Effect Of Air Velocity Research Articles

Analysis and prediction of battery temperature in thermal management system coupled SiC foam-composite phase change material and air

Lithium-ion batteries crucially rely on an effective battery thermal management system (BTMS) to sustain their temperatures within an optimal range, thereby maximizing operational efficiency. Incorporating bio-based composite phase change material (CPCM) into BTMS enhances efficiency and sustainability. This study commences by blending lauric acid and myristic acid in a 7: 3 mass ratio to synthesize a bio-based CPCM, following which the thermophysical properties of this CPCM are tested. Subsequently, the CPCM is integrated into a SiC foam and coupled with air to develop a novel BTMS. Then the effects of air velocity and initial temperature on the temperature of the battery pack are analyzed. Finally, the RIME-Convolutional Neural Network (CNN)- Self-Attention (SA)- Gated Recurrent Unit (GRU) model is established to predict the temperature of the battery in this BTMS. The results indicate that the latent heat of the CPCM is 97.98 J/g, melting at 35 °C upon heating. The incorporation of SiC foam-CPCM effectively reduces battery temperatures. When the air velocity is set at 3 m/s, the battery temperature remains below 40 °C during a discharge rate of 2C. Notably, the CPCM melts at higher initial temperatures, effectively mitigating the temperature rise in the battery pack. The RIME-CNN-SA-GRU model exhibits remarkable accuracy, with a maximum prediction error of 0.56 °C and a RMSE of 0.23, precisely capturing the trend of a sharp temperature rise at the end of discharge. This study presents an efficient solution for lithium-ion battery thermal management and temperature prediction.

Effect of Air Parameters on LiCl-H2O Film Flow Behavior in Liquid Desiccant Systems

The wettability and stability of a solution’s film on the filler surface are the key factors determining heat and mass transfer efficiency in liquid desiccant air conditioning systems. Therefore, this study investigates the effects of different air parameters on the flow behavior of a lithium chloride solution’s film. The effects of air velocity, air flow pattern, and pressure on the wettability and critical amount of spray are discussed. The results show that the main mechanism by which the air velocity affects the wettability is that the shear stress generated by the direction of the air velocity disperses the direction of the surface tension and weakens its effect on the liquid film distribution. In addition, in the counter flow pattern, the air flow blocks the liquid film from spreading longitudinally and destroys the stability of the liquid film at the liquid outlet, which increases the critical amount of spray. The pressure distribution is similar under different operating pressures when the flow is stable; thus, pressure has little effect on wettability. The simulation results under 8 atm are compared with the experimental results. It is found that the sudden increase in the amount of moisture removal when the amount of spray changes from 0.05 to 0.1 m3/(m·h) in the experiment is caused by the change in the liquid film flow state. In addition, the results show that within the range of air flow parameters for the liquid desiccant air conditioning system, air flow shear force is not the main factor affecting the stability of the solution’s film, and there is no secondary breakage of the solution’s film during the falling-film flow process.

Numerical study of solar evaporation in 3D-printed structures

In this study, we used three-dimensional (3D) printed concave geometries filled with activated carbon to create a unique 3D solar evaporator for clean water production. The evaporation process was modeled considering airflow and solar radiation to investigate the advantages of 3D concave geometries. This work encompasses a series of studies, focusing on mass transfer inside the concavity and around the structure, to elucidate specific exchange points. Additionally, the research explores the effects of air velocity and the incorporation of additional holes within the structure, with the aim of improving evaporation.

Micro-mechanical behavior of stone-blowing in ballast maintenance using DEM-CFD coupling method

