Pressure Loss Penalty Research Articles

Numerical Study of Thermal Performance on Fin and Tube Heat Exchanger with Flat Rectangular and Sinusoidal Winglet Vortex Generators

Generation of vortices in the fin and tube heat exchanger is one of the common methods to reduce the air-side thermal resistance. This study deals with the enhancement of heat transfer in the air side using conventional rectangular and sinusoidal sine wave vortex generators. The vortex generators are placed in the downstream location of the tube in the common flow-down configurations and the range of Reynolds number is maintained about 400 to 1100. The results of the above vortex generators are compared with baseline configuration based on thermos-hydraulic criterion parameters like variation in the flow structure, variation in the temperature distribution, variation in the pressure distribution, variation in the friction factor, and overall thermal enhancement factor. Based on the comparative numerical analysis, sinusoidal and conventional rectangular winglet shows good heat transfer enhancement in that they have a large pressure loss penalty.

Effect of truncated pin-fins on flow and heat transfer characteristics with impinging jets on a concave surface

The double-wall cooling system containing jet impingement and full-length pin-in cooling structures shows good performance in heat transfer enhancement and uniformity, which has-been used in the blade cooling design. However, the pressure loss induced by the full-length pin-fin is relatively high. It is very meaningful to get a cooling type which can balance the heat transfer performance of double-wall cooling and flow resistance, especially for the blade leading edge. In this study, numerical simulations have been carried out to study the influences of truncated pin-fins height and arrangement on heat transfer increment and flow behavior of jets impinging onto a concave double wall channel with varying truncated pin-fins arranged, considering the heat transfer enhancement potential and relatively weaken pressure loss penalty of truncated/broken pin-fin. Jets impingement on a smooth-concave surface is regarded as Baseline. Streamlines in two-dimensional sections in the channel and limiting streamlines near the target wall conjugated with flow characteristics figures are applied to better understand the flow structures in the channel. The local and averaged heat transfer performance is analyzed based on the flow discussions. The overall parameters, i.e., thermal performance, friction factor and pumping power, are also obtained. The results show that the introduction of relatively high truncated pin-fins located on the upper wall presents higher heat transfer enhancement and lower pressure loss comparing with the full-length case and truncated pin-fins located on pressure loss comparing with the full-length case and truncated pin-fins located on target wall cases. The truncated pin-fins placed on the upper surface with relative height of 0.75 reaches the highest overall thermal performance and uniformity in this work.

Numerical analysis and experiments on heat transfer and flow structures in rotating three-pass serpentine channels with ribs, guide vanes and trailing bleed holes

Numerical and experimental studies are conducted on heat transfer and pressure loss in a three-pass serpentine channel with trailing bleed holes. The guide vanes' effects in the smooth and ribbed channels are studied comparatively. Based on the hydraulic diameter and inlet velocity, the Reynolds number ranges from Re = 14,000 to Re = 100,000, and the rotation number ranges from Ro = 0 to Ro = 0.1. Through the numerical simulations, the rib configuration in serpentine channels influences the guide vane's flow control effects. Applying the guide vanes in the ribbed serpentine channel's tip bend region enhances the flow impingement and advection, increasing the total Nusselt number in the blade-tip region by about 25%, and this region's heat transfer uniformity is improved as well under non-rotating and rotating conditions without additional pressure loss penalty in the channel. Moreover, it is a promising method to improve the turning flow structures and enhance heat transfer further in the ribbed serpentine channel by applying the tandem guide vane in the tip bend region. Both the numerical computations and experiments show only slightly higher and more uniform heat transfer in the second and third passages after applying the guide vanes in the bend regions under non-rotating and rotating conditions. The experiments indicate that the rotation effects show a more appreciable influence on the heat transfer enhancement values along the serpentine channel than the channel Reynolds numbers. The heat transfer differences between the leading and trailing sides are 15.4%, 14.0%, and 21.3% in the three passages, respectively, at Re = 14,000 and Ro = 0.1, referring to the averaged Nusselt number in each passage. The CFD results demonstrate that the rotation significantly improves the heat transfer in the third passage by promoting more radial outflow through the tip hole, reducing the flow rates through the lateral bleed holes by about 13.2%.

