Food Drying System Research Articles

Design and analysis of a floating photovoltaic based energy system with underground energy storage options for remote communities

Remote communities are highly dependent on transported food and fuel and require resilient energy systems. This study proposes a solar energy-based resilient system with energy storage options which is uniquely designed to generate electricity, heat, cooling, hydrogen and hence ammonia. Floating photovoltaic plant integrated with an anion exchange membrane electrolyser, pressure swing adsorption air separator with ammonia reactor and a heat pump. The underground energy storage options are pumped-hydro storage, high-grade heat storage, medium-grade heat storage and cold storage. The proposed system intends to exploit the infrastructure of abandoned mines with underground storage, as well as unutilized water surfaces with floating photovoltaic plant. Among the direct useful outputs of the system, agricultural activities and food production can be supported with a greenhouse heater, a food drying system and an ammonia fertilizer. The proposed system is then analyzed through the first and second laws of thermodynamics by using mass, energy, entropy and exergy balance equations. A time-dependent analysis with simulation is carried out to analyze each hour in terms of energy and exergy balances by considering commercially available component data as well as actual meteorological data. The proposed system with a 120 MWp floating PV plant and energy storage options, is determined to be sufficient to meet all of 51 GWhe/year non-thermal electrical, 23.8 GWhth/year heating, and 7.7 GWhth/year cooling loads for a community with 5320 people by exploiting unutilized natural bodies and abandoned mines. The pumped-hydro storage system has 67.24 % round trip energy efficiency, while the hydrogen-based energy storage option possesses 46.50 % round trip energy efficiency in a typical meteorological year under average conditions. The overall energy and exergy efficiencies of the overall system are found to be 15.9 % and 17.1 % on average.

Detailed analysis of mass transfer in solar food dryer with different methods

In this study, the mass transfer, effective diffusion coefficient (Deff), activation energy (Ea), and drying efficiency values of the product dried in the solar food drying system were experimentally investigated. It was determined that Deff values, Ea values, and drying efficiency values calculated with experimental data varied between 0.15 × 10−10 - 0.1 × 10−10 m2/s, between 21.6 and 15.9 kJ/mol, and between 51.8% and 15.9%, respectively. Mass transfer values in the drying system are modeled in detail with four different methods such as numerical analysis method (CFD), machine learning algorithms (ANN, SVM) and drying kinetics mathematical models (Newton, Page, Midilli and Küçük, Thompson). The root means square error (RMSE) error analysis method was used to determine the validation of the models. For mass transfer studies, the moisture content (MR) values of the 10 mm thick product were taken into account. The novelty of this study is that mass transfer, which is an important parameter for drying system design and product selection, is expressed by mathematical empirical equations, artificial intelligence methods, and numerical analysis methods. The mass transfer of the product is shown by numerical analysis simulation with moisture contours. The method that models the MR values with the least error (0.01 RMSE) is the SVM algorithm.

Numerical and experimental analysis of heat and mass transfer in the drying process of the solar drying system

Design in a solar food drying system is crucial for food drying performance. In order to make effective use of the sun, the use of air-heated solar collectors is gradually increasing in drying systems. Dryer room temperature and pressure distribution modelling is a very important factor for system design and product selection. In this study, the drying air speed, drying temperature, and product moisture content values of a solar drying system were numerically modelled in a time dependent manner. In numerical analysis, temperature and drying air velocity were defined as variable under initial and boundary conditions. Polynomial equations based on time obtained from drying room inlet temperature and drying air velocity data were used. The R2 values of these equations were calculated as 0.96 and 0.91, respectively. COMSOL multiphysics program was used for temperature values, drying air velocity, product moisture content values and drying chamber pressure values modelling. Depending on the position of the sun and the time, the drying chamber inlet temperature values and air velocity values have been change. During the drying process of the product, moisture content values, heat and mass transfer values, drying efficiency values, diffusion coefficient and activation energy values were examined. Experimental data and computed fluid dynamics analysis (CFD) data were compared. Using the CFD numerical analysis program, the drying room temperature, moisture content and air velocity values were modelled with mean absolute percent error (MAPE) of 5.34%, 3.74% and 6.30%, respectively.

