Inlet Air Temperature Research Articles

Energy-Efficiency-Oriented Spatial Configuration of VRV Outdoor Units in an Equipment Layer Under Background Wind Conditions

This study provides a spatial configuration method to improve the cooling efficiency of multiple VRV outdoor units placed on equipment layers with high floors. Relevant factors include wind parameters, the placement of multiple outdoor units, and louver. A total of 96 cases were designed. CFD simulations were used to obtain the inlet air temperature distributions of multiple outdoor units and then calculate their cooling efficiency. The results found that these factors have effects on the average cooling efficiency of outdoor units in a single row to a certain extent. The influencing degrees of these factors, from large to small, were the louver angle, wind parameters, and the placement of multiple outdoor units. When the cooling efficiency of outdoor units was maximum and the louver angle was 15°, the louvers could be oriented perpendicular to the dominant wind direction (90°) when wind speed was ≥6 m/s, and the unit spacing was 600 mm. Based on this, when the number of outdoor units was expanded in the limited space, staggered arrangements with different directions of heat exchange surfaces were a recommended optimization layout. This study provides technical support for improving the working efficiency of VRV outdoor units in an equipment layer.

Exploring the Potential of Spray-Dried Blackberry Powder Enriched with Zinc and Folic Acid as a Nutritional Alternative for Children and Pregnant Women

Currently, strategies to achieve the Sustainable Development Goals (SDGs) are being sought worldwide. Accordingly, this study seeks to contribute to achieving SDGs 2 (Zero Hunger) and 3 (Good Health and Well-being) by addressing nutritional deficiencies in pregnant women and children. These vulnerable populations worldwide have malnutrition problems associated with a lack of zinc and folic acid, causing them health problems. This research aimed to develop a blackberry powder fortified with zinc and folic acid obtained by spray drying as a nutritional alternative for children and pregnant women. The blackberry was characterized according to the AOAC, an optimization of the spray drying process with a central composite experimental design. The powder’s bulk and tapped density, solubility, and anthocyanin content were determined. The variation in zinc and folic acid content over a storage period was measured. The moisture content of the fresh blackberries was 89%. The solubility and anthocyanin content of blackberry powder were 86% and 0.263 mg cyanidin-3-glucose/g, respectively. The optimal spray drying conditions were: 23.6% solid content and an air inlet temperature of 167.92 °C. The bulk density of the powder did not change with storage time (p > 0.05); the zinc and folic acid content in blackberry powder was 144 and 90 (µg/100 g), respectively. A blackberry powder fortified with zinc and folic acid was obtained by spray drying, guaranteeing 30% of the daily nutritional requirement for pregnant women and children, in a 50-gram portion of powder.

Wood hemicelluloses as protective materials for preserving the viability of probiotic Lacticaseibacillus rhamnosus GG during spray drying

Wood hemicelluloses from forest industry side-streams are promising economic and sustainable alternatives for encapsulating bioactive compounds. This study explores their suitability for probiotic encapsulation, specifically for maintaining cell viability and structure. The ability of galactoglucomannans (GGM) and glucuronoxylans (GX) to support the survival of Lacticaseibacillus rhamnosus GG (LGG) during spray drying at solid feed concentrations of 15 and 20 % and inlet air temperatures of 105 and 140 °C (outlet air temperature of 50 °C) was investigated and compared to the results obtained using maltodextrin (MD). Across all investigated conditions, LGG survival rates exceeded 85 % (>107 cfu/g) in GX and GGM microcapsule powders, which similar to that in MD microcapsules despite the differences in pH, particle size, and viscosity of their feed dispersions. The GX microcapsules demonstrated the highest process yield (50–58 %), followed by MD (39–51 %). All the microcapsule powders exhibited an amorphous structure consisting of spherical particles with an average diameter of 10 μm, sufficient for LGG accommodation. Atomic force microscopy analysis confirmed the encapsulation of LGG cells within microcapsules with intact rod-shaped chains post-spray drying. Overall, the spray-dried microencapsulation of probiotics using wood hemicelluloses maintains high probiotic viability and offers an eco-friendly, cost-effective alternative to traditional materials.

