Thermal Stratification in a Pool with Submerged Heater Under Low Frequency Excitation

Thermal stratification has potential applications in the nuclear and solar industries. Thermal performance of passive residual heat removal systems and solar heaters is affected by the thermal stratification in a pool. Under the seismic condition, thermal stratification behavior of liquid in the pool has never been studied and reported in the literature. The present work focuses on the experimental investigation of thermal stratification in a pool under the seismic condition with the horizontally mounted heater simulating heat exchanger. Effect of heater submergence depth, frequency of excitation and amplitude of displacement on the thermal stratification has been studied. It was observed that the heater submergence depth significantly influences the thermal stratification in a pool. When a pool is subjected to an external excitation, the pool water separates into two zones; convective and impulsive. If the heater submergence depth in the impulsive zone, excitation effects are not found. If heater submergence depth is close to convective zone, significant effects are observed. However, it was observed that only first mode of excitation with large amplitude helps to achieve complete thermal mixing and higher modes of excitation have the minimal on the mitigating of thermal stratification. Non-dimensional stratification number has been evaluated to explain the mitigation of thermal stratification with seismic excitation.