Hot Heating Research Articles

Effects of Conveyor Movement, Layer Rearrangement and Sample Mixing on Pest Mortality in Milled Rice Subjected to Radio Frequency Heating

Highlights Hot air-assisted RF heating accelerated temperature rise of samples. Thermal holding after RF heating improved heating uniformity and pest mortality. Layer rearrangement, conveyor movement, and mixing enhanced RF heating efficiency. Abstract. Application ofradio frequency (RF) treatment has been studied for disinfesting agricultural products, and RF heating non-uniformity has been demonstrated to directly influence pest mortality in treated products. The purpose of this study was to investigate the combined effects of holding time after conveyor movement, layer rearrangement, and sample mixing on the mortality of Rhyzopertha dominica (R. dominica) in milled rice treated with hot air-assisted RF heating. Results showed that hot-air assistance during the process of RF heating can lead to a rapid temperature rise and improve the temperature distribution. RF heating followed by holding samples in hot air for specific time periods effectively improved the heating uniformity of samples and raised the mortality of R. dominica in milled rice. Compared with the stationary conditions, conveyor movement, layer rearrangement, and sample mixing improved the hot air-assisted RF heating uniformity of the sample, raised pest mortality and reduced the thermal holding time after RF treatment required to achieve 100% pest mortality in milled rice. The findings of this study provide a valuable proof of concept for improving RF heating uniformity and optimizing parameters in RF disinfestation protocols for milled rice. Keywords: Heating uniformity, Milled rice, Mixing, Pest mortality, Radio frequency heating.

Development of an Integrated Solar-Biomass Energy System for Near-Zero Energy Buildings: A Technical and Environmental Study

The present study aims to satisfy the energy demands of a set of Norwegian residential structures with the least carbon dioxide and most renewable energy. Real-time data on building domestic hot water (DHW), heating, and electricity usage is used to plan and expand the renewable energy supply side. PVT panels provide DHW and electricity in the hybrid solar and biomass energy system. Heat is produced by the digester and heat pump. Also used is a twofold effect absorption refrigeration system for cooling. Rule-based regulation manages heat streams and redirects flows on the supply side. We provide the plant's size and execute the dynamic energy simulation. Electricity and biomass expenses determine building heating. The system is then tuned for operational conditions and compared to the design point. PVT may generate over 80% of annual DHW. Summertime radiation is more intense and can be turned into cooling energy, therefore 64.8% of cooling output comes from it. Digester/CC heats 66.55% of the structure, suggesting designers use biomass in winter due to increased energy costs. A parametric analysis shows that increasing PVT duration and tank size affects efficiency and emissions differently. Cost, efficiency, and emission index at TOPSIS are 9.73 $/hr, 36.8%, and 7.75 kg/MWh, according to optimization findings.

Developing a Quality Control System in a Continuous Hot Air Heating Process in Surimi Seafood Processing Using Image Analysis and Artificial Intelligence

In this study, the feasibility of classifying surimi gels during a continuous heating process using an artificial intelligence (AI) algorithm on labeled images was investigated. Surimi paste with varying corn starch concentrations (0%, 5%, and 10%) and moisture content levels (78% and 80%) from Alaska pollock were analyzed for the subtle physical changes. Rheological characterization and K-means clustering analysis performed on entire images captured from different batches of heated surimi gel indicated a four-stage transformation from its initial state to gel formation with the temperature ranges spanning 25 to <40 °C, 40 to <50 °C, 50 to <55 °C, and 55 to 80 °C. Subsequently, a Convolutional Neural Network (CNN) model based on the temperature classification was designed to interpret and classify these images. A total of 1000 to 1200 images were used for the training, testing, and validation purposes in the ratio 7:1:2. The CNN architecture incorporated essential elements including an input layer, convolutional layers, rectified linear unit (ReLU) activation functions, normalization layers, and max-pooling layers. The CNN model achieved validation accuracy >92.67% for individual mixture composition, 94.53% for classifying surimi samples based on moisture content, and gelation level, and 89.73% for complex classifications involving moisture content, starch concentration, and gelation stages. Additionally, it exhibited high average precision, recall, and F1 scores (>0.92), indicating precision and sensitivity in identifying relevant instances. The success of CNN in non-destructively classifying surimi gels with different moisture and starch contents is demonstrated in this work.

