Low Fin Research Articles

Functional morphology of endurance swimming performance and gait transition strategies in balistoid fishes.

Triggerfishes and filefishes (Balistoidea) use balistiform locomotion to power steady swimming with their dorsal and anal fins, and transition to a gait dominated by body and caudal fin (BCF) kinematics at high speeds. Fin and body shapes are predicted to be strong determinants of swimming performance and gait transitions. The goal of this study was to combine morphometrics and critical swimming tests to explore the relationships between fin and body shapes and swimming performance in a phylogenetic context in order to understand the evolution of balistiform swimming. Among 13 species of balistoid fishes, those with high aspect ratio fins tended to achieve higher critical swimming speeds than fishes with low aspect ratio fins. Species with long, large median fins and wide caudal peduncles used the balistiform gait alone for a larger percentage of their total critical swimming speed than fishes with short, small median fins and narrow caudal peduncles. Although analyses revealed overall positive relationships between median fin aspect ratios and gait transition speeds, fishes on both ends of the aspect ratio spectrum achieved higher swimming speeds using the balistiform gait alone than fishes with median fins of intermediate aspect ratios. Each species is specialized for taking advantage of one gait, with balistiform specialists possessing long, large median fins capable of the large power requirements of high-speed swimming using the median fins alone, while BCF specialists possess short, small median fins, ill-suited for powering high-speed balistiform locomotion, but narrow caudal peduncles capable of efficient caudal fin oscillations to power high-speed locomotion.

Evaluation and optimization of thermal performance for a finned double tube latent heat thermal energy storage

Embedded fin in phase change materials (PCMs) is one of the most efficient methods to enhance the heat transfer between the PCM and heat transfer fluid (HTF). An appropriate arrangement of the fins plays significant role to design a highly efficient latent heat thermal energy storage (LHTES) unit. The aim of this study is to find the most efficient arrangement of fins to accelerate the charging rate. A two-dimensional numerical model based on finite volume method (FVM) was developed with considering natural convection and the calculation results were validated with experimental data. The heat transfer characteristics of LHTES unit with different fins arrangements were firstly explored. These include no fins, straight fins, angled fins, lower fins and upper fins. Then, the effects of fins number (N), dimensionless fins length (l), heat transfer fluid temperature (Tw) and outer tube material on melting performance for four arrangements were studied. In addition, the best type of arrangements to increase the efficiency of heat exchanger was suggested. The performance enhancement of LHTES through fins configuration were quantitatively described based on complete melting time and heat storage capacity, and the conclusions are arrived as follows: when N ≤ 6, the optimum arrangement is the lower fins, while it is the angled fins when N > 6. For N = 6, only l could change the optimum arrangement of fins. At l equals 0.5 and 0.95, the optimum arrangement is angled case. While at l = 0.75, the optimum arrangement is lower case. It is also found that the heat storage capacity of lower fins configuration is minimal compared to other three configurations.

Simulation on PCM melting enhancement with double-fin length arrangements in a rectangular enclosure induced by natural convection

We numerically investigate the phase change melting enhancement in a latent heat thermal energy storage (LHTES) unit by arranging the internal double-fin length. The schemes for double-fin setting in unequal length are proposed. A fin length ratio is defined by the upper-fin length over the lower-fin length. RT42, used as the phase change material (PCM), is stored in a rectangular container to absorb thermal energy. Heat is added from the vertical side of the enclosure by a constant temperature input of 70 °C. A transient numerical model is developed and validated to simulate the phase change process with the natural convection involved. The melting enhancement by fin length arrangement is firstly characterized by the evolution of melt fraction with time. It reveals that in the premise of total fins length invariant, the schemes with short upper fin and long lower fin can positively enhance the PCM melting rate. With the length ratio at 0.25, the total melting time can save about 25% based on the equal length scheme. Such fin length arrangement scheme also performs better on the storage rate of sensible and latent heat energy. However, the schemes with long upper fin and short lower fin show a negative effect. To explore the mechanism of heat transfer enhancement by the double-fin length arrangement, the contours of liquid fractions are successfully predicted, as well as the liquid PCM flow motions. It is found that, when the length ratio is lower than 1, the natural convection currents are intensified significantly, with the clear chaotic flow structures appearing. However, the flow motions driven by natural convection become weak with the length ratio higher than 1. Later, the maximum velocity recorded during the entire melting process is also compared in detail. The length of solid-liquid PCM interface is proposed to evaluate the heat transfer for the first time. The scheme of fin length ratio at 0.25 performs a longer length of solid-liquid interface than the others, which is another important factor for the PCM melting enhancement. The heat transfer mechanism is detailed analyzed by the surface-averaged Nusselt number into three stages. The effects of fin length arrangement are reported mainly taking at the strong convection stage. In the later optimization studies, it is observed that when the length ratio is further decreased to 0.11, the total melting time is minimum for the current LHTES unit. Comparing with the equal length scheme, about 40.5% melting time is reduced. When the temperature input decreases from 70 °C to 50 °C, the time saving ratio can increase to 45%.

