Self-generated Heat Research Articles

The photothermal effect enhance visible light-driven hydrogen evolution using urchin-like hollow RuO2/TiO2/Pt/C nanomaterial

The photothermal catalysis has attracted much attention as a new catalytic method. Utilization of self-generated heat instead of external heating source is an ideal approach for improving the performance of catalysts. Herein, a novel urchin-like hollow TiO2 photothermal nano-catalyst with spatially separated Pt and RuO2 dual cocatalysts combine with carbon layer (denoted as RuO2/TiO2/Pt/C) is reported for catalytic hydrogen evolution under visible light irradiation. The photothermal catalytic performance of the as-prepared catalysts was evaluated in relation to structural characterizations and the thermal effect of the carbon layer. The sandwich nanostructure of carbon layer, Pt NPs and TiO2 layer effectively support and protect Pt NPs from agglomeration and deactivation of Pt active sites. The hot electrons generated from carbon layer can participate in the photocatalytic reaction. Furthermore, the enhanced visible light absorption performance of TiO2 is explained by narrowing the band gap due to a small amount of doping carbon and reducing the penetration-loss of light via constructing the hollow structure. As a result, the synergy between the spatially separated Pt/RuO2 NPs and the thermal effect with carbon layer greatly improve the catalytic performance of the TiO2-based catalyst for hydrogen production under visible light irradiation.

Experimental study on the influence of different heating methods on thermal runaway of lithium-ion battery

Due to the fact that lithium ions are subjected to different thermal abuses during services, this paper introduces heating of lithium-ion batteries with different State of Charge (SOC) by means of a spring heating ring and a cylindrical heating rod. The results show that with the increase of SOC, the thermal runaway phenomenon of lithium-ion battery increases dramatically. Under the same SOC, owing to the better heat transfer efficiency of the spring heating coil and the more uniform internal heating of the battery, the temperature of the battery heated by cylindrical heating rod and the start temperature of thermal runaway are higher than that of the battery heated by spring heating coil. The energy required to cause thermal runaway of battery decreases with the increase of SOC. The first decrease of battery voltage is the signal of obvious self-generated heat inside the battery. Under the same SOC, the battery heated by cylindrical heating rod needs to absorb more heat to touch the thermal runaway. The battery will produce toxic gas after thermal runaway, and the severity of battery thermal runaway directly affects the proportion of electrolyte. This work can provide some guidance for the domino effect and early warning of thermal runaway of lithium-ion batteries.

Experimental investigation on the characteristics of thermal runaway and its propagation of large-format lithium ion batteries under overcharging and overheating conditions

Overcharge and overheating are two common safety issues for the large-scale application of lithium-ion batteries (LIBs), and in-depth understanding of the thermal runaway (TR) and its propagation of LIBs induced by overcharging and overheating are strongly required to guide the safety design of battery system. In this paper, investigation on characteristics and mechanism of TR and its propagation of LIBs induced by overcharging and overheating are conducted experimentally. Besides, critical thermal energy triggering TR and chemical thermal contribution are identified. The normalized critical energy triggered by overcharging and overheating to TR are also determined. The results show compared with TR induced by overheating, TR induced by overcharging exhibits a more severe and catastrophic result due to their higher heat release, more combustible gases and mass loss. In addition, critical thermal energy triggering TR may be constant for fully charged batteries under the overheating of 300 W and 400 W, which is slightly affected by heating power (Ph). Moreover, Critical chemical heat shows a certain upward trend with increasing Ph. Critical electric energy triggering TR and critical self-generated heat slightly decrease with increasing overcharge rate. In open environment, TR induced by overheating propagates faster than that induced by overcharging.

