Abstract
The NHR-200 reactor in China adopts the noncondensable gas self-stabilizing control and the noncondensable gas used for pressure stabilization control can weaken steam condensation heat transfer in the integrated steam-gas pressurizer. A condensation experimental system was established and the heat transfer characteristics of steam-nitrogen and steam-argon condensation under natural convection had been investigated. The pressure ranged from 0.516 to 5.10 MPa. The distributions of nitrogen and argon in the steam/gas mixture were obtained in the experiments, and the results showed that nitrogen and argon were evenly distributed in the steam under different pressure, respectively. The effects of heat transfer temperature difference had also been investigated and it is found that the total heat transfer coefficient difference had little influence on the total condensation heat transfer coefficient. However, the steam condensation heat transfer coefficient decreased with the increase of the degree of supercooling of the wall. The condensation heat transfer coefficient was reduced by approximately 0.11 kW/(m2·K) as the degree of supercooling of the wall changed from 14°C to 36°C. The condensation heat transfer coefficient also decreased with the mass/molar fraction of noncondensable gas increasing and a certain difference between the effect of the mass fraction of noncondensable gas and the effect of the molar fraction of noncondensable gas was discussed in this paper.
Highlights
Small- and medium-sized reactors have become one of the options for future power propulsion due to their high safety and reliability, low power density, short construction period, and so forth. e integrated reactor is one of the main types of small- and medium-sized reactors, such as VVER-300 and VK-300 reactors in Russia, SMART reactor in South Korea, SMR reactors in the United States, and NHR-200 reactor in China [1,2,3].e NHR-200 reactor adopts the noncondensable gas self-stabilizing control, that is, the integrated steam-gas pressurizer is adopted and the noncondensable gas is used for the pressure stabilization control [4]
The pressure in the reported condensation experiments under natural convection is confined within 2.0 MPa. erefore, the investigations on heat transfer characteristics of steam condensation in presence of noncondensable gas under natural convection are conducted and an experimental system is established in this paper. e effects of nitrogen and argon on the steam condensation have been investigated and the pressure ranges from 0.516 to 5.10 MPa
When the primary pressure varied from 0.517 to 5.10 MPa and the gas temperature varied from 110°C to 249°C, the differences in the mass fraction of nitrogen/argon in the axial direction were less than 2.7% and had similar trends when the axial distance increased
Summary
Small- and medium-sized reactors (generally less than 300 MWe) have become one of the options for future power propulsion due to their high safety and reliability, low power density, short construction period, and so forth. e integrated reactor is one of the main types of small- and medium-sized reactors, such as VVER-300 and VK-300 reactors in Russia, SMART reactor in South Korea, SMR reactors in the United States, and NHR-200 reactor in China [1,2,3]. E effects of nitrogen and argon on the steam condensation have been investigated and the pressure ranges from 0.516 to 5.10 MPa. For the experimental studies, the pressure in the reported condensation experiments under natural convection is confined within 2.0 MPa. erefore, the investigations on heat transfer characteristics of steam condensation in presence of noncondensable gas under natural convection are conducted and an experimental system is established in this paper. E effects of nitrogen and argon on the steam condensation have been investigated and the pressure ranges from 0.516 to 5.10 MPa Some factors, such as the distribution of noncondensable gas in the steam, heat transfer temperature difference, the mass fraction, and molar fraction of noncondensable gas, have been studied in the experiments under high pressure in this paper
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