Numerical and experimental thermohydraulic performance evaluation of multi-minichannel heat sinks considering channel structure modification

Heat transfer and fluid flow behaviour have been studied numerically and experimentally in multi-mini channel heat sinks (MM-CHS). The proposed designs of MM-CHS are utilizing more than one passive technique in order to enhance the thermohydraulic performance with different inlet/outlet arrangements. Three curved channels have been considered including (arc, S, and wave) combined with two passive techniques of interruptions and ribs–cavities. Numerical simulations are performed on laminar water flow for the considered Reynolds number less than 500. In the experiment, four MM-CHSs with different channel structures that include straight channels, wave channels, wave channels with interruptions and wave channels with ribs–cavities are manufactured and tested to validate the simulation model and compare the performance improvement of the MM-CHS resulting from the adoption of both proposed techniques. Results show an effective improvement in the performance of the MM-CHS after using interruptions and ribs–cavities but with the pressure loss penalty. Compared with the interrupted curve channel, a ribbed curved channel with cavities is more effective in improving wall temperature uniformity along the channel length of MM-CHS. The best thermohydraulic performance is achieved by the wave channel with ribs and cavities, where the performance evaluation criterion reached about 1.68.

Heat Transfer Enhancement of Microchannel with Jets and Ribs

In this paper, we propose a new microchannel heat sink with ribs and jets, which can not only increase the heat transfer performance but also improve the fluid flow in the microchannel. The effects of different shapes of ribs and inlet aspect ratios on the performance evaluation criteria at various Reynolds numbers are discussed. At an inlet Reynolds number of 3000, the maximum temperature of the modified microchannel heat sink is 8.78% lower than that of the smooth microchannel, and the performance evaluation criteria is increased by 0.94. Under the same conditions, the bottom plate temperature difference of the hydrofoil rib microchannel jets is 3.4% lower than that of the cylindrical rib microchannel jets; and the triangular-shaped ribs increase the heat transfer and cause greater pressure loss penalty due to the formation of a larger swirl zone in the back area. The jet inlet parameters can effectively improve the heat transfer coefficient of the microchannel. In terms of the heat transfer capability and the uniformity of the bottom plate temperature, the hydrofoil rib microchannel with jets has the best heat dissipation effect when the jet inlet parameter is .

Experimental study on condensation heat transfer and pressure drop characteristics of R32 flowing inside an alternating cross-section flattened tube

This work presents the experimental study of two-phase flow inside an alternating cross-section flattened (ACF) tube. The ACF tube was made from a copper circular tube with an inner diameter of 4.31 mm. We conducted the test under the following experimental conditions: a mass flux of 280, 430, and 580 kg/m2s; a saturation temperature of 40, 45, and 50 °C; a heat flux of 10, 15, and 20 kW/m2; and an average vapor quality of 0.1–0.8. Compared to the existing flow pattern maps, most fell into the annular and semi-annular flow regimes. However, the results were found in the transition and intermittent flow regions at low vapor quality. The results from the circular and ACF tubes were examined and discussed. We found that the ACF tube revealed a prominent condensation heat transfer coefficient and a reasonable pressure loss penalty. The heat transfer coefficient and frictional pressure drop of the ACF tube were higher than that of the circular tube by approximately 25.6–111.1% and 4.3–39.9%, respectively. New correlations for the Nusselt number and two-phase friction factor were proposed.

Numerical investigations of turbulent heat transfer enhancement in circular tubes via modified internal profiles

Convective heat transfer enhancement in turbulent pipe flows via patterned surface textures is studied numerically via large eddy simulation (LES). The Reynolds and Prandtl numbers of the flow are 90,000 and 0.836, respectively. The patterned surface textures consist of ellipsoidal inward-facing elements, a wire coil, and spiral corrugations. The governing equations are solved on three-dimensional grids with the finite volume method using second-order temporal and spatial schemes. The mean Nusselt number and friction factor are calculated in each textured pipe and compared to an untextured baseline configuration. The inward-facing ellipsoidal elements showed the best performance yielding 22 − 42 % heat transfer enhancement with 41 − 97 % pressure loss penalty. The mechanisms driving convective heat transfer enhancement are examined via order-of-magnitude analysis of the first and second laws of thermodynamics. An effective convective mixing parameter is defined to reflect the interplay between the radial turbulence and local thermal gradients. The best enhancement technique yields 46% larger effective convective mixing with 26% lower turbulent kinetic energy compared to the least efficient case. The analysis shows that high heat transfer enhancement is promoted by inducing strong radial turbulent fluctuations in high-temperature-gradient regions while keeping other regions undisturbed. • Heat transfer enhancement via surface textures is studied via large eddy simulation. • Inward ellipsoids yield 22% higher heat transfer rate and 41% larger pressure drop. • The process driving heat transfer enhancement is explained via total energy budgets. • Near-wall radial fluctuations contribute the most towards enhancing heat transfer. • Axial vortices yield the best heat transfer enhancement and low entropy generation.