Effect of low dorsal fin on the breakdown of vortices over a slender delta wing

Previous theoretical and experimental works show that the originally steady symmetric vortices over a flat-plate delta wing at zero side slip but high angles of attack are destabilized by the addition of a low dorsal fin, which renders the separation vortices asymmetric, unsteady, or non-conical. This paper examines the effect of the dorsal fin on the onset of vortex breakdown. A sharp-edged flat-plate delta wing with a 7.5 deg semi-apex angle is tested in a low-speed wind tunnel. The unsteady velocity and vorticity fields are mapped out at the 60% wing root chord location to quantify the vortex burst process caused by the addition of the low dorsal fins by using the laser Particle-Image-Visualization (PIV) technique. Two fin heights with the ratio of the local fin height to the local wing semi-span 0.3 and 0.6 are tested. The results demonstrate that the loss of global stability of the vortex configuration due to the addition of the low dorsal fin accelerates the onset of vortex breakdown and causes one of the vortices in the pair to burst periodically. The frequency and size of the burst are related to the height ratio of the fin.

Numerical investigation on effects of using segmented and helical tube fins on thermal performance and efficiency of a shell and tube heat exchanger

Thermal performance of a shell-and-tube heat exchanger is investigated numerically using ANSYS FLUENT software under various conditions. Before proceeding with simulations, sensitivity analysis is performed for both mesh grid and turbulence model and the results are compared and validated with results obtained from Bell-Delaware method. The numerical study is consisted of three parts: First the effect of tube wall relative roughness and Reynolds number on total heat transfer and pressure drop is investigated. In the second part, effect of vertical segmented tube fins on heat transfer is studied under two independent adjustable parameters, namely fin pitch and fin height while surface roughness is fixed. Finally, a novel design of fins (helical fin) is proposed and its influence on thermal performance of the heat exchanger is investigated and results are compared to no-fin and segmented fin configurations. It is found that tube fins in general enhance overall efficiency of the heat exchanger. The efficiency is increased by 9.5% and 6% when the proposed helical fins and segmented fins are used respectively. CFD results purpose the efficiency is increased by increasing fin height, but decreased by increasing fin pitch. Helical fins increase effectiveness of heat exchanger by 17% compared to plain tubes. Although increasing surface roughness increases the efficiency, it leads to faster corrosion which means higher maintenance costs and is not desirable. The efficiency of the heat exchanger therefore can be prominently increased when combination of low surface roughness and helical fins with smaller pitch and larger height are used.

Two-dimensional analysis of low-pressure flows in an inclined square cavity with two fins attached to the hot wall

The gaseous low-pressure flow of a steady-state two-dimensional laminar natural convection heat transfer in a cavity with an attached two solid fins to the hot wall is numerically investigated. Such flows can be found in many engineering applications such as the “evacuated” solar collectors and in the receivers of the solar Parabolic Trough Collectors (PTCs), nuclear reactor cooling and electronic equipment cooling. Buoyancy effect is modeled using Boussinesq approximation. Effects of Knudsen and Rayleigh numbers, location and length of the fins, conductivity ratio and fins porosity, and the tilt angle on the flow and heat transfer characteristics are investigated. Physical parameters ranges in this study are as follows; 0≤Kn≤0.1, 103≤Ra≤106, LF takes the values of 0.25, 0.5 and 0.75 m, HF takes the values of 0.25_0.5, 0.25_0.75 and 0.5_0.75, 1≤Kr≤8000, 0≤ε≤1 and 0∘≤θ≤90∘. It is shown that Nusselt number depends directly on Rayleigh number and inversely on Knudsen number. In addition, it is found that attaching two solid fins to the hot wall will enhance the heat transfer for such flows. Moreover, it is found that the porous fins are superior to the solid fins as far as the heat transfer is concerned. In addition, it is shown that for the geometry where the lower fin height to cavity length ratio is 0.25 and the upper fin height to cavity length ratio is 0.75, the best heat transfer is achieved. In addition, for the fin lengths considered in the study, it is concluded that by increasing the length of the fin, a better heat transfer is achieved. Also, it is found that by increasing the tilt angle of the cavity, a better heat transfer is achieved up to a certain value which was found to be (30°) where beyond this value, Nusselt number will decrease. In addition, it is found that by increasing the conductivity ratio up to a certain value (103), better heat transfer is gained. Finally, a correlation among Nusselt number and the parameters investigated in this research proposed as Nu=0.02197ε0.00932sin(θ)0.00373Kr0.0273(h2/LF)2.814Ra0.13((h2−h1)/LF)1.373(h1/LF)1.615Kn0.37.

