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An adaptive mesh refinement procedure that uses nodeless variables and quadratic interpolation functions is presented for analysing transient thermal problems. A temperature based finite element scheme with Crank‐Nicolson time marching is used to obtain the thermal solution. The strategies used for mesh adaptation, computing refinement indicators, and time marching are described. Examples in one and two dimensions are presented and comparisons are made with exact solutions. The effectiveness of this procedure for transient thermal analysis is reflected in good solution accuracy, reduction in number of elements used, and computational efficiency.

Recent studies have found that the high demand for air-conditioning usage in tropical countries has affected the thermal adaptability of building occupants to hot weather, and increased building energy consumption. This pilot study aims to investigate the effects of transient thermal environment changes on participants' sensory and physiological responses.

The change of thermal perceptions, skin temperatures and core temperatures when exposed to transient thermal environments (cool-warm-cool) from 10 college-aged female participants during a simulated daily commute by foot to class in a tropical university campus were investigated. Subjective measurements were collected in real-time every 5 min.

The main finding suggests that participants were acclimatised to cool air-conditioned indoor environments, despite exhibiting significant mean skin temperature differences (p < 0.05). In addition, exposure to uniform air conditioning from 17 to 18°C for 20 min was thermally unacceptable and reduced concentration during given tasks.

The study focused on thermal comfort conditions in a uniform air-conditioned lecture hall, and the findings may not be applicable for residential and other private building spaces. The distinct temperature difference between indoor and outdoor in the tropical built environment resulted in high dependence on air-conditioning usage. The building occupants' well-being and energy conservation implications of the findings are discussed.

This study provides the platform for discussion on the dynamics of occupants' comfort level and adopting a more variable thermal environment in tropical spatial transient thermal environments among architects and building management system managers. The findings from this study may contribute to the Malaysian Standards for Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings (MS1525).

A knowledge gap in adaptive thermal comfort due to exposure from transient conditions in tropical university campus for energy efficiency revision has been investigated.

The purpose of this study is to clarify the mechanism of ambient and transient temperature effects on piezoelectric pressure sensors, and to propose corresponding compensation measures. The temperature of the explosion field has a significant influence on the piezoelectric sensor used to measure the shock wave pressure. For accurate shock wave pressure measurement, based on the actual piezoelectric pressure sensors used in the explosion field, the effects of ambient and transient temperatures on the sensor should be studied.

The compensation method of the ambient temperature is discussed according to the sensor size and material. The theoretical analysis method of the transient temperature is proposed. For the transient temperature conduction problem of the sensor, the finite element simulation method of structure-temperature coupling is used to solve the temperature distribution of the sensor and the change in the contact force on the quartz crystal surface under the step and triangle temperatures. The simulation results are highly consistent with the theory.

Based on the analysis results, a transient temperature control method is proposed, in which 0.5 mm thick lubricating silicone grease is applied to the sensor diaphragm, and 0.2 mm thick fiberglass cloth is wrapped around the sensor side. Simulation experiments are carried out to verify the feasibility of the control method, and the results show that the control method effectively suppresses the output of the thermal parasitic.

The above thermal protection methods can effectively improve the measurement accuracy of shock wave pressure and provide technical support for the evaluation of the power of explosion damage.

The paper aims to focus on the semiconductor temperature prediction in the multichip modules by using a simplified 1D model, easy to implement in the electronic simulation tools.

Accurate prediction of temperature variation of power semiconductor devices in power electronic circuits is important for obtaining optimum designs and estimating reliability levels. Temperature estimation of power electronic devices has generally been performed using transient thermal equivalent circuits. This paper has studied the thermal behaviour of the power modules. The study leads to correcting the junction temperature values estimated from the transient thermal impedance of each component operating alone. The corrections depend on multidimensional thermal phenomena in the structure.

The classic analysis of thermal phenomena in the multichip structures, independently of powers’ dissipated magnitude and boundary conditions, is not correct. An advanced 1D thermal model based on the finite element method is proposed. It takes into account the effect of the heat‐spreading angle of the different devices in the module.

The paper focuses on mathematical model of the thermal behaviour in the power module. The study leads to a correction of the junction temperature values estimated from the transient thermal impedance of each component given by manufacturers. The proposed model gives a good trade‐off between accuracy, efficiency and simulation cost.

Transient conjugated forced convection in the thermal entry region of a thick‐walled annulus, filled with a homogeneous and isotropic porous medium, has been numerically investigated using finite‐difference techniques. Non‐Darcian effects as well as axial conduction of heat have been considered. The flow is assumed to be hydrodynamically fully developed and steady but thermally developing and transient. The thermal transient is initiated by a step change in the prescribed isothermal temperature on the outer surface of the external tube of the annulus while the inner surface of the internal tube is kept adiabatic. A parametric study is carried out to explore the effects of the Darcy number, the inertia term, the Peclet number and the porous medium heat capacity ratio on the transient thermal behavior in a given annulus.