Tobacco stalk nanofibrillated cellulose: An eco-friendly binder on fluidized bed granulation

The search for new excipients that provide formulation alternatives over existing ones and that are derived from natural resources has advanced over the years. Emerging from this scenario, an important alternative to traditional excipients is nanofibrillated cellulose (NFC), which is generally obtained from agricultural wastes and is a cellulose-rich material. Most of the time, the nanofibers are presented in aqueous dispersions that form a highly entangled network of fibrous particles that exhibit gel-like behavior. Therefore, the present work aimed to explore the gel-like behavior of NFC from tobacco stalks to evaluate it as a binder in a fluid bed granulation process for further application as a pharmaceutical ingredient. The granulation process was carried out using top spray mode with an inlet air temperature of 80 °C, airflow between 9 and 11 mm3 h−1, and atomizing air pressure of 0.7 bar. Povidone (PVP) was used as a standard binder for comparison purposes. The binder systems were sprayed on the powder blend of theophylline and maltodextrin at a feed rate of 3.05 mL⋅min−1. Granule properties, such as yield, moisture content, morphology, label-free Raman imaging, particle size distribution, drug content, and flow properties, were evaluated. The process using NFC provided granules with excellent drug uniformity, low moisture content (<2 %), high yield (>92 %), and passable flow properties. Their behavior was comparable to that of granules prepared with the classical PVP binder system. Therefore, this study opens a perspective for the reuse of NFC from tobacco stalk, an agricultural waste, as an alternative binder for the granulation process, contributing to environmental sustainability.

Study on the double-coil heat exchanger for dehumidification and heating in greenhouses: Modeling, analysis, and optimization

Heat exchangers are widely used in dehumidification and heating technologies owing to their excellent heat transfer performance, however, their dehumidification capability is limited for greenhouse applications. This study evaluates a double-coil heat exchanger (DC-HE) for dehumidification and heating in greenhouses. Humid air undergoes condensation dehumidification through the dehumidifying coil and is then reheated by the heating coil before being released. Using double coils allows for the separate circulation of cold and warm water in their respective paths, handling the latent and sensible heat of the air. In this study, predictive methods for air treatment in a heat exchanger are combined, and theoretical calculations are performed on the DC-HE and validated through experimental investigations. Furthermore, the impact of variables such as air temperature, relative humidity, water temperature and flow rate, and air flow rate on the moisture removal rate (MRR), latent heat ratio (LHR), and heating capacity (qheat) of the DC-HE is analyzed, the effects of these variables on the sensible and latent heat transfer rates are discussed. Finally, the optimal variables for maximizing MRR and LHR are determined using the response surface method and multi-objective genetic algorithm. When the inlet air temperature, relative humidity, cooling-side water temperature, heating-side water temperature, cooling-side water flow rate, heating-side water flow rate, and air flow rate are 11.8 ℃, 95 %, 3 ℃, 30 ℃, 2 m/s, 2 m/s, and 2 m/s, respectively, the DC-HE achieves an MRR of 1.58 g/s, an LHR of 62.2 % and a qheat of 9.99 kW. Compared with other finned tube heat exchangers, the DC-HE enhances the moisture removal capacity and significantly reduces the temperature requirement for the heat source, offering a promising dehumidification and heating technology for greenhouse applications.

A simulation-based optimization of heat pump air circulation evaporating separation system for saline wastewater treatment

Recycling salt and water from saline wastewater is crucial for environmental preservation, resource conservation, and social economy sustainability. The heat pump air circulation evaporating separation (HP-ACES) system for saline wastewater treatment is proposed. Nevertheless, it is discovered that the system evaporation efficiency (SEE) is low and solid crystalline salt does not precipitate during the experiment. Therefore, an established and validated mathematical model of the HP-ACES system is provided and the average relative errors of the system evaporation rate (SER) and SEE are 5.3 % and 7 %, respectively. The theoretical analysis of the non-optimized system indicates that the main cause of the low SEE of the HP-ACES system during the test is incorrect cooling water flow. Hence, the system optimization scheme is presented and the comparison of the HP-ACES system's performances before and after optimization is conducted. Results demonstrate that the SEE of the optimized HP-ACES system has been greatly improved (optimized system: 0.62–2.46 kg/kWh, non-optimized system: 0.77–0.91 kg/kWh). Additionally, there is almost no change in the yield and composition of the solid crystalline salt when the inlet air temperature of spray separation tower is above 90 °C.

