Two-phase mini-thermosyphon electronics cooling, Part 4: Application to 2U servers

This paper is the fourth part of the present study on two-phase mini-thermosyphon cooling. As mentioned in the first three parts, gravity-driven cooling systems using microchannel flow boiling can become a long-term scalable solution for cooling of datacenter servers. Indeed, the enhancement of thermal performance and the drastic reduction of power consumption together with the possibility of energy reuse and the inherent passive nature of the system offer a wide range of solutions to thermal designers. While Part 1 presented the first-of-a-kind low-height microchannel two-phase thermosyphon test results and Parts 2 and 3 showed the system scale steady and dynamic modeling and simulation results associated with this design using our inhouse simulator, Part 4 deals here with an end-user application, i.e. the cooling of a 2U server. The dynamic code of Part 3 is used to model the behavior of a mini-thermosyphon that would fit within the height of a 2U server (8.9cm high), while respecting the other geometric constraints (positions of the processors, distance of the processors to the back of the blade, etc.). Thus, the simulated system consists of two parallel multi-microchannel evaporator cold plates on the top of two chips of about 11cm2, a riser, a common water-cooled micro-condenser at the back of the blade, a liquid accumulator and a downcomer (including the piping branches to/from the two cold plates). First, an analysis of the steady-state operation highlights multiple solutions from which one is stable and one is unstable. Then, the influences of few parameters such as refrigerants, piping diameters, water coolant inlet temperature and flow rates, filling ratio and heat flux are evaluated. Simulations with unbalanced heat loads on the two chips being cooled in parallel then show the desirable flow distribution obtained in such gravity-driven systems. Finally, temporal heat load and water coolant flow rate disturbances are simulated and discussed. Noting all of these numerous influences on optimal mini-thermosyphon operation, the need for a accurate and detailed simulation code, benchmarked versus actual system tests, is seen to be imperative for attaining a good, reliable, robust design.

[1]  Martine Baelmans,et al.  Numerical model of a two-phase microchannel heat sink electronics cooling system , 2012 .

[2]  Jackson Braz Marcinichen,et al.  Recent Advances in On-Chip Cooling Systems: Experimental Evaluation and Dynamic Modeling , 2014 .

[3]  R. Shah.  Laminar Flow Forced convection in ducts , 1978 .

[4]  Bruno,et al.  Compact Thermosyphon Heat Exchanger for Power Electronics Cooling , 2013 .

[5]  D. Zarefsky.  The U.S. and the world , 2014 .

[6]  Alessandro Franco,et al.  Experimental analysis of Closed Loop Two Phase Thermosyphon (CLTPT) for energy systems , 2013 .

[7]  John T. Wen,et al.  Vapor compression refrigeration cycle for electronics cooling – Part I: Dynamic modeling and experimental validation , 2013 .

[8]  Jackson Braz Marcinichen,et al.  Reasons to Use Two-phase Refrigerant Cooling , 2011 .

[9]  Renwei Mei,et al.  Instability phenomena in a two-phase microchannel thermosyphon , 2009 .

[10]  I. E. Idel'cik.  Memento des Pertes de Charge , 1999 .

[11]  Jarosław Mikielewicz,et al.  Natural Circulation in Single and Two Phase Thermosyphon Loop with Conventional Tubes and Minichannels , 2011 .

[12]  M. M. Yovanovich,et al.  Pressure Drop in Laminar Developing Flow in Noncircular Ducts: A Scaling and Modeling Approach detailed review and analysis of the hydrodynamic characteristics of laminar developing , 2009 .

[13]  J. Thome,et al.  Flow Boiling of R134a in a Multi-Microchannel Heat Sink With Hotspot Heaters for Energy-Efficient Microelectronic CPU Cooling Applications , 2011, IEEE Transactions on Components, Packaging and Manufacturing Technology.

[14]  Alessandro Franco,et al.  Closed Loop Two-Phase Thermosyphon of Small Dimensions: a Review of the Experimental Results , 2012 .

[15]  Ho-Young Kwak,et al.  Experimental Study on Closed-Loop Two-Phase Thermosyphon Devices for Cooling MCMs , 2001 .

[16]  B. S. Petukhov.  Heat Transfer and Friction in Turbulent Pipe Flow with Variable Physical Properties , 1970 .

[17]  T. Brunschwiler,et al.  Waste heat recovery in supercomputers and 3D integrated liquid cooled electronics , 2012, 13th InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems.

[18]  Chih-Chung Chang,et al.  Two-Phase Closed-Loop Thermosyphon for Electronic Cooling , 2010 .

[19]  Jackson Braz Marcinichen,et al.  Advances in Electronics Cooling , 2013 .

[20]  R. Mei,et al.  A Flow Boiling Microchannel Evaporator Plate for Fuel Cell Thermal Management , 2007 .

[21]  John R. Thome,et al.  Flow pattern-based flow boiling heat transfer model for microchannels , 2013 .

[22]  A. Hindmarsh.  LSODE and LSODI, two new initial value ordinary differential equation solvers , 1980, SGNM.

[23]  A. Cavallini,et al.  Update on Condensation Heat Transfer and Pressure Drop inside Minichannels , 2006 .

[24]  V. Gnielinski.  New equations for heat and mass transfer in turbulent pipe and channel flow , 1976 .

[25]  Elumalai Natarajan,et al.  Thermal Performance of a Two-Phase Closed Thermosyphon for Waste Heat Recovery System , 2010 .

[26]  S. H. Noie.  Heat transfer characteristics of a two-phase closed thermosyphon , 2005 .

[27]  Jonathan Olivier,et al.  Two-phase flow of refrigerants in 85 μm-wide multi-microchannels: Part II ― Heat transfer with 35 local heaters , 2011 .

[28]  M. Yovanovich,et al.  Laminar Forced Convection Heat Transfer in the Combined Entry Region of Non-Circular Ducts , 2004 .

[29]  John R. Thome,et al.  Towards development of a passive datacenter cooling technology: On-server thermosyphon cooling loop under dynamic workload , 2014, Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm).