Copper Fins Research Articles

Experimental Study of a Silica Sand Sensible Heat Storage System Enhanced by Fins

This study aims to assess the thermal performance of silica sand as a heat storage medium within a shell-and-tube sensible heat storage thermal energy system that operates using water as the heat transfer fluid. Two types of silica sand were analyzed, fine sand and coarse sand, to determine which was the best for heat transfer and storage. It was found that the fine sand, which had smaller particles compared to the coarse sand, enhanced the heat transfer in the system. The fine sand required 11.86 h to charge using the benchmark case and 17.58 h to discharge, whereas the coarse sand required 13.36 h to charge and 16.55 h to discharge. Methods of enhancement are also explored by comparing the system performance with the inclusion of four different configurations of copper fins to investigate against a benchmark case without fins in the system with fine sand. When equipped with four radial fins, the system demonstrated a significant enhancement, reducing charging and discharging times by 59.02% and 69.17%, respectively, compared to the baseline. Moreover, the system exhibited an even greater improvement with eight radial fins, cutting charging and discharging times by 63.74% and 78.5%, respectively, surpassing the improvements achieved with four radial fins. The ten annular fins decreased the charging time by 42.58% and the discharge by 62.4%, whereas the twenty annular fins decreased the charging by 56.24% and the discharging by 68.26% when compared to the baseline.

A Spray-Deposited Modified Silica Film on Selective Coatings for Low-Cost Solar Collectors

Solar collectors represent an attractive green technology for water heating, where sunlight is efficiently absorbed by a selective coating and the generated heat is transferred to water. In this work, the improvement and scale-up of an electrodeposited black nickel selective coating with a modified silica (MS) film deposited by spray pyrolysis are reported. The MS material was prepared by the sol–gel method using tetraethyl orthosilicate with the addition of n-propyl triethoxysilane to obtain a porous film with an adequate refractive index and enhanced flexibility. The reflectance of electrodeposited selective coatings was characterized with and without the MS film and compared to a commercially available coating of black paint. The MS film increased the solar absorptance from 89% to 93% while maintaining a much lower thermal emittance than the painted coating. The reflectance of the MS film remained unchanged after prolonged thermal treatment at 200 °C (200 h). The fabrication process was scaled up to 193 cm × 12 cm copper fins, which were incorporated in commercial-size flat-plate solar collectors. Three complete collectors of an area of 1.7 m2 were fabricated and their performance was evaluated under outdoor conditions. The results show that the electrodeposited selective coating with the MS film outperformed both the commercial black paint system and the system without the modified silica film.

Enhancing conical solar still performance using high conductive hollow cylindrical copper fins embedded by PCM

The present study aims to enhance the efficiency of the conical solar distiller in producing water during both day and night. This will be achieved through design enhancements, such as increasing the surface area of the distiller to maximize solar energy absorption and improve condensation rates. High thermal-conductivity cylindrical fins have been used, and their role will be investigated. These fins may be hollow and extended, with or without the inclusion of phase change material (PCM). Consequently, copper tubes are positioned at the base of the distiller basin, both with and without the inclusion of phase-changing paraffin wax material inside the hollow tubes. A comparison is made between the performance of three configurations: the first configuration is traditional, the second configuration includes fins without the incorporation of PCM, and the third configuration includes PCM-based fins. This comparison is crucial as it provides a clear understanding of the impact of each design enhancement on the distiller’s performance. The study findings indicated that the arrangement with hollow fins filled with PCM had the highest level of freshwater output. Furthermore, the results showed that the combined output of conical solar distillers equipped with fins made of copper tubes, both with and without PCM, were 7.50 and 6.75 L/m2/day, respectively. The cumulative production of conventional conical distillers is 4.85 L/m2/day. Freshwater output improved by 54.64 and 39.17 % when using hollow copper tubes with and without PCM within 24 h, compared with the conventional configuration. During night-time hours, it was observed that the freshwater output of distilled water from salt water significantly improved by 550 % when utilizing copper tubes loaded with PCM, compared to distillation using empty copper tubes. The maximum daily efficiency of conical distillers with fins with and without PCM were 73.6 % and 80.3 %, respectively. These results showed that conical distillers using copper tubes hollow filled with PCM represent good options for obtaining higher performance than distillation.

Modeling of a metal hydride energy storage tank dynamics using hybrid numerical, experimental, and machine learning methods

This study presents an integrated analysis combining numerical simulations, experimental investigations, and machine learning models to simulate the performance of metal hydride systems for hydrogen storage under various conditions by using a LaNi5 metal hydride cylindrical tank of 500 NL capacity, with a focus on PCM thermal enhancements and surface water heating and cooling. Numerical simulations offer insights into thermal and reaction dynamics, while experimental data are used for model validation and supplemented with additional numerical data for training a FFNN model to predict dynamic hydrogen flow, surface temperature, and surface heat flux. The obtained mean RMSEs for charging/discharging experimental data is 2.8 SOC% for the state of charge and 0.3 °C for surface temperatures. The study compares the effectiveness of water cooling and heating in metal hydride surface across different temperatures, highlighting their impact on the efficiency of hydrogen absorption and desorption processes. Energy consumption is shown to be non-linear; during charging, heat flux peaks before decreases rapidly within around 0.2 h. During discharging, heat flux rises steadily. The study also explores the impact of adding copper fins to the PCM covering metal hydride system, revealing significant improvements in charging and discharging efficiency, specifically, the integration of 16 copper fins led to a notable decrease in complete charging time from approximately 6.5 h to just over 5.2 h, and in complete discharging time from around 4.5 h to under 3.96 h. Using PCM, the highest heat flux is 5 times less during charge and 2 times less during discharge than that for water cooling mode.

Enhancing the melting rate of RT42 paraffin wax in a square cell with varied copper fin lengths and orientations: A numerical simulation

Latent thermal energy storage units are especially preferred in renewable thermal energy systems for their significant capacity to store heat. Nevertheless, the phase change materials in these units have low thermal conductivity, prompting researchers to tackle this problem using several methods, such as incorporating fins. This numerical study contributes to improving the charging rate of a square cell (50 × 50 mm) used paraffin wax RT42 as phase change material by adding 4 copper fins inside, 1 mm thick and of different lengths. The fins were positioned on the left wall, where a constant-temperature heat flux was applied, while the other walls were thermally insulated. Four configurations of the cell were examined: without fins, with 10 mm length fins, with 20 mm length fins, and with 30 mm length fins, respectively. The results demonstrated that the presence of fins significantly improved the charging rate of the square cell. Compared to the baseline configuration without fins, the time required for the paraffin wax RT42 to completely melt was reduced by 22.22 %, 33.33 %, and 55.56 % with fins of 10 mm, 20 mm, and 30 mm lengths, respectively. Configuration four was also compared with a setup where similar fins were positioned on the bottom wall while maintaining the heat flux on the left wall. It was observed that the total melting time doubled compared to configuration four, suggesting that the optimal placement for the heat flux is on the wall where the fins are located. The study contributes to enhancing and developing the charge rates of square and rectangular PCM cells such as these used for cooling PV panels.

Numerical investigations on thermal performance of PCM-based lithium-ion battery thermal management system equipped with advanced honeycomb structures

