The liquid cooling should take up the engine heat through the coolant, and release it, through the radiator, (1) into the open. The engine temperature should
ideally be very constant. The
heating of the vehicle interior is achieved through the heat exchanger (7).
How it works
The circulation pump cooling helps to avoid component-critical temperatures in all parts of the engine. Also the cylinders which are not in the vicinity of the pump, are cooled to the same extent. The temperature of the
coolant increases, from its entry into the cylinder block, until it reaches the cylinder head.
Whereby, the water jackets of the cylinders only exist in the
upper half, sometimes even, with a continuously upwards increasing cross section. The distribution is also controlled through the openings in the head gasket. The avoidance of both hot spots and of vapour-lock is
important. A pump (6) transports coolant, in a process regulated by the thermostat (5), from heat sensitive points in the engine to
the radiator (1). One or two
fans (4), controlled a by thermo switch (3) provide, when required, for additional heat exchange. This process is only fully initiated when the engine is too hot and / or there is insufficient air flow, to avoid unnecessary
energy losses and to maintain the operating temperature (as high as possible) of the internal combustion engine. Beforehand, the coolant circulates through the short circuit cycle (8). Diesel engines often need a
supplementary heating (9).The liquid cooling system is operated at up to approx. 1 bar over-pressure (testing pressure max. 1.5 bar) to allow an operating temperature of the coolant of more than 100°C. This
pressure is mostly controlled through two valves in the lid of the reservoir tank (2, figure 3 for trucks). If it rises too sharply, for the protection, e.g., of the radiator, it is bled off as air (pressure release valve). If there is a
danger of too low pressure through cooling, outside air is sucked in (check valve). Together, both mostly form a double-strike valve.
This kind of cooling has a steadying effect on the cylinder block and provides, except in modern diesel engines, for effective heating in the interior.
Apart from the electronification of the cooling system, there is one more possibility for higher efficiency and less weight, the vaporisation cooling. The heat
transmission is optimised
using substantially less coolant through the two-fold changing of the aggregate state. The air-conditioning already functions on this principle, however, for
the higher temperature level
of the engine cooling and the special mixture of the coolant, this conversion is difficult. The operational safety must be maintained at all costs. 06/09