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AbstractTo elucidate the effects of energy input modes on energy efficiency and berry quality in continuous microwave drying, four energy input modes with variational working ways of magnetrons were investigated by using numerical simulation and bench experiments in a continuous microwave dryer. Energy efficiency was divided into absorption and conversion efficiency to study the change rule of drying process, and the retention rate of anthocyanins of berry’s representative nutrition ingredient was studied considering both of the temperature and its uniformity. Results indicate that the energy input modes affect the absorption efficiency by changing the distribution uniformity of electric field of material layer, and the conversion efficiency by altering the matching degree between the energy allocation and drying characteristics of berry, which are both determined by the ways of working magnetrons of different energy input modes. The conversion efficiency has a greater influence on the final energy efficiency, so the energy input mode should be paid attention to the provision of microwave energy by selecting proper way of working magnetrons according to the drying characteristics. The effect of temperature uniformity on anthocyanin degradation is more obvious with average temperature increasing gradually, where better uniformity of electric field strength should be provided to guarantee the quality of dried berry by adjusting the energy input mode. The research results provide significant insights to optimize the energy input mode of taking into account both the energy efficiency and dried quality of material. [ABSTRACT FROM AUTHOR]

This study validates the mechanism of ultrasonic dehydration without transition of water into vapor. The process can be realized by cavitation dispersion of liquid initiated by collapse of cavitation bubbles of cylindrical shape formed in capillaries. The developed mathematical model considers the complete life cycle of cavitation bubbles, encompassing three stages: slow growth, rapid expansion with deformation, and collapse. The optimum range of sound pressure level from 150 dB (critical level) to 170 (limit level) at which cavitation dispersion of liquid from capillaries takes place has been determined. The optimum sample size corresponding to the ultrasonic wavelength in gas, at which the dehydrated productivity is maximized, has been determined. The mechanism of ultrasonic dispersion of liquid during drying was confirmed by experiments. Practical implementation of ultrasonic drying of food products (carrots) confirmed effectiveness of implementation of dehydration mechanism and provided a reduction of drying time by 1.9 times with a reduction of power consumption by 1.7 times. [ABSTRACT FROM AUTHOR]

Spray drying of milk is a highly energy intensive process. In this study, thermodynamic and exergoeconomic analyses of two-stage spray drying plant have been executed. This plant was analyzed on the basis of various parameters such as energy efficiency, exergy efficiency, energy improvement potential, exergy improvement potential, etc. The energy and exergy efficiency of the plant were 72.90 and 35.15%, respectively. The maximum energy improvement potential was for drying whereas maximum exergy improvement potential was for homogenizer. It indicates huge scope in the technical improvement for drying chamber and homogenizer of the plant. The highest cost of processing was for cyclone separator (percentage relative cost difference: 44%) followed by drying chamber (percentage relative cost difference: 40.71%). Highest energy destroyed was calculated for drying chamber (195.83 kJ/kg) followed by VFBD (87.62 kJ/kg). Lowest energy efficiency was calculated for VFBD (34.64%) followed by drying chamber (50.04%). Highest energy improvement potential was estimated for drying chamber (97.86 kJ/kg). Highest relative energy destruction ratio was calculated for drying chamber (52.04%) followed by VFBD (23.30%). Highest energetic factor was calculated for drying chamber (28.22%) followed by homogenizer (16.71%). Based on these analyses, it was realized that performance of the spray drying plant may be substantially improved by some design improvement of drying chamber and homogenizer only. [ABSTRACT FROM AUTHOR]

Net power plant efficiency is the ratio of exportable electrical power output to the product of fuel consumption rate and fuel heating value. Conventionally, power plants are designed to attain the maximum net power plant efficiency by using regenerative feed water heating, in which extracted steam from steam turbine is used to increase feed water temperature. An important factor that determines the net power plant efficiency is the temperature of flue gas exhausted from the power plant. Decreasing this temperature increases the net power plant efficiency. However, exhaust flue gas temperature should not be lower than the lower limit in order to avoid the corrosion resulting from condensation of sulfuric acid vapor in flue gas on heat exchanger tubes. The lower limit can be raised by reducing fuel moisture content and raising air temperature at boiler inlet. In this paper, it is proposed that low-pressure extracted steam should be used for fuel drying in steam dryer, and vapor released from steam dryer should be used for air heating in heat recovery air preheater. By doing so, the lower limit of exhaust flue gas temperature is decreased, and the net efficiency of the power plant is increased. A case study of a 600-MW lignite-fired power plant is used to demonstrate that the integration of steam dryer and heat recovery air preheater is economically justified. [ABSTRACT FROM AUTHOR]