Experimental investigation of a novel waste heat based food drying system

World Food Program reports that more than 821 million people are subjected to acute hunger despite sufficient amount of food being produced. One of the underlying reasons is the food wastage due to poor preservation techniques and the energy cost of the established processing methods. Drying techniques are an effective means for reducing post-harvest food loss. However, the existing industrial drying techniques consume 20–25% of the energy used in the food processing chain. A system that utilizes the waste heat recovered from a diesel engine exhaust flue gas is proposed and an initial prototype tested. The system requires no external energy to operate the drying process; hence no CO2 is generated as a result of this process. Furthermore, the entropy is reduced by 0.206 kJ/kg.K as the overall thermal efficiency increases by 8.46%. It is estimated that the payback period is in the range of 321 days. Drying experiments were conducted to assess the dried food quality of five different staple food products, i.e. potato, pumpkin, carrot, radish, and apple. The drying performance (moisture removal rate) and product quality (Color analysis and Vitamin C analysis) conformed to the current industry standard. The overall performance assessment suggests that the system has the potential to reduce current levels of emission in food drying process and could be a stepping stone towards the development of energy-efficient food preservation technique.

Design and numerical analysis of a hybrid geothermal PCM flat plate solar collector dryer for developing countries

Drying techniques reduce post-harvest food deterioration. However, conventional drying consumes 20–25% of the energy used in food processing industries. This work presents a detailed design and comprehensive numerical analysis of a hybrid geothermal-PCM flat plate solar collector, which is in effect a self-sustaining renewable energy food drying system. The applicability of the hybrid geothermal-solar dryer for developing countries with a significant underground geothermal temperature gradient is investigated. The performed numerical analysis promises high efficiency and effectivity of this near-zero hybrid energy technology. The proposed conceptual design assessed using the related mathematical model to assess the functional parameters of the hybrid geothermal PCM flat plate solar collector dryer. Numerical simulation showed that the efficiency of hybrid geothermal PA-FPSC is 20.5% higher than conventional flat plate solar collector when the mass flow rate is at 0.02 kg/s. Therefore, successful integration of this technology to the existing food processing industries of the developing countries could be a step towards the prevention of irreversible climate change achieving SDG 12 (sustainable development goals).

COMPUTATIONAL FLUID DYNAMIC ANALYSIS OF PRODUCT MOISTURE RATE’S IN THE SOLAR ENERGY DRYING SYSTEM

Bu çalışmada hava ısıtmalı güneş kollektörlü bir gıda kurutma sistemi tasarlanmıştır. Tasarlanan kurutma sisteminde elma kurutulmuştur. Kurutulan elma dilimlerinin nem içeriği (MCk), kuruma hızı (DR) ve nem oranı (MR) değerleri hesaplanmıştır. Deneylerde kurutulan elma dilimlerinin dehidrasyonu sayısal analiz programı ile simüle edilmiştir. Kurutma analizi için birebir ölçülerde model oluşturulmuştur. İlk durumda elma diliminin çapı 60mm, kalınlığı 14mm ve yüzey sıcaklığı 4°C dir. Kurutma havasının giriş sıcaklığı 56.4°C ve hava hızı 1.6m/s dir. Analiz sonucunda ele edilen kuruma hızı ve zamanı, nem içeriği ve sıcaklık değişimi verileri mevcut deneysel çalışmalar ile karşılaştırılmıştır. Simülasyon sonucu elde edilen değerler ile deneysel çalışmalar sonucu hesaplanan değerler benzerlik göstermiştir.

