Circular Counterpart Research Articles

The impact of drop-shaped pin-fins on the thermal and hydraulic characteristics of a finned tube

In this study, circular and drop-shaped pin-fins were employed to investigate the influence of pin-fins on the thermal behavior and flow characteristics of finned tubes using a combination of experimental and numerical methods. The configuration of in-line pin-fins was analyzed and compared with that of a smooth tube. The analysis covered Reynolds numbers spanning from Re = 7.03 × 103 to 35.17 × 103. Thermal and hydraulic contours were depicted. Two methodologies were utilized to assess the overall performance. The outcomes demonstrated that the average Nusselt number for the finned tubes equipped with drop and circular pin-fins rose by approximately 50.03%–93.1% and 59.59%–77.08%, respectively, in comparison to the smooth circular tube. Moreover, the drop-shaped pin-fins on the tube displayed a reduced friction factor, leading to a reduction of 1.36%–7.95% in comparison to the circular counterpart. Furthermore, both drop and circular pin-fins on the tubes exhibited approximately 2.93%–54.89% and 7.33%–37.1% higher efficiency, respectively, compared to the smooth tube. Generalized correlations were developed to compute the Nusselt number, friction factor, and effectiveness in relation to the Reynolds number, with the aim of providing guidance for future research and design efforts in heat exchangers incorporating pin-fin tubes. The utilization of tubes featuring drop-shaped pin-fins plays a significant role in energy conservation.

Generation of elliptical perfect optical vortex beams and their propagation in free-space.

We investigate the generation of an elliptical perfect optical vortex (EPOV) beam through the optical Fourier transformation of an elliptical Bessel-Gaussian beam and derive an analytical expression for its complex field amplitude. Our analysis includes the examination of the beam's propagation in free-space and the influence of topological charge on its transmission. The EPOV beam's propagation in free-space can be categorized into non-diffracting and diffracting stages. During the non-diffracting stage, the beam intensity and profile size are effectively preserved over a short transmission distance. Subsequently, in the diffracting stage, the beam profile initially contracts and then expands with a change in the beam intensity. Notably, the impact of topological charge on the beam intensity and profile size varies across different stages of propagation. We compare our results with those of the circular perfect optical vortex beam propagating in free-space, observing that the EPOV beam exhibits non-diffracting behavior for short propagation distances compared to its circular counterpart. The signature of the focusing behavior of the EPOV beam is observed at a relatively small propagation distance compared to the circular case.

An Analysis of Split-Ring Resonators and Potential Barcode Application

This paper presents an analysis of various split-ring resonator (SRR) configurations coupled with coplanar waveguides (CPW). Three distinct resonant structures are presented, namely, the S-shaped split-ring resonator (S-SRR), the conventional split-ring resonator (SRR), and a pair of SRR. Among the examined resonant structures, it is observed that the S-SRR exhibits the smallest electrical size with the corresponding resonant frequency of 1.37 GHz, while the conventional SRR has the largest electrical size with the corresponding resonant frequency of 3.34 GHz. On the other hand, the resonant frequency of a dual SRR is 2.37 GHz. However, the transmission coefficient of a dual SRR is -11.43 dB, which is higher than S-SRR (-10.02 dB) and SRR (-8.18 dB). Furthermore, this study extends the analysis between a square dual SRR and a circular dual SRR with retained area. The square SRR demonstrates a lower resonance frequency (2.23 GHz) relative to its circular counterpart (2.37 GHz). The comparison also shows that the transmission coefficient of the square configuration is -13.88 dB, which is higher than its circular counterpart (-11.43 dB). The realization of a barcode application is achieved by loading multiple S-shaped split ring resonators (S-SRRs) with varying geometric parameters adjacently onto the transmission line. By individually rotating each of these S-SRRs, it becomes possible to alter the notch magnitude, thereby positioning it within a specific designated range corresponding to a particular code. In the case of a configuration involving rotations of (0°, 45°, 90°, 0°, 45°, 90°), this approach results in the creation of a barcode denoted as "100 010 000 100 011 000". This methodology enables the encoding of information in the form of distinctive resonant responses, providing a versatile and compact means of realizing barcode applications.

