Infrared Heating Research Articles

Development of Applications of Infrared Heating in Ferritic Salt Bath Nitrocarburizing Process

Abstract A rapid salt bath nitrocarburizing process technology is primarily developed by providing infrared heating instead of conventional induction heating. Two thermochemical techniques, conventional salt bath nitrocarburizing with induction heating and salt bath nitrocarburizing with infrared heating, were done on AISI 1018 low-carbon steel. The results showed that infrared heating could significantly enhance the nitrocarburizing efficiency and shorten the holding time comparing with the conventional nitrocarburizing process. Nitrocarburizing time has been shortened from 120 min to 90 min in infrared heating technique, and a more intense carbon-enriched compound layer is observed in field emission scanning electron microscope micrographs when compared to the conventional nitrocarburizing process. Energy dispersive X-ray spectroscopy analysis reveals higher weight % (1.18 %) and atomic % (2.85 %) of nitrogen in infrared-heated nitrocarburizing process specimens as compared to weight % (0.96 %) and atomic % (1.92 %) in conventional nitrocarburizing specimens. A line scan mapping of compound layer and diffusion zone was done to find out the elemental intensities and results favored by infrared heating specimens. Furthermore, an increase in microhardness was observed because of the thick and compact compound layer in infrared heating. Also, more profound diffusion zone was observed as compared to the conventional nitrocarburizing process. Further, surface roughness values have been found to be very high because of the highly porous surfaces created by the postoxidation process, and this could also be attributed to higher radiant energies from infrared heating.

A mathematical model of heat transfer during tomato peeling using selected electric infrared emitters

A two-dimensional mathematical model of heat transfer was developed for heat transfer during the infrared (IR) peeling of tomato. The model was used to predict the temperatures of tomato heated using selected electric IR emitters having different characteristics. The IR heating process was hypothesized as a mathematically gray-diffuse radiation problem based on the enclosure theory. The heat transfer model was solved in COMSOL using a finite element scheme to predict the temperature of tomato during different heating times. The model was validated by comparing the predicted and measured temperatures of tomato surface that were presented in our accompanying study (Vidyarthi et al., 2019). The predicted temperatures agreed well with the experimental data (R 2 > 0.99). Simulation results indicated that IR heating for 25 s induced a dramatic temperature increase (>100 °C) on the tomato surface layers; limited to a maximum of 0.66 mm underneath the surface. There was no change in the temperature of tomato center (<28 °C). The rapid increase of tomato surface temperature and insignificant rise in interior temperature indicated a meager penetration capacity of IR radiation, causing insubstantial damage to tomato flesh integrity, and consequently preserving the nutritional quality of peeled product. This study provides designing parameters of an efficient IR tomato peeling technology, ensuring a high peeling performance and product quality. • A two-dimensional heat transfer model was developed for the infrared (IR) peeling of tomato. • The predicted and experimental surface temperatures of tomato agreed well. • Tomato surface layers experienced a dramatic increase of temperature. • Tomato interior showed insignificant rise in temperature. • Indicated a higher integrity of tomato flesh and a better quality of peeled product.

Design and performance evaluation of a pilot-scale pulsed vacuum infrared drying (PVID) system for drying of berries

The objective of current work was to develop a new pilot-scale pulsed vacuum infrared drying (PVID) system for the drying of berries. The system design and drying performance evaluation for grape and goji berries are reported here. The PVID system consisted of three major sections, including infrared heating section, vacuum section, and a controlling section. Electrical infrared (IR) emitter was made with carbon fiber sheet at the thickness of 2–4 mm, which emitted IR wavelength of 1–30 μm. The control system was used to achieve paused pressure by switching the drying chamber pressure between atmospheric pressure (101 kPa) and vacuum (3–10 kPa) successively and maintaining the pressure for different time periods. Grapes and goji berries were dried in a single layer at three different temperatures (55, 65, and 75 °C) with an atmospheric duration ranging from 1 to 12 min and vacuum duration from 10 min to constant vacuum. The drying characteristic and quality of PVID dried berries were investigated and compared with that of hot air (HA) dried berries. Results showed that the IR heating temperature, atmospheric duration, and vacuum duration had significant effects (p < .05) on the drying time. The optimum drying conditions for grapes and goji berries were IR heating at 65 °C, vacuum duration of 15 min, and atmospheric duration of 4 and 2 min, respectively. The corresponding drying time is nearly 720 min for grapes, and 450 min for goji berries. The PVID dried grapes and goji berries had more attractive color than that of HA dried ones. These findings demonstrated that PVID should be a promising method to produce high-quality dried berries. This study laid a good foundation for scaling up the technology in the future.

