Effect of ambient parameters change on mint leaves solar drying

Abstract This study investigates the effect of ambient conditions change on mint leaves solar drying performance and product water activity. Two drying methods, active indirect solar drying (AISD) and open sun drying (OSD) were compared while the experiments were carried out at specific dry climate conditions. During the experimental days, temperature varied from 20 to 30 °C, air relative humidity from 14 to 28.8 % and ambient pressure was around 82 kPa. The effect of air relative humidity change during the day on the rehydration of the product during the drying process was observed. After 7 h of drying, moisture content of mint leaves decreased from 85.29 % to 5.38 % in the AISD and 7.42 % in the OSD system. The 0.97 initial water activity decreased to 0.195 in AISD and 0.79 in OSD. Rehydration during the evening hours caused an increase in product water activity from 0.2 to 0.51. Changes of ambient conditions such as temperature and air relative humidity during the day can significantly affect water activity of dried product due to its rehydration and thus increase the risk of product spoilage.

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Thin-layer mathematical modeling of apple slices drying, using open sun and cabinet solar drying methods

International Journal of Innovative Research and Scientific Studies ◽

10.53894/ijirss.v4i2.55 ◽

2021 ◽

Vol 4 (2) ◽

pp. 43-52

Author(s):

Abdul Wasim Noori ◽

Mohammad Jafar Royen ◽

Juma Haydary

Keyword(s):

Thin Layer ◽

Mathematical Models ◽

Water Activity ◽

Model Fitting ◽

Coefficient Of Determination ◽

Drying Methods ◽

Solar Drying ◽

Drying Time ◽

Climate Conditions ◽

Thin Layer Drying

This paper aims to investigate the effect of climate conditions such as ambient temperature, humidity, pressure, sun radiation and pollution on sliced apples quality and drying time which are dried in an indirect forced cabinet solar drying (IFCSD) and open sun drying (OSD) systems. Both experiments were implemented at same place (Kabul, Afghanistan) and time. The IFCSD yield for saving time is 42.8 % which is more effective than drying in the OSD system. Simultaneously with the decreasing of sliced apple weight from 512.9 g down to 73.9 g, the water activity decreased from 0.955 down to 0.355 in the IFCSD system. For OSD system, the sample weight decreased from 512.6 g down to 78.4 g and its water activity from 0.955 down to 0.411. On the experiment day the average sun radiation was 571 w/m2 . The pressure drop between inlet and outlet of the dryer was 0.1 kPa. Different thin-layer mathematical models were investigated to identify the best model fitting the experimental data. The mathematical models’ performances were investigated by comparing the coefficient of determination (R 2 ), reduced chi-square (X2 ) and root mean square error (RMSE) coefficients. From all 11 applied thin-layer drying models the Page, Approximation diffusion, Verma et al and Midilli and Kacuk models are more fitted to our data.

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Effect of Drying Methods on the Physico-chemical Characteristics and Antioxidant Capacity of Taro, Sweetpotato, Stevia and Malunggay Leaves

Annals of Tropical Research ◽

10.32945/atr3928.2017 ◽

2017 ◽

pp. 88-99

Author(s):

Inish Chris Mesias ◽

Julie Tan ◽

Daniel Leslie Tan ◽

Benjamin L. Cinto

Keyword(s):

