scholarly journals Effect of Channel Diameter on the Combustion and Thermal Behavior of a Hydrogen/Air Premixed Flame in a Swirl Micro-Combustor

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3821 ◽  
Author(s):  
Xiao Yang ◽  
Zhihong He ◽  
Lei Zhao ◽  
Shikui Dong ◽  
Heping Tan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Thermal Performance ◽  
Wall Temperature ◽  
Outer Wall ◽  
Combustion Efficiency ◽  
Premixed Flame ◽  
Channel Diameter ◽  
Recirculation Zones ◽  
Micro Combustor

Improving the flame stability and thermal behavior of the micro-combustor (MC) are major challenges in microscale combustion. In this paper, the micro combustions of an H2/air premixed flame in a swirl MC with various channel diameters (Din = 2, 3, 4 mm) were analyzed based on an established three-dimensional numerical model. The effects of hydrogen mass flow rate, thermal conductivity of walls, and the preferential transport of species were investigated. The results indicated that the flame type was characterized by the presence of two recirculation zones. The flame was anchored by the recirculation zones, and the anchoring location of the flame root was the starting position of the recirculation zones. The recirculation zones had a larger distribution of local equivalence ratio, especially in the proximity of the flame root, indicating the formation of a radical pool. The combustion efficiency increased with an increasing Din due to the longer residence time of the reactants. Furthermore, the MC with Din = 2 mm obtained the highest outer wall temperature distribution. However, the MC with Din = 4 mm had a better uniformity of outer wall temperature and large emitter efficiency due to the larger radiation surface. An increase in thermal conductivity boosts the thermal performance of combustion efficiency, emitter efficiency, and wall temperature uniformity. But there is a critical point of thermal conductivity that can increase the thermal performance. The above results can offer us significant guidance for designing MC with high thermal performance.

Thermal Performance of 3D IC Integration with Through-Silicon Via (TSV)

2011 ◽  
Vol 2011 (1) ◽  
pp. 000025-000032 ◽  
Author(s):  
Heng-Chieh Chien ◽  
John H. Lau ◽  
Yu-Lin Chao ◽  
Ra-Min Tain ◽  
Ming-Ji Dai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Thermal Performance ◽  
Equivalent Thermal Conductivity ◽  
3D Ic ◽  
Through Silicon Via

Thermal performance of 3D IC integration is investigated in this study. Emphasis is placed on the determination of a set of equivalent thermal conductivity equations for Cu-filled TSVs with various TSV diameters, TSV pitches, TSV thicknesses, passivation thicknesses, and microbump pads. Also, the thermal behavior of a TSV cell is examined. Furthermore, 3D heat transfer simulations are adopted to verify the accuracy of the equivalent equations. Finally, the feasibility of these equivalent equations is demonstrated through a simple 3D IC integration structure.

Thermal Performance of 3D IC Integration with Through-Silicon Via (TSV)

2012 ◽  
Vol 9 (2) ◽  
pp. 97-103 ◽  
Author(s):  
Heng-Chieh Chien ◽  
John H. Lau ◽  
Yu-Lin Chao ◽  
Ra-Min Tain ◽  
Ming-Ji Dai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Thermal Performance ◽  
Equivalent Thermal Conductivity ◽  
3D Ic ◽  
Through Silicon Via

Thermal performance of 3D IC integration is investigated in this study. Emphasis is placed on the determination of a set of equivalent thermal conductivity equations for Cu-filled TSVs with various TSV diameters, TSV pitches, TSV thicknesses, passivation thicknesses, and microbump pads. Also, the thermal behavior of a TSV cell is examined. Furthermore, 3D heat transfer simulations are adopted to verify the accuracy of the equivalent equations. Finally, the feasibility of these equivalent equations is demonstrated through a simple 3D IC integration structure.

