Forced Air Convection Research Articles

A combined experimental-mathematical study on the kinetics of dry ice sublimation under different airflow velocities and blowing modes

The sublimation rate of dry ice, crucial for its cooling performance, is typically influenced by environmental temperature, pressure, and specific surface area. However, the effect of wind speed under forced air convection is not well understood, and current sublimation kinetic models inadequately capture this influence, leading to discrepancies between simulations and experiments. This study examines the sublimation kinetics of static dry ice particles under varying wind speeds and blowing modes. A mathematical model was developed to determine the sublimation kinetic parameters by integrating the Clausius-Clapeyron equation, mass transfer theory, and hybrid particle swarm optimization (HPSO) algorithm. These parameters were then used to create a cooling model for a small insulated box, and the results were validated against experimental data. The findings show that increasing wind speed enhances the sublimation rate of dry ice, with upward-blowing conditions resulting in higher rates than side-blowing conditions. The model’s predictions closely match experimental data, with a maximum mass change deviation of less than 3 % and a maximum temperature deviation of less than 4 °C, demonstrating high reliability.

Effects of corrugation on convective heat transfer and power generation in a wavy walled triangular cavity equipped with inclined elastic fin and piezo-energy harvester assembly

Piezoelectric energy harvesters are one of the energy conversion technologies that can be used to convert a variety of external sources, including wind, fluid motion, and vibrations, into electrical energy. This work suggests a novel wall corrugation design in addition to an elastic fin piezo assembly arrangement for power generation and thermal management in a triangular cavity during turbulent forced convection of air. Using the finite element method with ALE, the analysis is conducted for different values of fin inclination (γ between 0 and 60), corrugation amplitude (Af between 0.01H and 0.06H), corrugation frequency (Nf between 1 and 20) and fin distance from the mid-point of the inclined wall in wall direction. The average Nusselt number (Nu) and generated power (PW) show a non-linear increasing trend with increasing fin tilt. Average Nu increment factor becomes 5.17 with the highest fin inclination while the power increments become 11.6 and 4.46 when rising inclination from 30 to 45 and from 45 to 60. The generated power rises with higher corrugation amplitude and wave number. However, increasing the wave number results in thermal performance degradation. Increment of average Nu becomes 1.17 with highest corrugation amplitude while it declines by a factor of 10.3 at the highest wave number. Power enhancement factors of 5.73 and 2.32 are obtained by increasing the corrugation amplitude from Af = 0.0714H to Af = 0.1786H and from Af = 0.1786H to Af = 0.2143H. When fin positions sf = 0.7143H and sf = -0.7143H are compared with the case of fin location at sf = 0, the power increment factors become 12.27 and 4.76, respectively. For the power produced by the piezo device, a polynomial type correlation is suggested by adjusting the parameters of the corrugated wall.

Performance evaluation of enhanced clustered latent heat system for air heater using modified organic material

The present work evaluates a new model of clustered latent heat storage unit (LHSU) which specifically designed for air heater. The system involves multi-tank which is arranged in staggered configuration. The clustered system uses direct charge for heating the storage material and employs forced air convection for heat liberation. The maximum temperature increment for the heated air is more than 50 %, showing an effective function of the proposed model. This work also analyzes the role of storage material within the system. The stabilized storage material demonstrates a better performance in term of minimum heat loss on the charge stage. Also, it allows for an excellent charge behavior with average of 3.44 °C/min. The LHSU can be combined with an additional fin for accelerating the operation, making the system can be applied flexibly based on the requirement of the energy system. The operation curve is displayed as battery percentage to understand the characteristics of the system during energy interaction. In general, the addition of fin and modified storage material leads to significant improvement, offering the applicability of the proposed model in various technologies for air heater systems.

