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Refractance window drying (RWD) has been identified as the method that can give high-quality products at a relatively low production cost. However, knowledge about its use and adoption remains lacking both in academic curricula and industry in the developing world.

A lab-scale batch RWD of a closed-loop control system was designed, fabricated and evaluated for drying rates, evaporation rate, the energy of evaporation, energy efficiency and throughput. Testing was done using mango and tomato pulps.

Drying rates at 95°C of 1.32 gg⁻¹min⁻¹ and 0.854 gg⁻¹min⁻¹ at 2 and 3 mm, respectively, for tomato, 0.6 gg⁻¹min⁻¹ and 0.33 gg⁻¹min⁻¹ at 2 and 3 mm for mango pulp were obtained. The dryer had an evaporation rate of 4.63 × 10^–4 kg/s and 4.25 × 10^–4 kg/s, the energy of evaporation of 1.05 kW and 0.96 kW and thermal energy efficiency of 25.64% and 21.73% while drying tomato and mango pulps, respectively. Dryer throughput of 0.6 kg/h of dried mango Pulp and 0.47 kg/h of dried tomato pulp was obtained.

The designed RWD can be adequately used in laboratory experiments on different products to produce powders. This will enable the transfer of knowledge about RWD technology in developing countries.

The purpose of this paper is to present and discuss the external factors of the solar dryer design that influenced the thermal efficiency of the solar dryer that contribute to the better quality of dried food products.

From the reviewed works of literature, the external factors including the drying temperature, airflow rate and relative humidity have significant effects to increase the rate of moisture diffusivity of the freshly harvested products during the drying process. The proper controls of airflow rate (Q), velocity (V), relative humidity (RH%) and drying temperature (°C) can influence the dried product quality. The dehydration ratio is the procedure to measure the quality of the dried food product.

The indirect solar dryer including the mixed-mode, hybrid and integrated was found shorter in drying time and energy-intensive compared to sun drying and direct drying. The recommended drying temperature is from 35.5°C to 70°C with 1–2 m/s velocity and 20%–60% relative humidity. The optimum thermal efficiency can be reached by additional devices, including solar collectors and solar accumulators. It gives a simultaneous effect and elongated the drying temperature 8%–10% higher than ambient temperature with 34%–40% energy saving. The recommended airflow rate for drying is 0.1204 to 0.0894 kg/s. Meanwhile, an airflow rate at 0.035–0.04 kg/m2 is recommended for an optimum drying kinetic performance.

This paper discusses the influence of the external factors of the solar dryer design on the thermal performance of the solar dryer and final dried food products quality. Therefore, the findings cannot serve as a statistical generalization but should instead be viewed as the quantitative validation subjected to fundamentals of the solar dryer design process and qualitative observation of the dried food product quality.

A well-designed of solar dryer with low operating and initial fabrication cost, which is simple to operate is useful for the farmers to preserve surplus harvested crops to an acceptable and marketable foods product. The optimization of the external and internal factors can contribute to solar dryer thermal performance that later provides an organoleptic drying condition that results in good quality of dried product and better drying process. The recommended drying temperature for a drying method is between 35°C up to 70°C. Drying at 65.56°C was effective to kill microorganisms. Meanwhile, drying at 50°C consider as average drying temperature. The recommended airflow rate for drying is 0.1204 to 0.0894 kg/s. Meanwhile, air flowrate at 0.035–0.04 kg/m² is recommended for optimum drying kinetic performance. The recommended value of aspect ratio and mass flow rate is 200 to 300 for an optimum evaporation rate. The good quality of dried products and good performance of solar dryers can be developed by proper control of airflow rate (Q), velocity (V), relative humidity (RH%) and drying temperature (°C).

The proper control of the drying temperature, relative humidity and airflow rate during the drying process will influence the final dried food products in terms of shape, color, aroma, texture, rupture and nutritious value. It is crucial to control the drying parameters because over-drying caused an increment of energy cost and reduces the dry matter. The quick-drying will disturb the chemical process during fermentation to be completed.

This study identifies the potential of the solar drying method for dehydrating agricultural produces for later use with the organoleptic drying process. The organoleptic drying process can reduce mold growth by promising an effective diffusion of moisture from freshly harvested products. The research paper gives useful understandings that well-designed solar drying technology gives a significant effect on dried product quality.