Modeling of Heat Transfer Coefficient in Solar Greenhouse Type Drying Systems

As a sustainable energy source, solar energy is used in many applications. A greenhouse type dryer, which is a food drying system, directly benefits from solar energy. Convective heat transfer coefficient (hc) is an important parameter in food drying systems, in terms of system design and performance. Many parameters and equations are used to determine hc. However, as it is difficult to manually process and analyze large amounts of data and different formulations, machine learning algorithms are preferred. In this study, natural and forced convective solar greenhouse type dryers were designed. In a solar greenhouse type dryer, grape is dried in natural (GDNC) and forced convection (GDFC). For convective heat transfer coefficient (hc), predictive models were created using a multilayer perceptron (MLP)—which has many uses in drying applications, as mentioned in the literature—and decision tree (DT), which has not been used before in food drying applications. The machine learning algorithms and results of the estimated models are compared in this study. Error analyses were performed to determine the accuracy rates of the obtained models. As a result, the hc value of the dried grape product in a natural convective solar greenhouse type dryer was 11.3% higher than that of the forced type. The DT algorithm was found to be a more successful model than the MLP algorithm in estimating hc values in HDFC according to Root Mean Square Error. (RMSE = 0.0903). On the contrary, the MLP algorithm was more successful than the DT algorithm in estimating hc values in GDNC (RMSE = 0.0815).

Investigation of Mass Transfer with Different Models in a Solar Energy Food-Drying System

In drying systems, the examination of the drying rate values of the food product in advance gives important information about the raw material to be dried. In this study, thin-layer drying behavior of apple slices in a convective solar dryer was investigated. The experiments were carried out at a drying air temperature of 46–63 °C and a drying air speed of 0.7–1.8 m/s. In order to determine the drying kinetics, the mass change of apple slices was recorded under all drying air conditions. The effects of drying air temperature and speed, drying speed of apple slices, dimensionless moisture content, were investigated. In a solar drying system, thermal efficiency, solar radiation and air velocity values were measured. The drying kinetics of 15-mm thick apple slices were examined for three days in the solar drying system. Using the decision tree algorithm, which is a machine learning algorithm, a predictive model was created for moisture rate in drying experiments and four linear equations were obtained. According to obtained equations, the collector in the drying system depends on the inlet–outlet temperature values, the drying room inlet–outlet temperature values, the drying room humidity values and air velocity values. Moisture rate data were applied to twelve different models and their performance was determined by root mean square error (RMSE) analysis. The mathematical model with the least error rate was (RMSE: 0.09) Midilli model. A comparison was made between these drying models in the literature and the model generated by the decision tree algorithm. According to the results of RMSE error analysis, it was shown that the model created with the decision tree algorithm predicted the moisture rate values with less error values RMSE: 0.03) than the Midilli model.

CFD analysis of a tube-in-tube heat exchanger to recover waste heat for food drying

Food waste is an alarming issue for the modern world. Drying is one of the oldest and easiest solutions for overcoming unnecessary food waste. However, most of the conventional drying consumes a significant amount of energy to remove water from food. On the other hand, there are many sources, which cause heat waste. Smart utilization of waste heat from sources including IC engine, turbine, brick kiln and something like those would be a great solution to the energy consumption problem of food drying. There is no systematic theoretical analysis of waste-heat-based food drying system available in the literature. In this study, a comprehensive transport model of drying system using engine’s exhaust waste heat has been simulated. Utilization of a small lab-scale IC engine exhaust results in reducing about 1137.15 kg of CO2 every year that would be produced from a conventional food dryer of the same capacity. In addition, low installation cost and payback period offer a promising rational solution of drying system. The proposed system is also capable of reducing entropy to an appreciable extent. Therefore, successful implementation of this proposed technique would offer a high-energy efficient, low-cost drying system along with ensuring a green environment.

Thermodynamic analysis of an oxy-hydrogen combustor supported solar and wind energy-based sustainable polygeneration system for remote locations

In this study, a solar and wind energy-based system integrated with H2O2 combustor is developed to produce fresh water from sea-water desalination, electricity, cooling, hydrogen, and oxygen as well as to provide food drying and domestic water heating. The main components of the proposed system contains concentrated solar power (CSP), wind turbine, Rankine cycle, multi stage flash (MSF) desalination unit, water electrolyzer, a refrigeration unit, a food drying system, oxy-hydrogen combustor, domestic water heater, as well as hydrogen and oxygen storage units. Furthermore, for continuous operation of the system during night time and in cloudy weather conditions, a thermal energy storage (TES) unit and oxy-hydrogen combustion unit are integrated to the system. Based on energy and exergy balances, performance assessment of the proposed system is conducted. Moreover, effects of various parameters such as solar irradiation, wind speed and ambient temperature on some of the outputs of the system are investigated. The results illustrate that the proposed system fulfills most of the remote community requirements in an efficient, environmentally benign and uninterrupted way. The obtained results for the reference case show that with installation of parabolic trough concentrators (PTCs) on an area of 111,728 m2, the plant produces net electrical power of approximately 11.4 MW, approximately 828 m3/day of freshwater, about 36 kg/s of hot air for food drying, about 31 kg/s of heated domestic water, approximately 920 kg/day of H2 and about 2.26 MW of cooling. The overall energy efficiency of the system is found to be 50%, while the exergy efficiency of the system is 34%. In addition, the energy and exergy efficiencies of single generation in which there is only electrical power output are approximately 15% and 16%, respectively.

