Insertion Of Fins Research Articles

Integration of solar thermal collectors and heat pumps with thermal energy storage systems for building energy demand reduction: A comprehensive review

Solar energy, coupled with innovative technologies, holds the promise of propelling buildings towards net-zero and carbon neutrality. In this regard, this review explores the integration of solar technologies, heat pumps, and thermal energy storage systems to reduce building energy demand. It thoroughly examines various types of solar thermal collectors (STCs), including both concentrating devices like compound parabolic concentrators and parabolic troughs, as well as non-concentrating designs such as flat plate and evacuated tube collectors. It examines innovative strategies for enhancing STC performance, such as alternative profiles for compound parabolic concentrators and the insertion of thermal fins in absorber tubes. Furthermore, the review categorizes solar-assisted heat pumps (SAHPs) into indirect expansion (IDX) and direct expansion (DX) systems, describing their advantages and limitations. It performs a comparison between IDX-SAHPs and DX-SAHPs, explaining their effectiveness and applicability. Eventually, the review explores thermal energy storage materials, categorizing them into sensible heat storage, latent heat storage, and thermochemical heat storage (TCHS). It discusses the advantages and disadvantages of each category, as well as notable materials within them. A comparative examination between open and closed systems for TCHS further enriches the discussion. Throughout the review, recent advancements and key findings from relevant studies are summarized in separate tables, offering valuable information into practical strategies for sustainable building energy systems. Regarding the provided sections, this review plays a crucial role in introducing scholars to practical methods employed in recent years to integrate the STCs with heat pumps and thermal energy storage systems.

Influence of variable gravity on the phase change material for enclosed vertical channels with helical fins

This study numerically investigates the influence of variable gravity on the melting behaviour of a phase change material (PCM- paraffin wax RT27) contained within an enclosed vertical channel under different gravity conditions, specifically those found on the Earth, the Moon, and under the microgravity environments. Furthermore, the impacts of incorporating various number of helical fins within the PCM unit under different gravitational conditions are assessed for the first time. The findings indicate that the melting efficiency of PCM is considerably affected by the reduced gravity conditions, due to changes in the natural convection, velocity, and temperature; the melting time is twice as long under the moon-gravity conditions and sixfold longer under the microgravity conditions compared to the earth-gravity. It is also observed that reduced efficiency can be remedied by the insertion of fins into the PCM unit. The breakdown of the natural convection vortices with different number and orientation of fins expedites the melting process for all gravity conditions thus leading to improved performance in melting and energy storage.

Numerical investigation of the melting characteristics of spherical-encapsulated phase change materials with composite metal fins

A spherical phase change material (PCM) capsule with embedded composite fins for latent thermal energy storage is proposed and studied in this paper. A three-dimensional numerical model is established and validated by comparing with experimental data in the literature. The influences of the embedded fins with different structures, capsule size, and heating temperature on the melting performance are analyzed. Results show that the insertion of composite metal fins promotes the melting process owing to the extension of thermal surface. The fin with perforations exhibits higher energy storage performance as compared to the non-perforated one, which can be attributed to the reduction of the blockage effect as well as the increment in the filling volume of PCM. The punched fin with three perforations in each sheet is preferable to adopting in spherical PCM capsule in view of the less time required for completely melting and the higher energy storage capacity. However, as the size of capsule increases, the heat transfer enhancement contributed by the inclusion of the embedded fins reduces. In addition, the melting process can be accelerated significantly by raising the temperature of external shell surface from 340 to 360 K, while such improvement tends to be less pronounced for the further increase in heating temperature. This study can provide useful guidance for the optimal design of thermal energy storage system with spherical PCM capsules.