A numerical study is carried out to investigate the influence of multistage drying regimes on the drying kinematics of a porous material. In particular the effects of varying the conditions of the drying medium are studied. The drying model for the solid is developed based on the continuum approach. A series of simulations of the drying behaviour of a rectangular brick with varying temperature, heat transfer coefficient and relative humidity of the drying medium are undertaken. It is found that the total drying time is mainly dependent on the relative humidity of the drying medium. Also condensation is predicted on the surface of the brick, with the quantity of condensation being directly linked to the relative humidity and temperature of the drying medium. Overall it is concluded that multistage drying regimes are useful in reducing the overall drying time whilst avoiding detrimental shrinkage during the constant drying period.

The aim of this work was to study the effect of the different temperatures on drying kinetics and quality parameters of vacuum oven-dried mediterranean or black mussel (Mytilus galloprovincialis) specimens.

Drying process was performed at 50, 60 and 70 °C and a vacuum drying pressure of 0.1 kPa. The proximate composition analysis was done. Drying rates of the mussels were computed. Mathematical modeling was carried out. Effective moisture diffusivity, activation energy and total energy consumption were calculated. Color measurement was conducted.

Drying took place entirely in the falling rate period. The obtained results indicated that the drying air temperature has a remarkable influence on the moisture content and drying rate. Drying resulted in a significant increasing of protein and fat content. The D_eff values ranged from 1.44 × 10⁻⁹–3.23 × 10⁻⁹ m²/s, with the activation energy 4.47 kW kg⁻¹. The Alibas model is the most proper model to define the drying curves. This method provided high energy efficiency and quality in dried products.

Fresh mussels grown in Eceabat location were used as the study sample. In the drying process, 50, 60, 70 °C temperatures and 0.1 kPa pressure was used. These are the limitations of the research.

This work is the first to report the influence of vacuum oven drying on the color changes and drying kinetics of black mussels.

In this paper, a single module of cross-flow membrane humidifier is evaluated as a three-dimensional multiphase model. The purpose of this paper is to analyze the effect of volume flow rate, dry temperature, dew point wet temperature and porosity of gas diffusion layer on the humidifier performance.

In this study, one set of coupled equations are continuity, momentum, species and energy conservation is considered. The numerical code is benchmarked by the comparison of numerical results with experimental data of Hwang et al.

The results reveal that the transfer rate of water vapor and dew point approach temperature (DPAT) increase by increasing the volume flow rate. Also, it is found that the water recovery ratio (WRR) and relative humidity (RH) decrease with increasing volume flow rate. In addition, all mixed results decrease with increasing dry side temperature especially at high volume flow rates and this trend in high volume flow rates is more sensible. Although the transfer rate of water vapor and DPAT increases with increasing the wet inlet temperature, WRR and RH reduce. Increasing dew point temperature effect is more sensible at the wet side is compared with the dry side. The humidification performance will be enhanced with increasing diffusion layer porosity by increasing the wet inlet dew point temperature, but has no meaningful effect on other operating parameters. The pressure drop along humidifier gas channels increases with rising flow rate, consequently, the required power of membrane humidifier will enhance.

According to previous studies, the three-dimensional numerical multiphase model of cross-flow membrane humidifier has not been developed.

This work aims to study the hydrothermal behavior of mortar cement toward certain environmental factors (ambient air temperature and air velocity) based on its drying kinetics data. The objective is to provide a better understanding and controlling the stability of mortar structures, which integrate the sorption phenomenon, drying process, air pressure and intrinsic characteristics. This leads to predict the comportment of mortar structures in relation with main environmental factors and minimize the risk of cracking mortar structures at an early age.

Thermokinetic study was carried out in natural and forced convection solar drying at three temperatures 20, 30 and 40°C and three air velocities (1, 3 and 5 m.s-¹). The empirical and semiempirical models tested successfully describe the drying kinetics of mortar. These models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures.

The models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures. The average activation energy obtained expressed the temperature effect on the mortar diffusivity. The drying constant and the diffusion coefficient can be used to predict the influence of these environmental factors on the drying behavior of various building materials and therefore on their durability.

Evaluation of the effect of several environmental factors and intrinsic characteristics of mortar structures on their durability.

