Loading...
Colonna, Piero
Email Address
Birth Date
Research Projects
Organizational Units
Last Name
Colonna
First Name
Piero
Name
Piero Colonna
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
ON AIR-COOLED CONDENSERS FOR ORC SYSTEMS OPERATING WITH ZEOTROPIC MIXTURESGalieti, Lorenzo; De Servi, Carlo; Alfani, Dario; Silva, Paolo; Bombarda, Paola; Colonna, PieroThe use of mixtures as working fluids of ORC systems is being intensively investigated because of the better temperature profile matching achievable in the heat exchangers, resulting in lower thermodynamic irreversibilities and increased efficiency. The gains are expected to be higher for lowtemperature air-cooled power plants, where the ratio between the auxiliary power consumption associated to the cooling of the working fluid and the net power output of the ORC plant is higher. For instance, a temperature glide in the condenser may enable a reduction in the fan consumption at the cost of an increased heat transfer area, and possibly a decrease in the minimum temperature of the thermodynamic cycle. This solution is expected to be attractive for geothermal applications: since the drilling of the geothermal well is by far the dominant cost, the additional investment for the condenser can be more easily compensated by the increased revenues related to the greater electrical power output. This study focuses on the modelling and sizing of an air-cooled condenser for geothermal ORC power plants operating with working fluid binary mixtures. A detailed fin and tube air cooled condenser model is developed and integrated with an in-house tool for the simulation of ORC systems. Working fluid thermodynamic properties are computed with the PCP-SAFT equation of state (EoS). The tool is used to investigate the effect of the condenser design assumptions on the geothermal plant maximum power output for an optimal working fluid mixture, whose composition is determined by optimizing the PCPSAFT parameters. The outcome is a pseudo-fluid mixture that represents the ideal working fluid for the given thermal source. The results indicate that the adoption of mixtures allows the air-cooler consumption and generally the minimum cycle temperature to be decreased, leading to an increased plant efficiency. In addition, design guidelines for the condenser are derived, based on the tradeoff between component size and plant efficiency. Finally, the optimization results show that if the onset of the mixture condensation occurs in the recuperator, it might be possible to reduce the fan consumption and size of the condenser simultaneously, albeit at the expense of an increased complexity of the regenerator design.- Mechanical Design and Rotor-dynamic Analysis of the ORCHID TurbineMajer, Matteo; Chatterton, Steven; Dassi, Ludovico; Secchiaroli, Alessio; Gheller, Edoardo; De Servi, Carlo; Pennacchi, Paolo; Colonna, Piero; Pini, MatteoThe ORCHID turbine is a 10 kW, high-speed (~100 krpm) radial-inflow organic Rankine cycle (ORC) turbine, under realization in the Propulsion and Power laboratory of Delft University of Technology. The turbine will be installed and tested in the Organic Rankine Cycle Hybrid Integrated Device (ORCHID) facility, the setup for fundamental and applied studies on ORC technology currently in operation in the same lab. Experimental data from future measurement campaigns will be employed to validate numerical tools and develop best practices for designing and operating these unconventional machines. This work documents the recent design efforts to define the functional requirements, the necessary components, and the mechanical assessment of the turbine test bed. In particular, the detailed design of the rotor assembly, carried out in cooperation with the Rotor-dynamic research group of Politecnico di Milano, is described with emphasis on three main aspects. First, the derivation of the damping characteristics of a squeeze-film-damper cartridge for turbochargers, which has been selected as support bearing for the turbine shaft. Secondly, the estimation of the stiffness and damping coefficients of a labyrinth gas seal with swirl breakers, using 3D CFD simulations of the flow path. Finally, linear elastic rotordynamic simulations were performed on a finite beam element model of the resulting turbine shaft. The bearing stiffness, initially estimated using Hertz contact theory, was varied to investigate the sensitivity of the rotor critical speeds to it.