Minimally processed yam beam roots fortified with probiotics and phenolic compound from green coffee microencapsulated

Yam beam (Pachyrhizus erosus L.) root, commonly known as jicama, is widely consumed by health-conscious individuals due to its low caloric content. However, its nutritional value is relatively low, despite containing some. To enhance these nutritional properties, jicama can be supplemented with probiotics and antioxidant compounds. In this study, the jicama pieces were coated with an edible layer containing microencapsulated Lactobacillus acidophilus, Bifidobacterium spp. and phenolic compounds derived from green coffee, which were microencapsulated using a double spray drying technique. The probiotics and phenolic compounds were dried using double spray drying with chitosan at 120 and 140 °C. The results showed that the inlet air temperature did not have a statistically significant effect (p ≥ 0.05) on the encapsulation efficiency of probiotics, chlorogenic acid and caffeine content, or antioxidant activity expressed as IC50 value (110 - 116 µg/mL). After 6 d of storage at 4 °C, the jicama supplemented with the microcapsules containing Lactobacillus acidophilus and Bifidobacterium spp. exhibited a reduction in microbial viability by 1 and 2 log CFU/g, respectively. However, the addition of microcapsules allowed a higher concentration of phenolic compounds than the control group. Minimally processed jicama containing microcapsules with probiotics and phenolic compounds could be a functional food, and the reported procedure could be applied for industrial purposes.

A comparative performance study of terminal control strategy for the multi-split backplane cooling system in data centers

Multi-split backplane cooling, a typical rack-level cooling technology, has the advantage of solving local hot-spot problems with huge energy-saving potential. These systems adopt the multi-split mode, and the operation effect is affected by terminal control performance. However, there are factors in the operation process, such as superheat degree (SH), rack airflow, evaporating/condensing pressures, etc., which improve the control complication, particularly under large head load differences among different terminals. Therefore, appreciative control strategies for outlet air temperatures of terminal evaporators, including single-loop control limited by minimum stable superheat degree (SLC) and fan/electronic expansion valve (EEV) double-loop control (DLC), are proposed considering that cooling performance can be affected by both refrigerant flow and airflow. Then, comparative simulation studies are carried out to evaluate energy efficiency, control effect, and feasibility under the condition of different server heat distribution characteristics. Results indicate that the DLC strategy achieves 23 % higher energy efficiency than the SLC strategy with a better temperature control effect when the inlet air temperature (IAT) difference between terminal evaporators is within ±5K. The SLC strategy has better reliability by more stable control of SH at IATs below 42°C, but it may lead to cooling failure when IATs exceed 42°C. An insufficient liquid supply problem may happen to the evaporator adopting the DLC strategy when the IAT is too high, which can be solved by adjusting the pressure differential between the evaporator and condenser. Moreover, the DLC system exhibits intense coupling effects, and how to decouple it is worthy of further study.

