Design Of Solar Dryer Research Articles

Optimizing solar dryer design: A multicriteria decision making approach for hybrid systems

Solar dryers are a sustainable and efficient alternative for preserving agricultural products, offering numerous benefits for both the environment and the agro-industrial sector's economy. The objective is to develop a decisionmaking methodology based on environmental, economic, and social criteria, allowing the acquisition of data for the design of solar dryers using alternative energy sources to achieve the hybridization of one or more energy sources. The Analytic Hierarchy Process (AHP) methodology is based on breaking down a complex problem into a series of simple and manageable problems. This methodology evaluated alternatives based on different criteria and factors to consider. The AHP methodology was divided into three stages: the first was to define the problem to be solved, the second was to determine the criteria, and the third was to analyze the possible alternatives. This research provided information for the design of a solar coffee dryer in San Antonio el Porvenir, Chiapas. The solar dryer's design was based on criteria proposed by the producers, such as ease of repair, the product not being in contact with the ground, and ensuring safe operation due to the presence of children and women near the drying process.

Innovative Solar Air Dryer Designs for Agricultural Products-A Review

Indeed, agricultural technological development plays a crucial role in the agricultural commercialization and socio-economic transformation of India. Enhancing farming through solar dryers has been considered to be a key strategy for enhancing food security and greater socioeconomic change. Drying removes the majority of the product’s moisture content; it is a crucial post-harvest technique for agricultural goods that may increase quality, decrease losses during storage, and save transportation costs. The literature study provides evidence that solar dryers that use phase change material and operate in indirect or mixed modes are more effective than direct drying solar dryers in drying agricultural goods. This review study’s main objective is to give an overview of the recent developments in solar dryer technology achieved by different researchers. Innovative solar dryer designs for drying agricultural products are reviewed in this present work. A thorough analysis of the design, operation, uses, and comparison of solar dryers is conducted. The solar dryers design their modifications and different techniques to improve thermal performance are studied thoroughly. Hybrid solar dryer with CPC, ETC, photovoltaic technology can work as an independent unit and proves the better thermal performance dryer unit as compared to conventional dryers. The new improvements to hybrid dryers are also discussed in detail. Present study will be helpful for developing an economical dryer with variety of drying parameters and different agricultural products.

Assessing the Performance of a Blackbody Solar Dryer

About 33.3% of global food production is lost to spoilage every year. At current rates, that amount is adequate for feeding an average of 300 million people around the world. This huge loss can be decimated to 13.17% if food spoilage is avoided or managed better. One technique for minimizing food waste is solar drying. West Africa and locations around the equatorial plane are described by average daily insolation of about 4-6 kWhm−2. In effect, this energy source could be applied to curb the problem of food spoilage and wastage. Another side attraction of drying with solar is that, it offers year-round availability of food crops. In this study, solar drying is investigated with the principle of blackbody radiation using an electronic data logger coupled with the Arduino Uno, SD Card Module, DHT22 Temperature and Humidity Sensor, SD Card, and Connecting wires to record temperature and humidity data. The output was 56.3°C and 46.8°C for the upper and lower limit of temperature respectively, yielding an average difference of about 10°C. The interaction of sensible blackbody radiation within a four-tier rock bed was crafted into a novel solar dryer design. With this relatively high-temperature gradient between the upper and lower, a blackbody solar dryer constructed was suitable to preserve the both quality and shelf life of agricultural produce.

Experimental investigation and energy-exergy-environmental-economic analysis of modified indirect solar dual collector dryer while drying myrobalan slices.

The paper presents the performance evaluation of a modified indirect solar dual collector dryer (MIS2CD) integrated with a thermal storage system for drying myrobalan slices. The design of the solar collector and solar collector with thermal storage was to supply uninterrupted thermal energy to the drying chamber during sunny and sunset hours. To evaluate the dryer performances, one lot (20kg) of myrobalan was dried in the MIS2CD, and as a result, the thermal efficiency and energy supply period of MIS2CD increased by 12 ± 02% and 41 ± 1.2%, respectively. Drying characteristics of myrobalan slices in MIS2CD, TD, and OSD were studied and compared. A two-term exponential model best explains the drying kinetics of myrobalan slices dried in MIS2CD. The dried sample in MIS2CD results in lesser ΔE* values than TD and OSD methods. The highest exergy efficiency of 78.2% and lower exergy losses were recorded. The energy payback period of the MIS2CD was evaluated as 1.42years. The CO2 emitted and CO2 reduced reduction are calculated for drying myrobalan in MIS2CD for a lifetime (20years) of 67.85kg and 20.65 tons, respectively. The capital cost of the solar dryer design was estimated depending on the economic considerations of the state. The drying hours were increased in MIS2CD against OSD by 59% on the annual sunny days (210days). The sample drying period MSD and TD to reach the final moisture level of 7% was 9h and 5h, respectively. The total economic benefit is 22,622 INR (annually), and the 2.08 benefit-cost ratio for myrobalan dried in MIS2CD compared to TD. The MIS2CD's payback period is nearly 2.18years, much less than the dryer's lifetime.