Electric vehicles (EVs) have a key role in reducing the greenhouse gas emissions contributed by the transportation sector. Lithium-ion (Li-ion) battery which is composed of different cells is the major component in EV, that serves as the power source due to its superior performance. Battery thermal management systems (BTMS) are essential to improve the life and performance and to reduce the risk of fire hazards. In the present study, a single Li-ion cell with Phase Change Material (PCM) and fins is numerically modeled. The finite volume-based simulation is used to predict the heat transfer and flow characteristics of the systems at various operating conditions. Three different unconventional honeycomb-shaped finned PCM systems including baseline model are simulated and compared against the case of PCM without fins and simple honeycomb fin. Cell maximum temperature, temperature difference, and PCM liquid fraction are selected as the parameters for the performance comparison among the different finned configurations. A reduction of 2.77% in maximum cell temperature is obtained in a simple honeycomb structure compared to no fin design at 5C discharge conditions. It is also concluded that the three advanced honeycomb structure shows similar thermal performance but shows better performance than simple honeycomb structure. It is found that 1-Tetradecanol and n-Eicosane PCMs reduce the maximum cell temperature by 13.36 K and 11.81 K, respectively, compared to RT-35 PCM at 5C discharge. The results show that the proposed BTMS exhibits maximum performance at 309.15 K ambient temperature with copper fins and 1-Tetradecanol as PCM.

Performance enhancement of evacuated U-tube solar collector integrated with phase change material

In this research, a numerical simulation was undertaken to assess the effectiveness of an Evacuated tube solar collector (ETSC). The study explored the efficacy of merging a parabolic trough solar collector (PTSC) and copper fins into the U-tube ETSC design. Two types of fins, namely annular fins and disk-shaped fins, were evaluated. Additionally, the study aimed to analyze the influence of operational and geometric parameters, such as the heat transfer fluid (HTF) mass flow rate and the U-tube bend radius, on the performance of the U-tube ETSC. Furthermore, a comparative examination was carried out to identify the most suitable type of phase change material (PCM) for the U-tube ETSC. Finally, a comparative analysis was conducted to assess the performance of the U-tube ETSC in comparison to that of the coaxial tubes ETSC. The results clearly demonstrated that the integration of an PTSC, PCM, and disk-shaped fins substantially improved the overall performance of the ETSC in comparison to the conventional solar collector. This improvement led to a remarkable increase in energy efficiency, with an impressive gain of 42.94 %. The ETSC displayed remarkable performance, particularly at lower HTF mass flow rates and a reduced U-tube bend radius, achieving an average HTF temperature of 430 K. Additionally, among the tested PCMs, RT 82 emerged as the most suitable choice, providing an energy gain of 9.27 % in comparison with the case without PCM.

Critical analysis of enhanced photovoltaic thermal systems: a comparative experimental study of PCM, TEG, and nanofluid applications

Phase change materials (PCM), thermoelectric generators (TEG), and nanofluids are popular methods investigated for improving conventional photovoltaic thermal (PVT) systems. These methods are particularly used in warm climates where high temperatures negatively impact photovoltaic (PV) power output and energy efficiency. This experimental study evaluated the effects of 32 °C melting point PCM and TEG integration on PVT units, as well as 42 °C melting point PCM and nanofluid incorporation on concentrated PVT (CPVT) units. Technical, exergetic, and economic performance were compared using a small-scale PVT module. Low-cost commercially available materials were used to construct all PVT units. Industrial metal waste was introduced to enhance the thermal conductivity of paraffin wax and salt hydrate PCMs. The results indicated that applying PCMs, porous media, and concentrator plates increased energy generation, potentially offsetting their higher initial cost and achieving an energy cost of approximately $0.135/kWh. However, TEG and nanofluid implementation remained uneconomical, leading to a 15–35 % increase in energy cost. The water-based CPVT unit, enhanced with paraffin wax and copper fins, demonstrated the best technical performance. This unit achieved electrical, thermal, and exergy efficiencies of approximately 15.5 %, 37.4 %, and 16.7 %, respectively, with more than a 20 % reduction in cell temperature. The study also revealed that severe structural changes caused by corrosion of metallic materials in hydrated PCMs could alter the melting point by more than 30 %. This change negatively impacts heat storage capacity. Conversely, incorporating metal chips in non-hydrated PCMs improved the time to reach the melting point state by 30–60 minutes.

