Drying Chamber Temperature Research Articles

Insights into nanostructured silica particle formation from sodium silicate using spray drying: An experimental and theoretical study

Spray drying is a widely used operational procedure utilized in diverse sectors. The current knowledge of droplet mobility processesinside the drying chamber is not fully comprehensive due to the complex nature of droplet evaporation issues. The present study used a comprehensive methodology that integrated numerical models and actual testing to investigate the drying process of droplets in the context of spray drying. The precursor material utilized in this investigation was colloidal silica. The influence of external hydrodynamic variables, such as drying temperature (473, 673, and 873 K) and carrier gas flow rate (2, 4, 6 L/min), was thoroughly investigated in connection to the dynamics of droplets and the subsequent creation of silica particles. Distinct alterations in the size and shape of the silica particles were observed due to variations in drying temperature and carrier gas flow rate. The validity of this investigation was established by the generation of two discrete particle morphologies, namely spherical particles and doughnut-shaped particles. Spherical particles were produced under reduced carrier gas flow rates of 2 L/min and lower drying chamber temperatures of 473 K. In the quantitative evaluation, the computational fluid dynamics (CFD) computations properly established the evaporation rate constant (K) and the temperature difference (ΔT) inside the droplets. Furthermore, qualitative calculations provide insight into the complex dynamics of droplet motion inside the spray chamber. The results of this study have the potential to open up new possibilities for regulating nanoparticle creation via the use of the spray drying process.

Design and optimization of a domestic solar dryer: an analytical approach

PurposeFood loss and wastage is an issue of global concern and the household sector is one of the biggest contributors to this. Solar drying has been explored by many eminent researchers as a solution to this problem but there have been concerns about the lack in designs, higher cost, lower performance, and consumer acceptability. The present research aims to design a small-scale domestic solar dryer by using computer software.Design/methodology/approachResponse surface methodology (RSM) and computational fluid dynamics (CFD) are used to design the domestic solar dryer. Initially, design variables (inlet and outlet vent height) are identified and a design of experiments has been created using RSM for set of experimental runs. The experimental runs suggested by RSM were carried out using CFD simulation in COMSOL Multiphysics software and the results were used for optimization of response variables (outlet velocity and drying chamber temperature) in RSM.FindingsOutlet vent height was found to be most significantly affecting parameter to both the responses. The optimum values of inlet and outlet vent heights were 0.5 and 2.5 cm, respectively with the overall desirability of 0.728. The model accuracy was tested by conducting a confirmation test as post processing in design expert software.Originality/valueDesigning a solar dryer is a complex, costly and time consuming process, this study presents an easy, economic and fast method to design a new solar dryer. It would help researchers to design and develop new domestic as well as large size industrial solar dryer.

Computational study of the performance of a solar dryer for improvement in the shelf life of the food materials.

In this study, the thermal and drying characteristics of a thin layer food sample were investigated. An indirect type, simple, efficient, and economically feasible solar dryer was fabricated and used for food preservation. However, a dynamic model of a fabricated solar dryer was also presented to gain a better insight into the drying and thermal actions. This model consists of thermal modeling of the drying chamber, solar collector, and solar-dried food sample. The law of conservation of energy was applied to evaluate the temperature at different sections of the solar dryer with respect to drying time. All listed model equations were solved in the MATLAB environment. This study helps to examine the influence of solar radiation on the collector plate temperature, drying chamber temperature, food sample temperature, and performance parameters such as thermal efficiency with respect to drying time. Model data was found in good agreement with experimental data within a 4% error. It is concluded that the drying of food material is affected by air temperature, the collector temperature, mode of heat transfer, and material characteristics such as dimension and mass of the food sample.

