Hot Air Flow Rate Research Articles

Enhancing the quality attributes of mint medicinal plant (Mentha spicata L.) through simultaneous combined ozone and infrared drying

AbstractMedicinal plants are widely used in various traditional and modern medical methods due to their therapeutic properties. Drying is a common method used to preserve the biochemical compounds of medicinal plants. Still, conventional drying methods can lead to the loss of active compounds due to exposure to high temperatures. This research aimed to design and construct an ozone generator for use in a combined dryer and evaluate the ozone, temperature, and hot air flow rate on the quality properties of mint (Mentha spicata L.). Drying experiments were conducted at varying temperatures, air flow speeds, and ozone levels. Results indicated that increasing temperature reduced total phenol and flavonoid content while increasing antioxidant capacity. Higher airflow speed positively influenced total phenol, total flavonoid content and antioxidant potency but reduced drying time. Ozone exposure increased total phenol, flavonoid content, antioxidant activity, and had minimal effect on drying time. Optimization revealed that a temperature of 52.47°C, air flow rate of 1.5 m/s, and 90.37% ozone concentration yielded favorable outcomes, including enhanced phenolic and flavonoid content, antioxidant power, and decreased energy consumption. Compared to other drying methods, the proposed ozone‐enhanced method proved superior in preserving bioactive compounds and maintaining a reasonable drying time. Overall, the research highlights the potential of ozone‐assisted drying for optimizing the quality of medicinal plants during preservation.Practical ApplicationThe paper introduces a novel and efficient method for preserving the quality of medicinal mint. By concurrently applying ozone and infrared drying techniques, this approach aims to capitalize on their synergistic effects in maintaining the plant's beneficial compounds. Ozone acts as a natural antimicrobial agent, preserving the plant's integrity, while infrared drying expedites the process without compromising the phytochemical profile. This innovative method not only ensures microbial safety and extended shelf life but also enhances the mint's aroma, flavor, and nutrient retention. The practical application of this combined technique holds promise for pharmaceutical and herbal industries, providing a valuable approach for optimizing the drying process and preserving the medicinal attributes of Mentha spicata L.

Experimental investigation on the thermal appraisal and sustainability indicator of heat pipe-based indirect solar dryer during Giloy (Tinospora cardifolia) drying

Tinospora cordifolia (Giloy) is an anti-periodic, anti-inflammatory, anti-arthritic and anti-diabetic agent in folk medicine. As per ayurveda giloy boosts the immune system. Current work investigates an evacuated tubes solar dryer with heat pipes (ETSD_HP) to develop a sustainable drying method for medicinal plants, i.e., Giloy stem. Experiments are conducted at different air mass flow rates viz. 0.010 kg/s (Ṁ1), 0.0125 kg/s (Ṁ2), and 0.015 kg/s (Ṁ3). Thermal profiling, drying characteristics, mass transfer parameter, energy and exergy analysis were conducted. The initial moisture content of stem was 81.68±0.37 % (wb) and reduced to 8.75 % in the minimum time of 12 h at 0.0125 kg/s. Existing models for drying kinetics are evaluated, and a new model was developed for predicting the moisture ratio. The highest energy efficiency was 42 % for drying under Ṁ3. The exergy efficiency of the drying process increases as the hot air flow rate increases from Ṁ1 to Ṁ3. The improvement potential (IP), as a sustainability indicator, was in the range of 10.76 to 43.75 W, 17.09 to 59.44 W, and 16.79 to 77.15 W for Ṁ1, Ṁ2, and Ṁ3, respectively. The highest moisture diffusivity was found for Ṁ2, around 1.17 times more than Ṁ1.

A New Strategy for Consumption of Functional Lipids from Ericerus pela (Chavannes): Study on Microcapsules and Effervescent Tablets Containing Insect Wax-Derived Policosanol.

