Heating Preservation Research Articles

Eco-friendly drying techniques: a comparison of solar, biomass, and hybrid dryers.

Solar energy provides desired thermal energy for diverse applications, including industrial heating, domestic cooking, power generation, desalination, and agri-food preservation. Despite extensive research on solar drying from the scientific community, there are limited practical applications for small-scale use. This review attempts to analyze the design features of three specific types of dryers for food drying applications: solar evacuated tube dryers, biomass dryers, and hybrid solar dryers. The thermal performance of the three dryers is evaluated in terms of drying time, moisture removal, and temperature attained during drying. The review also assesses the prospects of solar dryers, highlighting the need for further research into innovative designs and advanced drying capabilities. The study provides valuable information for enhancing dryer performance with various integrated solutions.

Process parameters of microwave heating-assisted vacuum evaporation of tomato juice: quality, energy consumption, exergy performance, and kinetic processing

Increasing heating performance and preservation of product quality are critical factors in the food industry. Although microwave-vacuum heating is applied in many food processes, there are many unanswered questions about its effects on sensitive foods. In this study, the tomato juice was concentrated in microwave-vacuum heating system and results compared with conventional and conventional-vacuum heating methods. The effect of pressure and microwave power was investigated on quality parameters, energy consumption, exergy performance, and processing kinetics of tomato juice concentration. The processing time in the microwave-vacuum method was 2.3 to 6.3-fold lower than conventional and conventional-vacuum methods. The exergy performance was obtained in the range of 7.16–13.29% for microwave-vacuum heating and 2.04–2.99% for conventional methods. Microwave vacuum heating could reduce energy consumption by 30–71%, compared with conventional-vacuum methods. The minimum decline in ascorbic acid and total phenol content of tomato juice concentrate was observed for microwave-vacuum evaporation. Microwave-vacuum heating was an excellent concentration technique that provided tomato paste with improved nutritional quality, increasing exergy efficiency, reducing processing time and energy consumption compared to conventional and conventional vacuum processes.

Behaviors of novel manufacturing 1215MS+Bi steel in casting thermal processes

ABSTRACT Currently, the effects of cooling and heating rates on the sizes and morphologies of impurities and grains in the typical Bi-bearing 1215 MS steels in the manufacturing processes have never been studied, so this work aims to deduce their solidification and heating behaviors. The in-situ heating experiments were carried out using a high-temperature laser confocal microscope. Results show that bismuth could refine the dendrite arm spacing. Liquid Bi segregates at the solidification interface of grain boundary and inhibits the growth of grains. The surface tension of Bi-MnS is smaller than Bi-Fe. A big heating rate aggravated the thermal vibration of grains in local areas and resulted in large local temperature difference. Slow heating and heat preservation are helpful for sulfides to absorb heat and for achieving large grains. To sum up, this study broadens the recognition of free-cutting steels and further contributes to the development of new steel grade.

An Air Heat Tracing System of Firefighting Pipeline in Cold Region Highway Tunnel

Ensuring the proper operation of tunnel firefighting systems in cold regions is a key issue at hand. According to the characteristics of cold region tunnel fire control systems, this paper puts forward a kind of air heat tracing system (AHTS) that is suitable for cold region tunnel firefighting systems. In the AHTS, an annular air duct was used to heat the firefighting pipe and keep it warm, so that the water temperature in the firefighting pipe is above the freezing point, which helps prevent the water in the firefighting pipe from freezing and avoids the failure of the firefighting system. Meanwhile, the finite element software ANSYS was used to simulate the working state of the AHTS under different conditions, and the insulation effect under different conditions was evaluated. The results showed that the AHTS has a good heating and heat preservation function, which can effectively maintain the normal operation of the tunnel firefighting system in cold regions under a low temperature environment (below 0 °C). Furthermore, increasing the air temperature and air speed in the system was beneficial to the working effect of the AHTS, and the “high temperature and low speed” mode was beneficial to reduce the system power consumption. It is recommended that v = 5 m/s and Ta = 50 °C be used as the preset operating parameters. Finally, according to the numerical analysis results, the scientific and reasonable working parameters of the AHTS under different working conditions were optimized. The research content can provide new ideas and theoretical support for the thermal insulation technology of tunnel firefighting systems in cold regions in the future.