Experimental Study on Performance of Liquid–Gas Jet Pump with Square Nozzle

An experimental study is conducted to investigate the effects of different operating parameters on the performance of liquid–gas jet pumps. A square nozzle with an area ratio of 2.25 is designed for the liquid–gas jet pump, and an experimental setup for the liquid–gas jet pump system is constructed. By varying parameters such as inlet flow rate, temperature, and inlet pressure, the variations in the pumping capacity and pumping ratio of the system are studied. The performance of liquid–gas jet pumps with square nozzles and traditional circular nozzles under the same working conditions was compared through experimental data. Explore the performance advantages and disadvantages of liquid–gas jet pumps with different shaped nozzles under the same working conditions. The experimental results indicate that as the inlet flow rate of the liquid–gas jet pump increases, the pumping capacity of the system increases, leading to an increase in the pumping ratio. The operational efficiency slightly decreases with a rise in the working water flow rate. The pumping ratio of the system increases with an increase in the inlet pressure, reaching a peak value of around 4.0 when the inlet valve is fully open. Inlet pressure significantly affects the efficiency of the liquid–gas jet pump, with the highest efficiency point achieved at Pa (inlet air pressure) = 60 kPa, reaching an operational efficiency of 42.48%. When Pa exceeds 70 kPa, the operational efficiency rapidly declines. Comparing the performance of square and circular nozzle liquid–gas jet pumps under the same operating conditions, the performance of the square nozzle liquid–gas jet pump outperforms that of the circular nozzle counterpart. The pumping system’s performance decreases continuously with an increase in the working liquid temperature; however, the decline in pumping performance becomes gradual after exceeding 40 °C. As the water level rises, both the pumping capacity and pumping ratio of the system increase. After the liquid level reaches 40 cm, the changes in the pumping system’s performance become less pronounced.

Bolted CHS Flange-Plate Connections under Bending

Most research on circular hollow section (CHS) flange-plate connections deals with axial tension loading, yet bending action is a common load case. Prior researchers have studied both ring and blank-flange-plate connections, using a four-point-bending setup, generating a database of 10 experimental tests and five numerical models on bolted blank-flange-plate connections under pure bending. This limited data is extended herein by two large-scale laboratory tests with blank-flange-plate connections having a large span-to-tube diameter ratio, and 120 numerical models. Flange-plate plastification and bolt fracture are the valid failure modes for this splice, so all data was meticulously assessed to exclude experimental tests or numerical models not governed by connection failure. Existing design models for calculating the connection capacity under pure bending are evaluated and revised. Moreover, based on rectangular flange-plate connections, a novel method is proposed to design its circular counterpart under pure bending. For all methods, the difference in using the ultimate stress for flange-plate moment capacity—instead of the conventional yield stress—is also analyzed. Lastly, a reliability analysis is conducted to support the proposed design method.

Computational evaluation of the effect of femoral component curvature on the mechanical response of the UHMWPE tibial insert in total knee replacement implants

Total knee replacement (TKR) surgery is done on individuals with end-stage osteoarthritis to restore knee function and alleviate joint discomfort. There have been recent developments in the design of customized implants based on patient-specific data obtained from MRI scans and subsequent image processing techniques. Here curvature of the femoral component plays an important role in effective implant design. Therefore, the objective here is to investigate the influence of this curvature of the femoral component on the mechanical response of the bearing component. A 3D finite element knee implant model with a circular and an elliptical femoral component is developed and investigated for gait kinetics and kinematics. Responses such as contact pressure, stresses, strains, and wear produced on the tibial insert are estimated throughout the gait cycle. These findings suggest that the elliptical femoral component generates less contact pressure on the tibial insert than its circular counterpart. It is also inferred that too much variation in this curvature is not recommended as it may affect the patient's comfort level. In addition, the wear of the tibial insert is computed based on the contact pressure created by both knee implant models. Our study suggests an optimum value for the curvature and the comfort level of the patients over the existing knee implant designs.

Aerodynamic noise characteristics of non-circular cylinders in subcritical flow regime