Building archetype characterization for mass-housing energy efficiency through a UBEM approach

Building archetypes characterization is one of the main sources of inaccuracy in Urban Building Energy Modelling (UBEM). This study aims to implement an effective approach to developing a building archetype for estimating energy efficiency in social housing districts. The goal is to support researchers and decision-makers analyzing strategies for similar buildings, evaluate energy use in buildings, and design different retrofit scenarios. UBEM is a practical approach in large-scale building energy modeling used by researchers and stakeholders to analyze and develop different design and retrofit scenarios for buildings with similar construction features and occupancy. The archetype approach requires a subset of buildings representing a cluster with similar properties (e.g., building type, construction features, occupancy, and age), which is used to extrapolate the total energy consumption at the urban scale. The research focused on clusters of four in-line multi-story building types in Rome to conceptualize the study, characterized by reinforced concrete structures. The most diffused systems are the traditional building systems using a gas boiler and radiators for domestic hot water and heating. The model was implemented following a UBEM approach, relying on Urban Modeling Interface (UMI), a tool allowing the creation of building templates to evaluate their energy use at neighbourhood and city-scale. The overall results obtained in this study are described to characterize the archetype for the mass-housing building that researchers and administrations can use to evaluate different strategies for buildings with similar characteristics.

Changes in the physical and mechanical properties of Pinus taeda and Eucalyptus bosistoana wood modified by contact charring

Physical and mechanical properties were evaluated for all-sided charred Pinus taeda and Eucalyptus bosistoana wood by hot plate contact heating system followed by treatment with linseed oil. The water absorption, volumetric swelling, wettability, hardness, modulus of rupture, and modulus of elasticity in bending strength and compression strength parallel to grain were determined. The water absorption and volumetric swell were determined after immersion in water, as measured at various intervals of water immersion up to 120 h. The results suggested that the contact charring process with the addition of a linseed oil application improved water absorption and volumetric swell properties of charred specimens compared to un-charred controls. Hardness of the charred wood decreased by 38% and 43% in P. taeda and E. bosistoana specimens, respectively, compared with their respective controls. The highest reductions were seen in modulus of elasticity and compression strength values in charred P. taeda specimens, while modulus of rupture (MOR) values decreased more in charred E. bosistoana specimens than in charred P. taeda specimens. These results suggested that charring of P. taeda and E. bosistoana wood does improve the moisture-related characteristics; however, their mechanical behavior and hardness decreased.

Thermal and structural response of a pavement solar collector prototype

Thermal and structural response of a pavement solar collector prototype

Experimental investigation, modeling and in-situ monitoring of a gas-driven absorption heat pump in Belgium

This work describes the methodology used to realize a performance analysis of an ammonia-water condensing gas absorption heat pump. This heat pump shows a nominal heating output of 18,9 kW for an outdoor temperature of 7 °C and a delivery temperature of 35 °C, and it is designed for domestic hot water and heating production. The experimental results obtained in the laboratory are contrasted with those obtained from the monitoring of two residential facilities in the northern part of Belgium. Experimental tests were carried out in a climatic chamber to emulate different outdoor climatic conditions based on a combination of the EN 12309 requirements and typical Belgium weather data. Measurements of gas consumption, electrical consumption, water flows, and temperatures were collected to compute performance indicators. On the other hand, the monitoring data was analyzed and contrasted with the experimental results to evaluate the field systems’ performance; the problems found and modifications made are described and discussed. The results show that the performance of the systems is highly dependent on the coupling with other appliances, on the operating conditions and control of the system, resulting in penalties that can be considerable depending on the configuration used. An empirical model calibrated with experimental data is proposed, as well as a penalization factor calibrated with the monitoring data. The results presented evidence the differences found between the studied facilities, highlighting the main role of proper installation and control not to diminish the main performance indicators.