Stone-blowing restores the track geometry by blowing small crushed stones into the bottom of the sleeper, extending the maintenance period. In this study, ballast and filling stones were modelled using discrete element method (DEM), while the air blowing was simulated using computational fluid dynamics (CFD). The DEM-CFD coupled model has been used to simulate the stone-blowing process and investigate the optimal operation parameters from a micro view.The disturbance of ballast bed during stone-blowing process was analyzed. Meanwhile, the effect of air velocity and tube layouts on the stone-blowing, as well as the sleeper settlement after stone-blowing were discussed. The results show that the maximum disturbance occurs in the inserting area between sleepers, and the disturbance increased with faster insertion speed. It was suggested that the inserting speed of the tube is 0.4 m/s. When the air velocity of stone-blowing was not less than 20 m/s, the blowing quality meets the requirement. Furthermore, the four-tubed stone-blowing approach distributed filling stones more evenly under the sleeper, and reduced the risk of tube blockage. After stone-blowing, the contact number between the bottom of the sleeper and the ballast is greatly increased, reaching 217.9 % after double cross tubes, and 245 % after four tubes stone-blowing. The crushed stone blown in greatly improves the stress distribution of the ballast bed and makes the load transfer more uniform. Overall, this study provides valuable insights into the stone-blowing process and can help optimize the stone-blowing parameters for efficient and effective track maintenance.

Drying kinetics of lemon (Citrus lemon) seeds on forced-air convective processing

The convective drying kinetics of Citrus lemon seeds at different air temperatures (60–160 °C, 0.3 m.s−1), as well as the effect of air velocity (v) and technology (tray and rotary drum (RD) drying), were investigated. Internal seed temperature profiles showed that most of the process would occur under internal mass transfer control. Each drying curve was fitted with a theoretical diffusion model to determine the effective diffusivity (Deff), and with nine empirical models. Deff were 0.65 × 10−10-13.10 × 10−10 m2.s−1 and the activation energy was 19.90 kJ.mol−1. Deff increased by 85% when v was raised by 50%; this effect was partially compensated by seed movement when using RD (62% increment). A two-term exponential model with arrangements over the pre-exponential terms demonstrated the complementarity of both terms in explaining the seed dehydration process. In addition, convective heat transfer coefficients were calculated (0.48–0.65 W.m−2 K−1). Overall, the results provide valuable kinetic parameters to characterize the dehydration process for further design and simulation of drying equipment.

Effect of air velocity and relative humidity on passengers’ thermal comfort in naturally ventilated railway coach in hot-dry indian climate

In India, railways still continue to be the most prominent means of transport, especially non-air conditioned railway that carries around 3.5 billion people every year. Thermal comfort in these non-air-conditioned trains is predominantly influenced by windows and fans. The present study orients around the effect of fan air as well as naturally ventilated air on thermal comfort of passengers. The study is part of a field survey followed by an experimental investigation that was carried out in non-air-conditioned railway coaches during summer afternoon, with more than 1500 subjects of different gender and age category. The study significantly contributes in defining an elevated acceptable range of comfort air velocity inside a moving stock. The mean threshold air velocity where passengers responded a neutral PCV (passengers' comfort vote) is found to be 2 m/s which is much higher than conventional standards for enclosed static buildings and premises. The clear dominance of behavioral adaptation has been noticed in expression of thermal comfort by the passengers. This strengthens the idea of adopting some alternative method to deal with thermal discomfort of non–air-conditioned railway passengers. Here a novel term as ‘zone of independence’ (ZoI) has been defined at which the effect of air velocity becomes independent on passengers' comfort vote. This ZoI can significantly be utilized while optimization of thermal comfort in an ICF railway coach.

CONVECTIVE DRYING KINETICS OF YACON (Smallanthus sonchifolius Poepp. Endl.) SLABS AND EVALUATION OF THE DRYER PID TEMPERATURE CONTROL SYSTEM

Yacon is a functional food that is rich in fructooligosaccharides (FOS) and highly perishable, which requires inexpensive methods for its preservation. The objectives of this research were to model the kinetics of convection drying of yacon slabs and to assess the effect of air velocity on the temperature record of the heating zone controlled by the Proportional-Integral-Derivative control system (PID). Different temperatures (60, 70, and 80 °C) at constant air velocity (0.87 m s-1) were evaluated in a convective tray drying system. To determine the effect of air velocity on the PID temperature controller, different air velocities (0.81-2.06 m s-1) at constant temperature (70 °C) were studied. The results showed that Page’s model was the best fitting of the data obtained, the effective diffusivity of convective drying of yacon ranged from 1.22x10-10 to 1.9x10-10 m2 s-1 and the activation energy was 21.76 kJ mol-1. With PID temperature control, it was observed that the best drying rate and lowest temperature signal error occurred at an air velocity of 1.46 m s-1, where the temperature signal was more stable and closer to the reference temperature. In conclusion, the kinetic modeling of the convective drying of yacon provides optimal drying parameters as well as behavior of mass and heat transfer phenomena, particularly considering that the effect of air velocity influences the drying kinetics and the PID temperature control of the dryer.