Study on the flow and heat transfer characteristics inside high-porosity open-cell copper foams: Experimental and numerical explorations

A metal foam with an open-cell structure is a type of material with low flow resistance, high specific surface area, and strong fluid mixing ability. Open-cell metal foams have broad application prospects in electronic component cooling, multiphase heat exchangers, and compact heat exchangers for aerospace applications. This paper presented experimental and numerical analyses of the flow and heat transfer characteristics of five different copper foams under forced air convection. The pores per inch (PPI) of selected foams were 10, 20, 30, 40, and 60, with porosities ranging from 0.968 to 0.973. Analysis of the collected heat transfer and pressure drop data yielded the overall heat transfer coefficient, unit pressure drop, normalized average wall temperature, inertia coefficient, and resistance coefficient. The influence mechanisms of the porosity and flow velocity on heat transfer were analyzed and discussed. The numerical simulation and experiment fitted well. The results showed that increasing porosity led to a significant increase in heat transfer coefficient and unit pressure drop. The 60 PPI foam brought the maximum pressure drop while achieved the minimum thermal resistance.

Optimization of Lithium-ion battery thermal performance using dielectric fluid immersion cooling technique

Lithium-ion batteries (LIBs) are crucial for portable electronics, electric vehicles, and renewable energy systems. However, conventional cooling techniques for LIBs struggle to efficiently dissipate heat during rapid charging and discharging, potentially compromising performance and safety. This study explores the immersion cooling technique to optimize the thermal performance of 4S2P LIB module at 3 C discharge rate. The MSMD-NTGK battery model is utilized in numerical simulation to analyze the electrochemical and thermal characteristics of LIBs. Initially, static and forced convection immersion cooling methods are compared using two different cooling media: ester-oil and air. Static convection with ester oil reduces temperature rise by 8.3 % compared to natural air convection, while forced convection with ester oil achieves optimal temperatures (< 5 °C) at a fluid velocity of 0.077 m/s (20 LPM), lower than forced air convection. Furthermore, the study enhances forced convection with ester oil-based immersion cooling for LIB with different inlet and outlet structural designs. Among these, the middle inlet and middle outlet-center (MIMO-C) flow model demonstrates optimal temperature at reduced flow rate of 5 LPM and minimal pressure drop of 230 Pa compared to others. These findings underscore the potential of forced convection-based immersion cooling to improve LIB performance and lifespan.

Peltier element for real-time heat flux detection in fruit cooling under forced air convection

Peltier element for real-time heat flux detection in fruit cooling under forced air convection

Conjugate heat transfer analysis of the transient thermal discharge of a metallic latent heat storage system

Thermal energy storage systems utilizing metallic phase change materials exhibit great potential as a technology for mobile applications, offering high storage densities and high thermal discharge rates. First experimental investigations show the functionality and performance characteristics of this system. For a deeper understanding of the thermal discharge, this paper presents a numerical model and analysis of the transient conjugate heat transfer. For validation of the numerical model, the results of the simulations are compared to the available experimental data. The investigated storage is based on an aluminum silicon alloy and a box-shaped graphite container design. In this system, heat extraction is achieved by forced convection of ambient air. The transient thermal discharge was simulated from 650 °C to 100 °C, and the solidification of the storage material at around 577 °C was simulated using an enthalpy-porosity approach. The discharge time and total heat flow show good agreement with the experimental data, indicating the model’s successful validation. An empirical study was carried out to determine the thermal contact resistance at the interface between the storage material and the graphite container. The present study contributes new physical insights regarding the thermal discharge of a novel metallic latent heat thermal energy storage system.

Effects of using fireproof thermal management systems on the lifespan of battery cells

The current need, from the point of view of increasing the sustainability of electric vehicles (more and more present in the car market), makes the research in the field to be focused on the analysis of the factors that can lead to an increase electric vehicle batteries' lifespan. Since this is directly related to the temperatures reached during operation and the thermal gradients inside the battery packs, this paper presents the analysis of the cells' lifespan through artificial intelligence methods and techniques, evaluating the influence of the constructive and functional characteristics of two air-based hybrid thermal management systems (CHA - composite material + heat pipe + forced air convection and CTA - composite material + thermoelectric cooler + forced air convection). The construction of the thermal management system is a special and innovative one, being a composite material (epoxy flame-retardant resin and 2 wt% hexagonal boron nitride nanoparticles) chosen as the primary thermal energy dissipation element. The research was carried out experimentally on individual cells and on a battery module (consisting of 12 cylindrical Li-ion 18650 cells), the battery module being discharged at a rate of 3C with the temperatures recorded from 15 locations inside the battery module, which allows assessing the local and global influence of the thermal management systems. Predictions on the lifetime of the cells in the battery module were made using a convolutional neural network and showed that by using the proposed fireproof thermal management systems, the cells’ lifespan increases by 26.9 … 154.4% (depending on the implemented thermal management system and the location of the cell in the battery module).