In this study, we addressed various challenges associated with the consumption of functional lipids from the Ericerus pela (Chavannes), including unfavorable taste, insolubility in water, difficulty in oral intake, low bioavailability, and low psychological acceptance. Our study focused on the microencapsulation of policosanol, the key active component of insect wax, which is a mixture of functional lipids secreted by the Ericerus pela (Chavannes). We developed two innovative policosanol products, microcapsules, and effervescent tablets, and optimized their preparation conditions. We successfully prepared microcapsules containing insect wax-derived policosanol using the spray-drying method. We achieved 92.09% microencapsulation efficiency and 61.67% powder yield under the following conditions: maltodextrin, starch sodium octenyl succinate, and (2-hydroxy)propyl-β-cyclodextrin (HPβCD) at a ratio of 1:1:1, core-to-wall materials at a ratio of 1:10, 15% solid content, spray dryer feed temperature at 60 °C, inlet air temperature at 140 °C, and hot-air flow rate at 0.5 m3/min. The microcapsules exhibited a regular spherical shape with a minimal water content (1.82%) and rapid dispersion in water (within 143.5 s). These microcapsules released policosanol rapidly in simulated stomach fluid. Moreover, effervescent tablets were prepared using the policosanol-containing microcapsules. The tablets showed low friability (0.32%), quick disintegration in water (within 99.5 s), and high bubble volume. The microcapsules and effervescent tablets developed in this study presented effective solutions to the insolubility of policosanol in water. These products were portable and offered customizable tastes to address the psychological discomfort related to insect-based foods, thus providing a novel strategy for the consumption and secondary processing of insect lipids.

Development, testing and design optimisation of a water and R134a based thermosyphon heat exchanger for air-water heat recovery systems

Heat pipes find their increasing uses in heat recovery and energy saving in thermal systems. Our work involves the designing, building, and testing of a heat pipe heat exchanger made of 28 copper thermosyphons. We investigated the use of distilled water and R134a as the thermosyphons’ working fluid with optimisation. The thermosyphons were arranged into four rows by seven columns with a hot air flow at the evaporator and a cooling water flow at the condenser. The performance was tested in three working fluid cases: distilled water, R134a, and a hybrid. The hot air flowrate was varied and at temperatures of 80 °C, 110 °C, and 140 °C to investigate the performance. The results show that increasing the air flow temperature increased the effectiveness. Optimisation was examined using the ε-NTU analysis and revealed that R134a offered the highest effectiveness with a relatively small NTU. Tested using three values of Cr, highest effectiveness of 30%, 51% and 40% for distilled water, R134a, and the hybrid respectively, was achieved across all fluid cases at Cr = 0.15. A Reynolds analysis performed to compare the effect of relative flows over the evaporator and condenser showed that increasing Reh/Rec, increased the heat transfer at the condenser and the overall effectiveness. At Reh/Rec = 2500, heat transfer was 500 W, 2000 W and 800 W for distilled water, R134a, and the hybrid respectively. Our work could potentially be useful in the designing and optimising of a thermosyphon heat exchanger for saving energy in air-water heat handling applications.

Icing tests for the anti-icing structure with exterior hot air film heating

An improved ice protection system using exterior hot air film heating has been brought out for those structurers manufactured with lower thermal conductivity materials, where the interior hot jet impact heat transfer combines with the exterior hot air film heating. To verify the effectiveness of our design methods for such type of ice protection system, the test specimen manufactured with composite materials and supporting structures are designed, and the icing tests in the icing wind tunnel are carried out for the ice meteorological conditions given by the military standard and airworthiness regulations. Simulations are conducted to evaluate the hot air flow distribution of each slot of the actual test specimen. The test results are very consistent with the prediction results of the design method under the combination of different hot air flow rates and temperature, and various possible icing forms are accurately predicted, from trace icing to severe icing. The practicability of the anti-icing structure using the hot air film heating and the effectiveness of the system design method were verified by tests and showed good application prospects.