DYEING OF COTTON FABRIC WITH REACTIVE DYE USING INFRARED HEATING TECHNIQUE

A anew technique represented in this study for evaluating the performance of dyeing cotton fabrics using infrared (IR) heating technique compared to the conventional exhaust dyeing method. The effect of this new technique has been studied on the color strength (K/S), color fastness properties, tensile strength and elongation of the dyed cotton fabrics made of two Egyptian varieties Giza 90 and Giza 95 using Procion H-EXL blue reactive dye with concentrations 2%, 4% and 6% . The color strength values of the infrared heating technique in dyeing were better than those of the exhaust dyeing obtained using the same dye concentration 4% and the same recipes. Also the results for dyeing using infrared heating technique had no bad effect on the color fastness or on the dyed cotton fabric mechanical properties.

Experimental implementation of a real-time power flux estimator for the ITER first wall on the TCV tokamak

A control-oriented approach to the monitoring of wall power flux densities on ITER has been successfully developed. It is based on real-time equilibrium reconstruction in 2-D which is then used to describe the deposited heat flux as a poloidal flux function with user specified parameters for the power exhausted into the scrape-off layer (SOL) and the SOL heat flux width. To account for the real 3-D geometry of the plasma-facing components (PFC), appropriate weighting factors are derived from magnetic field line tracing in 3-D. Integration of the 3-D effect is performed with a new GUI-based software environment, SMITER, incorporating a field line tracer and permitting import and meshing of PFC CAD models. The paper discusses the experimental demonstration of the model-based wall heat flux algorithm on the TCV tokamak, reporting on the benchmarking of the new code package, SMITER against infra-red camera heat flux measurements and the derivation of the component shaping weighting factors. A comparison of the real-time estimation of the peak power flux and its spatial location against the off-line infra-red measurement for limiter plasma configurations is presented.

Evaluation of selected electric infrared emitters for tomato peeling

The performance of selected electric infrared (IR) emitters with different emissive powers was investigated examining tomato heating rate, peeling performance and final product quality. Four types of electric emitters, including ceramic full trough element (CFTE), pillared quartz element (PQE), quartz tungsten medium (QTM), and quartz halogen medium (QHM), were selected based on their ability to produce high emissive power with appropriate range of wavelengths. The electric emitters were tested to heat the tomato cultivar Hz 6410 for peeling, using a prototype IR heating system under similar conditions. The electric emitters attained high surface temperatures (602–825 °C) and emissive powers (27–37 kW m−2). High emissive powers of these electric emitters increased the heating rate of tomato, resulting in a high peeling performance and product quality in significant short times (≤25 s). Among all the studied emitters, PQE with the highest surface temperature (825 °C) and emissive power (37 kW m−2) took 10 s to heat the tomatoes to the degree that they had excellent peeling easiness while meeting the USDA peelability standard. However, tomatoes experienced undesirable skin burns when the heating time was too long at high emissive powers. The study provided valuable information about the suitability of different electric emitter with the IR wavelength spectrum (2.6–3.3 μm) for tomato peeling application.

An ode to polyethylene

Polyethylene is one of the most produced materials in the world—is it a blessing or a curse? This article makes the case for the former by highlighting a range of emerging applications of polyethylene in energy and sustainability, including passive cooling of electronics and wearables, water treatment and harvesting, and even ocean cleanup from plastic waste debris. Usually, when the word “polyethylene” is mentioned in the context of discussing sustainability issues, a good chance the message is that “the current level of environmental plastic pollution is unsustainable.” Polyethylene does indeed comprise a large volume of plastic waste, but only because it is used in so many different products, which eventually reach the end of their lifetime and end up on the landfills and in the ocean. There is, however, a good reason—actually, many good reasons—why polyethylene is one of the most produced materials in the world, and this review discusses various useful applications stemming from the unique material properties of polyethylene. Some of the emerging applications of polyethylene hold high promise for sustainable energy generation from renewable sources and for sustainable management of planetary energy and water resources. Light weight and corrosion resistance of polyethylene, combined with its unique infrared transparency and heat transfer properties, which can be engineered to span between the near-perfect insulation and metal-like conduction, are at the core of new technological applications of a not-so-old material.