Developmental Trend of Hybrid Solar Dryer: A Comprehensive Review

The objective of this paper is to present a review on hybrid solar dryer and its modification for further research. Energy is not evenly distributed in the world, developed countries have more than enough while developing countries are facing it inadequacy. Rural areas where agricultural activities are taking place largely have no access to power supply to power drying equipment. Large amount of farm produce of about 30% were damaged due to lack of drying facilities. This has been resolved with the application of evolution of solar dryer and to a better level, use of hybrid solar dryer of exponential value over open air sun drying. It was found that the drying efficiency of hybrid solar dryer was 35%, while the maximum drying temperature was 80oC. Retention time in drying chamber was found to be between 2 – 3 days, it indicate the sustainability of hybrid solar dryer for drying high moisture farm produce. Various design of solar dryer and hybrid solar dryer were reported in the literature thus for is presented. Hybrid solar dryer could be developed further with the inclusion of dehumidifier as a system aiding drying.

Solar Hybrid Drying System for Marine Applications – A Comprehensive Review

ABSTRACT At present, the fisheries sector’s contribution to the world as a source of nutrients and wealth is highly significant. Fisherfolks harvest marine products like fish, prawns, and squid in a surplus amount; however, due to the non-availability of cold chain facilities, a lot of items are spoiled. Hence, drying is practiced in most parts of the world to preserve marine products. Studies have reported use of various designs of the solar hybrid dryer for drying of marine products. However, there is no comprehensive report on different designs of solar dryers and their application, especially in the drying of marine products. Hence, this review focused on solar drying, various designs of solar-based dryers, and the application of solar hybrid drying systems for marine products including the quality analysis of the final product.

Environmental sustainability and exergy return on investment of selected solar dryer designs based on standard and extended exergy approaches

ABSTRACT Different solar dryer designs are available in the literature. However, it is essential to understand how the performance of the dryer designs contributes to environmental sustainability by reducing waste in the exergy-loop and mitigate CO2 emission into the atmosphere. The exergy-based sustainability indices include waste exergy ratio, lack of productivity (LOP), sustainability index, environmental destruction coefficient and exergy recovery ratio. The paper also introduces exergy return on investment (ExRoI) by applying an extended exergy accounting approach with the inclusion of exergy influx of material resources, capital and labor in the exegetic computations of the sustainability index. Four solar dryers consisting of an indirect solar-cabinet dryer, mix-mode solar dryer, hybrid solar dryer and a double-partitioned single-pass-collector solar dryer with a wind generator were used as a case study. Comparatively, the ExRoI is lower than the standard exergy-efficiency for the four dryers by 6.87 to 91.61%. In contrast, the standard exergy-based sustainability index was higher by 5.4 to 61.2%. Total invested exergy ranged from 0.04TJ to 0.081TJ. The values of waste exergy ratio, LOP, ERR, EDC, and carbon credit ranged from 0.47 to 0.79, 0.566 to 16.45, 5.44 × 10−4 to 1.37 × 10−1, 1.57 to 17.45 and 231.45 to $2908, respectively.

A review study on recent advances in solar drying: Mechanisms, challenges and perspectives

Drying is important in many processes for material preservation, operation optimisation, and easy handling. Various dryers have been developed to ensure controllable drying performance and enhance efficiency. Since traditional mechanical dryers depend heavily upon fossil fuels, ongoing studies have been conducted on solar dryers, focusing on offering alternative sustainable drying methods and utilising local materials in a more sustainable manner. This review features recent work and development on solar dryers from the material and technical perspectives, emphasising the component conceptions and ameliorations, material utilisations, and drying fluid thermodynamics. The overall drying performances, advantages, and current drawbacks of different solar dryer designs are critically discussed. Applications of various solar dryers in different sectors are also described.

Recent Developments in Design and Operations of Solar dryer.