Spray Drying of Inca Peanut Meal Protein Hydrolysate to Produce Protein Powder Drink Mix

The optimal conditions (maltodextrin concentration and inlet air temperature) for spray drying Inca peanut meal protein hydrolysate (IMPH) were determined. The maltodextrin concentration was varied at 5, 10 and 15 % by weight, and inlet air temperature was varied at 150, 160 and 170 °C. The IMPH was subjected to spray drying, where the feed solution was atomized into fine droplets and exposed to a hot air stream, leading to rapid drying and the formation of powder. The moisture, protein, yield, water activity and water solubility index (WSI) of IMPH powder were analyzed. The optimal condition for spray drying IMPH powder utilized 10 % maltodextrin and an inlet air temperature of 160 °C. Under these conditions, the moisture, protein, yield and WSI of IMPH powder were 2.93, 36.93, 38.95 and 99.59 %, respectively, while water activity was 0.41. IMPH powder particles were spherical and non-agglomerate. Inca peanut meal protein powder drink mix (IMPD) with cocoa flavor was the most acceptable. The IMPD with cocoa flavor could be promoted as a high protein and high dietary fiber product. It could be kept at 35 ± 2 °C for 12 weeks, whilst retaining good microbiological properties. HIGHLIGHTS The optimal conditions for spray drying Inca peanut meal protein hydrolysate (IMPH) were determined to be 10% maltodextrin and an inlet air temperature of 160 °C. This resulted in high yield, protein content, and water solubility, while keeping moisture and water activity low. IMPH powder had spherical, non-agglomerated particles, and cocoa-flavored Inca peanut protein powder drink mix (IMPD) was the most preferred in sensory evaluations. The IMPD with cocoa flavor was identified as a high-protein, high-dietary-fiber product, suitable for storage at 35 °C for up to 12 weeks while maintaining good microbiological quality. The study highlights the nutritional benefits of the cocoa-flavored IMPD, which includes essential amino acids, omega-3 fatty acids, and antioxidant properties. GRAPHICAL ABSTRACT

Enhancement of air-side heat transfer in crossflow heat exchangers using auto-fluttering reeds

Thin film aeroelastically fluttering reeds are investigated as a mechanism to enhance air-side heat transfer in an industry relevant crossflow heat exchanger that can reject over 10kW of heat. Nusselt number and friction factor measurements are made in a temperature- and humidity- controlled wind tunnel over a range of air inlet temperatures and flow rates spanning an air-side Reynolds number range of 800<Re<6000 without the reeds and 1200<Re<3400 with the reeds installed in the heat exchanger fin channels. Experiments are conducted with a set of 1440, 50.8-mm long, 15.9-mm wide, rectangular Mylar reeds installed in the heat exchanger fin channels. The fluttering reeds enhanced heat transfer by up to 60% with a maximum friction factor penalty of 200%. Two different reed thicknesses are investigated, 0.013mm and 0.025mm. Increasing the reed thickness yielded similar heat transfer performance while decreasing the friction factor penalty, indicating that it may be possible to decrease the pressure drop penalty through geometric optimization. Correlations for the reed Strouhal number and the reed-enhanced Nusselt number and friction factor are developed as a function of relevant dimensionless parameters.

Impacts of non-uniform airflow over gas cooler on the performance of transcritical CO2 air conditioning

The air flowrate and air inlet temperature over gas cooler in transcritical CO2 air conditioning for vehicles are easily unevenly distributed due to the influence of upstream obstacles. The unevenly distributed airflow affects heat exchange between CO2 and air, thus influencing the cooling capacity and power consumption of the air conditioning system. This study delves into the implications of such non-uniform airflow on the operational performance of transcritical CO2 air conditioning through simulation analysis. It elucidates the mechanisms by which the uneven distribution pattern, uneven distribution direction and non-uniformity affect the cooling capacity of transcritical CO2 air conditioning system. Moreover, the conditions of inhomogeneous airflow for enhanced heat transfer are explored by decoupling inhomogeneous flow rate and inhomogeneous temperature. Results indicate that non-uniform airflow of air temperature distributed as TB-HT (high in top and low in bottom) and air flowrate as TB-HB (high in bottom and low in top) increases the cooling capacity of 27.7 % at non-uniformity of 55 %. Conversely, uneven airflow of flowrate and temperature both distributed as LR-HL (high in left and low in right) at 40 % non-uniformity leads to a wastage of compressor power up to 1/2. These findings reveal the dual impacts of non-uniform airflow on the performance of transcritical CO2 air conditioning system, which emphasizes the importance of considering these impacts when designing automotive CO2 air conditioning systems.