A numerical study of PCM battery thermal management performance enhancement with fin structures

Phase change material (PCM) cooling is regarded as a promising thermal management technique to realize a proper battery working temperature. However, the low thermal conductivity of PCM restricts its practical applications. In this study, the impact of aluminum fin insertion on the thermal performance of PCM thermal management is explored. Couples of fin structure shapes were adopted and their performances were compared. It is demonstrated from the simulation results that, among the fin structures investigated in this study, the bifurcated fin structures achieved the lowest battery maximum temperatures, specifically, the battery temperature was reduced by 6.16 K compared to the pure PCM case under 5C discharge (5C means that battery is discharged from full of charge to 0% state of charge in 1/5 h). The 2-branch bifurcated fin structure could realize a further 0.50 K temperature drop than the single-branch counterpart. Besides, the impacts of various parameters were investigated. The maximum temperature at the end of 5C discharge process was reduced from 314.30 K to 311.36 K when the fin quantity increased from 3 to 8. The maximum battery temperature reaches up to 313.80 K if the thermal contact resistance between the battery and fin structure grows to 0.0025 W/(m2⋅ K) with 8 fins while it could be decreased by 1.21 K if the contact resistance reduced half to 0.00125 ((m2⋅ K)/W. The maximum battery temperature was found to decrease by 0.27 K with PCM width enlarged from 28 mm to 29 mm.

A new deep-water conger eel of the genus Rhynchoconger (Anguilliformes: Congridae) from the southwest coast of India, Arabian Sea.

A new species of deep-water conger eel, Rhynchoconger bicoloratus sp. nov., is described herein based on three specimens collected from the deep-sea trawlers landing at Kalamukku fishing harbour, off Kochi, Arabian Sea, from a depth beyond 200 m. The new species is distinguished from its congeners by having the following combination of characters: head larger than trunk, rictus at posterior margin of pupil, dorsal fin origin slightly before the pectoral fin insertion, eye diameter 1.7-1.9 in snout, ethmovomerine teeth patch broader than long with 41-44 recurved pointed teeth in 6-7 rows, vomerine teeth patch pentagonal shaped with single tooth on posterior end, pre-anal vertebrae 35, body bicoloured, peritoneum and stomach black. Genetically, the new species differs from its congeners with a divergence of 12.9-20.1% in the mitochondrial COI gene.

Numerical Simulation of the Fin Impact on the Cooling of the Shell of a Rotary Kiln

This work consists of a numerical study of a thermally stressed rotary kiln shell part in a cement plant. The numerical simulations are performed by using the finite volume method for the discretization and the simple algorithm for resolution. The velocity air injection, its temperature, and the kiln rotational velocity are the main parameters under investigation. The distribution of temperature, velocity, and pressure, as well as the evolution of the Nusselt number are determined. In the second step of this study, fins are inserted on the shell to examine their effect on cooling. The results analysis shows that the insertion of fins to the shell has a significant influence on the decrease in temperature of the shell’s external surface. The study shows that this decrease in temperature depends significantly on the air injection rate, not on its temperature, and a bit less on the rotating velocity of the kiln. To avoid overloading our equipment (weight of the shell), only four fins distributed around the kiln are added to explore their effect.

Multi-objective optimization for assisting the design of fixed-type packed bed reactors for chemical heat storage

• Multi-objective optimization applied on packed bed reactor for chemical heat storage. • Simultaneous maximization of heat storage density, rate and exergy efficiency. • Optimal design of thickness, reaction condition and fabrication of composite material. • High thermal contact conductance is recommended when utilizing enhanced composites. • Limitations on the packed bed’s thickness for achieving high exergy efficiency. The enhancement of heat transfer in packed bed reactors is essential for the practical application of chemical heat storage technology. This work presents the first attempt to utilize a multi-objective optimization algorithm for the design of packed bed reactors comprising heat-transfer-enhanced materials as an alternative to the insertion of metallic fins. A numerical model for the simulation of heat transfer with chemical reaction in a flat packed bed reactor comprising a composite of Ca(OH) 2 (reagent) and a silicon-impregnated silicon carbide foam (thermal conductivity enhancer) is developed. The genetic algorithm applied to the model aims to optimize four design parameters: the effective thermal conductivity of the packed bed material, its thickness, the thermal contact conductance, and the heat supply temperature. As a result, it determines the optimal trade-off between heat storage density, average heat storage rate and exergy efficiency. Under the assumptions of the model, the Pareto solution indicates that the optimal foam porosity is the interval 70-80%, while the optimal thickness is the interval 20-70 mm. The analysis suggests the necessity to improve the thermal contact conductance in packed bed reactors and, for achieving higher exergy efficiency, thinner (modular) packed beds result better performing than thicker ones.

