Plate Heat Research Articles

An experimental inverse problem in determining spatially varying surface heat flux using measured temperature readings

An experimental investigation to estimate the unknown spatially dependent surface heat flux of a flat plate based on the surface temperature readings taken by a thermography camera and the conjugate gradient method (CGM) is examined in this study. In the present three-dimensional inverse problem, the functional form of the heat flux is considered to be initially unknown; thus, the functional form of the heat flux is classified as the category of function estimation. In addition, air velocity is specified as the working condition, not the heat transfer coefficient; therefore, it is defined as an inverse heat conduction-convection conjugated problem (IHCCCP). The experimental study for estimating the unknown spatially dependent surface heat flux has not been examined previously in the IHCCCP. The estimations of the inverse solutions are conducted experimentally with two designed plate heaters and various inlet air velocities and plate thicknesses, and the total heat losses are found to be approximately 5% of the original design heating power. The experimental results indicated that for a uniform heating design (Design A), the estimated heat fluxes are always very accurate if the heat losses are deducted from the design power. For the nonuniform heating design (Design B), due to the existence of two discontinuities in the heating power, the estimated relative errors for heat fluxes are found to be between 16% and 18% using 6 to 8 iterations, reflecting the nature of the inverse problem, i.e., a small measurement error will amplify the error of the estimates; in addition, the estimated heat flux becomes less accurate as the plate thickness increases. Finally, numerical simulations with errorless measurements are performed, and the results reveal that the estimated errors for heat fluxes can be decreased to approximately 8% with 150 iterations for Design B.

Internal feed preheating necessary for energy-efficient modular multi-effect membrane distillation

Multi-effect membrane distillation (MEMD) systems achieve a high product recovery ratio by effectively utilizing the heat of condensation for further vaporization within the module. In this study, a novel internal feed-preheating design for improving the energy efficiency of modular MEMD systems is proposed and evaluated using a 2D CFD model. Custom user-defined functions are implemented to account for water vapor and associated energy transport across the membrane in an MEMD design with serpentine flow across various effects. Preheat channels embedded into the condensation plates help increase the temperature of feed entering the first effect by ∼25 K, close to heater plate temperature. As a result, high-grade external heat input is not used for sensible heating, instead being utilized towards evaporation and pure water production, resulting in ∼32 % improvement in energy efficiency. However, the added thermal resistance of the preheat channels results in lower average flux and hence recovery, which can be ameliorated by increasing the effective conductivity of the preheat channels. Increasing the thermal conductivity of preheat channels results in ∼23.5 % rise in recovery ratio. Such preheat designs are necessary to reap energy efficiency improvements by increasing the total number of effects in multi-effect vacuum and gap MD systems.

Innovative Design and Numerical Simulation Research of Downhole Electrical Heaters for In-Situ Oil Shale Exploitation

Summary To improve the overall performance of continuous spiral baffle heating systems, we propose in this paper two different structural models of electric heaters for in-situ shale oil wells. The models are simulated using Fluent software to investigate the flow and heat-transfer characteristics under different mass flow rates. The variation in heat-transfer coefficient, pressure drop, and overall performance of the heating plate under different gas mass flow rates and heights of heating and shielding plates are analyzed. The performance of the two different heater structures is compared with Wang’s laboratory experiment. The results show that Model I of the heating system has the best overall performance when the gas mass flow rate is between 9.74×10−3 kg/s and 1.624×10−2 kg/s, and the height of the heating and shielding plates is 35 mm at a mass flow rate of 9.74×10–3 kg/s. Wang’s pressure drop (ΔP) is more than 2.48 times higher than that of Model I and more than 6.49 times higher than that of Model II, while the heat-transfer coefficient (h) of both Model I and Model II is increased by more than 15% compared to Wang’s experiment. The overall performance (g) of Model II is increased by more than 5.7 times compared to Wang’s experiment, and the overall performance (g) of Model II is increased by more than 1.68 times compared to Model I. These results provide a theoretical basis for optimizing the design of continuous spiral baffle heating systems.