A comparative study of RSM and ANN models for predicting spray drying conditions for encapsulation of Lactobacillus casei

AbstractBackground and ObjectivesThe aim of this study was to develop a wall material using pea protein isolate and pectin to optimize the encapsulation of Lactobacillus casei by spray drying. Response surface methodology (RSM) and artificial neural network (ANN) were used to analyze the effect of processing parameters.FindingsThe results showed that both RSM and ANN could be used to successfully characterize the experimental data, although ANN demonstrated greater predictive accuracy than RSM due to a higher R2 and lower mean square error (MSE).ConclusionANN was observed to show more suitability than RSM. The encapsulation efficiency (90.7%), yield (45.5%), and wettability (169 s) of spray‐dried probiotic powder obtained under optimal spray drying conditions (inlet air temperature (132°C); feed flow rate (9.5 mL/min) and pea protein isolate concentration (7.1%)) were observed to be not significantly different (p &lt; .05) from predicted values for all three parameters, demonstrating the validity of applied model.Significance and NoveltyIn this study, production technology of vegan base probiotic powder has been developed using mathematical modeling through the spray‐drying method. Therefore, this data can be useful for food processing industries to develop a high‐quality probiotic powder through spray drying.

Inclined Installation Effect on the Offset Strip Finned Heat Exchanger Designed for a Hybrid Electric Propulsion System in Electric Vertical Take-Off and Landing

The plate-fin heat exchanger was designed for the liquid cooling thermal management system of the hybrid electric propulsion system for an electric vertical take-off and landing (eVTOL) vehicle. The offset-strip fin design was applied, and the performance of the heat exchanger was evaluated, particularly with respect to the inclination of the airflow entering the heat exchanger. The estimated performance during the design phase matched well with the experimental results. The inclination of the heat exchanger had a minimal effect on thermal performance, with a slight increase in performance as the inclination increased. However, the pressure difference along the airflow was affected, likely increasing as the inclination increased. The sensitivity of various parameters on coolant temperature was also investigated. The air inlet temperature had a significant effect on coolant temperature, followed by the coolant flow rate. Therefore, when designing the thermal management system, careful consideration should be given to the ambient air temperature and coolant flow rate.

Heat and mass transfer performance of multi-solute electroplating wastewater in spray evaporation separation process

Electroplating wastewater is complex in composition and contains many harmful substances. Based on the single droplet heat and mass transfer method, a one-dimensional mathematical model for the evaporation separation heat and mass transfer process of multi-solute electroplating wastewater is established. In order to validate the model, the experimental system of evaporation separation tower is established, and Nusselt numbers corresponding to metal ion solutions are fitted, reliabilities of models are also verified. The maximum relative errors of mathematical models are within 10.0 %. In addition, effects of the type and concentration of metal ions and air inlet temperature on heat and mass transfer characteristics of spray separation tower are investigated. Experimental results show that when the wastewater inlet concentration is the same, the improvement effects of increasing air inlet temperature on evaporation and separation performance from high to low are ZnCl2, CuCl2, and NiCl2 solutions. When the air inlet temperature increases from 90 °C to 130 °C, the evaporation speed of ZnCl2, CuCl2 and NiCl2 solutions increase by 90.3 %, 84.3 % and 45.7 %, respectively. When the air inlet temperature is the same, with the increase of wastewater inlet concentration, the evaporation separation performance of electroplating wastewater in descending order is ZnCl2, CuCl2, and NiCl2 solutions.