Characteristics of temperature uniformity system in multi-tier drying equipment with sharp turning technology

Drying is a process of heat and mass transfer that occurs on the surface and within the material to be dried. It helps reduce the internal moisture of the material, inhibiting the growth, damage, and chemical changes of microorganisms during storage, thus extending the shelf life of dry materials and improving the quality of raw materials. This study aims to test multi-level drying equipment using combustion heat with a square shape and racks inside it used as the drying space for the material. The raw material was placed on racks made of perforated metal. This research started from designing the drying equipment system, fabricating and testing system. The drying system was tested using fish and cocoa beans as sample materials. The tested equipment system included temperature distribution in the combustion chamber, distribution system of hot combustion gases through sharp turning technology, uniform temperature distribution in the drying chamber with 8 levels of racks, each capable of holding a load of 10 kg, and testing of the chimney system. The research findings concluded that to maintain a drying chamber temperature of 90⁰C, an average combustion chamber temperature of 339⁰C was required. The average combustion chamber temperature needed to maintain a drying chamber temperature of 80⁰C was 290⁰C. For a drying chamber temperature of 70⁰C, an average combustion chamber temperature of 314⁰C was required. The temperature distribution inside the drying chamber moves horizontally, indicating that the temperature distribution in the drying chamber was uniform for each drying rack.

An experimental evaluation of drying banana slices using a novel indirect solar dryer under variable conditions

Novel thermal characteristics of drying banana slices in an indirect dryer are presented for four different experimental drying conditions in the forced convection mode. The novel characteristics include measuring the airflow velocity in the drying chamber, measuring the thermal profiles in different trays comprehensively and measuring the relative humidity under different conditions. Two tests are carried for 16 h in two consecutive days (8 h per day for each test). The first test is on acloudy day followed by a sunny day, while the second test is carried out on two consecutive sunny days. Tests 3 and 4 are 24 h tests with high (0.23 m/s) and low (0.11 m/s) average drying chamber airflow velocities under good solar radiation conditions. The maximum temperatures obtained in the collector and the drying chamber are around 80 and 48 °C, respectively, for the 16 h tests. Significantly lower collector and drying chamber temperatures are obtained due to cloudy conditions. Maximum collector temperatures are around 84 and 95 °C for the high and low average airflow chamber velocities for the 24 h tests. The corresponding maximum temperatures in the drying chamber are around 50 °C for the 24 tests. The final moisture ratios are 0.26 (cloudy and sunny days) and 0.20 (two sunny days), respectively, for the 16 h tests. These final moisture ratios are lower than those obtained for the 24 h tests which are 0.32 and 0.28, respectively. Increasing the drying chamber airflow velocity results in faster moisture removal during sunshine hours for the 24 h tests. For tests 1, 2, 3 and 4, the maximum average collector efficiencies during the sunshine period are around 60, 80, 40 and 10 %, respectively. The average drying efficiencies for the total solar drying period for tests 1,2,3 and 4 on day 1 are 6.9, 6.9, 5.5 and 5.7 % respectively. These values are comparable, suggesting that the average collector powers, airflow velocities and efficiencies have a very small effect on the average solar drying efficiency for the whole drying period. The quality of the bananas slices mainly in terms of the colour and shape is also compared with previous studies and commercially available products. A reasonably acceptable quality product is obtained.

Energy, Exergy and Economic Analysis of a Mixed-mode Natural Convection Solar Tunnel Dryer for Banana Slices