Investigation of flow and heat transfer behavior of integrated pin fin-aluminum foam heat sink

• A novel aluminium foam heat sink (AFHS) consisting of pin fin inserts is proposed. • The developed mathematical model is validated with experimental data. • Thermo-hydraulic characteristics of proposed heat sinks are numerically studied. • Pin fin inserts lead to an enhancement on the heat removal capability of AFHS. • Pressure drop along the flow direction increases with pin fin insertion into AFHS. With the rapid development in the electronics industry, the thermal management of high power density electronic products (HPDEPs) has become very important and requires innovative heat removal technologies. In this study, an integrated heat sink (IHS) fabricated by combining aluminum foam and pin-finned heat sink configurations that are frequently used in the cooling of electronic products has been proposed as an effective solution for the thermal management of HPDEPs. The heat removal and pressure drop characteristics of the IHS were numerically investigated for its various design conditions such as the length/height ratio ( L/H ), fin profile, fin/foam height ratio ( H fin /H foam ), and heat sink/fin volume ratio ( V hs /V f ) over the range of Reynolds ( Re Dh ) number from 500 to 3500 by using the COMSOL Multiphysics v5.4. Before the numerical study was performed, to verify the outcomes of the developed simulation models, some of the IHS subjected to the numerical study were fabricated and their pressure drop and heat removal performances were experimentally examined in the range of Re Dh from 596 to 3551. As a result of the study, it was found that the thermal contact resistance ( TCR ) between the IHS and the heated surface has a greater effect on the Nusselt ( Nu ) number compared to the TCR between the solid fins and aluminum foam. The in-line or staggered arrangement of pin fins inside the aluminum foam did not lead to any significant difference in the overall performance of investigated IHS. For all the IHS examined, an increase in Re Dh results in a similar increase in the Nu and ΔP along the flow direction. In general, the most efficient IHS among the investigated ones in terms of the H fin /H foam ratio is the IHS with half-length fins, H fin /H foam =15/30. Average values of thermal performance factor ( ƞ) of the IHS with H fin /H foam ratio of 15/30 in in-line and staggered arrangement over the Re Dh number studied are 1.3 and 1.25 times higher relative to IHS with H fin /H foam ratio of 30/15. For a fixed number of fins, η of the IHS with fins of 4mm diameter is superior up to Re Dh =2000, after which, the situation varies in favor of the 8mm solid finned aluminum foam heat sink. Increasing the fin diameter from 4mm to 12mm in both fin configurations worsens the average value of ƞ by 10%. For a constant fin diameter, IHSs with 9 fins in in-line and 8 fins in staggered configuration have the highest ƞ when the Re Dh is greater than 2500 and 2000, respectively. Among the fin profiles examined, the IHS with elliptical fins is found to have the highest η , with a value of 1.24, at Re Dh =3500.

Ontogeny of a tessellated surface: Carapace growth of the longhorn cowfish Lactoria cornuta

Biological armors derive their mechanical integrity in part from their geometric architectures, often involving tessellations: individual structural elements tiled together to form surface shells. The carapace of boxfish, for example, is composed of mineralized polygonal plates, called scutes, arranged in a complex geometric pattern and nearly completely encasing the body. In contrast to artificial armors, the boxfish exoskeleton grows with the fish; the relationship between the tessellation and the gross structure of the armor is therefore critical to sustained protection throughout growth. To clarify whether or how the boxfish tessellation is maintained or altered with age, we quantify architectural aspects of the tessellated carapace of the longhorn cowfish Lactoria cornuta through ontogeny (across nearly an order of magnitude in standard length) and in a high‐throughput fashion, using high‐resolution microCT data and segmentation algorithms to characterize the hundreds of scutes that cover each individual. We show that carapace growth is canalized with little variability across individuals: rather than continually adding scutes to enlarge the carapace surface, the number of scutes is surprisingly constant, with scutes increasing in volume, thickness, and especially width with age. As cowfish and their scutes grow, scutes become comparatively thinner, with the scutes at the edges (weak points in a boxy architecture) being some of the thickest and most reinforced in younger animals and thinning most slowly across ontogeny. In contrast, smaller scutes with more variable curvature were found in the limited areas of more complex topology (e.g., around fin insertions, mouth, and anus). Measurements of Gaussian and mean curvature illustrate that cowfish are essentially tessellated boxes throughout life: predominantly zero curvature surfaces comprised of mostly flat scutes, and with scutes with sharp bends used sparingly to form box edges. Since growth of a curved, tiled surface with a fixed number of tiles would require tile restructuring to accommodate the surface's changing radius of curvature, our results therefore illustrate a previously unappreciated advantage of the odd boxfish morphology: by having predominantly flat surfaces, it is the box‐like body form that in fact permits a relatively straightforward growth system of this tessellated architecture (i.e., where material is added to scute edges). Our characterization of the ontogeny and maintenance of the carapace tessellation provides insights into the potentially conflicting mechanical, geometric, and developmental constraints of this species but also perspectives into natural strategies for constructing mutable tiled architectures.