Strain rate dependent formulation of the latent heat evolution of superelastic shape memory alloy wires incorporated in multistory frame structures

Due to their unique hysteretic energy dissipation capacity, shape memory alloy (SMA) wires are particularly interesting for the development of new-type of intelligent vibration control systems for structures. However, in structural control, most of the vibrations occur in high strain rate regimes, which interfere the release of self-generated heat and thus influence the hysteretic dissipation. This paper proposes a strain rate dependent formulation of the latent heat evolution and aims to improve the accuracy of existing macroscopic modeling approaches developed for SMA wires particularly for the dynamic load cases. The proposed formulation is determined phenomenologically and implemented in a continuum thermomechanical framework based constitutive SMA wire model without impairing the simplicity and robustness of the solution process. The proposed formulation is validated by cyclic tensile tests conducted on SMA wires. Results show that the calculations using the formulation can predict the wire response more accurately than the strain rate independent formulation. For the simulation of multistory frame structures incorporating multiple SMA wires, the governing equations are driven. Shaking table tests are conducted on a 3-story frame structure under harmonic and seismic excitation. The responses of the structure are successfully replicated using the strain rate dependent latent heat formulation.

Charging Of SmartPhone Through Self-Generated Heat

In this age of highly memory intense applications and increasing size of Random Access Memory (RAM), mobile Central Processing Unit (CPU) temperatures are bound to reach high values; the range can even extend up to 48 degree Celsius. In that case, it would only be logical to try and harvest that heat energy, which could help in the phone’s performance by actually cooling the device down and simultaneously it can be charged through converting this heat energy into electrical energy. When mobile phones are being charged by motion as well, heat should not be left behind because it is one of the most thermodynamically underappreciated sources of energy. In this paper, a Peltier Module has been used to capture heat from the CPU or the surroundings to generate a voltage that will supply power to the battery. The advantages of this method includes that a phone can be charged at anyplacewhere no power source is available. The only disadvantage in this method would be a low efficiency, because heat itself is of very low quality energy source.

Application and Mechanisms of Self-Generated Heat Foam for Enhanced Oil Recovery

Foams are widely used in the oil and gas industry due to their unique viscous and elastic properties. However, typical foam injection methods into reservoirs require large equipment with high injection pressure, which might not be suitable for development of offshore oilfields, deep wells, or high condensate petroleum reservoirs. Here, for the first time, we report self-generated heat foams (SGHFs) that are systematically generated and studied by combining self-generated nitrogen gas reactants (sodium nitrite and ammonium chloride) and environmentally friendly surfactants. Sandpack oil recovery flooding experiments at 60 °C and 4 MPa along with two-dimensional (2D) visualization micromodel experiments were carried out to analyze the oil displacement mechanisms. Various oil recovery aspects such as heat production, oil viscosity reduction, foam generation, profile control, and heat-foam synergistic effects were investigated. The results showed that SGHFs can increase oil recovery by 33.9% from homogeneous (permeability of ∼2 Darcy) single layer formation and by 20.4% from heterogeneous (permeability ratio >10) multilayer formation. The incremental oil recovery by SGHFs was much higher than that of conventional foam or self-generated heat (SGH) without foam. The heat produced by the SGHF chemical reaction increased the temperature of the crude oil by 13 °C, reduced the crude oil viscosity by 35%, and helped increase oil recovery by reducing the mobility ratio. Moreover, the foams generated by SGHFs had a remarkable effect on the profile (conformance) control in the presence of crude oil. The synergistic effect between the heat and the foam produced by SGHF chemical reaction can be explained by (1) The chemical reaction can produce small and uniform foam, seen by the 2D micromodel, which can block large pores in porous media and enhance sweep efficiency and (2) The uniform sweep efficiency due to the presence of foam can help distribute the heat and make the temperature rise evenly along the sandpack, which was beneficial to reduce the crude oil viscosity throughout the entire porous media and improve oil recovery.

Passive radiative cooling design with broadband optical thin-film filters

The operation of most electronic semiconductor devices suffers from the self-generated heat. In the case of photovoltaic or thermos-photovoltaic cells, their exposure to sun or high temperature sources make them get warm beyond the desired operating conditions. In both incidences, the solution strategy requires effective radiative cooling process, i.e., by selective absorption and emission in predetermined spectral windows. In this study, we outline two approaches for alternative 2D thin film coatings, which can enhance the passive thermal management for application to electronic equipment. Most traditional techniques use a metallic (silver) layer because of their high reflectivity, although they display strong absorption in the visible and near-infrared spectrums. We show that strong absorption in the visible and near-infrared spectrums due to a metallic layer can be avoided by repetitive high index-low index periodic layers and broadband reflection in visible and near-infrared spectrums can still be achieved. These modifications increase the average reflectance in the visible and near-infrared spectrums by 3–4%, which increases the cooling power by at least 35W/m2. We also show that the performance of radiative cooling can be enhanced by inserting an Al2O3 film (which has strong absorption in the 8–13µm spectrum, and does not absorb in the visible and near-infrared) within conventional coating structures. These two approaches enhance the cooling power of passive radiative cooling systems from the typical reported values of 40W/m2–100W/m2 and 65W/m2 levels respectively.

