scholarly journals On the Reproducibility of Thermal Measurements and of Related Thermal Metrics in Static and Transient Tests of Power Devices

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 557
Author(s):  
Gabor Farkas ◽  
Dirk Schweitzer ◽  
Zoltan Sarkany ◽  
Marta Rencz
Keyword(s):  
Thermal Resistance ◽  
Systematic Difference ◽  
External Boundary ◽  
Test Scheme ◽  
Structural Elements ◽  
Power Devices ◽  
Thermal Capacitance ◽  
Thermal Measurements ◽  
Single Number ◽  
Dual Interface

Traditionally the thermal behavior of power devices is characterized by temperature measurements at the junction and at accessible external points. In large modules composed of thin chips and materials of high thermal conductivity the shape and distribution of the heat trajectories are influenced by the external boundary represented by the cooling mount. This causes mediocre repeatability of the characteristic RthJC junction to case thermal resistance even in measurements at the same laboratory and causes very poor reproducibility among sites using dissimilar instrumentation. The Transient Dual Interface Methodology (TDIM) is based on the comparison of measured structure functions. With this method high repeatability can be achieved although introducing severe changes into the measurement environment is the essence of this test scheme. There is a systematic difference between thermal data measured with TDIM method and that measured with temperature probes, but we found that this difference was smaller than the scatter of the latter method. For checking production stability, we propose the use of a structure function-based Rth@Cth thermal metric, which is the thermal resistance value reached at the thermal capacitance belonging to the mass of the package base. This metric condenses the consistency of internal structural elements into a single number.

scholarly journals Discrete-Pulsed Current Time Method to Estimate Channel Thermal Resistance of GaN-Based Power Devices

2018 ◽  
Vol 65 (12) ◽  
pp. 5301-5306 ◽  
Author(s):  
Zheng Xu ◽  
Saptarshi Mandal ◽  
Jianyi Gao ◽  
Harshad Surdi ◽  
Wenwen Li ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Pulsed Current ◽  
Power Devices ◽  
Current Time

Modelling of the Internal Cooling of Fish during Ice Storage

2007 ◽  
Vol 3 (4) ◽  
Author(s):  
Dilip Jain ◽  
Pankaj Pathare
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Surface Heat ◽  
Cooling Time ◽  
Internal Cooling ◽  
Average Surface ◽  
Thermal Capacitance ◽  
Fish Weight ◽  
Surface Heat Transfer Coefficient

The internal cooling of fish has been studied on the basis of Newton’s cooling law. Experiments were conducted by cooling of the Indian major carp (Catla catla) of different weights with ice in an insulated box. Exponential model describing cooling of objects having irregular shape has been investigated. The developed model could predict the fish cooling with ice within a percent error of 0.74. The thermal properties of fish cooling with ice have been evaluated. The cooling data such as cooling coefficients, average surface heat transfer coefficient, thermal resistance, thermal capacitance, half cooling time and seven-eighth cooling time were determined for individual fish. The results show that the half cooling time and seven-eighth cooling time increased and the cooling rate decreased with increase in the weight of fish, respectively. Thermal resistance was independent of fish weight and having an average value of 1. 22 °C W-1. Thermal capacitance increased with fish weight and ranged from 665.8 to 4639.3 J °C-1. The average surface heat transfer coefficient of fish cooling with ice ranged from 11.68 to 34.41 W m-2 °C-1.

Non-Intrusive Case Temperature Measurement Method of Direct-Water-Cooled Power Module

2015 ◽  
Author(s):  
Keisuke Horiuchi ◽  
Yuichiro Konishi ◽  
Atsuo Nishihara
Keyword(s):  
Thermal Resistance ◽  
Structure Function ◽  
Temperature Measurement ◽  
Flow Rate ◽  
Measurement Method ◽  
Water Flow Rate ◽  
Power Module ◽  
Thermal Capacitance ◽  
Simulation Results ◽  
Heat Spreading

In this paper, we present a non-intrusive case temperature measurement method of the direct-water-cooled power module. It uses the structure function, which in this case comprises the cumulative thermal capacitance and the cumulative thermal resistance. Since the effective heat transfer rate of the pinfin heatsink varies with the water flow rate, in this study we assumed the inflection point of the structure function corresponding to the change in the flow rate was junction-case thermal resistance. We compared numerical simulation results with experimental results and present our findings. Finally, we show that the design area in which the heat spreading angle of 45 degrees, the well-known rule of thumb, is suitable.

scholarly journals Quick Fabrication VCSELs for Characterisation of Epitaxial Material

2021 ◽  
Vol 11 (20) ◽  
pp. 9369
Author(s):  
Jack Baker ◽  
Craig P. Allford ◽  
Sara-Jayne Gillgrass ◽  
Richard Forrest ◽  
David G. Hayes ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Threshold Current ◽  
Cavity Resonance ◽  
Sufficient Information ◽  
Substrate Thickness ◽  
Structural Elements ◽  
Lasing Wavelength ◽  
Systematic Analysis ◽  
Time Required ◽  
The Impact

A systematic analysis of the performance of VCSELs, fabricated with a decreasing number of structural elements, is used to assess the complexity of fabrication (and therefore time) required to obtain sufficient information on epitaxial wafer suitability. Initially, sub-mA threshold current VCSEL devices are produced on AlGaAs-based material, designed for 940 nm emission, using processing methods widely employed in industry. From there, stripped-back Quick Fabrication (QF) devices, based on a bridge-mesa design, are fabricated and this negates the need for benzocyclcobutane (BCB) planarisation. Devices are produced with three variations on the QF design, to characterise the impact on laser performance from removing time-consuming process steps, including wet thermal oxidation and mechanical lapping used to reduce substrate thickness. An increase in threshold current of 1.5 mA for oxidised QF devices, relative to the standard VCSELs, and a further increase of 1.9 mA for unoxidised QF devices are observed, which is a result of leakage current. The tuning of the emission wavelength with current increases by ~0.1 nm/mA for a VCSEL with a 16 μm diameter mesa when the substrate is unlapped, which is ascribed to the increased thermal resistance. Generally, relative to the standard VCSELs, the QF methods employed do not significantly impact the threshold lasing wavelength and the differences in mean wavelengths of the device types that are observed are attributed to variation in cavity resonance with spatial position across the wafer, as determined by photovoltage spectroscopy measurements.

scholarly journals THE FORMATION OF THE HEAT-INSULATING PROTECTING STRUCTURES OF DOME BUILDINGS TO THE FAR NORTH

2020 ◽  
Vol 2 (4) ◽  
pp. 21-26
Author(s):  
S. Ovsyannikov ◽  
A. Suska ◽  
S. Shevchenko
Keyword(s):  
Thermal Resistance ◽  
Thermal Insulation ◽  
Residential Buildings ◽  
Climatic Conditions ◽  
The Arctic ◽  
Structural Elements ◽  
Minimum Thickness ◽  
Far North ◽  
Inner Surface ◽  
The Russian Federation

the regions of the Far North are of great importance in the economic development of the Russian Federation. The harsh climatic conditions of the Arctic predetermine the requirements for residential buildings, in particular to ensure the thermal insulation properties of the enclosing structures of prefabricated buildings for living workers working in shifts. In this paper the calculation of the normalized values of thermal resistance of the protecting designs is made, the design and structure of walls and overlappings of collapsible structures is developed. To ensure the required thermal resistance at a minimum thickness of structural elements, it is proposed to apply liquid thermal insulation on the inner surface of the walls.

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