Experimental investigation on heat transfer performance of solar collector with baffles and semicircular loops fins under varied air mass flow rates

Insertion of fins and turbulators is one of the effective approaches to augment the restricted heat transfer characteristics of an air-based flat plate solar collector and the creation of holes/perforations in baffles and fins further increase the degree of improvement. Therefore, the prime objective of the present study is the experimental assessment of temperature distribution, heat transfer coefficients and thermal efficiency of a solar air heater integrated with baffles and fins in the form of hollow semicircular loops. The plain absorber plate was modified with the continuous insertion of semicircular loops of 0.03 m radius, constructed with wire of 0.002 m thick in a staggered manner. The experiments were conducted for measurement of solar intensity and collector temperature at air mass flow rates ranging from 0.006 to 0.02 kg/s. Results indicated the temperature of the air to be lower than loops and absorber plate but surpassed the glass plate temperature. The average temperature rise of air in finned collector was ranging from 14.08 to 22.78 °C, remarkably higher than conventional flat plate solar collector. Air mass flow rate of 0.02 kg/s presented 109%, 80.72% and 62.56% augmented average heat transfer coefficient than 0.006, 0.01 and 0.015 kg/s, respectively and 22.03% enhanced thermal efficiency than 0.006 kg/s. Further, the finned collector at 0.02 kg/s yielded 19.73–34.3% superior average thermal efficiency and 37.38–66.05% escalated heat transfer coefficient over the smooth absorber plate solar collector. The solar collector with hollow fins and baffles will be suitable for domestic and industrial applications like agricultural products drying, greenhouse, and space heating.

Benthic–limnetic morphological variation in fishes: Dissolved organic carbon concentration produces unexpected patterns

AbstractVariation in traits related to foraging and locomotion in benthic and limnetic habitats has been observed in many fishes. Benthic and limnetic food chain productivity in lakes is strongly influenced by the concentration of dissolved organic carbon (DOC) in the water, suggesting that DOC might indirectly impose selection on these traits and lead to classic benthic forms at low DOC concentrations and limnetic forms at high DOC concentrations. We tested this hypothesis via geometric morphometric and meristic analyses of bluegill sunfish (Lepomis macrochirus, Centrarchidae) from 14 lakes with DOC concentrations ranging from 4 to 24 mg/L. These lakes, located in close proximity to each other, straddle the drainage divide between the Mississippi River and Laurentian Great Lakes basins in northern Wisconsin, USA. Bluegill morphology was consistently related to lake DOC concentration in both drainage basins, despite differences in morphology between basins. Fish from higher DOC lakes had deeper bodies and smaller heads, among other differences, though the proportion of shape variation described by DOC was low. Gill raker length and inter‐raker spacing were positively related to DOC concentration. Although some traits were thus related to DOC concentration, the directions of these relationships did not match the predicted benthic–limnetic patterns. Further, no relationships were evident between DOC and gill raker number, eye width, pectoral fin dimensions, or pectoral fin insertion angle in univariate analyses. These variable outcomes suggest that selection linked to DOC does not map neatly onto the classic benthic–limnetic axis, that high DOC favors a benthic–limnetic generalist rather than a limnetic specialist, or that the benthic–limnetic morphological dichotomy is less clear and universal than is often suggested.

