Inlet Air Flow Rate Research Articles

Analysis of Inlet Temperature and Airflow Rate on Drying Process in a Spray Dryer Using Computational Fluid Dynamics Method

Spray drying is a method of producing a dry powder from liquid or slurry by rapid drying with a hot air. The spray drying process consists of atomizing the liquid into fine droplet, contacting the hot air with the droplets, drying droplets by the formation of solid particle agglomerates and separating solid products. This research was carried out to analyse the drying process parameter of spray dryer to reach the fluid drying temperature of around 100°C in which the drying process is assumed to be successful. Simulation using computational fluid dynamics method was performed. Air and water were employed as the working two phase fluids injected into the drying chamber at various inlet temperatures and airflow velocities. RNG k-ɛ and k-ω were used to solve drying process phenomenon in the drying chamber. In this work, the inlet air temperatures and the airflow velocities were varied from 175°C to 225°C and 1.5 m/s to 3 m/s, respectively. The results showed that the higher inlet air temperature, the greater the outlet temperature. In addition, the outlet temperature also increased with the increase of airflow velocity. Under the condition investigated, the optimal parameter was found at inlet temperature of 225°C and airflow velocity of 3 m/s. This condition is expected in avoiding the failure of spray drying process.

The Effect of Multiple Coexisting Convective Modes in Determining Thermoacoustic Behavior of a Partially Premixed Swirl Flame

Abstract This study focuses on the effect of multiple heat release mode interactions on the amplitude of unsteady pressure oscillation for a partially premixed radial swirl burner, which uses methane as fuel. A range of operating conditions based on inlet airflow rate and global equivalence ratio is considered for this purpose. The pressure time series shows amplitude modulation at the dominant frequency for all the flow rates and equivalence ratios considered. Wavelet analysis based on continuous wavelet transform illustrates the presence of heat release rate fluctuations at multiple frequencies other than the dominant mode of pressure oscillation, with this more pronounced at low frequencies. Spectral proper orthogonal decomposition performed on time-resolved CH* chemiluminescence images reveal four dominant spatial modes of chemiluminescence, chosen based on the dominant wavelet coefficients for the same. The identified frequencies correspond to the duct-acoustic mode, helical mode (spectrally close to acoustic mode), low-frequency axisymmetric mode and low-frequency helical mode. The low-frequency helical mode (considered as the result of nonlinear interaction between acoustic and helical mode) and the low-frequency axisymmetric mode (considered to have independent existence) have similar spectral content. Amplitude modulation of unsteady pressure is found to be a result of the superposition of duct-acoustic mode and low-frequency axisymmetric mode, whereas reduction in overall pressure amplitude with the decrease in global equivalence ratio is seen to be a result of an increase in the dominance of low-frequency helical mode. The relative dominance of low-frequency helical mode over dominant pressure mode reduces the overall pressure amplitude.

Performance assessment of a flat-sheet membrane-based dehumidifier with serpentine flow channels: An experimental study

Membrane-based dehumidification system is an emerging technology which drives based on the renewable low-grade energy sources. Water vapor selective membrane is able to separate water vapor from the air which can be used to condition air in buildings, more efficiently than conventional air-conditioning equipment. Flow channel designs (especially serpentine-type) and their impacts on the thermal–hydraulic performance of membrane-based dehumidifiers are essential and not well-studied. In the present work, a novel flat-sheet membrane dehumidifier with serpentine flow channels is designed and evaluated experimentally. The serpentine flow channel offers a long flow path that the air in the wet and dry sides of the channel interacts with each other through the membrane, thereby improving the heat and water vapor transfer. The effect of inlet air flow rate, relative humidity, and temperature of both wet and dry sides on the dehumidification rate, approach temperature, pressure drop, and coefficient of performance of the dehumidifier is examined. Results show that passing the humid air with higher flow rate, humidity, and temperature through the wet side channel leads to the higher dehumidification rate, approach temperature, and pressure drop. Increase of wet side air temperature and flow rate enhances the coefficient of performance, and the effect of inlet air relative humidity on the coefficient of performance is observed negligible at high air flow rates. Parametric study of dry side air condition reveals that the air with lower humidity improves the dehumidification rate and coefficient of performance, while its effect on the approach temperature and pressure drop is observed negligible. Elevated air temperature of dry side has positive and negative impact on the approach temperature and coefficient of performance of the dehumidifier, respectively.