Experimental Investigation of Thermal Performance of a Novel Alternating Cross-Section Flattened Tube Heat Exchanger

The air-side performance of a novel alternating cross-section flattened (ACF) tube heat exchanger was experimentally investigated. Three heat exchangers with an in-line tube arrangement and two tube rows were used as the test sections. The tube configuration is the highlight of the research work. ACF tubes with hydraulic diameters of 4.16, 4.75, and 5.20 mm were assembled as the heat exchanger. The experimental results showed that the ACF tube heat exchangers exhibited a prominent heat transfer characteristic with a reasonable pressure loss penalty. Performance evaluation criteria, as a nondimensional parameter, were employed to assess the heat exchanger performance. Finally, the j and f of the ACF tube heat exchanger were compared with those obtained from various shapes of noncircular tube and fin tube heat exchangers. All the details are examined and discussed in this study.

Numerical investigation of pentagonal V-shape ribs to enhance heat transfer in hydrogen rocket engine cooling channels

Keeping the combustion chamber walls at a sufficiently low temperature ensures liquid rocket engines' safe and reliable operation. The most promising method to achieve that is the heat transfer enhancement techniques which optimize the heat transfer coefficient and increase the thermo-hydraulic performance. The present work is concerned with numerical studies on the effect of the pentagonal V-shape ribs to enhance the heat transfer coefficient of the rocket engine's cooling channels. Numerical simulations for various chamfering angels of the pentagonal V-shape rib are performed by the (SST,k−ω) turbulent model. The simulation findings show that the overall performance of the ribbed channel improved inversely with the pentagonal chamfering angle. Compared with a conventional channel, the average Nusselt Number and thermal-hydraulic performance of the ribbed channel enhanced up to 66.6% and 52% respectively, and the 5° pentagonal V-shape rib has higher thermal-hydraulic performance with a slight high the pressure loss penalty.

Numerical study on influence of water based hybrid nanofluid and porous media on heat transfer and pressure loss

The performance augmentation of the heat exchangers is a deal between heat transfer improvement and pressure loss penalty. There is no study investigating this deal as the thermal performance index of the heat exchangers filled by hybrid nanofluid and porous media. The thermophysical properties of TiO2–Al2O3/water are available in the literature, but no study is dedicated to evaluating the flow characteristics of such a hybrid nanofluid, especially in a porous material. This paper is intended to explore the heat transfer and pressure loss of a turbulent convective flow of hybrid nanofluid (TiO2–Al2O3/water) and porous media in a double-pipe heat exchanger with a counter flow. Hot water flows in an annular pipe to warm cold nanofluid flow in an inner pipe. The effect of two porous media is examined for inserting in the inner pipe. Hybrid nanofluid increases the heat transfer (maximum 6%) and pressure loss (maximum 11%). The thermal performance index of the hybrid nanofluid in the aluminum porous media is less than 0.6, while this for the copper media is more than 1. Correlations for the calculations of the Nusselt number and friction factor of the turbulent hybrid nanofluid flow in porous media are missing in the literature. So, for the first time, equations were proposed for finding the Nusselt number and friction factor of the hybrid nanofluid in both empty and porous pipes.

Experimental investigation of heat transfer enhancement and pressure drop of fin-and-circular tube heat exchangers with modified rectangular winglet vortex generator