Effect of process factors of microwave hydrothermal method on the preparation of micron-sized spherical α-Al2O3 particles

Spherical α-Al2O3 particles with the size of 1–2 μm were obtained by microwave hydrothermal(M-H) method and subsequent microwave calcination. In the synthesis, Al2(SO4)3·18H2O was used as the aluminum sources, and CH4N2O was used as the precipitant. The effects of M-H temperature, heating preservation time and pressure in the reactor on the morphology, phase composition, particle size and surface area of the particles were studied. The results show that amorphous precursors with high sphericity and good dispersion can be rapidly (30 min) produced by M-H method at low temperature (100 °C). Increasing the temperature or extending the holding time will destroy the spherical morphology of the precursor, while transforming its phase from amorphous to γ-AlOOH. Pressure in the reactor does not change the phase composition of the precursor, but affects its dispersion and homogeneity. The precursor retains its spherical morphology after microwave calcination at 1100 °C for 90 min. The resulting powders were hot pressed and sintered at 1650 °C for 30 min to obtain a high-performance ceramic plate with a thermal conductivity of 27.1 W/(m·K) and a Vickers hardness of 21.4 GPa.

Large-scale heat pumps: Applications, performance, economic feasibility and industrial integration

Heat pumps can recover and upgrade industrial waste heat using renewable electricity, creating an essential technological lever to decarbonise thermal processes. High profitability requirements, unfavourable electricity-gas price ratios, and a lack of awareness of meaningful application possibilities among stakeholders from consultants and decision-makers, in both politics and companies, hinder further market penetration. To address these barriers, this review classifies 155 case studies of large-scale heat pumps to identify suitable characteristics that favour implementation. Unit operations, like utility water heating for cleaning purposes, process bath heating, drying, and thermal preservation processes, are identified as suitable processes that can be supplied with market-available heat pump technologies. These operations fall inside the current technology limits: > 50 kW heating capacity, up to 160 °C output temperature, and temperature lifts up to 95 K. COP regression models describe the efficiency of industrial water/water heat pumps, and recently also of HPs for drying and steam-generation purposes within a coefficient of determination of 0.87–0.96. These models form the basis for enhanced integration and economic assessment. Generalised results can be captured in the form of an universal nomogram to graphically evaluate ecological and economic break-even temperature lifts for heat pump integration concepts (i.e. between 26.5 K and 43 K temperature lift for an average price ratio of electricity to natural gas of 3.5 in Europe).

Structure-related differential proteins identification for sous-vide cooking hairtail (Trichiurus lepturus) product.

Optimal heating parameters for sous-vide cooking hairtail (Trichiurus lepturus) were selected and the differential proteins related to texture change were clarified using proteomics. Heating under 68 °C for 20 min was chosen to be the desirable heating parameter. Texture profile analysis (TPA) showed the texture of hairtail changed more severely during heat-up process than heating preservation process. Most of the high-content proteins did not change much during heating preservation. 169 kinds of proteins were identified as differential expressed proteins. Actin cytoplasmic 1, myosin heavy chain 1 and myosin heavy chain were the most variable structural proteins during heat-up process, with the change fold of 32.4, 29.1 and 18.8, respectively, while the highest structure proteins changing fold during heat preservation process were 16.7, 4.7 and 3.9, respectively, much lower than that of heat-up process. The partial deformation of structure-related proteins under sous-vide cooking was a vital factor in reserving the texture of hairtail.

Development and performance of heat insulation coatings for hot rolling of titanium alloy and superalloy rings

In recent years, with the continuous development of the equipment manufacturing industry, the seamless rings made of high-performance titanium alloys and superalloys have been widely used. These seamless rings mainly include aeroengine casing rings, carrier rocket capsule rings, gas turbine rings, oil/gas pipeline rings and so on. The metal ring hot rolling technology has become an irreplaceable manufacturing technology with its characteristics of low material consumption, high efficiency and high performance [1,2].However due to the special features of titanium alloys and superalloys, they have poor thermal processing plasticity and high processing sensitivity, thus cracks occur easily during metal temperature drop in hot rolling process. At the same time, the metal surface oxidation in the heating process also affects the surface quality and rolled parts performance. Therefore, using heat insulation and protective coatings is the most effective and easiest solution for the problem.In view of the above problems, Beijing Tianlichuang Glass Technology Development Co., Ltd. has successfully developed the water-based heat insulation coatings for titanium alloy & superalloy hot rolling at different rolling processes (different temperatures and different holding times). The coatings are coated on the metal surface at room temperature and dried before the billets are sent to furnace for heating. During the heating process, the coatings can prevent metal oxidation at high temperature and preserve heat during the billet transfer & rolling process without generating lubrication effect. These heating preservation coatings use a variety of crystalline non-metallic oxides, minerals and non-crystalline glass powders as major solid base materials, and blended with additives, adhesives and water to create suspensions, then applied to metal surface via brushing or spraying before heating. When design coating formulas, in order to realize good compatibility with the metals and right high temperature viscosity & expansion coefficient so as to achieve perfect match with different hot rolling processes, we should consider specific hot rolling process of titanium alloy & superalloy rings, that is, heating temperature, holding time, furnace atmosphere, and hot rolling condition.The heat insulation coatings can solve the problem of billet heat preservation & protection in the titanium alloy / superalloy ring hot rolling process, meanwhile reduce the surface cracks after hot rolling, making the metal easier to obtain even and fine microstructures. Also, the coatings are easy to use, non-toxic and environment friendly.