The present study experimentally investigates the aerodynamic noise from the flow around cylinders of square and equilateral triangle cross-sections at different angles of incidence ( α). The cylinder models have a side dimension of 10 mm and a span of 300 mm. The free stream velocity ( U 0) is in the range of 12–36 m/s, and the corresponding Reynolds numbers are 7.8 × 103 to 2.3 × 104, which is in the subcritical flow regime. The characteristic acoustic tones are generated at α = 30° and 45° for square and triangular cylinders. The frequency of acoustic tones linearly increases with the free stream velocity, and the corresponding Strouhal numbers are found to be in the range of 0.13–0.16. Depending on the angle of incidence, the overall sound pressure level is higher than the background noise by 4–24 dB for the square cylinder and 3–15 dB for the triangular cylinder at U 0 = 36 m/s. The highest noise level of the square cylinder is 90 dB at α = 45° and 79 dB at α = 30° for the triangular cylinder. The spectral scaling with the sixth power of the free stream velocity indicates the dipole behaviour of the acoustic tones. The mean and root-mean-square velocity profiles in the wake region characterise the noise emissions at different angles of incidence. The comparative acoustic study of the non-circular cylinders with a circular counterpart showed that the highest noise level is from the square cylinder at α = 45°. The directivity study shows that the noise level of the square cylinder at α = 45° at 90° angular location ( θ) is higher by 6.5 dB than that at θ = 30°.

Freeze-thaw behaviour of basalt fibre reinforced recycled aggregate concrete filled CFRP tube specimens

This paper is focused on the behaviour of basalt fibre reinforced recycled aggregate concrete (BFRC) short specimens confined by carbon fibre reinforced polymer (CFRP) tubes under freeze–thaw conditions. The main parameters investigated are the replacement rate of recycled coarse aggregate (RCA), the number of freeze–thaw cycle (FTC), the related temperature range, and the shape of short specimen section. The failure mode, dynamic elastic modulus, ultimate bearing capacity and the load–strain response of the specimens are studied. The results show that the failure mode and the load–strain response of CFRP tube confined recycled aggregate concrete (RAC) specimen have insignificant change due to FTCs. However, with the increase of the FTCs, the bearing capacity of the specimen decreases, and the specimen with square cross-section is much more sensitive than that of the circular cross-section counterpart. The smaller the range of freeze–thaw temperature changed, the smaller loss of the dynamic modulus and the smaller decrease range of the ultimate bearing capacity after FTCs.

Mixing Enhancement of Inverse Jet Flame with Circumferential Fuel Ports

ABSTRACT Despite more than a decade-long effort to understand the flow structure in Inverse Jet flame (IJF) configuration, the performance enhancements on such configurations are sparsely investigated. A passive technique to improve the air-fuel entrainment in IJF configuration is implemented in this study by altering the central-air port geometry with an elliptical port. The flow and mixing characteristics are studied using a three-dimensional Favre-averaged method for the elliptical central air-port IJF compared to its circular counterpart. The numerical model is validated using the standard k-ε turbulence model to capture the complex flow physics and comprehend the mixing characteristics of IJF in this burner configuration. The elliptical central port brought the differences in the spreading and entrainment rates. The present work emphasizes flow dynamics and mixing characteristics, including the features of the recirculation zone, turbulence kinetic energy, and velocity distribution. The (omega) Ω vortex identification method and turbulent kinetic energy distribution provided more profound insights into the role of vortex structures on air-fuel mixing. The vortex structures are prominent in the novel elliptical port IJF compared to the circular counterpart, thus affecting the flame structure. The vortex strength Ω was found to be 0.94 in elliptical IJF and 0.88 for the circular central port IJF. This work further quantifies the enhanced air-fuel mixing as observed with the elliptical inverse jet diffusion flame based on mixture fraction mixing index, which can be applied to any IJF configurations. The mixing index at the axis switching location was greater than 80% for the elliptical IJF compared to 45% in the circular IJF configuration.

Effects of circular and non-circular nozzle exit geometries on subsonic and supersonic jet propagations

The mixing enhancement and core length reduction of a jet without significant loss of thrust are essential for reducing infrared radiation, mitigating aeroacoustic noise, improving combustion characteristics, and thrust vectoring. The jet mixing can be improved by manipulating the flow behavior. In subsonic and sonic jets, the flow manipulation may be achieved by utilizing nozzles with non-circular geometries that shed vortices of varying size due to their non-uniform azimuth curvatures. Non-uniform vortices generate differential spreading along the nozzle’s perimeter, causing axis switching and improving entrainment characteristics. Therefore, the present study examines the effects of two non-circular nozzle exit shapes (elliptic and square) on the mixing augmenting efficacy at subsonic and sonic flow conditions. The circular nozzle is tested for comparison. Both quantitative and qualitative analyses evaluate the efficacy of nozzles with non-circular exit geometries. Among the configurations investigated, the elliptic nozzle is superior in shortening the potential core length and enhancing the jet spread. A maximum reduction of 18.75% in core length with rapid jet decay was accomplished with the elliptic nozzle. The measurement of pressure profiles at different streamwise locations reveals that the spread rate is greater for elliptic and square jets than their circular counterpart. The elliptic jet exhibits the highest spread along the minor-axis direction compared to the major-axis direction. The differential jet spread rate in the elliptical jet causes an early axis-switching––direct evidence of mixing augmentation. Shadowgraph images show the asymmetric pattern of shock cell structures and differential spreading in elliptic and square jets.

Energy-absorbing characteristics of hollow-cylindrical hierarchical honeycomb composite tubes inspired a beetle forewing

This paper investigates the superior energy-absorbing characteristics of hollow-cylindrical-joint hierarchical honeycomb composite tubes under axial quasi-static crushing. Biomimetic multi-cell tubes (BMCTs), inspired by the forewing of a beetle, were manufactured using the vacuum bag moulding method. Quasi-static compression tests were conducted to characterize the force–displacement response, the progression of failure, the crashworthiness characteristics, and the corresponding energy absorbing mechanisms. The experimental results show that the fiber orientation (α) has a significant effect on the energy-absorbing characteristics of these structures. The crush load efficiency (CLE) and specific energy absorption (SEA) tend to initially decrease and then increase with increasing α. It has also shown that the SEA of the BMCTs can be significantly affected by employing different fiber orientations. The highest SEA value measured on these structures, 77.3 J/g, is more than double of 34.9 J/g measured on the single circular tube counterpart. The energy-absorbing capacity of the composite structures is devisable and can be enhanced by integrated biomimetic design.

Tracking down the origin of superbubbles and supergiant shells in the Magellanic Clouds with Minkowski tensor analysis

Aims.We develop an automatic bubble-recognition routine based on Minkowski functionals (MF) and tensors (MT) to detect bubble-like interstellar structures in optical emission line images.Methods.Minkowski functionals and MT are powerful mathematical tools for parameterizing the shapes of bodies. Using the papaya2-library, we created maps of the desired MF or MT of structures at a given window size. We used maps of the irreducible MTψ2, which is sensitive to elongation, to find filamentary regions in Hα, [S II], and [O III] images of the Magellanic Cloud Emission Line Survey. Using the phase ofψ2, we were able to draw lines perpendicular to each filament and thus obtain line-density maps. This allowed us to find the center of a bubble-like structure and to detect structures at different window sizes.Results.The detected bubbles in all bands are spatially correlated to the distribution of massive stars, showing that we indeed detect interstellar bubbles without large spatial bias. Eighteen out of 59 supernova remnants in the Large Magellanic Cloud (LMC) and 13 out of 20 superbubbles are detected in at least one wavelength. The lack of detection is mostly due to surrounding emission that disturbs the detection, a too small size, or the lack of a (circular) counterpart in our emission line images. In line-density maps at larger scales, maxima can be found in regions with high star formation in the past, often inside supergiant shells (SGS). In SGS LMC 2, there is a maximum west of the shell where a collision of large gas clouds is thought to have occurred. In the Small Magellanic Cloud (SMC), bubble detection is impaired by the more complex projected structure of the galaxy. Line maps at large scales show large filaments in the SMC in a north-south direction, especially in the [S II] image. The origin of these filaments is unknown.

Porcine model elucidates function of p53 isoform in carcinogenesis and reveals novel circTP53 RNA

Recent years have seen an increasing number of genetically engineered pig models of human diseases including cancer. We previously generated pigs with a modified TP53 allele that carries a Cre-removable transcriptional stop signal in intron 1, and an oncogenic mutation TP53R167H (orthologous to human TP53R175H) in exon 5. Pigs with the unrecombined mutant allele (flTP53R167H) develop mainly osteosarcoma but also nephroblastomas and lymphomas. This observation suggested that TP53 gene dysfunction is itself the key initiator of bone tumorigenesis, but raises the question which aspects of the TP53 regulation lead to the development of such a narrow tumour spectrum. Molecular analysis of p53 revealed the presence of two internal TP53 promoters (Pint and P2) equivalent to those found in human. Consequently, both pig and human express TP53 isoforms. Data presented here strongly suggest that P2-driven expression of the mutant R167H-Δ152p53 isoform (equivalent to the human R175H-Δ160p53 isoform) and its circular counterpart circTP53 determine the tumour spectrum and play a critical role in the malignant transformation in flTP53R167H pigs. The detection of Δ152p53 isoform mRNA in serum is indicative of tumorigenesis. Furthermore, we showed a tissue-specific p53-dependent deregulation of the p63 and p73 isoforms in these tumours. This study highlights important species-specific differences in the transcriptional regulation of TP53. Considering the similarities of TP53 regulation between pig and human, these observations provide useful pointers for further investigation into isoform function including the novel circTP53 in both the pig model and human patients.

