Abstract
Passive containment cooling system (PCCS) is an important passive safety facility in the large advanced pressurized water reactor. Using the physical laws, such as gravity and buoyancy, the water film/air countercurrent flow is formed in the external annular channel to keep inside temperature and pressure below the maximum design values. Due to the large curvature radius of the annular channel, one of the short arc segments is taken out, as a rectangular channel, to analyze the main water film evaporation heat transfer characteristics. Two numerical methods are used to predict the water film evaporative mass flow rate during the heat transfer process in the large-scale rectangular channel with asymmetric heating when the water film temperature is not saturated. At the same time, these numerical simulation results are validated by the experiment which is set up to study water film/air countercurrent flow heat transfer on a vertical back heating plate with 5 m in length and 1.2 m in width. It is shown that the maximum deviation between numerical simulation and experiment is 30%. In addition, the influences on these parameters, such as heat flux, evaporative mass flow rate, and water film thickness, are evaluated under the different tilted angles of the rectangular channel and horizontal plane, water/air inlet flow rates, water/air inlet temperatures, heating surface temperatures, and air inlet relative humidities. All these results can provide a good guidance for the design of PCCS in the future.
Highlights
In recent years, more and more passive safety facilities have been applied in the large advanced pressurized water reactor
The passive containment cooling system (PCCS) is used in AP600 [1], AP1000 [2], and CAP1400 [3], mainly to remove the decay heat from the postulated accident scenario and prevent the release of the radioactive materials. e main characteristic of PCCS is that the gravity-driven water film flows downward along the outer surface of containment wall with the countercurrent buoyancy-driven air flowing above the water film in the annular channel. e water film evenly covering the heated shell wall cools down the containment together with naturally circulating air, and the water film evaporation will dominate the heat transfer process [4]
Because PCCS does not rely on electric power or active mechanics and the number of equipment simplified, it is adopted in the larger advanced power reactor
Summary
More and more passive safety facilities have been applied in the large advanced pressurized water reactor. E bottom surface temperature of the channel was changed by adjusting the input electric power of the conducting oil heater Based on their experimental results, they fitted an evaporation mass transfer relationship that mainly considered the influence of the channel gap height on mass transfer. Ere had been a lot of analysis codes that used to analyze the heat removal capacity of PCCS, such as MELCOR [11], COCOSYS [12], WGOTHIC [13], MAAP4 [14], COMMIX [15], and CAST3M [16] These current codes were lack of the experiment validation and did not consider the gradient distribution of parameters in the direction of the channel gap height, so their application was limited.
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