Antioxidant Capacity ◽

Bulk Density ◽

Water Activity ◽

Enzymatic Browning ◽

Chemical Characteristics ◽

Drying Methods ◽

Solar Drying ◽

Rehydration Ratio ◽

Sun Drying ◽

Physico Chemical

Fresh leaves are sensitive to high temperature so that appropriate drying method should be selected to dry leaves. This study aimed to determine the effect of drying methods on the physico-chemical characteristics and antioxidant capacity of taro (Colocasia esculenta), sweetpotato (Ipomea batatas), stevia (Stevia rebaudiana), and malunggay (Moringa oleifera) leaves. Fresh, healthy and mature leaves of taro, sweetpotato, stevia, and malunggay were subjected to solar drying, mechanical drying, and sun drying. The parameters evaluated in this study included moisture content, rehydration ratio, bulk density, water activity, total chlorophyll, antioxidant capacity, and non-enzymatic browning. Results showed that solar drying obtained the highest moisture removal capacity, rehydration ratio and water activity reduction while sun drying had the least. However, it was also with solar drying that the degree of non-enzymatic browning was the highest. Minimum bulk density was attained using solar and mechanical drying. In terms of chlorophyll content, mechanical drying had the highest. No apparent difference at p<0.05 between solar and sun drying methods was observed in terms of their effects on chlorophyll retention and antioxidant capacity. Variable effects of the different drying methods include little or no change, significant declines or enhancement of the leaves' physico-chemical and antioxidant attributes.

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Measurement of Bed Grain and Air Conditions during Solar Drying of Rice

International Journal of Food Engineering ◽

10.2202/1556-3758.2379 ◽

2011 ◽

Vol 7 (5) ◽

Author(s):

Pyseth Meas ◽

Anthony H. J. Paterson ◽

Donald J. Cleland ◽

John E. Bronlund ◽

A. John Mawson ◽

...

Keyword(s):

Wind Speed ◽

Relative Humidity ◽

Ambient Air ◽

Solar Drying ◽

Rice Varieties ◽

Drying Time ◽

Climate Conditions ◽

Solar Intensity ◽

Different Depths ◽

And Diffusion

Experiments on solar drying of rice were conducted in Cambodia in December 2004 using two local rice varieties and traditional methods practiced by farmers. For the whole drying time, the climate conditions—including the wind speed, ambient air temperature and relative humidity, as well as the solar intensity—were regularly monitored, along with the temperature, moisture content and relative humidity of the grain and air at different depths within the drying beds. Two drying treatments per day were extensively monitored. The monitoring showed that all of the processes of solar radiation, convection and evaporation at the surface, and conduction, convection, evaporation and diffusion within the bed are important.

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Design and Application of Variable Temperature Setup for Scanning Electron Microscopy in Gases and Liquids at Ambient Conditions

Microscopy and Microanalysis ◽

10.1017/s1431927615000732 ◽

2015 ◽

Vol 21 (3) ◽

pp. 765-770 ◽

Cited By ~ 6

Author(s):

Ahmed S. Al-Asadi ◽

Jie Zhang ◽

Jianbo Li ◽

Radislav A. Potyrailo ◽

Andrei Kolmakov

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Variable Temperature ◽

Ambient Pressure ◽

Thermoelectric Cooling ◽

Ambient Conditions ◽

Initial Water ◽

Different Temperatures ◽

Scanning Electron

AbstractScanning electron microscopy (SEM) of nanoscale objects in dry and fully hydrated conditions at different temperatures is of critical importance in revealing details of their interactions with an ambient environment. Currently available WETSEM capsules are equipped with thin electron-transparent membranes and allow imaging of samples at atmospheric pressure, but do not provide temperature control over the sample. Here, we developed and tested a thermoelectric cooling/heating setup for WETSEM capsules to allow ambient pressure in situ SEM studies with a temperature range between −15 and 100°C in gaseous, liquid, and frozen conditions. The design of the setup also allows for correlation of the SEM with optical microscopy and spectroscopy. As a demonstration of the possibilities of the developed approach, we performed real-time in situ microscopy studies of water condensation on a surface of Morpho sulkowskyi butterfly wing scales. We observed that initial water nucleation takes place on top of the scale ridges. These results confirmed earlier discovery of a preexisting polarity gradient of the ridges of Morpho butterflies. Our developed thermoelectric cooling/heating setup for environmental capsules meets the diverse needs for in situ nanocharacterization in material science, catalysis, microelectronics, chemistry, and biology.