EXPERIMENTAL AND NUMERICAL STUDY ON EFFECTS OF NEW-GENERATION FINNED HEAT EXCHANGER ON THERMAL PERFORMANCE OF THERMOELECTRIC COOLING SYSTEMS

In this study, an attempt has been made to increase the efficiency of the thermoelectric refrigerator by designinig a new-generation finned heat exchanger. Surface extension, which is one of the most applied passive heat transfer enhancement techniques, was applied for this finned heat exchanger. In this application, the heat absorbed from the cooling room is transferred to the external environment more effectively. In addition, by using an external thermoelectric element (which is installed with the secondary heat exchanger), the heat exchanger cools down faster and the heat is transferred to the environment more quickly. The manufactured cooling system was tested experimentally under different working conditions, including natural and forced convection. The effects of air velocity and applied voltage to the external TE module on thermal performance were examined. Additionally, the external finned heat exchanger has been simulated and heat transfer characteristics have been evaluated using computational fluid dynamics. The lowest and highest COP values have been obtained as 0.003 and 0.011, respectively, when the external TE module has been passive. By providing 12 V for the external TE module, the lowest and highest COP values have been observed as 0.0031 and 0.0042, respectively. In addition, the importance of surface extension applications for the efficient operation of thermoelectric elements has been emphasized.

Quantitative review and machine learning application of refractance window drying of tuber slices

Abstract Refractance window drying (RWD) is a preferred drying technique due to its suitability for heat-sensitive products. Although this drying technique appears promising, it is yet largely unexplored. In this study, the authors provide a review of the existing milestones on RWD using a sample of 40 articles from 2000 to date to quantify the state of investigations across multiple studies and establish specific areas needing further attention. Results show that experimental analyses constitute about 53–59 % of the reported cases, followed by a literature review 24–28 %. Furthermore, 17 % of the total study cases was observed across all modelling categories, with machine learning (ML) techniques constituting only about 8 %. Driven by the outcome, this study thus utilized three ML techniques to model the moisture ratio (MR) of 1.5–4.5 mm thick yam slices, operated over the range of 65–95 °C temperature in an RWD chamber. Unlike the routine procedures, the yam thickness versus air temperature effects on moisture ratio were investigated to determine the more significant factor as well as the air velocity effect or its lack thereof on MR. To investigate the validity window for the entire dataset, all data points were considered, with a training-testing ratio of 7:3 used in each case. For scenario one, prediction based on the yam thickness effect showed a greater influence on the MR. The air velocities at 0.5–1.5 m/s had little effect on MR as compared to the case where air velocity was ignored (i.e., the control case in this study). Also, model accuracy for all tested samples has been determined to be better than 93 %. Insight from this study is to guide in the future design of RW dryers for direct measurement of the moisture ratio of harvested root tubers at various conditions.

Experimental study of the influence factors of the droplet size of rotary nozzles during manned helicopter spraying operations

The droplet size significantly affects the performance of aerial spraying operations. Thus, it is crucial to develop rotary nozzles for helicopter spraying operations and analyze the influence of droplet size. We conducted a calibration test of the nozzle rotation speed to analyze the effects of air velocity, blade installation angle, hub diameter, and blade length on the rotation speed. The results showed that the rotation speed increased with an increase in air velocity and nozzle diameter and decreased with an increase in the blade angle. The rotation speed of three types of rotary nozzles was measured in the range of 576–15 358 r/min. A high-speed wind tunnel test was conducted to determine the droplet size of the rotary nozzles at different rotation speeds, spray flow rates, and hub mesh numbers. The influence degree of the three factors on the droplet size was rotation speed > spray flow rate > mesh number. The multiple linear regression equation of the volume median diameter (VMD) of the droplet size was obtained. The droplet size obtained from wind tunnel and flight tests at 5000 and 7000 r/min was compared. The droplet size was in the range of 148.56–259.39 μm and was slightly larger under wind tunnel conditions than during the flight test. The relative width of the droplet spectrum was small for both test methods, indicating that the droplet size distribution of the three rotary nozzles was uniform. Finally, the spray nozzles were used for insect control in forest areas and achieved a control efficiency of 94.6. This study provides a reference for optimizing the operating parameters of spraying nozzles and improving the performance of helicopter-based low-volume spraying operations.