Investigating the performance improvement of lithium-ion battery cooling process using copper fins and phase change materials (PCMs)

This study investigates utilizing phase change materials (PCMs) along with metallic fins for passive cooling of lithium-ion batteries. PCMs have low thermal conductivity, which is enhanced by incorporating copper or aluminum fins. Numerical simulations using ANSYS FLUENT's Solidification & Melting solver in an axisymmetric configuration are performed. PCM cooling outperforms air cooling, providing up to 15 °C lower maximum battery temperatures as long as PCM remains solid. The findings from the analysis of air cooling versus cooling with PCM demonstrate that the use of phase-change materials enhances battery cooling performance for a specific duration, provided that these materials do not fully liquefy. Adding fins further improves cooling for 0.2 mm thickness, 6 copper fins of 11.67 mm height give optimal performance with 8 °C lower peak temperatures than without fins. Copper fins outperform aluminum due to 60 % higher thermal conductivity but have 3X higher density. For longitudinal fins, 4 fins of 10 mm height perform better than 10 fins of 3 mm height. With high conductivity PCMs like paraffin wax (0.242 W/m.K), varying fin count has minimal impact as heat distributes rapidly. This study establishes guidelines for optimizing PCM-fin geometries and materials to maximize passive lithium-ion battery cooling performance.

The relationship between thermal management methods and hydrogen storage performance of the metal hydride tank

Solid-state hydrogen storage tanks are key equipment for fuel cell vehicles and hydrogen storage. However, the low heat transfer properties of hydrogen storage tanks result in the inability to meet the hydrogen supply requirements of fuel cells. In this study, different thermal management approaches were explored through the design of LaNi5-based solid-state hydrogen storage tanks. We experimentally studied the effects of different internal heat transfer methods, that is, expanded natural graphite (ENG), copper foam, and copper fins on the hydrogen absorption and desorption performance. We also studied the effects of external cooling methods with natural convection, air cooling, and water cooling, respectively. Under the same external cooling method of natural convection, a solid hydrogen storage tank filled with 5 wt.% ENG has similar performance to a tank filled with copper foam. Compared to natural convection, air and water cooling can significantly improve the heating performance of metal hydride (MH) beds by increasing the external heat transfer coefficient. The effect of water cooling is better than that of air cooling, and in these two enhanced performance conditions, the tank filled with copper foam performs better than with ENG. In the case of water cooling, by adding copper fins to a hydrogen storage tank filled with 5 wt.% ENG, the tank was saturated with hydrogen absorption in only 29.4 min, which is 55.6 % shorter than the hydrogen uptake time in a hydrogen storage reactor without copper fins. And its stable hydrogen desorption (1 NL/min) has reached 98.1 % of the total hydrogen released. The results show that the effective thermal conductivity and heat transfer area of metal hydride bed play key roles in improving heat transfer and reaction rate. In addition, heat transfer is more important than mass transfer to improve the performance of the hydrogen storage tank.

Parametric investigation of battery thermal management system with phase change material, metal foam, and fins; utilizing CFD and ANN models

The focus on developing an effective battery thermal management system (BTMS) to maintain optimal temperatures for lithium-ion batteries (LIBs), especially in electric vehicle (EV) applications, has grown significantly. The effective BTMS not only enhances the cooling performance of LIBs but also contributes to increased passenger safety and mileage of EVs. This study investigates BTMS configurations with fins, metal foam, and phase change material (PCM) to minimize temperature of battery during 3C discharging in varying conditions. Additionally, the study explores the impact of different BTMS material combinations and various fins lengths on system performance as a parametric investigation. Moreover, to streamline the analysis process and introduce novelty, artificial intelligence is explored as an alternative to computational fluid dynamics for predicting liquid fraction of PCM and temperature of battery, enhancing the innovative aspect of this study. Numerical simulations, using a non-equilibrium thermal model for metal foam modeling, reveal that the fourth case, integrating all three passive approaches, maintains the lowest temperature and enhances LIB cooling. The optimum BTMS shows a reduction of 3 K compared to BTMS utilizing pure PCM. During discharge process, the temperature difference in the battery decreases by approximately 75 % and 66 % in the fourth case compared to the first case (with pure PCM) under normal and harsh environmental conditions, respectively. Applying copper metal foam and copper fins yields the best results in reducing battery temperature. Increasing the length of fins and adding more fins effectively lower the battery temperature. Finally, an artificial neural network model is developed using the backpropagation learning technique coupled with the gradient descent optimization algorithm. The model exhibits excellent predictive capabilities, achieving high R-squared values of 0.98 for PCM liquid fraction and 0.99 for battery temperature.