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Solar Drying of Greenhouse Crop Residues for Energy Valorization: Modeling and Determination of Optimal Conditions

Agronomy ◽

10.3390/agronomy10122001 ◽

2020 ◽

Vol 10 (12) ◽

pp. 2001

Author(s):

Maria Guadalupe Pinna-Hernández ◽

Francisco Gabriel Acien Fernández ◽

José Gabriel López Segura ◽

José Luis Casas López

Keyword(s):

Relative Humidity ◽

Crop Residue ◽

Annual Variation ◽

Crop Residues ◽

Solar Drying ◽

Drying Process ◽

Ambient Conditions ◽

Characteristic Parameters ◽

First Order Kinetics

Large amounts of crop residue are produced annually in areas such as Almeria (Spain). These residues have elevated moisture and ash contents, and are also very heterogeneous, which hinders their reutilization. With the aim of facilitating biomass utilization in energy recovery-related processes, a model for solar drying was developed. Experiments were performed inside a greenhouse with tomato and pepper residues, following two strategies (hung or stacked residues). The influence of temperature and relative humidity on the residues’ equilibrium moisture was also studied. The results were that a model allowed for determination of the equilibrium moisture as a function of ambient conditions (temperature and relative humidity), with the model’s characteristic parameters being different for each crop residue. Regarding the drying process, the results conform to first-order kinetics, with the values of the kinetic constants varying as a function of the crop residues and their arrangement. The variation in equilibrium moisture as a function of the annual variation in ambient conditions (temperature and relative humidity) in Almería means that it would only be possible to dry crop residues inside greenhouse below a moisture level of 0.43 kgwater/kgdrysolids (30% water content) from April to November.

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Batch drying of sliced tomatoes at specific ambient conditions

Acta Chimica Slovaca ◽

10.2478/acs-2018-0019 ◽

2018 ◽

Vol 11 (2) ◽

pp. 134-140 ◽

Cited By ~ 1

Author(s):

Mohammad Jafar Royen ◽

Abdul Wasim Noori ◽

Juma Haydary

Keyword(s):

Relative Humidity ◽

Moisture Content ◽

Flow Rate ◽

Ambient Pressure ◽

Air Flow ◽

Force Sensor ◽

Effect Of Temperature ◽

Air Flow Rate ◽

Ambient Conditions ◽

Drying Time

Abstract In this work, drying of tomato slices was studied in a laboratory scale batch dryer working at conditions specific for geographical locations with low ambient pressure and low relative humidity of air. Tomato is a perishable farm product with high moisture content. Despite their high value, tomatoes are subjected to wastage and spoilage during their seasonal period; to last longer after harvested, they need to be treated by drying. Drying is one of the most widely used methods of tomato preserving for a longer period of time. This study involves experimental work on tomatoes drying in a tray laboratory batch dryer with the dimensions of (490 × 330 × 310) mm, a load cell-force sensor (range: 0–5 kg), fan (speed: 0–2500 rpm), air flow sensor (0–150 l/min) and a temperature and humidity monitoring system. This study was aimed at the development of a suitable drying method for the production of dehydrated agricultural products under specific air properties and climate conditions such as low ambient pressure and low relative humidity. During the experiment, the average ambient pressure was 82 kPa, and the average relative humidity of air was 20 %. Drying characteristics of tomato slices were determined at three temperature levels, namely: 50 °C, 60 °C and 70 °C,and three air flow rates: 30 l/s, 40 l/s and 50 l/s, for each temperature level. In this study, the effect of temperature, air flow rate, and ambient conditions on the drying rate of tomato slices were studied. The results indicate that during the experiments, tomatoes were dried to the final moisture content of 32.2 % from 92 %. Drying time at 50 °C, 60 °C and 70°C, and air flow of 30 l/s was 17.80 h, 15.80 h, and 14.08 h, respectively. For the air flow rate of 40 l/s, the drying time was 15.0 h, 12.9 h and 11.7 h and for the air flow rate of 50 l/s, the drying time of tomato slices was 14.0 h, 11.6 h and 10.2 h, respectively.

