Indirect Dryer Research Articles

Perkembangan Teknologi Pengering surya


 
 
 
 Solar dryers used in agriculture for food and crop drying are used for industrial drying processes. They can be proved to be a very useful device from the energy conservation point of view. It not only saves energy but also saves a lot of time, occupies less area, improves quality of the product, makes the process more efficient, and also protects the environment. Solar dryers circumvent some of the major disadvantages of classical drying. Solar drying under controlled conditions of temperature and moisture removing rate ensures perfect drying and desirable product quality. The percentage of moisture content in different agricultural products is different and varies product to product. For drying different moisture content products, the drying systems are usually classified as low and high temperature operated drying systems. The indirect, direct, and mixed mode dryers that have shown potential in drying agricultural products in the tropical and subtropical countries are discussed. A side from identifying the active and passive mode solar dryers, they also highlight the environmental influence on solar energy (harnessing) that plays a vital role in the solar drying sector. The classifications of sun drying procedures are created based on the stage of processing, the location of drying, or the apprehension to solar radiation. This paper also presents the related technologies that can help improve existing solar dryers.
 
 
 

Indirect Dryers for Biomass Drying—Comparison of Experimental Characteristics for Drum and Rotary Configurations

This paper focuses on indirect biomass drying. It compares the operating characteristics of a laboratory-scale drum dryer and a pilot-scale rotary dryer. Before the design of an industrial dryer for a specific material, it is important to experimentally prove the process and to determine the drying characteristics of the material. To verify the portability of experimental results for indirect dryers, a drum dryer with indirect electric heating in a laboratory scale was designed and built to test and study the process of indirect drying. Based on the results obtained on a small-scale device, a prototype of a pilot steam-heated rotary dryer was designed and manufactured. A broad range of experiments with green wood chips and wet bark from open-air storage with moisture contents of 50 to 65 wt % were carried out on both dryers. The drying curves indicating the process, the square and volumetric evaporation capacities, and the drying energy consumption were obtained and compared, and the feasibility of indirect drying for these tested types of biomass was confirmed.

Comparative Studies of Two Developed On-farm Solar Dryers for Vegetables

This research work was carried out to provide local farmers with on-farm solar dryers to minimize post-harvest losses of vegetables. Two dryers (Mixed mode and Indirect mode on-farm solar dryers) were constructed using locally available materials. The dryers basically consist of a blower, a collector area and a drying chamber. Aluminum sheet is placed inside the collector which serves as the absorbing material. An electrical axial fan was placed before the air duct to supply air responsible for forcing heated air to blow over the vegetables to be dried. Incorporated in the drying chamber are trays which provide a platform where the products to be dried were spread evenly. Transparent polythene material of 0.2 mm thickness with wooden frame was used as cover for the dryers. The dryers were evaluated to determine drying time and performance efficiencies, using Baobab leaves, Tomato and Okra slices as test crops. Collected data were analyzed using Statistical Analysis Software (SAS). The effects of variation of the independent factors were verified using Analysis of variance (ANOVA) at 1% and 5% levels of significant. Mean separation was carried out on significant factors using Duncan Multiple Range Test (DMRT). The results obtained showed the performance of the developed dryers, which indicates that drying time of mixed mode on-farm solar dryer stood at 56 hrs and 46 hrs while that of the indirect mode dryer was 76.67 hrs and 57 hrs and that of open sun drying was 154 hrs and 127 hrs for tomato and okra slices respectively. Results obtained showed that average system drying, energy collection and pick up efficiencies for the three test crops were 16.35%, 21.1% and 8.05% for mixed mode dryer respectively and 28.63%, 45.3% and 0.3% for indirect mode dryer, respectively. From the results obtained the mixed mode dryer dried all the products faster while indirect mode has superior energy efficiencies.

THE EFFECT OF THE FILLING RATIO ON THE OPERATING CHARACTERISTICS OF AN INDIRECT DRUM DRYER

This article investigates the effect of the filling ratio of the indirect rotary dryers on their operating characteristics. For moist biomass drying before combustion, the use of indirect drum dryers heated by a low pressure steam has proven to be highly suitable. Regarding the design of new dryers, it is necessary to experimentally verify the operating characteristics for specific materials and drying conditions. For this purpose, a set of experiments on a steam heated rotary drum dryer were carried out with green wood chips containing 60 to 66 wt% of moisture. The following operational characteristics of the dryer were experimentally determined: drying curves describing the process, square and volumetric evaporation capacities and drying heat consumptions. Based on the experimental results, the effect of various drum filling by dried material on the mentioned operating characteristics was analysed. On the one hand, higher drum filling ratio increases the drying time, on the other hand, the evaporation capacity also increases, while the specific energy consumption does not significantly alter. The maximum value of the evaporation capacity was reached when the drum was filled to 20 wt%. When the filling ratio was increased to 25 wt%, the evaporation capacity experienced almost no change.