Comparative Analysis on Dehumidification Performance of KCOOH–LiCl Hybrid Liquid Desiccant Air-Conditioning System: An Energy-Saving Approach

Conventional air conditioners (AC) operate on vapor compression refrigeration (VCR) technology, which is a heavy consumer of electricity, and the used refrigerants harm the environment. In humid and hot areas, a liquid desiccant AC system integrated with a VCR system has been proposed as a better alternative to traditional standalone VCR system, as it is an energy-efficient system that can remove latent air load, air pollutants from the processed air, and it is energy-saving. In this study, a hybrid liquid desiccant air conditioning (LDAC) system with a capacity of 5.5 kW was designed and developed by integrating these two different technologies, and the vapor pressure of potassium formate (KCOOH) solution at different solution temperatures and concentrations were monitored experimentally to determine the optimal concentration range. Moreover, a comparative study was conducted to analyze the dehumidification performance of lithium chloride (LiCl) and KCOOH solutions. Experiments are designed by using Minitab 19 software, which employs the design of an experimental technique through full factorial design by considering four variables, namely, type of desiccant, inlet air flow rate, inlet desiccant temperature, and inlet air humidity. To study and compare dehumidification characteristics of both solutions, three responses were considered, i.e., the coefficient of performance of a hybrid system, the heat load of dehumidifier, and specific humidity change. Experimental results revealed that 70% of KCOOH solution exhibited comparable vapor pressure to that of 36% LiCl solution. Additionally, the dehumidification ability of the KCOOH solution was better than that of the LiCl solutions.

Three dimensional MHD nanoluid stagnation point low withhigher order chemical reaction

In hot and dry climates, evaporative cooling of the air by water spray can be applied in several requirements, such as evaporative condensers which the airflow is precooled by the water spray before it reaches the condenser. The interaction between water droplets and the air is a complicated two-phase flow that is affected by the several parameters. Here, an Eulerian-Lagrangian 3D model was developed to investigate the influence of important parameters on spray cooling performance in a rectangular duct. The evaluated parameters include the number of nozzles, inlet air flow rate, and spray water flow rate. The results represented that growth in the number of nozzles causes a reduction in the spray cooling efficiency. Thi s is due to decrease of droplets retention time within the duct by increasing the number of nozzles at a constant total spray flow rate in the cases. The maximum and minimum spray cooling efficiency belong to the cases with one nozzle at water flow rate of 20 l/h and four nozzle at water flow rate of 5 l/h, respectively. The difference between spray cooling efficiency at 3 and 4 number of nozzles is less than 1.8%. Moreover, increasing the air flow rate from 0.5 l/h to 2 l/h (by 300%) makes a decrease in the spray cooling efficiency up to 58.6%.

Quantifying the coating yield by modeling heat and mass transfer in a Wurster fluidized bed coater

During the coating process of medicines, premature drying of the spray droplets may cause losses, as the droplets do not stick to the product. This work addresses two mechanisms that are central to predicting the heat and mass transfer in coating processes: (i) the evaporation of multicomponent spray liquids and (ii) the quantification of losses due to spray drying. We modeled a Wurster coating process via CFD-DEM simulation and validated the results based on temperature and coating-yield measurements obtained in lab-scale experiments. We assessed the effects of the inlet air flow rate, inlet air temperature and spray rate on the drying performance in a set of virtual experiments. Our calculations show that spray-drying losses can be reduced from 28.2% to 6.1% by selecting appropriate values of the input parameters. Implementing these results in a real coating system will maximize the coating yield and can reduce the process time by up to 75%.

Machine learning model of regenerative evaporative cooler for performance prediction based on experimental investigation

The regenerative evaporative cooler is experimentally investigated in this study and the predictive machine learning model is developed based on the test data to predict the energy and exergy performances of the device. This statistical machine learning framework is used to study the effect of six input operating variables (air inlet temperature, inlet air flow rate, air inlet specific humidity, water flow rate, inlet water temperature and extraction ratio) on the output variables (supply air temperature, cooling capacity, dew point effectiveness, coefficient of performance and exergy efficiency). The linear and polynomial regression models are followed to see the exactness of the model and check the train score against the test score. The effect of all the input variables on the output variables are discussed as well. In the case study, the developed machine learning model is used to predict the performances of fabricated regenerative evaporative cooler based on the field weather data of different days of 2020 in Varanasi. Model train score is 0.9974; the test score is 0.9912, the mean squared error is 0.1427, and the root mean squared error is 0.3778. This model can be used to predict the cooler performance under varied operating conditions.