The energy, exergy and economic analysis of a mixed-mode natural convection solar tunnel dryer for drying banana slices is presented. The collector, drying chamber and chimney energy and exergy are analysed for a load of 3.75 kg of fresh banana slices. Further, the economic analysis in terms of Net Present Value (NPV), Profitability Index (PI), the Payback Period (PB) and the Discounted Payback Period are presented. Drying experiments were done in a period of two days. During the experiment, solar radiation varied from 206.1 W/m2 to 934.5 W/m2; drying chamber temperature varied from 51.7ºC to 81.84ºC while the ambient temperature varied from 21.7ºC to 31.9ºC. The relative humidity ranged from 4.63% to 28.46% for the drying chamber and, 14.9% to 31.8% for the ambient. Under these conditions, the moisture content of the bananas was reduced from 73.89% to 14.27% in seven hours of drying on the first day. Energy and exergy efficiencies ranged from 5.56% to 57.32%, and 0.33% to 2.81%, respectively on Day 1. For Day 2 the energy and exergy efficiencies were from 14.15% to 59.16%, and 0.75% to 3.76%, respectively. For the drying chamber, the efficiency increased gradually in the first two hours to a maximum of 5.36%, corresponding to the period when there was maximum evaporation. The chimney, which is a bare flat plate type without glazing and insulation, lost heat from its surfaces. Nonetheless, it generated enough buoyancy to move air through the dryer. With the solar dryer lifespan of 10 years and the Discounted Payback Period of four years, the project is attractive and worth investing in.

Comparison of mixed-mode forced-convection solar dryer with and without stainless wire mesh in solar collector

Abstract A mixed-mode forced-convection solar dryer (MMFCSD) is a device that utilizes both direct and indirect solar energy. The solar collector, which stores thermal energy for indirect solar uses, is an essential component of the dryer. Unfortunately, the thermal efficiency of this device is generally low. In this study, a technique was employed to improve the heat transfer of the solar collector in a MMFCSD. The technique involved adjusting the air flow pattern into a swirling flow to disturb the thermal boundary layer on the absorber plate under forced convection by using stainless wire mesh. The experiment was conducted under actual conditions and bananas were used as the drying sample. The experimental results of the thermal efficiency of the solar collector (ƞsolar) and the drying efficiency (ƞdrying) are presented. The results indicated that the air outlet temperature and ƞsolar of the solar collector with stainless wire mesh were higher than the case without stainless wire mesh, reaching a maximum temperature of 46.22°C and 37.97°C, and average ƞsolar of 0.26 ± 0.02 and 0.14 ± 0.01, respectively. The MMFCSD with stainless wire mesh had a higher ƞdrying than the case without stainless wire mesh, with values of 0.048 ± 0.004 and 0.039 ± 0.003, respectively, resulting in an ~23.07% increase. This was attributed to the air swirling flow through the stainless wire mesh and the heat accumulation in the drying chamber, which led to an increase in the drying chamber temperature from 54.03°C to 63.60°C, an increase in the effective moisture diffusivity from 7.28 × 10–7 to 1.19 × 10–6 m2/s and a decrease in the drying time of 5 h 30 min. However, further research is needed to investigate the quality of the dried samples and their economic value.

Lyophilization as an alternative for conservation of equine plasma as a source of IgG for neonatal foals

The administration of plasma to foals with failed transfer of passive immunity is of utmost importance. Transporting refrigerated or frozen plasma to farms can be costly and complicated. Lyophilized plasma can facilitate transport and storage by improving and spreading the technology. Lyophilization is the most commonly used method for preparing dehydrated proteins, which must have adequate stability for an extended storage period at room temperature. This work aimed to evaluate the IgG concentration of fresh equine plasma (EP) and post-lyophilization. Plasma was collected from 6 healthy male horses, age 4±2 years, 356±62kg. An aliquot of EP was lyophilized. The lyophilization process was carried out at the Research Support Center of the Federal Rural University of Pernambuco. Before being lyophilized, samples were frozen at -80°C for 24 h and then processed, in an Alpha 1-4 LD Plus Christ apparatus, a drying chamber temperature of -27°C and vacuum of 0.52 mbar, for 24 hours. The lyophilized EP obtained was stored in well-sealed microtubes and frozen at -4°C for further analysis. The lyophilized EP was resuspended in deionized water to maintain the original volume. The concentration of IgG in fresh EP and lyophilized and resuspended EP was measured. Samples were evaluated using Simple Radial Immunodiffusion kits (IDRS) commercially available forequine serum and colostrum: IDRING® Horse IgG Test, by IDBiotech (Issoire/France). Horse IgG test plates contain an agar gel with a specific antiserum against horse IgG. Plate wells are filled with standards of 200, 100, 50, and 25 μg/mL of horse IgG and the EP and lyophylised EP samples. During diffusion on the agar gel, the antibodies specifically react with the antigen to form a precipitation ring. A linear calibration curve is established to determine the samples’ IgG concentrations from the measured diameters to known concentrations in the standard calibration set. The homogeneity of the variance between treatments was verified by the Shapiro-Wilk test. The results were subjected to analysis of variance (ANOVA) to determine the effects of lyophilization on the IgG concentrations. Significance was declared at P<0.05. When significant differences were tested using the Tukey, significance was set at P<0.05. The IgG concentration in fresh plasma was 8.9±3.2 g/L; after lyophilization, the plasma showed an IgG concentration of 7.1±2.2 g/L. No significant differences were found in the plasma IgG concentrations (P>0.05). The results suggest that lyophilization can be an alternative for conserving EP, since it is a very efficient process to maintain IgG concentration. Further studies should be carried out regarding the administration of plasma in the foal and the transfer of immunity.