Verification of rice quality during storage after drying with hot air and radio frequency heating

The objectives of the study were to observe the milling and cooking qualities of paddy rice dried with hot air (HA) and hot air and radio frequency heating (HA/RF) at 38 °C and 42 °C, and to observe these qualities after 6 months of storage under average temperature and RH of 28.4 °C and 70%, respectively. During storage, the average moisture content of paddy rice decreased from 13.66% to 11.37% in HA, 13.66% to 11.40% in HA/RF38, and 13.58% to 11.63 in HA/RF42. The milling qualities of rice were affected by the RF heating temperature and storage period. Rice dried with HA/RF38 and HA/RF42 could be safely stored for up to 5 months and 4 months, respectively, with satisfactory fissure percentage and head rice yield. The whiteness index significantly increased from 63.37 ± 0.58 to 64.46 ± 0.75 at HA, 62.78 ± 0.97 to 63.75 ± 1.55 at HA/RF38, and 62.77 ± 1.90 to 64.45 ± 0.95 at HA/RF42 during storage. For cooking qualities, elongation ratio (ER) was affected by RF and storage period, while texture profiles and pasting properties were only affected by storage period. The ER increased from month 3, by 10%, 11%, and 11% in HA, HA/RF38, and HA/RF42. The hardness of cooked rice reached its peak value between months 4–5. However, adhesiveness decreased as the storage period increased. The peak viscosity and setback increased with increasing storage period while breakdown conversely decreased. This study showed that hot air drying and RF heating temperatures of 38 °C could replace hot air drying without undesirable changes in milling and cooking properties during storage up to 5 months. Therefore, this is a promising drying technology for the rice milling industry.

Experimental test of a building thermal system for preventive maintenance based on thermoeconomic analysis

An analysis of the sectorial structure of energy consumption shows that residential and tertiary sector buildings are the third-highest consumers, responsible for 29.5% of a city’s final energy consumption. The Building Quality Control Laboratory of the Basque Government aims to promote quality, innovation, and sustainability in buildings. To accomplish this goal, it has constructed an experimental facility with different energy generation technologies and a very versatile control system for testing different energy systems and operation modes. In this study, we tested a facility for supplying domestic hot water and heating for a multi-family house by means of a condensing boiler and an aerothermal heat pump (together with the corresponding control). This installation could reproduce the thermal demands required to be satisfied by the generation equipment through a programmed operation of the installation based on real demands. Additionally, this installation was analyzed using thermoeconomics (TE) to solve problems unable to be solved using traditional energy analyses based on the First Law of Thermodynamics. These problems include: (1) Determining the costs of the products of the installation based on physical criteria, (2) detecting the places where losses actually occur, evaluating their costs, and proposing cost-effective improvements, and (3) diagnosing issues in the installation. As a result, this paper suggests a solution to the preventive maintenance problems confronting the technical maintenance personnel for thermal installations in buildings by applying TE knowledge and using real data collected from sensors.

Study on the influencing factors of thermal performance of radiant heating floor with the intensive solar irradiation

Radiant floor heating systems are widely used in buildings due to their great thermal comfort and energy-saving potential. In a building with many transparent envelopes, radiant floor units in some zones are usually irradiated by solar radiation, leading to overheating near the local floor surface. In order to quickly evaluate the heating performance of the radiant floor with the influence of solar radiation, a simplified model based on the thermal resistance network is established in this paper. Through derivation, the solar radiation effect coefficient (SREC) and the basic surface temperature are proposed, and then the floor surface temperature can be obtained from these two parameters. After experimental validation of this simplified method, the importance analyses of various factors affecting the SREC and the basic surface temperature are carried out, and the influence of each factor is summarized quantitatively. The results show that the pipe spacing has the greatest effect on the SREC, while the supply water temperature has the greatest effect on the basic surface temperature of the radiant floor. Moreover, the absorbed solar radiation intensity corresponding to the floor surface temperature equaling to the supply water temperature and the hot water stopping heating is defined as the critical value. As the temperature difference between the supply water and the indoor environment increases from 17 °C to 37 °C, the critical solar radiation intensity also increases from 180 W/m2 to 445 W/m2. If the absorbed solar radiation intensity is less than this critical value, increasing the pipe spacing, choosing a smaller pipe size, increasing the equivalent thickness and reducing the thermal conductivity of the radiant floor can all reduce the surface temperature of the radiant floor with the influence of solar radiation. The results of this study can put forward corresponding suggestions for the design and operation of the radiant floor to balance the cooperative heating relationship between the solar radiation and the heating system.

