EXPERIMENTAL INVESTIGATION AND ANALYTICAL MODELING OF A CLOSED TWO-PHASE THERMOSYPHON WITH IMPOSED CONVECTION BOUNDARY CONDITIONS

A closed two-phase thermosyphon operating with Refrigerant-11 and with imposed convection boundary conditions at the heated and cooled surfaces is experimentally investigated and analytically modeled with a lumped parameter model for varying working fluid temperatures. The thermosyphon exhibits different operational modes depending on the heating and cooling fluids' temperature difference. An increase of this temperature difference produces at first a maximum heat transfer rate identified with the flooding heat transfer limit. Beyond this limit the thermosyphon operation reverts to a different steady state through a transient non-equilibrium process. The new steady state, identified as the thermal blocking condition, produces a lower heat transfer capacity and is attributed to the simultaneous existence of: (1) a new flooding state near or at the exit of the adiabatic section, and (2) the dryout in the evaporator resulting from the transfer of liquid in the evaporator pool to the condenser during the transient process which leads to the thermal blocking condition. The limiting operational modes of the thermosyphon are modeled by a lumped parameter model that accounts for different geometrical configurations and liquid entrainment in the vapor. A comparison between the predicted and experimental heat transfer rates, prior and during the thermal blocking condition, demonstrates the model's utility to predict complex thermohydrodynamic processes in a thermosyphon

Assessing the pyroclastic flow hazard at Vesuvius

IN large eruptions, Vesuvius has generated catastrophic avalanches of tephra and hot gases, such as those that destroyed Pompei and Herculaneum in AD 79, and Torre del Greco and surrounding towns in 16311,12. These avalanches (pyroclastic surges and flows) are produced from collapses of the eruptive column, and can travel at >100 m s-1, with temperatures exceeding 800 °C. In 1944 Vesuvius ended its most recent cycle of activity, which had begun with the explosive eruption of 1631. Here we use numerical simulations to assess the hazards posed by the pyroclastic flows that are likely to accompany the onset of the next cycle of activity. We examine three different scales of eruption, and use vent conditions established by modelling magma ascent along the conduit13,14. Our results indicate that large- and medium-scale eruptions can produce complete destruction in the 7 km radius around the volcano (an area in which one million people live and work) in about 15 minutes or less, and that only small-scale eruptions can be arrested by the topographic relief of Monte Somma.Published551-5545V. Dinamica dei processi eruttivi e post-eruttiviJCR Journa

Primary Dural Lymphoma: Clinical Cases and Literature Review

Primary dural lymphoma (PDL) is an extranodal non-Hodgkin lymphoma that accounts for less than 1% of all central nervous system lymphomas. Primary dural lymphoma grows from the dura mater, and it is often diagnosed as meningioma or acute subdural hematoma due to its radiological characteristics. Surgery is the gold standard of therapy; in many patients, PDL is relatively benign with good outcome. Authors report their experience in three patients affected by extranodal non-Hodgkin lymphoma (PDL) mimicking a meningioma