Numerical and artificial neural network inspired study on step-like-plenum battery thermal management system

This study leverage numerical simulation (NS) and artificial neural network (ANN) capabilities to carry out additional investigations on step-like plenum battery thermal management system (BTMS). Different cooling strategies have been developed over the years in BTMSs’ design. Yet, air-cooling strategies still remains relevant, especially in battery-powered aircrafts, where light-weight is important and air is the preferred cooling fluid. Hence, additional study become necessary especially on the step-like plenum design to provide more insight on the performance of the design by considering several number of step, varied air inlet temperature and velocity. Computational fluid dynamics (CFD) approach was employed to obtained results for different number of step; Ns = 1, 3, 4, 7, 9, 15 and 19, varied air inlet temperature; Ti = 278, 298 and 318 K, and varied air inlet velocity; Vi = 3, 3.5, 4, 5 and 6 m/s. Artificial Neural Network (ANN) approach was then employed to predict the BTMSs’ performance for additional values of Ti and Vi. Minimum temperature (Tmin), maximum temperature (Tmax), maximum temperature difference (ΔTmax) and pressure drop (ΔP) were computed. By comparing the CFD results with the result predicted by the ANN, the percentage difference, for the entire dataset were 0.01 %, 0.005 %, 1 % and 0.14 % for Tmax, Tmin ΔTmax and ΔP, respectively. Based on the optimum design parameters predicted using ANN, for Tmax = 299.24 comprises Ns = 4, Vi = 6 m/s and Ti = 278 K, while for ΔP, comprises Ns = 1, Vi = 3 m/s and Ti = 318 K.

Energy management of residential buildings using innovative passive techniques

Abstract Recently, efforts on sustainability and energy savings in buildings have increased due to the growing global awareness of the energy use of buildings and the negative impacts of carbon dioxide emissions on climate change. As a result, it is critical to propose effective strategies to reduce such energy consumption. The goal of this project is to advance the idea of net-zero energy buildings as a worldwide mitigation method for climate change. Thus, a numerical model was developed and validated to investigate the passive cooling capabilities of an innovative phase change material (PCM)-based phase cube in residential buildings. The proposed phase cube includes six various PCM-compact storage module (PCM-CSM) configurations including Rubitherm’s SP-24E plates (Horizontal), Half Circular Inline, Half Circular Staggered, Vertical plates, Inline Cylindrical and Staggered Cylindrical compact storage modules. All the proposed designs were numerically simulated, and the obtained results were compared and analysed at an inlet air temperature and velocity of 35°C, and 4m/s, respectively and each phase cube contained the same mass of Rubitherm’s SP-24E PCM, which was 30.326 kg. The results showed that the Horizontal, Half Circular Inline and Vertical phase cubes can absorb heat at a higher rate from fresh air at nearly 496.19w, 465.9w and 458.16w, respectively translating the lowest outlet air temperature of about 25°C from the cube. Integrating such phase cubes into residential buildings for indoor passive air cooling substantially decreased the building cooling loads, resulting in reduced electric energy consumption by the air conditioning system.

Unsteady-state entropy generation analysis of the counter-flow dew-point evaporative coolers

The surging demand for air conditioning, especially in hot climates, underscores the urgency of strategies aimed at curbing fossil fuel reliance and fostering energy saving strategy. Despite the longstanding utility and advantages of the conventional mechanical vapor compression refrigeration system, sustainability hurdles persist owing to its pronounced electricity demand. While evaporative cooling, harnessing water evaporation, emerges as a more efficient alternative, its efficacy is contingent upon environmental conditions. Addressing this, dew-point evaporative cooling (DPEC) presents an innovative direction, showcasing superior efficiency by directing supply air into a wet channel. This study delves into the thermodynamic losses within a counter-flow configured DPEC system, employing a transient entropy generation model rooted in the second law of thermodynamics to provide a comprehensive analysis of DPEC’s performance. Key findings that emerged from this study reveal that (1) the transient entropy generation is intricately distributed across different layers of the dew point evaporative cooling (DPEC) system, including dry air, wet air, the channel plate, and the water film; (2) Parametric analyses highlight the significant impact of factors on entropy generation, inlet air temperature has a minimal effect on system efficiency, but higher temperatures increase thermal losses. Excessive humidity limits evaporative potential, while low humidity significantly increases entropy generation. The system performs optimally at a working ratio of 0.3 and lower air velocities (within the inlet air velocity range of 0.6 to 2.2 m/s). Channel length has little impact, while the system is more sensitive to channel height, with a height of 2.5–3.5 mm being conducive to better performance. Experimental validation demonstrates the model’s accuracy in predicting system performance. The research contributes to a deeper understanding of DPEC systems, offering insights for achieving optimal operating conditions and enhancing overall efficiency in the pursuit of sustainable development.