(Invited) Electrically Conductive Silver Nanowire Coatings on Textiles for Personal Thermal Management

Protection from arctic cold weather has been an ongoing need in military clothing. Current garment systems are problematic due to overdressing, poor moisture management, discomfort following strenuous activity, loss of dexterity and risk of pain and frostbite. All these challenges must be balanced to improve the mobility of Soldiers while reducing pain, hypothermia, and risk of frostbite. In this work, we develop an electrically conductive coating for military uniform fabrics based on synthesized networks of silver nanowires (AgNWs). The nanowire network provides thermal insulation through increased infrared (IR) heat retention as well active Joule heating of the fabric. Long silver nanowires were synthesized using the polyol method where silver nitrate is reduced in the presence of iron chloride seeds, ethylene glycol, and polyvinyl pyrrolidone. Different fabrics including polyester, polypropylene, cotton, and NyCo (50/50 blend of cotton and nylon) were coated with the nanowire ink, and thermal properties were examined. Fourier Transform Infrared (FTIR) spectroscopy revealed a highly thermally insulating coating with an IR reflectance of ~24 % for 100% cotton. Joule heating experiments were carried out and revealed that the temperature of the AgNW-coated textile could be increased by up to 109 °C with 3 V in under one minute. The sheet resistance of the coated fabric was measured using a IV-point probe and found to be significantly lower than the sheet resistance of untreated fabric suggesting the development of a highly conductive textile. Thermal images were also studied and thermal radiation of AgNW-coated fabric was decreased by ~3 °C, indicating that the coated textile appeared cold while being worn. The moisture vapor transmission rate (MVTR) of the coated fabric was investigated and results suggested that coating the different material fabric with AgNW networks does not affect the breathability of the textile since no significant changes in MVTR were observed for any of the fabrics. The results of our research suggest that AgNW-coated textiles could provide passive and active thermal management solutions to offer Soldiers protection from extreme climatic operating environments.

Quick pyrolysis of a massive coal sample via rapid infrared heating

There are few studies about pyrolysis with the a massive sample at high heating rates to obtain liquid and gas products. This study adopted a newly designed small fixed bed reactor mounted with infrared heating to minimize secondary reactions to volatiles and further to investigate the pyrolysis of Xinjiang Naomaohu coal in terms of pyrolysis products characterization at different temperatures and heating rates. Infrared heating has good penetrability to heat the inner layer of the sample at a quick rate of up to 1723 °C/min in the particle bed. For the tested reactor at 700 °C, raising the heating rate decreased the yields of gas and char and increased the yield of tar. The realized tar yield was higher than that in Gray-King (G-K) assay at heating rates above 18 °C/min. For the heating rate of 667 °C/min at the pyrolysis temperature of 700 °C, the obtained maximum yield of tar was 134% of the G-K assay oil yield. Overall, increasing the heating rate decreased char yield and increased the production of total volatiles. At higher heating rates, the tar became heavier, while at higher pyrolysis temperatures, it produced more light tar. The extraction rate of hydrogen from coal was found to be subject to a linear relationship with pyrolysis gas yield.

A nano-photonic filter for near infrared radiative heater

Infrared (IR) radiative heating is a highly desirable method for heating as compared to convective heating due to the unprecedented control of radiative energy transfer, leading to a significant increase in energy efficiency. The greatest challenge however with IR radiative heating is its low penetration depth due to the strong IR absorption by the water content in the substance to be heated. Near IR (NIR) heating can circumvent this problem as it has greater penetration depths. The proposed nano-photonic design for NIR filter (or effective selective emitter) has transmissivity of more than 70% in NIR and less than 15% in both visible and IR wavelengths as opposed to currently available IR heaters, which have high emissivity across all wavelengths. This NIR filter can be applied to any radiative heating source to transform it into a NIR radiative heater. We demonstrate this with a simple prototype by applying it in front of tungsten-based incandescent lamp where significant reduction in white glow (glare) was observed. Potential application of this NIR filter would be in heating in both building and industrial sectors where the ability to provide localized heating could lead to significant energy savings. In addition, NIR selective emitters can be applied for power generation by supplying thermophotovoltaics (TPV) with photons at the right wavelengths, which will increase the efficiency of TPV.