Assessment of ammonia distribution in a livestock farm using CFD simulations

Livestock farming is a significant source of ammonia emissions, which can have adverse effects on human health and the environment. Understanding the distribution and dispersion of ammonia within a livestock farm is crucial for developing effective mitigation strategies. In this study, computational fluid dynamics (CFD) simulations were employed to assess the spatial distribution of ammonia within a representative livestock farm. A detailed 3D model of the farm was created, incorporating the structural layout and ventilation systems. The CFD simulations were conducted using an approach validated by several other researcher groups, considering factors such as ammonia release rate, temperature, and ventilation rates. The results of the CFD simulations provided valuable insights into the distribution patterns of ammonia within the farm. The concentration contours revealed areas of high ammonia concentration, highlighting potential hotspots and vulnerable locations. To investigate the effect of air velocity and temperature on ammonia convection and to save electricity cost, the duty cycle was determined using transient analysis. We have studied the costs and benefits of agricultural ammonia emission abatement options for compliance with air quality regulations. The simulations allowed for the evaluation of different ventilation rates to mitigate ammonia concentration. The findings contribute to the understanding of ammonia emission sources and provide valuable guidance for the design and optimization of livestock farming systems, enabling the development of sustainable practices that mitigate the environmental impact of ammonia emissions.

Experimental analysis of smoke dispersion in belt fires by using a real-size model of the underground space

It is essential to investigate the dispersion of a large amount of toxic and harmful smoke in coal mine network during belt fires. A real-size model of an underground space was used to study the additional thermal resistance of single roadway and the dispersion characteristics of CO in bending structure, as well as the effect of air velocity on CO dispersion. The results show that the resistance of high temperature air flow is related to the ventilation resistance of the roadway under normal airflow, and is proportional to airflow temperature. The additional thermal resistance increases first and then decreases with time, and curve trend is similar to multiple “humps” with the increase of distance, which indicates that temperature is dominant factor. The distribution of CO is V-shaped at 90° corner, and the distribution pattern is unaffected by corner number. The increase of the air velocity destroys the CO distribution at the initial corner, and the air vortex zone appears at the bottom of the roadway. Meanwhile, the smoke flow diffused to the working face shifts from the outer wall to the inner wall of the working face. The results are helpful for selecting emergency evacuation areas and implementing safe measures.

Addressing personalized thermal comfort in residential settings: A novel dual-supply vent air conditioner

A new approach was proposed for meeting diverse thermal comfort demands of different occupants by using a dual-supply vent air conditioner with independent control of the air supply parameters at each vent to establish distinct thermal environments. The feasibility of this method was tested in a living room environment, and numerical simulation was conducted to explore the differences in thermal environment at various locations under different air supply temperatures, velocities, directions, and vent positions. The results indicated that, within the targeted air supply zone, the maximum temperature difference could reach around 2.5 °C. Considering the Cooling Effect of air velocity, the maximum Equivalent Temperature difference was around 4.5 °C, which could address the differences in common personalized thermal comfort preference. Utilizing the differential air supply velocities of different vents was an effective means of achieving diverse thermal environments, although attention should be paid to local thermal discomfort caused by drafts. This approach may offer a new perspective in addressing the differing thermal comfort preferences among occupants within the same residential room, additionally providing innovative insights for improving traditional air conditioning systems.

