Forced Convection Drying Research Articles

PERFORMANCE EVALUATION OF NATURAL AND FORCED CONVECTION IN SOLAR DRYERS FOR MULLET FISH

Ombak Damai Trading, a Malaysian company specialising in dried mullet fish, needed to dry the fish faster to meet growing demand. They reduced the drying time from 1-2 days to 3-4 hours using a solar dryer. The dryer was equipped with an IoT (Internet of things) weighing system for precise monitoring and data collection. Two inlet fans were added for forced convection drying. Measurements of weight, temperature, and humidity were taken for ten days. The forced convection system was found to be 85.78% effective, compared to 59.36% for natural convection. Moisture analysis revealed that the forced convection system removed more moisture, with a maximum percentage of 36% compared to 22% for natural convection. Forced convection also had a higher drying rate of 60.17 g/hour compared to 37.83 g/hour for natural convection. These findings can help seafood businesses optimise the drying process and achieve target moisture levels. Further studies are recommended to examine the forced convection system's commercial scalability, as well as the effects of drying on nutritional content and sensory qualities.

Experimental study and mathematical modeling of drying kinetics of mint leaves under forced convection

In this study, we investigated the influence of temperature and air velocity on the drying behavior of Mentha spicata L. leaves using a forced convection dryer. This drying method was chosen for its cost-effectiveness and its ability to facilitate fast and efficient drying while preserving the quality of aromatic herbs. Our aim was to identify the most suitable mathematical model for accurately representing the drying process. We analyzed experimental data on moisture content obtained during thin-layer drying of Mentha spicata L. using various established empirical models from existing literature. Thirteen empirical models were applied to fit the drying curves obtained. Statistical analysis, employing key parameters such as the coefficient of determination (R2), reduced chi-square (χ2), and root mean square error (RMSE), indicated that the Midilli and Kucuk model provided the most accurate fit for the observed drying curves. This was evidenced by the highest R2 values (0.9994, 1.0000), lowest χ2 values (6.07 × 10−6, 6.28 × 10−5), and lowest RMSE values (2.17 × 10−3, 6.86 × 10−3). We observed an increasing trend in moisture diffusivity with temperature variations between 32 °C and 60 °C, while maintaining a constant airflow velocity of 1.2 m/s. Additionally, an increase in mean air velocity from 0.7 to 1.7 m/s correlated with higher moisture diffusivity. The effectiveness of the Arrhenius equation in representing the temperature dependence of diffusivity was confirmed, with an activation energy of 72 kJ/mol, consistent with previous literature findings.

Experimental analysis and development of novel drying kinetics model for drying grapes in a double slope solar dryer

This experimental study aimed to evaluate the efficacy of natural and forced convective drying techniques in reducing the moisture content of the grapes in comparison with the conventional open sun drying method. Moisture effective diffusivity and activation energy were graphically determined using the Arrhenius equation. In the initial three-day period, forced convection drying significantly reduced moisture from 2000 g to 353 g, with a minimum loss of 14 g. In the next three days, natural convection reduced moisture from 2787 g to 468 g, with a minimum loss of 11 g. These outcomes were then compared to the results of open-sun drying. The investigation showed that open drying and natural convection methods eliminated 25.05 % and 82.35 % of the moisture content, respectively. However, for three days, open-sun drying removed 30.5 % of grape moisture, while forced convection achieved an impressive 83.21 % reduction. The study's innovative mathematical model explained drying curve characteristics, supported by correlation coefficients and parity plots. The comparison shows that the experimental moisture ratios and those predicted by the new correlation exhibit R2 values ranging from 0.984 to 0.994.

Utilization of PID Controller to Optimize Energy Consumption in Hybrid Forced Convection Dryer

The drying process is essential in food processing, particularly for grains or beans. This process can influence the characteristics and quality of the dried material. However, the drying process needs massive energy. This condition can increase the cost of production. Therefore, optimizing energy is needed during the drying process. PID controller was proposed to be utilized in the dryer to maximize energy efficiency in this study. This method was implemented in forced convection and hybrid forced convection dryer. The temperature sensor was used as parameter control of the PID method to control the electric heater and exhaust fan. Moreover, PZEM-004T was used to measure the energy consumption. The objective of this study is to implement and fine-tune the PID controller to obtain the performance difference between two types of dryers, namely forced convection and hybrid forced convection. This will be achieved by collecting data on power and energy consumption. The results indicate that the hybrid dryer can significantly decrease power and energy consumption by 48.32% and 49.18%, respectively, compared to the forced convection dryer.