The presence of vortices in a flow field significantly impacts heat transmission. The effect of a modified rectangular winglet vortex generator on heat transfer and pressure drop performance for a fin-tube heat exchanger (FTHE) is experimentally explored in this work. Design and fabrication of full-scale prototype of an FTHE are carried out. Two types of rectangular winglet vortex generators (RWVGs), i.e., Flat RWVG and RWVG with a circular punched hole are installed into the FTHE for experimentation purposes. The experimental studies are conducted with Reynolds numbers ranging from 8000 to 25,000. The experimental results show that the use of RWVG in FTHE provided a much greater heat transfer coefficient than FTHE without RWVGs with an increase in pressure loss penalty. For better wake management, the RWVG are installed behind the circular tubes in a common flow down (CFD) arrangement. The comparative study is carried out to explore thermo-fluid performance of fin-and-tube heat exchanger with two inline circular tube arrangements for all considered cases of RWVGs. By varying the tube wall temperature (i.e., 65, 75, and 85 °C), thermo-hydraulic performance criteria such as Nusselt number (Nu), friction factor (f), and thermal performance factor (η) are compared. Lower tube surface temperature gave the highest enhancement in heat transfer performance with a lower friction factor. However, the thermal performance factor (η) for the RWVG with a circular punched hole is about 1.04–3.2%, 1.3–5.4% and 2.3–10.52% higher than RWVG-Flat for the tube wall temperature 65 °C, 75 °C, and 85 °C, respectively.

Heat Transfer in a Rotating, Blade-Shaped, Two-Pass Cooling Channel With Various 45-Deg Rib Orientations

Abstract This study features a rotating, blade-shaped, two-pass cooling channel, which follows the contour and shape of realistic airfoils. Effects of two different 45-deg rib orientations on the heat transfer and pressure loss were investigated and discussed. The cross section and orientation with respect to rotation vary in the serpentine cooling channel. The first passage of the channel is oriented at 50 deg from the direction of rotation, and the second passage is angled at 105 deg. The radially outward first passage has an aspect ratio (AR) = 4:1. After a 180-deg blade-shaped tip turn, the coolant flows radially inward into the AR = 2:1 s passage. The copper plate method was applied to calculate average heat transfer coefficients in each region of the cooling channel. The 45 deg angled ribs with a profiled cross section are placed on the leading and trailing surfaces in two ways: unusual and criss-cross. The rib spacing is P/e = 10, and rib height is e/H = 0.16. In this study, the Reynolds number ranges from 10,000 to 45,000 in the first passage, resulting in Re = 16,000 to 73,000 in the second passage. The rotational speed varies from 0 to 400 rpm, corresponding to maximum rotation numbers of 0.38 and 0.15 in the first and second passages, respectively. From the results, the 45-deg usual and unusual ribs generally have higher heat transfer than the criss-cross ribs. However, the criss-cross ribs have the lowest pressure loss penalty among the three cases. Taking both heat transfer and pressure loss into account, the 45-deg unusual ribs have a higher thermal performance under the stationary condition while the criss-cross ribs are better than other rib orientations under rotating conditions. Thus, the 45-deg unusual and criss-cross ribs can be considered for applications in real engines. The heat transfer and pressure loss data in this study provide important information for internal cooling of gas turbine blades.

Experimental evaluation of longitudinal and transverse vortex generators on the endwall of a serpentine passage

A 180-deg turning channel can be seen in many heat exchange systems, and a strong three-dimensional flow phenomenon will occur at the turning point. In order to strengthen the heat transfer inside the turn and considering the lack of relevant enhanced endwall heat transfer approach, the present study innovatively demonstrates the measures of enhanced internal endwall heat transfer using arrays of delta-winglet and conical vortex generators. The studied parameters of the vortex generators include aspect ratio (AR), spacing, and angle of attack, etc. The experimental results indicate that the longitudinal vortex generators have more advantages in increasing the heat transfer than the transverse conical vortex generators in certain configurations with the same order of magnitude of the increased area. Besides, transverse conical vortex generators are more helpful to improve the endwall heat transfer uniformity than longitudinal vortex generators. The array of longitudinal vortex generators with 45-deg angle of attack, 0.02 m pitch, and 2 aspect ratio provides the highest thermal performance for all studied cases, indicating that the longitudinal delta-winglet vortex generators can induce near-wall flow turbulence as well as convective heat transfer of the endwall with a modest pressure loss penalty. For this optimally designed endwall, the Nusselt number is augmented by up to 35%. From the perspective of energy saving, the present studied vortex generators provide a superior thermal performance at identical pumping power, which can be useful in the future design of endwalls in sharp-turn channels.