Simulation Analysis and Experimental Verification of Freezing Time of Tuna under Freezing Conditions

In order to predict the regular temperature change in tuna during the freezing process for cold chain transportation, improve the quality of frozen tuna, and reduce the energy consumption of freezing equipment, a three-dimensional numerical model for freezing tuna of different sizes was established. An unsteady numerical simulation of the air velocity and flow field was combined with an analysis of the freezing process of tuna. This paper also studied the effect of air velocity, temperature, and tuna size on the freezing process. The numerical results show that there was a positive correlation between the cold source environment and the tuna-freezing process. Lower temperatures and higher air increased the velocity at which the tuna moved through the maximum ice crystal formation zone, maintaining a better aquatic product quality. In some cases, however, the smaller tuna models achieved a longer freezing time. Due to the difficulty of obtaining the whole tuna sample, the temperature curve and freezing rate over time obtained during the freezing process were tested using a tuna block of a specific size. The maximum error did not exceed 6.67%, verifying the authenticity and feasibility of the simulation.

Experimental study on the influence of environmental parameters on human multi-node warming sensitivity and demand

The thermal comfort of personnel can be improved by optimizing the thermal environmental parameters. And local temperature regulation can enhance the body's comfort in hotter or colder environments. This study systematically investigates the changes in skin temperature, local thermal sensation, and thermal comfort in eight parts before and after heating stimulation under four ambient temperatures and six air velocities, and develops multi-node physiological models of human warming sensitivity and demand. The results indicate that post-stimulation ambient temperature and air velocity have weaker effects on thermal sensation vote and thermal comfort vote than pre-stimulation. The warming demand of the face shows poorer sensitivity to ambient temperature, which is 66.88% lower compared to the abdomen. The air velocity strongly influences the warming demand of the neck, which is 75.01% higher than the lower legs. In addition, the warming sensitivity of the trunk is more influenced by ambient temperature than by air velocity, whereas the extremities' sensitivity is more susceptible to air velocity. The effect of air velocity on warming demand is 2.01–5.91 times greater than the ambient temperature. This study also presents the optimum comfortable temperature and the corresponding equilibrium velocity, providing a certain design basis for pulsating air supply, task-ambient air conditioning, and other variable air supply parameters methods.

The influence of the incoming air velocity with the fan on the inlet side of an air-water generator on the freshwater mass

The air-water generator is a promising device to provide freshwater in the future. However, the machine still produces less freshwater; hence, a study of the effect of air velocity with a fan installed at the entrance of a simple air-water generator on the freshwater mass was conducted under environmental conditions. The air velocities varied were 4 m/s, 5 m/s, and 6 m/s. The air-water generator was made from a refrigeration machine system using R134a refrigerant as the working fluid. The compressor specification was 1 PK rotary type. The results show that the highest average freshwater mass obtained is 1241 g for 7 hours, the highest COP was 4.72, and the highest total heat transfer rate is 208.21 J/s.

Modeling and optimization of integrated earth air heat exchanger and direct evaporative cooling system using ANN and RSM approaches for preserving fruits and vegetables

AbstractConventional air‐conditioned storage systems are more energy intensive which requires a consistent supply of electricity. Apart from this, it is costly and not suitable in remote areas where electricity is almost inaccessible. Therefore, the present study aimed to test the performance and feasibility of an integrated earth air heat exchanger and direct evaporative cooling system for storage of fruits and vegetables. The effects of air velocity (4–6 m/s), water flow rate (0.032–0.096 kg/s), and thickness of the cooling pad (50–150 mm) with corresponding responses were investigated in order to develop response surface methodology (RSM) and artificial neural network (ANN) models and compared them to predict temperature drop and humidity rise. Using RSM model, the optimum values for maximum temperature drop (16.80°C) and humidity rise (70.85%) within a range of input variables were found to be 4 m/s air velocity, 0.065 kg/s water flow rate, and 150 mm thickness of the cooling pad. For predicting the temperature drop and humidity rise, the higher (0.992 and 0.998) lower MAE (0.045 and 0.064), RMSE (0.187 and 0.266), and values (0.028 and 0.001) were observed in the ANN model. The developed ANN model was better than RSM models, and the model prediction was in good agreement with experiment values within the range of ±5% uncertainty. The results of this study indicate that the proposed cooling system can be successfully applied to store horticultural commodities.Practical ApplicationIntroduced hybrid cooling technique is low‐cost and eco‐friendly, and can be commercially used for on‐farm storage of fruits and vegetables to enhance their shelf life. The system is helpful for smallholder farmers/retailers to maintain the quality of the commodity during storage, minimize post‐harvest losses, and fetch good market value for the commodity.

