PCCE - A Predictive Code for Calorimetric Estimates in actively cooled components affected by pulsed power loads P. Agostinetti, M. Dalla Palma, F. Fantini, F. Fellin, R. Pasqualotto Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti 4, 35127 Padova, Italy Abstract The analytical interpretative models for calorimetric measurements currently available in the literature can consider close systems in steady-state and transient conditions, or open systems but only in steady-state conditions. The PCCE code (Predictive Code for Calorimetric Estimations), here presented, introduces some novelties. In fact, it can simulate with an analytical approach both the heated component and the cooling circuit, evaluating the heat fluxes due to conductive and convective processes both in steady-state and transient conditions. The main goal of this code is to model heating and cooling processes in actively cooled components of fusion experiments affected by high pulsed power loads, that are not easily analyzed with purely numerical approaches (like Finite Element Method or Computational Fluid Dynamics). A dedicated mathematical formulation, based on concentrated parameters, has been developed and is here described in detail. After a comparison and benchmark with the ANSYS  commercial code, the PCCE code is applied to predict the calorimetric parameters in simple scenarios of the SPIDER experiment. Keywords: predictive, code, calorimetry, estimates, cooling Introduction During operations of fusion experiments, some components can be affected by high heat fluxes, that can lead to local dam- ages and component burnout if the heat load is not exhausted by a proper cooling system. Among these high heat flux compo- nents, there are some parts of the Neutral Beam Injectors (Radio Frequency drivers, acceleration grids, beam line components), of the Radio Frequency antennas, of the Divertor and of the Blanket. Measuring the temperature and thermal energy can be useful for the design of such components, and to have information on the energy fluxes inside the machines for monitoring and pro- tecting them during operations [1, 2]. In particular, measuring the energy absorbed by these components during short pulses can be useful before operating the experiment with long pulses, which are much more critical in terms of risks of damage. A simplified scheme of a generic actively cooled component subject to an externally applied power load is shown in Fig. 1. A certain mass flow ˙ m of coolant (water most of times) ex- hausts most of the heat absorbed by the component, being the remaining part exhausted by thermal conduction and radiation processes. As the components are generally inside a vacuum environment, convection processes with the surrounding fluid are not considered in this analysis. Calorimetric measurements can be carried out both in contin- uous working conditions and during pulsed power sessions. In the first case, a steady state condition is generally reached after a proper time interval and the following power balance formula Heat exchanger High Heat Flux Component Tout Tin Conduction Radiation Externally applied power (Pext) Other components Pump Figure 1: Cooling scheme of a generic high heat flux component. can be used to estimate the power absorbed by the component [3]: P = ρ · ˙ V · C f luid · (T out − T in ) (1) where ρ is the coolant density, ˙ V is coolant volume flow, C f luid is the coolant specific heat capacity (at constant pressure), T in is the coolant inlet temperature and T out is the coolant outlet temperature. ˙ V , T in and T out can usually be measured with flux meters and thermocouples respectively, while the thermo-physical proper- ties ρ and C f luid are known functions of the coolant temperature. In pulsed power sessions, there could be not enough time to reach a steady state condition, so it might be not possible to measure a value of T out that is stable for a sufficient time. In this case, Eq. (1) cannot be used for the calorimetric estimates, and more sophisticated mathematical tools must be adopted for Preprint submitted to Fusion Engineering and Design January 10, 2011