Mechanosensation is evolutionarily tuned to locomotor mechanics

The biomechanics of animal limbs has evolved to meet the functional demands for movement associated with different behaviors and environments. Effective movement relies not only on limb mechanics but also on appropriate mechanosensory feedback. By comparing sensory ability and mechanics within a phylogenetic framework, we show that peripheral mechanosensation has evolved with limb biomechanics, evolutionarily tuning the neuromechanical system to its functional demands. We examined sensory physiology and mechanics of the pectoral fins, forelimb homologs, in the fish family Labridae. Labrid fishes exhibit extraordinary morphological and behavioral diversity and use pectoral fin-based propulsion with fins ranging in shape from high aspect ratio (AR) wing-like fins to low AR paddle-like fins. Phylogenetic character analysis demonstrates that high AR fins evolved independently multiple times in this group. Four pairs of species were examined; each included a plesiomorphic low AR and a high AR species. Within each species pair, the high AR species demonstrated significantly stiffer fin rays in comparison with the low AR species. Afferent sensory nerve activity was recorded during fin ray bending. In all cases, afferents of stiffer fins were more sensitive at lower displacement amplitudes, demonstrating mechanosensory tuning to fin mechanics and a consistent pattern of correlated evolution. We suggest that these data provide a clear example of parallel evolution in a complex neuromechanical system, with a strong link between multiple phenotypic characters: pectoral fin shape, swimming behavior, fin ray stiffness, and mechanosensory sensitivity.

A new species of the genus Diaphenchelys (Anguilliformes: Muraenidae) from Thailand

A new species of moray eel, Diaphenchelys dalmatian is described based on five specimens [289.8–503.0 mm total length (TL)] collected from the western coast of peninsular Thailand and the Gulf of Thailand. It can be easily distinguished from Diaphenchelys pelonates McCosker and Randall 2007, another species of the genus Diaphenchelys McCosker and Randall 2007, by its coloration (ground color white with brown dalmatian-like spots vs. brown with pale vermiculate pattern). The present new species also differs from D. pelonates in its longer tail (62.0–64.6% TL vs. 59.6–61.5%), fewer infraorbital pores along upper lip (three vs. four), fewer mandibular pores (five vs. six or seven), and fewer vertebral counts (preanal vertebrae 43–46 vs. 55–58; total 126–131 vs. 153–155). Diaphenchelys is closely similar to the genus Strophidon McClelland 1844 in the shape of neurocranium, the elongate body, low vertical fins, eye location, jaw shape, and presence of inner mandibular teeth. However, both differ in the vertebral counts (126–155 in Diaphenchelys vs. 164–208 in Strophidon) and coloration (prominent pattern vs. uniform).

Tadpole ofProceratophrys mantiqueira(Anura: Odontophrynidae), with a Description of Its Internal Oral Features

We describe the larval external morphology and internal oral features of Proceratophrys mantiqueira from its type locality and provide novel natural history information for adults. The tadpoles of P. mantiqueira (Stage 37) exhibit a depressed body with low tail fins, eyes positioned dorsally, and a ventral oral disc bordered by a single row of marginal papillae, with a wide gap on the anterior labium; a few submarginal papillae may be present. The labial tooth row formula is 2(2)/3(1). The shape and amount of papillae in the buccal floor, especially the infralabial and lingual papillae, can distinguish the tadpole of P. mantiqueira from other congeners. Our results add important new data about the larval morphology of this species and may help future studies on the intrageneric relationships of Proceratophrys.

