Plate Heat Research Articles

Modelling and implementation of an in-situ thermally regenerated adsorption module for removing gaseous xylene

The technology of in-situ thermally regenerated air purifiers (TRAP) can effectively recover adsorbents’ adsorption capacity, which is promising for low-concentration uncontinuous waste gas treatments in light pollution industries, such as furniture industries and tire factories. This study aims to provide a design model for the adsorption behaviours of the TRAP module under various practical situations in the furniture industry. We propose a dimensionless parameter (the Number of Mass Transfer Units, NTUm) to predict the one-pass efficiency. A TRAP module consisting of multiple flexible and thin adsorption boards was developed to validate the model experimentally. The polluted air with xylene flows through the module and is adsorbed by the boards. When the adsorption boards are saturated, the heating plate will be electrically heated to about 80 °C, releasing xylene from the boards and regenerating their adsorption performance. The modelling results agree with the experimental results., which indicate that the NTUm is a crucial and helpful parameter in enhancing the efficiency of the TRAP module.

Broadband phase-modulated metasurface based on vanadium dioxide patches in microwave band

Phase-modulated metasurfaces (PMMs) have attracted considerable attention because of their widespread application in many fields. However, the most existing PMMs are only available in a relatively narrow band. In this paper, we propose a design of a broadband PMM based on vanadium dioxide (VO2) patches. The unit cell of the proposed PMM is composed of a surface layer supported by a 0.5 mm F4B with a dielectric constant of εr = 2.65, and a dielectric layer with a metal ground on its back. The surface layer consists of two opposite T-shaped metal patches connected by a VO2 patch. The VO2 patch can be used as an active element due to the insulator-to-metal transition of VO2. The process of phase transition is achieved by direct heating with a heating plate, without additional feeders affecting the performance of the PMM. The designed PMM can achieve a broadband phase difference within 180° ± 37° from 6.94 to 20.84 GHz, with a fractional bandwidth of 100%. Both full wave simulation and measurement results show that the proposed metasurface presents a good phase reconstruction performance over a wideband frequency range.

Experimental Results of a 10/40 kW-Class Reversible Solid Oxide Cell Demonstration System at Forschungszentrum Jülich

In 2018, a 5/15 kWDC reversible solid oxide cell system was developed and successfully operated by Forschungszentrum Jülich. Based on the knowledge gained with this first system, an optimized system in the power class of 10/40 kWAC was developed afterwards in 2019 that uses the well-established Integrated Module. This module consists of four 20-layer sub-stacks, two heat exchangers and five heating plates. It represents the main components of the system. The basic system layout was retained in general from the previous system and adjusted in accordance with the higher power level, as well as the supporting balance of plant components. The layout of the demonstrator system and its results are described. During the experimental evaluation in fuel cell mode, the system could provide an electrical output power from 1.7 to 13 kWAC. The maximum system efficiency of 63.3% based on the lower heating value (LHV) could be reached at a system power of 10.4 kWAC. This operating point was also analyzed regarding the temperature distribution in the stack and efficiency losses. In electrolysis mode, a maximum efficiency of 71.1% (LHV) was achieved with an electrical power input of −49.6 kWAC. At this operating point, about 11.7 Nm3 h−1 of hydrogen are generated. The stack temperature distribution and the efficiency losses are also analyzed for the electrolysis mode. Finally, the potential for the efficiency optimization through higher heat integration in this mode is experimentally evaluated and discussed.

Design of a Bean Sprouts Device by Soilless Automatic Cultivation

In order to solve problems: the existing household bean sprouts cultivation device is relatively simple; bean sprouts are easy to be contaminated in the open cultivation tank which affects the quality of bean sprouts, and the automation is poor. The bean sprouts device by soilless automatic cultivation adopts cylindrical closed culture bin structure, and the temperature and humidity sensor is set in the culture bin, which can monitor the environment in real time. At the same time, the heating plate, fan and humidifier are set in the culture bin to heat up, cool down and humidify the environment, so as to realize automatic bean sprouts cultivation. The prototype test showed that: at the temperature 26°C-30°C, humidity 85%-95%, the diameter of mung bean sprouts can reach 2.5mm, and the height can reach 150mm. the diameter of yellow bean sprouts can reach 3mm, and the height can reach 160mm. The average yield of the two sprouts was 98%. The device has the advantages of soilless, intelligence, miniaturization and simple operation, which can meet the requirements of automatic bean sprouts cultivation. It is a necessary product for household in the future.

