Prediction of Velocity and Temperature Profiles in Thermally Driven Gravity Currents Applied to Stratified Thermal Storage Tanks

摘要

It has been demonstrated that one way of producing thin thermoclines in a chilled water thermal storage tank is by introducing the fluid in the form of a gravity current. Early in the flow the gravity current is controlled mainly by inertia and buoyancy forces, producing what is called the inertia-buoyancy (I-B) regime. Subsequently, the viscous force dominates inertia, and the flow is governed by viscous and buoyancy forces, resulting in the viscous-buoyancy (V-B) regime. In the work to be reported, vertical profiles of velocity and temperature in two-dimensional, thermally driven, constant inflow gravity currents were studied. This was done to provide a basis for understanding the initial stages of the formation of a thermocline. The gravity current was modelled with three regions, the head, the main body and the mixed region. In this analysis, the head was ignored and a laminar flow model was used to predict velocity and temperature profiles in the main body near the floor and in the mixed region above the main body and behind the head. Analytical and numerical models were developed for both regimes. Major features of the I-B regime temperature above the floor to an elevation roughly equal to the top of the inlet diffuser opening and a high gradient region above the top of the inlet opening. Velocity profiles in the I-B regime velocity profiles and also higher gradients above the top of the inlet opening than those in the V-B regime. 6 refs., 8 figs. (ERA citation 13:036465)