Quasi-static mechanical properties of tomato peels produced from catalytic infrared and lye peeling

This study investigated the quasi-static mechanical properties of tomato peels of three cultivars - Hz 5608, Seminis DRI 319 and Seminis HP 849. The peels were produced from infrared (IR) heating with three targeted tomato surface temperatures of 109, 112 and 115 °C at two loading rates which reflected the different heating rates. Peels from conventional lye peeling method using a solution of 10% NaOH at 95 °C were used for comparison. Fresh tomato peels were used as control. A texture analyzer was used to determine the tensile strength to failure, puncture resistance strength, and adhesive strength of peels. It was found that mechanical strengths of tomato peels obtained from both IR and lye peeling processes were significantly (α = 0.05) lower than those of the control. However, the mechanical strengths of tomato peels under IR treatment at the temperatures of 109 and 112 °C were significantly (α = 0.05) higher than those of the peels obtained from lye treatment. The mechanical strength of the peels produced from IR treatment at 115 °C was similar to those produced from lye treatment. The reductions in tensile, puncture and adhesive strengths of peels were up to 88, 87.3 and 74.3%, respectively, for IR heated tomatoes, whereas these were 95.1, 99.3 and 91.3%, respectively, for lye treated tomatoes compared to control. The peels obtained from IR peeling had more integrity than those obtained from lye peeling. Increasing the loading rates of tomatoes during IR heating corresponding to lowered heating rate significantly (α = 0.05) decreased the mechanical strengths of peels due to increased residence time for reaching the targeted temperatures. Tomato cultivars had a significant (α = 0.05) effect on the adhesive strength of peel but not on tensile and puncture resilience strengths. These results provide important information about the changes of mechanical properties of tomato peel under different processes.

Transparent wood bearing a shielding effect to infrared heat and ultraviolet via incorporation of modified antimony-doped tin oxide nanoparticles

Optically transparent wood (TW) is an emerging candidate for applications in energy efficient buildings. In this study, anti-ultraviolet and infrared heat shielding TW was prepared based on the delignification of the wood's substrate. This was followed by infiltration of pre-polymerized methyl methacrylate (PMMA) with modified antimony-doped tin oxide (ATO) nanoparticles. The ATO addition enhanced the interfacial bonding among the compounds, which improved the fracture strength, leading to a high fracture strength of 96.4 MPa and modulus of 4.27 GPa with addition of 0.3% ATO. Furthermore, the obtained ATO/TW exhibited high transparency, excellent near infrared (NIR) heat shielding performance, and ultraviolet (UV) shielding properties according to the ultraviolet–visible spectrophotometer measurement, the infrared heat shielding simulation test, and the UV-shielding test. The TW treated with 0.3% ATO still maintained a very low thermal conductivity of around 0.2 W m−1 K−1. After addition of 0.7% ATO, the obtained TW had a quite low UV transmittance of ＜20%. The Aspergillus niger maintained high viability after UV irradiation treatment when shielded with TW treated with 0.7% ATO. The findings indicate that the multifunctional and durable ATO/TW has a potential to be used as energy-saving building material.

The effects of infrared treatment on physicochemical characteristics of vegetable soybean

Vegetable soybean (Edamame) blanching with hot water/steam is an energy- and water- intensive process that may also result in compromised product quality. The effectiveness of infrared (IR) heating to dry and simultaneously blanch Edamame was investigated at heating intensities of 11.06, 8.43 and 6.99 kW/m2. Temperature, weight, texture, and green intensity of heated samples for various durations were determined. In general, product weight decreased during IR heating. The largest weight reduction (9.5 %) was achieved after 100 s of heating at the highest IR heating intensity. Hardness was reduced alongside treatment duration, reaching the lowest values (11172.9–10847 N) at 100 or 120 s despite heating intensity. The highest green intensity was recorded (0.33) for treatments at 100 or 120 s. The new process combined drying and blanching into one step which potentially improves processing efficiency and product quality.

