Insulated Expansion Tank (IET) and Thermal Storage for Engine Cold Start

During the cold start of an IC engine, the water temperature and particularly the oil sump temperature rises slowly depending on the outside ambient temperature. At the same time, the engine consumes more gasoline and emits more pollutants in the form of CO, HC, NO_X. The thermal comfort in the passenger compartment is also poor.

To avoid or minimize some of these problems, Valeo Engine Cooling is developing a new, economical system, the Insulated Expansion Tank (IET), which makes it possible to instantaneously heat the engine coolant by sensible heat from the IET, the volume of this tank has been increased especially for this application. The component actually has two functions:

1. 1.
   Allows for expansion and degassing of the cooling circuit
2. 2.
   Thermal storage of sensible heat

The IET is installed in the engine cooling circuit according to figure 1. Temperature and flow rate controls work according to the servo schematic depending on the coolant temperature inside the IET during an engine cold start.

The IET can transfer 150 to 200 Wh of thermal energy into the engine cooling circuit in a very short time; less than 30 seconds. However, the heat flux is equivalent to 18 to 24 kW.

Two types of servo controls have been studied:

ELECTRONIC CONTROLS - more efficient, but with higher costs. The components are: the electronic control unit, a (3) way electric solenoid valves and temperature sensors.

THERMOSTATIC CONTROLS - (mechanical) This solution requires only one 3 way thermostatic valve. The performance is similar to the electronic control, but the cost is less.

Valeo Engine Cooling has adopted the thermostatic control solution due to the very low cost, which can be up to 3 or 4 times less than the electric solution.