Heat and mass transfer at the ignition of single and double gas hydrate powder flow in a reactor

This paper details the heat and mass transfer at the ignition patterns of single (methane) and double (methane-isopropanol) granulated hydrates in a heated air. The experiments were performed in a laboratory-scale combustion chamber in the form of an oblong reactor with free-falling powder of the gas hydrate granules. The air in the combustion chamber was heated by the walls with ceramic plate heaters. The variation ranges of the input parameters were chosen to match the capacities of modern energy generation systems. We established the ignition delay times of the gas hydrate granules, combustion regimes, and sizes of the flame zone behind moving granules. We also analyzed the joint influence of the gas hydrate granules on their ignition behavior. A model was developed to estimate the threshold boundary conditions of gas hydrate ignition in different-sized chambers, with variable hydrate component composition granule size. Gas hydrate dissociation rates were determined in different sections of the laboratory-scale combustion chamber. Thermal conditions were predicted in which gas hydrates consistently ignite in combustion chambers with minimum cooling of the chamber walls and minimum unburnt fuel.

Numerical simulation of thermo‐solid coupling under the condition of unidirectional heating of underground coal gasification overlying rock

AbstractIn order to study the variation law of temperature and stress of overlying rock under the thermal solid coupling condition of underground coal gasification (UCG), the coal measure sandstone samples were heated in one direction, the variation law of temperature and thermal stress was analyzed, and the experiment was analyzed using the numerical simulation software COMSOL. The temperature field, stress field, and volume strain distribution of rock mass are obtained. The results show that in the heating stage of the heating plate, the temperature curve of each measuring point changes rapidly and the temperature rises rapidly, and due to the decrease of the heating rate of the heating plate, the change rate of thermal stress tends to decrease. In the circumferential region of the lower end face, stress stretching occurs and the radial strain is the largest. Under the constraint of unidirectional heating, the temperature distribution of rock along the height direction is obvious. The principal stress is mainly concentrated near the lower end face of the specimen. The research results are helpful to study the thermal damage and fracture characteristics of overlying sandstone of UCG from the perspective of thermal solid coupling.

Experimental study of falling film evaporation on a vertical plate

In this paper, an experimental study is conducted on the evaporation of a film of water. The liquid film falls along the wall of a vertical plate and is exposed to a uniform heat flux density. We chose a metal plate with practical dimensions to obtain a system easy-to-use. We used a grid of 32 thermistors (NTC) to track the temperature evolution on the plate, which is heated uniformly and homogeneously by a silicone-coated copper heating plate. The system is insulated, and numerous precautions have been taken to avoid heat loss at the plate's edges and back to ensure complete heat transfer between the heating plate and the metal plate. The results show that the temperature is higher for systems with greater heat flux density q and a lower mass flow rate Γ0. It was found that the increase of imposed heat flux density q leads to an increase in the evaporation phenomenon; for example, with a heat flux density of 2200 W/m2, the system evaporation efficiency is 54 %, and 39 % for a mass flow rate of Γ0 = 2 Kg/h.m and Γ0 = 3 Kg/h.m respectively.

Design and spraying-preparation of the gradient coatings with various diameters and contents of SiO2 nano-particles for the enhanced anti-impact and thermal insulation performance

Composites used in aircraft are vulnerable to mechanical and thermal damage during particle impact at high speeds. In this paper, a series of gradient polyurethane silica coatings with different silica particle sizes and concentration gradients were prepared on epoxy resin matrix composites by pneumatic spraying process. The results of corundum impact and thermal insulation performance experiments indicated that multi-layer gradient coatings improved the particle impact resistance and thermal insulation. The damage was reduced to <1 % of surface damage area and thickness loss under the protection of enhanced gradient coatings, showing excellent particle impact resistance. Under unidirectional heating conditions, the temperature difference between the heating plate and the sample surface was four times that of the unprotected sample, from 2.2 °C to 9.4 °C, and the total thermal conductivity of the protected sample was reduced by 91.73 %. The coatings remained intact under high-speed particle collision of 300 A plasma flow, which verified the protection performance of the coatings simulating the situation that the coatings were impacted by particles and heated simultaneously. The as-prepared gradient coatings can effectively enhance the anti-impact and thermal insulation performance of composites, exhibiting wide application prospects.

