Dry System Research Articles

A physics‐constrained hybrid residual neural network for the prediction of moisture content in a closed‐cycle drying system

AbstractClosed‐cycle drying technology has the advantages of safety, energy saving, and environmental protection, and has a wide application prospect. Due to the multi‐physics and multi‐scale nature of heat/mass transfer in the closed‐cycle drying process, as well as the characteristics of drying medium circulation and energy integration, it is difficult to obtain the product moisture content prediction model in closed‐cycle process based on rigorous closed‐cycle drying process mechanism model. However, accurate monitoring of product moisture content in the closed‐cycle drying process is the key to improving drying quality and process optimization. Aiming at the challenges in predicting moisture content, this paper proposes a physics‐constrained hybrid residual neural network (PC‐HRNN) for soft sensor modelling within a designed closed‐cycle drying system. The characteristic of this proposed method lies in its effective fusion of physics, knowledge, and data. First, a hybrid residual neural network (HRNN) is constructed based on the integration of a physics model and a data‐driven model. The HRNN takes the knowledge from the physics model as its auxiliary features and learns the prediction residuals of the physics model through a neural network model. Then, a new loss function that takes into account physical laws is introduced into HPNN to standardize model training and improve the generalization performance of the model. The experimental results show that the PC‐HRNN model improves prediction accuracy and model robustness, reduces the demand for data, and demonstrates stronger extrapolation capabilities under limited data.

Energy contribution and loss of greenhouse-type drying chamber in multi-energy drying system: Heat distribution and exergy efficiency

In this paper, the relationship between the structural design of the greenhouse drying chamber and energy contribution and loss is discussed from the perspective of energy saving and system performance, and the rationality of their design is analysed based on the exergy efficiency. Taking the multi-energy drying system of kelp as an example, the airflow and temperature distributions of different greenhouse-type drying chambers were simulated and optimized by using the computational fluid dynamics (CFD) method, and the heat transfer and loss were analyzed. The results show that the optimized drying chamber has an increase of about 40% in The results show that the optimized drying chamber has an increase of about 40% in exergy efficiency and a reduction of about 37% in exergy damage. The average energy efficiency of the greenhouse-type drying chamber was more than 80% with a size of 5000×2500×2300 mm, a tilt angle of 22.5°, and fans of 7. In addition, the energy efficiency was negatively correlated with the temperature difference between the inlet and outlet and positively correlated with the ambient temperature. Despite the heat loss in the drying chamber, its contribution to the system's overall energy efficiency is significant.

Modernization of small-sized drying plant for searching optimal modes with thermovision control

The climatic features of the Murmansk region (low average annual temperature; insignificant number of sunny days) do not contribute to the effective use of natural methods of drying aquatic organisms and determine the use of artificial dehydration methods using appropriate equipment. The capabilities of ship fish processing complexes are limited; highly productive coastal fish processing plants are required to supply the population with fish products. The development and testing of new drying modes has been carried out using a small-sized drying unit UPOR-M2. In the course of the study, a drying unit modernization project has been developed, equipment has been selected (thermal imaging system; damper and fan control modules), the system has been modernized and a number of experiments has been conducted to determine the effectiveness of the work performed. The modernization of the drying unit has made it possible to increase the accuracy of the data obtained by 25 % (temperature), 20 % (relative humidity), 18 % (weight), to implement remote control of the processes and to ensure reliable operation of the drying system. Further research of different drying modes for aquatic organisms should include upgrading the air supply control system and improving communication equipment.

Validation of a Passive Solar Drying System Using Pineapple.

