A STUDY OF ENHANCED DROPLET COOLING ACROSS GRID SPACER IN LOCA REFLOOD OF PWR BY LDA MEASUREMENT.

摘要

An experimental investigation of droplet-vapor mist flow across a test grid spacer was conducted. The study sought to simulate the grid spacer enhanced droplet cooling under reflooding conditions in the loss-of-coolant accident (LOCA) of a pressurized water reactor (PWR). The study also provides a fundamentally improved understanding of the basic mechanisms concerning droplet dynamics and droplet-vapor mist flow heat transfer.;The current investigation gives a discussion regarding droplet dynamics and heat transfer mechanism across grid spacer. The current study also provides a detailed discussion of the grid spacer's quenching behavior, the cooling downstream, and the droplet enhancement cooling, combined with the results of the full length rod bundle test. Empirical correlations are made for prediction of temperature distribution and heat transfer in the rod bundles during the refill and reflood phase of a LOCA.;An understanding of water droplet dynamics is necessary for explaining the sharp drop in cladding temperature which is observed immediately downstream of the grid spacer. A test channel which simulates the PWR reactor rod bundle was built to conduct both temperature measurements of the rod cladding and vapor flow, and droplet dynamics measurement before and after the grid spacer. The large droplets (