CIWA - Condensation Induced Water Hammer

Motivation and Objectives

Condensation Induced Water Hammer can occur in a variety of technical applications. Wherever subcooled water is brought into contact with hot steam via a sufficiently large exchange surface, there is a risk of abrupt condensation. This occurs, for example, in the chemical industry or in the emergency cooling of a nuclear reactor, where cooling water is fed into the pipes of a steam-conducting system. Under certain operating conditions, the two-phase flow of water and water vapour that is generated takes on flow forms that promote condensation. The stochastically occurring condensation shocks show a multiple of the operating pressure of the system, which can result in the bursting of pipelines or system components.

In order to design endangered plant sections in such a way that they can withstand the pressure impulse, simulation programs are increasingly used in plant design. Current calculation programs, however, describe the occurrence and severity of condensation shocks only inadequately, as there is insufficient detailed knowledge of the thermohydraulic flow processes during the pressure impulse. In nuclear technology in particular, there is a need for research and development in the calculation and computer-aided simulation of safety-relevant scenarios with transient, thermohydraulic flow processes in pipelines. New, experimental and analytical analyses show that there is a necessity to check existing models to see whether they provide adequate results and, if this is not the case, to improve and validate the models appropriately.

Project Aim

The primary goal is the recording and evaluation of fast contact condensation processes as well as an extension of existing calculation possibilities. For this purpose, experimental results will be obtained at a total of three test facilities and used for the validation of simulations with different program codes. The evaluation can then show the current limits of the calculation possibilities. On the basis of theoretical and experimental work, a calculation tool will be developed which meets the requirements regarding the determination of conservatively covering results. For these purposes an additional validation with the results of the test facilities of the project partners under changed geometry and operating conditions is carried out. The practical applicability of the model in practice is an important requirement. For this purpose, the CIWA module is to be coupled to external system and CFD codes by developing a transparent data interface. In the above-mentioned focal points, the young scientists involved in the joint project will be integrated alternately and thus receive a strong practical orientation with the aim of maintaining competence in power plant technology.

The Project Team

The project is being carried out by a total of six project partners. The competences in the team are composed of well-founded theoretical basic knowledge at the universities and decades of hands-on experience at the Technical Inspection Associations (TÜV). Due to the close cooperation in the joint project as well as the thematically comprehensive and related topics, the greatest possible integration of the project partners and work is guaranteed. The overriding goal of all project partners is to maintain competence in the field of nuclear technology and related technical fields of application. For this purpose, the results and the know-how gained will be communicated to junior staff through seminars lasting several days, publications and websites. The project thus makes significant contributions to ensuring the safety of nuclear power plants in operation according to the state of the art in science and technology and to maintaining competence.