Novel designs of LVGs conformations and introduction of Batch Heated and Channeled Pipe for increasing heat transfer efficiency in pipes

The struggle for energy efficient systems is and will increasingly become the most prevalent element in every field of human activity, as new directives for green energy and minimization of energy waste are binding all new relevant projects, either operational or under development. A crucial part of this effort is rested upon the installations used for heat transfer and especially the pipes. In this paper we contribute towards this effort by proposing novel conformations for the interior of straight pipes of orthogonal cross section. Three conformations are presented and studied, for the case of a pipe having heated walls. The first two are using Longitudinal Vortex Generators (LVG) placed, not on a heated surface but inside the flow field, aiming at creating currents which will redirect the flow locally from the central regions of the pipe towards its walls. The third one is based on a completely different approach and it is named Batch Heated and Channeled Pipe (BHCP). Under this approach, one part of the fluid is separated in one small part of the pipe next to its walls so as to rise its temperature as high as possible, before being redirected towards pipe's core. Air was used as the working fluid. Models were designed in CATIA and simulated using ANSYS-Fluent computational package. Various turbulent flow conditions were considered, ranging from Re numbers starting at 5k and finishing at 20k. The efficiency of each conformation was examined based upon bulk temperature at the outlet, Nu number for various Re numbers, pressure losses caused by conformations presence as well as their effect on flow downstream of the conformation. For conformations performance evaluation was used additionally one of the best theoretical instruments for depicting and analyzing the flow and thermal fields' characteristics, specially modified for 3D flows, the Field Synergy Principle (FSP). The results reveal that the BHCP gives an extraordinary increase of the heat transfer efficiency, reaching the staggering 260% increase of mean Nusselt number. Unfortunately this comes with a very high pressure loss penalty which needs further attention. Nevertheless, this outcome regarding BHCP performance leads to the conclusion that the idea upon which this model is based is very promising and so further attempts would be considered in the direction of lowering the elevated pressure losses recorded, without neglecting any further potential improvements of the already elevated Nusselt Number.

Impact of Ceramic Matrix Composite Topology on Friction Factor and Heat Transfer

AbstractCeramic matrix composites (CMCs) are of interest for hot section components of gas turbine engines due to their low weight and favorable thermal properties. To implement this advanced composite in a gas turbine engine, characterizing the influence of CMC’s surface topology on heat transfer and cooling performance is critical. However, very few published studies have reported the flow and heat transfer effects caused by this unique surface topology. This study is an experimental and computational investigation to evaluate the effect of weave orientations, relevant to CMC surfaces, on the resulting pressure loss and convective heat transfer within an internal channel. The weave pattern was additively manufactured as the walls of a scaled-up coupon containing a single channel. For each of the three weave orientations, bulk pressure losses and convective heat transfer coefficients were measured over a range of Reynolds numbers. Scaling the pressure losses in terms of a friction factor and convective heat transfer coefficients in terms of a Nusselt number showed the importance of choosing the appropriate definition of the hydraulic diameter, which was particularly important for the friction factor. A coupon having one wall with the weave surface increased pressure loss and heat transfer compared to a smooth wall with the largest increases occurring when the CMC weave strands were perpendicular to the flow. Friction factor augmentations were much higher than heat transfer augmentations. When adding the weave to a second channel wall, pressure loss and heat transfer were further increased. Orienting the CMC strands perpendicular to the flow consistently showed the largest augmentations in heat transfer over a smooth channel, but at a much higher pressure loss penalty than that seen with the CMC strands parallel to the flow.

Effective efficiency assessment of a solar air heater having baffles spaced with different successive ratios

The baffle in the air collector duct increases heat transfer, while also significantly increasing the pressure loss penalty. Pressure loss reduction can be achieved using the unequal baffle pitch which is proposed in this study. In the current paper, a numerical investigation of an air collector duct with inclined baffles is presented. Inclined baffles spaced with successive ratio (r) from 1 to 1.4 and Reynolds number (Re) of air from 2370 to 13250 were varied to evaluate Nusselt number, friction factor and effective efficiency of the collector. 2D numerical simulations with the standard k-ε turbulence model were performed to clarify the flow mechanism through baffles. The results show that pressure loss in case of r > 1 significantly reduces compared to that of r = 1. Therefore, the maximum effective efficiency of the baffled collector duct with successive ratios from 1 to 1.3 is the same and equals to 0.6. It is better to install dense baffles near the inlet than dense baffles near the outlet because many baffles concentrated on the inlet create high turbulence in the rest of the air collector duct.