Leakage of air in tumble dryers is an important parameter regarding the energy efficiency of the drying process. In general, tumble dryers are prone to leakage, therefore further investigation and optimization in this field is of great interest. This study investigates and quantifies leakage of air within the closed-loop system of an in-situ household heat pump tumble dryer. Each potential leakage location was characterized by leakage curve obtained either by isolated or cumulative measurements using system pressurization method. Based on the static pressure distribution within the closed-loop system, the leakage outflow and inflow were quantified. The leakage of air at the rear and front drum seal was evaluated with and without drum movement. The results indicated the highest leakage outflow rate at the heat pump housing, which represents 12,6% of the total drying air flow rate within the closed-loop system. Sealing heat pump housing improved the condensation efficiency from B to A class according to the IEC 61121. [ABSTRACT FROM AUTHOR]

For a biomass power plant, which uses a biomass fuel having a high moisture content, flue gas drying is an effective method of increasing the overall power plant efficiency. However, this method requires flue gas that has a high temperature. Most biomass power plants, however, are designed so that flue gas temperature is already reduced to a low value through the installation of economizer and air heater. This paper investigates the use of steam-air preheater to raise both air temperature and flue gas temperature. Therefore, steam-air preheater enhances the potential of flue gas dryer, and both devices can be used in conjunction to raise the overall efficiency of a biomass power plant. Models of power plant, flue gas dryer, and steam-air preheater are used in this paper to demonstrate by simulation that the integration of flue gas dryer and steam-air preheater results in 2.52% increase in electrical power output of a reference power plant that consumes a fuel with 52% moisture content (wet-basis) if the fuel moisture removal rate in flue gas dryer is 7140 kg/h, and the total heating surface area of steam-air preheater is 2000 m2. The simple payback period for the investment in this integration is 3.3 years. [ABSTRACT FROM AUTHOR]

Citrus residue is a large-scale agro-industrial biowaste that can become a source of renewable energy through drying. Drying demands high power consumption due to the low energy efficiency of this process in the industries. In this work, the energy performance of the drying process in a semi-industrial rotary drum of 2.7 m length and 0.45 diameter was analyzed. The main objective was to find the operational condition for the lowest energy consumption and also the highest energy, drying and exergetic efficiencies. The experiments were performed under different solid mass flow rates (0.2 and 0.4 kg/min) inlet air velocities (1 and 2 m/s) and temperatures (135, 145, and 155 °C). The average energy efficiency was 13.1% with 25.1% of drying efficiency, 37291.3 kJ/kg of specific energy consumption, and 37.3% of exergy efficiency. The results showed that the drying technique can be an interesting alternative to add value to the citrus residue. [ABSTRACT FROM AUTHOR]

Residential clothes drying consume about 650 TBtu of primary energy per year in the United States, equivalent to 3% of primary residential energy consumption. There is a strong impetus to reduce the energy consumption of clothes dryers by both improving existing technology and developing alternatives that use fundamentally different drying mechanisms. Clothes drying technologies are broadly classified into either evaporative or mechanical drying. The focus of this paper is on mechanical drying, including vibrational, centrifugal, and press-based methods. In this work, the physical processes involved in these mechanical fabric drying processes were analyzed to develop general theories of mechanical cloth drying energy efficiency. Quantitative evaluation of the theories requires measured fabric properties. To accomplish this, a set of experiments was conducted on samples of a standard test fabric. The fabric was a cotton-polyester blend specified by the US Department of Energy to evaluate the standardized efficiency of all residential clothes dryers in the US. Mercury porosimetry experiments were conducted to determine the fabric pore size distribution, apparent density, and porosity. Elasticity experiments were conducted to determine the fabric's Young's modulus. Isostatic press experiments were conducted to establish a relationship between compression force and fabric moisture content. The data resulting from these experiments were combined with mathematical models developed in this work to calculate the theoretical maximum performance limits for mechanical drying of the standard fabric. The results of the analysis are used to make recommendations for the most promising technologies that offer the greatest potential energy savings for residential clothes drying. [ABSTRACT FROM AUTHOR]