Prednosti i nedostaci direktnog i indirektnog sušenja merkantilnog zrna i semena

The question again arises as to how to dry certain types of agricultural grain products and seeds. Should it be indirect or direct? The reason for this is the occasional fires that occur in dryers. It is often and unprofessionally stated that the cause of the fires is the use of a direct dryer. However, the causes of fires are multiple, and it is seldom due to the type of dryer. Two factors determine the differences between direct and indirect drying, and these are the nutritional and safety aspects. The ambition of this study is to clarify all the important differences between direct and indirect grain drying and to eliminate the established misconceptions on this issue. Drying of sunflower, oilseed rape and sorghum is especially delicate.

Analysis of Direct, Indirect and Hybrid Solar Dryer

Analysis of Direct, Indirect and Hybrid Solar Dryer

شبیه سازی نوری کلکتور بشقابی به وسیله دریافت کننده های استوانه ای و کروی بهینه شده با استفاده از نرم افزار TRACEPRO با شرایط بومی ایران برای خشک های خوردشیدی

This paper proposes the design and optical evaluation of a solar dish collector with changeable structure using TracePro software with native conditions of Iran for solar dryers. The designed dish concentrator has a diameter of 1.5m. TracePro's goal is to design and evaluate complex optical systems. Modeling a parabolic concentrator in TracePro can be achieved using several methods. All segments of dish collectors are made of glass (perfect parabolic mirror with a reflection coefficient of 95%). In the ray-tracing simulations, the two cavity receiver model (cylindrical and semi-sphere) is added to study the influence of physical parameters of the cavity. The simulation result shows that semi-spherical receiver is better and it has got better optical performance. Thereby it is highly recommended for various types of solar dryers such as direct drying (solar box dryer), or indirect drying (solar cabinet dryer).

An Engineered solar crop and meat dryer for rural Africa: A techno-economic outlook

This paper introduces a new solar crop dryer design for small scale entrepreneurs going into crop storage and marketing. It is an indirect drying system requiring 2 m2 ground space for installation of both the 2 m2 collector and the 1 m3 dryer chamber. Both collector and dryer are designed de-novo, and manufactured to give one assembly. The assembly is then analysed for heat and mass transfer using both TRNSYS and MATLAB software. For places with an equatorial climate, the system is predicted to be adequate for a start, with daily moisture removal limits of between 12 and 15 kg. This translates to a drying rate of about 20 kg/day wet produce from 75% to 12% moisture content. An economic analysis is done for two cases of direct manufacture and importation. In either case, it is found that breakeven is possible within the first one to two years of acquisition for high value products - in part because of the heavy crop and price losses currently experienced with sun drying. It is therefore concluded that the new product may not only be helpful in reducing food waste, but that it might also have economic viability to commercial entrepreneurs.

Sustainable Energy for Drying of Cashew Kernels – Experimental Research

Drying is an important process in food preservation. In cashew processing industries cashew kernels are dried for easy peeling of the thin brownish sticky layer known as testa. For this it is necessary to reduce the average moisture content of 13% to 5%. Drying is achieved by direct and indirect methods like traditional open sun and using conventional energy through dryers. Due to control of the air properties in indirect drying cashew kernels can be dried at faster rate and can retain their quality. Air flow passages also play an important role in drying process. The objective of the study is to investigate experimentally the energy consumption for drying 1 kg of cashew kernel using electrically assisted heating and to evaluate the feasibility of active solar air dryer for drying in cashew processing industries. An electrical heat-assisted dryer (EHD) and an active solar flat plate collector air dryer (ASAD) systems are designed and developed using locally available materials. Both the systems are tested for reduction in moisture content with series of experiments. EHD is tested with three different drying chambers for optimum drying rate. In its final test drying chamber without baffle plates has resulted in reduction in moisture content to required level by 5% in three hours with drying rate of 2.8 kg/h against 6.5% and 6.8% in single tray version and four trays with baffle plate version. The drying efficiency of drying chamber is found to be 30.54%. In ASAD system the experimental results ensure the drying of cashew kernels within stipulated time of 6 hours with drying rate of 1.66 kg/h and energy consumption of 255 kJ against 270 kJ of electrical heater drying. The drying chamber exhibits an efficiency of 50.89%. The study suggests that the design is feasible to small, cottage industries for cashew kernel drying. The energy savings up to 3750 kJ per day for a batch of 15 kg is possible.