Influence of dynamic temperature control on the injection molding process of plastic components

Conventional injection molding (CIM) technology has been largely used to produce plastic parts, mainly on automotive industry, due to high production ratios, constricted dimensional tolerances production, and low labor costs. Nowadays, industry has been demanding for thinner and lighter molded parts production, with better mechanical properties. Low mold temperatures (≈60ºC) are used to decrease the cycle molding time and process final costs. However, the fast cooling of parts can easily result in surface defects, such as weld lines, sink marks, or warpage. To avoid such defects and eliminate the need for secondary operations (additional operating costs), a dynamic mold heating and cooling control technology known as Rapid Heating and Cooling Molding (RHCM) can be employed. Based on RHCM, this study compared the efficiency of using heating rods, water flow, and external infrared heating systems to investigate the effect of dynamic temperature control on the injection molding process. An experimental injection mold was manufactured and used for the studies under controlled conditions to produce standard tensile and flexure specimens. The effect of process parameters, geometry of the runner system, location of the injection point, and other relevant settings was considered. From this study, new insights were obtained regarding the industrial application of RHCM as well as the degree of efficiency of different design solutions for the RHCM process.

Integrated Gripping-system for Heating and Preforming of Thermoplastic Unidirectional Tape Laminates

Forming and overmolding of thermoplastic multi-layer UD-tape laminates has become increasingly important due to its potential for large-scale production. In the process the tape laminates have to be heated above melting temperature of the polymer in an infrared heater and then transported into the mold. To guarantee the formability of the laminate the temperature has to be maintained above the melting temperature during handling. To improve part quality a preforming of the tape laminate prior to overmolding is preferable. Integration of the preforming step in the handling process allows the shortening of the process route. In this work a gripping-system which allows further heating and preforming of the laminate during the handling process is presented. The temperature losses during transport have been modelled using the Stefan-Boltzmann law. By means of temperature measurements it is shown, that the integrated infrared-heaters allow a compensation of the cooling during handling, resulting in lower maximum heating temperature in the upstream infrared heating field and therefore a reduction of heating time and degradation of the polymer. The repeatability of the handling-integrated preforming has been evaluated using three-dimensional overlays of the resulting 3D-shaped laminates acquired by a laser scanning arm.

Investigation of a rapid infrared heating assisted mineralization of soybean matrices for trace element analysis

A fast sample preparation procedure based on use of infrared (IR) assisted heating for mineralization of soybean derived samples has been developed for their subsequent multielement analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectrometry (FAAS). A cold finger was examined for refluxing of acid vapors to determine its impact on efficiency and economy of digestion. The optimized procedure, based on 1 g subsamples, 8 mL of HNO3 (65% w/w) and exposure of the mixture to a 500 W IR source for 5 min without refluxing, permitted accurate determination of all analytes in NIST SRM 1568b (rice flour). Detection limits using ICP-OES were (µg/kg) 97, 1.0, 39, 185, 0.47 and 1200 for Ca, Cu, Fe, K, Mn and P, respectively, and 18 for Zn by FAAS. The IR-assisted digestion approach provided a low cost, easy to use system having great potential for implementation in routine analysis of trace elements in soybean and similar matrices.

Tomato peeling performance under pilot scale catalytic infrared heating

Steam and lye peeling methods have been the most commercialized methods in tomatoes industry. However, they are water and energy intensive and have adverse effects on the environment. The infrared (IR) dry-peeling was studied as a sustainable tomato peeling method because it does not require water nor chemicals. An IR peeling system equipped with catalytic IR emitters was designed and constructed. The peeling performance of the system, in terms of peelability, peeling loss, and product quality, was examined under different loading rates using the tomatoes cultivars, Hz 5608, Seminis DRI 319, and Seminis HP 849. Peeling performance was significantly (α = 0.05) affected by surface temperature of tomatoes during IR heating. A tomato surface temperature range of 109–115 °C (±2 °C) during IR heating was found to be optimum for achieving a good peeling performance. Compared to conventional lye peeling, IR dry-peeling produced up to 38.2% firmer peeled tomatoes and up to 12.2% lower peeling loss with a similar or better peeling easiness and more desirable color of the peeled tomatoes.