Thermal and electrical behavior of built-middle photovoltaic integrated Trombe wall: Experimental and numerical study

This study proposed a new system with the photovoltaic (PV) panel installed in the middle of channel of the Trombe wall (TW) system, called as built-middle photovoltaic integrated Trombe wall (PVMTW), which can realize multiple functions of electricity generation, space heating and heat preservation. The experiment rig was built to study the temperature field of the PVMTW system in heating seasons, in Hefei. A mathematical model of the PVMTW system was developed and validated against experimental data. Using the validated model, the thermal performance of the PVMTW system was investigated by comparison with that of the classic Trombe wall. The results showed that in the daytime, the average thermal efficiency of the PVMTW system was 65.2% higher than that of the classic TW system. In terms of room air temperature and interior surface temperatures on the walls, the indoor thermal comfortable of the PVMTW system was almost the same as that of the classic TW system. The average predicted mean vote (PMV) for two rooms (room with the PVMTW system and room with the classic TW system) were 0.05 and −0.36, respectively. Additionally, the average electrical efficiency and average total efficiency achieved 0.120 and 0.585, respectively.

Numerical Investigation into the Two-Phase Convective Heat Transfer within the Hold of an Oil Tanker Subjected to a Rolling Motion

A crude oil tanker usually encounters a rolling motion during sea transportation, which leads to rotational movement and sometimes a sloshing of the liquid hold. This rolling-induced body motion seriously affects the thermal and hydraulic behavior of the liquid hold, which then affects the heating process and heat preservation of the tanker. Clarification of the involved thermal and hydraulic characteristics is the basic requirement for establishment of a scientific heating scheme and heat preservation method. A two-phase 3D model considering the free liquid surface and non-Newtonian behavior of the fluid was established for the thermal calculation of the liquid holds in oil tankers. The thermal and hydraulic characteristics of the liquid hold were investigated under different combinations of dimensionless parameters, and the combined effect of rolling and fluid non-Newtonian behavior was investigated. It was found that rolling intensifies the heat transfer based on the combination of the Richardson number (Ri) and the rotation-strength number (ω*), and non-Newtonian behavior of the fluid effectively affects the heat transfer in a rolling motion. This research is expected to provide a reference for design and optimization of the heating and heat preservation method for oil tanker operation.

Thermal management of 48 V standby battery for outdoor base station at cold environment

The standby battery for outdoor base station could not function properly at cold environment for a long time. In order to improve its performance and lengthen its life time, it was necessary to heat the battery and keep warm. This dissertation presented the heating and heat preservation method of 48 V Lead-acid battery pack for base station based on the heating plate and phase change materials at cold environment. Then, the thermal management performances of this battery pack were simulated. The results showed that the uniformity of battery temperature field was increased and the heat preservation process was lengthened effectively. And the pack kept good working condition after continuous heating and heat preservation progress. The method was simple and practicable, and it could be used on the thermal management of lithium ion battery because of its good applicability

Environmental Impact and Carbon Footprint Assessment of Taiwanese Agricultural Products: A Case Study on Taiwanese Dongshan Tea