A Quick Overview of Compact Air-Cooled Heat Sinks Applicable for Electronic Cooling—Recent Progress

This study provides an overview regarding enhancement of an air-cooled heat sink applicable for electronic cooling subject to cross-flow forced convection. Some novel designs and associated problems in air-cooled heat sinks are discussed, including the drawback of adding surfaces, utilization of porous surfaces such as metal foam or carbon foam, problems and suitable applicable range of highly interrupted surfaces (louver or slit) and longitudinal vortex generator. Though the metal foam may accommodate significant surface area, it is comparatively ineffective for air-cooling application due to its much lower fin efficiency, and this shortcoming can be improved by integrating with solid fin. For highly dense fin spacing (e.g., <1.0 mm), cannelure or grooved surface may be a better choice, and fin structure with periodic contraction and expansion may not be suitable for it introduces additional pressure drop penalty. The partial bypass concept, which manipulates a larger temperature difference at the trailing part of heat sink, can be implemented to significantly reduce the pressure drop. Through some certain niche operation, t the thermal resistance of the partial bypass heat sink may be superior to the conventional heat sink. The trapezoid fin surface featuring easier manufacturing and a smaller weight is shown to have competitive performance against traditional rectangular fin geometry. The IPFM (Interleaved Parallelogram Fin Module) design which combines two different geometrical fins with the odd number fins being rectangular shape, and parallelogram shape in even fin numbers, shows 8%–12% less surface than conventional design but still offers a lower thermal resistance than the conventional rectangular heat sink in lower flowrate operation. The cross-cut design shows appreciable improvements as compared to the conventional plate fin design especially in high velocity regime and the single cross-cut heat sinks are superior to multiple cross-cut heat sinks.

Study of convection heat transfer enhancement inside lid driven cavity utilizing fins and nanofluid

In the present study, the effect of suspension of nanoparticle on mixed convection flow is investigated numerically in lid driven cavity with fins on its hot surface. Study is carried out for Richardson numbers ranging from 0.1 to 10, fin(s) height ratio change from 0.05 to 0.15 and volume fraction of nanoparticles from 0 to 0.03, respectively. The thermal conductivity ratio (kfin/kf) is equal to 330 and Grashof number is assumed to be constant (104) so that the Richardson numbers changes with Reynolds number. Results show that the heat transfer enhances by using nanofluid for all studied Richardson numbers. Adding fins on hot wall has different effects on heat transfer depend to Richardson number and height of fins. Use of low height fin in flow with high Richardson number enhances the heat transfer rate while by increasing the height of fin the heat transfer reduces even lower than it for pure fluid. The overall enhancement in Nusselt number by adding 3% nanoparticles and 3 fins is 54% at Ri=10. They cause reduction of Nusselt Number by 25% at Ri=0.1. Higher fins decrease the heat transfer due to blocking fluid at corners of fins.

Low Height Ultra-thin Fin on A5083 Aluminum Plate Fabricated by Friction-stir Forming

Recent demands on miniaturization of an electronic apparatus have caused board-space constraints, and thermal management is getting increasingly difficult. Thermal management employing heat sinks is often compromised by the space constraints for a product design. Lower profile passive heat sinks having thin fins are among necessary solutions to these space limitations. Most such products have been generated by conventional or back pressure applied forging. However, thinness of its fin is limited, though a higher density of fins is more effective. This paper describes a new forming technology, friction-stir forming (FSF), to generate a low profile, ultra-thin fin. The suggested process is as follows. The authors put a material plate on a die and conducted friction stirring on its back surface. The material deformed and precisely filled narrow grooves of the die due to high pressure and heat caused by friction stirring. This study investigates the forming conditions and the corresponding results including the height limit of the fin. Consequently, we successfully generated low-profile, ultra-thin fins with 0.5mm thickness and less on 3mm-thick JIS A5083P-O aluminum plate.