Simulation Analysis and Optimization of Temperature Field for Hot In-Place Asphalt Pavement Recycling

The heating temperature field of asphalt pavement is a key factor affecting the quality of pavement heat-in-place recycling (HIR). Using the heat transfer characteristics of HIR, a three-dimensional heat transfer model was simplified into a one-dimensional heat transfer model along the depth direction. A temperature sensor was installed on the site to monitor the temperature change of the asphalt pavement at different depths under different heating powers, and the actual temperature and heat transfer model were highly compatible. Through this model, the influence of heater running speed and heater heat flux density on the temperature field of the asphalt pavement heated by infrared radiation (IR) was calculated by the finite differential method, and an optimal combination of heating is proposed. In accordance with construction continuity and minimum energy consumption principles, at the 3.0–3.5 m/min recommended running speed of the heating machine, the asphalt at a depth of 4 cm satisfied the temperature demand, but the asphalt on the road surface was prone to heat aging. The heating effect of the constant temperature variable power heating (CTVP) is ideal, but the continuous change in heating power increases the difficulty of construction. Constant temperature discrete power heating (CTDP) divides the ideal heat flux density curve into several stages according to the length of the heating plate in the heater, increasing the feasibility of constant temperature heating in engineering and reducing energy consumption.

Can tires turn green?

Tires’ substantial environmental footprint is set to drop as producers increase their use of renewable materials and efficient technologies emerge for chemically recycling them. Currently, most tires are incinerated or landfilled, at a high environmental price. While the sector’s footprint may be shrinking, millions of metric tons of rubber particles get released annually as tires wear down on roads. And independent scientists say this pollution is a cause for concern. The tire industry says it is trying to understand the impacts of these particles. Until issues around them are addressed, however, the sustainable tire will remain out of reach. Rubber crumbs rain down onto more than 150 electric heating plates, raising their temperature to over 600 °C within seconds. In an atmosphere depleted of oxygen, the crumbs rapidly transform into a gas, which is cooled into a synthetic oil and a solid that is mostly carbon black. This process is

Experimental and numerical analysis of heat transfer in a dimple pattern heat exchanger channel

In contrast to the predominant herringbone shape of heat plates, a microplate heat exchanger has an array of relatively small dimples. Its number and shape define the characteristics of such a plate heat exchanger. Literature, however, of the flow characteristics in such kinds of channels is scarce. Precise knowledge of the flow specifics in such a channel is of key importance to develop efficient new products. Single-phase water flow and heat transfer in microplate heat exchanger was investigated with the laboratory experiments and use of computational fluid dynamics simulations. A novel and innovative laboratory experiment was developed where flow characteristics and heat transfer in the microplate heat exchanger were measured. Experimental results were directly used as boundary conditions in numerical simulations. With this approach a direct validation of the results of numerical simulations were obtained. Heat transfer simulations were performed with three turbulence models: k- ε, k-ω SST and the Reynolds stress model. The most reliable results in heat transfer analysis were obtained using the Reynolds stress model where results are on average 7.05% lower compared to the results of the laboratory experiment. When all experimental uncertainty contributions were analysed, the simulation results were in the band between − 11% and 1.8% compared to the results of the laboratory experiment. Numerical simulations show that the heat transfer coefficient in the channel is proportional to Re0.64 in the analysed geometry of a microplate heat exchanger. The heat transfer coefficient was calculated and was between 9740 and 21990 W/m2K at Reynolds numbers 1170 and 4170 respectively.

Analysis of the thermal management of electronic equipment byemploying silicon carbide nano-pcm-based heat sink.