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DETERMINATION OF WET-BULB TEMPERATURE AND RELATIVE HUMIDITY OF REDUCED AMBIENT PRESSURE ENVIRONMENT: COMPUTER SIMULATION AND RAINBOW THERMOMETRY VALIDATION

10.1615/tfec2018.cmd.021664 ◽

2018 ◽

Author(s):

Parida Losangwal ◽

Pumyos Vallikul ◽

Songrit Tanchatchawan

Keyword(s):

Computer Simulation ◽

Relative Humidity ◽

Ambient Pressure

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Indoor Airflow Distribution in Repository Design: Experimental and Numerical Microclimate Analysis of an Archive

Buildings ◽

10.3390/buildings11040152 ◽

2021 ◽

Vol 11 (4) ◽

pp. 152

Author(s):

Karin Kompatscher ◽

Rick P. Kramer ◽

Bart Ankersmit ◽

Henk L. Schellen

Keyword(s):

Vertical Gradient ◽

Building Envelope ◽

Cfd Modeling ◽

Indoor Climate ◽

Ambient Conditions ◽

Climate Control ◽

Climate Conditions ◽

Airflow Distribution ◽

Air Mixing ◽

Delay Variations

The majority of cultural heritage is stored in archives, libraries and museum storage spaces. To reduce degradation risks, many archives adopt the use of archival boxes, among other means, to provide the necessary climate control and comply with strict legislation requirements regarding temperature and relative air humidity. A strict ambient indoor climate is assumed to provide adequate environmental conditions near objects. Guidelines and legislation provide requirements for ambient indoor climate parameters, but often do not consider other factors that influence the near-object environment, such as the use of archival boxes, airflow distribution and archival rack placement. This study aimed to provide more insight into the relation between the ambient indoor conditions in repositories and the hygrothermal conditions surrounding the collection. Comprehensive measurements were performed in a case study archive to collect ambient, local and near-object conditions. Both measurements and computational fluid dynamics (CFD) modeling were used to research temperature/relative humidity gradients and airflow distribution with a changing rack orientation, climate control strategy and supply as well as exhaust set-up in a repository. The following conclusions are presented: (i) supplying air from one air handling unit to multiple repositories on different floors leads to small temperature differences between them. Differences in ambient and local climates are noticed; (ii) archival boxes mute and delay variations in ambient conditions as expected—however, thermal radiation from the building envelope may have a large influence on the climate conditions in a box; (iii) adopting night reduction for energy conservation results in an increased influence of the external climate, with adequate insulation, this effect should be mitigated; and (iv) the specific locations of the supply air and extraction of air resulted in a vertical gradient of temperature and insufficient mixing of air, and adequate ventilation strategies should enhance sufficient air mixing in combination with the insulation of external walls, and gradient forming should be reduced.

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Enzymatic Synthesis of Isopropyl Acetate by Immobilized Bacillus cereus Lipase in Organic Medium

Enzyme Research ◽

10.4061/2011/919386 ◽

2011 ◽

Vol 2011 ◽

pp. 1-7 ◽

Cited By ~ 21

Author(s):

Madan Lal Verma ◽

Wamik Azmi ◽

Shamsher Singh Kanwar

Keyword(s):

Acetic Acid ◽

Bacillus Cereus ◽

Water Activity ◽

Molecular Sieves ◽

Immobilized Lipase ◽

Molar Ratio ◽

Ester Synthesis ◽

Initial Water ◽

Isopropyl Acetate ◽

Mg Addition

Selective production of fragrance fatty acid ester from isopropanol and acetic acid has been achieved using silica-immobilized lipase of Bacillus cereus MTCC 8372. A purified thermoalkalophilic extracellular lipase was immobilized by adsorption onto the silica. The effects of various parameters like molar ratio of substrates (isopropanol and acetic acid; 25 to 100 mM), concentration of biocatalyst (25–125 mg/mL), reaction time, reaction temperature, organic solvents, molecular sieves, and initial water activity were studied for optimal ester synthesis. Under optimized conditions, 66.0 mM of isopropyl acetate was produced when isopropanol and acetic acid were used at 100 mM: 75 mM in 9 h at 55°C in n-heptane under continuous shaking (160 rpm) using bound lipase (25 mg). Addition of molecular sieves (3 Å × 1.5 mm) resulted in a marked increase in ester synthesis (73.0 mM). Ester synthesis was enhanced by water activity associated with pre-equilibrated saturated salt solution of LiCl. The immobilized lipase retained more than 50% of its activity after the 6th cycle of reuse.

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