Cooling systems in machinery

TYPES OF COOLING SYSTEM:

1. Air Cooling System
2. Liquid Cooling System
3. Combine Air & Liquid Cooling System          

Air Cooling System:

             Air cooling is a method of dissipating heat. It works by making the object to be cooled have a larger surface area or have an increased flow of air over its surface, or both. An example of the former is to add fins to the surface of the object, either by making them integral or by attaching them tightly to the object's surface (to ensure efficient heat transfer).

             Instead of circulating fluid through the engine, the engine block is covered in aluminum fins that conduct the heat away from the cylinder. A powerful fan forces air over these fins, which cools the engine by transferring the heat to the air.

             Mostly it is done by using a fan blowing air into or onto the object one wants to cool. In many cases the addition of fins adds to the total surface area.

             In all cases, the air has to be cooler than the object or surface from which it is expected to remove heat. This is due to the second law of thermodynamics, which states that heat will move spontaneously from a hot reservoir (the heat sink) to a cold reservoir (the air).

Advantages

Ø  No need for radiator

Ø  No coolant

Ø  No water pump etc.

Ø  Less weight

Disadvantages

Ø  Noisy

Ø  Difficult to control temperature properly.

                       WATER COOLING SYSTEM:

Ø               Water cooling is a method of heat removal from engine components As opposed to air cooling, water is used as the heat conductor. Water cooling is commonly used for cooling automobile internal combustion engines and large industrial facilities such as steam electric power plants, hydroelectric generators, petroleum refineries and chemical plants.[

Ø                  The cooling system on liquid-cooled vehicles circulates a fluid through pipes and passageways in the engine. As this liquid passes through the hot engine it absorbs heat, cooling the engine. After the fluid leaves the engine, it passes through a heat exchanger, or radiator, which transfers the heat from the fluid to the air blowing through the exchanger 

COOLANT/ANTI-FREEZ:

               

Ø  Vehicles operate in a wide variety of temperatures, from well below freezing to well over 50 C. So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat.

               

Ø  Water is one of the most effective fluids for holding heat, but water freezes. The fluid that most vehicles use is a mixture of water and ethylene glycol (C₂H₆O₂), also known as antifreeze. By adding ethylene glycol to water, the boiling and freezing points are improved significantly.

               

Ø  The temperature of the coolant can sometimes reach 250 to 275 F (121 to 135 C). Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point.

Ø  Its distinctive odor also indicates cooling system leaks and problems that would go unnoticed in a water-only cooling system.

	Pure Water	50/50 C2H6O2/Water	70/30 C2H6O2/Water
Freezing Point	0 C	-37 C	-55 C
Boiling Point	100 C	106 C	113 C

COOLING MECHANISM:

Ø  Heat is conveyed from working parts to the RADIATOR hence to the air

Ø  Water/Coolant takes this heat from Cylinder and Combustion chamber by circulating in the water jacket

Ø  Water jacket is connected to the radiator by two hoses, one from the cylinder head to the radiator tank and the other base of the cylinder block to the base of the radiator

ØThe radiator consist of fine tubes called fins that increase the surface area

Ø  Water is confined in these tubes in thin films, which allow it to cool rapidly under the influence of an air flow