Constructal multi-scale structure of PCM-based heat sinks

This paper inquires the effectiveness of a PCM-based heat sink as a reliable solution to portable electronic devices. This sink is composed of a PCM with low thermal conductivity and fins to boost its conductivity. The optimization is subjected to fixed heat sink volume filled with PCM between vertical equidistant fins. New fins are installed in the unheated space existing in each enclosure which is not involved in thermal distribution from vertical fins to the PCM. Based on the same principle, new fins generations are augmented stepwise to the multi-scale structure. The steps of adding fins will continue up to the point that the objective function reaches its maximal value, i.e., maximizing the longest safe operation time without allowing the electronics to reach the critical temperature. The results indicate that in each length of the enclosure, the optimum volume fraction and the best fins distance values exist in which the heat sink performance becomes maximum, and adding more fins lowers the performance of the heat sink. Increasing the enclosure’s length by \(2^{n}\) does not change them. For an enclosure with constant length, the optimal number of steps for adding fins within the enclosure is a function of the fin thickness. The results indicate that increasing the thickness changes the optimal number of adding fins inside the enclosure (normally a decrease). As the fin thickness is lowered, there will be a higher effect by adding vertical fins in the enclosure. Numerical simulations cover the Rayleigh number range \(2\times 10^{5}\le \hbox {Ra}_{\mathrm{H}} \le 2.7\times 10^{8}\), where H is the heat sink height.

Transfer Pricing: Strategies, Practices, and Tax Minimization

AbstractUsing a survey of tax executives from multinational corporations, we document that some firms set their transfer pricing strategy to minimize tax payments, but more firms focus on tax compliance. We estimate that a firm focusing on minimizing taxes has a GAAP effective tax rate that is 6.6 percentage points lower and generates about $43 million more in tax savings, on average, than a firm focusing on tax compliance. Available COMPUSTAT data on sample firms confirm our survey‐based inferences. We also find that transfer pricing‐related tax savings are greater when higher foreign income, tax haven use, and R&D activities are combined with a tax minimization strategy. Finally, compliance‐focused firms report lower FIN 48 tax reserves than tax‐minimizing firms, consistent with the former group using less uncertain transfer pricing arrangements. Collectively, our study provides direct evidence that multinational firms have differing internal priorities for transfer pricing, and that these differences are strongly related to the taxes reported by these firms.

Effects of the partially movable control fin with end plate of underwater vehicle

Underwater torpedo has control fin with very low aspect ratio due to launching from limited size of cylindrical torpedo tube. If the aspect ratio of control fin of underwater vehicle is very low three-dimensional flow around control fin largely reduces control forces. In this study, the end plate was applied to reduce the three-dimensional flow effects of partially movable control fin of underwater vehicle. Through numerical simulations the flow field around control fin was examined with and without end plate for different flap angles. The pressure, vorticity, lift and torque on the control fin were analyzed and compared to experiments. The comparison have shown a reasonable agreement between numerical and experimental results and the effect of end plate on a low aspect ratio control fin. When the end plate was attached to the movable control fin, the lift increased and the actuator shaft torque did not significantly change. As this means less consumption of the actuator shaft torque compared to the control fin that has the same control force, the inner actuator capacity can be reduced and energy consumption can be saved. Considering this, it is expected to be effectively applied to the control fin design of underwater vehicles such as torpedoes.

Comparison of production efficiency and quality of differently cultured pikeperch (Sander lucioperca L.) juveniles as a valuable product for ongrowing culture

Production efficiency, frequency of fin erosion, skeletal and gill covers deformities, proximal composition of fish body with special emphasis on fatty acid contents in liver and muscle, oxidative stress and antioxidant response in gill, liver, muscle and intestine were analyzed and compared in exclusively RAS- and POND-cultured juveniles and juveniles produced with the combination of POND and RAS aquaculture in pikeperch (Sander lucioperca L.) with final body weight between 8.5 and 9.5 g. Higher production efficiency, lower fin erosion, no morphological deformities, higher level of essential fatty acids and lower oxidative stress were found in POND–RAS- and POND-cultured juveniles compared to exclusively RAS-produced pikeperch. This study showed that intensive pikeperch juvenile production still needs next technological innovations. On the other hand, the combination of POND–RAS aquaculture has provided a good potential to be an alternative production system producing high-quality juveniles for intensive or pond ongrowing culture mainly in countries with large pond area.

Experimental study on a novel battery thermal management technology based on low density polyethylene-enhanced composite phase change materials coupled with low fins

Phase change materials (PCM) cooling has been considered as the most potential alternative to traditional battery thermal management (BTM) technology, but significant challenges remain: PCM leakage, poor mechanical properties and low surface heat transfer capability between PCM and the external environment. Here, we develop a BTM technology based on the ternary composite materials of expanded graphite (EG), paraffin (PA) and low-density polyethylene (LDPE) coupled with low fins. The as-doped LDPE framework can not only enhance the mechanical molding property but also prevent PA leakage to a great extent. Coupling with low fins endows the entire BTM system with high surface heat transfer capability. For instance, the as-prepared LDPE/EG/PA composite PCM shows much better mechanical properties and cooling effect in comparison to EG/PA composite and air cooling, respectively. After coupling with low fins, the as-constructed PCM-based battery module presents excellent heat dissipation performance, keeping the battery pack working under the safety temperature of 50°C and temperature difference of 5°C for lithium-ion power batteries, even at an extremely high discharge rate of 3.5C.