Impact of fin material properties and the inclination angle on the thermal efficiency of evacuated tube solar water heater: An experimental study

In recent years, evacuated tube solar water heaters (ETSWH) have become popular due to their efficiency and low maintenance based on trends in India's solar thermal market. Numerous studies have focused on improving system performance. In the scientific literature, there is a lack of information on the selection of appropriate fin material and the benefits associated with it. The thermal efficiency (ηt) of ETSWH is directly impacted by the choice of fin material. In this context, the goal of this study was to assess the impact of copper and aluminum using fin material as well as the inclination angle on ETSWH's ηt. The experiments are conducted for mass flow rate (mwt) varying from 2 to 5l/h. With a mwt of 2l/h, the highest outlet temperature of 55°C was recorded, while the highest ηt was found at 41.2°C with a mwt of 5l/h. At all mwt, copper fin is more efficient than aluminum fin due to their superior thermal conductivity. Among the considered inclination angles, at an inclination angle of 30°, the efficiency of ETSWH is found to be optimal. ETSWH with a copper fin attains (ηt = 58.57%), which is more significant than the case when the aluminum fin is used (ηt = 51.50%).

Experimental investigation of axial finned tube evaporator thermal distillation system using for diesel engine waste heat recovery process

The study aims to improve the waste thermal energy retrieval from flue gas of an internal combustion engine (ICE). The recovered waste heat energy was used for distillation by using a thermal distillation system. The performance of the thermal distillation unit was investigated by varying the evaporator (boiler) type and engine load (25, 50, 75 %). Four different types of boilers were used including one smooth copper tube and other three were two, three and four axial finned copper tube evaporators. The impact of boiler type and engine load on the net retrieved energy and exergy, net energy and exergy efficiency, and distillate yield rate of thermal distillation unit was also examined. The results showed that the net extracted heat energy and exergy for axial finned tube evaporator was approximately 26.823 – 45.513 % and 7.614 – 25.203 W higher than that of smooth tubes evaporator at 25 and 75 % engine load, respectively. The distillation yield was found to be ~ 2.35 liter/ hour in the case of four axial finned tube boiler at 75 % engine load.

Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.

Sustainable freshwater production using novel cascade solar still with phase change material, serpentine water path, and copper fins.

Heat losses in solar stills are high, which has led to a decrease in their thermal efficiency. Also, the production of these devices is limited to the presence of the sun, and their production stops during cloudy hours or at night. To solve these problems, in this experimental study, two cascade solar stills are examined under relatively similar conditions for sustainable freshwater production. One of these solar stills is modified with the phase change material and copper fins, and another one is a conventional cascade solar still without using the phase change material and copper fins. Paraffin was selected as a heat storage material to increase the time of desalination of water by the solar still. In addition, the copper fins are used to increase the conduction heat transfer in phase change material and provide better melting and solidification processes. To prolong the water path along the steps, the serpentine water path was considered. The results showed that at sunset hours, desalination efficiency with phase changing material and fins was increased. At 5 pm, the efficiency of the modified device was increased by 29% (on average) as compared to the conventional solar still without using phase changing material and fins. The rate of water production in conventional solar still in midday was higher compared to the modified solar still. However, in the sunset and night hours, the modified solar still has a higher production rate due to heat released from the thermal storage system.