Platelet-rich plasma: lyophilization as an alternative for conservation and transport

Platelet-rich plasma (PRP) has been used in equine reproduction to improve pregnancy rates due to its immune-modulating effect. Platelet granules contain numerous proteins, such as growth factors, cytokines, and antimicrobial peptides. However, the shelf life of platelets is 5 days and used at a temperature above 20°C, where there is the concern of bacterial contamination. Also, preparation is a time-consuming procedure. Therefore, studies to find an effective method of PRP storage would be of great benefit, saving costs, and could also guarantee a faster and more effective treatment. This work compared the platelet levels between fresh and lyophilized PRP. Peripheral blood from 8 healthy equine males with a mean age of 4±2years was collected in 4.5-mL vacutainer tubes containing 3.2% sodium citrate. The PRP preparation was performed by double centrifugation in vacutainer tubes. Blood was homogenized and centrifuged at 120g for 10 minutes. After the first centrifugation, the upper 30% of the plasma was discarded. The remaining plasma (70%) was submitted to another centrifugation at 240g for 10 minutes. After the second centrifugation, 30% of plasma at the bottom of each tube was considered PRP. Platelet count was carried out with an automated hematology analyzer (HematoClin 2.6VET - Bioclin IL, USA). The lyophilization process was carried out at the Research Support Center of the Federal RuralUniversity of Pernambuco. Before being lyophilized, samples were frozen at -80°C for 24 h and then processed in an Alpha 1-4 LD Plus Christ apparatus, a drying chamber temperature of -27°C and vacuum of 0.52 mbar, for 24 hours. The lyophilized PRP obtained was stored in well-sealed microtubes and kept frozen at -4°C for further analysis. The results were subjected to analysis of variance (ANOVA) to determine the effects of lyophilization on the platelet concentrations. Significance was declared at P<0.05. The median platelet count in the fresh PRP was 108±35.2 × 103/uL. The platelet count after lyophilization was 46.6% lower (p<0.05) when compared with the initial count (56±17.7 × 103/uL). Although there was a significant reduction in platelet concentration after lyophilization, 53.4% of platelets were viable after the process. Our study showed the viability of lyophilizing PRP using a standard and easy system. Despite several published studies on PRP standardization, to the best of our knowledge, this is the first work on equine PRP lyophilization. In addition, lyophilized PRP appears to be a possible alternative to fresh PRP; with minor variability, a large-scale production with increased shelf life could be achieved following a single production process. Further studies are needed, mainly on growth factors after lyophilization and the use of PRP in vivo.

