Duration Of Thermal Cycle Research Articles

Short-cycle borehole thermal energy storage: Impact of thermal cycle duration on overall performance

Borehole thermal energy storage arrays are a common form of seasonal underground energy storage which relies on the thermal mass of subsurface rock or sediment to store hot or cold thermal energy. However in practice, typical seasonal operation seldom leads to cyclic energy recovery factors greater than 50%–60% due to significant thermal losses during prolonged periods between consecutive charges. In this paper, the impact of short cycle operation (down to a few days) on energy recovery and overall performance is investigated. Analytical and numerical models are used to estimate energy recovery as a function of cycle length for a typical array and for two distinct charging and discharging scenarios (constant temperature or thermal charge load), which is novel and has not been done before. The results show that shorter cycle duration yields increased recovery factors and storage capacity, which is ascribed to a greater rate of charge to rate of thermal loss ratio. In particular, short-cycle operation at the scale of days unlocks recovery factors in excess of 85 %. The results, supported by a numerical subsurface analysis of the temperature distribution, also show that the recovery efficiency increases with time as losses approach, but never fully reach, a steady-state.

Short-cycle Borehole Thermal Energy Storage: Impact of Thermal Cycle Duration on Overall Performance

Short-cycle Borehole Thermal Energy Storage: Impact of Thermal Cycle Duration on Overall Performance

Analysis of impacts of thermal shocks on mechanical properties of E-glass fiber reinforced polyester composites

Glass fiber reinforced polyester composites are economic and high-performance composite materialsthat has gained a wide range of applications. Besides the developments in composites design, scientific studies addressing the consequences of thermal changes on the mechanical properties of fiber reinforced polymer composites(FRPCs) are scarce. Therefore, the main aim of the present work is to investigate the physical/mechanical properties of glass fiber reinforced polyester composites under thermal shocks. The effects of thermal cycle duration (2, 5 and 20 hours) on the porosity and mechanical properties (maximum stress, strain, elastic modulus and impact resistance) of polymeric composites reinforced by glass fiber, woven fabric and copper/silica nanoparticles (NPs) were investigated. The results exhibited that the porosity and mechanical properties changed obviously in long duration cycles, i.e., 20 hours. Major reduction trends were observed when the fabric reinforced samples were further reinforced by NPs. It was concluded that although NPs reduce porosity and pose filling effect in composite matrix, can also provide stress concentration locations. The composites reinforced by woven fabric and prepared by RTM method provide better mechanical properties. Moreover, after thermal shocks, the fibers within the composite structure formed curved shapes. Consequently, a reduction occurred at the elastic modulus of fibrous reinforced composites (fiber or fabric) after thermal cycles. Besides theelevated porositywas the predominant factor reducing elastic modulus, fiber deformation was also considered as a hidden factor which has never been discussed in previous research studies. A model of bicomponent structure was used to explain the effects of fiber deformation on elastic modulus of the FRPCs.

Rapid adaptation and continuous performance evaluation of SARS-CoV-2 envelope gene (E-gene) real-time RT-PCR assays to support the hospital surge in test demand.

We describe the timely adaption of both published WHO E-gene protocol and commercially available LightMix Modular E-gene assay to the test platform (ABI 7900 Fast real-time analyzer and TaqMan Fast One-step Virus Master Mix) available in an accredited tertiary hospital laboratory with an on-going evaluation to ensure the provision of quality service within the time constraint. The LightMix Modular E-gene was slightly more sensitive when compared to the WHO E-gene, both analytically and diagnostically. The assay was recommended for screening of SARS-CoV-2 infection. With the availability of technically competent staff through continuous training, the provision of round-the-clock service is feasible despite the test is of high complexity. The thermal cycling duration of the adapted LightMix E-gene and WHO E-gene is shortened by half and one hour respectively and allows the number of runs to double when 24-hround-the-clock service is provided. An increase in testing capacity could support surges in testing demand, which is essential to control the current SARS-CoV-2 pandemic, to prevent potential overwhelming of the healthcare system, and to optimize utilization of the isolation beds.

Fabrication of chromium carbide cermets by electric resistance sintering process: Processing, microstructure and mechanical properties

Chromium carbide-based cermets are suitable for use in abrasive and corrosive environments. This work presents the fabrication of chromium carbide-based cermets by a very fast sintering process: Electric Resistance Sintering. The thermal cycle duration was less than 1 s and without protective atmosphere.Two different compositions were studied: Cr3C2-25NiCr (wt%) and WC-20Cr3C2-7Ni (wt%). Microstructure and crystallographic phases of the initial powders and sintered materials are presented. In addition, hardness and toughness were characterized and compared to conventional materials.One important issue of ERS is the size and homogeneity of the pieces. This work presents the also the fabrication of a mining wear piece and some aspects about scaling up.

