Heating Wire Research Articles

In-plane thermal conductivity measurement of microscale polymer films using a reusable micro-thermocouple

Polymers serve as encapsulating materials for electronic devices, making it crucial to investigate their thermophysical properties. In this work, a novel 2ω method for assessing the in-plane thermal conductivity of polymer films is proposed. A reusable micro-thermocouple, serving as both a heating wire and a sensor, is used with silver paste as the interstitial material in contact with the test film. By comparing the 2ω voltages under both contact and non-contact conditions, the thermal impedance is determined. The thermal conductivity is directly calculated by determining the slope of the real part of the thermal impedance against the logarithm of frequency. Theoretical analysis shows that the influences of contact thermal resistance and radiation heat loss are negligible. To validate the accuracy of the method, measurements were repeated on polyimide and polyester films under various contact conditions. The results demonstrate consistency and align with those obtained using the laser spot periodic heating technique.

Fabrication of SNAP structures by wire heating.

Surface Nanoscale Axial Photonics (SNAP) is a promising technological platform for creating novel optical devices such as compact high-Q tunable delay lines, signal processors, and optical comb generators. For this purpose, the development of simple and reliable methods for the accurate introduction of a nanometer-scale variation of the optical fiber surface is desirable. Here, we present an easy-to-implement technique for the introduction of nanoscale variations of the effective optical fiber radius by annealing with a heated metal wire. Using the proposed method, we introduce modifications of the fiber effective radius with accuracy better than 0.1 nm without post-processing, making the proposed approach the simplest alternative to the previously developed SNAP fabrication techniques.

Experimental investigation of a distributed photovoltaic heating system based on building envelope thermal storage

Low-carbon heating in farmhouses can be achieved using photovoltaic (PV) heating. However, the severe mismatch between the PV energy supply and the building thermal load requires expensive energy storage devices and control systems. In this study, a controller-less PV heating system utilizing the building envelope for thermal storage was evaluated on a farmhouse in northern China. The building envelope simultaneously functions as the heating terminal and is composed of insulation boards, electric heating wires, and the thermal storage wall. PV electricity is fed to be absorbed by the electric heating wire to produce heat. The thermal storage wall absorbs the heat generated by the heating wire before releasing it into the room through convection and radiation. Long-term monitoring reveals that the black bulb temperature of the farmhouse was above 16 °C for more than 60 % of the time throughout the heating season. The building envelope acting as a thermal reserve improved system supply and demand matching by 77 % and the indoor temperature fluctuation was reduced by about 47 %. The thermal storage wall can provide 58 % of the heating energy when there is no PV power supply. The payback period of the heating system is only 6.5 years, verifying the good rate of return of the system. This study proposes a lower cost energy storage solution for PV heating than previous studies, and engages the building envelope into the building energy system.

Experimental study on snow melting and deicing of carbon fiber heating roads considering thermal insulation conditions

The electrothermal method for snow melting and deicing in road engineering provides efficient deicing. To improve the ice melting efficiency of carbon fiber heating cables, employing extruded polystyrene foam board (XPS)、polyethylene foam cotton (PEF) as insulation materials under the carbon fiber heating wire could reduce heat transfer to the lower layers of the road structure. Road model tests were conducted under various conditions to analyze how different heat insulation conditions、environmental temperatures affect road snow melting and ice melting. The results indicate that the placement of the heat insulation layer significantly affects the temperature fluctuation range between its upper and lower layers.The ice melting rate increases by 25∼50 % compared to pavement structures with no heat insulation layer. When heat insulation material is incorporated into the road structure layer, under preheated conditions, snow with a thickness of 0.2 cm on the surface of the plate heat insulation model can completely melt within 2.5 h, reducing the effective ice-melting time by 40∼51.7 %. A comparison of the thermal performance of the two insulation materials under various conditions reveals that the XPS plate is more suitable as an insulation layer compared to other materials.

