Test: Engine Friction, Lubrication & Cooling - 1 - Mechanical Engineering MCQ

IC engines at best can transform about 25 - 35% of chemical energy into mechanical energy. About 35% of heat generated is lost to the cooling medium, remainder being dissipated through exhaust and lubricating oil.

Maximum temperature: At the center of piston crown.
Minimum temperature: At the bottom of oiston skirt.

A thermostat prevents the circulation of water below a certain temperature through the radiator so that the water gets heated, in modern engines, a wax-element type thermostat is normally employed.

The thermostat allows the water to go to the radiator only when the water has been raised to a pre-determined temperature of about 80 - 85° C. If the temperature of water is less, it is by passed to the pump.

It draws air through the spaces between the radiator tubes to bring down the water temperature appreciably.

It is used where plenty of water is available. The water from a storage tank is directly supplied through an inlet valve to the engine cooling water jacket. The hot water is not cooled for re-use but simply discharged. It is also known as nonreturn system.