Solar drying is useful in several residential, commercial and industrial applications. Proper dryer design, operation and maintenance are essential for enhancing the dryer performance and better quality of the dried product. Solar dryer is beneficial as it protects the product from adverse climatic conditions and quickly economically dry the product. The dryer design has undergone significant shapes, dimensions, and storage features leading to better reliability. Researchers worldwide have reported higher energetic and exergetic performance through advanced design, measurement, and control features. Conventional dryer’s efficiency deterioration is attributed to the lack of proper material selection and computational fluid flow techniques. Traditional dryer designs have focused on product drying rate while advanced sustainable solar dryer designs increased solar thermal utilization in a limited area with locally available materials based on fluid flow conditions suitable to the microclimatic conditions. Analysis using computational fluid dynamics (CFD) software has assisted in refining dryer designs to be compact with the complex flow and quick product drying features. The present paper tracks developments in solar dryer designs for different dryer classifications. Recommendations for energy-efficient design and measures for improvement in existing dryers are also discussed.

Assessment of eco‐thermal sustainability potential of a cluster of low‐cost solar dryer designs based on exergetic sustainability indicators and earned carbon credit

This research aims to establish the interconnectivity between solar dryer designs and the exegetic-sustainability performance of solar dryers. This is to assist energy policymakers and fabricators to establish design standards and make the right choice for waste exergy management strategy for environmental sustainability. Therefore, in this study, the exergy-based sustainability indicators and earned carbon credit were used to assess and compare the performance of four different designs of solar dryers of equal collector capacity under the same external environmental conditions in the same town. In terms of better sustainability indicators that include high exergy efficiency, lower waste exergy emission, higher sustainability index and lower lack of productivity, solar dryer designs with single-pass triple air movement direction with inlet air powered by wind generator had the best indices for environmental sustainability. In contrast, the natural convection mix-mode solar dryer design had the lowest environmental effect factor and destruction coefficient while the indirect natural convection solar dryer had the highest energy recovery ratio based on exergy output from water evaporation. However, the mix-mode solar dryer powered by the wind generator earned the highest carbon credit. The exergy efficiency ranged from 19.09 to 52 % for the four cases, whereas the waste exergy ratio ranged from 0.52 to 0.81. The LOP value ranged from 2.95 to 19.96. Similarly, the sustainability index ranged from 1.28 to 2.5, the average environmental destruction coefficient varied from 3.96 to 20.96, the exergy recovery ratio for the four dryers varied from 0.001825 to 0.12405, and the earned carbon credit ranged from $442. 3 to $2630.5.

Research outcome of sustainable solar drying technology dissemination for preserving perishable agriculture and horticulture crops in the North Western Himalayan region of India

Solar drying in a controlled environment offers one of the best options to preserve perishable crops. The objective of the present study is to work toward achieving UN sustainable Goal targets by 2030 through sustainable solar dryer designs and crop drying techniques based on years of experimentation and field implementation. In this study, low-cost free of maintenance innovative solar dryer designs, and research results of solar drying of commercial agricultural and horticultural crops grown in the North-Eastern Himalayan region of India, are presented. The farmer feedback survey results of field-installed solar dryers in different climatic zones of the region varying from low hills to high altitude snowbound regions are critically analysed. The quality parameters of the solar dried products namely color, reducing sugar, total sugar, and ascorbic acidity, are found to be commercially acceptable thus enhancing the market potential of the solar dried products. The newly developed low-cost indirect solar dryers with automation can easily be propagated worldwide. The market value of some solar-dried fruit products is found to enhance from 29% to 200% due to better quality, appearance, and taste, thus providing better returns to farmers and moving towards sustainable agriculture development.

Design and fabrication of a double- chamber solar dryer

Object of research: This paper discusses the design and construction of a modified, cost effective solar dryer for use by the average Nigerian farmer or agri-business entrepreneur.
 Investigated problem: Local farmers often have a lot of difficulties in properly drying harvested agricultural produce for storage and processing purposes, safely and efficiently due to capital constraints. There was therefore a need for an efficient, low cost solar dryer design to aid in this pursuit.
 Methodology: The designed dryer is a passive dryer that makes use of heat energy tapped through glass collectors placed over the drying and air inlet chambers respectively. The dryer was designed and constructed with carefully selected, inexpensive materials with dimensions of 40cm x 40cm x 60cm for the drying chamber and dimensions of 10cm x 80cm x 40cm for the heating chamber. The glass collectors (4mm thick) were inclined at an angle of incidence of 17.26°. Okra slices were used to test the performance of the dryer.
 Results / Area of practical use: The study yielded a low cost (€145.60) modified solar dryer capable of drying agricultural produce in a safe and clean way. During eight (8) hours of drying under a temperature range of 39 °C – 45 °C, the initial weight of the okra slices reduced from 150g to 9g, 9g, 10g and 9g on each of the four trays of the drying chamber respectively. Local farmers and agripreneurs will be encouraged to make use of this clean alternative of drying food produce without the drawbacks from regular sun drying.
 Conclusion: There is need for more work to be done in terms of installation of solar panels to enhance dryer performance. More work should also be carried out on tests during the dry season for increased dryer efficiency.

