An Industrial Scale Test Rig for the Investigation of Heat Transfer to Supercritical Water in Advanced Power Engineering Applications

摘要

Heat transfer to supercritical water in heated tubes and channels is relevant for steam generators in conventional power plants and future concepts for supercritical nuclear and solar-thermal power plants. As more renewable, volatile energy sources feed the power grid, existing conventional supercritical steam power plants are required to shift towards more flexible operation to sustain the security of supply. This requires advances in the range of their operating parameters, leading to off-design conditions in their steam generators. At these conditions, conventional models fail to reliably predict the heat transfer coefficient. Moreover, the development of designs for future supercritical nuclear reactors and solar-thermal power plants requires an expanded understanding of supercritical heat transfer. A new experimental facility, the High Pressure Evaporation Rig HIPER, engineered, constructed and commissioned at the Institute for Energy Systems (Technische Universitat Munchen) aims to provide heat transfer data to fill the existing knowledge gaps at these conditions. The test rig consists of a closed loop high pressure cycle, in which de-ionized water is fed to an instrumented test section heated by the application of direct current. It is designed to withstand a maximum pressure of 380bar at 580°C in the test section. The test section is a vertical tube (material: AISI A213/P91) with a 7000mm heated length, a 15.7mm internal diameter and a wall thickness of 5.6mm. It is equipped with 70 thermocouples distributed evenly along its length. The power supply of the plant can deliver 1MW of power. The test rig enables the determination of heat transfer coefficients in the supercritical region at various pressures, heat flux densities, and mass flux densities. Transients of these parameters, corresponding to load changes in the steam generator, and their effect on heat transfer can also be investigated. In a first series of tests, experiments are conducted to provide data on normal and deteriorated heat transfer under vertical upward flow conditions. The test section pressure, the mass flux density and the heat flux density are adjusted individually to investigate their individual effects on the heat transfer coefficient. The data is then compared to existing models for the prediction of the heat flux necessary for the onset of heat transfer deterioration. Depending on the operating conditions, a large deviation between the predictions of the existing models is observed.