Cupric oxide nanofluid influenced parabolic trough solar collector: thermal performance evaluation

ABSTRACT The availability of solar radiation has potential for energy applications, and recently, the parabolic trough collector (PTC) plays a crucial role in heat exchanger applications. The conventional system lacked thermal performance, reducing heat transfer coefficient and thermal efficiency. With this, the main goal of the research is to attempt to enrich the overall thermal capacity of the PTC system by introducing triangular copper fins and CuO nanoparticles (10–20 nm). During the experimental evaluation, the different concentrations (0.1, 0.2, and 0.3%) of CuO blended with water (nanofluid) are permitted to circulate the receiver boundary configured with PTC setup 3.5 m2 at the flow rate of 0.12 kg/s. Effects of CuO nanofluid concentrations on heat gain, heat transfer coefficient, and thermal and exergy efficiency of the system are measured and spot the optimum heat gain of 689.9Wm enriched heat transfer coefficient of 172.3 W/m2K, maximum thermal and exergy efficiency of 70.9% and 37.2% respectively.

Impact of sensible storage material and copper fins on the performance of serpentine tube type vacuum tube collector system: Energy, technical and financial assessment

This paper offers an experimental evaluation of an SR-EVTC (serpentine evacuated tube collector) system embedded with a copper annular fin and sensible heat storage liquid (SR-EVTC/SS-AF). In this study developed system was compared with the control EVTC (SR-EVTC/CS) under the same meteorological conditions. In addition, the technical and financial feasibility of SR-EVTC/SS-AF and SR-EVTC/CS in different locations of India was also assessed for their practical implementation and commercial viability. To determine their thermal performance, the developed systems were investigated during sunny and cloudy days for three different water flow ranges, i.e. 0.008, 0.012, and 0.016 m3/h. During the experimental investigation on clear sunny days, both SR-EVTC/SS-AF and SR-EVTC/CS were found to have the highest daily average energy efficiency of 82.45 % and 63.88 %, respectively, when the flow rate was 0.016 m3/h. Whereas during cloudy days, the highest value of daily energy efficiency was achieved to be 87.78 % and 74.35 % respectively for EVTC/SS and EVTC/WSS, when the flow rate was 0.008 m3/h.It has been noticed that on average, the same amount of solar radiation is incident at Location-I and Location-V. However, due to the lowest ambient temperature, the annual energy demand at Location-V is found to be the highest. For SR-EVTC/SS-AF, values of PBP and LCSWH are found to be lowest for Location-I due to the lowest ratio of annual energy requirement to average the annual solar irradiation incident, whereas the value of NPW is highest for Location-V due to the highest annual energy demand.

Saturated water flow boiling heat transfer and pressure drop in scalably microstructured plain and finned copper tubes

Well established understanding of flow boiling heat transfer and its hydrodynamic driving mechanisms have led to the inception of surface geometry augmentation techniques that can enhance thermal-hydraulic performance. Enhancing the flow boiling heat transfer at a reasonable pressure drop enables the deployment of more compact and efficient heat exchangers and thermal systems. To enable ease of manufacturing, simplicity, and reliability, passive augmentation techniques that do not require external stimuli are preferred. In this study, a scalable copper microstructuring technique was developed on both smooth and internally finned 0.25” tubes to investigate how it affects the thermofluidic behavior of relatively higher surface tension water during saturated flow boiling. The internally finned tubes used in this study comprised of 50 fins with a helical angle of 13°. To apply the conformal microstructures on the internal tube surfaces, chemical oxidation via an alkaline mixture was used, resulting in structures having characteristic length scales approaching 200 nm −1 µm. Our results show that microstructuring of plain copper tubes provides a water flow boiling heat transfer coefficient enhancement ranging from 10 % to 90 % compared to untreated specimens for vapor qualities ranging from 0 to 0.1 and mass flow rates ranging from 255 to 485 kg/(m2·s). Augmentation is attributed to the increased roughness of the plain copper tubes that creates additional nucleation sites for enhanced liquid entrapment and increases wettability. Associated with this heat transfer augmentation is an increased pressure drop ranging from 0.5 % to 38 % relative to untreated tubes due to the increased skin friction as well as add fluid flow disruption. Overall, the performance factor ranged between 0.86 to 1.81 demonstrating that the augmentation in heat transfer overshadowed the increase in pressure drop. Interestingly, applying the conformal microstructures on internally finned copper tubes decreased the heat transfer coefficient and pressure drop by as much as 75 % and 45 %, respectively, when compared to the un-structured finned copper tubes counterparts. The decrease in heat transfer performance and pressure drop was attributed to partial wetting of the fin roots due to the presence of a vapor layer near the inner tube walls. Our work develops a mechanistic understanding of the role that microstructures play during flow boiling of water on industrially applicable smooth and finned tube geometries and designs.