Numerical analysis-based performance prediction in a direct evaporative cooler used for building cooling

In the present performance parameters is determined for the varied operating conditions using mathematical modelling. Outlet humidity ratio, Dry bulb temperature (DBT), cooling efficiency and cooling effect have been predicted by varying the air velocities, inlet DBT, inlet relative humidity (RH) and pad thickness for three different wettability of Celdek packing. Predicted results revealed that cooling effect, saturation efficiency, ΔDBT and humidity ratio are found to be increasing with the increase in pad thickness and wettability of the material. An increase in the inlet air flow rate and RH resulted in a decrease in ΔDBT, humidity ratio and cooling efficiency. The maximum performance of ΔDBT, ΔRH, saturation efficiency and cooling effects have been observed for Celdek 7090 and are equal to 6°C, 55%, 90% and 7000 Watts for the thickness of 0.3 m, wettability of 630 m2/m3. Wettability of 630 m2/m3 & thickness 0.3 m gave maximum performance.

Thermal analysis on the impact of spray charactristics on evaporative cooling process

In hot and dry climates, evaporative cooling of the air by water spray can be applied in several requirements, such as evaporative condensers which the airflow is precooled by the water spray before it reaches the condenser. The interaction between water droplets and the air is a complicated two-phase flow that is affected by the several parameters. Here, an Eulerian-Lagrangian 3D model was developed to investigate the influence of important parameters on spray cooling performance in a rectangular duct. The evaluated parameters include the number of nozzles, inlet air flow rate, and spray water flow rate. The results represented that growth in the number of nozzles causes a reduction in the spray cooling efficiency. Thi s is due to decrease of droplets retention time within the duct by increasing the number of nozzles at a constant total spray flow rate in the cases. The maximum and minimum spray cooling efficiency belong to the cases with one nozzle at water flow rate of 20 l/h and four nozzle at water flow rate of 5 l/h, respectively. The difference between spray cooling efficiency at 3 and 4 number of nozzles is less than 1.8%. Moreover, increasing the air flow rate from 0.5 l/h to 2 l/h (by 300%) makes a decrease in the spray cooling efficiency up to 58.6%.

Experimental investigations on indirect contact type liquid desiccant cooling systems for high latent heat load application

Heat driven sorption technologies are promising alternatives to traditional vapour compression based systems for comfort cooling. High latent heat load applications and improved indoor air quality are best accommodated by the various sorption technologies available and desiccant-based cooling systems. Liquid desiccant-based systems are preferred over solid desiccant-based systems due to lower pressure drop, the possibility of continuous operation, solar energy for regeneration, and the ease of storage of regenerated desiccant solution. This paper investigates the experimental performance of indirect contact type liquid desiccant cooling systems for applications involving a high latent heat load. An experimental test rig includes a dehumidifier, regenerator, and heat exchanger, all been developed, fabricated and connected to work as one unit. The dehumidifier and regenerator transfer the heat and mass from liquid desiccant to the air membrane making the arrangement an indirect contact type of heat exchanger. Lithium Chloride solution is used as a desiccant solution in experiments, and Polyvinylidene Fluoride is used as a membrane material. The effect on dehumidifier performance parameters like rate of moisture removal, sensible heat effectiveness, and latent heat effectiveness is studied for varying inlet air parameters as well as for various liquid desiccant operating parameters. The inlet air specific humidity ranges from 10 to 13 g/kg da, and the inlet air flow rate varies from 2 to 4.5 kg/hr. The inlet desiccant temperature supplied at 24–32 0C with desiccant concentration varied 30–42%, and the desiccant solution mass flow rate is supplied in the range of 3–11 kg/h. Various dehumidifier performance parameters like rate of moisture removed, latent heat effectiveness and sensible heat effectiveness are discussed. Based on the experimentation, utilizing the optimum values of inlet air parameters or optimum values of desiccant solution parameters has been recommended to achieve the cooling system's highest possible latent heat effectiveness.