Experimental Research on Combustion and Emission Performance for Micro Combustor of MTPV System with Stratified Porous Media

2012 ◽  
Vol 608-609 ◽  
pp. 934-940
Author(s):  
Jian Wu ◽  
Bo Li ◽  
Bin Xu ◽  
Jia Xuan Miao
Keyword(s):  
Porous Media ◽  
Temperature Distribution ◽  
Band Gap ◽  
Experimental Research ◽  
Wall Temperature ◽  
Combustion Efficiency ◽  
Critical Component ◽  
Uniform Temperature ◽  
The Past ◽  
Micro Combustor

As the critical component of the system, micro-combustor requires a high and uniform temperature distribution along the wall to meet demands for the band gap of the PV cells. The past experiments have proved that the peak wall temperature of the combustor with porous media increases obviously. This paper will have a research on stratified porous media to enhance the combustion efficiency of the combustor and reduce the emissions.

scholarly journals The Effect of Differentiating the Thermal Conductivity between Inner and Outer Walls on the Stability of a U-Bend Catalytic Heat-Recirculating Micro-Combustor: A CFD Study

2021 ◽  
Vol 11 (12) ◽  
pp. 5418
Author(s):  
Valeria Di Sarli
Keyword(s):  
Thermal Conductivity ◽  
Outer Wall ◽  
Ansys Fluent ◽  
Conductive Materials ◽  
Commercial Code ◽  
Stable Operating ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability ◽  
Micro Combustor ◽  
Operating Window

The effect of differentiating the thermal conductivity between inner and outer walls on the stability of a U-bend catalytic heat-recirculating micro-combustor was investigated. To this end, a two-dimensional computational fluid dynamics (CFD) model was developed using the commercial code ANSYS Fluent (release 2020 R1) and, for different combinations of values for the inner and outer thermal conductivities, simulations of lean pre-mixed propane/air combustion were performed by varying the inlet gas velocity. Numerical results have shown that extinction is mainly ruled by the inner wall, whereas the outer wall controls blowout. Differentiating the thermal conductivity has been found to be an effective strategy to jointly exploit the better extinction resistance of low-conductive (i.e., insulating) materials, required by the inner wall, and better blowout resistance of highly conductive materials, required by the outer wall, thus enlarging the stable operating window of the catalytic micro-combustor compared to the use of the same material for both walls.

scholarly journals The Effect of Catalyst Placement on the Stability of a U-Bend Catalytic Heat-Recirculating Micro-Combustor: A Numerical Investigation

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1560
Author(s):  
Niket S. Kaisare ◽  
Valeria Di Sarli
Keyword(s):  
Thermal Conductivity ◽  
Power Systems ◽  
Outer Wall ◽  
Input Power ◽  
Two Dimensional ◽  
Gas Velocity ◽  
Ansys Fluent ◽  
Conductive Materials ◽  
The Stability ◽  
Micro Combustor

This study investigates the combined effect of catalyst placement and solid thermal conductivity on the stability of a U-bend catalytic heat-recirculating micro-combustor. The CFD code ANSYS Fluent 2020 R1 was used for two-dimensional simulations of lean premixed propane/air combustion by varying the inlet gas velocity, i.e., the input power. Three configurations were compared at low (3 W/(m K)) and high (30 W/(m K)) wall thermal conductivity: (A) the configuration in which both inner and outer walls are catalyst coated; (B) only the inner wall is catalyst coated; and (C) only the outer wall is catalyst coated. Numerical results show that, at low thermal conductivity, configuration (B) exhibits the same resistance to extinction as configuration (A), whereas at high thermal conductivity, configurations (B) and (C) exhibit much lower resistance to blowout than configuration (A). Accordingly, for low-power systems, which typically lose stability via extinction and thus require low-conductive materials, an optimal catalyst placement can be the partial coating of configuration (B). Conversely, for high-power systems, which are prone to blowout and thus require high-conductivity materials, a full coating of both the inner and outer walls is needed to guarantee higher stability. To elucidate these findings, a detailed analysis of the combustion behavior of the three configurations is presented.