Optimization of thermal photovoltaic hybrid solar dryer for drying peanuts

The drying of agricultural products is traditionally carried out using solar radiation. However, this process is time-consuming and also unreliable in locations having cold and humid environments. This study experimentally investigates an innovative air collection system integrated with a dryer. The study focuses on the drying analysis of peanuts utilizing three operational modes of a solar dryer: forced convection, natural convection, and traditional open-sun drying. Key parameters including solar radiation intensity, moisture extraction, and outgoing air temperature from the collector were studied. Solar radiation served as the primary energy source, driving the solar dryer's operation within a drying air temperature range of 33 °C–58 °C, applied to 8 kg of peanuts. Initially, the peanuts exhibited a moisture content of 72 %. The developed solar dryer subsequently reduced the moisture content of the peanut by 18 %. The study evaluated three key aspects: electrical efficiency, thermal efficiency, and overall thermal efficiency of the proposed hybrid collector and solar dryer system, conducted from 9 a.m. to 4 p.m. Results indicate that the forced convection mode of solar drying outperformed the other modes, demonstrating superior effectiveness. These findings hold significant implications for the advancement of solar dryer technology, offering valuable insights for the wider solar drying community.

Exploring forced convective solar drying of henna (Lawsonia inermis) and its effect on the biological activities: Comparison with open sun dried product

The first focus of this study is to investigate the design and behavior of locally built solar dryer during processing henna leaves. This was performed through the determination of the most important parameters that effect drying process. Appropriately, it was found that solar radiation has a direct effect on the collector outlet air temperature and consequently the product moisture content. Accordingly, high radiations lead having high air temperature at the drying chamber and consequently, the moisture content will decrease rapidly. Similarly, lower radiations will still lead to decrease of the moisture content, however, the drying rate will be less important than at high radiations. On the other hand, air velocity has an inverse dissipative effect of the energy and its increase leads to the decrease of the outlet temperature of the solar collector. Indeed, the highest outlet temperature from the solar collector was around 32 °C at an air velocity of 2 m/s. At 5.5 m/s, this temperature dropped to around 27 °C. The second objective of this study is to present the effect of different drying methods (i.e. forced convective solar drying and open sun drying) of Lawsonia inermis on the content of secondary metabolites (phenolic and flavonoid compounds) and compare the results with fresh henna samples. The yield of phenolic compounds was determined, and the dry crude extracts were found to be richer than the fresh sample in all of the drying modes used. The best yields are obtained with convective solar dryer and open sun drying samples (28.6 and 13.93%), respectively. The total phenolic and flavonoid contents of convective solar dryer product were 25 and 10% higher than open sun dried samples. Antioxidant tests (DPPH, ABTS, and ferric reducing power) revealed the scavenging and reducing abilities of the extract dried with the solar dryer. The values of antioxidant capacities measured by the three different methods were all consistent, appropriate, and highly correlative for assessing total antioxidant capacities. The solar dryer allows the preservation or even the increase of the antioxidant activity of the tested extracts.

Computer-Aided Neuro-fuzzy Algorithm for Prediction of Ginger(Zingiber officinale) Rhizome Drying

Neuro-fuzzy modeling technique has been used for the development of computer-based adaptive process control systems for most postharvest operations instead of convectional mechanistic modeling technique owing to its good prediction without prior knowledge of process operation. Therefore, adaptive neuro-fuzzy inference system (ANFIS) modeling and prediction of ginger (Zingiber officinale) rhizome moisture content in a forced convective tray dryer was investigated in this study. Computer codes for an exhaustive search and grid partitioning were written in the Matlab software environment and used for the analysis of experimental data obtained from the ginger rhizome drying experiment. The data were trained and checked using the grid-partitioning ANFIS method for the development of neuro-fuzzy network for ginger drying prediction. The prediction accuracy of the network was evaluated by varying input and output Membership Function (MF) types. The exhaustive search analysis shows that drying time (DT) has the highest effect on the moisture content, followed by air drying temperature (ADT), air relative humidity (ARH), and air flow velocity (AFV). Moreover, combination of DT and ADT as two interactive variables; and combination DT, ADT and ARH as three interactive variables show highest effect on ginger moisture content removal during the process. Generalized bell (gbell) MF with two MF for each input variable and constant output MF 2 type were obtained as the best ginger drying ANFIS network with corresponding R and MSE of 0.9667 and 0.0971, respectively. Therefore, this study shows the reliability of the ANFIS model for the prediction of ginger rhizome drying in a tray dryer.

