Il Peso del Thermal Management nei LED

Transcription

1 Il Peso del Thermal Management nei LED Heat Pipe: high performance thermal solution Ing. Manca Claudio F.lli POLI S.r.l. Padova Ottobre 2013 Titolo Intervento 1/N

2 Heat pipes in the history The Heat pipe precursor was the Perkins Tube Form 1800 up to 1910 different types of Two phase wickless tube have been patented the1944 Gaugler introduced the sintered wick element GM US Patent Padova Ottobre 2013 Titolo Intervento 2/N

3 Heat pipes in the history In the 1963 Grover patented a device. He used a Wire Mesh Wick G. M. GROVER U.S. Patent N 3,229,759 Grover includes the experimental data with the operating limits for a device utilizing the sodium as fluid He used, for the first time, the name Heat Pipe Padova Ottobre 2013 Titolo Intervento 3/N

4 International Heat Pipes Conference 1 IHPC Stuttgart (Germany) IHPC Bologna (Italy) IHPC Palo Alto CA (USA) IHPC London (UK) IHPC Tsukuba (Japan) IHPC Grenoble (France) IHPC Minsk (Belarus) IHPC Beijing (China) IHPC Albuquerque (USA) IHPC Stuttgart (Germany) IHPC Tokyo (Japan) IHPC Moscow (Russia) papers 13 IHPC Shangai (China) IHPC Florianopolis (Brazil) papers 15 IHPC Clemson, SC (USA) papers 16 IHPC Lyon (France) papers 17 IHPC Kanpur (INDIA) 2013 Padova Ottobre 2013 Titolo Intervento 4/N

5 What is an Heat Pipe Copper ampoule Wick material in which the fluid moves due to microcapillarity Inner cavity in which the vapour moves Internally a little bit of fluid (water) for the heat transfer Padova Ottobre 2013 Titolo Intervento 5/N

6 How an Heat pipe works Transition vapour liquid Transition liquid vapour Padova Ottobre 2013 Titolo Intervento 6/N

7 Methods to bring back the liquid to the evaporator The condensed liquid in the pipe must be carried back to the evaporator to feed the thermal transfer cicle METHOD GRAVITY FORCE WICK FORCE ELECTRODYNAMIC FORCE CENTRIPETAL FORCE OSMOTIC FORCE MAGNETIC FORCE DEVICE THERMOSYPHONS HEAT PIPES ELECTODYNAMIC HEAT PIPES ROTATIONAL HEAT PIPES OSMOTIC HEAT PIPES MAGNETIC FLOW HEAT PIPES Padova Ottobre 2013 Titolo Intervento 7/N

8 Classification Heat Pipes Thermosyphons 1. HEAT PIPES 2. LOOP HEAT PIPES (LHP) 3. CAPILLARY PUMPED LOOPS 4. FLAT HEAT PIPES 1. CLOSED THERMOSYPHON 2. LOOP THERMOSYPHON (LT) 3. ANTIGRAVITY THERMOSYPHON 5. MINI & MICRO HEAT PIPES 6. GROOVED HEAT PIPES 7. OSCILLATING HEAT PIPES 8. PULSATING HEAT PIPES (PHP) Padova Ottobre 2013 Titolo Intervento 8/N

9 Thermal resistance Model propoesd by prof. LaTrofa / Filippeschi Pisa University T Tcoldair R = hotair = C W W / R 1 R 2 R 3 R 4 R 5 R 6 R 7 R 8 R 9 Wall Convection Hot Gas Wall Conduction Capillary Thermal Transfer Liquid Vapor Interface Thermal gradient in the Vapour pipe Vapour Liquid interface (condenser) Capillary Thermal Transfer (condenser) Wall Conduction (condenser) Wall Convection Cold Gas (condenser) Padova Ottobre 2013 Titolo Intervento 9/N

10 Thermal resistance Vs Heat pipe length Source Enertron Padova Ottobre 2013 Titolo Intervento 10/N

11 Temperature drop across the Heat Pipe Padova Ottobre 2013 Titolo Intervento 11/N

12 They are passive Heat pipes features They do not need any extra power to work It is the input heat to activate the thermal cycle They can move the heat up to 20 meters They can be used both in cryogenic and in High temperature applications Environment operative condition They can work up to 9g of acceleration And with 34 g random in shock and vibration They can transerf thermal loads from Watts up to Megawatts Padova Ottobre 2013 Titolo Intervento 12/N

13 Diametro Example of power/dimension relationship CRS-5000 Series Operating Temperature (mid point between Evaporator and Condenser Chambre) Φ mm +20 C +40 C +60 C +80 C +120 C Note: heat-pipes operating in a horizontal position Dati CRS Engineering per la serie CRS-5000 For example a unit of 10 mm diameter which operates in horizontal position with the operating temperature of 60 C (for example halfway between 80 C of the hot side and 40 C of a possible ambient temperature) can carry 143 watts of thermal energy. Padova Ottobre 2013 Titolo Intervento 13/N