The Implementation and Comparison of Conventional and Enhanced Borehole Thermal Response Tests: A Case Study

Ground source heat pump (GSHP) systems depend on the capacity for heat transfer between the system and the ground, and it is good practice to carry out an in situ thermal response test (TRT) to determine the undisturbed ground temperature, the thermal conductivity of the ground, and the thermal resistance of the borehole. Conventionally, a TRT is undertaken in a replica borehole heat exchanger (BHE); however, alternative methods have been developed that can provide continuous depth-resolved temperature recordings. The enhanced TRT (ETRT) uses a hybrid cable system which incorporates a resistance heating wire to provide a linear heat source and a fibre optic cable to measure the temperature along the length of the borehole. In this paper, a case study is presented in which a TRT and ETRT were carried out in the same BHE to evaluate its thermal response and estimate the thermal characteristics of the ground. After a brief introduction of both methods and their interpretation, a comparison between them is presented regarding their advantages and disadvantages using the results of the performed tests, which revealed an 8% difference in the soil thermal conductivity values, averaged over the length of the BHE.

Design and Implementation of an Ice-Tethered Observation System for Melt Pond Evolution with Vision and Temperature Profile Measurements

Melt pond is one of the most significant and important features of Arctic sea ice in the summer and can dramatically reduce the albedo of ice, promoting more energy into the upper ocean. The observation of the seasonal evolution of melt pond can improve our fundamental understanding of the role and sensitivity of sea ice in the context of global climate change. In this study, an ice-tethered observation system is developed for melt pond evolution with vision and temperature profile measurements. The system composition, structure of the ice-tethered buoy, freeze-resistant camera, and thermistor chain are analyzed. A sealed shell and electric heating wires are used to increase the temperature to around the camera in low-temperature environments. The ice thickness and depth of melt pond can be inverted using a specific interface recognition algorithm. A low-light image enhancement strategy is proposed to improve the quality of images under the low lighting conditions in polar regions. The proposed system was tested in the second reservoir of Fen River, Yellow River, from 15 January to 27 January 2021. An artificial freshwater pond was used as the location for thermistor chain deployment and observation. The differences in mean square error (MSE), peak signal-to-noise ratio (PSNR), and feature similarity index (FSIM) between the original and enhanced images indicate that the proposed algorithm is suitable for low-light image enhancement. The research on the ice-tethered observation system will provide a new framework and technical support for the seasonal observation for melt pond.

Development and Application of Shape-Memory Polymer and Alloy Composite Sheets

The authors previously developed a flexible and multi-degree-of-freedom pneumatic artificial rubber muscle that uses shape-memory polymer (SMP) sheets with an embedded electrical heating wire. The bending direction and initial shape of the muscle can be changed by utilizing the large difference in the elastic modulus below and above the glass transition temperature, shape fixity, and shape recovery of SMPs. In this study, to improve performance, we propose a shape-memory composite (SMC) sheet that consists of SMP sheets with an embedded shape-memory alloy (SMA) wire used as an electric heating wire. The mechanical properties of the previously developed SMP sheets and the proposed SMC sheets are compared through shape recovery, bending, and tensile tests using prototypes. The motion of the artificial muscle with various samples attached is evaluated through an isometric test and bending angle measurements. The experimental results confirm that the use of the SMA wire improves the production reproducibility and shape recovery of the SMP sheets without degrading other mechanical properties or actuator performance.

Field experiment examining condensation reduction methods based on underground parking lot types

ABSTRACT In this study, condensation reduction methods with high field applicability to various types of underground parking lots in apartment buildings were selected and tested. The selected methods included floor-insulating drainage plates, induction fans with heating wires, and an automatic control ventilation system based on indoor and outdoor temperatures and humidity. The effectiveness of these methods was evaluated via real-world field experiments. The results indicated that while the insulating drainage plates initially blocked the cold, their long-term effectiveness matched that of normal drainage plates (difference 0.1°C). The induction fan with a heating wire showed average increases of 0.8°C and 2.7°C in wall surface temperature after one and three months, compared to normal induction fans. The absolute humidity of the automatic control ventilation decreased by 1.8 g/kg after 10 h of operation during rainy weather, whereas the manual control ventilation system increased by 0.6 g/kg under the same conditions. This study offers insights into the most effective application of these methods for various parking lot configurations.

