HEAT SINKS* Heat sinks are needed when the heat transfer to theambient air directly from the top of the device is not sufficientto keep the semiconductor device within the allowabletemperature range.* heat sink was supplanted in higher power applications .* increasing the thermal conductance of components and increasing the fin area exposed to the airflow is very important.
THERMAL INTERFACE MATERIALS• TIM is essential when two or more solid surfaces are in the heat path.• The air gaps created by multiple voids of "contacting" hard surfaces are simply too large a thermal barrier for even modest power applications.• The first tactic in overcoming this barrier is to fill the voids and eliminate air by introducing a third material to the heat path that is fluidic and wets the surfaces.
Cont.• An important property of any TIM is its thermal conductivity.• grease and Elastomeric pads are used as TIM.
COOLING FANS AND BLOWERS • Cooling fans and blowers are essential to systems that produce a significant amount of heat like computers and other electronic components. • Different systems are engineered to work with specific types of fans. • Cooling fans come in all shapes and sizes. as well as voltage, airflow, and case size.
Difference Between Fans and BlowersAxial fans:• Create an air flow that is parallel to the axis of the fan blade.• designed to work with systems that have low back air pressure and high rate air flow.• less noise.• Quite common and the most economical cooling solution.• they are normally used in computers.
CONT.Blowers :• Send air on a perpendicular direction in relation to its axis.• Designed to work with systems that have high impedance (i.e. high back pressure) and low rate air flow.• It produce a more concentrated airflow in a system, So they tend to generate a significant amount of noise.• they are used in Servers.
AC AND DC COOLING FANS property DC FANs AC Fans voltages 5V, 12V, or 24V 110v , 220v frequency 0 50 Hz , 60 Hz Air Flow speed Variable ConstantPower consuming Low ( 60 percent less) highElectro Magnetic and Lower level Higher levelRadio Frequency Interference Life longer shorter
CONT.• The difference in the cost between AC fan and DC fan is negligible.• When choosing fan for your applications, it is important to look at the cooling requirements of the system and applications, the fan type, the air flow, and AC or DC power operation.• AC fans are used when DC voltage is not available.• All types of computer equipment rely on DC cooling fans.
What is liquid cooling ? • Liquid (Water)cooling is a method of heat removal from electrical components . As opposed to air cooling, water is used as the heat conductor.
History • Cooling hot computer components with various fluids has been in use since at least as far back as the development of Cray-2 in 1982. • Through the 1990s, water cooling for home PCs slowly gained. • it started to become noticeably more prevalent after the introduction of AMDs hot-running Athlon processor in mid 2000
Cont. • As of 2011, there are several manufacturers of water cooling components and kits, and some custom computer retailers include various setups of water cooling for their high performance systems. • Apples Power Mac G5 was the first mainstream desktop computer to have water cooling as standard. • Dell followed suit by shipping their XPS computers with liquid cooling.
cont.Radiators have different FPI (fins per inch) and therefor optimized for different typeof fans, the ones with high FPI are optimal with powerful fans where ones with lowFPI are better for lower RPM fans.
Advantagesof liquid cooling over air cooling • waters higher specific heat capacity, density, and thermal conductivity. This allows water to transmit heat over greater distances with much less volumetric flow and reduced temperature difference. • Drawing heat away from the processor and outside of the system. This allows for higher clock speeds in the processor as the ambient temperatures of the CPU core are still within the manufacturers specifications.
Advantagescont. • The water jacket around an engine is also very effective at deadening mechanical noises, which makes the engine quieter, Many high performance CPUs require fan speeds in excess of 7000 rpm that generate noise of 60+ decibels of noise. • No DUST and no need to open computer to clean it.
Disadvantages. • Costs significantly more than an air-cooled engine system, approx. 600$. • Size and weight ,need large area inside and out side the computer require larger desktop system cases to fit all of these parts within the computer case itself ,approx.6.5Kg. • and technical skills required to install a kit , suitable tubes length , leaks could cause severe damage to the components inside of the system.
cont. • Leaking . • Condensation, due to the ambient air right around the pelt being cold. • Water freezes at 0℃.
Usage • Water cooling can be used to cool many computer components. • especially the CPU. • GPU. • Northbridges. • Southbridges. • Hard disk drives. • Memory. • Voltage regulator modules (VRMs). • Power supplies can be water-cooled.
Coolant. • This coolant contains a high quality anti-corrosion agent for various materials including copper, aluminum, and plastic, that prevents corrosion for long term operation. • Material : Propylene Glycol & Anti-Corrosion Agent. • Freezing Point : -9℃. • Exchange Cycle : 1 year.
Liquid vs. Air cooling Liquid Air Cost high low size big small compatibility Specific CPU All CPU safety less more Skill required yes no efficiency high moderate spread low high