A sectorial scheme of gate-all-around field effect transistor with improved electrical characteristics

Reliability and controllability for a new scheme of gate-all-around field effect transistor (GAA-FET) with a silicon channel utilizing a sectorial cross section is evaluated in terms of Ion/Ioff current ratio, transconductance, subthreshold slope, threshold voltage roll-off, and drain induced barrier lowering (DIBL). In addition, the scaling behavior of electronic figures of merit is comprehensively studied with the aid of physical simulations. The electrical characteristic of proposed structure is compared with a circular GAA-FET, which is previously calibrated with an IBM sample at the 22 nm channel length using 3D-TCAD simulations. Our simulation results show that sectorial cross section GAA-FET is a superior structure for controlling short channel effects (SCEs) and to obtain better performance compared to conventional circular cross section counterpart.

Efficiency Enhancement in a Wireless Power Transmission System Using Parasitic Components

In this paper, we present a rigorous optimization method to design a wireless power transmission (WPT) system. In order to enhance the power received by the receiver, parasitic components are integrated into the system. Our analysis shows that a system with square parasitic wire actually gives better performance than its circular counterpart. From our results, it can be seen that the presence of square parasitic wires in the system improves considerably the efficiencies, as well as the distance of effective power transfer. By implementing two square parasitic wires and using an optimization algorithm to carefully select the positions of the receiving antennas, we show that power coupled to one receiver can be significantly enhanced; while the other suppressed – the peak power at the receiving antenna is improved to 15.7% and the power detected by the adjacent antenna is minimized to as low as 2.6%. This result is important as it shows that the parasitic components do not only enhance the power coupled to the receiving antenna, it also effectively reduces crosstalk in adjacent antennas. Indeed, it can be observed that the peak efficiency obtained using two parasitic wires (with the transmitter sandwiched in between the two wires) is almost twice of that using a single wire.

Stability analysis of the wake-induced vibration of tandem circular and square cylinders

We present a stability analysis to investigate the underlying fluid–structure modes during transverse wake-induced vibration (WIV) of an elastically mounted downstream cylinder in a tandem arrangement at low Reynolds number. The upstream cylinder with an equal diameter is kept stationary, whereas the downstream cylinder in the tandem arrangement is free to vibrate in the transverse direction. The WIV involves complex interaction dynamics of the upstream wake with the freely vibrating downstream cylinder, which leads to a relatively large transverse force and vibration in the post-lock-in region. We consider a data-driven model reduction approach to construct an eigenvalue representation of WIV system and perform the stability analysis to examine the underlying process of WIV for the tandem circular and square cylinders. The model reduction of the fluid system is constructed by the eigensystem realization algorithm (ERA) and coupled with a transversely vibrating bluff body in a state-space format. Unlike the wake-oscillator model, the ERA-based ROM does not rely on any empirical formulation and captures naturally the essential linear fluid dynamics through the solution of the Navier–Stokes equations. Results show that the WIV region and the onset reduced velocity can be predicted accurately by tracing the eigenvalue trajectories of the ERA-based low-dimensional model for a range of reduced velocities. The stability analysis reveals that there exists a persistently unstable eigenvalue branch that sustains WIV, which also implies that the highly nonlinear behavior of WIV has its linear origin. The sharp corner of the square cylinder is found to have the stabilizing effects, namely (i) the reduced velocity for the WIV onset is larger than its circular cylinder counterpart, (ii) the transverse response amplitude and the lift force are consistently lesser in both lock-in and post-lock-in regimes for the square cylinder configuration. This work has a potential impact on the development of control strategies for reducing undesired vibrations and loads in flexible structures undergoing wake interference effects.

