Presentation on theme: "Electronics Cooling MPE 635"— Presentation transcript:
1 Electronics Cooling MPE 635 Mechanical Power EngineeringDept.
2 Course Goals1. To establish fundamental understanding of heat transfer in electronic equipment.2. To select a suitable cooling processes for electronic components and systems.3. To increase the capabilities of post-graduate students in design and analysis of cooling of electronic packages.4. To analysis the thermal failure for electronic components and define the solution.
3 Part-AMain topicsIntroduction to electronics cooling and thermal packagingIntroduction to basic modes of heat transferConduction heat transfer and extended surfaces in electronic devicesTransient conductionNatural convection heat transfer (i.e. PCB cooling)Forced convection heat transfer (Internal and External flow )Fan performanceRadiation heat transfer and its applications in electronic devicesSolving the electronics cooling problems with EES softwareElectronics cooling problemsSolution of selected electronics cooling problems
4 1. Introduction to electronics cooling and thermal packages Thermal management importance in the electronic product developmentHeat sources in electronic products:-Power dissipated through electric resistancesP=I2R-Switching power dissipation in transistors
5 Case Study Every personal computer contains a CPU. The CPU clock and speed progress with time, the clock speed was increased from 200 MHz to 2 GHz from 1998 to due to this improvement, the CPU packages should also be improved to accommodate the increase in heat dissipation.You are required to study the various heat sinks and the required fan for thermal management for the Pentium® Processors from the MMX generation until the 4th generation.
6 Reliability and temperature Recent studies of electronic equipment have shown that the field reliability of equipment is temperature related.The failure rate model may be competitively described by the Arrhenius-type modelWhere the coefficients Ai, Bi, and Ei are independent of temperature.
7 Reliability and temperature Typical junction temperatures for equipment presently operating in a large number of field applications.
8 Liquid Cooling System Consideration System Types-direct cooling systemThe coolant flows over the component to remove heat from the surface and as such must be capable of sustaining a voltage gradientEfficient means of heat removal because the coolant is closest to the heat source.In addition, moisture absorption can lead to a chemical breakdown in some coolants, which in turn lowers the flash point, hence creating a potential safety hazard.
9 Liquid Cooling System Consideration System Types-Direct cooling system (cont.)Restrictions- Necessity for the maintenance of coolant purity- The system must be absolutely airtight in order to prevent air or moisture from degrading the heat transfer performance of the coolant.- Extreme care is thus required in selecting a dielectric for direct cooling applications.
10 Liquid Cooling System Consideration System Types-Direct cooling system (cont.)Common Examples of Direct Liquid CoolingApplicationCoolantCray-2 supercomputerFC.77Laser target illumination for electro-optical systemsFC-104, EGW, deionized waterRadar transmitter and TWTs on F-15 and F-16 fighter aircraft and othersC25RAntenna and klystron tubes for E3-AWACS radar systemFC-77, EGWTWTs on F-16 and ATF radarsC25R, PAO
11 Liquid Cooling System Consideration System Types-Indirect cooling system (cold-plate cooling)No requirement on the voltage drop.Suitable for commercial applicationsMay be used in antenna array modules having solid-state circuitry and in high-heat flux power supply modules in aircraft applications.
12 Liquid Cooling System Consideration Coolant Selection Parameters- FOM (Figure of Merit)- Toxicity- Maximum wet wall temperature- Flammability- Cost- Material compatibility- Corrosion- Pressure drop characteristics- Water absorption sensitivity
13 Liquid Cooling System Consideration Pressure drop and pump requirements- For the viscous pressure drop through the heat exchanger core, neglecting the entrance and exit losses,the velocity head term () is replaced by (), where G is the mass flow per unit area, kg/m2.s, a more commonly used heat exchanger parameter.
14 Liquid Cooling System Consideration Pressure drop and pump requirementsthe velocity head term () is replaced by (), where G is the mass flow per unit area, kg/m2.s, a more commonly used heat exchanger parameter.
15 AIR COOLING SYSTEM Induced or Draft Cooling Forced Cooling For small heat dissipation applications, the prime mover of the air cooling system may be the draft or circulation created by density variations.Forced CoolingThe prime movers are fans or blowers . For The general classification of blowers is best defined in terms of specific speed. Specific speed, Ns, is expressed by the equationWhere:Q (in ft3/min) and the pressure Δp (in inches of water)
16 AIR COOLING SYSTEM Fans and Blowers Range of specific speeds for various Fans and blowersFan and blower impeller designs