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[en] Nuclear thermoelectric units with electric power as high as 200 KWT, in case of of lifted thermogenerator blocks by their technical, ecological, and economic chracteristics, meet the requirements of autonomous electric energy sources for land-based and sea units of the stationary and transportable type. This report describes the developement of a thermoelectric unit with two phase thermosiphons in the cooling circuits
[en] Single phase natural circulation is of interest in various energy systems, including solar heaters, nuclear reactors, geothermal power production, engine and computer cooling. The present paper deals with an experimental study on the influence of pressure drops on the behavior of a single-phase natural circulation loop. In a simple rectangular loop (MTT-1) located at DITEC, three series of tests have been carried out, with localized pressure drops (orifices of 6 mm, 10 mm and 14 mm diameter in the vertical legs) and different power levels. The experimental data are analyzed and compared with previous results obtained with smooth pipes, demonstrating the stabilizing effect of the pressure drops on the overall behavior of the loop
[en] Mass transfer time relaxation parameters for condensation affect the amount of the mass transfer in the phase change. In the present study, a numerical investigation has been implemented with four different parameters for the condensation process in a thermosyphon, with the parameter of 0.1 for the evaporation process. The numerical results were compared with the experimental results to validate the numerical methods. When the mass transfer time relaxation parameter for the condensation was set to the value considering the density ratio out of the four parameters, the numerical result was in good agreement with the experimental result. This numerical process is expected to be used to predict the temperature distribution in the thermosyphon more accurately.
[en] A new experimental facility is being developed for materials irradiation and testing at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR). Details of this facility have been presented before. A prototype of this facility, the Thermosyphon Test Loop (TSTL) has been built, and experimental data have been obtained and analyzed. Pretest calculations for this facility with the RELAP5-3D code have been presented previously as well as other calculations with the TRACE code. The results of both codes were very different. RELAP5-3D predicted much higher pressures and temperatures than TRACE. This paper compares calculated results with the TSTL experimental data. Comparison of calculations with the codes RELAP5-3D and TRACE with experimental data of the new TSTL facility has shown that TRACE results agree well with the data and that RELAP5-3D calculates very high pressures and temperatures. The TRACE code is well suited to model this facility and is being used for future calculations. (authors)
[en] This paper presents an experimental investigation on the heat transfer characteristics of a vertical flat thermosyphon (VFT). Several tests were performed to assess the effects of filling ratios, hydraulic radius, working fluid, and aspect ratio (Le/4HR) at a vertical orientation on the heat transfer characteristics of the VFT. It was found that the filling ratios and hydraulic radius affect heat flux: while the aspect ratios of VFT increased, the heat flux decreased. In addition, the working fluid changed from water and ethanol to R123 as the heat flux increases
[en] This study considers the transient physical phenomena in an open loop thermosyphon, where the wall heat conduction is coupled to the fluid hydrodynamics and heat transfer. Some simplifying assumptions allow a semi-analytical solution in several cases of practical importance. A U-shaped natural circulation loop open to the atmosphere and heated from one side is examined. The present analysis is applied to assess the performance of a natural convection system used for passive cooling of an advanced nuclear reactor containment. The present semi-analytical solution is found to favorably compare with a finite-difference solution of the full governing equations invoking the RELAP5/MOD2 code
[en] Highlights: • Annular thermosyphon shows higher heat transfer compared to concentric thermosyphon. • Annular thermosyphon requires new prediction model for flooding limit. • Fill ratio of working fluid affects the flooding limit of the annular thermosyphon. - Abstract: A passive in-core cooling system (PINCs) based on hybrid heat pipe can be adopted to enhance the passive safety of advanced nuclear power plants. A hybrid heat pipe is a heat transfer device that takes the dual roles of neutron absorption and heat removal by combining the functions of a heat pipe and a control rod. To observe the effect of neutron absorber material inside the heat pipe and fill ratio of the working fluid on the thermal performances of heat pipe including operation limit, an annular thermosyphon heat pipe (ATHP) that contains a neutron absorber inside a concentric thermosyphon heat pipe (CTHP) was experimentally studied in the condition of various fill ratios. The ATHP showed lower thermal resistances in the evaporator region with a maximum reduction of 20% compared to those of a CTHP. In terms of the operational limits, the ATHP showed a lower entrainment limit than the CTHP due to a smaller cross-section for vapor path in the evaporator region, which resulted in high shear at the vapor–liquid interface. In addition, increasing the fill ratio enhanced the entrainment limit by 18%.
[en] This study aims to experimentally investigate the heat transfer characteristics of a thermosyphon using nanofluids. A thermosyphon with three individual pipes, which share the internal volume of the evaporator section, was designed, and its performance was tested for various charge amounts, input powers of the evaporator section's heater, and concentrations of working fluids. The optimized charge amount of the thermosyphon using distilled water was 30%, and the thermal resistance of the thermosyphon with TiO2 nanofluid was 18.1% lower than that with Ag nanofluid. In addition, the heat transfer performance of the thermosyphon with TiO2 1% was optimized at an input power of 300W at the evaporator section's heater and a charge amount of 30%
[en] The R3B-Glad superconducting Magnet provides the field required for a large acceptance spectrometer, dedicated to the analysis of Reactions with Relativistic Radioactive ions Beams. In the framework of the FAIR Project to GSI and within NUSTAR physics program, the technical study started in 2006, and the engineering design is undertaken. One main feature of this butterfly-like magnet with graded, tilted and trapezoidal racetrack coils is the active shielding. It makes it possible to decreasing the field by two orders of magnitude within a 1.2 m length, despite the large opening on the outlet side of the magnet (around 0.8 square meters). The fringe field is lower than 20 mT in the target area beside the entry, while the main field is larger than 2 teslas, out of 2 m length. The other principal characteristics are as follows: first, a high level of magnetic forces (300 to 400 tons per meter), with little place to block the coils, requiring a very specific mechanical structure; then, the magnet protection system that is based on an external dump resistor, coupled to a strong quench-back effect, to prevent any damage of the coils which could be caused by the 24 MJ of stored energy; lastly, the indirect cooling of the cold mass with a two-phase helium thermosyphon. The overall size of the conical cryostat will be around 3.5 m long, 3.8 m high and 7 m broad. (authors)