scholarly journals Influence of Geometrical Changes in an Adiabatic Portion on the Heat Transfer Performance of a Two-Phase Closed Thermosiphon System

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3070
Author(s):  
Mohanraj Chandran ◽  
Rajvikram Madurai Elavarasan ◽  
Ramesh Babu Neelakandan ◽  
Umashankar Subramaniam ◽  
Rishi Pugazhendhi
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Transfer Performance ◽  
Heat Fluxes ◽  
Heat Transfer Analysis ◽  
Transfer Performance ◽  
Two Phase ◽  
Cross Sectional ◽  
Inclination Angles ◽  
Adiabatic Section

In this study, a modified non-uniform adiabatic section in a Two-Phase Closed Thermosiphon (TPCT) is proposed where the uniform section was replaced by convergent and divergent (C-D) sections. The heat transfer analysis was performed on the modified TPCT and their findings were compared with standard TPCT. The deionized water (DI) in the proportion of 30 vol% is filled in both the TPCTs. Further, the heat transfer performance analysis was carried out for three different orientations, such as 0°, 45° and 90°, and heat input was varied from 50 to 250 W. The effect of these geometrical changes and inclination angles on the heat transfer performance of both the TPCT were evaluated to compare the thermal resistance, wall temperature variation and heat transfer coefficient. The non-dimensional numbers such as Weber (WE), Bond (BO), Condensation (CO) and Kutateladze (KU) were investigated based on heat fluxes for both TPCTs. By introducing the convergent-divergent section nearer to the condenser, the pressure before and after the C-D section was increased and decreased. This enhances the heat transfer in the evaporator slightly up to 2% and 1.4% at horizontal and 45° orientation, respectively, in Non-Uniformed Adiabatic Section (NUAS) TPCT when compared to Uniformed Adiabatic Section (UAS) TPCT. The thermal resistance of NUAS TPCT was reduced by up to 4.5% relative to UAS TPCT in horizontal and 45°. The results of the non-dimensional number also confirmed that NUAS TPCT provided better performance by enhancing 2% more pool boiling characteristics, interaction forces and condensate returns. Several factors such as gravity assistance, fluid accumulation, pressure drop and thermal resistance exert an influence on the heat transfer performance of the proposed NUAS TPCT at various orientation angles. However, different type of cross-sectional variations subjected to orientation changes may also get influenced by several other parameters that in turn affect the heat transfer performance distinctly.

Experimental Investigation on the Effects of Inclination Angle on Heat Transfer Performance of a Liquid Metal High-Temperature Oscillating Heat Pipe

2021 ◽  
Author(s):  
Mengke Wu ◽  
Yulong Ji ◽  
Yanmin Feng ◽  
Xin Yang ◽  
Yadong Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Heat Transfer Performance ◽  
Input Power ◽  
Transfer Performance ◽  
Oscillating Heat Pipe ◽  
Inclination Angles

Abstract The liquid metal high-temperature oscillating heat pipe (LMHOHP) is a kind of high efficiency heat transfer device, which can function in high-temperature environments above 500°C. In this paper, the effects of inclination angle on the startup and heat transfer performance of a LMHOHP were investigated experimentally. The sodium-potassium alloy (potassium 78%) was used as the working fluid of the LMHOHP and the filling ratio was 50%. The start-up characteristics and heat transfer performance of the LMHOHP at four inclination angles of 0°, 30°, 60° and 90° were tested when the operating temperatures were 150°C and 400°C, respectively. Experimental results show that (1) The LMHOHP can start-up and function at all the tested inclination angles, the maximum temperatures of the evaporator and condenser can exceed 1000°C and 700°C, respectively. (2) The thermal resistance of the LMHOHP decreases with inclination angle increases, the thermal resistance at the inclination angle of 90° decreases by up to 32.9%, 41.6% and 55.9% compared with that at the inclination angle of 60°, 30° and 0°, respectively. (3) When the input power exceeds 3000W, the flow patterns of LMHOHP at the inclination angle of 90°, 60° and 30° can be changed from the oscillating motion to the unidirectional circulating flow. (4) Compared with the operating temperature of 150°C, the heat transfer performance of the LMHOHP improves at the operating temperature of 400°C, at the input power of 3457W and the inclination angle of 90°, the minimum thermal resistance of LMHOHP is 0.075°C/W. The results shown that the LMHOHP has a good adaptability to working conditions which further extends the application range of oscillating heat pipe.

scholarly journals Simulation analysis of heat transfer performance of heat sink with reduced material design