Electrical and electronic equipment like light bulbs, computing systems, gaming systems, DVD players, and drones experiences heat generation during extensive use. The heat energy should be liberated to ensure uninterrupted performance and prevent premature failure of the devices. This study uses an experimental setup of the heat sink, phase change material, silicon carbide nanoparticles, thermocouple, and data acquisition system to control heat generation and increase heat lost to the surroundings in electronic equipment. The silicon carbide nanoparticles are mixed in varying compositions, i.e., 1wt.%, 2wt.%, and 3wt.%, in paraffin wax as the phase change material. The influence of the heat input (15W, 20W, 35W, and 45W) through the plate heater is also studied. The operating temperature of the heat sink was allowed to fluctuate between 45 and 60°C while experimenting. The fluctuation in the temperature of the heat sink was recorded to monitor and compare the charging, dwell, and discharging periods in the heat sink. It is observed that increasing the percentage composition of silicon carbide nanoparticles in the paraffin wax resulted in increasing the peak temperature and the dwell period of the heat sink. Increasing the heat input above 15W benefited in controlling the duration of the thermal cycle. It is inferred that high heat input is beneficial in enhancing the heating period, while the percentage composition of silicon carbide in the PCM benefits by increasing the heat sink's peak temperature and dwell period. It is concluded that high heat input, i.e., 45W, is beneficial in enhancing the heating period, while the percentage composition of silicon carbide in the PCM benefits by increasing the heat sink's peak temperature and dwell period.

Comparative experimental analysis of potato slice drying using a multiple phase change material cascaded modified indirect solar dryer and conventional indirect solar dryer

In the present research, multiple phase change materials (M-PCMs) have been utilized to enhance the performance of conventional indirect solar dryer (ISD). The bheem paraffin and paraffin wax having phase change temperatures of 50–55 °C and 60–62 °C were cascaded in rectangular chambers at beneath of absorber plate at the inlet and outlet side up to nearly half the length of the absorber plate of the solar air heater (SAH), known as a modified ISD. The experiments were carried out on conventional and modified ISD simultaneously under the climate of Valsad (20.61° N, 72.91° E), Gujarat, India. An atmospheric air with a velocity of 15 m/s was flown through conventional and modified ISD. In the first batch, 0.5 kg of pre-processed potato slices were placed in the bottom and top trays of conventional and modified ISD whereas in the second batch, 0.3 kg was placed on each tray. A 2 h and 1 h faster drying of potato slices was achieved in the bottom and top trays for the first batch in modified ISD than in conventional ISD. In the second batch, nearly 92.11% and 54.35% drying of potato slices in the bottom and top trays was achieved in modified ISD, which was 269.92% and 227.41% higher than conventional ISD. During 12 h of the drying operation, a total of 1.13 kg of water evaporated from the potato slices in modified ISD compared to 0.87 kg in conventional ISD. Compared to conventional ISD, an enhancement of 22.29% and 7.92% in SAH efficiency without and with considering blower power, an enhancement of 29.69% in overall drying efficiency, and a reduction of 22.87% in specific energy consumption were achieved for modified ISD. The use of M-PCMs in conventional ISD significantly enhances the drying of potato slices during the sunshine as well as off-shine hours and enhances the performance of conventional ISD.

Structural variety of developing and equilibrium horizontal convection confined in a rectangular vessel resulting from different heating plate arrangements

Structural variety of developing and equilibrium horizontal convection confined in a rectangular vessel resulting from different heating plate arrangements

Анализ теплоэнергетических параметров тепличных комплексов

The analysis of existing heating systems for greenhouse complexes was carried out, their advantages and disadvantages were identified. Tasks have been set for the use of structures based on an energy-efficient surface-distributed method of heating (heating) using plate and volumetric multi-electrode composite electric heaters. A complex for determining the heat balance in the greenhouse has been carried out, inflows and outflows of heat have been identified. The possibility of using heat influx from a plate multi-electrode composite electric heater is presented, which makes it possible to normalize the microclimate in the greenhouse during the cold periods of the year. Keywords: TEMPERATURE HEAT SUPPLY, HEATING, GREENHOUSE, ENERGY BALANCE, HEAT BALANCE, HEAT TRANSFER, ENERGY SAVING