A Critical Review of Recent Development in Li-Ion Battery Cooling Using Advance Phase Change Materials

Electric vehicles (EVs) can significantly reduce the greenhouse gas emissions, compared to traditional fuel vehicles and also effectively reduced the severe increasing pollution from transportation sector. EVs technology are the alternative of petrol/diesel vehicles, however performance of the power batteries in the major concerns. Li-ion battery (LiBs) are very sensitive to the temperature, which drastically affect the lifespan, thermal performance and safety. Battery thermal management (BTMSs) in thus an essential and it can considerably decrease the adversative effect of high battery cells temperature. In this regard, this work presents a detailed review of BTMSs using phase change materials (PCMs), including metal-foam based PCM, nano-particles dispersed PCM and fin insertion in PCM. It is found that the PCM through utilization of nano-particles possesses excellent thermal properties for effective heat dissipation of the battery pack and highly advantageous. In future, advanced BTMS for fast-charging EVs working at high temperature, hydride BTMS through utilization of heat pipes with forced air cooling and nano-particles will be advantageous. The tactic presented for battery cooling herein can be utilized by the EV industry in fast-charging based vehicle conditions.

Discharging process and thermal evaluation in the thermal energy storage system with fractal tree-like fins

Under microgravity environment for spacecraft operation, the melting rate of phase change material is restricted by its low heat transfer performance and disappearance of natural convection. To accelerate the melting under microgravity, the insertion of fractal tree-like fins into a latent heat thermal energy storage unit is proposed. The dynamic melting behavior and heat transfer performance in cavities with fractal tree-like fins having bifurcation angle of 30°, 60° and 90° are investigated through a transient model based on the enthalpy-porosity method. The relationship between the effects of tree-like fins and thermocapillary convection on melting is disclosed. The results show that during melting driven by combined heat conduction and thermocapillary convection, the presence of tree-like fins significantly accelerates melting, and the increment degree of melting rate increases with the increase of bifurcation angle. Compared with cavity without fin, 30°, 60° and 90° fins reduce melting time by 47.7%, 57.2% and 64.3%, respectively. The fractal tree-like fins also enhance the increment speed of energy storage capacity, while enhancing and slightly deteriorating heat transfer at the beginning and end of melting, respectively. The thermocapillary convection accelerates the melting under microgravity, and the acceleration effect degree increases with the increase of bifurcation angle. With the presence of natural convection, compared with the cavity without fin, 30°, 60° and 90° fins reduce the melting time by 57.8%, 60.6% and 65.3%, respectively; the acceleration effect of fins on melting is enhanced, and the effect of bifurcation angle on melting becomes weaker. The present design innovatively introduces tree-like fins into thermal energy storage under microgravity condition, and can be used for temperature control of spacecraft electronic devices.

Two new species of the hillstream loach genus Indoreonectes from the northern Western Ghats of India (Teleostei: Nemacheilidae)

The hill stream loach genus Indoreonectes is endemic to peninsular India south of the Satpura hill ranges and is represented by three species I. evezardi, I. keralensis and I. telanganaensis. Indoreonectes evezardi has been suggested as a species complex based on recent genetic studies; however, due to lack of type material the species delimitation has been difficult. Here we redescribe I. evezardi collected from its type locality and describe two new species from the northern Western Ghats of India. Indoreonectes neeleshi, described from Mula River tributary of Godavari river system, can be diagnosed from all its congeners based on a combination of characters: inner rostral barbel reaching middle of nostril; maxillary barbel reaching midway between eye and posterior border of operculum; dorsal hump behind nape; bars on lateral side of the body wider than inter-bar space; total vertebrae 35 and dorsal fin insertion between 13th and 14th abdominal vertebrae. Indoreonectes rajeevi, described from Hiranyakeshi River of the Krishna river system, differs from all its congeners based on a combination of characters: inner rostral barbel reaching anterior margin of eye; maxillary barbel reaching posterior border of operculum; conspicuous black markings on lower lip, dorsal hump absent; total vertebrae 36 and dorsal fin insertion between 12th and 13th abdominal vertebrae. Further, I. neeleshi differs from its congeners by the raw genetic distance of 6.8–14.4% for the cox1 gene and 5.7–16.2% for the cytb gene, while I. rajeevi differs from its congeners by the raw genetic distance of 10.9–14.0% for the cox1 gene and 11.8–15.8% for the cytb gene.