Low cost energy-efficient preheating of battery module integrated with air cooling based on a heat spreader plate

Integration of heating and cooling functions has aroused increasing interest for the automotive battery modules. The proposed cylindrical 18650 battery module is equipped with an external sleeved spreader plate (SHSP), which features low thermal resistance and a large exchange area as an efficient heat transfer medium. The transient temperature characteristics of the battery module were experimentally investigated in both cooling mode and heating mode, respectively. In cooling mode, the temperature characteristics of the battery module equipped with SHSP were examined. With an inlet velocity of 1 m/s and a discharge rate of 3 C, the temperature rise and temperature difference are only 12.9 °C and 2.83 °C at an ambient temperature of 25 °C, respectively. In heating mode, the heat-up characteristics of the battery module were experimentally examined at a subzero temperature of −20 °C under three different heating protocols: continuous heating, fast-rest-slow heating, and slow-rest-fast heating. Immune from potential effects on the battery internal degradation, the heating rate of the battery module in a continuous heating protocol could reach 6.98 °C/min with a heating efficiency of 69.8%, which outperforms the existing external heating modes.Additionally, the fast-rest-slow heating protocol has clear-cut advantages in terms of heating rate while maintaining a smaller temperature difference during the heating phase. Finally, a simplified thermal resistance network model for the cell is established based on the analysis of the one-dimensional steady state heat transfer. According to projections, the thermal resistance of the present heating model is 2.03 K/W, which is less than the hot air convection heating model by 5.24 K/W. The proposed method exhibits excellent performance and provides a low-cost, highly efficient design solution for the battery module under varying conditions.

Laser Heating Method for an Alkali Metal Atomic Cell with Heat Transfer Enhancement

Alkali metal atomic cells are crucial components of atomic instruments, such as atomic magnetometers, atomic gyroscopes, and atomic clocks. A highly uniform and stable heating structure can ensure the stability of the alkali metal atom density. The vapor cell of an atomic magnetometer that uses laser heating has no magnetic field interference and ease of miniaturization, making it superior to hot air heating and AC electric heating. However, the current laser heating structure suffers from low heating efficiency and uneven temperature distribution inside the vapor cell. In this paper, we designed a non-magnetic heating structure based on the laser heating principle. We studied the temperature distribution of the heating structure using the finite element method (FEM) and analyzed the conversion and transfer of laser energy. We found that the heat conduction between the vapor cell and the heating chips (colored filters) is poor, resulting in uneven temperature distribution and low heating efficiency in the vapor cell. Therefore, the addition of graphite film to the four surfaces of the vapor cell was an important improvement. This addition helped to balance the temperature distribution and improve the conduction efficiency of the heating structure. It was measured that the power of the heating laser remained unchanged. After the addition of the graphite film, the temperature difference coefficient (CVT) used to evaluate the internal temperature uniformity of the vapor cell was reduced from 0.1308 to 0.0426. This research paper is crucial for improving the heating efficiency of the non-magnetic heating structure and the temperature uniformity of the vapor cell.

Application Research of PVT in Solar House R-CELLS

The application of PVT (Photovoltaic-thermal) technology is discussed based on R-CELLS, which is a zero-energy solar energy house at Solar Decathlon China 2021. Combined with the actual data, the simulation model of the PVT system, which supplies domestic hot water and heating bathroom, is established in TRNSYS, and the performance evaluation of the whole year and heating season and economic analysis of the whole life cycle is carried out at the same time. Comparing and analyzing the system with or without auxiliary heating in the water tank, the simulation results show that the annual average electrical efficiency of the system is 15.35% and 15.52%, the annual average thermal efficiency is 3.36% and 9.52%, and the payback period is 13.87 years and 12.12 years. By increasing the number of PVT panels, 4 PVT panels can achieve zero energy consumption of the system, and the payback period of the PVT system can be reduced to 6.5 years after continuing to increase. The small-scale PVT system is systematically analyzed based on a case, and the importance of water tank auxiliary heating design and supply-demand matching design in the PVT energy supply system is found through data comparison, which has reference significance for the promotion of PVT building energy supply system in the future.

