Additional Sparger Tests in PPOOLEX with Reduced Number of Injection Holes
Markku Puustinen, Jani Laine, Antti Räsänen,
This report summarizes the results of the two sparger pipe tests (SPA-T1 and SPA-T7) carried out in the PPOOLEX test facility at LUT in 2015. Steam was blown through the vertical DN65 sparger type blowdown pipe to the condensation pool filled with sub-cooled water.
The main objective of the tests was to obtain additional data for the development of the Effective Momentum Source (EMS) and Effective Heat Source (EHS) models to be implemented in GOTHIC code by KTH. The test parameters were selected by KTH on the basis of pre-test simulations and analysis of the results of the earlier sparger tests in PPOOLEX. As opposed to the earlier tests only one row of injection holes at the sparger head (SPA-T1) or the holes of the load reduction ring (SPA-T7) were now used for steam injection. Both tests had two stratification periods and two mixing periods. In addition SPA T1 had an extra stratification period at the end of the test.
During the stratification periods the used steam injection flow rate was in the range of 30-45 g/s (75-112 kg/m2s). With these kind of mass fluxes steam flowed through the injection holes of the sparger as small jets and condensed mainly outside the sparger pipe. Because no chugging kind of phenomenon existed and the steam jets were too weak to create much turbulence in the pool, suitable conditions for thermal stratification to occur prevailed.
When the steam injection was vertically downwards from the LRR the transition region between the cold and warm pool water was deeper in the pool than in the horizontal injection case. The vertical length of the transition region was also longer in the LRR case.
Complete mixing was achieved with both tested flow modes, oscillatory cone jet mode (SPA-T1) and oscillatory bubble mode (SPA-T7). In the earlier tests with all the injection holes of the sparger head unblocked a considerably larger flow rate was not enough to mix the pool. Then the flow mode was different and not enough momentum and internal circulation were created for complete mixing to happen. Mixing was observed only above and a short distance below the sparger head outlet elevation.
condensation pool, steam blowdown, sparger, mixing