A full-scale CFD model of scavenge air inlet temperature on two-stroke marine diesel engine combustion and exhaust emission characteristics

Most ships in the maritime transport sector are equipped with large two-stroke marine diesel engines in their propulsion systems. Therefore, ensuring stable and long-term operation of these engines is crucial to maintaining freight transportation. The design of the ship's machinery, particularly the diesel engine, is a crucial step in achieving this goal. Computational Fluid Dynamics (CFD) tools can be used to achieve this goal. This article presents a full-scale CFD study on the effect of different scavenge air inlet temperatures (300, 312, 330 and 340 K) on the combustion process and generation of exhaust emissions in a two-stroke marine diesel engine using ANSYS Forte software. Regarding the cylinder pressure, the presented model agrees well with experimental data. The maximum cylinder pressure decreases as the scavenge air inlet temperature increases, whereas the maximum cylinder temperature increases as the scavenge air inlet temperature increases. The maximum NOX, CO and UHC emission values are calculated to be 2256.5, 20375.8 and 3743.9 ppm, respectively, at a scavenge air inlet temperature of 340 K. Due to the higher combustion temperature caused by the increasing scavenge air inlet temperature, it is observed that the exhaust emission levels increase.

Study of inhalation micropowders obtained by spray drying

Objectives. To study the influence of the type of matrix-forming material and excipients concentration, spray drying parameters on the characteristics of the powder for inhalation, as well as to investigate the inhalation compositions for stability under stressful conditions.Methods. Spray drying was used to obtain powder compositions with the required characteristics for inhalation therapy. Microscopic and analytical studies of powders were carried out. Statistical analysis made it possible to estimate the influence of factors on the powder characteristics and rank them by importance. The stability of spray dried powders was studied.Results. The optimal parameters for obtaining powders for inhalation were found by means of mathematical statistics: air flow rate was 37 m3/h; compressed air flow rate — 601 L/h; inlet air temperature — 150°C; solution flow rate — 45% of the power of the peristaltic pump (16.3 g/min for this composition); L-leucine concentration — 10 wt %; ratio of components of the matrix polyvinylpyrrolidone K-30/D-mannitol = 1 : 3. Under these conditions, as well as by means of 2 experiments additionally selected from the research design, a composition with isoniazid as an active substance was spray dried. The resulting powders were analyzed, in order to confirm the correctness of the recommended parameters.Conclusions. The selection of compositions and spray drying conditions involves multiple criteria. The characteristics of the powder for inhalation may deteriorate significantly during long-term storage. The optimal parameters were determined using statistical analysis and confirmed by experimental data.

Experimental study of the optimal design and performance of a mixed-flow dew-point indirect evaporative cooler

Evaporative cooling technologies represent a promising alternative to face the emerging cooling energy poverty, owing to their low production and operative costs. High performance can be achieved through more complex designs, such as dew point indirect evaporative cooling (DIEC) systems. Recent literature explores improvements on these systems, like flow configuration, materials, and water distribution. This study proposes a compact mixed-flow DIEC system made of polycarbonate plates covered with two possible wicking materials. Three water distribution systems are also studied. The prototypes are experimentally characterised by varying the inlet air temperature, humidity, volume flow, and working-to-intake air ratio. The best performing design is evaluated in terms of temperature drop, dew-point effectiveness, wet-bulb effectiveness, and cooling capacity. Results are consistent with those in the literature for equivalent heat transfer areas. The use of a wicking material improves the cooling capacity by up to 1.45. The type of material is less relevant, which enables to select the most economic and accessible option. External nozzles for water distribution offers temperature drops of more than 1 °C and better cooling capacities of approximately 100 W than inlet water distributors.