All-climate battery thermal management system integrating units-assembled phase change material module with forced air convection

Phase change material (PCM) is widely adopted to construct integrated battery thermal management systems (BTMSs) for all climates. However, integrated BTMSs in cylindrical battery modules remain arduous challenges due to the compact/massive cuboid-shaped PCM module and the curved surface of the cells. Herein, we propose a novel all-climate BTMS integrating units-assembled composite PCM (CPCM) module with force air convection. The CPCM module assembled by sleeve-like CPCM units provides developed airflow channels and enlarged heat transfer surface from 1.17 × 10−3 to 3.63 × 10−3 m2 for enhancing convective heat transfer. Consequently, compared to conventional cuboid-shaped module, the thermal resistance of the units-assembled module is remarkably reduced by 52.0% and 60.1%, and the heat flux is enhanced by 7 times under both cooling and preheating modes. In cooling tests, this BTMS demonstrates superior performance by controlling the temperature and temperature difference below 40.30 and 2.80 °C at 3-C discharge, respectively. In preheating tests, it effectively preheats the battery module from 0 to 10 °C in 302 s with a low temperature difference of 3.82 °C. Furthermore, this units-assembled CPCM module saves 53.8 wt% of the CPCM dosage, and thus the energy density of the battery module is increased from 75.6 to 94.4 Wh·kg−1.

Experimental study on 18650 lithium-ion battery-pack cooling system composed of heat pipe and reciprocating air flow with water mist

Lithium-ion batteries (LIBs) are critical power sources for portable devices, electric vehicles, power grids, and energy-storage systems. Effective thermal management is mandatory for achieving optimal battery performance. Although the air-cooling method has been investigated extensively owing to its simple structure, convenient maintenance, and low cost, it is insufficient for cooling large-scale battery packs because of its limited air-cooling capacity and unsatisfactory temperature uniformity. Thus, a reciprocating spray cooling system comprising a reciprocating air flow channel, heat pipe array, and spray nozzle is proposed herein for the efficient cooling of 18,650 LIB packs. The effects of the inlet air speed, spray frequency, and spray duty cycle on the cooling performance of the reciprocating mist cooling system and the corresponding optimal operating parameter range are analyzed. Additionally, the competitive mechanism between forced air convection and evaporative cooling is discussed. The results indicate that, compared with the case of natural convection cooling, the temperature increment of the battery pack decreases by 32.1 % under reciprocating mist cooling. Meanwhile, the maximum temperature difference reduces to approximately 3.41 °C with 3C of discharge. The spray frequency minimally affects the overall heat dissipation but induces surface temperature fluctuations in individual batteries. Increasing the spray duration per 10 s in a single spray duty cycle can reduce the average temperature of the battery pack by approximately 2 °C. Additionally, the power-allocation scheme affects the heat dissipation of the system. Decreasing the flow rate of spray cooling water and increasing the inlet air speed promote the evaporation of water mist inside the system, thus further improving heat dissipation. This study provides new insights into the design of air-cooled thermal management systems for battery packs.

Ways to ensure environmental standards when harmful gaseous substances are released into the atmosphere from drainage networks based on modeling their operation

The issues of physical and mathematical modeling of the operation of a pressure-free drainage pipeline made of polymer material and ceramics are studied in order to prevent negative environmental consequences when harmful and toxic gases are released into the atmosphere of cities from the drainage network. Studies of the dynamics of changes in hydraulic and aerodynamic parameters during the flow of liquid and gas in the subsurface space of a ceramic pipeline are presented. An algorithm for solving the problem based on the calculation of hydrodynamic similarity criteria describing the phenomena of mass transfer as a result of forced air convection by using a mechanical ventilation system of aggressive airborne droplet mass over a water surface is compiled. Based on the results of the operation of a special automated calculation program, the total mass of harmful gases released from the water into the subsurface space of the pipeline, the time of removal of hydrogen sulfide entering the subsurface space in concentrations significantly exceeding their maximum permissible values in the city atmosphere, as well as the time of removal of gaseous substances depending on the filling of water in the gravity pipeline are determined.