Heat and mass transfer analysis of natural convection in a liquid desiccant closed-loop system: The effect of heat source and heat sink temperature

Considering the importance of providing healthy and suitable indoor air condition efficiently, liquid desiccant air condition systems are the focus of study in recent years. The concept of natural convection heat and mass transfer loop is introduced. The system is a closed-loop consisting of two three-fluid hollow fiber membrane heat and mass transfer exchangers played as absorber and regenerator. The system was run under standard conditions with an inlet air flow rate of 6 m3/h. The sensitivity analysis was made to reveal the effect of heat source and heat sink temperature on the system performance. The heat sink and heat source temperature lie between 15–25 °C and 50–70 °C respectively and the outlet air temperature and humidity ratio, moisture removal rate, cooling capacity and coefficient of performance are the evaluating indexes. The results show that despite the convectional desiccant loops the high solution flow rate is not desirable and instead the concentration gradient in the loop is the most important factor. For each heat source temperature, there is an interval of heat sink temperature for which the solution flow rate is the maximum and the concentration gradient is the minimum. Under operating conditions of the present study, the maximum obtained COP is 0.71 which is for temperature pair of (55 °C, 20 °C).

Data-driven prediction of flame temperature and pollutant emission in distributed combustion

The flame temperature and pollutant emission (of NO and CO) characteristics in distributed combustion were examined using data-driven artificial neural network (ANN) approach. Experimental results collected from swirl-assisted distributed combustion using methane fuel at an equivalence ratio 0.9 were utilized for dataset preparation. The distributed combustion condition was created in a swirl-assisted burner (at thermal intensity of 5.72 MW/m3-atm) by diluting the main airstream with carbon dioxide. Experimental results of exhaust NO and CO concentrations and adiabatic flame temperature (AFT) derived from Chemkin-Pro® simulation were selected as the target output. The ANN model was developed with inlet airflow rates and O2 concentrations as the input, and pollutant emission and AFT as the output variables. The ANN possessed one hidden layer with variable number of neurons (10, 15, and 20). Tangent sigmoid and Log sigmoid transfer functions were tested along with feed forwards and cascade forward network schemes having Levenberg–Marquardt backpropagation training algorithms. Different learning rates of model training were investigated to determine the optimized training model. The best model (with learning rate 0.2) was selected based on the mean square error (MSE) and the strength of correlation (R) predicted for individual outputs. The model predicted very well the target outputs in both conventional swirl combustion and distributed combustion regime for wider applicability in a range of applications. A very strong correlation was predicted by the current ANN model for the overall data as indicated by the R value of 0.9842. Furthermore, the results obtained with Bayesian Regularization backpropagation method demonstrated better prediction than those from Levenberg–Marquardt algorithm.

Effect of air flow rate distribution and flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration

This study investigates the effect of non-uniform distribution of the air inlet flow rate and change of air flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration. This study considers three patterns of air inlet flow rate in the transverse direction of each stack, and five patterns of air inlet flow rate in the stacking direction. The software package for simulation is reliable through an accuracy comparison, and it analyzes the current density, temperature, and thermal stress distribution of a SOFC stack with 20 layers. The results show that the progressively increasing profile of the air inlet flow rate along the x direction drops the cell thermal stress of a SOFC unit. Moreover, the non-uniform profile of air inlet flow rate in the stacking direction affects the position of the region with high thermal stress of the SOFC stack, and changing flow direction of the air obviously drops down the thermal stress without affecting the power generation of the SOFC stack.

Experimental and numerical study of PCM storage integrated with HVAC system for energy flexibility