In this work, the industrial case study of effluent drying with a direct and hybrid heat recovery configuration is investigated for the purpose of improving heat recovery potential and understanding the influence of various design parameters on the performance indicators in the spray drying process. Initially, data collection and performance analysis of industrial spray dryer of effluent management is performed. Then, the effect of design variables such as recirculation ratios, mass flow rate of dry hot air, water vapor, temperature of the mixing chamber, and heat input on performance parameters (thermal efficiency, energy savings, and the sustainability index) are evaluated for several configurations of the spray drying unit used in effluent management. As an outcome, substantial improvement in energy efficiency (83%) and energy-saving (26%) was achieved for a spray drying system with a 70% recirculation ratio of exhaust air for a hybrid heat recovery configuration, which is approximately 2.5% higher than the direct heat recovery configuration and it is significantly higher than that without an energy recovery system. In addition, a significant reduction in the blower power and heat input is noted in the direct and hybrid heat recovery system. The sustainability index is higher for the hybrid heat recovery configuration, indicating it being the most environment friendly configuration. The absolute humidity in the exhaust air is kept constant during entire investigation for uniformity in analysis. [ABSTRACT FROM AUTHOR]

Paper drying is the most energy-intensive step in papermaking and around 90% of the total amount of manufactured paper is produced in multi-cylinder dryers. A framework based on a physical model of multi-cylinder drying was developed to assess the effect of various energy-saving measures at a production site. The framework was applied to the drying section of a paper machine producing corrugated paper. The calculated steam and power savings reach up to 1.55 GJth/tpaper and 0.1 GJel/tpaper respectively, depending on the chosen combination of efficiency measures. The cumulative effect of the measures is not equal to the sum of their individual effects, which highlights the importance of accounting for interactions when considering the implementation of several measures. [ABSTRACT FROM AUTHOR]

Although DC power is claimed to be more energy-efficient than AC power for EHD drying, experimental studies on this subject are still insufficient. This research compares the efficiency of DC versus AC (60 Hz frequency) power for EHD drying by using 1 × 1 and 2 × 2 multi-pin discharge electrodes. Energy indicators were determined from the measurements of electric power consumption at the corresponding drying rate of the wet tissue paper. The experiments revealed the key benefits of DC drying, such as enhanced drying rate, higher energy efficiency, and lower specific energy consumption. For the comparable drying flux of 0.2 g/(m2 s), the specific energy consumption of DC drying was in the range from 350 J/g (2 × 2) to 750 J/g (1 × 1) as compared with 2000 J/g (2 × 2) to 5000 J/g (1 × 1) for AC. The specific energy consumption of a 2 × 2 discharge electrode was consistently smaller than the 1 × 1 one, indicating the role of emitters spacing in the process efficiency. The specific energy consumption of both electrodes increased with the drying rate. [ABSTRACT FROM AUTHOR]

This work investigates the evenness of fabric drying in a household heat pump tumble dryer. The evenness of drying was defined as the standard deviation of the fraction of water, evaporated from each fabric item. Drying experiments were performed according to the IEC 61121 standard, which was also followed to determine quantities and types of cotton fabric items (towels, pillowcases and sheets) within each load. Regression analysis was performed to develop models for evenness of drying as a function of load mass and drum speed. Similarities between the tumble dryer energy efficiency parameters and the evenness of drying were analyzed. A high level of agreement was determined between responses of energy efficiency, drying time and evenness of drying to changes in drum speed. Effects of load mass were however more complex and were reflected in a non-linear response of evenness of drying to changes in load mass – the best evenness of drying could be obtained at 2 kg load, followed by 6 kg and 4 kg load. Load composition was determined as an important factor affecting the evenness of drying. At larger loads, a sheet or a pillowcase in average contributed more to the un-evenness of drying than a towel. The presence of sheets and probably the ratio of sheets to other item types in the load were determined as the most probable factors that negatively affected the evenness of drying. [ABSTRACT FROM AUTHOR]