Lethal effects and mechanism of infrared radiation on Sitophilus zeamais and Tribolium castaneum in rough rice: Poster

The objective of this study was to investigate the characteristics of adult Sitophilus zeamais and Tribolium castaneum, and the 21.1% dry base (d.b.) MC of rough rice by ATR-FTIR spectra, and determine the theoretical optimum infrared (IR) heating temperature of the tested samples. In laboratory experiments, a ceramic IR drying device was used to heat infested rough rice to research the mortality of Sitophilus zeamais and Tribolium castaneum, the drying characteristics of rough rice, and milling quality. The theoretical calculation optimum temperature of IR heating was 300 °C according to the results of FTIR spectra. In addition, the effects of the different IR radiation intensities and heated rough rice temperatures on mortality of insects, moisture removal, and milling quality were determined in this text. A high insect mortality, heating rate and corresponding high moisture removal were achieved by using IR heating. After heating, tempering process significantly increased insect mortality when the heated tempered rice temperature was less than 55 °C, and improve moisture removal and milling quality of rough rice during nature air cooling. When the rice heated under the IR radiation intensity of 2780 W/m2 for 110 s, the rice temperature reached 60.2° ± 0.5°C, 100% mortality of S. zeamais and T. castaneum, and 3.97 percentage points of moisture removal during the heating period after tempering and natural cooling. In addition, the high rice milling quality can be achieved after tempering treatment. Therefore, it can be concluded that the optimum conditions of simultaneous disinfestation and drying were 60 °C rice temperature under the IR radiation intensity of 2780 W/m2, followed by tempering and natural cooling.

Effects of IR heating on distribution and transport of gaseous air pollutants in urban and mountain churches in Poland

Abstract The spatial distribution and temporal concentration variation of a set of gaseous air components (e.g., CO2, CO, H2CO, H2O) have been monitored with a multi-channel photoacoustic gas-analyzer in an urban church (Saint Catherine's, Cracow) and a mountain church (Saint Michaels Archangel, Szalowa) of Poland, in order to assess the likely effects of air pollution indoors under the influence of provisory electrical infrared (IR) heaters and without heating. Likewise, the ventilation characteristic and the leakage of these buildings with different constructions (i.e., plastered stone and wooden structures) with the assistance of decay curves of SF6 tracer gas was evaluated and compared. The wooden building in Szalowa, due to its more open structure, developed about one order higher ventilation rates (e.g., 0.9–1.3 h−1) than the stone church in Cracow (e.g., 0.1 h−1). The IR-heating affected only modestly the ventilation rate of the wooden church (e.g., 1.2–1.6 h−1), but it increased significantly that of the plastered stone church (e.g., 0.27 h−1). The ventilation rates were also assessed with the use of the CO2 curve decay method, and satisfactory agreement was found with those observed by the use of SF6 tracer. The spatial distribution of the studied gaseous pollutants (CO2, H2O) was found to be in some occasions nonhomogeneous in both buildings, due to the active usage of the IR-heating, especially, during a couple of consecutive liturgical services. Besides the pollution events due to ingress of gaseous air pollutants, present at enhanced levels outdoors, increased CO, CO2 and H2CO peaks were observed indoors too, which, in most cases, could be associated with incense burning.

Peeling of kiwifruit using infrared heating technology: A feasibility and optimization study

Infrared (IR) technology has been studied as an alternative to conventional food processing technologies. The IR technology has attractive merits such as uniform heating, high heat transfer rate, reduced water, and energy consumption and improved product quality and safety. This research studied the feasibility of kiwifruit peeling using IR heating. The response surface methodology (RSM) was used to investigate the effects of IR radiation power (250–850 W), the distance between IR emitter and sample (10–70 mm) and heating time (45–125 s) on the peeling performance and physicochemical properties of kiwifruit. Lye-peeling was used as the control treatment to compare the efficiency of IR peeling. Heating with a power of 446 W at the distance of 70 mm for 125 s was found to be the optimum operating conditions for the IR peeling of kiwifruit. Under these conditions, the results were a peelability of 90%, weight loss of 4.5%, peel thickness of 0.4 mm, surface temperature of 64.1 °C, puncture force of 57.7 N, color difference of 2.4 and ascorbic acid content of 140 mg/100 g fresh fruit. Compared to hot lye peeling, the IR radiation heating caused significant reduction in weight loss, surface temperature, and color differences. It also maintained the firmness of fruits.