Topographic Variations in Mobilization of Blubber in Relation to Changes in Body Mass in Short-Finned Pilot Whales (Globicephala macrorhynchus)

AbstractFat-level measurements used to indicate individual body condition and fitness are useful only when taken at a region along the body where fat responds to variations in caloric intake. Investigations to identify appropriate species-specific regions are limited, especially for cetaceans that have a specialized fat (blubber) that serves as an energy reserve and provides insulation. Over 18 mo, body mass of six pilot whales varied (range: 50-172 kg), and although caloric intake increased when water temperatures were lower, generally the best-fitting state-space model for length-adjusted mass was based on a single factor, caloric intake. After correcting for body length (range: 330-447 cm), the slope for thickness and blubber ring thickness (average thickness along a girth) in relation to body mass was positive and had a P value of <0.10 at six of 16 measurement sites and one of five girth measurement sites, respectively. The slope for body girth (a reflection of changes in underlying thickness) in relation to body mass was positive and had a lower P value ([Formula: see text]) at three of five girth measurement sites. Results indicate that from the anterior insertion of the pectoral fins to the posterior insertion of the dorsal fin is the most metabolically active region. This region includes the midflank site, a location where thickness measurements have historically been taken to monitor cetacean body condition. Conversely, in the peduncle region was comparatively inert. These findings must be considered when measuring thickness and body width (i.e., photogrammetry) to monitor the condition of free-ranging cetaceans.

Microevolutionary change in viscerocranial bones under congeneric sympatry in the Lake Tanganyikan cichlid genus Tropheus

The endemic Lake Tanganyika cichlid genus Tropheus lives at rocky shores all around the lake and comprises six species which are subdivided into about 120 morphologically similar but color-wise distinct populations. Typically, they live without a second Tropheus species, but there are some regions where two or even three sister species live in sympatry. We previously showed that there are morphological differences concerning head shape, eye size and insertion of fins among populations living alone compared to those living in sympatry with a second Tropheus. This study goes one step further to test if sympatry affects the shape of viscerocranial bones. By means of geometric morphometrics, we compare the shape of four bones among thirteen Tropheus populations, some of which in sympatry and some living alone. We quantify patterns of shape variation and estimate morphological disparity among the four bony elements in the study species and populations. We found consistent differences in the shape of one bony element among non-sympatric and sympatric populations, besides an extensive variation in the shape of viscerocranial bones within and among species. Furthermore, sexual dimorphism in Tropheus is clearly evident in the viscerocranial bones analyzed. We suggest that the relatively subtle morphological signal in sympatric vs. non-sympatric Tropheus populations is owed to the fact that the depth segregation does not yet represent a full shift in the trophic niche, albeit our data confirm that differences in ecologically relevant traits, such as bones of the preorbital region, play an important role in the process of niche separation and in the context of explosive diversification of cichlid fishes.

Comparison of different approaches for thermal performance improvement of a phase change energy storage system

Performance improvement of a phase change material (PCM) thermal storage system is numerically investigated. A finite volume solver is employed to simulate the melting process of the PCM in different geometrical and boundary conditions. The numerical predictions are initially validated against available experimental data. Afterward, four different scenarios are investigated to improve the thermal characteristics of the phase change process. These scenarios include insertion of radial fins with different radial lengths, insertion of a porous layer on the PCM side of the heat transfer fluid (HTF) tube, doubling the HTF mass flow rate, and also increasing the HTF inlet temperature. The results indicate that all of these scenarios expedite the melting process, but at different rates. The insertion of the porous medium is shown to be more effective than using of radial fins. Moreover, according to the second-law analysis of the thermal storage system, using the porous layer provides a superior exergy efficiency compared to other enhancement scenarios. Overall, the addition of a metallic porous layer around the HTF tube is proven to be the most effective as well as the most efficient approach to improve the thermal characteristics of the energy storage system.