The paper aims to evaluate drying performance of earth mortar by solar drying for more durability, minimize pathologies in traditional construction and determine the influence of temperature and humidity on the microstructure of earth mortar using static gravimetric method.

A convective solar dryer was used for the pretreatment of building and solid materials for construction.

The humidity influences the mortar sorption – surface water sorption of earth mortar increased with increasing temperature.

The study used a novel method for pretreatment building materials by using solar dryer.

This study aims to investigate the effect of spray drying temperature and maltodextrin addition on the contents of phenolics, flavonoids, anthocyanins and antioxidant activities (2,2-diphenyl-1-picrylhydrazyl [DPPH] radical scavenging activity, ferric reducing antioxidant power and reducing power) of karonda powder.

Over the past few decades, the demands for application of natural colorants in food production have been attracting the attention of academic research and food industry. Anthocyanins, a red pigment commonly found on plants, show high potentials in the preparation of spray-dried pigment powder. This study, therefore, was conducted using full factorial design with two factors, namely, inlet temperature (150°C and 160°C) and soluble solid concentration (10, 15 and 20°Brix) with maltodextrin as carrier to produce pigment powder from karonda, an anthocyanin-rich fruit which is native to southeast Asia.

Increasing soluble solid content from 10 to 15°Brix resulted in a 42%–57% reduction in phenolic, flavonoid and anthocyanin contents. However, when increasing the amount of maltodextrin from 15 to 20°Brix, a lower reduction (approximately 11%–19%) was observed. In samples with the same °Brix, there was no significant variation in antioxidant contents and activities, especially at high maltodextrin ratios. In addition, the reducing power of samples dried at higher temperature (160°C) was higher than that of samples dried at lower temperature. Karonda spray-dried powder showed a good positive correlation (p < 0.01) between antioxidant contents and DPPH• activity.

To the best of the authors’ knowledge, in this study, for the first time, the effect of spray drying conditions on the quality of karonda powder was investigated.

Paint drying is a very important process in an industry where shorter drying time for productivity and lower energy consumption for production cost are required while maintaining the product’s painting quality. In the present study, a drying process in a line-type paint drying furnace equipped with nozzles for hot air supply and moving conveyer belt to dry painted automotive parts is numerically simulated for the flow and heat transfer inside the furnace to evaluate the quality of the drying or baking at the end of the drying process in a production line.

A baking window for a specific paint is used for judging the local degree of baking (DOB) of the painted parts, which can be useful to identify under-baked or over-baked locations of the painted parts, and hence the quality of the baking process.

Numerical results of a time history of temperatures at two monitoring points on the painted parts were obtained and compared to the measured data in an actual furnace and showed good agreement. Three types of paints were considered in the present study and numerical results showed different drying characteristics. In addition to the original furnace nozzle configuration, two more furnace nozzle configurations with different numbers, direction and speed of hot air supply were simulated to improve the furnace’s drying performance. As a result, a newly suggested nozzle configuration with quick drying paint can give us a remarkable improvement in surface averaged DOB compared to the original nozzle configuration with original paint.

The present simulation technique and DOB methodology can be used for the optimal design of a drying furnace.

This study aims to present a basic mathematical model for investigating the structure of counter-flow non-premixed laminar flames propagating through uniformly-distributed organic fuel particles considering preheat, drying, vaporization, reaction and oxidizer zones.

Lycopodium particles and air are taken as biofuel and oxidizer, respectively. Dimensionalized and non-dimensionalized forms of mass and energy conservation equations are derived for each zone taking into account proper boundary and jump conditions. Subsequently, to solve the governing equations, an asymptotic method is used. For validation purpose, results achieved from the present analysis are compared with reliable data reported in the literature under certain conditions.

With regard to the comparisons, although different complex non-homogeneous differential equations are solved in this paper, acceptable agreements are observed. Finally, the impacts of significant parameters including fuel and oxidizer Lewis numbers, equivalence ratio, mass particle concentration, fuel and oxidizer mass fractions and lycopodium initial temperature on the flame temperature, flame front position and flow strain rate are elaborately explained.

An asymptotic method for mathematical modeling of counter-flow non-premixed multi-zone laminar flames propagating through lycopodium particles.