Heating of the pipeline with thermally insulated outer surface was modelled using the explicit finite difference method. The time variation of the fluid temperature at the pipeline inlet has the ramp form. An exact analytical solution was found using the method of superposition. The differences between the analytically and numerically predicted fluid and tube wall temperatures are small. The same method will be used in future for modeling, a heat storage unit, that is used in a combined electric-water heating system.

Heating of the pipeline with thermally insulated outer surface was modelled using the explicit finite difference method. The time variation of the fluid temperature at the pipeline inlet has the ramp form. An exact analytical solution was found using the method of superposition. The differences between the analytically and numerically predicted fluid and tube wall temperatures are small. The same method will be used in future for modeling, a heat storage unit, that is used in a combined electric-water heating system.