Experimental investigation of convective heat transfer in the aircraft cabin environment at low air pressure

The heat transfer capacity of the cabin environment under low air pressure is significantly different from that under normal pressure. The existing research on the low-pressure environment of aircraft cabins has not provided a reliable convective heat transfer correlation to guide the design of the cabin thermal environment. This investigation evaluated the heat transfer in an actual aircraft cabin under different pressures. A laboratory test was designed in a cabin mockup with controllable boundary conditions for air temperature and pressure. Based on the measurement results, the quantitative effects of low pressure on the convective heat transfer coefficient (CHTC) of the heating surface were analyzed. According to the experimental results, the CHTC of the horizontal surface in natural convection increased from 3.26 W/(m2·K) to 5.10 W/(m2·K) when the heat flux increased from 100 W/m2 to 400 W/m2, and the CHTC dropped by 23–30% when the pressure dropped from 101 kPa to 61 kPa. With the same heat flux, the average CHTC value for the vertical plate was slightly lower than that for the horizontal heating plate under normal pressure, and the trend became significant as the air pressure decreased. In general, the average CHTC for forced convection was substantially higher than that for natural convection. Consequently, correlation equations for calculating natural and forced convection on horizontal and vertical plates under low air pressure were proposed, which will aid the design of the cabin thermal environment.

Experimental and LBM simulation study on the bubble dynamic behaviors in subcooled flow boiling

Bubble dynamic behavior is a fundamental issue in comprehending flow boiling process. In this paper, the bubble characteristics are studied in depth through experiment in conjunction with the Lattice Boltzmann method (LBM). Firstly, the visualized experiment in rectangular channels with double heating plates is performed during subcooled flow boiling. High-speed camera is employed to directly capture the macroscopic bubble dynamic behaviors under different working conditions. Furthermore, LBM model with a novel hybrid boundary scheme is developed to investigate mesoscopic bubble characteristics, including contact diameter, microlayer thickness profile and superheated layer thickness. The bubble diameter from LBM model is compared to experimental data with a mean relative error of 10.8%. The results of the current research find that the bubbles nucleating on the inside channel have smaller contact diameter ratio and larger inclined angle. Finally, combining macroscopic experiments and mesoscopic LBM studies, a model of the bubble growth rate is proposed for predicting bubble growth behavior. In the process of model development, three aspects for deciding the bubble growth rate are considered, including microlayer evaporation, heat diffusion from the superheated liquid layer, and condensation at bubble dome caused by subcooled flow boiling. The prediction model agrees well with the experimental results, with a mean relative error of 14.7%. The established bubble growth model will help to predict the heat transfer process during flow boiling.

Simultaneous densitometric determination of β-sitosterol and lupeol through validated HPTLC method in different plant parts of Uraria picta (Jacq.) Desv. ex DC. – A dashmool species

Abstractβ-sitosterol (BS) and lupeol (LU) exhibit a number of biological activities and are the important bioactive marker compounds in pharmaceutical science. In the present study, a simple, precise, accurate and validated high performance thin layer chromatographic (HPTLC) method was developed for simultaneous quantification of these two compounds in leaves, stem and roots of Uraria picta, a critically endangered medicinal plant and one of the important constituents of ten plants ayurvedic formulation called Dashmoola. Standards and test samples were applied on TLC aluminum plate precoated with 0.2 mm layer of silica gel 60F254. The plate was run in a twin glass chamber comprising toluene: methanol: chloroform (8:1:1, v/v/v) as a mobile phase. The plates were immersed in anisaldehyde-sulfuric reagent and then heated at 105 °C for 5 min in CAMAG TLC plate heater for appearance of bands. Densitometric scanning was performed at λmax = 525 nm using tungsten light source in CAMAG TLC Scanner4 armed with WinCATS software. RF values of BS and LU standards and those of test samples were found to be 0.53 ± 0.01 and 0.63 ± 0.01 respectively. The method was further validated by following the International Conference of Harmonization (ICH) guidelines. For BS and LU, the linear regression data for the calibration plots revealed a satisfactory linear association with r2 = 0.995 and 0.998, respectively. Linear range for both BS and LU was 200–600 ng/band. Accuracy of the method was evaluated by performing recovery study at three different levels by standard addition methods with an average recovery of 99.86% and 101.07%. The results revealed that the leaf samples of U. picta contained highest concentration of BS (0.150 ± 0.02%) while its root samples confined the highest concentration of LU (0.149 ± 0.01%). The developed method can be applied for routine and quality control analysis in different herbal formulations containing U. picta species.