Wasted produce is a pertinent issue in agriculture, with billions of tons of produce going to waste even before it hits markets. Specifically, in Sub-Saharan Africa (SSA), nearly half of all produce is lost before market. To combat this, the Agricycle® passive solar drier was designed to provide a cost-effective method of drying fruit for preservation. Using a psychrometric chamber to simulate the SSA environment, vitamin C, total phenolic contents, and iron tests were conducted, along with microbial content determination, water content determination, dissolved solids testing, and color and microstructure analyses to validate passive solar drying, comparing the results to freeze-dried samples. Nutritional contents were comparable between fresh, freeze-dried, and solar-dried samples, with a loss in vitamin C (statistically significant), total phenolic contents, and dissolved solids during solar drying. The microbial analysis for solar-dried samples was below standard limits, and the water content in the solar-dried samples was ~10% w.b. (<20% w.b.) compared to ~3% w.b. of the freeze-dried samples. Although having comparable vitamin C, total phenolic contents, and iron values, freeze-dried and solar dried samples showed very different colors and microstructures based on colorimetry and SEM imaging. In conclusion, the Agricycle® passive solar drier is a promising alternative approach for food preservation.

Integrated solar dryer and distillation system with PCM and injection, powered by PVT panels and solar concentrator

This research introduces a novel hybrid system integrating solar drying, solar distillation, and photovoltaic thermal panels, aimed at drying agricultural products, producing clean drinking water, and conserving energy. The system enhances the drying air temperature using thermal energy storage materials and a solar dish concentrator connected to a hot water storage tank, ensuring continuous operation even after sunset. The solar distiller, equipped with energy storage materials and an air injection system, is integrated with an external condenser to condense water vapor before expulsion, thereby increasing freshwater productivity. The results revealed that the developed system achieved an accumulative freshwater productivity of 87.1 L per day. The rates of water removal from dried potato slices ranged from 0.18 to 0.91 kg/h between 8:00 am and 10:00 pm. Additionally, the system achieved a gain output ratio of 1.38, indicating a significant improvement in energy efficiency. This innovative system offers practical solutions to address energy and freshwater scarcity, especially in remote regions of the Middle East and North Africa (MENA) region, which are characterized by high solar irradiance. The implementation of such hybrid systems could contribute to sustainable development by reducing reliance on conventional energy sources and mitigating environmental pollution.

Investigation of the effects of coal properties, environmental conditions, and costs on coal drying method selection using multi-criteria decision-making method (AHP)

In this study, coal properties and environmental characteristics were investigated, and the most suitable coal drying method was determined for four different regions (Armutcuk, Afsin, Can, and Soma) where Türkiye's significant coal reserves are located, using the AHP method (Analytical Hierarchy Process). Installation and operating cost, drying rate, environmental risk, and land area parameters were used as selection criteria in the AHP method. After analyzing the physical and chemical properties of coals from four different regions, changes in moisture content and drying costs were calculated according to various drying methods (rotary, microwave, solar, and air). The results indicated that the solar energy data of the regions were determined to be 1315, 1610, 1400, and 1444 kWh/m²-year for Armutcuk, Afsin, Can, and Soma, respectively. Accordingly, solar energy drying systems are expected to be preferred in regions with high solar energy. However, with the effect of other selection criteria, it was determined that although the Can region receives less solar energy than the Soma region, the microwave drying method should be used for the coal of the Soma region, and the solar energy drying method should be used for the coal of Can region. Microwave and solar energy methods should be preferred for drying the coals of the Armutcuk and Afsin regions, respectively. As in many sectors, multi-criteria decision-making methods are necessary for optimum equipment/method selection in the mining sector. In conclusion, this study showed that the AHP method can be used when appropriate criteria are thoroughly determined.

Comparison of different solar dryers with and without heat storage for crop drying: A review

AbstractSolar drying systems have proven to be cost‐effective and environmentally friendly for drying various products. An extensive investigation of solar dryers with different designs, applications, and operating principles is conducted. Compared to direct drying, solar drying improves product quality by lowering moisture content without compromising the original product's qualities. Solar dryers are of two types: passive solar dryers and active solar dryers. Passive‐mode solar dryers circulate air through natural convection, whereas active ones circulate air through forced convection. Crop‐affected design characteristics include crop sensitivity, cost and time available to dry the crop, crop moisture content, the level of drying required, and so on. A wide range of research has been carried out on the thermal modeling of the dryer, using different designs. This article also discussed and compared the drying performance of three basic solar dryers: direct solar dryer, dryer with PVT air collection, and phase change materials (PCM). Even though PCM dryers are more expensive and uncommon, their ability to speed up drying at night makes them impactful.

