This thesis examines the transient performance of packed bed heat regenerators when very large temperature differences are involved. The effects of gas temperature on the key gas physical properties of velocity, density and heat capacity were studied via simulation. Three models were developed and compared. The first model (HRKDV) considers heat balances for both solid and gas phases, the second (HRVDV) considers mass balances in addition to the heat balances set up in the first model and the third one (HRASO) considers that the only significant rate of accumulation term is that of the energy of the solid phase. The governing partial differential equations were solved by the method of lines with the spatial discretization accomplished by the method of orthogonal collocation. The findings of this work reveal that whereas the effects of large temperature changes on the gas velocity and density are completely negligible, the effects of temperature on the gas heat capacity must be considered "continuously" when large temperature swings occur. Considering the heat capacity as a constant, even at an average value, leads to significant errors in temperature profiles. / Graduation date: 1992

This thesis examines the transient response of a packed bed heat regenerator when heated from an initial uniform bed temperature. Very large (1700 K) temperature differences were studied as well as the effect of simultaneous chemical reaction in the gas phase. First the effects of temperature on physical and transport properties were studied in detail in the absence of a reaction. Models with compressible flow were compared with conventional models with constant properties and incompressible flow. Several measures of the regenerator's response to a step change in inlet gas temperature were calculated to characterize the spread of the temperature front. Variances of the spatial derivative of the gas temperature profile and the time derivative of the product gas temperature were used to evaluate thermal efficiency. The effects of an exothermic homogeneous gas phase reaction in the regenerator process were also studied. Several simple kinetic schemes and inlet conditions were simulated and the profiles of reaction rate and conversion as well as temperature were analyzed. / Graduation date: 1993