An Assessment of Effects of Nanofluids on Heat Transfer Performance of Two-Phase Cooling Systems

2021 ◽  
Author(s):  
Alexander V. Korobko ◽  
Sana Fateh
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Data Centers ◽  
Heat Transfer Performance ◽  
Future Research ◽  
Transfer Performance ◽  
Two Phase ◽  
Cooling Systems ◽  
The Impact ◽  
Two Phase Cooling

Abstract The recent increase in complexity of computations and the expansion of edge computing have led to the emergence of high power density data centers with an urgent demand for more advanced thermal management systems. Two-phase passive cooling systems such as thermosyphons and heat pipes have been widely used in industry to maintain the temperature of the servers below the threshold of failure and carry away a large quantity of heat from a small area. Such systems are economically viable and sustainable since they have no moving parts and consume lower power. However, an upgrade to these cooling systems is imminent due to the ever-increasing power densities of the data centers and more challenging thermal management issues faced by the industry. Nanofluids have emerged recently as a new class of cooling liquids claiming to enhance the heat transfer performance in single and two-phase cooling systems. As per several studies presented in this paper, the thermal performance of thermosyphons is shown to be enhanced by employing nanofluids. In this paper, a comprehensive review is presented on the effect of nanofluids in improving the Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) in two-phase cooling systems. The boiling phenomenon and working principles of thermosyphons will be discussed to understand the underlying mechanisms affecting heat transfer in the evaporator region, where the heat is absorbed from the source. The impact of nanoparticle features, concentration, and deposition pattern on HTC enhancement will also be studied. Additionally, estimates of the heat dissipation improvement by using nanofluids along with the bottlenecks and challenges faced in applying such fluids practically are reviewed as well. In conclusion, recommendations are made for future research needed to overcome the risks and commercialize the nanofluids in two-phase cooling systems for providing significant improvement in heat transfer performance as compared to conventional working fluids.

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.

Optimization of a U-Bend for Minimal Pressure Loss in Internal Cooling Channels—Part II: Experimental Validation

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Filippo Coletti ◽  
Tom Verstraete ◽  
Jérémy Bulle ◽  
Timothée Van der Wielen ◽  
Nicolas Van den Berge ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Heat Transfer Performance ◽  
Internal Cooling ◽  
Transfer Performance ◽  
Cooling Channel ◽  
Piv Measurements ◽  
Cooling Channels ◽  
Numerical Predictions ◽  
The Impact

This two-part paper addresses the design of a U-bend for serpentine internal cooling channels optimized for minimal pressure loss. The total pressure loss for the flow in a U-bend is a critical design parameter, as it augments the pressure required at the inlet of the cooling system, resulting in a lower global efficiency. In the first part of the paper, the design methodology of the cooling channel was presented. In this second part, the optimized design is validated. The results obtained with the numerical methodology described in Part I are checked against pressure measurements and particle image velocimetry (PIV) measurements. The experimental campaign is carried out on a magnified model of a two-legged cooling channel that reproduces the geometrical and aerodynamical features of its numerical counterpart. Both the original profile and the optimized profile are tested. The latter proves to outperform the original geometry by about 36%, in good agreement with the numerical predictions. Two-dimensional PIV measurements performed in planes parallel to the plane of the bend highlight merits and limits of the computational model. Despite the well-known limits of the employed eddy viscosity model, the overall trends are captured. To assess the impact of the aerodynamic optimization on the heat transfer performance, detailed heat transfer measurements are carried out by means of liquid crystals thermography. The optimized geometry presents overall Nusselt number levels only 6% lower with respect to the standard U-bend. The study demonstrates that the proposed optimization method based on an evolutionary algorithm, a Navier–Stokes solver, and a metamodel of it is a valid design tool to minimize the pressure loss across a U-bend in internal cooling channels without leading to a substantial loss in heat transfer performance.

Heat Transfer Performance of an Air-Assisted Impinging Water Jet Under a Fixed Pumping Power Constraint

2013 ◽  
Author(s):  
Daniel Trainer ◽  
Sung Jin Kim
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Heat Transfer Performance ◽  
Plug Flow ◽  
Water Jet ◽  
Air Injection ◽  
Transfer Performance ◽  
Pumping Power ◽  
Two Phase ◽  
Impingement Point

Air injection into a liquid impinging jet has been shown to be a method of improving non-phase change heat transfer rates by up to twice the normal amount. Previous work has shown that there exists an optimal operating point in terms of the volumetric fraction of air injection when the pumping power is held constant because of an optimal two-phase flow pattern. However, previous work focused on heat transfer from the impingement point only, and neglected performance at other points. The present work studies the local heat transfer performance of an air-assisted water jet, at the impingement point and at positions moving radially outward, under constant pumping power conditions. The area-averaged heat transfer is also considered. Heat transfer at the stagnation point is shown to be optimized between β = 0.1∼0.2, where a bubbly flow pattern exists. Nuavg(r/D ≤ 1) is optimized when the flow pattern was plug-flow and off-center peaks in Nur exist. Nuavg(r/D > 1) is optimized when the water is accelerated by the injected air, but splattering is avoided. Flow patterns have no direct effect outside the impingement region.

