Experimental Characterization of Two-Phase Cold Plates Intended for High Density Data Center Servers Using a Dielectric Fluid

2021 ◽  
Author(s):  
Bharath Ramakrishnan ◽  
Cong Hiep Hoang ◽  
Sadegh Khalili ◽  
Yaser Hadad ◽  
Srikanth Rangarajan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Dielectric Fluid ◽  
Base Temperature ◽  
Phase Flow ◽  
Cold Plate ◽  
Two Phase ◽  
Cold Plates

Abstract High Performance Computing (HPC) data centers demand cutting edge cooling techniques like direct contact liquid cooling (DCLC) for safe and secure operation of their high-power density servers. Two-phase flow boiling heat transfer technique is widely believed to address the heating problem posed by HPC racks. In this study, a novel liquid cooled cold plate containing microchannel and jet impingement arrangement was characterized for its two-phase flow and thermal behavior. A sophisticated bench top setup involving a mock package was developed to carry out the experiments in a controlled fashion using a dielectric fluid Novec/HFE-7000. Two-phase flow boiling in cold plates which has a strong dependency on surface phenomena was carefully studied at various levels of inlet pressure, subcooling, flow rates and heat flux levels to the mock package. A resistance network was invoked to determine the average heat transfer coefficient at various exit qualities estimated by energy balance equation. While the results make it evident that, the high heat generating components can be kept at operable conditions using the two-phase cooling; a deeper insight at the outcomes could pave way for more energy efficient cold plate designs. The experiment was carried out with a large heated surface of 6.45 cm2 and maximum dissipated heat flux was around 63.6 W/cm2 corresponding to chip power of 410 W. Base temperature was kept below 75 oC and pressure drop did not exceed 21 kPa.

scholarly journals Evaluation of Heat Transfer Coefficient of Two-Phase Flow Boiling with R290 in Horizontal Mini Channel

2021 ◽  
Vol 88 (3) ◽  
pp. 88-95
Author(s):  
Ronald Akbar ◽  
Jong Taek Oh ◽  
Agus Sunjarianto Pamitran
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
The Heat Transfer Coefficient

Various experiments have been conducted on the heat transfer coefficient of two-phase flow boiling in mini channel tubes. In addition to obtaining data on the heat transfer coefficients through experiments, many researchers have also compared their experimental data using existing correlations. This research aims to determine the characteristics of the heat transfer coefficient of refrigerant R290 from the data used by processing and knowing the best heat transfer coefficient correlation in predicting the experimental data so that the results are expected to be a reference for designing a heat exchanger or for further research. The experimental data predicted is the two-phase flow boiling in a horizontal tube 3 mm diameter, with the mass flux of 50-180 kg/m2s, heat flux of 5-20 kW/m2, saturation temperature of 0-11 °C, and vapor quality of 0-1. The correlation used in this research is based on the asymptotic flow model, where the model is a combination of the nucleate and convective flow boiling mechanisms. The results show an effect of mass flux and heat flux on the experimental heat transfer coefficient and the predicted R290 heat transfer coefficient with asymptotic correlations had a good and similar result to the experimental data.

scholarly journals Peripheral Heat Transfer Coefficient during Flow Boiling: Comparison between 2-D and 1-D Data Reduction and Discussion about Their Applicability

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4483 ◽  
Author(s):  
Rita Mastrullo ◽  
Alfonso William Mauro
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Data Reduction ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Operating Conditions ◽  
Phase Flow ◽  
Two Phase

This paper presents a critical analysis of possible data reduction procedures for the evaluation of local heat transfer coefficient during flow boiling experiments. The benchmark method using one-dimensional (1-D) heat transfer in a heated tube was compared to a new data reduction method in which both radial and circumferential contributions to the conductive heat transfer inside a metal tube are considered. Using published experimental flow boiling data, the circumferential profiles of the wall superheat, inner wall heat flux, and heat transfer coefficients were independently calculated with the two data reduction procedures. The differences between the two methods were then examined according to the different heat transfer behavior observed (symmetric or asymmetric), which in turn was related to the two-phase flow regimes occurring in a channel during evaporation. A statistical analysis using the mean absolute percentage error (MAPE) index was then performed for a database of 417 collected flow boiling data taken under different operating conditions in terms of working fluid, saturation temperature, mass velocity, vapor quality, and imposed heat flux. Results showed that the maximum deviations between the two methods could reach up to 130% in the case of asymmetric heat transfer. Finally, the possible uses of the two data reduction methods are discussed, pointing out that the two-dimensional (2-D) model is the most reliable method to be employed in the case of high-level modeling of two-phase flow or advanced design of heat exchangers and heat spreader systems.