SIMULATION OF THE GRAIN DRYING PROCESS IN BUNKER DRYERS USING HELIOCOLLECTORS

Drying is the main method of preparing agricultural materials for storage. Today, there are a variety of drying plants in the world that use solar radiation energy to heat a drying agent or drying material. But most designs of solar dryers are adapted to work in stationary conditions, special rooms. Reducing energy consumption for drying grain materials is an urgent problem, which is solved in two main ways - technical modernization of existing drying equipment and development of new energy-saving methods and modes of drying agricultural materials and their implementation on existing and upgraded facilities. Both the first and second way of solving the problem of energy saving is based on a mathematical description of the processes of heat and mass transfer.The mathematical model of thermal modes of the drying unit is a set of interconnected models of its individual elements with external kinematic parameters (atmospheric air temperature, intensity of solar radiation, etc.). The model of a single element of the system is a system of differential equations in differential form, limit and initial conditions, which reflect the basic physical dependences of the studied processes.The aim of the research was to formulate a mathematical model based on the theory of heat and mass transfer to determine the dynamics of the development of interconnected nonstationary fields of temperature and moisture content of the material and the drying agent - air.Numerical implementation of the proposed mathematical models in a standard mathematical package allows to analyze the performance of equipment, in particular film solar collectors, for convective drying of dispersed agricultural materials in the layer depending on the parameters of the feed material, solar radiation intensity or (and) heat generator capacity atmospheric air.

Comparison of Warming Efficiency of Greenhouse Solar Dryer with Four Distinct Design Implementations

Drying is a technique for transferring warmth from a source to a product while also removing moisture from the product in a limited space. When using sun drying, the heat required for drying is primarily provided by solar energy. In this paper we have discussed about the fundamentals of different types of green house solar dryer, and to develop new design of solar dryer that would maximize warming efficiency. The main goal of this research is to run a computational fluid dynamics analysis on a previous model to analyze the influence of the highest warming within the greenhouse solar dryer.

A review of the significance effect of external factors of the solar dyer design to dried foods product quality

Purpose 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. Design/methodology/approach 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. Findings 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. Research limitations/implications 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. Practical implications 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). Social implications 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. Originality/value 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.

Performance evaluation of the DehytrayTM solar drying device using plantain, pepper and okra under the tropical conditions of Oyo State, Nigeria

The quest for improved performance of access to solar dryers has led to the development of several designs of solar dryers. This study evaluated the performance of the DehytrayTM, a relatively new solar dryer made up of food grade plastic, in comparison with sun drying using plantain, okra and pepper as test crops in five replicated trials. Freshly harvested crops were divided into two batches, weighing 1.3 kg each. The first batch was blanched with salty water (7 g/100 g) for 2 to 4 min while the other was unblanched. Fresh, sun-dried and solar dried samples were analyzed for their proximate composition and microbial load using standard methods. Drying efficiency was determined using standard equations while three thin layer drying models were applied to the experimental data compared according to their coefficient of determination (R2) and root mean square error (RMSE), predicted by non-linear regression analysis using Microsoft Excel solver, 2018. Mean temperatures ranged from 55-65°C and 25.5-34.3°C for DehytrayTM solar dryer and sun drying, respectively. Efficiency of the dryer ranged between 16.6-28.1% (blanched) and 16.3-33.7% (unblanched) for plantain, 18.2-29.8% (blanched) and 19.4-28.8% (unblanched) for okra and 11.7-17.8% (unblanched) and 11.2-17.7% (blanched) for pepper. Efficiency of the sun drying ranged from 1.1-2.1% (blanched) and 1.4-2.3% (unblanched) for plantain, 1.3 -3.1% (blanched) and 1.6- 3.7% (unblanched) for okra and 0.7 -0.9% (unblanched) and 0.7 -1.1% (blanched) for pepper. There was a good retention of nutrients on the solar dried crop compared to that of the sun-dried crop. Mean airflow rate in the DehytrayTM was 0.021 m3/s compared to 0.49 m3/s in the sun drying. The portability and performance of the DehytrayTM makes it a viable option in the humid tropics. Key words: DehytrayTM, drying model, sun drying, solar drying, efficiency, postharvest operation.