Numerical Simulation of the 3D Simultaneous Heat and Mass Transfer in a Forced Convection Solar Drying System Integrated With Thermal Storage Material

Abstract The demand for quality dried products necessitates cost effective and innovative drying techniques that will improve its market value. The slow drying rate, weather dependency, and moisture reabsorption have been identified as the major challenges of solar drying operation. To address these shortcomings, hybrid solar drying systems have been recommended for the drying of various agricultural materials and other porous products. Designing a better drying system to accommodate thermal storage materials requires detailed analysis, which could be achieved through numerical simulation. Therefore, the numerical simulation of heat and mass transfer in a forced convection solar drying system integrated with black-coated firebrick sensible thermal storage materials (STSM) for the cocoa beans, locust beans, cereal grains, etc., was investigated under no-load conditions. The equations governing the fluid flow for a three-dimensional solar drying system were solved using the finite volume method with the aid of ansys, the computational fluid dynamics software to comprehend the dynamic and thermal behavior of the airflow within the dryer. The experimental maximum temperature values of 96.9 °C and 77.3 °C for the collector and drying chamber were in agreement with the simulated maximum collector and drying chamber temperatures of 116.9 °C and 80 °C respectively. The designed solar drying system with the incorporated STSM showed the capacity of raising the temperature of the air within the drying chamber to 3–37 °C above ambient temperature between 01:00 p.m. and 10:00 p.m. The agreement of the simulated dryer model with the experimental one is an indication that the developed dryer is suitable for drying cocoa, locust beans, fish, cereal grains, and some other agricultural products within an acceptable period based on the previous studies and therefore, the drying system is recommended to avoid the shortcomings associated with traditional/open sun drying.

A detailed analysis of a novel auto-controlled solar drying system combined with thermal energy storage concentrated solar air heater (CSAC) and concentrated photovoltaic/thermal (CPV/T)

In recent years, the use of solar energy, one of the renewable energy sources, has been increasing in many areas due to its practical, environmental, and economic benefits. Besides, the drying industry is an applied area where solar energy can be implemented. Solar drying systems are used in the industry to reduce high drying costs and to obtain better quality products. In this study, a novel solar drying system was designed by combining concentrated solar air collector (CSAC) and concentrated photovoltaic/thermal system (CPV/T). In addition, the automation system has been integrated for data acquisition from the system and humidity-temperature control of the drying chamber. The SAC's inlet air was preheated by a heat exchanger using thermal energy from the PV/T. The drying system has been designed to be more useful by using phase change material in the collector. Thus, the drying process can be performed on cloudy days and after sunset. In addition, the designed system can generate electricity from the PV module to meet the electricity requirement. The mint which grows in various regions worldwide was chosen as the product to be dried in this study. Mint was dried from the first moisture content of 3.3125 g water/g dry matter to the last moisture content of 0.0625 g water/g water/g dry matter. Besides, the average overall efficiency of the system, PV module electrical efficiency, and drying efficiency were found to be 61%, 10%, and 26%, respectively. Furthermore, the average system exergy efficiency, PV module exergy efficiency, and concentrated solar air heater exergy efficiency values were calculated as 20%, 16%, and 21.9%, respectively. In the experiment, the ambient average temperature was 22 °C, while the average drying chamber temperature was 30 °C. The mint drying quality efficiency was 67% on average at this drying chamber temperature. The energy, exergy efficiency, and sustainability index of the system were calculated as 61%, 38.8%, and 1.69, respectively. Moreover, the enviro-economic cost of the system was determined to be 0.39 ¢/h.

Analysis on characteristics and operation mode of direct solar collector coupled heat pump drying system

To solve the intermittent problem of solar drying systems, this study proposes a solar vacuum tube collector coupled heat pump drying (HPD) system that can adopt three operating modes as different climatic conditions. The performance of the system under different working modes and drying characteristics was analyzed; moreover, the system was also based on the relationship between energy supply and consumption. The results show that under load conditions, the system runs in the solar drying (SD) mode and the drying chamber temperature can reach >50 °C. In the HPD mode, the average heating power of the system is 11.88 kW, the heating coefficient is 2.26 and the average thermal efficiency of the heat exchanger is 39.3%. In the solar-assisted heat pump drying (SAHPD) mode, the average coefficient of performance of the system is 3.26, compared to HPD model, a 44.2% increase. The heating ratios of the SD, HPD and SAHPD modes were 37.9%, 58.5% and 3.6%, respectively. Furthermore, the Two-term models with R2 value of 0.9986 and RMSE value of 0.01038 was considered the best drying kinetics model for the vacuum tube collector coupled heat pump drying grapes. This study guides the application of SAHPD systems in agricultural products drying.