A high heat dissipation strategy based on a multi-scale porous hydrogel and heat sink exhibiting cooling capacity comparable to that of forced air convection but with zero energy consumption

A new composite heat sink (CHS) is designed based on a multi-scale porous hydrogel. Owing to the high heat transfer coefficient and zero energy consumption property, the CHS shows great potential in electronic device cooling field.

Numerical Investigation of the Thermal Performance of a Hybrid Phase Change Material and Forced Air Cooling System for a Three-Cell Lithium-Ion Battery Module

The thermal performance of a lithium-ion battery module comprising three cells contained within a casing was investigated at discharge rates of 3C and 5C with three different cooling strategies: forced air, phase-change material (PCM), and a hybrid system using a combination of forced air and the PCM. Three levels of fan speed (5000 rpm; 7000 rpm; and 9000 rpm) for cooling air flow were considered. A numerical simulation of heat transfer was performed using the ANSYS Fluent software. The electrochemical modelling of a battery was developed based on the NTGK approach, and the phase-change phenomenon was treated as an enthesis–porosity problem. The composite PCM, aluminum metal foam embedded in n-octadecane, had better heat dissipation performance than forced air convection. The PCM is significantly more effective at heat dissipation than forced air. Interestingly, when using a hybrid cooling system that combines forced air and a PCM, although it meets the operational requirements for Li-ion batteries in regard to maximum temperature and temperature uniformity at a 3C discharge rate, the airflow appears to have a negligible effect on thermal management and yields an indiscernible change in temperature. This can be attributed to a complex flow pattern that developed in a casing as a result of the suboptimal design of the inlet and outlet. Further studies will be required for the optimal positioning of the inlet and outlet, as well as the effectiveness of combining liquid cooling methods.

Mitigation of thermal runaway in air cooled Li-ion batteries using a novel cell arrangement coupled with air flow improviser: A numerical investigation and optimization

The concept of e-mobility is gaining the utmost importance owing to stringent emission norms. However, the safety issues associated with propulsion batteries are posing a major threat to their success. The occurrences of accidents caused due to thermal runaway in electric two-wheelers grabbed global attention. In this research work, an effort is being taken to address this concern, by arranging the battery cells in a pentagonal arrangement and employing forced air convection. The influence of air velocity (0.15, 0.30, and 0.45 m/s) and air inlet position (60, 75, and 90 mm) and intermediate cell distance (4, 6, and 8 mm) on the thermal performance of the battery is investigated using a numerical approach. Maximum cell temperature, pressure drop across the channel, maximum air velocity, maximum turbulent kinetic energy, and maximum turbulence intensity are considered output responses. A grey relational analysis (GRA) is used to identify the optimum level for all input parameters considering all output responses. The optimal forced convection parameters for the proposed pentagonal cell arrangement are the intermediate cell distance of 6 mm, air velocity of 0.45 m/s, and air inlet position of 90 mm from the center of the cell arrangement. With this arrangement, the peak cell temperature is reduced from 48.32 to 36.83 °C (8%). The study is extended with an airflow improviser to examine the influence of its geometrical parameters (improviser angle, fillet angle, and its distance from the center of the battery module) on the battery cell temperature. At the optimal conditions, the presence of an airflow improviser increases the air velocity from 1.76 to 2.302 m/s (19%) and turbulence intensity from 196 to 0.350 m2/s2 (33%). Thus, the cell temperature could be reduced to the extent of 8.6% by adopting the pentagonal cell arrangement with airflow improviser and optimal operating parameters.