Study on hot air heating characteristics of greenhouse in cold region

Agriculture is the main industry in northeast China. As an important part of facility agriculture, agricultural greenhouses are playing a more and more important role. Due to geographical location, Northeast China is cold in winter, and the solar radiation energy is less, therefore, the large-span greenhouses commonly used in northeast China are prone to uneven temperature and insufficient heating. In this paper, in order to solve the phenomenon of uneven air flow field, humidity field and temperature field in greenhouse, based on AIRPAK simulation, four kinds of hot air heating return air modes, such as upper air supply and lower air return mode, lower air supply and upper air return mode, two-side air supply mode and left air supply and right air return mode, we explored the influence of temperature field, humidity field and air flow field in greenhouse. The results showed that the heat load of the greenhouse in winter is 161.51 kW, using two-side air supply mode is the best way. The air supply wind speed is 1.6 m/s, and the return wind speed is 3.1 m/s. The environment of the greenhouse can be maintained at about 15°C day and night, and the relative humidity is relatively uniform. In the crop growing area, the wind speed is between 0 m/s and 0.25 m/s. According to this research, suitable crops can be selected for reasonable planting and distribution in the greenhouse to maximize productivity.

Effect of Hot Air Heating on The Cavity Temperature Distribution of Injection Mold

In this paper, the air-assisted mold temperature control (AMTC) is applied for heating the mold in the injection molding process. The simulation is run with the same boundary conditions in the experiment. The results shows that the AMTC can heat the surface mold plate to 171.6 °C. This temperature value is higher than the glass transition temperature of almost thermoplastic materials that used in the injection molding process. With the product thickness values of 0.1 mm, 0.3 mm and 0.5 mm, the heating rates were 6.3 °C/s, 6.39 °C/s and 6.58 °C/s, respectively. The increase in heating rate can be explained by the need for thermal energy to heat up the stamp volume that is inserted in the mold cavity for changing the product thickness. Also, the highest temperature at the top of the stamp which is nearest to the hot air gate, and the temperature is smaller when the area is far from the hot air gate.

Simultaneous Effects of Hot Steam Injection and Surface Heating through an Embedded Channel of Steam Turbine Cascade

One of the challenges of turbines in the last stages is the condensation of the water droplets of the steam flow; resisting against the droplets condensation could be one of the negative effects of the presence of droplets in the flow. The presence of droplets leads to erosion and damage to the blade as well as losses and efficiency drop in the turbine. Surface heating and hot steam injection are approaches suggested for solving the problem of droplets condensation; in the present study, a channel embedded in the turbine blade has been used to solve the problem of condensation. This is a step forward for making the hot steam injection and the blade surface heating practical. To prevent the condensation effects in the steam turbine cascade, two methods have been, simultaneously, utilized: surface heating and hot steam injection in a 3D study. As a result of applying the two heating methods mentioned, Er, Lr, and Wr decreased by 28.2%, 31.3%, and 61.5%, respectively. Moreover, the kinetic energy (one of the most important parameters in the turbine nozzle application) has increased by 0.35%. The results show a more surface temperature transfer on the blade's suction side.

Numerical and Experimental Analysis of a Prototypical Thermoelectric Generator Dedicated to Wood-Fired Heating Stove.

The typical operating range of domestic heating devices includes only heat generation. However, the availability of combined heat and power generation in microscale devices is currently becoming a more and more interesting option. This paper shows the experimental and numerical analysis of the possibility of developing a micro-cogeneration system equipped with a wood-fired heating stove and a prototype of the thermoelectric generator equipped with low-price thermoelectric modules. In the first step, mathematical modeling made it possible to analyze different configurations of the hot side of the thermoelectric generator (computational fluid dynamics was used). Next, experiments have been conducted on the prototypical test rig. The maximum power obtained during the discussed combustion process was 15.9 We when the flue gas temperature was approximately 623 K. Assuming a case, when such value of generated power occurred during the whole main phase, the energy generated would be at a level of approximately 33.1 Whe, while the heat transferred to the water would be approximately 1 078.0 Whth. In addition to the technical aspects, the economic premises of the proposed solution were analyzed. As was shown, an installation of TEG to the existing stove is economically not viable: the Simply Payback Time will be approximately 28.9-66.1 years depending on the analyzed scenario. On the other hand, the SPBT would be significantly shorter, when the installation of the stove with an integrated thermoelectric generator was considered (approximately 5.4 years). However, it should be noted that the introduction of the power generating system to a heat source can provide fully or partially network-independent operation of the hot water and heating systems.