Heat Flux Measurement Method of Two-Phase Flow in SRM

2012 ◽  
Vol 152-154 ◽  
pp. 883-888
Author(s):  
Xiang Yu Zhang ◽  
Guo Qiang He ◽  
Pei Jin Liu ◽  
Jiang Li
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Two Phase Flow ◽  
Thermal Protection ◽  
Flux Measurement ◽  
Combustion Products ◽  
Phase Flow ◽  
Solid Rocket Motor ◽  
Two Phase ◽  
Heat Flux Measurement

Accurate information on heat transfer data of combustion products in the solid rocket motor chamber is a crucial prerequisite for the engine thermal protection. A measurement technique was well developed to acquire steady-state heat flux data of two-phase flow and was used successfully in the hostile environment. Experimental heat flux measurement has been obtained with an innovative designed instrument by simulating the flow field of complex charging configuration. The total heat flux of combustion products in the chamber was brought away by the coolant and calculated by its enthalpy rise in this device. The data could be used to analyze the heat transfer phenomena in SRMs and provide boundary condition for establishing insulation erosion model.

Numerical Simulation of Subcooled Flow Boiling Heat Transfer in Helical Tubes

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Jong Chull Jo ◽  
Woong Sik Kim ◽  
Chang-Yong Choi ◽  
Yong Kab Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Steam Generator ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Heat Transfer Analysis ◽  
Normal Operation ◽  
Phase Flow ◽  
Two Phase ◽  
Side Flow

This paper addresses the numerical simulation of two-phase flow heat transfer in the helically coiled tubes of an integral type pressurized water reactor steam generator under normal operation using a computational fluid dynamics code. The shell-side flow field where a single-phase fluid flows in the downward direction is also calculated in conjunction with the tube-side two-phase flow characteristics. For the calculation of tube-side two-phase flow, the inhomogeneous two-fluid model is used. Both the Rensselaer Polytechnic Institute wall boiling model and the bulk boiling model are implemented for the numerical simulations of boiling-induced two-phase flow in a vertical straight pipe and channel, and the computed results are compared with the available measured data. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. Both the internal and external turbulent flows are simulated using the standard k-ε model. From the results of the present numerical simulation, it is shown that the bulk boiling model can be applied to the simulation of two-phase flow in the helically coiled steam generator tubes. In addition, the present simulation method is considered to be physically plausible in the light of discussions on the computed results.

Two Large-Amplitude/Long-Period Oscillating Boiling Modes in Silicon Microchannels

2003 ◽  
Author(s):  
H. Y. Wu ◽  
Ping Cheng
Keyword(s):  
Heat Flux ◽  
Water Temperature ◽  
Large Amplitude ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Saturation Temperature ◽  
Phase Flow ◽  
Two Phase ◽  
Long Period

A simultaneous visualization and measurement study has been carried out to investigate flow boiling of water in the 8 parallel silicon microchannels heated from below. It is found that there are two large-amplitude/long-period oscillating boiling modes exist in microchannels depending on the amounts of heat flux and mass flux. When the outlet water temperature is at saturation temperature and the wall temperatures are superheated, while the inlet water temperature is still subcooled, a Liquid/Two-phase Alternating Flow (LTAF) mode appears in the microchannels. This LTAF mode disappears when the inlet temperatures reaches the saturation temperature. As the heat flux is further increased such that the outlet water is superheated while the inlet water temperature is oscillating between subcooled and saturation temperature, a Liquid/Two-phase/Vapor Alternating Flow (LTVAF) mode begins. During these two unstable boiling modes, there are large-amplitude and long-period oscillations of water and wall temperatures with respect to time. Bubbly flow as well as some peculiar two-phase flow pattern are observed during the two-phase flow periods of the two unstable modes in the microchannels.

Flow Boiling Heat Transfer and Two-Phase Flow Instability of Nanofluids in a Minichannel

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Leyuan Yu ◽  
Aritra Sur ◽  
Dong Liu
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Flow Instabilities ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Boiling Heat Transfer

Single-phase convective heat transfer of nanofluids has been studied extensively, and different degrees of enhancement were observed over the base fluids, whereas there is still debate on the improvement in overall thermal performance when both heat transfer and hydrodynamic characteristics are considered. Meanwhile, very few studies have been devoted to investigating two-phase heat transfer of nanofluids, and it remains inconclusive whether the same pessimistic outlook should be expected. In this work, an experimental study of forced convective flow boiling and two-phase flow was conducted for Al2O3–water nanofluids through a minichannel. General flow boiling heat transfer characteristics were measured, and the effects of nanofluids on the onset of nucleate boiling (ONB) were studied. Two-phase flow instabilities were also explored with an emphasis on the transition boundaries of onset of flow instabilities (OFI). It was found that the presence of nanoparticles delays ONB and suppresses OFI, and the extent is correlated to the nanoparticle volume concentration. These effects were attributed to the changes in available nucleation sites and surface wettability as well as thinning of thermal boundary layers in nanofluid flow. Additionally, it was observed that the pressure-drop type flow instability prevails in two-phase flow of nanofluids, but with reduced amplitude in pressure, temperature, and mass flux oscillations.

Sign in / Sign up

Export Citation Format

Share Document