Assessment of cost sources and improvement potentials of a ground-source heat pump food drying system through advanced exergoeconomic analysis method

Advanced exergoeconomic analysis, the so-called new exergetic approach combined with the economic analysis, is applied to a ground-source heap pump (GSHP) drying system in this study. The thermodynamic inefficiencies and cost performance of the system components are evaluated in parts. Moreover, the results of the advanced exergoeconomic analysis are compared to those of the conventional exergoeconomic analysis. The results show that total costs in the overall system are 4.008 $/h whereas 2.569 $/h of the total costs are avoidable. The avoidable investment costs are significantly lower than avoidable destruction costs. Advanced exergoeconomic analysis indicates that the most important system components are the drying duct and the condenser with respect to reducing the costs. It is possible to reduce 34.6% of the total costs by developing improvement strategies focused on the drying duct and the condenser. It may be concluded that the conventional exergoeconomic analysis is an effective approach to specify the components, in which costs are accumulated while the advanced exergoeconomic approach is essential to determine the cost sources and to develop cost effective improving strategies.

Performance Evaluation of a Dehumidifier Assisted Low Temperature Based Food Drying System

Low-temperature drying allows foods such as green leafy vegetables to be dried without losing the original color and texture. The system proposed in this paper consists of desiccant dehumidifier which removes the moisture from the air and increases its adsorption capacity. Airflow rate and regeneration temperature of the dehumidifier was controlled to ensure minimal damage to the food during the drying process in comparison with tray drying. Fenugreek green leaves were dried from an initial moisture content of 88.6 % to 5% (wb). The fenugreek dried with rotary desiccant bed dehumidifier has superior green color, flavour and maximum retention of various nutrients.

Low-temperature desiccant-based food drying system with airflow and temperature control

A new low-temperature food drying system with controlled airflow and temperature is presented. Low-temperature drying allows foods such as vegetables to be dried without losing the original color and texture. Existing low-temperature systems are slow, and it is difficult to obtain uniform product quality. The system proposed in this paper consists of an airflow control system to improve drying speed, and temperature control to ensure minimal damage to the food during the drying process in comparison with sun drying. Through experimental evaluation of the system, it is demonstrated that dried vegetables produced by this method retain their fresh color and high vitamin content.

612 デシカントを用いた低温吸湿食品乾燥システム開発と制御

612 デシカントを用いた低温吸湿食品乾燥システム開発と制御

Development of an Efficient Family Size Solar Dryer

Abstract Since the air heater is the most important component in a solar food drying system, improving its performance is desirable, especially when the space available for the dryer is limited and its cost is to be kept as low as possible. The solar system considered is the forced convection type, in which air is driven inside the heater by using a small suction fan of low power consumption. In this work, two configurations of air heaters were tested to increase heat gain without much increase in size or cost. This could be achieved by elongating the air path through the collector or by using two glass covers, between which the air is allowed to flow before it enters the heater. For both configurations, an inexpensive reflecting surface is used to increase heat input Experimental results show an average increase of daily energy input of 40% and 57% for the first and second heater, respectively. This, in turn, increases the thermal efficiency of both heaters. Although the second type is more efficient tha...

Thermal performance of a new solar air heater

A solar air heater, part of a food drying system using solar energy as a renewable energy source for heat, was developed and tested for several agricultural products (i.e., sultana grapes, green beans, sweet peppers, chilli peppers). Drying processes were conducted in the chamber with forced natural air heated partly by solar energy. Solar air heater performances were discussed along with estimates of energy efficiency of the system. The obtained results indicate that the present system is efficient and effective.