Experimental and Large Eddy Simulation Study for Visualizing Complex Flow Phenomena of Gas Turbine Internal Blade Cooling Channel With No Bend

Abstract In this study, the internal cooling channel was investigated without any bend. Smooth surfaces and dimpled surfaces were investigated using the different combinations of connecting circular and rectangular holes. The computations were performed using the large eddy simulation (LES) model for Reynolds (Re) numbers from 10,000 to 50,000. A total of six different connecting holes were investigated with a smooth and dimpled surface. A partial spherical dimple with two circular holes showed the highest heat transfer, but it has a higher pressure loss penalty. Even though the leaf dimpled surface with the rectangluar holes indicated a little low heat transfer, it represents the highest efficiency at higher Reynolds numbers because of the low-pressure drops.

Thermohydraulic Performance of a Fin and Inclined Flat Tube Heat Exchanger: A Numerical Analysis

Proper determination of inclination angle of a flat tube may increase the overall heat transfer performance without extending heat transfer surface. In this paper, the inclined flat tube heat exchanger with plain fins is numerically investigated. The influence of flat tube inclination angle and Reynolds number on the thermo-hydraulic performance index was evaluated. Tube pitch, fin spacing and flat tube size are fixed. Solving 3D computational domain with the symmetric boundary condition is used to reduce computation time. The results show that when increasing the inclination angle of the flat tube from 0 to 45°, both heat transfer and pressure loss increase because the free area of air flow decreases leading to an increase in air velocity and impingement heat transfer. The variation of inclination angle from 0 to 15°, the increase in heat transfer is stronger than the increase in the pressure loss penalty, so the performance index reaches a maximum of 0.405 at the angle of 15°. Contours of temperature, pressure and velocity at different inclination angles are presented to clarify the thermo-hydraulic characteristics of finned-tube heat exchangers using inclined flat tubes. The current work yields heat transfer enhancement ability by adjusting inclination angle of a heat transfer flat tube.

Heat Transfer Enhancement of Nanofluid Flow in a Tube Equipped with Rotating Twisted Tape Inserts: A Two-Phase Approach

Al2O3–water nanofluids along with stationary and rotating twisted tape inserts are used to increase the rate of heat transfer in a plain tube. The simulations are conducted through varying the design parameters including angular velocity of twisted tape, Reynolds number and nanofluid volume concentration. It is found that inserting a twisted tape inside a tube substantially increases the heat transfer coefficient and friction factor compared to the plain tube. Compared to the stationary twisted tape, the rotating twisted tape exhibits a great potential to modify the average Nusselt number by about 32.8–39.6% at Reynolds number of 250, depending on the angular velocity. This is attributed to the formation of conical tornado-shape structures in the flow pattern, causing more effective mixing in the flow. By increasing the Reynolds number, the enhancement in the average Nusselt number increases in stationary and decreases in rotating configurations compared with the plain tube. To assess the tradeoff between heat transfer enhancement and pressure loss penalty, the performance evaluation criterion (PEC) is calculated. The results suggest that the highest PEC is obtained at Reynolds number of 250, nanofluid volume concentration of 3% and the highest studied angular velocity.

Flow-Field Measurements in a Metal Additively Manufactured Offset Strip Fin Array Using Laser Doppler Velocimetry

Abstract Metal additive manufacturing (AM) of heat exchanger enables custom and conformal designs for a wide range of applications. However, one challenge with metal AM is the resultant surface roughness formed when using this process, which is nonexistent during traditional manufacturing processes. The goal in this study is to explore how this roughness impacts the pressure drop and flow field of a commonly used heat exchanger surface called an offset strip fin (OSF). Two OSFs of the same geometry are tested: one with an average fin roughness of 34 μm from metal AM and the other with an average fin roughness 2.5 μm, used as a baseline. The roughness from the metal AM process increased pressure losses and transitioned the flow to turbulent-like behavior at lower Reynolds numbers when compared with the smooth fin. Laser Doppler velocimetry (LDV) measurements captured the row number in the fin array where transition from laminar to turbulent-like flow occurred. The location of transition from low to high turbulence levels occurred earlier in the fin array as the Reynolds number was increased for the smooth and rough fins. Wake profiles of time-averaged axial velocity were similar between the rough and smooth fins, with the rough fins having higher levels of turbulence intensity (TI) and less symmetric wake profiles. Overall, this study indicates that a pressure loss penalty is associated with using metal AM OSF due to the resultant surface roughness and an earlier transition to turbulent-like flow.