Computer-Aided Neuro-fuzzy Algorithm for Prediction of Ginger(Zingiber officinale) Rhizome Drying

Neuro-fuzzy modeling technique has been used for the development of computer-based adaptive process control systems for most postharvest operations instead of convectional mechanistic modeling technique owing to its good prediction without prior knowledge of process operation. Therefore, adaptive neuro-fuzzy inference system (ANFIS) modeling and prediction of ginger (Zingiber officinale) rhizome moisture content in a forced convective tray dryer was investigated in this study. Computer codes for an exhaustive search and grid partitioning were written in the Matlab software environment and used for the analysis of experimental data obtained from the ginger rhizome drying experiment. The data were trained and checked using the grid-partitioning ANFIS method for the development of neuro-fuzzy network for ginger drying prediction. The prediction accuracy of the network was evaluated by varying input and output Membership Function (MF) types. The exhaustive search analysis shows that drying time (DT) has the highest effect on the moisture content, followed by air drying temperature (ADT), air relative humidity (ARH), and air flow velocity (AFV). Moreover, combination of DT and ADT as two interactive variables; and combination DT, ADT and ARH as three interactive variables show highest effect on ginger moisture content removal during the process. Generalized bell (gbell) MF with two MF for each input variable and constant output MF 2 type were obtained as the best ginger drying ANFIS network with corresponding R and MSE of 0.9667 and 0.0971, respectively. Therefore, this study shows the reliability of the ANFIS model for the prediction of ginger rhizome drying in a tray dryer.

Evaluation of the Performance of the ATESTA Forced Convection Dryer when Drying Pineapples

Objective: Evaluating the performance of the ATESTA [Solar Energy and Appropriate Technology Workshop] forced convection dryer, developed at the Albert Schweitzer Ecological Center of Burkina [CEAS Burkina], on the drying of pineapple slices in Togo. Method: For this purpose, two ATESTA dryers were setup in a company in Lomé, Togo, one operating in forced convection and the other, the witness, in natural convection mode. Drying tests of pineapple slices were carried out with these two dryers. Data were collected on water loss, organoleptic parameters and energy consumption during the drying process Findings: The results showed that the water loss rate increased by 11.4% as well as the first choice dry matter content by 36% and an energy saving of 21% percent of natural convection to forced convection. This performance of the ATESTA forced convection dryer increases the economic profit of USD [United States Dollar] 2.68/kg or USD 45.52/drying cycle and USD 2678.40/t of dried pineapples. The results of microbiological analyses revealed that the total flora [1.2.102 CFU/g] [Colony-Forming Unit per gram] yeast and mold [6.4.101 CFU/g] content of pineapple slices dried by the ATESTA forced convection dryer were in line with the limit values of the Directive 2000/13/EC [European Parliament and the Council]. Novelty: Performance tests on the forced convection dryer have made a more efficient dryer available to pineapple processors. Forced convection can also be adapted to existing dryers. Keywords: Performance, ATESTA dryer, Togo, Forced convection, Dried prineapple

Controlling temperature using proportional integral and derivative control algorithm for hybrid forced convection solar dryer

Drying is one of the crucial processes in agricultural production, especially in grain processing. The drying process can improve grain quality and affect the grain content. However, maintaining the temperature is a challenge in the drying process. Because it can influence the drying performance and produce a low-efficiency reduction of water content, in this study, the hybrid drying system is proposed to improve the performance of the forced convection dryer system. The proposed system used a proportional integral and derivative (PID) control system to obtain the optimal temperature. The proposed system was compared with natural drying and forced convection methods. The experimental result showed that the proposed system performed excellently for three performance evaluations. The average temperature was obtained as the highest of the other methods, with 54.68 °C and 54.55 °C for coffee and cocoa beans. The water content can be reduced by an average of 27.38% and 42.67% for coffee and cocoa beans. Then, the proposed system also had the highest reduction efficiency of water content than the other methods, with 62.71% and 36.94% reductions for coffee and cocoa beans, respectively. The results indicate that the proposed hybrid system performs better than the other methods.

Simulation of hydrodynamics of the dispersed layer of fruit during solar-convective drying

The article proposes a hydrodynamic model of forced convective drying of fruits and vegetables, in which the direction of the coolant flow to the product being dried, the degree of dispersion of the product layer, the hydrodynamics of drying fruits and vegetables in the form of spheroids, flat disks and flat plates, as well as supports with plastic, metal and wooden gratings, modeled based on the necessary equations and criterion equations.