Effect of flow maldistribution on the optimal design of a cross flow heat exchanger

In this study, a cross flow heat exchanger is optimized based on multi objective optimization algorithm by considering the effects of flow maldistribution for both cold and hot sides. For this purpose, total annual cost (TAC) and effectiveness of exchanger are selected as fitness functions and six decision variables including the heat exchanger and fin geometries are considered as decision variables. The optimization is performed for the three non-uniform velocity inlet profiles including linear, parabolic and power law and their optimum results are compared with the uniform (constant) profile. It is observed that, the Percentages of reduction in effectiveness for the final optimum solution are in the range of 2.93–4.88%, 1.50–3.38% and 0.79–1.24% respectively in the cases of linear, parabolic and power law profiles compared with constant inlet profiles. Moreover, Percentages of growth in the TAC for the final optimum solution are in the range of 13.00–16.49%, 6.97–10.49% and 0.77–1.63% respectively in the cases of linear, parabolic and power law profiles compared with constant inlet profiles. In addition, the higher hot and cold stream flow lengths and lower fin height and fin spacing are needed in the cases of linear, parabolic and power law profiles compared with the constant velocity profile for the fixed value of effectiveness.

Effect of Dorsal Fin on Symmetry of Vortices over Slender Delta Wing

Three different sets of experiments are designed to reveal the behavior of the vortex flow over a delta wing with different fin heights. A sharp-edged flat-plate delta wing with an 82.6-deg-sweep angle is tested in low-speed wind tunnels at angles of attack up to 35 deg. The same tests are performed on an identical delta-wing model but with a flat-plate dorsal fin. The ratio of the local fin height to the local wing semispan varies from 0.3 to 1.5. The results of smoke laser-sheet visualization, particle image velocimetry, and force measurement are obtained and presented. The test results show that the vortices over the delta-wing-alone model at high angles of attack and zero sideslip are stable, symmetric, and steady before vortex breakdown, but a low dorsal fin renders the originally symmetric vortices asymmetric at the same angle of attack; the flow recovers symmetry and conicity when a higher fin is added. These results are in agreement with predictions by the stability theoryCaiet al., (“Stability of Symmetric Vortices in Two Dimensions and over Three-Dimensional Slender Conical Bodies,” Journal of Fluid Mechanics, Vol. null, 2003, pp. 65–94). This agreement demonstrates that the absolute type of instability is responsible for loss of symmetry of the vortices over a delta wing with a fin within the range of tested conditions.

Performance of finned tubes used in low-pressure capillary-assisted evaporator of adsorption cooling system

Adsorption cooling systems (ACS) are a viable alternative to vapor compression refrigeration cycles (VCRCs) where low-grade waste heat is readily available. In an ACS, which works with water as a refrigerant, the operating pressure is quite low (∼1kPa). Under such low evaporation pressures, the height of a water column affects the water saturation pressure and, consequently, its saturation temperature, which can severely affect the performance of an ACS. This makes the design of evaporators of ACS different from those of conventional VCRCs. One practical solution in low pressure (LP) evaporators is to use capillary-assisted tubes. In this study, three enhanced tubes with different fin geometries (fin spacing and fin height), and a plain tube as a benchmark, are tested for different chilled water inlet temperatures. The results show that enhanced tubes have 9.8–21 times lower external convective heat transfer resistances compared to the plain tube. In addition, the enhanced tube with the highest fin height (Turbo Chil-26 FPI) has 33% lower external convective resistance than that with lower fin height (GEWA-KS-40 FPI). The major finding of this study is that up to 89% of the overall thermal resistance in the enhanced tubes is due to the internal convective resistance. This clearly indicates that the main bottleneck in the performance of a LP evaporator is the convective heat resistance inside the tube. Therefore, the internal heat transfer coefficient and internal surface area of enhance tubes should be increased to enhance the performance of the LP evaporator and overall specific cooling power (SCP) of ACS.