Computer Simulation of Solar Air Heating Systems Using Rock Bed Thermal Storage Units

摘要

This thesis is concerned with the analysis and design of solar air heating systems utilizing rock beds as thermal storage units. A computer simulation model capable of estimating the response of both the solar collector and the rock bed is described. Differential equations describing the rock bed were approximated in a finite-difference form and solved numerically on a digital computer. The temperature of both the solid (rock) and the fluid (air) is determined as a function of time and distance along the bed. The simulation required both charging and discharging of the rock bed for time-varying inlet fluid temperatures. The numerical method used to solve the rock bed equations proved to be stable and convergent and showed satisfactory agreement in comparison to an analytical solution for constant-inlet air temperature. A cost analysis was also incorporated within this program; by varying the collector area one could determine the optimum collector size for maximum savings. Pressure drop relationships for flat-plate collectors, duct work and packed beds were used to determine operating costs. The particular air system tested proved to be cost effective when compared with natural gas fuel costs for an economic term of 20 years. (Author)