Transient cooling of electronic components by flat heat pipes

Abstract This paper presents a theoretical investigation of a Flat Heat Pipe (spreader) designed for the cooling of multiple electronic components in transient state. This model is a transient model, coupling 3D thermal model with a 2D hydrodynamic one through the mass flux of evaporation–condensation, which occurs in a mass conservation equation. The model makes it possible to obtain the FHP wall transient temperatures, the transient pressures, velocities and temperatures in both liquid and vapor phases. A comparison of the behaviour of the FHP and an equivalent solid plate submitted to a transient thermal cycle shows that the FHP enhanced the electronic components cooling for the long thermal cycle duration when the solid plate is more efficient for the very short transient thermal cycles. The FHP provides also a very low thermal resistance, which helps to minimise the temperature gradient and then the hot spots and overheating.

A simple smart wing actuator using Ni-Ti SMA

One way shape memory effect (SME) is not sufficient in the application of the automatic repeated actuation of the SMA wire because the actuator using SME cannot return to its initial shape after it cools down. In the present study, the two-way SME under residual stress is considered. An actuator using the two-way effect of SMA returns to its initial shape by increasing or decreasing the temperature of SMA under initial residual stress. Using the two-way effect, we manufactured a simple smart wing actuator which consists of the SMA wire and a torsional spring to induce variable residual stresses. The SMA wire after the specific training procedure in order for the actuator to be used for the repeated actuations without performance deteriorations in the specified actuation requirements was used. The simple smart wing actuator has been tested for repeated actuations in still-air as an environmental thermal condition for the practical aspect of its usage. The characteristics of actuator behavior according to operation thermal cycle duration time, i.e., the response characteristics for rapid actuation were investigated. By the application of the simple smart wing actuator using the SMA wire, SMA shows novel performance in repeated actuations.

Effect of thermal cycling processes on the structure and properties of heat resistant ceramics

This paper deals with a study of the thermal aging process of a low-porosity refractory material based on the aluminum-titanium silicate system that exhibits high levels of thermomechanical properties. Aluminum titanate, mullite, and rutile form the main crystalline phases of the material. The experimental specimens were subjected to moderate thermal cycling in an automatic fast-heating PAS furnace available at the Minsk Porcelain Factory (temperature 1360~ duration of a cycle 6 h) and to abrupt thermal shocks (heating up to 1300~ and water quenching). In order to study the structure and properties, specimens were drawn at intervals of I0 cycles. It was established that after the first 30 cycles during the course of moderate thermal cycling (after a 180-h operation), no deterioration of the properties of the specimens occurred (in fact, some improvement was observed). This owes to the continuation of the sintering processes that could not proceed to completion during the firing operation. During the process of additional crystallization of the material, the defects developed due to thermal cycling can be 'healed' Subsequent increase of the duration of thermal cycling leads to rapid occurrence of the process of preferential recrystallizatio

オーステナイト系ステンレス鋼溶接継手部におけるＬＴＳ現象に関する解析的評価法 第一報 各種溶接継手部におけるＬＴＳ感受性とその評価

Recently, it has been reported that sensitization in welded joints could be promoted remarkably in the range of lower temperature, in which region, sentization would be hardly indcued for solution heat treated materials. This phenomenon, known as LTS (Low Temperature Sensitization), is becoming a serious problem for operating all sort of reactors and pressure vessels in the high temperature condition. This would be caused by fine carbide nucleation which was induced in weld thermal cycle duration.In this paper, effects of weld thermal cycle on the susceptibility to LTS were discussed by unstable heat conduction analysis. The following properties became evident after examining the experimental results. The peak temperature in weld thermal cycles which could cause LTS in the post weld heat duration, was decreased gradually and LTS region was extended with the increase of weld heat input. And it was also recognized that the susceptibility to LTS in Type 304L was much lower than that in Type 304. According to welding method to imporve the resistance to LTS, application of water quenching welding method was very effective, because of preventing of the carbide nucleation by rapid cooling in weld thermal cycle duration.

Gravitational Effects on Process-Induced Defects in Single Crystal Silicon

Description and discussion of a series of experiments which vary each of several important processing parameters including wafer orientation, temperature, gravity greater than 1 g, and ultimately zero gravity. These experiments are in progress and results to date are included from experiments which control temperature, duration of thermal cycle, and wafer orientation during 1 g processing. Preliminary evidence is presented which indicates that gravitational stresses play a role in defect generation during processing at 1 g.