Thermal Science and Engineering - From Macro to Nano in 200 Years Avram Bar-Cohen University of Maryland, Distinguished Univ Prof AIHTC, President IHTC-15 15th International Heat Transfer Conference August 10-15, 2014 Kyoto, Japan
•   Brief History of Heat Transfer • Genesis • Foundations of Conduction (Macro) • Foundations of Convection (Macro) • United States • Japan •   Assembly of International Heat Transfer Conferences •   Thermal Packaging of Electronics (Micro to Nano)
Newton's Principia (1687) . Transient heat transfer experiments . Devised linseed oil thermometer • Rate of cooling proportional to temperature difference (1701) – Newton's Law of Cooling . Distinction between natural and forced convection
. . . Established thermometric standards for environmental measurements, 1714 Fahrenheit’s thermometer consisted of vertical glass tube, filled with mercury Temperature scaled to make environmental temperatures positive; divided water freezing point (32°F) to boiling point (212°F) into 180 segments
. Clear distinction between heat and temperature . Observed that each material has it’s own “capacity for heat” • Empirically quantified “latent heat” of fusion, later latent heat of evaporation
Father of Thermal Engineering . Applied Black’s observations to create efficient & powerful steam engine . Watt steam engine far more powerful than Newcomen steam engine . Separated condenser from body of engine •   Ushered in the Industrial Age!
Joule's paddlewheel and calorimeter, proved that heat and mechanical work are forms of energy . Discovered relationship between mechanical work and heat . Officially refuted Caloric Theory with careful experiments . . “Joule Equivalent” - mechanical equivalency of heat “Joule heating” with electricity • Experimentally confirmed 1st law of Thermodynamics (Energy Conservation)
Described three fundamental properties of heat flow: Joseph Fourier (1768-1830) Father of Thermal Science 1. Heat Capacity 2. Interior Conductibility 3. Exterior Conductibility (surface heat exchange) H fi
Joseph Fourier (1768-1830) Obsessively interested in heat transfer after joining Napoleon's army in Egypt (1798) . . Fourier's Law derived in On the Propagation of Heat in Solid Bodies (1807) Added heat transfer coefficient to Newton's Law of Cooling .
Joseph Fourier (1768-1830) . Fourier’s memoir revised into “Prize Essay” and won the Grand Prize in Mathematics from the Institute de France in 1812 . General form of  interior conduction derived in “Prize Essay” Compilation of Fourier's work published in 1822, The Analytical Theory of Heat .
T DS Dt
. Navier-Stokes equation derived independently by Stokes (England) and Navier (France) in the early 1800's . Energy equation was arguably derived with the 1833 Fourier-Poisson differential equation