An innovative forced convection method for drying geosourced and biosourced construction materials at wall scale

As global temperatures continue to rise, climate change impacts are now being observed in all aspects of life, driving the need to transition to a low-carbon economy. In the building sector and as a construction material, Earth-Hemp composites present a sustainable solution due to their low embodied energy and low environmental impact. However, at the construction site, and as with any other material, the drying process of Earth-Hemp can be very slow, which can lead to costly delays for building work and even serious problems in term of mold growth affecting their durability. The objective of this work is to develop an innovative drying method to reduce drying time of construction materials and speed up the completion of a project. In this paper, a comparative study of natural convection drying with innovative forced convection drying is carried out on sprayed Earth-Hemp-Lime "ELH" prototypes. The results show that the innovative forced convection method is very effective for drying ELH materials at an accelerated rate, where the drying period has been reduced by a factor of 2, compared to the drying time required when using the natural convection method.

Single layer drying behaviour of grenade peel in a forced convective solar dryer

Solar drying experiments in thin layer of grenade peel were conducted in forced convection solar dryer consisting of a solar air collector, an auxiliary heater and a drying cabinet. Moreover, grenade peel is sufficiently dried in the ranges of 32 °C to 36 °C of ambient air temperature, 45 to 70 °C of drying air temperature, 32 to 53 % of relative humidity, 0.028 to 0.056 m3s-1 of drying air flow rate and 200 to 950 W/m2 of daily solar radiation. The experimental drying curves show only the falling drying rate period. The main factor in controlling the drying rate was the drying air temperature. The drying rate equation is determined empirically from the characteristic drying curve. Twelve mathematical models were tested to fit the experimental data. The Midilli-Kucuk model was found to satisfactorily describe the solar drying curves.

Monitoring Temperature Profile and Drying Kinetics of Thin-Layer Banana Slices under Controlled Forced Convection Conditions

The drying kinetics of banana slices were examined in a forced convection dryer using an infrared camera to monitor the temperature profile and drying kinetics under control conditions. The air temperature was tested at 40 °C, 50 °C, 60 °C, and 70 °C and the air velocity at 0.2 m/s, 0.5 m/s, and 0.75 m/s, with initial moisture contents of the banana ranging from 76–80% wet basis. The thicknesses of the banana slices being dried were 2, 4, 6, and 8 mm. The optimum drying conditions for the highest drying rate and best color were found to be a temperature of 70 °C, an air velocity of 0.75 m/s, a low relative humidity of 5 to 7%, and banana slices with a thickness of 2 mm. As the air temperature increased, the drying rate and shrinkage also increased. Shrinkage varies concerning moisture loss, and the reduction in radial dimension of banana slices was around 17–23% from the original slice before drying. An empirical mathematical equation was derived by applying the technique of multiple linear regression analysis to the whole dataset of the many experiments of the experimental work. The moisture diffusivity was between 7.88 × 10−10 to 1.04 × 10−10 m2/s, and the average activated energy of the banana was 34.29 kJ/mol. The experimental data were used to fit the drying models. The Midilli model was predicted to produce the closest results to the experimental data.

Qualitative, energy and economic analysis of forced convective solar drying of tomatoes slices

Solar drying is a thermodynamic method of controlling moisture content that uses a non-depletable free renewable energy source. This work discussed a qualitative and economic analysis of a forced convection drying system for tomato slices in an agricultural greenhouse under Tunisian climatic conditions. Then an exergy and energy balances of the drying system were presented. The tomato’s thin layer was dried in a mixed convection solar drier for 79 h and 127 h in a conventional sun drying process from an initial moisture content of 20.27 to 0.36 kg H2O per kg of dry matter. Energy and exergy analyses of the tomato’s drying process were investigated. It was also discovered that the exergy efficiency of the drying chamber ranged from 16.44 percent to 70.47 percent. The overall efficiency of the greenhouse and the solar air collector were calculated to be 42 percent and 62 percent, respectively. To determine the quality of fresh and dried tomatoes, color analysis was performed. A cost-benefit analysis was performed, and the payback period for the system was estimated to be 1.82 years.