14 Operating limits Padova Ottobre 2013 Titolo Intervento 14/N

15 LED Lamp thermal management Faults statistics for electronic systems For every 10 C increase in temperature the duration of the expected life of the electronic device decreases by about 50% The LED is an electronic device and follows the same law Padova Ottobre 2013 Titolo Intervento 15/N

16 Relative Luminous flux Vs Junction temperature Source Cree Padova Ottobre 2013 Titolo Intervento 16/N

17 Thermal management of LED engines These are the reasons why LEDs require dissipation High power LED The luminous efficacy is around 30-35% (as of 2014) of electricity applied. The rest of electrical energy is transformed in a loss of power and must be dissipated. Padova Ottobre 2013 Titolo Intervento 17/N

18 Heat transfer from junction to environment Padova Ottobre 2013 Titolo Intervento 18/N

19 Heat sink calculation It starts from the temperature difference "desired" between junction (or better Tc) and ambient In the past Knowing the quantity of heat to be disposed per unit of time (Power in W) the maximum thermal resistance can be calculated N.B. This value must be reduced by thermal resistance Junction -Packaging and by Packaging-sink thermal resistance Padova Ottobre 2013 Titolo Intervento 19/N C

20 Heat Sink calculation In the past The heat sink must provide a thermal resistance less than the value found Padova Ottobre 2013 Titolo Intervento 20/N

21 Heat Sink calculation In the past Eventually it is possible to operate corrections by choosing the most appropriate size Padova Ottobre 2013 Titolo Intervento 21/N

22 Limits of traditional heat sinks Padova Ottobre 2013 Titolo Intervento 22/N

23 Heat pipes Heat sinks vs traditional heat sinks Traditional haet sinks: low thermal conductivity* Force of gravity *Inrespecttothe power Source Fischer Elektronik GmbH Padova Ottobre 2013 Titolo Intervento 23/N

24 Heat pipes heat sinks vs traditional heat sinks Traditional heat sinks: low thermal conductivity* The calculations shown were correct with uniform heat sources The problem becomes even more dramatic with the COB Areas with lower efficiency SourceFischer Elektronik GmbH Padova Ottobre 2013 Titolo Intervento 24/N

25 Heat pipes heat sinks vs traditional heat sinks Traditional heat sinks: low fin efficiency This feature limits the height of the fins Tfin = TAmbient Low fin efficiency Greater height does not become greater dissipation Heat Source Padova Ottobre 2013 Titolo Intervento 25/N

26 Heat pipes heat sinks vs traditional heat sinks Traditional heat sinks: to increase the dissipation It must be broaden the base of the heatsink But there is present the problem of thermal Areas with lower efficiency Padova Ottobre 2013 Titolo Intervento 26/N

27 Heat pipes heat sinks advantages Padova Ottobre 2013 Titolo Intervento 27/N

28 Heat pipes heat sinks vs traditional heat sinks Fin efficiency Heat pipes heat sink: high thermal conductivity Aluminum W/mK Aluminum extruded (60XX) W/mK + 22% Thermalconductivity N.B. Cast aluminum-50% Padova Ottobre 2013 Titolo Intervento 28/N

29 Heat pipes heat sinks vs traditional heat sinks Fin efficiency The Heat pipes heat sink solves the problem The fin temperature is much more uniform Padova Ottobre 2013 Titolo Intervento 29/N

30 Heat pipes heat sinks vs traditional heat sinks Heat sink weight With equal power dissipation halved the weight Aluminum g Aluminum extruded 1021 g -58% weight Padova Ottobre 2013 Titolo Intervento 30/N

31 Heat pipes heat sinks vs traditional heat sinks Heat Pipes Heat sink To increase power dissipation It grows in height with consistent basis Great for COB applications when the power grows No changes in the metal frame Padova Ottobre 2013 Titolo Intervento 31/N

32 Heat pipes heat sinks vs traditional heat sinks Heat Pipes Heat sink Permits the construction of special aesthetic value Design Padova Ottobre 2013 Titolo Intervento 32/N

33 Conclusions The increased thermal performance and such increase is highlighting the limits of traditional heat sinks. Thus become particularly interesting coolers that use the Heat Pipes thanks to the particularity of transmitting very efficiently the energy away from the LED This technology is particularly interesting for COB applications, characterized by high energy density (heat applied localized on small surfaces) Padova Ottobre 2013 Titolo Intervento 33/N

34 EASY FAMILY For powers up to 12 Watts, it is not valuable the use of Heat pipes The aluminum heat sinks are enough to dissipate such small powers Wepropose forsuchlevelofpower the Easy family Itisa Pure Aluminum1050 heatsink family high efficiency: Low weight High efficiency Modularity Easy tocustomizein covered applications Itisthe sametechnologyused on the SH7 product Padova Ottobre 2013 Titolo Intervento 34/N

35 EASY FAMILY Padova Ottobre 2013 Titolo Intervento 35/N

36 Grazie per l attenzione F.lli Poli Via dei Fabbri, 23 Breganze(VI) Padova Ottobre 2013 Titolo Intervento 36/N