This paper presents both experimental and numerical studies of PCM storage integrated with an HVAC system. The experiments focus on PCM storage in 3 different sizes, and study the temperature change in the PCM storage during the charge and discharge period, the impact of the PCM quantity on the charge and discharge rates of the PCM storage and the impact of the discharge air temperature and airflow rate on the discharge rate. The main conclusions are that the temperature effectiveness of the PCM storage depends more on the PCM quantity than the discharge inlet air temperature and airflow rate. The air path in the PCM storage should not be too long to achieve the longer PCM activation in time. The storage with 36 pieces of PCM plates and latent storage capacity of 5.23 MJ can be charged/discharged fast, with high and stable outlet air temperature (above 28 °C for 3 h), especially during the discharge period. The most promising configuration of the experimental study was chosen for a numerical study the energy flexibility of the HVAC system without PCM and with PCM. A model of the PCM storage integrated with an HVAC system is built with EnergyPlus and validated by experimental data. The study concluded that the HVAC heating setpoint control based on the electricity price without PCM storage has limited cost-saving potential due to the high electricity transmission and tax cost. The PCM storage integrated with an HVAC system can reduce the energy cost by 7 % while obtaining a similar indoor thermal comfort level compared to the HVAC heating setpoint control without PCM storage. The payback time of HVAC with PCM is seven years compared to HVAC system without PCM. The cost reduction of energy flexibility of the system is relatively limited because the electricity transmission cost and electricity tax account for 80% of the total electricity cost in Denmark.

Spray layering of human immunoglobulin G: Optimization of formulation and process parameters

Spray layering is a technique used to apply drug or functional polymers onto carrier beads; in addition, it can be used as an alternative method for protein drying and to layer protein on a multiparticulate delivery system. In this study, the effects of formulation variables and process parameters on human immunoglobulin G (IgG) properties during spray layering were studied. Excipients including polyvinylpyrrolidone (PVP), trehalose, sucrose, L-arginine monohydrochloride were studied for their effects on improving IgG stability during spray layering. Process parameters including protein solution feed rate, inlet air temperature, inlet air flow rate, and atomization pressure of spray solution were studied using 24 full factorial design with three replicated center points. Adding PVP into the formulation significantly decreased the turbidity of the reconstitution solution and increased the IgG recovery. Adding trehalose, sucrose, or arginine further improved protein recovery after reconstitution and decreased the percentage of IgG aggregation. The Design of Experiments (DOE) results showed no significant effects from the four process factors on the process yield and IgG protein recovery in the range of parameters studied. All main factors except atomization pressure had significant effects on monomer percentage, among which air flow represented the most significant influence. In addition, the inlet air temperature had significant effects on the in vitro binding activity of IgG after spray layering. By optimizing the formulation, we were able to recover the most spray layered IgG and reduce the IgG aggregation during the process. The DOE studies gave insight into how process variables affect the spray layered products.

Experimental Investigation of the Cooling Effect Generated by a Heat Sink Integrated Thermoelectric-Based U-Shaped Air-Conditioning System

Over the past years, thermoelectric refrigeration has attracted considerable attention due to its compact size, reliability, and environmental friendliness. Traditional refrigeration systems use greenhouse gases, which significantly impacts our environment. Therefore, in this work, a thermoelectric cooler prototype refrigeration system, a solid-state device causing no harm to the environment, was constructed and tested experimentally. A heat sink was attached to the cold side of the thermoelectric cooler (TEC) to cool the air passing through the heat sink. In contrast, a cold plate was attached to the hot side of TEC to remove the generated heat with the help of the liquid circulating in the aluminium cold plate. Experiments were carried out by varying parameters such as input current to the TEC module, inlet air flow rate, water flow rate through the cold plate, etc. The experimental results indicate that the cooling effect is increased by approximately 40%, increasing current from 2A to 8A. However, the cooling effect was decreased with increasing inlet airflow rate by 58% when airflow rate increased from 2.25 m/s to 3.55 m/s. However, the system performance shows approximately 35% increment with an increase in fan speed. Furthermore, a decrease in the water flow rate from 3.04 L/m to 1.80 L/m showed a slight increment in the cooling by 15%.

Air preheating potential with high Opaque Ventilated Façade under natural and forced convection

Opaque ventilated façades (OVF) are increasingly used in building envelope because of their positive impact on building energy efficiency. Usually, air flow is driven by natural ventilation. Recently, there were some attempts to drive air flow mechanically to preheat or precool air in combination with HVAC, Heat pump or Latent Heat Thermal Energy Storage (LHTES) systems. In this framework, an experimental real-scale module of an OVF was built (1.9 m width and 3.5 m height). In this study, OVF is tested during autumn under natural and under forced convection by means of ventilator placed at cavity outlet. Inlet air flowrate are changed from day to day or during the day. For each test, temperature, air velocity, air flow rate and thermal flux are monitored at different locations of OVF. Their analysis shows that collector efficiency and amount of collected energy depend mainly on cavity air flow rate. The measurements are compared to simulation results obtained from two thermal models describing OVF: Trnsys Type 1230 and home-developed pseudo 2D. A good agreement is found for air temperature at cavity outlet while differences are observed in opaque layers due to modelling assumptions. Last, sensitivity analysis on two design parameters is carried out.