Research on atomization evaporation characteristics and parameter optimization of a novel spray evaporation desalting system

Rotary spray evaporation technology has received particular attention due to its superiority in high-salinity wastewater's zero liquid discharge (ZLD). This research develops a new type of high-efficiency and low-energy-consumption rotary spray evaporation tower. The effects of atomization speed, feed flow, feed liquid concentration, hot air temperature, and hot air velocity on high-salinity wastewater's atomization and evaporation characteristics were studied. The numerical results show that the atomization speed can reduce the droplet spraying to the tower wall to reduce the sticky wall phenomenon and prolong the droplet residence time to increase the evaporation rate. By controlling the atomization speed, feed flow, and feed concentration, the droplet SMD can be reduced by 6.0 % to 37.3 % so that the droplets are evenly dispersed. With reasonable hot air temperature and speed, the outlet temperature drops by 19.1 % to 29.0 %, and the evaporation rate increases by 8.7 % to 11.8 %. The optimal working conditions are 16,000 r/min atomization disk speed, 10 kg/h feed flow, 433 K hot air temperature, 10 m/s hot air flow rate, and 93.2 % evaporation rate at this time. The results show that the rotary spray evaporation technology can be a powerful means of ZLD of high-salinity wastewater.

Effect of the modification of spray drying parameters on the fabrication of bovine-derived hydroxyapatite microspheres for biomedical applications

In this work, the effect of the spray dryer parameters on bovine-derived hydroxyapatite (BHAp) was studied to fabricate microspheres with controlled particle size distribution and morphology. A factorial design was implemented to establish the impact of spray drying process parameters on the final BHAp powder properties. The critical process factors were solid content in the slurry, atomization pressure, and hot air flow rate, whereas the studied experimental outputs were particle size distribution and morphology, characterized by laser diffraction and scanning electron microscopy, respectively. Additionally, the Ca/P molar ratio was evaluated from X-ray diffraction data. The obtained results showed a strong influence of the atomization pressure and the solid slurry content on the particle size distribution (increasing from 2.56 ± 0.02 µm to 32.46 ± 0.78 µm) and particle morphology (with an increased circularity from 0.3502 ± 0.0172 to 0.8688 ± 0.0039), being both properties suitable for thermal spray (TS) applications. Moreover, the BHAp crystalline structure and Ca/P molar ratio did not present any changes with the spray drying process parameters employed. Finally, it was found that magnesium was preserved in the spray dried particles, the former being also present in the starting powder feedstock.

Application of self-adaptive temperature recognition in cold-start of an air-cooled proton exchange membrane fuel cell stack

The Self-adaptive control of the temperature can achieve the start of fuel cell at different operating temperatures, which is very important for the successful cold-start of the air-cooled PEMFC. The temperature distribution characteristics during the cold-start process were analyzed based on adaptive temperature recognition control in this paper. Preheating model and cold-start model were established and the optimal balance between the hot air flow rate and the temperature required to promote a uniform temperature distribution in the stack was explored in the preheating stage. Finally, the non-equilibrium mass transfer, as well as the temperature rise in the catalyst layer and gas diffusion layer with different current densities, were analyzed in the start-up stage. The results indicate that the air-cooled PEMFC stack can be successfully started up at -40 °C within 10 min by means of external gas heating. The current density and air velocity have significant impacts on the temperature of air-cooled PEMFC stack. Dynamic analysis of air-cooled PEMFCs and real-time monitoring are suitable for machine learning and self-adaptive control to set the operation parameters to achieve successful cold start. Optimize the matching of load current and cathode inlet speed to achieve thermal management in low temperature environment.

Humidification-dehumidification solar desalination system using porous activated carbon tubes as a humidifier

The integration of solar water desalination utilizing humidification dehumidification (HDH) techniques with a cooling system (CS) and hot air flow rate was investigated experimentally during Sept and Oct. 2020 under Egypt's Suez governorate's climate located at 29.9669°N, 32.5499°E. The system performance at various air flow rates, water basin height of the daily production was tested. A porous activated carbon tube (PACT) was utilized as a humidifier where the relative humidity reaches 100%, and the cooling system was used as a dehumidifier. The results revealed that increasing water height (Hw) enhances freshwater productivity. The highest distillate yield occurred at water height 3 cm, increasing 13.75% and 5.5% compared with water height 1 cm and 2 cm, respectively. The optimal hot air flowrate is 0.01156 kg/s with an increase of 100%, 38.46%, 15.9%, and 34.5% compared with 0.0057, 0.0086, 0.0144, and 0.0173 kg/s, respectively. The maximum freshwater production is 6.12 kg/day. The energy and exergy efficiencies and gain output ratio (GOR) are 26.73% and 1.57%, and 1.24, respectively. Economic analysis showed that the cost of 1 L of fresh water is 0.01386 USD.