RECUPERAREA ENERGIEI TERMICE SOLARĂ ȘI A ENERGIEI TERMICE DIN PROCESUL DE COMPOSTARE

The use of energies from renewable sources, as an alternative to those obtained from fossil fuels, represents a sustained concern in the world scientific environment, this action being a particularly important objective at present, especially in the context of increasingly acute manifestations of the effects of climate change. The recovery and use of thermal energy developed in the composting process of biodegradable and solar waste is a current concern of the research environment in the field. In this paper we want to present some research on the recovery of thermal energy from the two renewable energy sources mentioned in order to use thermal energy for the production of the agent that can be used in the current activity of individual agricultural and livestock farms as well as in households, for the preparation of domestic hot water and heating of living spaces, greenhouses, and solariums. The paper presents the current state of research, some theoretical considerations regarding the thermodynamic phenomena that occur in the thermal energy recovery process, a modulated system for the recovery of thermal energy from the composting process and solar energy, experimentation in real operating conditions, the results and their interpretation and related conclusions.

ANALISIS TEMPERATUR PELAT LANDASAN HOT-GAS WELDING DAN BENTUK BEVEL TERHADAP KEKUATAN TARIK LASAN HDPE

Welding has developed rapidly at this time, both for metallic and non-metallic materials, one of the methods used for plastic welding is Hot-Gas Welding. Plastic is a very difficult material to weld due to its low thermal conductivity. The quality of the mechanical properties of the existing plastic welded joints is not close to the strength of plastic objects without welding. The purpose of this study was to determine the effect of variations in the temperature of the base plate and variations in the shape of the bevel during the Hot-Gas Welding process on the tensile strength of HDPE sheet welded joints, to determine the conditions of the interaction between variations in the temperature of the base plate and variations in the shape of the bevel during the Hot-Gas Welding process. HDPE sheet welded joints that produce maximum tensile strength values. In this study, two independent variables were used, namely the base plate temperature (30,70,110,150 C), variations in bevel shape (V, X, U) and three controlled variables which included HDPE plastic material with a thickness of 5mm, using added filler material in the form of HDPE plastic with a diameter of 4 mm and a hot gun airflow heating temperature of 250℃. The tensile test standard uses the ASTM D 638-03 standard and for data processing is done by DOE factorial, as supporting data macrostructural photos of each weld joint are carried out. The results showed that the maximum tensile strength of HDPE welded joints was obtained at the temperature of the base plate of 150°C and the V bevel shape with a value of 18.46 MPa or 84.22% of the parent material

Postharvest blanching and drying of industrial hemp (Cannabis sativa L.) with infrared and hot air heating for enhanced processing efficiency and microbial inactivation

Postharvest blanching and drying of industrial hemp (Cannabis sativa L.) by infrared (IR) and hot air (HA) heating was studied. Experiments were conducted at different IR heating times (1 and 2 min) and HA temperatures (65 and 85 °C) and compared with conventional indoor drying. Drying time was decreased from 3366 min (conventional) to as low as 222 min (85 °C HA). IR and HA processing reduced the total aerobic bacteria, and total yeast/mold levels by up to 0.81 and 1.85 log CFU/g, respectively from their initial levels of 4.63 and 4.75 log CFU/g, meanwhile reduced the activities of polyphenol oxidase and peroxidase by up to 91.7% and 66.7%, respectively. More than 96.1% total cannabidiol was preserved by thermal processing. Total terpene retention ranged from 18.3% to 71.1% under tested conditions with distinct terpene profiles. The results provide important information on the microbial safety and a timely solution to improve the postharvest processes of hemp.