Electrothermal-assisted all-weather solar steam generator based on hydrogel implantation strategy

Using solar energy to treat sewage is a feasible scheme to alleviate the shortage of water resources and reduce carbon emissions. However, the fluctuation of sunlight intensity poses a great challenge to the stability of the treatment process, which hinders its application in the actual water treatment scene. Herein, based on the adhesion of hydrogel, an electrothermal-assisted all-weather solar steam generator with sandwich structure was synthesized through hydrogel implantation strategy, in which polyacrylamide hydrogel with thermal grease-modified heating wires was implanted as the middle heat conduction layer, the photothermal evaporation layer as the upper layer and the waste heat evaporation layer as the bottom layer. The electrothermal assisted solar evaporator (EASE) perfectly achieves the superposition of photothermal and electrothermal effects, and can achieve high interfacial water evaporation performance under extremely low auxiliary working voltage. Applying a low voltage of 2 V to both ends of the evaporator can achieve a high evaporation rate of 4.58 kg m−2h−1 under 1 solar irradiation, which is similar to the sum of the evaporation rate under only 1 solar illumination (2.22 kg m−2h−1) and a 2 V voltage input (2.26 kg m−2h−1). More interestingly, the suitable thickness of the hydrogel layer not only ensures the transfer of heat between layers, but also weakens the heat loss caused by the water flow effect. The implantation strategy ensures the stability of the water structure and inhibits the hydrogen reaction of electrolytic water in the electrothermal process. This work provides an important theoretical and practical reference for the preparation of all-weather solar interface water purification equipment.

Properties Enhancement of Metal Additive Manufactured Part via Cold Deformation Process

Wire-arc additive manufacturing is a method of 3D printing metal using welding techniques. However, due to heat, the mechanical properties of the deposited material may be affected. Various methods have been proposed to mechanically improve the properties. In this study, cold deformation was introduced to enhance the properties. The effects of a few parameters, including welding speed, wire feed rate, heat input, thickness ratio, and types of material, were studied. Based on the result, the hardness, tensile, and wear properties of the manufactured part improved, while other properties, like impact toughness, had a lower value. Based on the preliminary result, cold deformation shows potential alternatives for part repair or reconstruction of worn or broken parts.

Numerical study on natural convection heat transfer of supercritical CO2 in an infinite space

A numerical study of natural convection heat transfer from horizontal heating wire to supercritical carbon dioxide (sCO2) in an infinite space was performed. The qw ∼ ∆T curves of sCO2 natural convection heat transfer were calculated in a wide range of parameters, where initial bulk temperature (Tib) and operating pressure (P) varied in the range: 275 K < Tib < 345 K and 7.5 MPa < P < 11 MPa, respectively. Then, we reported from the viewpoint of pseudo-phase transition for supercritical fluids, the characteristics and mechanism of sCO2 natural convection heat transfer were revealed through comparing with qw ∼ ∆T curve of subcritical pool boiling. The similarity between film-like heat transfer at Tw > Tpc for supercritical pressure and film boiling at Tw > Tsat for subcritical pressure was demonstrated. The influence of operating parameters such as Tw, Tib, and P on sCO2 heat transfer was also discussed. For supercritical film-like heat transfer, thermal resistance of film-like which reflects the effect of gas-like film thickness and its thermal conductivity on heat transfer was proposed. Expectedly, the variation of thermal resistance explained successfully the difference of sCO2 heat transfer under different operating parameters. The investigation is of paramount importance in comprehension of sCO2 heat transfer mechanism for designing heat exchanger component in the advanced sCO2 application.

P‐62: Fast Response LCD under Low Temperature Environments Using In‐cell Heater Wires

One of the challenges inherent in automotive LCD relates to the response characteristics displayed in low‐temperature environments. In this study, we devised a panel by incorporating heater wires into the Thin‐Film Transistor (TFT) substrate of the LCD, which was optimized through thermal simulations. Additionally, we validated the enhanced response time in low‐temperature environments by utilizing the optimized heater wires within the LCD cell for automotive applications.

Research on the Strength Characteristics of Thermally-Stabilized Loess by Microwave and Resistance Wire Heating

Research on the Strength Characteristics of Thermally-Stabilized Loess by Microwave and Resistance Wire Heating

Experimental and theoretical research on the temperature evolution law of overcurrent fault wires

AbstractTo investigate the problems of overload and excessive thermal insulation associated with building electrical fires caused by wires, a theoretical model of wire heat transfer is established, and the pyrolysis and combustion phenomena of the insulation layer are analyzed. The results showed that the temperature evolution of the wire underwent three stages: constant temperature, insulation heating, and high‐temperature pyrolysis. The insulation layer experiences bulging, exhausting, carbonization, dripping, and burning in sequence, and insulation layer dripping requires at least 160 A of current. As the current increases, the temperature increase rate of the wire increases gradually, and the fusing time of the wire gradually decreases. Under the same current, 160°C is the turning point at which the temperature increases. The temperature increase rate of the copper wire is greater than that of the aluminum alloy wire, and the temperature increase rate of the bare wire is greater than that of the insulated wire. The fusing time of an aluminum alloy wire is less than that of a copper wire, and the fusing time of a bare wire is less than that of an insulated wire. The research results provide theoretical guidance for the prevention and investigation of building electrical fires.