Numerical study on the impact of mucus layer and inlet air-temperatures on the particle deposition in a highly idealized mouth-throat model using LES

Presence of mucus layer and inlet air temperature variations can significantly affect the extent of particle transport and deposition in the mouth-throat airway for aerosol drug delivery applications. In addition, higher inlet air temperature can lead to thermal injuries as well. The main goal of the present paper is to investigate these effects in a highly idealized mouth-throat geometry in detail. Large eddy simulation was performed to accurately predict the air flow-fields and a Lagrangian particle tracking model has been employed to capture the particle deposition efficiencies and patterns. The effects of three different inlet air temperatures (15 °C, 26.7 °C and 45 °C) and three different particle sizes (3 μm, 5 μm and 6 μm) have been studied for inlet flow rates of 15 L/min and 30 L/min with and without mucus layer in the present investigation. Detailed velocity and temperature fields, as well as, particle deposition efficiencies and patterns were analyzed and it has been found out that (a) the particle deposition efficiencies varied significantly with changes in inlet air temperature and flow rates, particle diameters and in the presence of mucus layer, (b) the presence of recirculation zones and secondary vortices determined the rate of particle deposition at different inhalation flow rates and inlet air temperatures, and (c) the changes in temperature distribution near the mouth-throat wall in the presence of mucus layer have a dominant effect on particle deposition as compared to inertial deposition. The findings of the present work will provide useful information in understanding the heat transfer effects on particle transport and deposition for the design of pulmonary drug delivery devices under the influence of various environmental and human factors.

Fluidization characterization in the ConSigma 25 dryer via process data – A method of advanced quality assurance in continuous manufacturing

Wet granulation lines in pharmaceutical manufacturing facilities typically comprise a dryer that removes the excess moisture content after wet granulation. In this study, a semi-continuous dryer installed in the ConsiGma 25 wet granulation line was investigated. The goal was to highlight specific characteristics of this type of dryer, utilizing the available process data and the corresponding data obtained via material characterization. This paper addresses typical effects and issues associated with the dryer’s setup and operation (e.g., unexpected cell temperature profiles, the effects of air flow and temperature on the granule properties, variations in the granule moisture between the dryer cells). Since in many situations the liquid-to-solid ratio is based on the properties of granules after the granulation step, the selection of inlet air flow rate and the inlet air temperature of the dryer as well as the overall line throughput (affecting the cell fill level in the dryer) are of particular interest from a practical point of view. This paper discusses these issues and provides suggestions on how to address them when setting up the process. A novel approach for characterizing the fluidization inside the dryer by means of quantifying the “smoothness” of the temperature profile is proposed. The paper should be viewed as a hands-on guideline, which highlights possible pitfalls during the process setup and offers solutions.

Structure Optimization of Battery Thermal Management Systems Using Sensitivity Analysis and Stud Genetic Algorithms

Battery thermal management systems (BTMS) are hugely important in enhancing the lifecycle of batteries and promoting the development of electric vehicles. The cooling effect of BTMS can be improved by optimizing its structural parameters. In this paper, flow resistance and heat dissipation models were used to optimize the structure of BTMS, which were more efficient than the computational fluid dynamics method. Subsequently, five structural parameters that affect the temperature inside the battery pack were analyzed using single-factor sensitivity analysis under different inlet airflow rates, and three structural parameters were selected as the constraints of a stud genetic algorithm. In this stud genetic algorithm, the maximal temperature difference obtained by the heat dissipation model was within 5K as the constraint function, where the objective function minimized the overall area of the battery pack. The BTMS optimized by the stud genetic algorithm was reduced by 16% in the maximal temperature difference and saved 6% of the battery package area compared with the original BTMS. It can be concluded that the stud genetic algorithm combined with the flow resistance network and heat dissipation models can quickly and efficiently optimize the air-cooled BTMS to improve the cooling performance.