The Application of Pinch Technology to a Novel Closed-Loop Spray Drying System with a Condenser and Reheater.

Spray drying is an energy-intensive process in industrial use, making energy recovery a critical focus for improving overall efficiency. This study investigates the potential of integrating heat-recovery systems, including an innovative air reheater, into a closed-loop spray-drying unit to maximise energy savings. Through detailed pinch analysis, the system achieved a very low approach temperature, averaging 3.48 K, which is significantly lower than that of conventional open-loop systems. The study quantifies the energy-recovery potential by demonstrating that the integration of heat-recovery components can reduce the external heating demand by up to 30%. This not only enhances heat-transfer efficiency but also lowers operational costs and reduces the system's environmental impact. The results suggest that closed-loop systems with air reheaters offer a scalable solution for improving energy efficiency across different industrial applications. The research highlights a new paradigm: focusing on latent energy within the system rather than adjusting individual operational variables.

Assessment of thermochemical, physicochemical, and biochemical properties of purple cabbage powder converted by different drying systems

Assessment of thermochemical, physicochemical, and biochemical properties of purple cabbage powder converted by different drying systems

Non-invasive ultrasonic sensing of internal conditions on a partial full-scale spent nuclear fuel canister mock-up

The safe storage of spent nuclear fuel (SNF) in dry cask storage systems (DCSSs) is critical to the nuclear fuel cycle and the future of nuclear energy. A critical component of DCSSs is the SNF canister. The canister is a sealed stainless-steel structure, which is first vacuum dried and then backfilled with helium. The structural deterioration within a canister can be monitored through its internal gas properties. This monitoring serves as the driving force behind the non-invasive ultrasonic sensing approach in this paper. A major challenge in collecting gas-borne signals using ultrasonic sensing is the impedance mismatch between the stainless-steel canister and the helium gas inside. Only a small fraction of the ultrasonic signal makes its way from the transmitter to the receiver through the gas medium. In this paper, experimental studies on a partial full-scale canister mock-up were carried out to capture the gas-borne signals. Damping materials were applied on the outside, and blocking and unblocking tests were conducted to identify the gas-borne signal. The research results showed that the excitation frequency played an important role in maximizing the gas-borne signals. The gas-borne signal was successfully detected at around the theoretical time-of-flight (TOF) at 225 kHz. A high signal-to-noise ratio (SNR) was achieved in the measurements. Next, acoustic impedance matching (AIM) layers were added, and it was found that the gas signal energy was improved by 160.4% compared with that of no AIM layers. Subsequently, the relative humidity (RH) level and temperature of the gas were varied to simulate abnormal internal conditions of the canister. The non-invasive testing system demonstrated reliability and sensitivity in detecting gas temperature and RH variations. Theoretical calculations demonstrated the potential for detecting low-level xenon and air within an actual SNF canister filled with helium. Last, an active noise cancellation (ANC) method, previously developed by the authors, was verified on the canister mock-up for the first time. The results showed that the SNR of the gas signal was improved by 213.6% compared with that of no ANC.

