Design tool KOLEKTOR

Mathematical model of solar flat-plate liquid collector has been transformed into design tool KOLEKTOR 2.2. The design tool is a computer program with user-friendly interface created in

Visual Basic Studio environment. Detailed geometrical and physical parameters of individual solar collector parts are entered through appropriate tool cards (general design parameters, absorber, glazing / insulation, calculation, see Fig. 3). Besides the principle parameters and characteristics the tool allows to enter also internal air pressure in the collector (for modelling both flat-plate atmospheric and evacuated collectors), slope of collector, type of heat transfer fluid (water, water — ethyleneglycol solution, water-propyleneglycol solution with defined mixing ratio) and to choose the separate free-standing installation or building envelope integration of collector (with given thermal resistance of envelope). Design tool allows to choose from various empirical models for calculating the heat transfer coefficients (e. g. forced convection in pipes, natural convection in air gap, sky radiation, wind convection) collected from different authors and thus to trace the influence of heat transfer coefficient model selection on the calculated performance of solar collector. There is often a number of possible models for calculation of heat transfer coefficients available but with rather different resulting values, e. g. wind convection models, and their influence on calculated collector performance should be verified (sensitivity analysis). Data entered into tool cards and choices made can be saved into text file (*.kol) for later use.

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Fig. 3. Tool cards of KOLEKTOR 2.2.

Output results of the design tool are the solar collector performance for given boundary conditions or efficiency curve of solar collector at standard boundary conditions (ta = 20 °C, G = 800 W/m2, w = 3 m/s) related to mean fluid temperature. Heat transfer coefficients in the individual parts of solar collector and nominal stagnation temperature tstg are displayed for detailed analysis. Results of calculation (collector efficiency curve) can be saved into spread-sheet file (*.res).