[en] Helical pipes have been extensively adopted in industries and engineering, especially in nuclear power plants as steam generators. Compared with straight ones, helical pipes gain the advantage of improved heat transfer efficiency but face the challenge of adverse pressure resistance. In this paper we utilized the innovative Lattice Boltzmann Method to investigate the flow characteristics in helical pipes. The results proved in good accordance with previous experiments and could provide assistance for the design and optimization of helical pipes. (author)

[en] The 10 MW High Temperature Reactor Test Module (HTR-10) is being constructed now and planned to be operational in 2000. One of the objectives is to develop the high temperature process heat application. The methane steam reformer is one of the key-facilities for the nuclear process heat application system. The paper describes the conceptual design of the HTR-10 Steam Reformer with He heating, and the design optimization computer code. It can be used to perform sensitivity analysis for parameters, and to improve the design. Principal parameters and construction features of the HTR-10 reformer heated by He are introduced. (author)

[en] The technology of nuclear energy seawater desalination was discussed in the paper. The different interfaces of nuclear power applied in desalination technology were also analyzed. Because of good performance, low energy wastage and other reasons, the horizontal tube and low temperature MED (LT-MED) technology is very coupling with nuclear heating reactor (NHR). Then, the principle and application of LT-MED technology were introduced. In the end, a physical-mathematical LT-MED model was developed to explore the thermal hydraulic performance. Two temperature difference distribution schemes, equal temperature difference and equal heat transfer area temperature difference, were analyzed for the system design. (authors)

[en] Full text of publication follows: Natural circulation is widely used in dynamic engineering and chemical engineering. If the natural circulation system itself moves, such as heaving or rolling, the movement will affect the fluid flow inside the system and at the same time change the pressure distributing in the system. The above effect may result in single-phase flow into two-phase flow and excite the density-wave oscillation in the system. Density-wave oscillation will cause mechanical surge in the system and mangle the equipment. Up to now, great deals of researches have been done on mass flow rate and density-wave oscillation in immovable natural circulation system. But with regard to the heaving or rolling natural circulation system, researches are mainly focused on the static problems, such as flow rate wave, temperature field change or critical heat flux etc. No researches on two-phase flow density-wave oscillation in a heaving or rolling circulation system have been reported in public papers. Base on analysis model developed for immovable natural circulation system, with regard to the heaving, rolling or pitching of a classic natural circulation system, an analysis model has been established which can analyze the change of mass flow rate and density-wave oscillation boundary in the immovable and moving system. Inertia force item is added to the fundamental system conservation equations in order to include the effect of heaving, rolling or pitching. The inertia force of heaving, rolling or pitching is analyzed first. The frequency domain linear stability analysis method is used to analyze the two-phase flow stability boundary. The calculation results show that the excursion of density-wave oscillation boundary will occur when the system is heaving, rolling or pitching, and the parameters of heaving, rolling or pitching will affect the boundary excursion. Compared with immovable natural circulation system, the following results can be obtained: if the heating power is constant the density-wave oscillation boundary will move toward smaller inlet subcooling region because of heaving and rolling when mass flow rate is greater than the flow rate value in immovable system. On the other hand, the density-wave oscillation boundary will move toward higher inlet subcooling region when mass flow rate is less than the value in immovable state. The excursion of the oscillation boundary will increase when the maximum heaving acceleration and the maximum rolling (or pitching) angle increases or the period of rolling (or pitching) decreases. The heaving period will affect the boundary obviously only in a certain range. (authors)

[en] Experimental results of flow oscillation under small break loss-of-coolant accident(SBLOCA) on upper plenum of nuclear heating reactor are presented.The experiment is carried out on the thermohydraulic test system HRTL-5 of the 5 MW nuclear heating reactor, which is a natural circulation system. The variations of pressure, temperature, void fraction, and circulation mass flow are described. Flow oscillation is described and its development mechanism is studied specially. Results show that the pressure decreasing in LOCA and bubbles producing caused by flashing,and mass flow variation have influence on each other and cause cyclical variations of flow and heat transfer

