EXTENDED MODEL EQUATION FOR UNCOVERED COLLECTORS

摘要

A test system with 50 m² uncovered collector was installed and operated connected to a district heating net in Bishkek (Kyrgyzstan). The useful power gain as well as the weather conditions were measured for two months with a high time resolution. The collector was driven with water inlet temperatures far below the ambient temperature level. For the description of the energy balance of the collector an extension of the customary model equations was necessary. The extended model equation consider different heat transfer mechanisms and coefficients which are effective on different and varying sections of the absorber at the same time and includes e.g. convective and condensation heat transfer. The results of the model are compared with measured data. If the boundary conditions, especially the time series of weather, are known, with the model proper long term predictions can be carried out regarding the expected collector gain even for unusual conditions as described above.