Application of artificial intelligence to predict energy consumption and thermal efficiency of hybrid convection-radiation dryer for garlic slices

This study aims to examine the energy-related aspects of a hybrid convection-radiation drying technique employed in the drying process of garlic slices. Several factors, including infrared radiation intensity (1500, 2000, and 3000 W/m2), air temperature (40, 50, and 60 °C), and airflow rates of the drying chamber (0.7, 1.0, and 1.5 m/s) were evaluated to optimize the responses of drying time (min), energy consumption (kJ), thermal efficiency (%), and specific energy consumption (MJ/kg). Furthermore, an Artificial Neural Network model was employed to predict the effects of the parameters above on the drying system's specific energy consumption, energy consumption, drying time, and thermal efficiency. The obtained data were analyzed using a self-organizing map and principal component analysis. Interestingly, the findings showed that increasing the air temperature and infrared radiation intensity led to shorter drying times, while higher airflow rates resulted in longer drying durations. Additionally, it was found that higher infrared intensity and air temperature, combined with lower airflow rates, improved the energy indices. Increasing the air velocity to 1.0 and 1.5 m/s at the same air temperature and radiation intensity resulted in a considerable increase in drying time by 9 and 22.7%, respectively. The lowest efficiency value of 10.1% was observed at 40 °C temperature and an air velocity of 1.5 m/s. The Artificial Neural Network model demonstrated high accuracy with a Root Mean Square Error of 0.05 and an overall accuracy of (95%) in predicting the drying parameters. Notably, the self-organizing map visualization revealed that higher air temperatures and radiation corresponded to lower drying times, energy consumption, and specific energy consumption. Conversely, higher airflow rates resulted in increased drying time and energy consumption. The present study suggested that 60 °C, 3000 W/m2 and 0.7 m/s are optimum conditions for efficiently drying garlic slices under the hybrid dryer. This investigation addresses the limitations and deficiencies of previous work on energy optimization and efficiency analysis of garlic under a hybrid dryer with infrared heating systems. Further studies on the economic feasibility of applying such a system for sample drying and the impact of drying on the thermal behaviors of the products need additional investigation.

Tomato dry farming as an agroecological model for California’s drought resilient future: Farmers’ perspectives and experiences

Small, diversified farms on California’s Central Coast have been dry farming for decades, allowing farmers to use water stored in soils from winter rains to grow tomatoes and other vegetables with little-to-no irrigation in summers without rainfall. As recent water shortages in California have forced a reckoning with the precariousness of the state’s water supply, policy groups and the general public have become increasingly interested in dry farming as a promising means of achieving water conservation goals. Academic research on this practice, however, has been scarce. Amid growing urgency to develop low-water agricultural systems in the state, we interviewed 10 Central Coast dry farmers, representing over half of the commercial dry farm operations in the region where this practice was developed, to collaboratively answer 2 central research questions: (1) What business and land stewardship practices characterize successful tomato dry farming on California’s Central Coast? (2) What is the potential for dry farming to expand beyond its current adoption while maintaining its identity as a diversified practice that benefits small-scale operations? We summarize farmers’ wisdom into 9 themes about current dry farm practice, its potential for expansion and future opportunities. We also synthesize farmer-stated environmental constraints on dry farm feasibility into a map of suitable areas in California. As we consider how dry farming might expand to new areas and operations, we highlight dry farming’s history as an agroecological alternative to industrial farming in the region and the need for careful policy planning to maintain that identity. In examining this California Central Coast dry farming system, we ask if and how it can enhance the viability of nonindustrial farming operations as the food system adapts to less water availability. Because policies that encourage dry farm expansion could change economic landscapes in which dry farming operates, we caution that well-intentioned policies could edge small growers out of dry farm markets if not carefully designed. At the same time, we emphasize the opportunity for dry farm tomato systems to model an agroecological transition toward water savings in California.