Modification of Microcontroller-Based Batik Canting as A Temperature and Viscosity Control of Night Wax

The leakage of the wax during the casting of the candle using conventional canting hampers the process of making batik, especially coloring, thereby damaging the motif and reducing the quality of written batik. The solution given is related to the problem of leakage of night wax through E-Canting which is modified from conventional canting using an Arduino nano microcontroller, connected to a temperature sensor, heater plate, and servo to facilitate batik craftsmen in waxing. The use of a microcontroller connected to a temperature sensor to maintain a stable temperature and viscosity of the night wax with the process of releasing the wax is regulated using a lever system that is connected via a servo. The manufacture of E-Canting is carried out in three stages, namely coding through Arduino IDE (Integrated Development Environment) software, assembling components using solder by connecting Arduino nano to other electronic components such as temperature sensors, heater plates, servos, LCDs, and incorporating the E-Canting framework. and electronic components. The energy used by the E-Canting is in the form of electricity which is channeled through the battery so that batik craftsmen can use the E-Canting as needed. The use of E-Canting is able to stabilize the temperature and viscosity of the night wax so as to minimize the occurrence of leakage. E-Canting is able to melt night wax with the required viscosity of 5.54 Pa at 80° in 3.39 minutes which has the potential to increase the amount of quality batik production.

Influence of specific electrical resistance on the heating of metal plates exposed to high frequency electromagnetic waves

Temperature distribution in the metallic plate influenced by high frequency electromagnetic wave depends on thermal and electrical properties of the plate material. The goal of the paper is to present the significance of the temperature dependence of the electrical resistivity and its influence on the plate heating. A mathematical model of the problem was established and an analytical closed-form solution the problem was presented. The active power of the electromagnetic wave was calculated by Poynting vector. Temperature field was obtained by integral-transform technique. Numerical examples were presented for three different materials (copper, aluminum, and steel). Calculated results show the large influence of temperature dependent electrical resistance on heating of the metallic plate.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ ТЕПЛОВЫХ ПРОЦЕССОВ В СИСТЕМЕ ПРЕДПУСКОВОГО ПОДОГРЕВА ДВС С ИСПОЛЬЗОВАНИЕМ КОМПОЗИТНОГО МАТЕРИАЛА

The engine oil heating system is one of the most important components that any internal combustion engine needs when operating at low temperatures. When a certain temperature is reached, the oil becomes more liquid and can perform its functions more efficiently, such as lubricating the engine and cooling its parts. However, there are cases when the engine starts at low temperatures, which prevents the proper operation of the engine. In such cases, an efficient device for rapid heating of the engine oil is required. To achieve this goal, an internal combustion engine preheater with a heating element in the form of a plate based on a composite material placed in the sump of the internal combustion engine is used. This material, unlike many others, has high thermal conductivity and thermal radiation, which makes it possible to achieve high oil heating performance. To simulate the heat transfer process in the engine oil heating system, a computer simulation using a two-dimensional model was used. The model consists of three main blocks: a sump pan, a heating plate based on a composite material and engine oil located inside the sump pan. When modeling, the following parameters are considered: heat flow generated by the heating plate; heat exchange between oil and plate; heat transfer between oil and sump pan; heat transfer from the sump pan to the environment; heat transfer formulas are used to calculate heat flows, and thermal conductivity is used to model boundary conditions. The data obtained will allow determining the optimal size and location of the heating element (plate), as well as choosing the optimal material for its production. Modeling of the heat transfer process and its mathematical description in the engine oil heating system using a heating plate based on a composite material makes it possible to achieve optimal system performance. In addition, it gives results on the basis of which it is possible to significantly reduce energy costs and improve the environmental assessment of the internal combustion engine.