Recent progress in phase change materials storage containers: Geometries, design considerations and heat transfer improvement methods

• The different geometries of PCM storage containers and their design considerations are presented. • Recent advances of different heat transfer improvement techniques in PCM storage containers are reviewed. • Various designs of PCM-finned storage systems and their key design parameters are deeply discussed. • Discussions for current systems design and recommendations for future research are illustrated. The potential for phase change materials (PCMs) has a vital role in thermal energy storage (TES) applications and energy management strategies. Nevertheless, these materials suffer from their low thermal conductivity and hence heat transfer enhancement techniques should be applied to enhance their thermophysical properties. This review focuses on the geometrical configurations of PCM containers and their design considerations, aims to improve the performance of TES systems. Various methods for enhancing heat transfer of PCMs (the main challenge in container design) include microencapsulated PCMs, insertion of fins, the combination of fins and nanoparticles, the use of metal foams and graphite, and the doping of high photothermal materials are also extensively discussed as well. Moreover, this paper highlights various designs of PCM-finned storage systems and discusses deeply their key parameters to find out the suitable design for optimum melting and solidification rate of PCM. The reviewed results showed that the rectangular PCM container is the effective container for the bulk storage due to its high melting rate and storage efficiency. Moreover, the use of longitudinal finned geometry within PCM integrated triplex tube heat storage units significantly achieved better heat transfer performance compared to the other finned geometries. Additionally, the improvement of the heat transfer of PCM by the deployment of fins is more effective than the hybrid combination of fins and nanoparticles. Further optimization and experimental studies are recommended to explore new hybrid compound intensification techniques such as the triple combination of fins, expanded graphite, and heat pipes with multiple PCMs that augment the thermal performance of TES systems.

Performance evaluation on the gradient design of pore parameters for metal foam and pin fin-metal foam hybrid structure

This paper reported a study on the heat transfer in solidification of phase change materials (PCMs) embedded in metal foam. Heat transfer enhancement techniques are addressed in solidification including the insertion of pin fins and gradient design of pore parameters. Numerical models to describe the transient phase change heat transfer are established through the volume-averaged theory. One-temperature model is accounted for under the core assumption of local thermal equilibrium state. An experimental test rig is designed and established to verify the feasibility of the built numerical models by means of comparing solidification fronts and temperatures at PCM. The effects of gradients in parent materials, porosity and pore density for metal foam upon solidification behavior in metal foam and pin fin-metal foam hybrid structures are quantified. The contribution of local natural convection to the solidification behavior is justified and found this effect can be safely neglected for simulation on solidification in metal foam. Results demonstrate that the insertion of pin fins notably improve the solidification in metal foam regardless of gradient in pore parameters. The gradient in porosity rather than parent materials for the pin fin-metal foam hybrid structures can further improve the solidification rate. As for metal foam, both gradient in parent materials and graded porosity can significantly promote the solidification. The best heat transfer structure is recommend to be a pin fin-metal foam hybrid structure with gradient in metal foam porosity, outperforming other competing heat transfer techniques including pin fins or metal foam.

Optimal hydrothermal design of internal flow pipe with insertion of straight and helical metal foam fins

AbstractIn this paper, the hydrothermal performance of a tubular heat exchanger is developed numerically by inserting metallic foam fins (MFF) in several configurations: straight single‐, single‐helical, and double‐helical MFF. The working fluid is water, whereas the volume of the MFF is kept constant throughout the whole manuscript. The geometric parameters investigated here are the aspect ratio of the rectangular porous fin, the number of turns of the fin, the number of fins, and the pores per inch for a wide range of laminar Reynolds number. The finite volume method is adopted for solving the governing equations of the laminar flow regime. The results are presented in terms of Nusselt number, friction factor, hydrothermal performance (JF), velocity, and temperature contours. The results show that the heat transfer of the smooth pipe is enhanced when a straight MFF is used. More heat removal enhancement is recorded when the MFF is twisted helically with the circumference of the pipe. Additional thermal augmentation is observed with an increase in the number of turns of the helical MFF up to a certain value. Unexpected heat transfer enhancement is recorded when a double‐helical MFF is used instead of a single‐helical one. The maximum enhancement in the JF observed is 1.7 using double‐helical MFF with two turns.