Comparison of airf low environmental effects on thermal fabrics

Smart thermal textiles are becoming increasingly popular and temperature precision is one of the important targets in their industrialization and commercialization. Some thermal products do not rely on temperature sensors but rather the input electric current pulse to achieve thermal control. In this situation, the surrounding environment, especially ventilation, can greatly affect the thermal control process. Therefore, in this paper, a case study of an apparel system will be provided to study the effect of airflow on the heating process of thermal fabric. The relationship between temperature precision and ventilation is determined when the air flows at any angle to the surface of the thermal fabric. The results show that the thermal conductivity is proportional to the wind speed when the wind speed is high; in contrast, when the wind speed is near to zero, the thermal conductivity of the thermal fabric will not proportionally tend to zero as the result of self-generated heat transfer. This research also shows that the air inflow angle and the wind direction has little effect on the heat dissipation of thermal fabric. This research may generate the data archive and become a valuable reference for future soft thermal studies. It is expected that the developed system will span multidisciplinary gaps and contribute to a new form in a precise and controllable way within the textile industry.

Thermo-structural optimization of the ITER ICRH Four Port Junction and Straps against in-vessel design criteria

Design optimization work has been conducted on the ITER Ion Cyclotron Resonance Heating (ICRH) Four Port Junction (4PJ) and Straps – a sub-assembly of the antenna. The aim of the analysis is to evaluate ways of making the component compliant with SDC-IC rules while balancing the competing demands of different performance requirements. Of particular interest are the bends that connect the 316L(N) strap pipes to its housing, where previous work had shown that primary plus secondary stresses would result in a low predicted fatigue life. The aim of the study was to explore the possibility of reducing stresses in these bends. Coupled ANSYS CFX and structural models are used to calculate coolant and metal temperatures and resulting stresses due to incident and self-generated heat. Although all of the modifications explored resulted in primary plus secondary stresses exceeding the cyclic damage design criteria, some avenues are identified for future studies and a reduction in stress toward the target is obtained.

Simultaneous measurement of self-generated magnetic fields and electron heat transport in dense plasma

AbstractThe role of self generated magnetic fields in the transport of a heat wave following a nanosecond laser irradiation of a solid target is investigated. Magnetic fields are expected to localize the electron carrying the heat flux but at the same time are affected in their evolution by the heat flux itself. We performed simultaneous measurements of heat wave propagation velocity within the target and magnetic fields developing on the target surface. These were compared to results obtained by numerical magneto-hydrodynamic modeling, including self-generated B fields. The comparison shows that longitudinal heat flow is overestimated in the simulations. Similarly, but most notably, the radial expansion of the magnetic fields is underestimated by the modeling. The two are likely linked, the more pronounced radial drift of B-fields induces a rotation of heat flux in the radial direction, and corresponding longitudinal heat flux inhibition. This suggests the need for improving present modeling of self-generated magnetic fields evolution in high power laser-matter interaction.

Probabilistic Risk Assessment Using Dynamic Flowgraph Methodology for Copper Chloride CANDU-SCWR Hydrogen Production

Copper chloride cycle is a proven efficient method to separate hydrogen from water. Super Critical Water Reactor (SCWR) is the focus of generation IV reactor design for optimization of the nuclear energy. This research has modeled an integration of copper chloride cycle hydrogen and oxygen units with the proposed SCWR Primary Heat Transport (PHT) cycle, to accommodate the load variation and to compensate SCWR excessive heat produced during off peak hours. Copper chloride cycle is regenerative and can meet up to fifty percent of its heat requirements; the research investigates the efficiency and safety of a switch over between self-generated and external heat mechanism. The integration is analyzed for its reliability by using the conventional fault tree method and state of the art dynamic flowgraph methodology. Dynamic flowgraph methodology dymonda software analysis produced probable alternates, depicting the probabilistic risk assessment for the integration model.

