Method for estimating a thawed volume present in liquid form in a tank

A method for estimating a volume of thawed liquid contained in a motor vehicle tank, said tank comprising at least one heating element arranged inside the tank, wherein, after having started the vehicle and when the at least one heating means is activated, the following operations are executed at regular time intervals (ΔTi):

• Step A:
• using a thermometer arranged outside the tank, a temperature (θexti) of the ambient air outside the tank is obtained,
• Step B:
• as a function of said temperature (θexti) outside the tank and, using a first preestablished relationship (R1(θexti)), a heat-energy transfer (δES) between the contents of the tank and the external surroundings is determined,
• Step C:
• as a function of the power (W) produced by the at least one heating element, and using a second preestablished relationship (R2(W)), a heat-energy transfer (δEE) between the at least one heating element and the contents of the tank is determined,
• Step D:
• as a function of the energy transfers (δEi=δES+δEE) determined in steps B and C, and using a third preestablished relationship (R3(θEi)), a quantity (δVi) of liquid thawed or refrozen during this time interval (δTi) is determined,
• Step E:
• the quantities of liquid (δVi) thawed and refrozen during the preceding successive time intervals are summed in order to determine an estimated volume of thawed liquid present in the tank (VWC=ΣδVi).