[en] Falling liquid film is widely used in nuclear engineering, thermal engineering, chemical engineering, and electronics owing to its high efficiency of heat and mass transfer with small temperature difference, flow rate and power consumption, such as cooling towers, AP1000 passive containment cooling system (PCCS), and multiple-effect distillation (MED) for seawater desalination. To investigate the fluid dynamics of the falling liquid film, a simultaneous measurement technique with only one camera, which combined planar laser induced fluorescence (PLIF) and particle image velocimetry (PIV), has been applied in the liquid film flow experiment. Image acquisition in this research utilizes a long distance microscope and provides high spatial resolution at a relative large working distance. With this experimental method, it becomes feasible to generate streamwise velocity evolution of film flow on an inclined plane. In addition, film thickness measurements are performed using a laser confocal displacement technique enabling investigation of the wave dynamics. Isothermal film flow with systematic variations of both Reynolds number (Re=11.5∼32.9) and the inclined angel (β=20deg) are investigated. Comparison between experimental results and previous published results is made to verify the measurement method. (author)

[en] Test pressures are 1.0∼4.0 MPa, heating powers 27∼190 kw, inlet subcooling 5∼80 degree C, water used as coolant, and steam quality at the outlet of test section is less than 0.05. These test conditions cover the parameters for a typical 200 MW heating reactor. The experimental results show that the steam quality is the dominant factor in a natural circulation system with low pressure and low steam quality about the effect of system pressure, heating power and inlet subcooling on the flow rate, relative oscillatory amplitude and oscillatory region of flow rate

[en] A research program on thermal-hydrodynamic stability of the two-phase flow, simulating the behavior in the primary loop of a nuclear heating reactor developed by the Tsinghua University institute of nuclear energy technology (INET) in China has been executed for several years. In the integrated primary loop of the NHR heating reactor, the natural circulation of the coolant water was adopted with low system pressure, low steam quality at the exit of the core and a relatively long riser above the core. It is important to keep the reactor operating under stable conditions with enough safety margins. The program was aimed at: (1) accumulating experimental data for verification of the models and codes used in the design and safety analysis of this type of reactor; (2) understanding the unstable behavior, its physical mechanisms and parameter effects. The results of the study show that under certain geometric conditions and operating parameters a self-sustaining, low frequency, even amplitude mass flow oscillation may be excited at very low steam qualities. Stability maps under different conditions are provided. An unstable region, which exists between the single-phase stable region and the low steam quality bulk boiling stable region, was experimentally demonstrated. (orig.)

[en] The study on flow stability of water and steam two phase mixture in a natural circulation system with relatively low pressure and low steam quality has been promoted by the design and development of nuclear heating reactor. When the system pressure was changed from 1.0 to 4.0 MPa the experimental results about the flow characteristic, obtained from the test loop HRTL-200 which uses water as coolant, are presented. The experimental conditions are as following: heating power is 131 kw, flow resistance coefficient on the entrance of test section is 25, and the subcooling are from 5 to 80 degree C. The studied parameters cover ones of the 200 MW Heating Reactor. The results show that with the increase of system pressure the natural circulation mass flow rate will decrease and the instability region will become smaller, but the change tendency will become un-obvious after the system pressure is greater than a certain value. With the increase of system pressure, the oscillation amplitude of the mass flow rate will decrease and the vibration period will almost not change in the instability region

[en] The heat and mass transfers in the interface of steam and liquid and condensation near the wall with non-condensable gas were analyzed. A steam-gas pressurizer model was developed, the process of pressure transient in the pressurizer with the non-condensable gas was investigated and the thermal-hydraulic characteristics of a steam-gas pressurizer were described. The calculation results were verified with the results from the MIT pressurizer experiment. The results show that the calculation accuracy using pressurizer model without non-condensable gas is high, the relative deviation is 0.8% and the peak pressure is 0.647 MPa. When the mass fraction of non-condensable gas is from 0 to 20%, the calculation accuracy decreases, the maximum relative deviation is 15.4% and the peak pressure is from 0.647 MPa to 1.02 MPa. It's found that the non-condensable gas plays an important role on the pressure response in the gas-steam pressurizer. When the mass fraction and varieties of non-condensable gas are different, the pressure response in the pressurizer is significantly different. (authors)