Fluid-structure interaction of a thin flexible heater inside a lid-driven cavity

The purpose of this study is to explore the characteristics of fluid-structure interaction and heat transfer enhancement from a hot flexible thin plate during mixed convection. The mixed convection condition of the plate heater is assumed by placing it inside a lid driven cavity with top and bottom cavity walls being fixed and insulated while left and right cavity walls maintained at constant low temperature move in downward and upward direction respectively. The Galerkin Finite Element Approach has been used to numerically solve equations describing unsteady flow, thermal and stress fields in the Arbitrary Lagrangian-Eularian (ALE) framework. Key parameters include Reynolds number ( Re) and Richardson number ( Ri), and Cauchy number ( Ca) which are varied in the range of 100 ≤ Re ≤ 500, 0.1 ≤ Ri ≤10, and 10−4 ≤ Ca ≤ 10−7 respectively. To investigate the effect of the heater’s geometry, the plate length ( l) has been varied within 0.1 ≤ l ≤ 0.7. The results have been presented in terms of the distribution of streamline and isotherm, heat transfer rate from the flexible heater as well as its deformation. The outcomes reveal that heat transfer enhances with the increase in Reynolds number and Richardson number while it degrades with the extension of the heater. Moreover, thermal frequency obtained by Fast Fourier Transform (FFT) indicates dominant peaks at higher Reynolds number and Richardson number although these become insignificant as the plate becomes rigid.

Application of Self-Assembled Polyarylether Substrate in Flexible Organic Light-Emitting Diodes.

The structure used in this study is as follows: substrate/PMMA/ZnS/Ag/MoO3/NPB/Alq3/LiF/Al. Here, PMMA serves as the surface flattening layer, ZnS/Ag/MoO3 as the anode, NPB as the hole injection layer, Alq3 as the emitting layer, LiF as the electron injection layer, and aluminum as the cathode. The properties of the devices with different substrates were investigated using P4 and glass, developed in the laboratory, as well as commercially available PET. After film formation, P4 creates holes on the surface. The light field distribution of the device was calculated at wavelengths of 480 nm, 550 nm, and 620 nm using optical simulation. It was found that this microstructure contributes to light extraction. The maximum brightness, external quantum efficiency, and current efficiency of the device at a P4 thickness of 2.6 μm were 72,500 cd/m2, 1.69%, and 5.68 cd/A, respectively. However, the maximum brightness of the same structure with PET (130 μm) was 9500 cd/m2. The microstructure of the P4 substrate was found to contribute to the excellent device performance through analysis of the AFM surface morphology, film resistance, and optical simulation results. The holes formed by the P4 substrate were created solely by spin-coating the material and then placing it on a heating plate to dry, without any special processing. To confirm the reproducibility of the naturally formed holes, devices were fabricated again with three different emitting layer thicknesses. The maximum brightness, external quantum efficiency, and current efficiency of the device at an Alq3 thickness of 55 nm were 93,400 cd/m2, 1.7%, and 5.6 cd/A, respectively.

DESIGN OF PLATE HEAT EXCHANGER FOR HEAT TREATMENT INDUSTRY

This study discusses the design of plate type heat exchangers (PHE). Conventional heat exchangers have many drawbacks, including difficult maintenance, high cost, and increased area usage. In contrast, plate heat exchangers have a number of benefits over traditional heat exchangers. Because the liquid spreads across the plate, PHE has a bigger surface area. The study discusses and explains the design of the plate type heat exchanger, plate material, chevron angle, and gasket material since the plate allows for faster heat transmission. Key Words: Plate heat exchanger, Design, materials.

Comparison of Thermal and Laser-Reduced Graphene Oxide Production for Energy Storage Applications.

A way to obtain graphene-based materials on a large-scale level is by means of chemical methods for the oxidation of graphite to obtain graphene oxide (GO), in combination with thermal, laser, chemical and electrochemical reduction methods to produce reduced graphene oxide (rGO). Among these methods, thermal and laser-based reduction processes are attractive, due to their fast and low-cost characteristics. In this study, first a modified Hummer's method was applied to obtain graphite oxide (GrO)/graphene oxide. Subsequently, an electrical furnace, a fusion instrument, a tubular reactor, a heating plate, and a microwave oven were used for the thermal reduction, and UV and CO2 lasers were used for the photothermal and/or photochemical reduction. The chemical and structural characterizations of the fabricated rGO samples were performed by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman spectroscopy measurements. The analysis and comparison of the results revealed that the strongest feature of the thermal reduction methods is the production of high specific surface area, fundamental for volumetric energy applications such as hydrogen storage, whereas in the case of the laser reduction methods, a highly localized reduction is achieved, ideal for microsupercapacitors in flexible electronics.