Mechanistic modeling and experimental approaches of rice bran drying in a mini-pilot forced convective dryer

Mechanistic modeling and experimental approaches of rice bran drying in a mini-pilot forced convective dryer

Development of novel cabinet solar dryer using UV sheet and its performance evaluation: An experimental study

In this present paper, the experimental study of novel designed ultraviolet (UV) sheet cabinet type solar dryer has been developed at Chhattisgarh Swami Vivekanand Technical University, Bhilai, Chhattisgarh (21˚ 27′ N, 81˚43′ E) for drying banana slices. For this analysis, local weather condition such as solar radiations, atmospheric temperature, wind speed and humidity of air were collected. The solar dryer is designed with drying chamber using six (06) numbers of trays at upper, middle and lower part of chamber using dimensions as 57 cm × 58 cm (2 Tray), 57 cm × 90 cm (2 Tray) and 57 cm × 111 cm (2 Tray), respectively. The same setup has been designed with fan and PV panel for forced convection drying. 2 kg of banana slices were equally distributed in the six (06) trays for drying. It was found that in forced convection, banana slices reaches to equilibrium moisture content of 13.75% (wet basis) from 86.2% (wet basis) of initial moisture content in just 16 h of drying time. Whereas in the same time it reaches to 17.5 % (wet basis) and 17.7% (wet basis) of final moisture content for natural and open sun drying, respectively. It was also observed that the highest temperature was achieved by upper tray. Forced convection drying is the most efficient way of drying when compared to natural and open sun drying.

Numerical simulation of optimal inlet air temperature of a forced convective fish cabinet rotary dryer

Computational fluid dynamics was applied in the prediction of the effect of inlet temperature on the drying time of fish in a cabinet rotary dryer. On completion of the simulation, the temperature distribution of the air (fluid domain) within the drier at different inlet air temperatures and time intervals was obtained. Inlet air temperatures ranging from 35oC to 55oC was simulated for a time interval of 10 minutes to 120 minutes so as to examine the influence of inlet temperature on the drying process of fish. Based on this temperature range, it was observed that the ideal drying time for the fish which satisfies the condition for efficient fish drying for all five inlet air temperatures of the fish is 70 minutes. Furthermore, it can be observed that it takes about 120 minutes for the inlet air temperature of 50 degrees Celsius to attain a cabinet drying temperature of 316K (43°C) while it takes only 70 minutes for the inlet air temperature of 55 degrees Celsius to attain the same temperature under the same condition.

Photovoltaic Forced Convection Greenhouse Solar Dryer with an Integrated Vertical Solar Collector for Mango Drying

The design and experimentation of a Photovoltaic forced convection greenhouse solar dryer with a vertical solar collector incorporated inside the drying chamber for mango drying is presented. The integrated vertical solar collector combined the features of a south wall and a solar air heater to capture solar radiation that escapes through the south wall (north wall for the northern hemisphere) and heat the air before it enters the drying chamber. Mango drying experiments were carried out to ascertain the performance of the dryer. The solar radiation at the beginning of the experiments at 08:30 hours was 525.1 W/m2, reaching a maximum of 1,133.0 W/m2 shortly after midday and decreasing to 492.4 W/m2 at 16:30 hours when the experiments were stopped. The ambient temperature and relative humidity ranged from 28.4 ⁰C to 36.4 ⁰C and 19.9% to 37.8%, respectively. Under these conditions, the air temperature inside the drying chamber was on average 14.7 ⁰C above ambient, resulting in high drying rates such that the mango reached the moisture content of 13.7% wet basis after 7.5 hours of drying. The incorporation of a vertical solar collector inside the drying chamber helped, through storing heat in its mass, stabilise the drying chamber air temperature and made the forced convection dryer more compact thereby reducing usage of the space outside the dryer  and making it available for other operations.

Sustainability and 4E analysis of novel solar photovoltaic-thermal solar dryer under forced and natural convection drying

Developing a sustainable photovoltaic-thermal (PVT) solar drying system is essential to maintain zero carbon emission in the drying process. This work represents the drying of star fruit in a novel PVT solar dryer to analyze the sustainability indicators based on the energy and exergy performance with the environmental and economic evaluation (4E) under forced convection drying (FCD) and natural convection drying (NCD). The moisture content of star fruit in the PVT solar dryer is decreased from 10.11 (d b) to 0.19 (d b.) in 12.50 h and 14.50 h under FCD and NCD, respectively. The same has been obtained in open sun conditions with a drying time of 22.00 h. The PVT energy and exergy efficiencies are 69.27% and 31.12% in FCD mode, respectively, and 43.58% and 17.89% in NCD mode. The drying efficiency of 15.27% and 13.98%, specific moisture extraction rate of 0.1786 kg/kWh and 0.6657 kg/kWh, and specific energy consumption of 12.37 kWh/kg and 3.57 kWh/kg are evaluated in FCD and NCD modes, respectively. The drying system payback time is 1.40 yr and 1.70 yr in FCD and NCD mode, respectively.