Application Status of Co-Processing Municipal Sewage Sludge in Cement Kilns in China

Municipal sewage sludge (MSS) disposal is an urgent issue in China with the continuous growth of sewage treatment capacity. Among various disposal methods, co-processing of MSS in cement kilns has been one of the most promising disposal methods in recent years. The present situation of sewage treatment and sludge disposal, the development of co-processing MSS in a cement kiln, and main disposal routes in China were discussed in this study. The results indicated that China had paid considerable attention to the technology and released correlative policies in the past few years. There were about 35 co-processing projects built in China, all of which were limited by construction scale and pollutant emissions. Due to differences in construction methods and economic conditions, China’s co-processing projects mainly employed three routes—direct addition to a transition chamber, addition to a precalciner after direct thermal drying, and addition to a precalciner after indirect drying. Summarizing and analyzing the characteristics of MSS co-processing would facilitate its development in China and similar regions.

A Glance on Solar Drying Technology: A Review

Preservation of fruits, vegetables, and food are essential for keeping them for a long time without further deterioration in the quality of the product. In this review paper, the attention is given on different types of solar drying technologies. There are basically two types of solar drying methods viz, direct type and indirect type. In direct type solar radiations directly fall on the product which is in closed in cabinet and in case of indirect type drying of product can be done by natural or force method. Mixed mode solar drying method is combination of both direct and in direct type. Solar drying has been used to dry plants, seeds, fruits, meat, fish, wood, and other agricultural, forest products. In order to benefit from the free in recent years to develop solar drying mainly for preserving agricultural and forest products.

Design, development and CFD modeling of indirect solar food dryer

Abstract In this study, a solar powered indirect food dryer is designed and developed. The dryer design consists of a solar collector unit, drying chamber with two columns of four rack shelves, chimney for the exhaust air, and a solar powered fan. The outlet of the dryer is designed in a truncated pyramid geometry so that precipitation of condensed water would be minimized and additional heating of the drying air is possible at the exit. The dryer is developed and manufactured in Mekelle, Ethiopia. Computational Fluid Dynamics, CFD is employed for predicting a transient three dimensional flow field and temperature distribution within the drying chamber using a symmetric flow domain. The predicted air flow distribution in the vicinity of the rack shelves showed that the mean flow velocity is 0.14 m/sec for the lowest shelf and 0.12 m/sec for the other shelves due to cooling of the air. A significantly uniform airflow distribution is observed on the top three shelves compared to the bottom shelf. The inside of the drying chamber evolves towards a steady operating temperature of 315K. The temporal temperature distribution reveals that the food to be dried will evolve to this temperature in about 35 minutes. For validating the model, the temperature distribution on each rack shelf is measured along with the global solar irradiation. The maximum average temperature difference between the measurement and the CFD simulation is found to be 4.3 °C. Hence, the CFD model is able to produce a good qualitative and quantitative insight into the temperature distribution within the drying chamber, rack shelves, and symmetry plane.

Thermal performance amelioration of flat plate solar collector of an indirect dryer

Thermal performance amelioration of flat plate solar collector of an indirect dryer

Experimental investigation and numerical modeling of heat transfer during solar drying of carrot slices

The knowledge of heat transfer analysis during drying is critical for process design, quality control and energy saving. In this study, convective heat transfer coefficient, hc during solar drying of carrot slices was determined experimentally. Carrot slices of 0.03 m diameter and 0.005 m thickness were dried in laboratory scale natural convection direct, indirect and mixed mode solar dryers. It was observed that samples dried in mixed-mode solar dryer achieved higher values of $$ \overline{h_c} $$ (24.95 W/m2 °C) followed by indirect (15.80 W/m2 °C) and direct solar dryer (13.52 W/m2 °C). Heat transfer correlations were developed during drying of carrot slices in different dryers through standard dimensionless numbers in the form of an equation Nu = C(Ra)n. The results of uncertainty analysis in the $$ \overline{h_c} $$ was observed to be in the range of 0.073%–2.7%. A numerical 2D finite element model was developed to analyse the temperature distribution inside carrot slices during drying period by using COMSOL Multiphysics simulation program. The numerical results were compared against experimental data and the outcome suggested that the sample temperatures are in close agreement with the model predictions. Lower values of statistical parameters showed better acceptability of the simulation model for predicting solar drying behaviour of carrot slices.

Construction of an indirect solar dryer with a photovoltaic system and optimised speed control

With a radiant energy of 4.5 kWh/m2 (International Power Plant in Iran), Iran has a good potential for using solar thermal energy to dehumidify products in the agricultural and pharmaceutical industry. In fact, drying provides the possibility of restoring surplus products due to its longer shelf life, for future use. Indirect drying results are better results (nutrition and taste) than direct drying. Indirect solar dryer today works in many countries in industrial and lower levels of humidity and is quite satisfactory. It should be noted that the electronic and control system is embedded in data creation and air flow when necessary. The solar dryer is a device that performs the drying of different products with the use of renewable energies, in other words, performs dehumidifying operations without even using 1 W of electricity from the city.