Solar photovoltaic-thermal system with novel design of tube containing eco-friendly nanofluid

In photovoltaic (PV) solar systems, electricity can be produced from part of the sunlight and the remaining energy raises the temperature. The aim of the current investigation is to suggest a novel design for the heat transfer tube's (HTT) cross section for overcoming this challenge in photovoltaic/thermal (PVT) systems. In this numerical simulation, the range of fluid inlet velocity (Vin) was set between 0.01 and 0.18 m/s. The value of ambient temperature (Tamb) and fluid inlet temperature (Tin) is 30 °C, and solar radiation (G) has been adjusted to 800 W/m2. A comparison was made between the circular tube and the 8-lobed tube with the same hydraulic diameter, and the better performance of the 8-lobed tube was proved. To meet the increased efficiency of the PVT system, copper fins with four different arrangements were employed. The highest efficiency occurred when the fins were placed all around the inside of the HTT. To create heat transfer fluid (HTF), non-toxic graphene nanoplatelets (GNP) have been mixed with water involving two weight fractions (0.025 % and 0.1 %). Examining the effect of changing the fluid inlet velocity (Vin), it was concluded that the system's electrical performance is increased by 5.8 %, with rise of Vin, in the best case. By using the GNP nanoplatelets (0.1 %), at Re = 1611, the maximum exergy, electrical, and thermal performances of the unit were 15.32 %, 14.05 %, and 55.22 %, respectively, in the best case. In the best case, more carbon dioxide (about 7.1 Tons) can be reduced and the carbon credit is 5.5 % higher than that of base case. In addition, the payback period is less than 2 years in the best case with 18700$ profit in the 10th year.

Design and optimization of metal hydride reactor with phase change material using fin factor for hydrogen storage

The solid-state hydrogen storage in metal hydride (MH) is safer and energy efficient than the gaseous and liquid storage methods. The absorption of hydrogen in MH is highly exothermic. Hence, a good heat management system is required to increase the charging rate. The phase change material (PCM) can be integrated into the reactor to reuse the absorption heat for hydrogen desorption. The present numerical study models the concentric cylindrical reactor with magnesium (Mg) as MH surrounded by sodium nitrate (NaNO3) as PCM using COMSOL Multiphysics v6.1. The effect of buoyancy inside the PCM domain is investigated. An iterative approach is used to determine the required amount of PCM. Copper fins are added inside both MH and PCM. The effect of the number of fins, corresponding fin thickness and pitch on hydrogen absorption are determined to optimize the MH reactor. The outcomes reveal that the hydrogen absorption rate increases with fin numbers. The reactor with 10 and 30 fins takes 86.5 and 97.3 % less time than without fins for 90 % hydrogen absorption, respectively. The novel approach is proposed to estimate the fin efficiency (ηf) using temperature profiles of MH and fin during prevailing unsteady heat and mass transfer. The fin factor (Ff) is presented using the ηf and mass of MH. The performance evaluation criterion (PEC) is discussed based on hydrogen absorption relative to the system's weight. Further, the effect of operating parameters like hydrogen supply pressure and the initial temperature is studied on the reactor performance.