Design and Simulation of Air-Solar Preheating Unit: An Improved Design of a Flat Plate Solar Collector

The design of a flat-plate solar collector (FPSC) is accomplished by multiple input multiple output (MIMO) design technique. The design variables (absorber, fluid and glass temperatures; length, width, height of the FPSC) were the unknown variables in the commensurate thermal balance equations based on; component, overall and yardstick thermal balance on the FPSC. Then, simulator matrices were setup comprising of coefficient and column matrices of design functions. The elements of the coefficient matrix were the partial derivatives of the design functions with respect to the design variables. Besides the convective and radiative heat transfer coefficients were function of the design variables. The initial values of the design variables (307K, 334.5K, 368K, 2 m, 1 m, and 0.045m, respectively) were set, at the seventh iteration, the output variables (306.9K, 339.15K, 368.1K, 2.01m, 1.005m, 0.04m, respectively) merged as the design functions → 0 with insignificant change in the design variables. The output results were used to simulate FPSC, to track its responses to changes in the physical conditions, the stimulation revealed some constraints in the design of the FPSC, which is vital information for the overall optimization of the FPSC. The design yardsticks; the thermal efficiency (0.76) and the effectiveness (0.4) are quite pragmatic. This shows that MIMO technique to thermal system design is effective as convergence among the design variables was sought. Moreover, MIMO considered all thermal losses instead of basing the yardsticks on top loss overall transfer coefficient alone; thus, neglecting sidewalls and base losses. Moreover, the advent of connecting box prepares the preheating unit for high temperature drying (> 150 oC) on integration with a reheating unit.