Proposing a Hybrid Thermal Management System Based on Phase Change Material/Metal Foam for Lithium-Ion Batteries

The charging and discharging process of batteries generates a significant amount of heat, which can adversely affect their lifespan and safety. This study aims to enhance the performance of a lithium-ion battery (LIB) pack with a high discharge rate (5C) by proposing a combined battery thermal management system (BTMS) consisting of improved phase change materials (paraffin/aluminum composite) and forced-air convection. Battery thermal performance is simulated using computational fluid dynamics (CFD) to study the effects of heat transfer and flow parameters. To evaluate the impact of essential parameters on the thermal performance of the battery module, temperature uniformity and maximum temperature in the cells are evaluated. For the proposed cooling system, an ambient temperature of 24.5 °C and the application of a 3 mm thick paraffin/aluminum composite showed the best cooling effect. In addition, a 2 m/s inlet velocity with 25 mm cell spacing provided the best cooling performance, thus reducing the maximum temperature. The paraffin can effectively manage thermal parameters maintaining battery temperature stability and uniformity. Simulation results demonstrated that the proposed cooling system combined with forced-air convection, paraffin, and metal foam effectively reduced the maximum temperature and temperature difference in the battery by 308 K and 2.0 K, respectively.

Numerical investigation of form-stable composite phase change material for battery passive cooling

Phase change material (PCM) has gathered much attention in battery thermal management for electric vehicles, in which form-stable PCM is a promising method to reduce the leakage of energy storage material. In this paper, a composite PCM that has form-stable property is used for passive cooling of electric car battery. Three cooling configurations are set up in the gap between two batteries, and their performance is analysed by a numerical model. The results show that integrating composite PCM with forced air convection can maximally prevent battery from heat accumulation at 5C and reduce the core temperature by 15.9 K, while filling the gap with composite PCM can reduce the temperature by 15.7 K. With the discharge rate decreased, forced air convection plays more significant role than PCM in slowing down the rise in battery temperature. The maximum battery temperature reduces when the ratio of PCM thickness to battery width increases from 0 to 0.1, but the maximum temperature is limited to a certain level with thicker PCM. The addition of 4.6 wt% graphite to the composite PCM greatly improved the heat absorption capacity of PCM, and the forced air with 20 m·s-1 velocity has better cooling behaviour than PCM.

Three-dimensional transient CFD modeling of multiple finned aluminum foam heat sinks in a horizontal channel

Finned metal foam heat sinks are well-known because of their excellent performance in cooling of powered electronics. In this study, three-dimensional transient numerical simulations of finned aluminum foam heat sinks in a forced convection of air were carried out using commercial COMSOL. The geometry under consideration consists of an array of finned aluminum foam heat sinks mounted on heater blocks and placed on a plate in a horizontal channel. Heat sink aluminum foam regions were considered as porous media with a local non-equilibrium thermal model to evaluate thermal characteristics, while the Forchheimer-Brinkman extended Darcy model is considered for the flow analysis. Our main concern in the present study is to evaluate the transient thermal–hydraulic behavior and the cooling performance under constant flux heat sources while varying the Reynolds number and variable morphological parameters of the aluminum foam, i.e., porosity (ε) varied from 0.85 to 0.95. The thermal performance ratio and the average Nusselt number of the finned aluminum foam heat sinks are 23.14% and 30%, respectively, larger than the finned aluminum heat sinks. As the Reynolds number increases, the thermal characteristics are enhanced, and the pressure drop is increased. An increase in porosity causes a reduction in heat transfer rate and an elevation of pressure drop.

Effects of control volume outlet variation on axial air cooling of lithium-ion batteries