Noninvasive measurement of temperature for simulated tissue based on piezoelectric micromachined ultrasonic transducers

This paper reports a noninvasive measurement of temperature for simulated tissue based on an AlN piezoelectric micromachined ultrasonic transducer array. Polydimethylsiloxane and a built-in heating plate are used to simulate the thermal therapy of human tissue. Based on time-of-flight (ToF) from the simulated tissue surface to the heating plate surface and corresponding temperature data, the piecewise linear fitting method is used to fit the ToF-temperature curve, and its sensitivity is (below 50 °C) and (from 50 °C to 65 °C). The average error of real-time temperature measurements is 0.58 °C for temperatures below 65 °C. The proposed method can provide a good solution for temperature detection during thermal therapy.

Heat transfer performance of a novel PCM based heat sink coupled with heat pipe: An experimental study

Thermal management is vital for all electronic applications due to the system’s considerable heat output. The improvement of the charging time for a continuous operation has been the subject of much research to date. However, for intermittent operations, which are most likely to be experienced in practical applications are considered, a reduction in the heat discharge time from the heat sink is equally as essential as an improvement in the charging time. The main aim of this study is to develop a strategy that enhances the charging cycle performance and performs well during the discharging cycle as well.This paper reports the experimental heat transfer results of a novel n-Eicosane phase change material (PCM) based finned heat sink coupled with a heat pipe for electronic thermal management. Heat transfer experiments are performed on four heat sink (HS) configurations: heat sink (i) without a fin, (ii) with a circular stem at the center, (iii) with three longitudinal plate fins having a central gap for heat pipe provision, and (iv) with four longitudinal plate fins. A circular heat sink having an outer diameter of 58 mm and 55 mm in height with a wall thickness of 4 mm is considered for all the heat sink configurations. The fill ratios considered are 33, 66, and 99%. The heat input given to the plate heater is varied between 8 and 12 W. Results show that the HS performs best at a PCM fill ratio of 99%. A sintered heat pipe is coupled with a three fin heat sink. Finned heat sink with heat pipe (FHSHP) enhances the (i) charging time by 21.1%, 15.41%, and 21.65%, (ii) discharging time by 22.5%, 23.25%, and 21.25% compared to a heat sink with three fins for the power level of 8, 10, and 12 W, respectively. Further, the overall effectiveness is high for the FHSHP compared to all the geometries considered in the present study. The novel design (FHSHP) is advantageous from an engineering standpoint for efficient thermal management of electronic components.

Experimental study of a solar air heater with modified absorber plate through square obstacles with threaded pin fins

In this present experimental study, a flat absorber plate of a solar air heater (SAH) is modified through square obstacles with threaded pin fins to rate the performance of the SAH. It is evident from the literature that the poor rate of heat transfer of flat plate SAH remains a matter of concern for practicing engineers. The modification of the absorber plate’s surface becomes to be an effective practice for the researchers to counter the drawbacks and augment the performance of the SAH. From the energy, exergy, exergoeconomic, and enviroeconomic standpoint, the present study discloses that the modified absorber plate performs better than the conventional flat absorber plate. The exit temperature of the solar air heater is increased by about 9% using the modified absorber plate. The energetic efficiency is found to be improved with the governing parameters. For a fixed air flow rate of 0.0094 kg/s, using a modified plate absorber augments the useful energy gained and the energy efficiency by 28.81% and 23.59%, respectively, for the higher collector tilt angle of 35°. Similarly, exergy efficiency is reported to be increased by 30% for the same conditions. Using a modified absorber plate decreases the exergy destruction by about 10% for the higher collector tilt angle and air flow rate. The energy payback time is estimated to be 1.42 years and the CO2 mitigation is reduced to 32.98 kg/year compared to the CO2 mitigation value of 333.33 tonnes using the modified absorber plate for a system life of 30 years.

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.