OPTIMISATION OF MANTLE TANKS FOR LOW FLOW SOLAR HEATING SYSTEMS

A model, describing the heat transfer coefficients in the mantle of a mantle tank has been developed. The model is validated by means of measurements with varying operational conditions for different designed mantle tanks. The model has been implemented in an existing detailed mathematical programme that simulates the thermal behaviour of low flow SDHW systems.

The yearly thermal performance of low flow SDHW systems with different designed mantle tanks has been calculated. The influence of the mantle tank design on the thermal performance is investigated by means of the calculations with the programme and by means of tests of three SDHW systems with different designed mantle tanks.

Based on the investigations design rules for mantle tanks are proposed. The model, describing the heat transfer coefficients in the mantle is approximate. In addition, the measurements have revealed that a temperature stratification in the hot water tank, above the mantle is built up. This phenomenon may be important, but it is not taken into calculation in the programme.

Therefore, theoretical and practical work is continuing in order to make a more precise model for the whole mantle tank.