2020 ◽  
Vol 12 (5) ◽  
pp. 168781402092130
Author(s):  
Ya-Chu Chang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Thermal Resistance ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Electronic Device ◽  
Local Heating ◽  
Transfer Performance ◽  
Electronic Components ◽  
Thermal Reliability

The field of electronic device applications is becoming more and more extensive. With the development of science and technology and the improvement of the integration of electronic components, local heating is becoming more and more serious. If heat cannot be discharged immediately, it will cause heat to accumulate, causing the temperature of each component to exceed the limit. The reliability of electronic equipment is greatly reduced. Especially in important fields such as military and aerospace, the thermal reliability of electronic components is higher. The research results show that increasing the Reynolds number is helpful to reduce the overall temperature and thermal resistance of the heat sink, but the increase of the Reynolds number and the decrease of the thermal resistance value are gradually flat. The design concept of material reduction has a significant impact on processing and cost. The results of this article show that selecting the appropriate heat sink fins and matching the specific Reynolds number can effectively improve the heat transfer performance of the heat sink.

scholarly journals Entropy Generation and Heat Transfer Performance in Microchannel Cooling

Entropy ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 191 ◽  
Author(s):  
Jundika Kurnia ◽  
Desmond Lim ◽  
Lianjun Chen ◽  
Lishuai Jiang ◽  
Agus Sasmito
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Heat Transfer Performance ◽  
Second Law Of Thermodynamics ◽  
High Heat ◽  
Heat Fluxes ◽  
Transfer Performance ◽  
Cooling Channel ◽  
High Heat Transfer ◽  
Microchannel Cooling

Owing to its relatively high heat transfer performance and simple configurations, liquid cooling remains the preferred choice for electronic cooling and other applications. In this cooling approach, channel design plays an important role in dictating the cooling performance of the heat sink. Most cooling channel studies evaluate the performance in view of the first thermodynamics aspect. This study is conducted to investigate flow behaviour and heat transfer performance of an incompressible fluid in a cooling channel with oblique fins with regards to first law and second law of thermodynamics. The effect of oblique fin angle and inlet Reynolds number are investigated. In addition, the performance of the cooling channels for different heat fluxes is evaluated. The results indicate that the oblique fin channel with 20° angle yields the highest figure of merit, especially at higher Re (250–1000). The entropy generation is found to be lowest for an oblique fin channel with 90° angle, which is about twice than that of a conventional parallel channel. Increasing Re decreases the entropy generation, while increasing heat flux increases the entropy generation.

scholarly journals Effects of inclination angles on heat transfer performance of a loop thermosyphon for CPU cooling

2014 ◽  
Vol 80 (814) ◽  
pp. TEP0154-TEP0154 ◽  
Author(s):  
Hiroyuki TOYODA ◽  
Yoshihiro KONDO ◽  
Shigemasa SATO ◽  
Shigeyasu TSUBAKI
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Inclination Angles

Thermo-Fluid Dynamic Design Exploration of a Double Pipe Heat Exchanger

2019 ◽  
Author(s):  
Tomohiro Hirano ◽  
Mitsuo Yoshimura ◽  
Koji Shimoyama ◽  
Atsuki Komiya
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Nsga Ii ◽  
Cross Sectional ◽  
Average Temperature ◽  
Double Pipe ◽  
Sectional Shape ◽  
Pipe Heat

Abstract Toward a practical application of the additive manufacturing (AM), this study proposes a shape optimization approach for the cross-sectional shape of the inner pipe of a counter-flow double pipe heat exchanger. The cross-sectional shape of the inner pipe is expressed by an algebraic expression with a small number of parameters, and their heat transfer performance is evaluated by a commercial Computational Fluid Dynamics (CFD) solver. The optimization is conducted by the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) assisted by the Kriging surrogate model, and the NSGA-II finds the optimal cross-sectional shape with many protrusions around the perimeter of the inner channel to improve the heat transfer performance. In this study, heat transfer performance is evaluated from the temperature drop at the outlet of the high-temperature fluid. Through the comparison of two cross-sectional shapes with the same heat transfer surface area — average temperature at the outlet of the optimal high-temperature channel is 324.58 K while average temperature at the outlet of a circular high-temperature channel with the same area as the optimal channel is 331.93 K, it is revealed that the number of protrusions plays important roles which contribute not only to increase heat transfer area but also to improve heat transfer performance.

