Oil Tank wtih heater

Hello, I am a new Comsol user. I am trying to model an oil tank heated by a U heater.The heater use oil at a higher temperature. The cold oil in the tank is at 30°C and the hot is at 250°C.I use Non-isothermal Flow for the oil in the tank and non-isothermal pipe flow for the oil in the heater.Basically, I have used the model cold water glass (in the library) to model the oil in the tanker and the mold cooling model, the pipe part, ( in the library) to model the heater. Unfortunately, when I run the model, the temperature in the heater is constant (at the initial temperature of cold oil) after some seconds and the temperature in the tanker is even lower !!. It should be heated not cooled! So, the oil in the heater pass from 250 to 30°C and the oil in the tank from 30 to 28C, that is impossible at all! Where is the heat going ?

Help please !!
Thanks