Discrete element analysis of heat transfer characteristics of concrete pavement under electrical heating for snow melting and deicing

The carbon fiber electrothermal method is an efficient approach for snow melting and deicing of pavements in the cold winter. The heat transfer mechanism needs to be explored for the carbon fiber electrothermal system design, especially how the microstructure affects the thermal behavior of pavement. To do so, a discrete element method (DEM) based heat transfer model considering the pavement microstructure has been established in the current study. The shape and content of coarse-grained aggregates have been represented by using the irregular polygonal aggregate method. The accuracy and feasibility of the proposed model were verified by comparing the numerical results with the measured data. On this basis, the heat transfer characteristics of pavements during snow melting and deicing using the carbon fiber electrothermal method have been investigated. The results show that the ambient temperature and the carbon fiber heating wire (CFHW) temperature are the two primary factors affecting the heating efficiency and the maximum temperature on the pavement surface. The spacing and buried depth of the CFHW also play a crucial role in determining the temperature rise rate and the uniformity of temperature distribution of the road surface layer. Furthermore, the effect of the aggregate content on the overall heating rate is not as significant as that of the specific heat capacity ratio of the aggregate to the mortar, suggesting modifying the thermal conductivity of aggregates to enhance deicing efficiency rather than changing the aggregate contents. The effects of the CFHW design parameters on the temperature distribution of the pavement surface are also investigated. The maximum and minimum temperatures of the pavement layer decrease gradually with the increase of the laying spacing and burial depth of the CFHW, but the temperature difference increases with the increase of the laying spacing of the CFHW and decreases with the increase of the burial depth. The research results can provide a reference for the optimization design of snow melting and deicing of pavements by the CFHW heating method.

Heat transfer error analysis of high-temperature wall temperature measurement using thermocouple

Thermocouples are widely employed as the temperature measuring element for an aero-engine. However, due to the unique characteristics of the aero-engine test environment, there exist significant temperature measurement errors of the thermocouple. The steady-state heat transfer error of the thermocouple can be attributed to convection heat transfer error, wire heat transfer error, and radiation heat transfer error. The flow and heat transfer process of wall temperature measurements using armored K-type thermocouples were simulated numerically by Fluent software at the Mach number of 0.1–0.5 and the temperature of 700∼1200 K. The results indicate that convective error accounts for more than 55 % of the total transfer error. To reduce excessive temperature measurement errors, a novel airflow stagnation cover structure around the thermocouple was presented. When the diameter of the stagnation cover is 2 mm, the error of the thermocouple is reduced to less than 1 %.

Simultaneous measurement of thermal conductivity and emissivity of micro/nanomaterials

Although thermal conductivity of micro/nano scale material has been readily measured, the high specific surface area leads to non-negligible radiative heat transfer. Here, a method for simultaneous measurement of intrinsic thermal conductivity and emissivity of micro/nano materials was developed and verified. The physical model of this measurement principle consisted of two parallel platinum wires, which serve as both heaters and heat flux meters. Thermal conductivity and emissivity can be derived by comparing the changes in the average temperature rise of the heater and sensor platinum wires before and after attaching the test sample. The thermal conductivity and emissivity of an individual platinum wire were determined to 71.7 W/(m·K) and 0.14, which are consistent with the reference values. Subsequently, the thermal conductivity and emissivity of the polymer composite fiber were measured to be 1.45 W/(m·K), 0.73 and 1.87 W/(m·K), 0.8 at different composite filler concentrations. In principle, this method is applicable for accurately measuring the thermal transport properties of any micro/nano wires using appropriate sensors.