Estimation of forced heat convection in a rectangular channel with curved-winglet vortex generator: A machine learning approach

• It was determined that angle of curved winglet, plate temperature, and Re on heat transfer are important parameters. • The findings achieved from the experimental datas have been evaluated as a result of the comparison with the target value within the ±4% diversion interval for all Nu. • The designed artificial neural network ( ANN ) structure indicated optimum mean square error ( MSE ) of 1.4x10 -2 , average relative deviation ( ARD% ) of 0.1771 and correlation coefficient ( R 2 ) of 0.9879 in architecture of average Nu datasets. There are a limited number of studies in the literature on the effect of curved fins on heat transfer. In this study, the effect of novel fin geometry and angle of attack of winglet ( α =30 o , 60 o , and 90 o ) on heat convection is estimated using a machine learning method. Airflow in the rectangular channel is investigated under constant heat flux ( q ''=100 W/m 2 ) and turbulence regime (5683≤Re≤17049) by experimental studies. Improvements in heat transfer are observed at different temperature values (T=30 o C, 50 o C and 70 o C) of the plate on which the blades were attached. In order to investigate the effect of input parameters on the prediction accuracy, an artificial neural network structure consisting of curved fin angle, Reynolds number and heater plate temperature parameters is preferred. Heat transfer is estimated by feedforward backpropagation (FFBP) and multi-layer perceptron (MLP) neural network algorithm using a data set containing 45 empirically obtained values in the forced convection condition. The training network has been calculated through Scaled Conjugate Gradient with ten neurons in the hidden layer. The results obtained from the experimental data assessed in consequence of the comparison with the target value within the ±4% diversion interval for all Nusselt numbers. Optimum mean square error (MSE), average relative deviation (ARD%) and correlation coefficient ( R 2 ) is obtained as 1.4x10 -2 , 0.1,771 and 0.9879 respectively in architecture of average Nusselt number datasets.

Thermal runaway features of large-format power lithium-ion cells under various thermal abuse patterns and capacities.

Herein, a comprehensive investigation is performed to research the thermal runaway features of large-format power lithium-ion cells under various heating patterns (2 kW electric heating oven and 600 W electric heating plate) and capacities (60, 150, and 180 Ah). Although the electric heating plate induces the cell to encounter thermal runaway earlier in comparison with the electric heating oven, the combustion does not appear for the former case since the compact stacking of the electric heating plate restrains the heat release of the heater such that the surrounding temperature is too low to induce the ignition of the thermal runaway combustibles. Besides that, it is interesting to find that the color of the ejected products under the electric heating plate condition becomes shallower as the thermal runaway proceeds, which implies that the ejecta in the initial of thermal runaway is mixed with quantities of solid particles and the proportion would gradually decrease. With the increase of the cell capacity, thermal runaway emerges later as a result of the greater cell height which delays the cell temperature rise, when exposed to an electric heating oven. In addition, the cell with a larger capacity demonstrates a lower peak temperature, a lower maximum temperature rise rate, a shorter combustion, a lower flame temperature, and a weaker radiation heat strength during thermal runaway; that is, less heat is released due to its violent thermal runaway behaviour. Finally, the severe explosion risk for the larger-capacity cell should be especially noted considering the larger amount of explosive gases released.

The improvement of levofloxacin and tetracycline removal from simulated water by thermosensitive flocculant: Mechanisms and simulation

Antibiotics were detected in worldwide natural water especially in COVID-19 period. The common flocculants rarely removed the dissolved antibiotics from natural water and wastewater. The flocculation improvement of organic polymer flocculants might solve the issue of antibiotic pollution or promote the removal efficiencies of antibiotics in water/wastewater treatment plants. Herein, a thermosensitive flocculant, P(DAC-NIPAM), was prepared via one-step method. It was investigated that the relationship between the various functional groups of P(DAC-NIPAM) and its flocculation performances in the treatment of simulated water containing levofloxacin, tetracycline, colloidal particles and natural organic matters. The removal mechanisms were discussed. The results indicated that the rich cationic, hydrophilic and hydrophobic groups of P(DAC-NIPAM) enhanced the interaction between flocculants and pollutants. The bridging of P(DAC-NIPAM) among micelles, charge neutralization, hydrogen bond between P(DAC-NIPAM) and two antibiotics, the shrinkage of P(DAC-NIPAM) molecule and enhancement of hydrophobicity when water temperature was above low critical solution temperature (LCST), co-flocculation and co-settlement of multiple pollutants all contributed to the efficient removal of levofloxacin and tetracycline from water. Flocculation simulation further confirmed that thermosensitive flocculant combined with heating plates was a potential candidate for antibiotic treatment in actual water treatment plants.