This paper aims to present the results of measurements and calculations illustrating mutual thermal coupling between power Schottky diodes made of silicon carbide situated in the common case.

The idea of measurements of mutual transient thermal impedances of the investigated device is described.

The results of measurements of mutual transient thermal impedances between the considered diodes are shown. The experimentally verified results of calculations of the internal temperature waveforms of the considered diodes obtained with mutual thermal coupling taken into account are presented and discussed. The influence of mutual thermal coupling and a self-heating phenomenon on the internal temperature of the considered diodes is pointed out.

The presented methods of measurements and calculations can be used for constructing the investigated diodes made of other semiconductor materials.

The presented results prove that mutual thermal coupling between diodes mounted in the common case must be taken into account to calculate correctly the waveforms of the device internal temperature.

Proper thermal management is a key to improve the efficiency and reliability of light-emitting diodes (LEDs). This paper aims to report the influence of applying thermally conductive materials on thermal performance of indium gallium aluminum phosphide (InGaAlP)-based thin-film surface-mounted device (SMD) LED.

The LED thermal and optical parameters were determined using the combination of thermal transient tester (T3Ster) and thermal and radiometric characterization of power LEDs (TeraLED) instruments. The LED was mounted on FR4, 2W and 5W aluminum (Al) package substrates. Measurements were carried out by setting different boundary conditions: air between LED package and substrate and using thermally conductive epoxy (TIM A) and adhesive (TIM B) of thermal conductivity 1.67 and 1.78 W/mK, respectively.

For LED mounted on FR4 package, the total real thermal resistance is improved because of TIM B by 6 and 9 per cent at 50 and 100 mA, respectively. Likewise, the relative decrease in total thermal resistance of LED on 2W Al package is about 9 and 11 per cent. As well, for LED mounted on 5W Al package, the total real thermal resistance is reduced by 2 and 4 per cent.

No much work can be found in the literature on thermal interface material effects on thermal performance of low-power SMD LED. This work can assist in thermal management of low-power LEDs.

Surface configuration at the interface between two materials makes a huge difference on thermal resistance. Thermal transient analysis is a powerful tool for thermal characterization of complex structures like LEDs. The purpose of this paper is to report the influence of surface finish on thermal resistance.

Surface of heat sink was modified into two categories: machined as channel like structure; and polished using mechanical polisher and tested with 3W green LED for thermal resistance analysis.

The observed surface roughness of rough and polished surface was 44 nm and 4 nm, respectively. Structure function analysis was used to determine the thermal resistance between heat sink and MCPCB board. The observed thermal resistance from junction to ambient (R_thJA) value measured with thermal paste at 700 mA was lower (34.85 K/W) for channel like surface than rough surface (36.5 K/W). The calculated junction temperature (T_J) for channel like surface and polished surface was 81.29°C and 85.24°C, respectively.

Channelled surface aids in increasing bond line thickness. Surface polishing helps to reduce the air gaps between MCPCB and heat sink and also to increase the surface contact conductance.

The proposed method of surface modification can be easily done at laboratory level with locally available techniques.

Much of the available literature is only concentrating on the design modification and heat transfer from fins to ambient. There was little research on modification of top surface of the heat sink and the proposed concept would give good results and also it will make the material cost reduction as well as material too.

The transient thermal behaviour, based on a rigorous transient thermodynamic treatment, of a power VDMOS transistor during turn‐off is presented. The time variation of the interior lattice temperature within the device is calculated by self‐consistently solving the fully coupled Poisson's equation and transient electron continuity equation together with the transient heat flow equation. The simulation takes account of temperature dependent heat conduction and capacity and includes thermoelectric currents due to temperature gradient. To make the transient thermal simulation more robust, a new analytical expression for heat capacity is used.

The thermal behavior at the interfaces (of the deposited strands) during fused filament fabrication (FFF) technique strongly influences bond formation and it is a time- and temperature-dependent process. The processing parameters affect the thermal behavior at the interfaces and the purpose of the paper is to simulate using temperature-dependent (nonlinear) thermal properties rather than constant properties.

Nonlinear temperature-dependent thermal properties are used to simulate the FFF process in a simulation software. The finite-element model is first established by comparing the simulation results with that of analytical and experimental results of acrylonitrile butadiene styrene and polylactic acid. Strand temperature and time duration to reach critical sintering temperature for the bond formation are estimated for one of the deposition sequences.

Temperatures are estimated at an interface and are then compared with the experimental results, which shows a close match. The results of the average time duration (time to reach the critical sintering temperature) of strands with the defined deposition sequences show that the first interface has the highest average time duration. Varying processing parameters show that higher temperatures of the extruder and envelope along with higher extruder diameter and lower convective heat transfer coefficient will have more time available for bonding between the strands.

A novel numerical model is developed using temperature-dependent (nonlinear) thermal properties to simulate FFF processes. The model estimates the temperature evolution at the strand interfaces. It helps to evaluate the time duration to reach critical sintering temperature (temperature above which the bond formation occurs) as it cools from extrusion temperature.