Critical heat-flux experiments under low-flow conditions in a vertical annulus
Abstract
An experimental study was performed on critical heat flux (CHF) at low flow conditions for low pressure steam water upward flow in an annulus. The test section was transparent, therefore, visual observations of dryout as well as various instrumentations were made. The data indicated that a premature CHF occurred due to flow regime transition from churn turbulent to annular flow. It is shown that the critical heat flux observed in the experiment is essentially similar to a flooding limited burnout and the critical heat flux can be well reproduced by a nondimensional correlation derived from the previously obtained criterion for flow regime transition. The observed CHF values are much smaller than the standard high quality CHF criteria at low flow, corresponding to the annular flow film dryout. This result is very significant, because the coolability of a heater surface at low flow rates can be drastically reduced by the occurrence of this mode of CHF.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- March 1982
- Bibcode:
- 1982STIN...8322563M
- Keywords:
-
- Annular Flow;
- Boiling;
- Convection;
- Flow Velocity;
- Heat Flux;
- Reactor Safety;
- Atmospheric Pressure;
- Stagnation Flow;
- Water;
- Fluid Mechanics and Heat Transfer