1881: Lorenz
•  Buoyancy-induced convective transport 1885: Graetz • Thermal entrance region in pipe flow 1842: Reynolds • Laminar & turbulent flow • Turbulent heat transfer 1904: Prandtl • Boundary layer concept • Mixing length model 1915: Nusselt • Convective heat transfer •  Underlying dimensionless groups 1920's-30's: Max Jakob •  Steam thermal transport – boiling & condensation porne Reynolds (1842- 1912)
hL Convective Conductive K Dimensionless Nusselt Number . . . In 1907, received doctorate in Mech. Eng. from Munich Technical University, Germany In 1915, published prominent paper: The Basic Laws of Heat Transfer Proposed dimensionless groups in convective HT using similarity theory . Established a foundation for subsequent formidable advances in convective, radiative, and two-phase heat transfer across the world
J-Factor Analogy . First US Heat and Mass Transfer Effort: University of Delaware's Chemical Engineering Department . In 1936, Colburn published “Colburn Analogy” and heat transfer “J-Factor” . Colburn’s shell-and-tube HX research nurtured US HX industry
Theodore von Karman (1904-1955) . von Karman escaped Germany when the Nazi regime started purging Jewish professionals in 1933 . Accepted Cal Tech's invitation to become head of Guggenheim Aeronautics Lab, later renamed JPL . Created foundation for American rocket and missile technology Founded Aerojet Corporation, advised NASA
Jakob Dimensionless Number Max Jakob (1879-1955) . . . . In 1936, fled Nazi Germany to avoid persecution, after illustrious 25 year career Over 200 technical publications with profound heat transfer impact In 1938, became professor of Mech. Eng. at IIT and founded the Heat Transfer Lab Textbook and a two-volume treatise on heat transfer had a profound influence on heat transfer education and research in the United States
Stothe P. Kezios (1921-2005) . “Mid-West” thermal engineering initially driven by Jakob at IIT . 1937-1938 Heat Transfer lectures influenced several prominent academic leaders: Stoethe P. Kezioss (ITT), George Hawkins (Purdue), and Richard Jordan (Minnesota) •   Kezios became chair of Heat Transfer Division (1958-59), 1st editor of ASME Journal of Heat Transfer (1963), and ASME's 96th president (1977-78)
. Hawkins drove from Purdue to IIT to attend Jakob's 1937-1938 lectures Dean of Engineering at Purdue from 1953 to 1967 . . Established world class heat transfer program at Purdue
Jordan became head of Minnesota's Mechanical Engineering Department (1950) . • Persuaded Eckert to join department and establish the Thermodynamics and Heat Transfer Laboratory (THTL) at Minnesota in 1951 . THTL seminal contributions by E.M. Sparrow, Warren Ibele, Richard Goldstein, James Hartnett, Patankar, Simon, Bar-Cohen,... Mid-West key to formation of AIHTC and ICHMT
William H. McAdams (1892-1975) . “East Coast” thermal engineering initially driven by McAdams at MIT . Authored “Heat Transmission” in 1933 – primary teaching and reference book . Warren Rohsenow joined MIT in 1946, established Heat Transfer Laboratory Expanded research of boiling and condensation . . Mentored numerous luminaries: Clark, Griffith, Mikic, Bergles, .......
(Turbulent Pipe Flow) . . “West Coast” thermal engineering initially driven by Llewellyn Boelter at UC Berkeley Moved from EE to ME in 1923, formed heat transfer program with Floyd Cherry, Harold Johnson, and Robert Martinelli, . Boelter produced analytic “Heat Transfer Notes” and Dittus-Boelter heat transfer coefficient correlation for Turbulent pipe flow
. Professor at Tohoku University from 1921 to 1956 . Pioneer in the understanding of boiling phenomena • Established the Nukiyama boiling curve in the 1930's
. Professor of Tokyo Institute of Technology from 1961 to 1983 . Significant impact on heat transfer community with a wide range of subjects: . Convective heat transfer, magneto-hydrodynamic power generation, plasma, high-temp, condensation, geothermal, and ocean thermal energy . Emphasized broad applications of thermal science and physics-based approach
Beginning of IHTC:
• “International Discussion on Heat Transfer”– London & Atlantic City, 1951 “International Heat Transfer Conference” – Colorado, 1961 . . Companion meeting for USSR researchers in London, 1962 •    4-Year IHTC cycle began with 3 rd conference – Chicago, 1966 • Lead by Hartnett, Rohsenow, Eckert, Kezios, and Kutateladze . William Begell as publisher
Avram Bar-Cohen Conference Chair Kyoto, Japan (2014) Washington, DC, USA (2010) Sydney, Australia (2006) Grenoble, France (2002) Kyongju, Korea (1998) Brighton, UK (1994) Jerusalem, Israel (1990) San Francisco, USA (1986) Munich, Germany (1982) Toronto, Canada (1978) Tokyo, Japan (1974) Versailles, France (1970) Chicago, USA (1966) Conference Chair Conference Chair Members of AIHTC国E � ik. (18)
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Gen-2b: Attached Coolers, '80-… Heat Sink Era ’85-… . Optimized heat sinks Improved TIM's . . Air flow paths GOAL: Reduce øça “case-to-air” resistance
9" hot spot = 500 W/cm² (2 x 2 mm) q" avg. = 50 W/cm² (40 x 40 mm) On-Chip Hot Spots in IBM 3D Chip Stack
Typical 3D Chip Stacks (2005)
Vision: Provide localized thermal management within the device substrate to increase Power, Speed, Reliability High Thermal Conductivity Substrates • Integrate lattice-mismatched heat spreaders • Eliminate thermal interface resistance • Match coefficient of thermal expansion of electronic material
Embedded Thermal Vias
• Micro-machined vias within ~1 micron of junction • High thermal conductivity conformal fill materials • Low coupling resistance for junction-to- thermal via, thermal via-to-heat sink High Thermal Conductivity Over-layer for Heat Removal from Topside of Devices • High thermal conductivity in deposited material • Conformal coverage with no gaps Eliminate impact on device electrical properties due to time varying dielectric constant of liquid
Distribution Statement A, Approved For Public Release, Distribution Unlimited