Performance evaluation of indirect type forced convection solar mango dryer: A sustainable way of food preservation

India like other developing countries adopts many food preservation technologies using fossil fuels. But the fossil fuel resource depletes over the years and is non-renewable. Therefore, solar drying technology is preferred as a sustainable method for food preservation. The present study is aimed at a sustainable livelihood initiative for drying fruits and vegetables through solar technology intervention using an indirect forced convection type solar dryer. Such a dryer of 15 kg capacity has been designed and fabricated for drying mangoes. Performance indicators such as instantaneous collector efficiency, drying efficiency, drying rate, COP, heat utilization factor, and moisture content on a dry basis are evaluated as 59%, 32.25%, 0.15178 kg/hr, 0.77, 0.229, and 2.55, respectively by considering maximum outlet collector temperature, drying chamber temperature and atmospheric temperature. Economic indicators such as pay-back period and cost-benefit ratio are also evaluated as 1.439 and 2.0008, respectively. The dryer can be used by rural people of Odisha for earning their livelihood.

Optimization of drying parameters for hybrid indirect solar dryer for banana slices using response surface methodology

Present research work focuses on applying response surface methodology (RSM) in optimization and modeling dried banana slices in a hybrid indirect solar dryer. The relationship of independent variables in terms of mass of banana slices (kg), drying chamber temperature (°C), water flow rate (L/hr), and geometry (cm2). Therefore, responses of interest or dependent variable consisting of moisture content (% db), energy consumption (kW/h), and shrinkage (%) utilization are concluded. A short drying period and energy consumption are seen as the optimizing drying parameters of banana slices. Response surface methodology with central composite design (CCD) was applied to optimize the dependent variable. Experimentally observed data are adjusted by applying a second-order polynomial regression model. The predicted R2 in the range of 0.9828–0.9530, adjusted R2 value (0.9571–0.9974), and model F value (08.18) for banana slices were calculated. Optimal operational parameters are observed 89.99 ℃ (drying cabin temperature), 14.0 L/hr (water flow rate), 0.9998 (circular geometry), and 0.24004 kg (product mass). Optimum responses were 7.55% db (moisture content, MC), 5.54 kW/h (energy consumption), and 69.54% (shrinkage). Further, experiment was conducted at optimal operating conditions, and the results indicate good consistency between predicted and experimental data with a deviation of 3.14%, 2.16% and, 1.41% for the minimum moisture content (wb), energy consumption and, shrinkage, respectively.

Temporal and spatial representation of temperature and moisture in drying chamber and its impact on vertical vacuum dehumidifying rice seed dryer performance

Population growth is resulting in a daily increase in rice consumption demand. To grow paddy for this expanding population, quality seeds are necessary. The study was conducted to evaluate the performance and estimate the drying cost of the vertical vacuum dehumidifying dryer. The studied dryer consists of four main parts: drying chamber, heating and cooling chamber, compressor and blower. The paddy (BRRI dhan 80) sample sizes were 100, 125 and 150 kg as treatment per batch. In three treatments, the drying chamber temperature was varied from 21.1 to 57.0 °C. Paddy was dried from initial moisture content 21.8 to 10.6%, 21.1 to 12.0% and 20.7 to 11.9% in three treatments within the drying time of 6.0, 6.5 and 7.0 hrs respectively. During the drying process, the relative humidity was differed from 60 to 35%. The rate of drying was found 2.08, 2.12 and 2.01 kghr −1 respectively for 100, 125 and 150 kg per batch. The capacities of the dryer were found 16.66, 19.23 and 21.43 kghr −1 for three treatments respectively. The drying efficiency was found 68.85% (for 100 kg batch), 69.85% (for 125 kg batch) and 66.20% (for 150 kg batch). The drying cost of paddy (Tk./kg) was found 0.71, 0.56 and 0.47 for three treatments respectively. • The performance of the vertical vacuum dehumidifying rice seed dryer was assessed in terms of drying rate, drying capacity, drying efficiency, and drying cost. • The temperatures of different points in the drying chamber were obtained in the range of 44.2–57.0 °C. • The paddy moisture content was reduced to the final moisture content of 10.6–12.0%. • The Vertical Vacuum Dehumidifying dryer meets the requirements of Bangladesh's small-scale farmers in terms of drying efficiency, drying capacity, and drying cost.

Computational Fluid Dynamics (CFD) Modelling of ZnO-SiO2 Composite Through a Consecutive Electrospray and Spray Drying Method

Modelling of the droplet formation and drying process in the synthesis of Zinc Oxide-Silicon Dioxide (ZnO-SiO2) composite have been conducted through a CFD modelling. In general, modelling of spray drying only focused on exploring the drying chamber section. The phenomenon builds in a consecutive electrospray and spray drying method has been successfully studied in this paper. The influence of carrier gas flow rate (2 to 10 L/min), precursor flow rate (1 to 10 ml/h), drying chamber temperature and applied voltage (12 to 14 kV) were investigated systematically. Numerical modelling was conducted to describe the mechanism of the composite droplet formation through the jet shape of the electrospray. Evaporation of the initial composite droplet was considered in the modelling, accounting for its size evolution. Simultaneous mass transfer modelling due to the composite evaporation was solved in combination with a general dynamic equation solution. The modelling results show that the applied voltage and the precursor flow rate effectively affected the composite droplet size. While the carrier gas flow rate and the drying chamber temperature, influenced the effectiveness of the composite particle formation in the spray drying synthesis.

Investigating shrinkage corrected drying characteristics, rehydration, color profile and microstructural evolution during solar drying of pineapple slices

AbstractThe study describes the solar drying characteristics of pineapple slices with incorporation of shrinkage and influence of drying and rehydration on structural alterations, color profile and microstructure. Samples were dried in mixed mode solar dryer at an air velocity of 0.5 m/s, with recorded average solar radiation, ambient and drying chamber temperature of 665 W/m2, 33°C and 65°C, respectively, from initial moisture content of 89.9% to a final moisture content of 23% in 6.5 h. Samples showed 43.7% higher drying rate and 82.25% lesser moisture diffusivity on consideration of shrinkage. Moisture diffusivity was increased with a reduction in moisture content during drying on ignoring the shrinkage, while it was initially increased and then gradually reduced at later hours when shrinkage effect was considered. The slices showed overall shrinkage of 86.95% during drying but could recover only 35–45.57% of its volume during rehydration. The water absorption and volume recovery were consistently higher at rehydration temperature of 60°C followed by 45°C and 30°C. Solar dried and rehydrated samples demonstrated overall color change of 16.80 ± 1.15 and 5.87 ± 2.5–7.56 ± 1.43, respectively. Scanning electron micrographs of solar dried samples presented collapsed cellular matrix but rehydrated samples showed porous microstructure indicating regaining of honeycomb network.Practical ApplicationsSolar drying is an essential sustainable approach to reduce the tremendous post‐harvest losses of fruits and it also offers the advantages of energy cost saving, higher affordability level and greater payback power to farmers. Present study explored the drying characteristics, followed by rehydration characteristics and effect of drying and rehydration on quality attributes of pineapple slices. Therefore, results are helpful for food processors and engineers in optimization of drying and rehydration processes to obtain best quality products, shelf‐life extension of perishable fruits. Solar dried pineapple slices will give better returns to farmers. Moreover, dried pineapple can be utilized as dried chips/snacks, powder, etc. and also can be further rehydrated to reconstitute for utilization in different value added food products like ice‐cream, cakes, flakes, granules etc.