Comparison of the dried properties of Ganoderma lucidum produced by the convective dryer and infrared dryer

Ganoderma lucidum is a promising medicine with a high amount of antioxidants and calcium. The selection of appropriate drying process methods in food science has a chief role to reach the best final characteristics. This study aimed to investigate the effects of air velocity and temperature in the convective dryer, sample distance, and infrared power in infrared dryers on the drying kinetics and quality of Ganoderma lucidum slices. In addition, Response Surface Methodology based on central composition design was used to optimize and analyze drying conditions. The ranges of temperature and air velocity were 40–60 °C and 0.5–1.5 m/s, respectively in the convective drying process while the range of distance and infrared power was 4–16 cm and 500–1500 W, respectively in the infrared drying process. It is worth mentioning that antioxidant and calcium contents were greatly enhanced during the drying procedures. Moreover, the values of the total color difference ranged between 8.21 and 19.66 for the convective dryer and 8.14 and 28.85 for the infrared dryer. A kinetic study indicated that dried samples by the infrared dryer could rapidly reach equilibrium moisture content due to exposure to IR radiation. Consequently, the results indicated that the infrared dryer has better performance than the convective dryer regarding drying time, energy consumption, and amount of calcium and antioxidant.

The effect of air velocity and indoor ambient properties on the effective operating range of an air ionizer device

Air ionizers are devices that purify the indoor air by artificially generating negative air ions (NAIs) which are proven to improve air quality and well-being of humans. Hence, more ionizers are being incorporated into heating, ventilation and air conditioning (HVAC) applications nowadays. . Every ionizer has its effective range of operation, which is the area inside a room that can potentially be covered by significant concentration of NAIs compared to the general concentration of ions naturally present in the room. This range may change depending on the indoor temperature, humidity and fan speed of the HVAC unit as preferred by the room occupants. Present research intends to design an experimental setup that could measure negative air ion (NAI) concentration at varying distances from an ionizer under different values of the aforementioned parameters. The experiment was conducted inside an indoor psychrometric test room to allow controlling of ambient temperature and humidity. Air velocity through the ionizer was varied from 1.5 m/s to 4.5 m/s, whereas the range of temperature and relative humidity were set from 25°C to 31°C and 60% to 80% respectively. To evaluate the ionizer’s operating range, NAI concentration was measured at every preset longitudinal (0 cm to 75 cm), lateral (-25 cm to 25 cm) and elevation (-15 cm to 15 cm) distance relative to the ionizer for 6 minutes using an ion counter named “Air Ion Counter Model AIC2”. The results reveal that the ionizer’s effective operating range increased with velocity, with the furthest range recorded at 4.5 m/s. Whereas a negative correlation was found between the ionizer’s effective operating range with temperature and humidity, with the furthest range recorded at 25°C and 60% respectively. The results also show that most ions were distributed in areas below and towards the right side from the ionizer’s perspective.

Numerical Investigation of Cross-Flow Water Cooling Towers

Abstract In this study, thermal performance of the forced cross-flow water cooling tower is numerically investigated by using the commercial computational fluid dynamics software ansys-cfx. The temperature variation between inlet and outlet of the water, namely, process water temperature, is the main extracted result of simulations. Additionally, the cooling range (CR) that is the difference between inlet water temperature and outlet water temperature is the second representative result of the analysis. The effect of air velocity (Va), water droplet diameter (dw), and water temperature at the inlet of tower (Tw) are the variables that are considered to be the effective design parameters on the process temperature of the water. The process water temperature decreases, but the cooling range increases when the air velocity increases. When the inlet water temperature increases, the process water temperature and the cooling range also increase. On the other hand, the process water temperature decreases with the decreasing diameter of water droplets.