Mathematical models to describe the drying process of Moringa oleifera leaves in a convective-air dryer

Drying kinetics of Malaysian Moringa oleifera leaves was investigated using a convective-air dryer. The drying parameters were: temperature (40, 50, 60, 70 °C), air velocity (1.3 m s^–1, 1.7 m s^–1). The drying process took place in the falling rate period and there was an absence of a constant rate period in this experiment. Six mathematical models (Lewis, Henderson and Pabis, Wang and Singh, Peleg, Page, and logarithmic) were selected for the description of drying characteristics of the leaves. The Wang and Singh model was determined as the best model based on the highest overall coefficient determinant (R²) and the lowest overall root mean square error (RMSE). The effective diffusivity (D_eff) was also calculated which was in the range of 3.98 × 10^–11 m² s^–1 to 1.74 × 10^–10 m² s^–1.An Arrhenius relation was constructed to determine the activation energy for the samples in the convective air dryer. The activation energy for M. oleifera leaves was 39.82 kJ mol^–1 and 33.13 kJ mol^–1 at drying velocities of 1.3 m s^–1 and 1.7 m s^–1, respectively.

Energy Performance Analysis of Convective Drying of Sorghum Gruel Residue

This research is concerned with the energy performance analysis of convective drying of sorghum gruel residue. The process was carried out on a hot air dryer conducted at four drying air temperatures of 40, 50, 60, and 70 °C respectively, three different air velocities 0.8, 1.0 and 1.2m/s and three different varieties of sorghum gruel residue, Caudatum,Durra and Guineense respectively. The effects of drying temperature and air velocities on the specific energy consumption, energy efficiency, drying efficiency and thermal efficiency were investigated. The specific energy consumption for Caudatum,Durra, Guineensevarieties ranges from 169530.001 J/kg - 71433.758 J/kg, 170557.25 J/kg - 76732.96 J/kg and 179367.266 J/kg - 83750.923 J/kg respectively while the energy efficiency for Caudatum,Durra, Guineensevarieties ranges from 35.5% - 13.934%, 31.188% - 13.836% and 28.463% - 13.157% respectively. The results of this study also confirmed that the convective drying process is energy intensive and drying fresh agricultural produce with heated-air dryers requires a relatively large amount of energy.

Cutting Oxygen Production-Related Greenhouse Gas Emissions by Improved Compression Heat Management in a Cryogenic Air Separation Unit

Oxygen production in cryogenic air separation units is related to a significant carbon footprint and its supply in the medicinal sphere became critical during the recent COVID-19 crisis. An improved unit design was proposed, utilizing a part of waste heat produced during air pre-cooling and intercooling via absorption coolers, to reduce power consumption. Variable ambient air humidity impact on compressed air dryers’ regeneration was also considered. A steady-state process simulation of a model 500 t h−1 inlet cryogenic air separation unit was performed in Aspen Plus® V11. Comparison of a model without and with absorption coolers yielded an achievable reduction in power consumption for air compression and air dryer regeneration by 6 to 9% (23 to 33 GWh year−1) and a favorable simple payback period of 4 to 10 years, both depending on air pressure loss in additional heat exchangers to be installed. The resulting specific oxygen production decrease amounted to EUR 2–4.2 t−1. Emissions of major gaseous pollutants from power production were both calculated by an in-house developed thermal power plant model and adopted from literature. A power consumption cut was translated into the following annual greenhouse gas emission reduction: CO2 16 to 30 kilotons, CO 0.3 to 2.3 tons, SOx 4.7 to 187 tons and NOx 11 to 56 tons, depending on applied fossil fuel-based emission factors. Considering a more renewable energy sources-containing energy mix, annual greenhouse gas emissions decreased by 50 to over 80%, varying for individual pollutants.

Evaluation of Changes and Characteristics of Hair According to the Application of the Hair Dryer Plasma Functional Module

Hairdryers are commonly known to cause hair damage such as “roughness”, “dryness”, and “hair color loss”. while using it. So, numerous studies have tried to find ways to dry hair with no damage or minimized level. In this study, we examined hair damage levels by varying drying applications during the process and analyzed hair changes either in essential characteristics such as “oil and moisture balance” or “microstructure”. As a result, hair was severely damaged when treated with a general hot air dryer for 90 minutes, causing cuticle crack or layer separation. In contrast, the plasma hairdryer caused just a little or even no damage to hair for the same exposure time. It may be because ions and moisture molecules generated when using a plasma hairdryer can protect hair structure from the harsh hot air condition.

Optimization of the process of banana flour preparation

Banana (Musa paradisiaca) is a cheap source of carbohydrates and micronutrients. Converting banana into flour can help to obtain a consistent ingredient for bakery foods while preventing the post-production losses of this bulky and perishable food source. Hence a study has been undertaken to standardize the drying protocol for banana flour preparation. The effects of the different temperature-treatment combination on drying of banana were studied. Experiments were done at 50°C, 60°C and 70°C (without any treatment, with citric acid dipping and with combined citric acid and blanching process) and the variation in the quality of the dehydrated material was studied. The results showed that drying at 70°C followed by 0.5% citric acid treatment for 10 min, in 24h, in non-circulating natural convection air dryer was the optimal protocol concerning better quality parameters like water activity, total soluble solids, ascorbic acid, microbial contamination and the time taken to complete the drying process.