Evacuated tube solar and sun drying of beetroot slices: Comparative assessment of thermal performance, drying kinetics, and quality analysis

In this research work, the thermal performance of an evacuated tube solar dryer (ETSD) was investigated at no-load and with load of beetroot slices for drying. The experiments were performed in both ETSD and sun drying to compare drying kinetics, mass transfer phenomena, colour changes, and retention of bioactive compounds of beetroot slices. At no-load condition, maximum ambient and drying chamber temperature achieved were 41.50 °C and 75 °C respectively. The initial moisture content was found to be 84.05% which reduced to 9.25% and 13.56% in ETSD and sun-drying, respectively. Average drying rate was found to be 8.5 g water/g dry solid. hr and 7.94 g water/g dry solid. hr. in ETSD and sun-drying respectively. Weibull and Midilli kucuk models precisely described the drying kinetics of beetroot slices in ETSD and sun-drying, respectively. The effective moisture diffusivity range, activation energy, and maximum mass transfer coefficient of beetroot slices dried in ETSD were 1.01 × 10-7 to 2.45 × 10-7 m2/s, 27.60 kJ/mole, and 3.23 × 10-4 m/s respectively while for sun drying these parameters are 1.19 × 10-7 to 2.24 × 10-7 m2/s, 57.15 kJ/mole, and 3.18 × 10-4 m/s. Betalain pigment retention was higher by 63.98% in ETSD drying than sun drying. The colour changes were found to be higher in sun drying. The average phenolic content and antioxidant capacity were higher by 31.07% and 21.87% in ETSD as compared to sun drying. Therefore, the ETSD can effectively dry other food commodities with reduced drying time and significant retention of quality attributes.

Experimental study of infrared – assisted heat pump drying of lime slices

This paper describes the experimental drying of lime slices using an infrared –assisted heat pump dryer. Experiments were carried out on a heat pump dryer model with a capacity of 1 HP integrated with 2000 W infrared radiator whose power can be varied from 0% to 100%. Experiments have been performed with the drying capacity of 1,2 kg/batch and the drying air velocity of 1,2 m/s. Three evaluations were considered: the effect of material thickness on drying time; the effect of temperature in drying chamber and intensity of infrared radiation on drying time, power consumption and product quality. The results showed that the drying process having 3 mm thickness of lime slices, the temperature in the drying chamber of 42,5¸45oC and the radiation intensity of 110¸300W/m2 was the good effective drying range. In addition, the study formulated a linear regression equation for the drying time relationship with drying chamber temperature and infrared radiation intensity. This mathematical model can be used as reference to determine actual drying time as well as a helpful tool for designing infrared - heat pump dryer.

Standardization of blood meal production process at a rendering plant using design of experiments

This research focuses on the standardization of the blood meal production process at a Colombian rendering plant through a design of experiments. Initially, 108 samples of blood meal were taken where only 23% achieved the moisture target (7.5% to 8.5%). Therefore, an analysis of the measurement system was performed using a repeatability and reproducibility (R&amp;R) study. Results showed that 39.96% of the observed variability was caused by the measurement system that was out of control. So, it was necessary to improve the method of sampling reducing the participation of the measurement system in the variability of the process to only 3.79%. Later, several experiments were accomplished with a 2k factorial design. Each experiment consisted of a response variable (blood meal moisture), two controllable factors (drying chamber temperature and percentage of rotation of the metering screw), and an uncontrollable factor (initial blood meal moisture). Finally, experiments were carried out and validated observing that, with a drying chamber temperature of 160 °C and a percentage of screw rotation of 29%, more than 97% of the blood meal was according to the moisture target. In conclusion, is confirmed that the design of experiments is a tool that allows a clear path towards optimization and standardization of processes.