Vertical Connectors in Ancient Monuments: Documentation and Experimental Study of the Behaviour of Iron and Titanium Connectors

ABSTRACT Ancient monuments are constructed following the dry construction system. Large dimensional structural members, with perfectly plane interfaces, are placed without mortar. Two types of iron connectors, vertical and horizontal, used to connect individual stone blocks, are activated in case of relative displacements, e.g. earthquakes. The paper focuses on, iron or titanium, vertical connectors, crossing the interfaces between successive stone courses, and investigates their seismic behaviour. In situ and bibliographical documentation of vertical connections in ancient Greek monuments, including their topology, dimensions, and typical pathology attributed to them, served as a basis for the design of an experimental program. First, specimens simulating the original connections are tested under monotonic and cyclic actions. The behaviour of those connections, effectuated using iron vertical connectors, having confirmed the pathology observed in situ, i.e. fracture of the substrate, an alternative connection was tested aiming at avoiding or significantly delaying the failure of the substrate (marble). An unbonded length was provided to the connector, close to the interface, to postpone the contact between the connector and the marble. The test results confirmed the anticipated change of behaviour, associated though with smaller shear resistance and larger displacements at its attainment than for the original connections.

Thermodynamic and economic analysis of a solar-assisted ejector-enhanced flash tank vapor injection heat pump cycle with dual evaporators

This paper proposes a solar-assisted ejector-enhanced flash tank vapor injection heat pump cycle with dual evaporators (SEFVIC), designed for heat pump drying application. Compared to the standard flash tank vapor injection heat pump cycle (FVIC), the SEFVIC uses an additional high-temperature evaporator to further minimize irreversible losses during the heat transfer process. Moreover, it integrates solar energy to improve the drying quality and heating capacity of the cycle. Meanwhile, the introduction of an ejector improves the system's performance by reducing throttling loss. The advantages of SEFVIC over FVIC are evaluated using theoretical models based on the first and second laws of thermodynamics. Results show that SEFVIC reveals a 34.1 % improvement in the heating coefficient of performance and a 192.8 % enhancement in volumetric heating capacity compared to FVIC under typical operating condition. Notably, SEFVIC maintains superior performance even at lower evaporating temperatures. Moreover, exergy research indicates that 77.1 % of the total exergy destruction in SEFVIC is attributed to the solar collector. Economic analysis indicates that the integration of solar energy into the SEFVIC is economically beneficial. These findings highlight the prospective application of SEFVIC and guide combining the multi-temperature heat pump drying system and auxiliary solar source.

Performance study of the rapid heating drying system based on the reverse Brayton air cycle for agricultural application

Air temperature and humidity control are important for crop storage. Current drying methods in agriculture include solar heating and air source heat pumps, whereas solar heating may lead to poor quality of the dried product and air source heat pumps may not reach the desired temperature when the environment is harsh. In this paper, a rapid heating and drying system based on reverse Brayton air circulation is proposed to obtain high temperature and low humidity air quickly by adjusting the pressure ratio to achieve an adjustable crop drying process. An improved rapid heating and drying system with a water cooler is also proposed to increase the drying efficiency of the system. The results show that the total dehumidification rate of the improved system can reach 11.51 g/s, which is 1.48 g/s higher than that of the rapid heating and drying system without a water cooler, and the dehumidification energy efficiency of the improved system can reach 1.26 kg/(kW.h), which is 0.11 kg/(kW.h) higher than that of the rapid heating and drying system without a water-cooling device.

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.

Optical characterization and thermal performance of a novel solar dryer with dynamic control of solar radiation

In this study, a novel adaptive solar dryer with a coating of polymer-dispersed liquid crystals (PDLC) was designed, built, and characterized to evaluate its optical properties and thermal performance by modulating the transmission of solar radiation toward the drying chamber. PDLC films can electrically switch between opaque and transparent states, making them ideal for controlling solar radiation. Unlike conventional direct dryers, the proposed solar drying system takes advantage of direct solar radiation, known for its rapid drying process, while minimizing the impact on product properties. The results show that the PDLC coating exhibited a significant difference in transmittance between the “on” and “off” states under ambient conditions. At 400 nm, the transmittance varied by 20 %, increasing to 30 % at 450 nm. The solar dryer with dynamic control of solar irradiance constantly maintained a temperature range of 52.19 °C–57 °C. Lower relative humidity values were achieved compared to the uncontrolled solar dryer, resulting in a uniform irradiance distribution within the drying cabinet. The solar dryer with dynamic control of solar irradiance (acrylic and PDLC film) presents a total thermal resistance (0.02817 mK/W) exhibiting better heat permanence inside the drying cabinet compared to polycarbonate (one of the materials most used for drying systems). The system's thermal efficiency ensures reliable operation regardless of weather conditions, efficiently capturing and converting solar energy into heat.