Performance of a double-pipe heat exchanger with different met-al foam arrangements

This paper contributes to the field of improving the performance of heat exchangers using metal foam (MF) full-filled and partially/periodically-filled within the gap between the two pipes. The effect of configuration and arrangement of copper MF (15PPI and porosity of 0.95) installed on the outer surface of the inner pipe of a counter-flow double-pipe heat exchanger on the thermal and hydraulic performance was studied experimentally. The test section consisted of concentric two pipes; the inner pipe which was made of copper while the outer pipe was a Polyvinyl chlo-ride. Air was used as a working fluid in both hot and cold sides. A wide cold air flow rate range was covered from 3 to 36 m3/h which corresponds to Reynolds number (Re) range from 2811 to 31,335. The hot air flow rate was kept constant at 3m3/h. The temperature difference (ΔT) be-tween the inlet hot air and inlet cold air was adopted to be (20°C, 30°C, 40°C, and 50°C). The re-sults revealed that the higher Nusselt number (Nu) was at ΔT= 50°C and the thermal performance of the heat exchanger with the MF for all the arrangements was greater than the smooth heat exchanger. The highest and lowest friction factor was 1.033 and 0.0833 for the case 1 and 8, re-spectively, and the optimal performance evaluation criteria (PEC) was 1.62 for case 7 at Re = 2800. The Nu would be increased with a moderate increase in the friction factor by optimizing the arrangement of the MF. The two essential parameters that played an important role for in-creasing the PEC were the MF diameter and the MF arrangement along the axial length of the cold air stream.

Experimental and numerical investigation on evaporation characteristics of high salinity wastewater by rotary spray

Zero Liquid Discharge (ZLD) of high salinity wastewater is always an important subject in the field of energy and environment. In order to improve the evaporation rate, the mass and heat transfer characteristics of the rotary spray evaporation technology in the treatment of high salinity wastewater are explored. The relationship between the evaporation characteristics of wastewater and various parameters such as hot air flow rate, hot air temperature, feed flow rate, atomizing disk rotating speed and feed liquid concentration change is studied by experiment and simulation. It is concluded that the hot air temperature and hot air flow rate are important factors affecting the evaporation effect of the system. The atomizing disk rotating speed and the feed flow rate have a great influence on the atomization effect of the atomizer. A fluid recirculation area is generated around the atomizing disk, which allows droplets to reside longer in the evaporation chamber, thus improving the evaporation efficiency. Compared with other factors, the effect of feed liquid concentration on atomization and evaporation is relatively small. Finally, a better process operation condition is obtained through research: the atomizing disk rotating speed is 24,000 r/min, the feed flow rate is 4.5 kg/h, the hot air temperature is 498 K, and the hot air flow rate is 80 m3/h.

Analisis Unjuk Kerja Oven Pengering Hasil Modifikasi Dengan Variasi Kecepatan Aliran Udara Panas

Cost production efficiency through modified tunnel driyer by using the economizer so that the cost of fuel component eliminated. This study aimed to determine the performance of modified tunnel driyer associated with the quality of the product produced related to achived drying rate . From 3 (three) experiments conducted with variations in the hot air flow velocity of 0.5 m / sec, 0.7 m / sec, and 0.9 m / sec, it was found that only the first experiment occurred condensation and the resulting drying product was declared NG . From the results of the hypothesis independent sample t-test concluded the level of dryness of the results of the 3rd experimental product is better than the results of the 2nd experimental product. Thus, setting a hot air flow rate of 9 m / sec produces the most optimal modified dryer performance.