Modal Analysis of Corrugated Plasmonic Rods for the Study of Field Localization, Conductor Attenuation, and Dielectric Losses

By virtue of the strong confinement of surface-wave fields that it provides, the transverse corrugated conducting rod is an important structure in the fields of plasmonics and metasurfaces, finding applications in focusing, sensing, imaging, spectroscopy, and subwavelength optics, among others. This paper presents an analytical modal method for treating such grated rods with generally dielectric-filled grooves, one which offers rapid yet accurate surface-wave modal solutions. Based on the asymptotic corrugation boundary conditions, the formulation is simple and elegant, providing not only the dispersion relationship between the frequency and wavenumber but also the explicit functional forms of the fields. Dispersion and modal field results obtained by the proposed method are validated with an independent full-wave solver. Because of its candidacy for microwave applications at high powers and high frequencies, as well as transmissions over long distances, studies of dielectric and conductor losses are also carried out, for both the grooved rod and its likewise corrugated circular waveguide counterpart. Parametric studies are conducted on three aspects, namely, the degree of field localization on the surface of the rod, as well as attenuation due to dielectric and metal losses. Measurements of dispersion and field decay properties conducted on a manufactured rod that concur with theory are also reported.

Effect of aspect ratio on heat transfer enhancement in alternating oval double pipe heat exchangers

In this paper, a numerical study for laminar, incompressible flow for alternating oval double pipes is carried out in order to analyze the suggested configuration under different conditions. In addition to Reynolds number, the effect of pipe aspect ratio, as one of the significant non-dimensional variables on thermal performance is analyzed quantitatively. The results show that in all aspect ratios, heat transfer rate accepts higher values comparing to circular counterpart. However, it is not considered as oval double pipes are always worth taking the place of circular types, since the pressure loss effects may be dominant over the heat transfer improvement. For this purpose, Enhancement ratio (ER) is investigated as a function of aspect ratio (γ) and Reynolds number (Re). It is revealed that, at a specific Reynolds number, ER increases with aspect ratio until it reaches a max value, then starts declining. Therefore, to determine whether using this configuration is economically justified or not, a map for ER in terms of mentioned parameters is given. It is revealed that in particular pairs of (γ,Re), the ER>1 condition can be achieved. It is also found that the region of ER>1 becomes more limited at extreme values of aspect ratio resulting in an optimum value for each Reynolds ratio. In addition, for Reynolds values less than 600, ER is always less than one regardless of aspect ratio value. In the end, mathematical expressions for the extreme values of γ that result in higher than one values of ER is suggested.

Mode instability in ytterbium-doped non-circular fibers.

We present a theoretical study of transverse mode instability (TMI) in non-circular ytterbium-doped fibers including the rectangular core in a circular or D-shaped cladding. The D-shaped cladding is found efficient to suppress the TMI thanks to better heat dissipation, as compared to the circular cladding. However, the rectangular core does not suppress the TMI despite its better heat dissipation than a circular core counterpart. Although the temperature built in the rectangular core decreases with an increasing aspect ratio of the rectangular core, the low temperature does not benefit the TMI suppression. Instead, the TMI becomes stronger than its circular core counterpart. Our study reveals that the power coupling between two involved modes and gain saturation effect play a significant role in influencing the TMI. The power coupling strength is associated with the frequency offset between two modes, and it grows with an increasing aspect ratio of rectangular cores, suggesting the longer axis of rectangular core promotes the TMI.

Numerical investigation of heat transfer and entropy generation of laminar flow in helical tubes with various cross sections

This study evaluates heat transfer performance and entropy generation of laminar flow in coiled tubes with various cross-sections geometries i.e. circular, ellipse and square, relatives to the straight tubes of similar cross-sections. A computational fluid dynamics model is developed and validated against empirical correlations. Good agreement is obtained within range of Reynolds and Dean numbers considered. Effect of geometry, wall temperature, Reynolds number and heating/cooling mode were examined. To evaluate the heat transfer performance of the coiled tube configurations, a parameter referred as Figure of Merit (FoM) is defined as the ratio heat transfer rate to the required pumping power. In addition, exergy analysis is carried out to examine the inefficiency of the coiled tube configurations. The results indicate that coiled tubes provide higher heat transfer rate. In addition, it was found to be more efficient as reflected by lower entropy generation as compared to straight tubes. Among the studied cross-section, square cross-section generates the highest entropy, followed by ellipse and circular counterpart. Entropy production from heat transfer contribution is two order-of-magnitude higher than that of entropy contribution from viscous dissipation. Cooling case produces slightly higher entropy than heating counterpart. Finally, this study can provide practical guideline to design more efficient coiled heat exchanger.