A Universal Biocompatible and Multifunctional Solid Electrolyte in p-Type and n-Type Organic Electrochemical Transistors for Complementary Circuits and Bioelectronic Interfaces.

The development of soft and flexible devices for collection of bioelectrical signals is gaining momentum for wearable and implantable applications. Among these devices, organic electrochemical transistors (OECTs) stand out due to their low operating voltage and large signal amplification capable of transducing weak biological signals. While liquid electrolytes have demonstrated efficacy in OECTs, they limit its operating temperature and pose challenges for electronic packaging due to potential leakage. Conversely, solid electrolytes offer advantages such as mechanical flexibility, robustness against environmental factors, and ability to bridge the interface between rigid dry electronics systems and soft wet biological tissues. However, few systems have demonstrated generality and compatibility with a wide range of state-of-the-art organic mixed ionic-electronic conductors (OMIECs). This paper introduces a highly stretchable, flexible, biocompatible, self-healable gelatin-based solid-state electrolyte, compatible with both p- and n-type OMIEC channels while maintaining high performance and excellent stability. Furthermore, this nonvolatile electrolyte is stable up to 120°C and exhibits high ionic conductivity even in dry environment. Additionally, an OECT-based complementary inverter with a record-high normalized-gain of 228 V-1 and a corresponding ultralow static power consumption of 1 nW is demonstrated. These advancements pave the way for versatile applications ranging from bioelectronics to power-efficient implants.

Evacuated Tube Solar Collector-Based Drying System: Analytical Modeling, Influencing Factors, and Recent Progress in Drying of Agri-Commodities

Evacuated Tube Solar Collector-Based Drying System: Analytical Modeling, Influencing Factors, and Recent Progress in Drying of Agri-Commodities

A novel weight index-based uniform partition technique of multi-dimensional probability space for structural uncertainty quantification

Accurately and efficiently achieving the uncertainty quantification of engineering structures is a challenging issue. The direct probability integral method (DPIM) provides an effective pathway to address this issue. However, the key partition technique via Voronoi cell of DPIM requires a prohibitive computational burden for multi-dimensional probability space. Moreover, due to the distributed nonuniformity of representative points, the accuracy of DPIM with the partition technique via Voronoi cell (DPIM-Voronoi) for obtaining the response probability density function (PDF) of structures with multi-dimensional probability space still needs to be improved. To this end, a novel weight index-based uniform partition technique is proposed in this study. This technique can generate uniformly distributed representative points and calculate their assigned probabilities using the weight indexes of representative regions. This feature ensures that the representative points can fill the probability space in a highly uniform manner, and avoid the resource-consuming calculation process of assigned probability by Monte Carlo simulation in the original partition technique via Voronoi cell. Based on the proposed technique, DPIM with a Weight index-based Uniform partition technique (DPIM-WU) is developed. Compared to DPIM-Voronoi, the advantages of DPIM-WU include: (1) improving the computational accuracy of response PDF for structures with multi-dimensional probability space, especially in the tail region, leading to improved accuracy of the dynamic reliability; (2) remarkably reducing the computational cost, with minimal computer memory required for the partition process of multi-dimensional probability space; (3) enhancing the robustness to the number of representative points. These advantages are verified through the stochastic response and dynamic reliability analyses of four typical examples, including the 5-story buildings, dry friction system, cylinder structure, and adjacent buildings with pounding motion. Notably, in the stochastic pounding response analysis of adjacent buildings, a stochastic P-bifurcation occurs as the coefficient of variation of the structural parameters decreases.