Intrachip:
. Cooling fluid flowing through microchannels fabricated directly into chip
Interchip:
. Cooling fluid flowing through the microgap between chips in 3D chip stacks . . Highly Efficient Cooling Chip Heat Flux > 1kW/cm2 . Chip Temperature Rise < 30K . Hot Spot Heat Flux > 5kW/cm2 . Hot Spot Temperature Rise < 5K
Program Objective:
. Provide the fundamental thermofluid building blocks for the utilization of Intra and Interchip evaporative cooling in 3D DoD electronics

Challenges:
. Complete the Inward Migration of Thermal Packaging . Extract heat directly from device, chip, and package . Place thermal management on an equal footing with functional design and power delivery Benefits: . Allow electronic systems to reach material, electrical, optical limits . Reduce SWaP-C for comparable performance . Lead the way to integrated, intelligent system co-design
Enabling Technologies:
. Microfluidics – convective and evaporative Thermal interconnects – active/passive . . . Thermal Co-Design Microfabrication – channeling, hermeticity
Distribution Statement A, Approved For Public Release, Distribution Unlimited

• Long and illustrious history for international thermal science and engineering (TSE) •   AIHTC plays key role in nurturing community •  TSE efforts started in 1800's with Steam Engines, Furnaces, and moved to HVAC, Gas Turbines, and Satellites •   Microelectronics and microfabrication pushed TSE to micro-scale •  Embedded Cooling and nanofabrication necessitate TSE R&D and design at nano-scale.
口口口口口口口口口口口口口Born, NYC 1935 SB, SM -1958, PhD 1962, MIT Married Priscilla, “Penny,” Maule 1960 Ford Asst Prof, Mech Eng, MIT 1963 Professor, Mech Eng, Ga Tech, 1969 Chair, Mech Eng, Iowa State, 1972 Professor, Mech Eng, RPI, 1986 Dean, College of Eng, RPI, 1989-1992 President, ASME, 1990-1991 NAE member, 1992 Published 400 papers, 26 books Graduated 82 PhD and MS students Survived by wife Penny, sons Eric and Dwight, and 5 grandchildren AEB: “Two are better than one…” Ecclesiastes, 4:9 Thank You !! In Memory of: Professor Yoram Zvirin (1942 – 2013) Mechanical Engineering, Technion- Israel Institute of Technology Academic and public service Head, Technion Transportation Research Institute Head, Internal combustion engines lab Director, Israel National Museum of Science Chairman, Solar World Congress 1999 (Jerusalem) Secretary, Assembly of IHTC 9, Jerusalem, Israel 1990 ICHMT Scientific Council Interest areas and contributions Combustion, fuel efficiency, alternative fuels, emissions Transportation systems, autonomous vehicles, environmental impacts Radiative heat transfer, conjugate heat transfer Solar collectors, Natural convection in thermosyphons IHTC15 Aug. 2014 41
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. . HT at MIT progressed with: John A. Clark, Peter Griffith, Bora Mikic, and Arthur Bergles Avram Bar-Cohen – Distinguished UMD Professor – completed PhD with Art Bergles in 1971 In 1992, John Lienhard V upgraded MIT’s heat transfer laboratory . Renamed the Rohsenow Heat and Mass Transfer Laboratory

SOA: Remote Cooling
•  Heat removed far from chip •  Low ΔT for heat transfer to ambient • Limits power dissipation
ICECool: Intrachip/Interchip Cooling
•  Heat is removed at the chip • High ΔT for heat transfer to ambient •  Overcome SOA component thermal limits at Dissipated Current SOA High Conductivity Thermal Vias Liquid Dielectric Microfluidics
Areas of Focus
• Integrated Microfluidics • Thermal Substrates and Interconnects • Thermal Co-Design Manifolded Evaporative Dielectric On-Chip TECs Liquid Manifolded Evaporative Microfluidics Microfluidics Microfluidics
Technology Goals
• GaN MMIC PAs with 10x output power •  Microprocessors with up to 10x  frequency
Distribution Statement A, Approved For Public Release, Distribution Unlimited

Gen-1b: Rack Cooling ‘64-’85 . DIP’s and SMT’s on PCB’s . PCB's in Card Cages GOAL: Control rack air temperature

Nanoelectronics Era, 2000-...
. GHz-level CMOS with features below 100nm . . Power dissipation increasing, distinct on-chip “hot spots” on Si/compound semiconductors Emergence of homogeneous/heterogeneous “chip stacks” denying access to back of chip for “thermal solution” GOALS: . Remove large flux . Reduce/eliminate on-chip “hot spots” . Extract high heat density High Power Hot Spots 3-Dimensional Triple Threat