Heat transfer enhancement in rotary drum dryer by incorporating jet impingement to accelerate drying rate

The purpose of this study was to investigate experimentally the effects of impinging jets installed in a conventional rotary dryer for heat transfer enhancement. The metal drum had as insert a jet tunnel at the centerline, and the jets were arranged in an in-line configuration on the jet tunnel. A jet-to-jet (S) and a jet-to-target (H) distances were fixed at S/d = 6 and H/d = 4, respectively. Jet velocity (Vj ) was set at Vj = 5, 10 and 15 m/s, while jet temperature (Tj ) was 70, 80 or 90 °C. Drum rotation speed (N) was also investigated at N = 0.5, 1, and 3 rpm. The conventional rotary dryer was examined at the same mass flow rate of hot air to compare with the case having impinging jets. All experiments were conducted by batch drying 5 kg of fresh chilies for 8 hours. Results showed that installing jets gave more effective heat transfer, which accelerated water removal over that with the conventional rotary dryer, and the moisture contents were greatly reduced. On using impinging jets, the jet temperature had more influence on heat transfer enhancement than the jet velocity. In comparison, the effect of drum speed was small.

The drying rate of mushroom on tray dryer and effect of mushroom powder on organoleptic properties of Batagor

Oyster mushrooms and straw mushrooms are currently great demand in the food industry. Mushrooms have the characteristics that are easily damaged and decomposed. The effort of preserving mushrooms is by drying using hot air at a certain temperature and flow rate. The purpose of this study was to determine the drying rate of oyster mushrooms and straw mushroom in variations temperature and flow rate of hot air. In this study, the drying of mushrooms was carried out with a tray dryer that has a stacking rack with dimensions of 30 cm x 25 cm. The temperature variations used were 30, 40, 50ºC and the dryer air flow rate was 1, 2, 3 m/s. The dried mushroom with a moisture content of less than 10% is mashed to a powder then added to the food (Batagor) for an organoleptic test. The best drying result is obtained at temperature 50°C and flow rate of 3 m/s with a drying rate of 1.52 kg water/m2.h. Organoleptic test on Batagor produces the most preferred flavour by using type mushroom of Volvariella volvacea, and for aroma and texture preferably with Pleurotus ostreatus.

Pengaruh Perbedaan Ketebalan Irisan Asam Gelugur (Garcinia atroviridis) Terhadap Kandungan Total Asam Pada Asam Sitrat Dengan Pengeringan Sinar Matahari Sistim Konveksi Paksa

The mechanism of the drying process is the process of heat transfer and mass transfer that takes place simultaneously. The pressure of the water vapor in the acid gelugur is higher than that on the surface interface of the gums and air acids. Intensity solar radiation averages around 300-590w / m2 and Ambient Temperature 28,830C. The hot air condition in the drying box averages 320C. The content of total citric acid gelugur acid was 1.2787% with 3mm slice thickness and 1.3981% with a 5mm slice thickness. Drying is done from 08.00-17.00 am with a hot air flow rate of 1.5m/s.

Spray drying of hydroxyapatite powders: The effect of spray drying parameters and heat treatment on the particle size and morphology

The physical and chemical properties of spray dried hydroxyapatite (SD-HA) are significantly depended on precipitation and spray drying (SD) process parameters. This study presents the effects of precipitation pH, solid content, slurry feed rate, atomization pressure, hot air temperature and hot air flow rate on the particle size distribution of SD-HA. Moreover, the physical and chemical properties of SD-HAs and heat treated micro-granules depending on the precipitation pH were investigated. Taguchi Experimental Design (DoE) was employed to optimize the parameters and to determine the significant factors. The physical properties of SD-HA and heat treated micro-granules were analyzed via particle size analyzer, SEM and TEM. RAMAN and FTIR were carried out to examine the chemical properties. Increasing of the precipitation pH led to slightly increase of the median particle size and the high temperature stability of the SD-HA. DoE results demonstrated the most significant SD parameters as atomization pressure and slurry feed rate. The increases in heat treatment temperature decreased the specific surface area, pore volume and particle size of SD-HA, while increased the crystallinity and powder density. SD-HA were stable up to 1250 °C and decomposed at approximately 1450 °C.

Development of a desalination system driven by solar energy and low grade waste heat

Various thermal power systems emit flue gases containing significant amount of waste energy. The aim of this research is to recover a valuable amount of this energy to develop an efficient desalination system coupled with solar energy. Experiments were performed in the month of June 2014 at Al-Qassim, Saudi Arabia (26°4′53″N, 43°58′32″E) for different hot air (waste gas) flow rates and evaporator inlet water temperature to study the effect on daily potable water productivity. The proposed setup comprised an evaporator, condenser, air blower, electric heaters, storage tank and evacuated tube solar collectors. It was found that increasing the hot air flow rate increases the water productivity up to the critical flow rate after which the productivity decreases. Analytical model was developed for this desalination setup and the results were compared to that obtained from experiments. The overall daily (9AM–5PM) potable water productivity of the proposed system is about 50L for corresponding useful waste heat varying from 130 to 180MJ/day and a global solar radiation on a horizontal surface ranging from 15 to 29MJ/m2/day. Water is produced at the cost of 0.014USD/L and the fuel saving equal to 1844kg/h is achieved for the proposed desalination system.

Adsorption Behavior of Toluene on Modified 1X Molecular Sieves

In this paper, the toluene adsorption/desorption properties of modified 13X molecular sieves (M-13X) are discussed. M-13X molecular sieves were prepared by acidic and steam treatments of 13X molecular sieves. The structural parameters of M-13X were evaluated and compared with those of other molecular sieves (HY, HZSM-5, Cs7NaMOR, and a commercial 13X). The results show that the specific surface area, average pore diameter, and pore volume of M-13X were 414.17 m2/g, 2.98 nm, and 0.31 mL/g, respectively. The pore size distribution of M-13X was 1.8–3.0 nm. Because of its larger Si/Al ratio (Si/Al = 6.77), the hydrophobicity of M-13X is much higher than that of 13X (Si/Al = 1.28), indicating that it is particularly well suited to toluene control applications. The saturation adsorption capacity of M-13X was 0.045 g/g for simulated toluene at a temperature of 293 K and a relative humidity of 50%. The optimal regeneration temperature of M-13X was 473 K for 120 min with a hot air flow rate of 140 L/min. Implications: The modified 13X molecular sieves (M-13X) are adsorbents with a high adsorption capacity and great hydrophobicity, suitable for the treatment of VOCs. The purpose of the present investigation is to provide a practical guide for their design.

Experimental Comparison of Various Solid Desiccants for Regeneration by Evacuated Solar Air Collector and Air Dehumidification

In this article, the regeneration and adsorption of different desiccants such as silica gel, activated alumina, and activated charcoal for producing dry air is proposed. The air needed for regeneration was heated in an evacuated tube solar collector with a surface area of 4.44 m2. The desiccants were regenerated at temperatures in the range of 54.3–68.3°C. The regeneration performance was greatly affected by the regeneration temperature but depended on the initial moisture content, temperature of the desiccants, and flow rate of regeneration air. Comparison of the performances showed that at high hot air flow rate the regeneration time and adsorption time were shorter for these desiccants than that at low flow rate. Silica gel was observed to perform better at high as well as low flow rates for regeneration and adsorption than activated alumina and activated charcoal.

Hot Air Dryer with Closed – Loop Oscillating Heat Pipe with Check Valves for Reducing Energy in Drying Process

This research was studied to saving energy of hot air dryer with closed-loop oscillating heat pipe (CLOHP/CV). The CLOHP/CV made from a copper tube with inner diameter of 2mm. The evaporator and condenser lengths were 18cm. The adiabatic length was 20cm. Distilled water with 50% by total volume of tube was filled into CLOHP/CV. The number of meanderings was 40. The temperature for testing was 50, 60, 70, 80 and 90 oC. The hot air flow rate was 0.5, 1.0 and 1.5 m/s. The results of the normal hot air dryer and the hot air dryer with CLOHP/CV, it was found that the hot air dryer with CLOHP/CV can save thermal energy more than the normal hot air dryer. Moreover if determine in saving electrical energy, the hot air dryer with CLOHP/CV can save energy more than the normal hot air dryer by average of 28.13%.