Experimental Investigations on Electrical Heat Assisted Drying of Cashew Kernels

Drying is an important process in food preservation. In cashew processing industries cashew kernels are dried for easy peeling of the thin brownish sticky layer known as testa. The average moisture content of 13% of the cashew kernels needs to be reduced to 5% for proper peeling action. Drying can achieved either by traditional drying methods or through dryers. Due to control of the air properties in indirect drying cashew kernels can be dried at faster rate and can retain their quality. Air flow passage also plays an important role in drying process. The objective of the study is to investigate experimentally the feasibility of drying chamber for drying of cashew kernels using electrically assisted heating. An electrical heat assisted drying system is designed and developed using locally available materials. The system uses three different drying chambers that are designed and tested for optimum drying rate of cashew kernels in three separate experiments. Drying chamber without baffle plates has resulted in reduction in moisture content to required level by 5% in three hours with drying rate of 2.8 kg/h against 6.5% and 6.8% in single tray version and four trays with baffle plate version. The drying efficiency of drying chamber is found to be 30.54%.

Impact of postharvest processes on major phenolic constituents and antioxidant potentials of different Ocimum species

Tulsi (Ocimum sanctum Linn.) is one of the preferred herbs used as tea blended beverage in India. Ocimum is a rich source of antioxidants. The present study demonstrates the effect of post-harvest processes and blanching treatment on antioxidant potential of O. sanctum and seven other Ocimum species/cultivars. An optimized high performance liquid chromatographic method was applied to study the distribution of caffeic acid (CA) and rosmarinic acid (RA), and rutin (RU) in shed dried and blanched Ocimum leaves. Blanching treatments included thermal (Deep freeze- liq. N2, dry-hot air, and wet heat-boil H2O) and chemical methods (NaCl, NaHCO3, and CaOCl2). In general, blanching treatments have severely degraded the phenolic content of all Ocimum species. Only 77% increase in CA content of O. kilimandscharicum (OK) when treated with CaOCl2 was observed. Similarly, 14%, 18%, and 19% increase in RA content in the OK leaves were also observed when treated with boiling water, hot air, and CaOCl2, respectively. Shed drying process was found to be most appropriate to hold the antioxidant potential but compromised appearance. Blanching through a quick dip in wet-heat followed by indirect dry-heat drying reduced the loss of green colour. The present findings are useful to adopt the appropriate postharvest handling and pre-treatment of Ocimum for optimum retention of green colour appearance and their antioxidant potential.

Clinical study design for enzyme replacement therapy in acid ceramidase deficiency presenting as Farber disease, an ultra-rare condition with broad phenotypic heterogeneity

The scale-up of mechanical equipment such as agitators, solid blenders, indirect dryers, and other pieces of equipment requiring specialized knowledge almost always requires assistance from the supplier’s engineering staff or others outside the operating or engineering company doing the scale-up. However, it is very important for the designer to adequately communicate to the outside sources of knowledge what exactly the equipment is to perform. The purpose of this chapter is to provide examples of this type of equipment, point out why outside assistance may be necessary, and show how the engineer from the owner or engineering company can work with the supplier. Two specific examples have been chosen to illustrate these principles. The first example is an agitator/mixer scale-up. The other example is that of an indirect dryer.

Comparative approach to the performance of direct and indirect solar drying of sludge from sewage plants, experimental and theoretical evaluation

The objective of this work is to contribute to the enhancement of sludge of wastewater treatment plants and solar energy in Algeria. A kinetic comparison was made to the direct and indirect solar dryers operated with natural convection. Two models have been developed to simulate drying. Under natural conditions and at ambient temperatures below 32 °C, the indirect dryer gives high temperatures and efficiency compared to the direct dryer. Drying curves show that the higher the temperature is, the shorter drying time is and the faster drying speed is. From the drying curves, only the decreasing speed phase or slowdown (phase 2) is observed in the two types of drying, which is similar to results obtained in the literature with plant products. Solar dryers have reduced the time needed, a moisture reduction of 71% which increases the dryness of the mud from 14.47% to 85.53%. Thirteen mathematical models existing in the literature were tested and compared with the proposed models. The proposed models and the modified Henderson and Pabis model showed the best smoothing qualities of all indirect and direct dryer drying kinetics, with an advantage for the proposed models as they are dimensionless (independent models of units of measurement), they contain fewer parameters and verify the boundary conditions.

Integration of Biomass Indirect Dryers into Energy Systems

Integration of Biomass Indirect Dryers into Energy Systems