CH-85-02-3 -- A Simple Boiler Model PDF

The oil-fired boiler is considered as a component of a heating system. Heat production efficiency and temperature variation of the boiler water are the most interesting boiler characteristics. The computational time of the model must be short in order to make full-system simulations possible.

In order to meet these requirements, a simple model with no iterative processes has been developed. The flue gas and ventilation losses from the boilers are computed, assuming first order transients approaching constant gas and air temperature, respectively, when the burner starts and stops.

Corrections are made for flue transients and are also possible for flue changes due to, e.g., wind pressure and to chimney temperature dependence on burner operation intermittency. The environmental heat losses to the plant room are divided into two parts, one dependent on mean boiler water temperature and one on burner operation.

The heat content of the boiler is calculated by means of a resulting heat capacity for the boiler and its water. This means that the total heat content is represented by only one temperature. This is taken as the control temperature of the water. Comparisons with other programs indicate that the model issatisfactory.