scholarly journals Visualization Study of Startup Modes and Operating States of a Flat Two-Phase Micro Thermosyphon

Energies ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 2291 ◽  
Author(s):  
Liangyu Wu ◽  
Yingying Chen ◽  
Suchen Wu ◽  
Mengchen Zhang ◽  
Weibo Yang ◽  
...  
Keyword(s):  
Wall Temperature ◽  
Large Amplitude ◽  
Small Amplitude ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Interface Evolution ◽  
Visualization Experiment

The flat two-phase thermosyphon has been recognized as a promising technique to realize uniform heat dissipation for high-heat-flux electronic devices. In this paper, a visualization experiment is designed and conducted to study the startup modes and operating states in a flat two-phase thermosyphon. The dynamic wall temperatures and gas–liquid interface evolution are observed and analyzed. From the results, the sudden startup and gradual startup modes and three quasi-steady operating states are identified. As the heat load increases, the continuous large-amplitude pulsation, alternate pulsation, and continuous small-amplitude pulsation states are experienced in sequence for the evaporator wall temperature. The alternate pulsation state can be divided into two types of alternate pulsation: lengthy single-large-amplitude-pulsation alternated with short multiple-small-amplitude-pulsation, and short single-large-amplitude-pulsation alternated with lengthy multiple-small-amplitude alternate pulsation state. During the continuous large-amplitude pulsation state, the bubbles were generated intermittently and the wall temperature fluctuated cyclically with a continuous large amplitude. In the alternate pulsation state, the duration of boiling became longer compared to the continuous large-amplitude pulsation state, and the wall temperature of the evaporator section exhibited small fluctuations. In addition, there was no large-amplitude wall temperature pulsation in the continuous small-amplitude pulsation state, and the boiling occurred continuously. The thermal performance of the alternate pulsation state in a flat two-phase thermosyphon is inferior to the continuous small-amplitude pulsation state but superior to the continuous large-amplitude pulsation state.

scholarly journals Numerical Simulation of a Thermosyphon Radiator Used in Electronic Devices

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Liang Ding ◽  
Wei Wang ◽  
Bingrui Li ◽  
Yong Shuai ◽  
Bingxi Li
Keyword(s):  
Heat Flux ◽  
Numerical Model ◽  
Thermal Resistance ◽  
Wall Temperature ◽  
Thermal Load ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
High Heat ◽  
High Heat Flux ◽  
Load Conditions

The heat dissipation of electronic devices is an important issue. The thermosyphon radiators have high heat dissipation performance, so they are gradually widely used in electronic devices. In this study, a numerical model of the thermosyphon is established. It is observed that simulated temperatures agree well with experimental data in the literature with a relative error no more than 4%. After the numerical model is validated, it is used in the simulation of the thermosyphon radiator. The wall temperature of the condensing section under different thermal load conditions is compared, and the thermal resistance of the condensing section is analyzed. The results show that with the increase of heating and condensing heat flux, the wall temperature fluctuation of the condensing section increases, but very small just about 5K, 6K, 7K, and 9K, respectively. The thermal resistance of the condensing section decreases, indicating that the thermosyphon radiator has a better performance under high heat flux conditions.

Thermoreflectance Wall Temperature Measurement in Annular Two-Phase Flow

2019 ◽  
Author(s):  
Jason Chan ◽  
Brian E. Fehring ◽  
Roman W. Morse ◽  
Kristofer M. Dressler ◽  
Gregory F. Nellis ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Annular Flow ◽  
High Heat ◽  
High Heat Flux ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
Dry Out

Abstract A thermoreflectance method to measure wall temperature in two-phase annular flow is described. In high heat flux conditions, momentary dry-out occurs as the liquid film vaporizes, resulting in dramatic decreases in heat transfer coefficient. Simultaneous liquid and vapor thermoreflectance measurements allow calculations of instantaneous and time-averaged heat transfer coefficients. Validation, calibration and uncertainty of the technique are discussed.

scholarly journals Effect of Surface Microstructure on the Heat Dissipation Performance of Heat Sinks Used in Electronic Devices

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 265
Author(s):  
Yuxin You ◽  
Beibei Zhang ◽  
Sulian Tao ◽  
Zihui Liang ◽  
Biao Tang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Thermal Radiation ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
High Heat ◽  
Heat Sinks ◽  
High Heat Flux ◽  
Thermal Emissivity ◽  
Effect Of Surface

Heat sinks are widely used in electronic devices with high heat flux. The design and build of microstructures on heat sinks has shown effectiveness in improving heat dissipation efficiency. In this paper, four kinds of treatment methods were used to make different microstructures on heat sink surfaces, and thermal radiation coating also applied onto the heat sink surfaces to improve thermal radiation. The surface roughness, thermal emissivity and heat dissipation performance with and without thermal radiation coating of the heat sinks were studied. The result shows that with an increase of surface roughness, the thermal emissivity can increase up to 2.5 times. With thermal radiation coating on a surface with microstructures, the heat dissipation was further improved because the heat conduction at the coating and heat sink interface was enhanced. Therefore, surface treatment can improve the heat dissipation performance of the heat sink significantly by enhancing the thermal convection, radiation and conduction.