This paper addresses cylindrical lithium-ion cells' heating and non-uniform cooling by simulating a simple battery pack design with 24 cells and axial airflow. Cooling a battery pack using forced air convection in a rectangular container causes non-homogeneous temperature distribution. The middle cells and the second half of the battery pack (near the exit) get less cooling compared to the cells near the inlet. To solve this issue of non-uniform cooling, in this paper, we propose an optimized Battery Thermal Management System (BTMS) which allows higher amounts of turbulent kinetic energy to be generated near the cells closer to the exit and farther away from the inlet. We attempted to create a narrow region in the middle of the pack which leads to an increase in mixing and turbulence in the airflow. This directs the flow precisely, hence getting rid of dead air flow zones behind the cells. The convergence functions like a nozzle, propelling the air flow into the second half of the battery pack. Using COMSOL Multiphysics, the mixing and turbulence of the airflow, as well as the temperature increase and homogeneity inside the battery pack, are investigated. Three separate investigations are conducted in order to determine the optimal shape for the BTMS control volume as well as to determine the effect of system's inlet pressure and outlet velocity on the cooling performance. Results indicated that the system's temperature decreased significantly by lowering the outlet dimensions and introducing convergence to the BTMS's central area. Increasing outlet velocity increased cooling in a case with a single fan significantly, whereas increasing pressure in a case with two fans increased cooling slightly.

Taguchi optimization and analysis of variance for thermoelectric generators with forced convection air cooling

In recent years, humanity has experienced the effects of using unsustainable energy sources that pollute the environment while being inefficient. Most of the primary energy input used in energy conversion processes is lost in the form of heat. Thermoelectric generators (TEGs) have the potential to recover some of this wasted heat; however, their low energy conversion efficiency needs to be addressed. Previous literature has shown effective optimization of thermoelectric generation systems through statistical tools such as the Taguchi method that optimized all the parameters that affect the outcome of the system. To this date, no research has considered wind speed for convection heat transfer as one of the optimizable parameters. This study aims to optimize the operating conditions of commercially available TEGs that are cooled by forced convection simulating naturally occurring wind speeds and operate under low-quality waste heat temperatures to improve the TEG performance further. Two commercially available TEGs are optimized via the Taguchi method. The Taguchi method is implemented with three parameters and three levels, making an L9 orthogonal array. The objective function is the maximum output power. The optimized parameters are the hot side temperature, the heat sink size, and the wind airspeed. Analysis of variance (ANOVA) is used alongside the Taguchi orthogonal array for the statistical analysis of the results. The optimization results show that the hot side temperature is the most influential parameter to the output power. In addition, the change in the heat sink size also significantly influences the output power, whereas the impact of the wind speed is not as significant. In addition, interaction analysis between the parameters is performed. The Taguchi method yields satisfactory optimization results. The optimized system yields 0.65 W of power at 140 °C hot side temperature, Model K402 heat sink, and 3.7 m·s−1 wind speed. The influence of the air velocity of 1.73% is minimal on the output power compared to the hot side temperature, with a level of influence of 75.67% and a heat sink size of 22.43% for the shorter module. The results also show that the TEG with a smaller TE leg height yields the best output power at low load resistance ranging from 0.2 Ω to 2 Ω, as the TEG with a taller TE leg renders better performance at higher load resistance ranging from 3 Ω to 16 Ω at the optimal conditions. The results show that the hot side temperature remains the most important parameter in the optimization process. Furthermore, convection cooling from naturally occurring winds has a minimal but positive effect on the output of the presented TEG system.

INTERACTION OF HEAT TRANSFER METHODS, STORAGE TEMPERATURE AND PACKAGING ATMOSPHERE ON QUALITY OF PROCESSED CHICKEN MEAT

This research investigated the combined effects of cooking methods (household griddle (C1), household conventional oven (C2), industrial oven (C3), storage temperature (refrigeration /freezing) and packaging system (aerobic and vacuum), on quality of chicken burgers. The results show that refrigeration storage favours the retention of moisture content and the juiciness of chicken burgers, but the application of vacuum (RV) was the best option to maintain the juiciness and moisture content (p &lt; 0.05) of the samples prepared in an industrial oven with forced-air convection. The highest protein content was observed in the samples that were frozen in vacuum packaging (FV), and the lipid content was highest in the samples chilled in conventional packaging (RC) at 1 atm. Regardless of the cooking method used and the internal pressure of the packages (≤ 1 atm), refrigerated storage contributed to the best scores (p &lt; 0.05) for color and flavor attributes. The treatments that presented the highest sensory acceptance index were the frozen samples in vacuum packaging prepared in the industrial oven, conventional oven, and grill (90%, 82.66%, and 74.33%, respectively).