Abstract Data centers are critical to the functioning of modern society as they host digital infrastructure. However, data centers can consume significant amounts of energy, and a substantial amount of this energy goes to cooling systems. Efficient thermal management of information technology equipment is therefore essential and allows the user to obtain peak performance from a system and enables higher equipment reliability. Thermal management of data center electronics is becoming more challenging due to rising power densities at the chip level. Cooling technologies like single-phase immersion cooling allow overcoming many such challenges owing to their higher thermal mass, lower fluid pumping powers, and potential component reliability enhancements. It is known that immersion cooling deployments require extremely low coolant flow rates, and, in many cases, natural convection can also be used to sufficiently dissipate the heat from the hot server components. It, therefore, becomes difficult to ascertain whether the rate of heat transfer is being dominated by forced or natural convection. This may lead to ambiguity in choosing an optimal heat sink solution and a suitable system mechanical design due to unknown flow regimes, further leading to sub-optimal system performance. Mixed convection can be used to enhance heat transfer in immersion cooling systems. The present investigation quantifies the contribution of mixed convection using numerical methods in an immersion-cooled server. An open compute server with dual CPU sockets is modeled on Ansys Icepak with varying power loads of 115W, 160W and 200W. The chosen dielectric fluid for this single-phase immersion-cooled setup is EC-100. Steady-state Computational Fluid Dynamics (CFD) simulations are conducted for forced, natural, and mixed convection heat transfer in a thermally shadowed server configuration at varying inlet flow rates. A baseline heat sink and an optimized heat sink with an increased fin thickness and reduced fin count are utilized for performance comparison. The effect of varying Reynolds number and Richardson number on the heat transfer rate from the heat sink is discussed to assess the flow regime, stability of the flow around the submerged components which depends on the geometry, orientation, fluid properties, flow rate and direction of the flow. The dimensionless numbers’ influence on heat transfer rate from a conventional air-cooled heat sink in immersion versus an immersion-optimized heat sink is also compared. The impact of server orientation on heat transfer behavior for the immersion optimized heat sink is also studied on heat transfer behavior for the immersion optimized heat sink.
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Heat Transfer Coefficients in Perforated Fins
Three-dimensional steady state and incompressible flow and heat transfer are simulated over a perforated fin to validate the numerical heat transfer coefficients with experimental data. The validated numerical approach is necessary to investigate the complex flow patterns over perforations, which is difficult and costly to capture through experiments. Perforations with square cross sections are distributed equidistantly along the length of the fin. The simulation is performed for a laminar airflow with Reynolds numbers between 992 and 1722. The Navier-Stokes and energy equations are discretized through the finite volume approach, and the pressure and velocity components are coupled by the SIMPLEC algorithm. Excellent agreements (below 6.1%) are obtained by comparing average numerical and experimental Nusselt numbers. Suggestions for future research to address the current gaps in understanding the thermo-fluid mechanism in perforated fins are provided.
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- Award ID(s):
- 1914751
- PAR ID:
- 10332057
- Date Published:
- Journal Name:
- Proceedings of the 9th International Conference on Fluid Flow, Heat and Mass Transfer (FFHMT’22)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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