Procesamiento no térmico de alimentos

Conventional approaches to process foods have proven to offer very safe products but, in some cases, the quality of the final product is significantly lower to the original one. Nonthermal processing of foods has emerged as a viable alternative to those conventional processing by offering safe products of excellent quality and at very reasonable cost. These emerging technologies utilize nonthermal microbial stress factors as the main inactivation mechanism. In some cases, external sources of heat or self-generated heat are utilized to supplement the main inactivation mechanism. This combination becomes very relevant in the case of the sterilization of low-acid foods by pressure assisted thermal processing (PATP). This article presents some of the most relevant nonthermal technologies where some of them are already in use by the food industry and others will be adopted in the very near future. It is the case; these nonthermal technologies could be used in combination among themselves or with other preservation approaches seeking synergistic effects in order to have shorter processes and very good quality food products.

Evidence of thermal effects in a high-power Er^3+–Yb^3+ fiber laser

We analyze the influence of heat generation caused by nonradiative transitions in a high-power 1.55 μm double-clad erbium–ytterbium fiber laser on the Stark level population. At strong pumping rates, 1 μm lasing can start as a result of parasitic reflections. We present a model that allows us to simulate the effect of self-generated heat on the Stark level population by using the MacCumber relation. Heat generation plays a significant role and improves the 1.5 μm laser’s efficiency by increasing the 1 μm lasing threshold.

Impact of the self-generated heat on the scalability of HEMTs

This work is aimed at studying the influence of the self-heating effect on the scalability of HEMTs from an experimental point of view. To accomplish that, we analyze the DC and microwave performance of devices having scaled gate widths. Our experimental results show that the DC transconductance does not scale linearly with the gate periphery under high power dissipation condition. The observed degradation of the transconductance in larger devices can be explained by a reduction of the average carrier velocity due to the occurrence of self-heating. Thermal phenomena even affect the RF small signal performance of the devices under test as they influence the DC operating point. Therefore, the RF transconductance and the forward transmission coefficient are degraded when the dissipated power increases so that all the self-generated heat cannot be completely removed.

Vibration Control of High-Rise Buildings Using High-Damping Rubber Damper. 3rd Report. Temperature Dependency and Durability of Cylinder Type High-Damping Rubber Damper.

A new type of high-damping rubber damper for vibration control of tall buildings has been being developed in this study. This paper describes the temperature dependency of the damper which will be an important problem in vibration control systems using high molecule material. The tests were carried out in two different conditions from the viewpoint of the temperature variation of vibration control material into the dampers. One is the variation of environmental temperature around the damper and the other is the self-generated heat in the damper which will be induced by the cyclic loading such as earthquake or wind. Moreover, the durability of damper was investigated by following tests; breaking test, static tests and cyclic loading tests under excessive shear strain amplitude. As the results, it was confirmed that the temperature dependency of the damper would not much affect to the energy absorbing characteristics even in the case of the practical use and the durability of the damper was highly enough against the large earthquakes by means of its strong adhesive characteristics.

Reaserch and prospects on clean utilization of coal

Due to the fact that lithium ions are subjected to different thermal abuses during services, this paper introduces heating of lithium-ion batteries with different State of Charge (SOC) by means of a spring heating ring and a cylindrical heating rod. The results show that with the increase of SOC, the thermal runaway phenomenon of lithium-ion battery increases dramatically. Under the same SOC, owing to the better heat transfer efficiency of the spring heating coil and the more uniform internal heating of the battery, the temperature of the battery heated by cylindrical heating rod and the start temperature of thermal runaway are higher than that of the battery heated by spring heating coil. The energy required to cause thermal runaway of battery decreases with the increase of SOC. The first decrease of battery voltage is the signal of obvious self-generated heat inside the battery. Under the same SOC, the battery heated by cylindrical heating rod needs to absorb more heat to touch the thermal runaway. The battery will produce toxic gas after thermal runaway, and the severity of battery thermal runaway directly affects the proportion of electrolyte. This work can provide some guidance for the domino effect and early warning of thermal runaway of lithium-ion batteries.