Design and experimental analysis of energy-saving and heat storage of a hot water tank based on the source-sink matching principle

In this work, a hot water tank was developed to improve the performance of energy-saving and heat storage based on the source-sink matching principle. Through the source-sink device, the excess heat at the upper boundary of the tank could be absorbed by a heat collecting chamber and transmitted through the heat pipes to the bottom heating plate for reuse. The reasonable distribution of heat was realized while the heat insulation was improved. A comparison experiment regarding the charging and discharging processes between the improved and conventional hot water tank was tested to verify the performance enhancement. The results showed that the total exergy efficiency of the improved hot water system was increased by 7.6%, and the exergy efficiency of the water tank was 25% higher than that of a conventional tank. The heat loss of the upper layer of the tank was reduced by 55%, which indicated the improved water tank had a noticeable energy-saving effect. In addition, the total amount of available hot water in the improved tank was twice that of the conventional tank under the same operating condition. The improved hot water tank was more aligned with the users’ demand for hot water.

A Novel Method for Growing α-Ga2O3 Films Using Mist-CVD Face-to-face Heating Plates

In this paper, the method for growing α-Ga2O3 films on c-plane sapphire substrates using an inexpensive fine-channel mist-CVD face-to-face heating plate was investigated. Because high temperatures can result in reactor deformation, expensive AlN ceramics resistant to deformation are used as the reactor fabrication material in traditional fine-channel mist-CVD equipment, which limits its use for promotion and research purposes. In this work, we used a face-to-face heating method to replace the traditional single-sided heating method which will reduce the requirement for equipment sealability. Therefore, cheap quartz can be used to replace expensive AlN ceramics to make reactors, which can greatly reduce the cost of mist-CVD equipment. We also investigated the effects of substrate temperature and carrier gas on the crystalline quality and surface morphology of α-Ga2O3 films. By optimizing the fabrication conditions, we obtained triangular grains with edges that were clearly visible in atomic force microscopy images. Using absorption spectrum analysis, we also found that the optical bandgap of the film reached 5.24 eV. Finally, we recorded a value of 508 arcsec for the full width at half maximum of the α-Ga2O3 (0006) diffraction peak in the X-ray diffraction pattern.

Miniaturized open-source 2LabsToGo screening of lactose-free dairy products and saccharide-containing foods

The open-source 2LabsToGo system is the only one in its nature. It combines in one miniaturized instrument all relevant steps normally performed in a chemical and biological laboratory. For the first time, the applicability of the 2LabsToGo system was studied for screening 17 food products. As examples, saccharides were analyzed in eight products of different matrix complexity, and the absence of lactose was studied in nine lactose-free dairy products. Derivatization including homogeneous reagent application and plate heating via the 2LabsToGo system was explored for saccharide detection, and its performance was investigated. The visual detection sensitivity of lactose was comparable to previous studies. The precision of lactose in milk matrix (%RSD 4.6%) as well as the coefficient of determination of the calibration function (0.9995) were highly satisfying. The obtained lactose content of milk (4.5%) was plausible. Screening eight saccharide-containing food samples showed the saccharides in agreement with the expectations for the respective food product. The lactose content of nine different lactose-free dairy products was proven to be below the 0.1% lactose limit value. As proof-of-principle and for verification, these screening results obtained with the miniaturized 2LabsToGo system were reproduced using conventional state-of-the-art instrumentation, which led to the same results. However, instrumental costs were comparably low for the 2LabsToGo system. The application of the new 2LabsToGo system was successfully shown for saccharide screening, which is attractive to the field of quality control or official food control.