analyze the temperature distribution and pressure drop of different arrangements of hot-end HX (HHXs) and transmission tubes. Simulation results show that the acoustic loss decreases from 10.36 W to 5.17 W when first stage HHX (HHX I) is eliminated from the original CPTC for the same working condition. Experimental tests of a three-stage CPTC are carried out to verify the optimal distribution of the HHXs, the cooling capacity of the three-stage CPTC increases from 249.6 W (original) to 273.5 W (optimized) at 233 K with an input power of 500 W, and the efficiency is improved by 9.46 %. Moreover, the efficiency of the three-stage CPTC with the optimized distribution of the HHXs is improved by 50.7 % at 233 K when compared with the single-stage PTC. The pressure amplitude at the inlet of each stage also increases. The results verify the optimization method for the distribution of IHXs and further confirm that CPTC improves the efficiency of PTC.

Finite Element Analysis of Combined Energy Piles with Long and Short Heat Exchanger Tubes

To improve the heat exchange effect of energy piles in coastal areas, a new energy pile with a combination of long and short heat exchanger tubes is proposed. This technology combines the characteristics of implanted pile construction and arranges heat exchanger tubes of different lengths inside and outside the precast pipe pile, which can make full use of the geological conditions in coastal areas. Finite element analysis was applied for a project in a deep, soft soil ground to study the effectiveness of the new combined energy pile technology. The influences of the combined heat exchanger tubes and groundwater seepage conditions on the heat transfer and stress state of the energy pile were analyzed. The results show that the deformation and internal force of the pile body are closely related to temperature change. The temperature change is determined by heat transfer, which is closely related to the arrangement of heat exchanger tubes and underground water flow. With the increase of groundwater seepage velocity, the heat taken away by the heat exchanger tubes gradually increases; thus, the heat exchange between the heat exchanger tubes and the pile body decreases. The inner heat exchanger tube of the pile leads to an increase in heat exchange. However, as the length of the inner heat exchanger tube increases from 40 m to 80 m, the heat exchange decreases. The research results provide technical support for further development of the new energy pile technology.