Isoprenoid emissions from Schima superba and Cunninghamia lanceolata: Their responses to elevated temperature by two warming facilities

Isoprenoids (including isoprene (ISO) and monoterpenes (MTs)) are the majority of biogenic volatile organic compounds (BVOCs) which are important carbon-containing secondary metabolites biosynthesized by organisms, especially plant in terrestrial ecosystem. Results of the warming effects on isoprenoid emissions vary within species and warming facilities, and thus conclusions remain controversial. In this study, two typical subtropical tree species seedlings of Schima superba and Cunninghamia lanceolata were cultivated under three conditions, namely no warming (CK) and two warming facilities (with infrared radiators (IR) and heating wires (HW)) in open top chamber (OTC), and the isoprenoid emissions were measured with preconcentor-GC–MS system after warming for one, two and four months. The results showed that the isoprenoid emissions from S. superba and C. lanceolata exhibited uniformity in response to two warming facilities. IR and HW both stimulated isoprenoid emissions in two plants after one month of treatment, with increased ratios of 16.3 % and 72.5 % for S. superba, and 2.47 and 5.96 times for C. lanceolata. However, the emissions were suppressed after four months, with more pronounced effect for HW. The variation in isoprenoid emissions was primarily associated with the levels of Pn, Tr, monoterpene synthase (MTPS) activity. C. lanceolata predominantly released MTs (mainly α-pinene, α-terpene, γ-terpene, and limonene), with 39.7 % to 99.6 % of the total isoprenoid but ISO was only a very minor constituent. For S. superba, MTs constituted 24.7 % to 96.1 % of total isoprenoid. It is noteworthy that HW generated a greater disturbance to physiology activity in plants. Our study provided more comprehensive and more convincing support for integrating temperature-elevation experiments of different ecosystems and assessing response and adaptation of forest carbon cycle to global warming.

Entire mechanical analysis of prestressed CFRP strengthened RC beams under different prestressed introduced methods

In order to clarify the effect of mechanical tensioning and SMA wire heating recovery on introducing prestress into CFRP sheet strengthened reinforced concrete (RC) beams, an experimental research on the bending performance of prestressed CFRP sheet strengthened RC beams was conducted. Based on the test results, a bending carrying capacity model for RC beams externally strengthened with prestressed CFRP sheets was proposed. The model provides calculation methods for the decompression moment, cracking moment, yielding moment, and ultimate moment, corresponding to different failure modes of the RC beams strengthened with externally bonded prestressed CFRP sheets. Four experimental beams were designed to verify the accuracy of the model with the prestresses of 100 MPa and 200 MPa. The results show that during the yield stage and strengthening stage, the loading-unloading stress-strain relationship curves of SMA wire under different prestrains are basically consistent. When the prestrain of SMA wire is 10%, the maximum recovery stress reaches 448.5 MPa. Under the same prestrain conditions, the maximum recovery stress of CFRP sheets was reduced by 37.8–39.5% when the prestress was introduced through heating recovery of SMA wires. The failure mode of mechanically tensioned prestressed CFRP sheet strengthened beams is the CFRP sheet debonding caused by mid-span bending cracks, while the failure mode of strengthened beams with prestressed CFRP sheet by SMA wire heating recovery is the CFRP sheet end debonding. The cracking moment and yield moment of the strengthened beams are significantly increased by two methods of introducing prestressing. The stiffness improvement of mechanically tensioned prestressed CFRP sheet strengthened beam is relatively large. While, the prestressed CFRP sheet strengthened beam by SMA wire heating recovery gradually experience end peeling failure of the CFRP sheet, and the prestressing effect does not effectively limit the development of cracks, resulting in limited stiffness improvement. The calculation results are in good agreement with the experimental results, proving that the proposed method for analyzing the entire bending process can be used to predict the bending mechanical properties of the prestressed CFRP sheet strengthened beams.

Design of an electric activation system for the smart hybrid tendons crack-closure system in concrete beams.

This work presents the design of a smart activation system for the crack-closure technology of the Hybrid Tendons. Previous research has demonstrated the effectiveness of this technology in providing a self-repairing mechanism for concrete elements. The Hybrid Tendons are made combining a pre-stressed Kevlar inner core restrained by a Shape Memory Polymer sleeve. To trigger the crack-closing action, the Shape memory potential of the outer sleeve needs to be activated via heating. The work focuses on the design and testing of an electric activation system for the Hybrid Tendons using a system of heating wires. Kanthal wires are chosen for this application and integrated in the manufacturing process of the Hybrid Tendons: the wires are wrapped around each tendon and connected to a power supply. An experimental campaign is conducted to assess the system's capability to activate the Hybrid Tendons and deliver the crack-closing action in concrete beams under constant load. Additionally a numerical model is also developed to offer a sound interpretation of the experimental results. The system is ultimately proven successful in activating the Hybrid Tendons embedded in the concrete, effectively delivering the crack-closing action and boosting the flexural response of the structural element.