Thermodynamic analysis of forced convective solar drying of cocoa with black coated sensible thermal storage material

Thermodynamic analysis of a forced convective solar dryer integrated with black coated sensible (firebrick) thermal storage material (STSM) for cocoa was investigated. The intermittent nature of solar radiation and its consequence on thermal processes such as drying necessitates the introduction of materials for heat supplement to keep the cocoa beans at a raised temperature above the ambient. As a steady flow thermodynamic system, the analysis was carried out based on the first and second laws of thermodynamics to account for the energy involved in the solar drying of cocoa beans. The maximum drying chamber utilization energy during the first and second daytime drying process was 0.739 and 0.724 kJ/kg. The energy utilization (EU) decreased with the increase in time from 12:00 to 18:00 h respectively. Also, the energy utilization ratio (EUR) ranged from 0.190 to 0.577, and 0.222 to 0.931 during the first and second daytime experiments respectively. The collector efficiency varied between 4.2 and 61.2% while the minimum and maximum solar radiation for the two daytimes were 49.6 and 759.6 W/m2 with an average mass flow rate of 0.032 kg/s. The maximum energy efficiencies for the two-day times obtained at 10:00 h were 28.0 and 58.2%. In the drying chamber, the maximum exergy (inflow and loss) for the two-day time drying process was 7.53 and 8.33 kJ/kg, and 4.83 and 8.175 kJ/kg respectively. The exergetic efficiency during the first daytime experiment varied between 1.52 and 65.81%, while it varied between 1.82 and 53.30% during the second daytime. Thus, the results obtained in this study will inform the choice of an appropriate solar dryer design by the relevant stakeholders in the cocoa industry.

Numerical Simulation of Rock-bed Solar Thermal Storage Energy

Solar dryers are increasingly being applied to dry fruits and vegetables in order to increase their shelf-lives. In the sunny-belt countries, the availability of solar irradiance is taken for granted and the mean daily solar irradiation is often used as the design basis for a solar dryer. The predicted performance of the solar irradiance is therefore inherently inaccurate. Contemporary solar dryer designs incorporate thermal energy storage (TES) systems for application after sunset. The performance of such TES systems is often determined experimentally. In this study, mathematical models have been developed and by numerical simulation using the technique of Finite Differential Method (FDM) and MATLAB programming, the performances of solar irradiance as well as that of the TES system have been predicted. The simulation results were secured to inform the design of the solar dryer for fruits and vegetables in the sun-belt countries.

Experimental and numerical optimal design of a household solar fruit and vegetable dryer

In the present study, a low-cost solar fruit and vegetable dryer was designed, constructed, and tested for small-scale production, especially in households. An optimizing procedure was performed to convert a typical widely-used direct cabinet dryer into a new indirect dryer using experimental data and numerical simulations. Several well-designed experiments accompanied by CFD simulations using finite volume method were carried out. It was concluded that the proposed conversion procedure could be achieved utilizing a blackened absorber plate, an air circulating unit, and a honeycomb air manifold. The drying capacity of the dryer could be increased by more than 50% in comparison with the direct type by adding a new tray to the optimized dryer. The thermal efficiency of the proposed solar dryer was estimated 16.4%, indicating that the desirable energy performance of the dryer was superior to some available designs of solar dryers. Besides, it was observed that the proposed numerical approach was able to produce a reliable qualitative and quantitative insight into both the thermal and fluid mechanical behavior of the dryer. Finally, it was claimed that not only was the developed apparatus suitable and efficient for the household usage, but also the optimized version of the dryer could be inspiring for those who are currently using typical direct cabinet dryers to convert their dryers into indirect ones.

Solar thermal drying performance analysis of banana and peach in the region of Gafsa (Tunisia)

The solar drying of foods is considered among the most important green and sustainable food preservation techniques. The development of efficient solar dryer designs and the investigation of food drying characteristics will improve considerably the food preservation. This work proposes to project a solar chimney-dryer and to pack out an experimental thermal study in order to take the appropriate thin layer drying mathematical models for both banana and apricot. The design, essentially composed of an absorber, a glass and a chimney, is described in detail and its functioning, based on air heating, is clearly explained. The evolution of glass temperature, absorber temperature and chimney temperatures are investigated experimentally. All experiments are carried out under the meteorological conditions (solar irradiance and ambient temperature) of the region of Gafsa-Tunisia (34.4311°N, 8.7757°E) during the days June 05, 2018 and June 07, 2018. The solar thin layer drying of two products (banana and peach) is investigated experimentally for two drying air flow rates. Nine empirical mathematical models that predict the evolution of moisture ratio during the thin layer drying process are presented and compared to experimental results. A nonlinear regression analysis study is carried out to select appropriate models for banana and peach drying.