An Experimental Study of Two Phase Flow in Impinging Micro Channels

2013 ◽  
Author(s):  
Liang-Han Chien ◽  
Han-Yang Liu ◽  
Wun-Rong Liao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Heat Sink ◽  
Heat Transfer Performance ◽  
Experimental Result ◽  
Working Fluid ◽  
Transfer Performance ◽  
Two Phase ◽  
Micro Channels

A heat sink integrating micro-channels with multiple jets was designed to achieve better heat transfer performance for chip cooling. Dielectric fluid FC-72 was the working fluid. The heat sink contained 11 micro-channels, and each channel was 0.8 mm high, 0.6 mm wide, and 12 mm in length. There were 3 or 5 pores on each micro-channel. The pore diameters were either 0.24 or 0.4 mm, and the pore spacing ranged from 1.5 to 3 mm. In the tests, the saturation temperature of cooling device was set at 30 and 50°C, and the volume flow rate ranged from 9.1 to 73.6 ml/min per channel (total flow rate = 100∼810 ml/min). The experimental result showed that heat transfer performance increased with increasing flow rate for single phase heat transfer. For heat flux between 20 and 100 kW/m2, the wall superheat decreases with increasing flow rate at a fixed heat flux. However, the influence of the flow rate diminished when the channels are in two phase heat transfer regime. Except for the lowest flow rate (9.1 ml/min), the heat transfer performance increased with increasing jet diameter/spacing ratios. The best surface had three nozzles of 0.4 mm diameter in 3.0 mm jet spacing. It had the lowest thermal resistance of 0.0611 K / W in the range of 200 ∼ 240 W heat input.

Research Progress of Three Kinds of Enhanced Heat Transfer Structures

2013 ◽  
Vol 711 ◽  
pp. 219-222
Author(s):  
Zhan Shu He ◽  
Xiao Long Liu ◽  
Xue Fei Yang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Metal Foam ◽  
Porous Metal ◽  
Research Direction ◽  
Research Progress ◽  
Future Research ◽  
Transfer Performance ◽  
Enhanced Heat Transfer

In order to transfer heat as much as possible through a unit area in unit time, this paper introduces three enhanced heat transfer structures, namely microchannel, open-celled metal foam and open-celled sintered porous metal. From two aspects of the heat transfer performance and the flow resistance, this paper reviews their research progress. Among three kinds of enhanced heat transfer structures, open-celled sintered porous metal has the best heat transfer performance, followed by open-celled metal foam and micro-channel. While, the sequence of the pressure drop of three kinds of enhanced heat transfer structures is in the reverse order. Thus, Enhanced heat transfer Structures with good heat transfer performance and small pressure drop are the future research direction.

scholarly journals Field Study on the Air-Side Heat Transfer Performance of Copper Finned-Flat Tubes for Heavy-Duty Truck Radiators

2021 ◽  
Vol 39 (5) ◽  
pp. 1451-1459
Author(s):  
Jose Canazas
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heavy Duty ◽  
Cooling Systems ◽  
Heavy Duty Truck ◽  
Flat Tubes

Heavy-duty truck cooling systems have been given low importance in the enhancement and research of heat transfer performance since off-highway conditions are hard to evaluate in laboratory essays or CFD studies. The present work is performed to evaluate the heat transfer performance of copper finned-flat tubes used in heavy-duty truck radiators. Parameters were measured in the field of two heavy-duty truck engines cooling systems. In both vehicles water is used as the cooling fluid. The results showed that the Air convective heat transfer coefficient and Overall heat transfer coefficient on the air side decreases as the Reynolds Number decreases and increases as passing through the first row to the fourth row. Additionally, the mass air flow and heat transfer rate have very high values in comparison from normal automotive radiators' operative conditions, since heavy-duty truck radiators require a large heat transfer rate. The analysis presented in this paper was used for a heavy-duty truck radiator but can be extended to any equipment with finned flat tubes. A more accurate study should be done considering vibrations and different environmental conditions.

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