Ultra-Compact Micro-Scale Heat Exchanger for Advanced Thermal Management in Datacenters

2020 ◽  
Author(s):  
Raffaele L. Amalfi ◽  
Todd Salamon ◽  
Filippo Cataldo ◽  
Jackson B. Marcinichen ◽  
John R. Thome
Keyword(s):  
Heat Transfer ◽  
Form Factor ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Two Phase ◽  
Pressure Drops ◽  
Cooling Technology ◽  
Cooling Loop ◽  
Two Phase Cooling

Abstract The present study is focused on the experimental characterization of two-phase heat transfer performance and pressure drops within an ultra-compact heat exchanger (UCHE) suitable for electronics cooling applications. In this specific work, the UCHE prototype is anticipated to be a critical component for realizing a new passive two-phase cooling technology for high-power server racks, as it is more compact and lighter weight than conventional heat exchangers. This technology makes use of a novel combination of thermosyphon loops, at the server-level and rack-level, to passively cool an entire rack. In the proposed two-phase cooling technology, a smaller form factor UCHE is used to transfer heat from the server-level thermosyphon cooling loop to the rack-level thermosyphon cooling loop, while a larger form factor UCHE is used to reject the total heat from the server rack into the facility-level cooling loop. The UCHE is composed of a double-side-copper finned plate enclosed in a stainless steel enclosure. The geometry of the fins and channels on both sides are optimized to enhance the heat transfer performance and flow stability, while minimizing the pressure drops. These features make the UCHE the ideal component for thermosyphon cooling systems, where low pressure drops are required to achieve high passive flow circulation rates and thus achieve high critical heat flux values. The UCHE’s thermal-hydraulic performance is first evaluated in a pump-driven system at the Laboratory of Heat and Mass Transfer (LTCM-EPFL), where experiments include many configurations and operating conditions. Then, the UCHE is installed and tested as the condenser of a thermosyphon loop that rejects heat to a pumped refrigerant system at Nokia Bell Labs, in which both sides operate with refrigerants in phase change (condensation-to-boiling). Experimental results demonstrate high thermal performance with a maximum heat dissipation density of 5455 (kW/m3/K), which is significantly larger than conventional air-cooled heat exchangers and liquid-cooled small pressing depth brazed plate heat exchangers. Finally, a thermal performance analysis is presented that provides guidelines in terms of heat density dissipations at the server- and rack-level when using passive two-phase cooling.

Two-Phase Heat Transfer Performance of Dielectric Fluid HFE-7100 Within Multiport Microchannel

2008 ◽  
Author(s):  
Lung-Yi Lin ◽  
Yeau-Ren Jeng ◽  
Chi-Chuan Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Single Phase ◽  
Heat Transfer Performance ◽  
Convective Heat Transfer Coefficient ◽  
Dielectric Fluid ◽  
Transfer Performance ◽  
Two Phase ◽  
Two Phase Heat Transfer

This study presents convective single-phase and boiling two-phase heat transfer performance of HFE-7100 coolant within multi-port microchannel heat sinks. The corresponding hydraulic diameters are 450 and 237 μm, respectively. For single-phase results, the presence of inlet/outlet locations inevitably gives rise to considerable increase of total pressure drop of a multi-port microchannel heat sink whereas has virtually no detectable influence on overall heat transfer performance provided that the effect of entrance has been accounted for. The convective boiling heat transfer coefficient for the HFE-7100 coolant shows a tremendous drop when vapor quality is above 0.6. For Dh = 450 μm, it is found that the mass flux effect on the convective heat transfer coefficient is rather small.

scholarly journals Numerical Study on Heat Transfer Performance in Packed Bed

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 414 ◽  
Author(s):  
Shicheng Wang ◽  
Chenyi Xu ◽  
Wei Liu ◽  
Zhichun Liu
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Transfer Process ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Continuous Phase ◽  
Heat Transfer Process ◽  
Packed Beds ◽  
Transfer Performance ◽  
Entransy Dissipation

Packed beds are widely used in industries and it is of great significance to enhance the heat transfer between gas and solid states inside the bed. In this paper, numerical simulation method is adopted to investigate the heat transfer principle in the bed at particle scale, and to develop the direct enhanced heat transfer methods in packed beds. The gas is treated as continuous phase and solved by Computational Fluid Dynamics (CFD), while the particles are treated as discrete phase and solved by the Discrete Element Method (DEM); taking entransy dissipation to evaluate the heat transfer process. Considering the overall performance and entransy dissipation, the results show that, compared with the uniform particle size distribution, radial distribution of multiparticle size can effectively improve the heat transfer performance because it optimizes the velocity and temperature field, reduces the equivalent thermal resistance of convection heat transfer process, and the temperature of outlet gas increases significantly, which indicates the heat quality of the gas has been greatly improved. The increase in distribution thickness obviously enhances heat transfer performance without reducing the equivalent thermal resistance in the bed. The result is of great importance for guiding practical engineering applications.

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