The current paper aims to find scientifically valid approaches to improving the environmental safety of technologies for drying grain materials and granular fertilizers. The methodology for environmental and economic efficiency justification of the energy-saving multi-stage shelf dryers with a convective fluidized bed drying provides design and operational parameters control. Meta-analysis of energy-effective and eco-friendly dryers based on the bibliometric method and the Scopus database is used for this study. The results showed that pollutants concentration in the exhausts could be controlled by modifying the design and the required number of shelves, ensuring the required material residence time to achieve the desired moisture content. The production of electricity using alternative resources like biogas and biofertilizer produced from the anaerobic digestate allows for achieving several Sustainable Development Goals simultaneously. The Goals in scope include Goal 6 Clean Water and Sanitation, Goal 7 Affordable and Clean Energy, Goal 9 Industry, Innovation and Infrastructure, Goal 12 Responsible Consumption and Production, Goal 13 Climate Action, and Goal 15 Life On Land. [ABSTRACT FROM AUTHOR]

The major limitation of the use of superheated steam spray drying (SHS-SD) for food products is the missing proof of its applicability for heat sensitive materials. A selection of food, in particular dairy products, were spray dried under superheated steam conditions in a lab scale spray dyer with an inlet steam temperature of 250 °C and outlet steam and product temperatures between 130 and 160 °C by pressure nozzle atomization. Powder attributes show that superheated steam spray drying of heat sensitive food products is technically feasible and does not necessarily result in major quality loss such as severe browning. [ABSTRACT FROM AUTHOR]

Clay drying is one of the most important steps in the construction materials industry. Due to its high-energy requirement, clay drying is one of the most energy-consuming processes contributing to greenhouse gas emissions, motivating the search for strategies to increase the energy efficiency of the process. The process involves several operating variables whose historical records can generate a large amount of data, which can be organized and analyzed efficiently using data mining techniques (DMT). In this paper, the performance variables of a material-industry rotary dryer were identified and analyzed. A cluster analysis was performed using the Ward's classification method with 1729 operating data, identifying the kind of materials processed and the operating configurations. A linear regression model was constructed using the RRELIEFF feature selection algorithm in Orange: Data Mining Toolbox in Python. The main thermal-energy-consumption variables were the production rate, power, inlet gas temperature, and product moisture delta. These four variables represent the dryer's specific energy consumption index ( I c ) more suitably than the classic Energy Vs Production model. Consequently, it was established that a global-aeration-factor reduction could improve the process efficiency by 7% to 10% at the average production rate. [ABSTRACT FROM AUTHOR]

Yerba mate is an herbal tea produced in the central part of South America. One of the main steps of the process is drying. Among the different types of dryers which are used at present, the double pass belt conveyer dryer is the most energy efficient. The increase in wood prizes used as fuel, has generated a demand from industrial producers to improve the thermal efficiency of the process. In order to do this, a numerical model of a double deck dryer of yerba mate has been developed to study the way of improving the energy efficiency and propose modifications to the present working conditions in industry. The good of fitness of the model was determined using experimental data from two industrial dryers. The results of the model were that using hot air at 100 °C and a solid mass flow rate of 4,000 kg/h, the energy efficiency was of 40.60%. Simulating the process at different drying conditions, it was found that the energy efficiency of the dryer could be improved by recirculating 15% of the exhaust air (63.70%), or drying at 120 °C and using a higher solids mass flow rate of 6,200 kg/h with an energy efficiency of 46.21%. [ABSTRACT FROM AUTHOR]

Pre-dried 2-phase olive pomace was dried until 8% moisture content of it by tray dryer. The effect of tray dryer's process conditions in terms of drying temperature (70–90 °C), air velocity (0.5–1.8 m/s), and sample thickness (0.5–1.5) on the quality of olive pomace and system energy efficiency were investigated. Moreover, tray dryer process parameters were optimized considering of minimum drying time, minimum quality loss of olive pomace, and maximum system energy efficiency. The optimum tray dryer conditions were 85.2 °C of drying temperature, 1.72 m/s of air velocity, and 0.5 cm of sample thickness as specified by using the Design Expert packaged software. The effects of drying temperature, air velocity, and sample thickness on the physical and chemical properties of dried 2-phase olive pomace (free fatty acid and specific absorption value [K232, K270]) and the system's energy efficiency (in terms of the moisture extraction rate and specific energy consumption) were examined. [ABSTRACT FROM AUTHOR]