Working Principle of Water-Cooled oil Cooler
The working principle of a Water-Cooled Oil Cooler is distinct from its air-cooled counterpart, though the ultimate goal—rejecting heat from the oil—remains the same.
The core principle is Heat Exchange through Conduction via a Liquid Medium (Coolant). Instead of using air, it uses the engine’s coolant to absorb heat from the oil.
Here is a detailed, step-by-step breakdown of its operation:
1. The Core Component: A Heat Exchanger
A water-cooled oil cooler is essentially a shell and tube heat exchanger or a plate-type heat exchanger.
- It consists of a metal housing (often aluminum or brass) that contains two separate, sealed passageways:
- A passage for engine oil.
- A passage for engine coolant.
- These two passages are in very close contact, separated only by thin metal walls that conduct heat easily, but they never mix.
2. The Path of the Hot Oil
Hot oil, after circulating through the engine and absorbing heat, is directed by the oil pump into the oil cooler. It enters through an inlet port and flows through its dedicated passageways (e.g., through a series of small tubes or between stacked plates).
3. The Path of the Cooler Coolant
Simultaneously, cooler engine coolant is circulated from the engine’s
cooling system into the adjacent passageways within the oil cooler (e.g., it
surrounds the tubes or flows in alternate channels between the plates). This
coolant is typically cooler than the hot oil because it has already been cooled
by the main radiator.
4. The Heat Transfer Process (Conduction)
This is the crucial step. The heat from the oil is transferred to the
coolant through conduction:
- The heat
energy from the hot oil moves through the thin metal walls separating the
two fluids. - The cooler
coolant on the other side of the wall absorbs this heat energy. - The large
surface area of the tubes or plates maximizes the area available for this
heat exchange to occur efficiently.
5. The Outlets: Cooled Oil and Warmed Coolant
- Oil Side: After giving up its excess heat, the oil exits the cooler at
a significantly reduced temperature and is returned to the engine to
resume its lubricating and cooling duties. - Coolant Side: The coolant, which has now absorbed the heat from the oil,
exits the oil cooler and flows back into the engine’s cooling system. It
eventually travels to the main radiator, where this combined heat load
(from the engine block and the oil) is finally rejected to the outside
air.