Maximizing Heat Transfer Through Joint Fin Systems

2005 ◽  
Vol 128 (2) ◽  
pp. 203-206 ◽  
Author(s):  
A.-R. A. Khaled
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Performance ◽  
Critical Length ◽  
The Other ◽  
Rigid Fixation ◽  
Convection Coefficient ◽  
Heat Transfer Characteristics ◽  
Cold Side ◽  
Transfer Characteristics

Heat transfer through joint fins is modeled and analyzed analytically in this work. The terminology “joint fin systems” is used to refer to extending surfaces that are exposed to two different convective media from its both ends. It is found that heat transfer through joint fins is maximized at certain critical lengths of each portion (the receiver fin portion which faces the hot side and the sender fin portion that faces the cold side of the convective media). The critical length of each portion of joint fins is increased as the convection coefficient of the other fin portion increases. At a certain value of the thermal conductivity of the sender fin portion, the critical length for the receiver fin portion may be reduced while heat transfer is maximized. This value depends on the convection coefficient for both fin portions. Thermal performance of joint fins is increased as both thermal conductivity of the sender fin portion or its convection coefficient increases. This work shows that the design of machine components such as bolts, screws, and others can be improved to achieve favorable heat transfer characteristics in addition to its main functions such as rigid fixation properties.

scholarly journals Enhancement of the Thermal Performance of the Paraffin-Based Microcapsules Intended for Textile Applications

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1120
Author(s):  
Virginija Skurkyte-Papieviene ◽  
Ausra Abraitiene ◽  
Audrone Sankauskaite ◽  
Vitalija Rubeziene ◽  
Julija Baltusnikaite-Guzaitiene
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Comparative Method ◽  
Multiwall Carbon Nanotubes ◽  
Acrylic Resin ◽  
Positive Influence ◽  
Outer Shell ◽  
Ir Camera ◽  
Spacer Fabric ◽  
Thermally Conductive

Phase changing materials (PCMs) microcapsules MPCM32D, consisting of a polymeric melamine-formaldehyde (MF) resin shell surrounding a paraffin core (melting point: 30–32 °C), have been modified by introducing thermally conductive additives on their outer shell surface. As additives, multiwall carbon nanotubes (MWCNTs) and poly (3,4-ethylenedioxyoxythiophene) poly (styrene sulphonate) (PEDOT: PSS) were used in different parts by weight (1 wt.%, 5 wt.%, and 10 wt.%). The main aim of this modification—to enhance the thermal performance of the microencapsulated PCMs intended for textile applications. The morphologic analysis of the newly formed coating of MWCNTs or PEDOT: PSS microcapsules shell was observed by SEM. The heat storage and release capacity were evaluated by changing microcapsules MPCM32D shell modification. In order to evaluate the influence of the modified MF outer shell on the thermal properties of paraffin PCM, a thermal conductivity coefficient (λ) of these unmodified and shell-modified microcapsules was also measured by the comparative method. Based on the identified optimal parameters of the thermal performance of the tested PCM microcapsules, a 3D warp-knitted spacer fabric from PET was treated with a composition containing 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS shell-modified microcapsules MPCM32D and acrylic resin binder. To assess the dynamic thermal behaviour of the treated fabric samples, an IR heating source and IR camera were used. The fabric with 5 wt.% MWCNTs or 5 wt.% PEDOT: PSS in shell-modified paraffin microcapsules MPCM32D revealed much faster heating and significantly slower cooling compared to the fabric treated with the unmodified ones. The thermal conductivity of the investigated fabric samples with modified microcapsules MPCM32D has been improved in comparison to the fabric samples with unmodified ones. That confirms the positive influence of using thermally conductive enhancing additives for the heat transfer rate within the textile sample containing these modified paraffin PCM microcapsules.

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