06-03-2013, 11:50 AM
DESIGN AND THERMAL ANALYSIS OF COOLING FINS
DESIGN AND THERMAL.docx (Size: 1.92 MB / Downloads: 232)
ABSTRACT
Most internal combustion engines are fluid cooled using either air (a gaseous fluid) or a liquid coolant run through a heat exchanger (radiator) cooled by air. In air cooling system, heat is carried away by the air flowing over and around the cylinder. Here fins are cast on the cylinder head and cylinder barrel which provide additional conductive and radiating surface. In water-cooling system of cooling engines, the cylinder walls and heads are provided with jacket cooling fins help keep Chevrolet volt battery at ideal temperature .We know that in case of Internal Combustion engines, combustion of air and fuel takes place inside the engine cylinder and hot gases are generated.
The temperature of gases will be around 2300-2500°C. This is a very high temperature and may result into burning of oil film between the moving parts and may result into seizing or welding of the same. So, this temperature must be reduced to about 150-200°C at which the engine will work most efficiently. It is to be noted that the engine is quite inefficient when it is cold and hence the cooling system is designed in such a way that it prevents cooling when the engine is warming up and till it attains to maximum efficient operating temperature, then it starts cooling. The modeling is done using Pro E, and analysis is done using Ansys. The overhangs of the cooling fins are calculated for the thermal and deflections analytically are compared with the results obtained with the analysis software.
INTRODUCTION
COOLING SYSTEMS OF INTERNAL COMBUSTION ENGINES
IN the past decades, heat dissipation of electronic element grows rapidly with the improvement of manufacturing technology. This growth induces serious electronic cooling problem. Air-cooling module, which composed of a heat sink and a fan, is popular for solving the heat dissipation problem. In order to satisfy the heat dissipation of modern electronic element, thermal designers have to increase fin area and fan speed to improve its cooling capacity. However, the increase of fin area is restricted by the space. Besides, the increase of fan speed would induce noise, which damages human health. Air-cooling module, therefore, is hardly to meet the requirement of modern electronic component.Recently, thermoelectric cooler (TEC) is applied to electronic cooling. With the advantages of small size, quietness and reliability, thermoelectric cooler is widely applied to military, aerospace, instrument, and industrial products for different cooling purpose [5]. A typical thermoelectric cooler consists of p-type and n-type semiconductor pellets connected electrically in series and sandwiched between two ceramic substrates. Whenever direct current passes through the circuit of heterogeneous conductors, it causes temperature differential between TEC sides. As a result, one TEC face, which is called cold side, will be cooled while its opposite face, which is called hot side, is simultaneously heated. With the above advantages, TEC might be one of the best candidates for electronic cooling and a lot of studies try to determine its utility on electronic cooling .
AIR COOLED SYSTEM
Air cooled system is generally used in small engines say up to 15-20 kW and in aero plane engines. In this system fins or extended surfaces are provided on the cylinder walls, cylinder head, etc. Heat generated due to combustion in the engine cylinder will be conducted to the fins and when the air flows over the fins, heat will be dissipated to air. The amount of heat dissipated to air depends upon :
• Amount of air flowing through the fins.
• Fin surface area.
• Thermal conductivity of metal used for fins.
ADVANTAGES OF AIR COOLED SYSTEM :
Following are the advantages of air cooled system :
• Radiator/pump is absent hence the system is light.
• In case of water cooling system there are leakages, but in this case there are no leakages.
• Coolant and antifreeze solutions are not required.
• This system can be used in cold climates, where if water is used it may freeze.
DISADVANTAGES OF AIR COOLED SYSTEM:
• Comparatively it is less efficient.
• It is used in aero planes and motorcycle engines where the engines are exposed to air directly.
Water-cooling
Water-cooling is the practice of using water to help cool your components. In essence water-cooling works similarly to heat pipe technology in that the role of water is taking heat out of your blocks and dumping it into the ambient. Water-cooling, when compared to air cooling is much more modular in it's execution. Analogically, compared to an air cooler it would be as if you got to buy the heat pipes, the fin assembly, the contact plate and the fans all separately and then made your own cooler. Water-cooling is usually chosen, when the chosen by reasonably informed people, for three reasons. Firstly is looks, since you can choose the finish on your blocks and fittings, color of tubing and coolant etc. Second would be silence. Using water-cooling one can cool their computer much quieter than most air solutions. Some air coolers nowadays are very quiet, such as the well know Noctua NH-D14, however with water-cooling you can extend that to other components such as your Graphics Cards and motherboard components etc.. Alternatively, given a high noise tolerance, water-cooling can net you MUCH greater performance. And given the modular nature of water-cooling users can choose where about sin that spectrum they sit.
RESTRICTION
Usually refers to how a particular component (usually a block or a rad) impairs the flow of water in your system. Typically, CPU blocks are the most restrictive component in a loop. GPU only blocks have a similar construction and usually are also very restrictive. Other blocks, such as full cover VGA blocks and motherboard blocks tend to be much less restrictive and the restriction of most radiators is usually pretty much negligible when compared to your blocks. Restriction might also refer to the AIR restriction in a rad, though this is less common.
MONO-METAL EXTRUDED FIN
Extruded or Integral Fins are created by sending thick-walled tubes through a press which extrudes the fin from the tube in a cold worked process. The cold working process hardens the fins making them well suited to cleaning. There is no bi-metal joint exposed to the gas side eliminating galvanic corrosion. The Mono-metal fin is best suited for low pressure applications.
FUNCTION OF FINS:
In electronic systems, a heat sink is a passive component that cools a device by dissipating heat into the surrounding air. Heat sinks are used to cool electronic components such as high-power semiconductor devices, and optoelectronic devices such as higher-power lasers and light emitting diodes (LEDs). Heat sinks are heat exchangers such as those used in refrigeration and air conditioning systems, or the radiator in an automobile. A heat sink is designed to increase the surface area in contact with the cooling fluid surrounding it, such as the air. Approach air velocity, choice of material, fin (or other protrusion) design and surface treatment are some of the factors which affect the thermal performance of a heat sink. Heat sinks are used to cool computer central processing units or graphics processors. Heat sink attachment methods and thermal interface materials also affect the eventual die temperature of the integrated circuit. Thermal adhesive or thermal grease fills the air gap between the heat sink and device to improve its thermal performance. Theoretical, experimental and numerical methods can be used to determine a heat sink's thermal performance.
WORKING OF FINS:
A cooling fin acts like a passive cooling device as it works by pulling excessive heat from the main source producing the heat and in place it increases cooling to that surface area. Cooling fins work in two ways. They direct heat evenly away from metal or some other object like your processor chip. Second they allow air to cool the coils, metal or chip just as evenly. If a fan simple blew air onto a radiator coil the air would not be evenly spread to all areas. Cooling fins allow the air to jit all areas of the coils which is why we must never bend fins. If we do we need to fix them as quickly as possible since this leads to overheating.
INPROCESSOR/MICROPROCESSOR COOLING:
Heat dissipation is an unavoidable by-product of all but micro power electronic devices and circuits. In general, the temperature of the device or component will depend on the thermal resistance from the component to the environment, and the heat dissipated by the component. To ensure that the component temperature does not overheat, a thermal engineer seeks to find an efficient heat transfer path from the device to the environment. The heat transfer path may be from the component to a printed circuit board (PCB), to a heat sink, to air flow provided by a fan, but in all instances, eventually to the environment.