Climate change is an important global environmental threat. Agriculture aggravates climate change by increasing greenhouse gas (GHG) emissions, and in response, climate change reduces agricultural productivity. Consequently, the modern agricultural development mode has progressively transformed into a kind of sustainable development mode. This study aimed to determine the environmental impact and carbon footprint of Dongshan tea from Yilan County. Environmental impact was assessed with use of SimaPro version 8.0.2 and IMPACT2002+. Results showed that climate change has the largest impact upon it in general, followed by human health, natural resources, and ecosystem quality. Furthermore, with use of the IPCC 2007 100a method for carbon footprint of products (CFP), conventional tea was found to have a CFP of 7.035 kgCO2-e, and its main contributors are the raw material (35.15%) and consumer use (45.58%) phases. From this case study, we found that the hotspots of the life cycle of environmental impact of Taiwanese tea mainly come from fertilizer input during the raw material phase, electricity use during manufacturing, and electricity use during water boiling in the consumer use phase (which contributes the largest impact). We propose the ways for consumers to use of highly efficient boiling water facilities and heating preservation, and the government must market the use of organic fertilizers in the national policy subsidies, and farmers have to prudent use of fertilizers and promote the use of local raw fertilizers, and engagement in direct sales for reducing the environmental impacts and costs of agricultural products and thus advancing sustainable agriculture development.

Millimeter-wave beam scattering by edge-plasma density fluctuations in TCV

In magnetically confined fusion devices, the use of millimeter waves (mmw) at the electron cyclotron (EC) frequencies ranges from plasma diagnostics to plasma heating, current drive and core confinement preservation. For large tokamaks such as ITER, numerical simulations and analytical estimates suggest that plasma edge turbulence could significantly broaden the EC-beam, possibly preventing tearing modes stabilization at the designed power levels. We report measurements of mmw-beam scattering by plasma turbulence in the TCV tokamak. A mmw-Gaussian beam is injected from the top of the device and the transmitted power is measured at the bottom. We show that the measured plasma density fluctuations in the upper part of the scrape-off layer (SOL) are the cause of fluctuations of the transmitted mmw-power. A full-wave model based on COMSOL multiphysics is presented and compared against the wave-kinetic-equation solver WKBeam in a TCV case. Using the SOL turbulence simulations from the GBS code, comparison between the scattering effect on the mmw-beam with both the full-wave simulations and the experiments are ongoing. We also present experimental observations of rapid changes in the transmitted power caused by ELMs in ELMy H-mode plasma.

Research on Energy-Saving Scheduling of a Forging Stock Charging Furnace Based on an Improved SPEA2 Algorithm

In order to help the forging enterprise realize energy conservation and emission reduction, the scheduling problem of furnace heating was improved in this paper. Aiming at the charging problem of continuous heating furnace, a multi-objective furnace charging model with minimum capacity difference and waiting time was established in this paper. An improved strength Pareto evolutionary algorithm 2 (SPEA2) algorithm was designed to solve this problem. The original fitness assignment strategy, crossover operator and population selection mechanism of SPEA2 are replaced with DOPGA (Domination Power of an Individual Genetic Algorithm), adaptive cross operator, and elitist strategy. Finally, the effectiveness and feasibility of the improved SPEA2 was verified by actual arithmetic example. The comparison of results gained from three methods shows the superiority of the improved SPEA2 in solving this problem. Compared with strength Pareto evolutionary algorithm (SPEA) and SPEA2, the improved SPEA2 can get a better solution without increasing time complexity, the heating time is reduced by total 93 min, and can save 7533GJ energy. The research in this paper can help the forging enterprise improve furnace utilization, reduce heating time and unnecessary heating preservation time, as well as achieve sustainable energy savings and emissions reduction.

Parameters Optimization of γ-Ti-46.6Al-1.4Mn-2Mo Alloy by Hot-Pressing Sintering and its Microstructures

In order to obtain the maximum relative density of γ-Ti-46.6Al-1.4Mn-2Mo alloy, the effects of the sintering temperature, heating preservation time and compacting force prepared by hot pressing were studied using Back Propagation (BP) Neural Network. The process parameters were optimized by Genetic Algorithm (GA) contributed by the use of Matlab. The results show that the optimum preparation process for Ti-46.6Al-1.4Mn-2Mo alloy are hot-pressing sintering temperature of 1374oC, heating preservation time of 291 min, compacting force of 37Mpa. The relative density of Ti-46.6Al-1.4Mn-2Mo alloy prepared under the condition is 96.11% (predicted value is 96.87%) with the relative error was only 0.78%. The microstructures of Ti-46.6Al-1.4Mn-2Mo alloy are studied by X-ray, optical microscope and SEM.