Single-Phase and Two-Phase Hybrid Cooling Schemes for High-Heat-Flux Thermal Management of Defense Electronics

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Myung Ki Sung ◽  
Issam Mudawar
Keyword(s):  
Single Phase ◽  
Heat Dissipation ◽  
Jet Impingement ◽  
High Heat ◽  
High Heat Flux ◽  
Microchannel Flow ◽  
Two Phase ◽  
Cooling Performance ◽  
Hybrid Cooling ◽  
Circular Jets

This study examines the cooling performance of two hybrid cooling schemes that capitalize on the merits of both microchannel flow and jet impingement to achieve the high cooling fluxes and uniform temperatures demanded by advanced defense electronics. The jets supply HFE 7100 liquid coolant gradually into each microchannel. The cooling performances of two different jet configurations, a series of circular jets and a single slot jet, are examined both numerically and experimentally. The single-phase performances of both configurations are accurately predicted using 3D numerical simulation. Numerical results point to complex interactions between the jets and the microchannel flow, and superior cooling performance is achieved by optimal selection of microchannel height. The two-phase cooling performance of the circular-jet configuration is found superior to that of the slot jet, especially in terms of high-flux heat dissipation. Unprecedented cooling fluxes, as high as 1127 W/cm2, are achieved with the circular jets without incurring CHF.

Fast Transient and Intensified Heat Dissipation Applicable to High Heat Flux Density

2011 ◽  
Author(s):  
Jing Li ◽  
Shuanshi Fan ◽  
Zemin Yao ◽  
Jing Li ◽  
Xinli Wei
Keyword(s):  
Heat Flux ◽  
Flux Density ◽  
Heat Flux Density ◽  
Heat Dissipation ◽  
Electronic Devices ◽  
Spray Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Power Electronic ◽  
Fast Transient

In this paper, in order to solve the problem of intensified heat dissipation in high power electronic devices, a fast transient and intensified heat dissipation technology was put forward by comparing many heat transfer modes based on the analytical study on the existing technologies about heat dissipation at high heat flux density and about fast heat transport. This technology combined spray cooling technology with fast endothermic chemical reaction processes; we summarized the characteristics of media applicable to an environment with transient high heat flux density by comparing various parameters of many sprayed media in the spray cooling process. According to the energy balance of endothermic chemical reactions of relevant media, we determined the media (mainly carbon dioxide hydrate) applicable to the fast transient and intensified heat dissipation technology and presented the conditions for the chemical reactions. We analyzed the methods controlling the instantaneous chemical reaction rate and proposed the structural characteristics of the chemical reactor so as to ensure that the time for heat removal will be control to around 0.01 second. Thus, the problem of fast transient heat dissipation in high power electronic devices, etc. would be radically solved.

Reliable MOSFET operation using two-phase microfluidics in the presence of high heat flux transients

2011 ◽  
Vol 21 (10) ◽  
pp. 105002 ◽  
Author(s):  
Shiv Govind Singh ◽  
Amit Agrawal ◽  
Siddhartha P Duttagupta
Keyword(s):  
Heat Flux ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase

Model Predictive Control of a Pumped Two-Phase Cooling System With Microchannel Heat Exchangers

2018 ◽  
Author(s):  
Oyuna Angatkina ◽  
Andrew Alleyne
Keyword(s):  
Heat Flux ◽  
Model Predictive Control ◽  
Predictive Control ◽  
Heat Exchangers ◽  
Cooling System ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Cooling Systems ◽  
Two Phase Cooling

Two-phase cooling systems provide a viable technology for high–heat flux rejection in electronic systems. They provide high cooling capacity and uniform surface temperature. However, a major restriction of their application is the critical heat flux condition (CHF). This work presents model predictive control (MPC) design for CHF avoidance in two-phase pump driven cooling systems. The system under study includes multiple microchannel heat exchangers in series. The MPC controller performance is compared to the performance of a baseline PI controller. Simulation results show that while both controllers are able to maintain the two-phase cooling system below CHF, MPC has significant reduction in power consumption compared to the baseline controller.

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