An Immersed Particle Heat Exchanger for Externally Fired and Heat Recovery Gas Turbines

Abstract

Designing and manufacturing high-efficiency heat exchangers is usually considered a limiting factor in the development of gas turbines employing either heat'recovery JouleBrayton cycles or extemal combustion. In this work, an innovative heat exchanger is proposed, modeled, and partially tested to validate the developed numerical model employed for its design. The heat e.xchanger is based on an intermediate medium {aluminum oxide AI2O)) flowing in countercurrent through an hot stream of gas. In this process, heat can be absorbed from the hot gas, temporarily stored, and then .similarly released in a second pipe, where a cold stream is warmed up. A flow of alumina particles with very small diameter (of the order of hundreds of microns) can be employed to enhance the heat transfer. Experimental test.K demonstrate that simple one-dimensional steady equations, also neglecting conductitm in the particles, can be effectivelv employed to sinuilate the flow in the vertical part of the pipe, namely, to compute the pipe length required to achieve a pre.uribed heat exchange. On the other side, full three-dimensional computational fluid dynamics simutati(ms have been performed to demonstrate that a more thorough gas flow and particle displacement analysis is needed to avoid a had disirihtitioit of alutnina particles and, thus, to achieve high thermal efficiency.

Developments in the design and construction of continuous full‐scale ultrasonic devices for the EVOO industry

“…The main considered patents were three, in particular (i) by Jimenez and co‐inventors , which protected the idea of a system for the control of applied ultrasound based on the information provided by the temperature sensors; (ii) by Pieralisi , which proposes to accelerate the oil extraction process applying ultrasound directly in contact with the olive paste with the synergetic effect of a heater‐conveyor; and (iii) by Masotti and co‐authors which patented an ultrasound devices useful to improve the quantity of polyphenols the turbidity stability of the EVOOs. While, the considered research activities concerned the effects of heat‐exchange , both warming and cooling, in order to exploit the multiple combinations between different sonication power intensities and temperatures, in particular the works made by Amirante et al , Veneziani et al , and Balzano et al .…”

Analysis of the complementary energy losses of a high temperature gas to gas heat exchanger based on a solid intermediate medium

“…Cold particles are collected at the bottom of the second module and delivered back at the top of the plant by the conveyor. The potential of such heat exchange mode has been demonstrated both theoretically and experimentally: an effective onedimensional model, which allows us to compute the column lengths required for achieving the heat exchanger design efficiency, was proposed and validated by means of a test bench, reproducing the upper half of the proposed Immersed Particle Heat Exchanger [8]. It is noteworthy that, due to the small particle size, conduction inside the intermediate medium can be neglected, as demonstrated in [10] by means of DNS simulations.…”

“…Some of the authors have recently proposed and optimized [8][9][10] an innovative Immersed Particle Heat Exchanger, which employs an intermediate medium with high thermal capacity: with reference to Figure 1, small alumina particles fall in a column where hot gas, coming from a separate combustion chamber (external combustion gas turbine) or from turbine outlet (heat recovery cycle), flows from the bottom to the top; the warmed up particles are then collected at the bottom of the column and inserted at the top of a second column where they transfer the accumulated heat to a counter-flowing cold gas. Cold particles are collected at the bottom of the second module and delivered back at the top of the plant by the conveyor.…”

“…It is noteworthy that, due to the small particle size, conduction inside the intermediate medium can be neglected, as demonstrated in [10] by means of DNS simulations. The experimental facility was also equipped with a second vertical pipe, used to demonstrate that very fine particles, which could damage turbine blades in a real plant, can be completely eliminated by means of centrifugation [8,9]. In addition, a tri-dimensional CFD model, capable of recognizing all 3D geometrical details, was developed and used to optimize the main geometrical parameters affecting the heat exchange effectiveness [9].…”

“…As well, a second mechanical system must be placed below the bottom column in order to depressurize and transfer the particles into a pneumatic conveyor, capable of delivering back the particles to the top of the plant for a continuous operation mode. Such devices must operate without crushing the particles, both to maintain their size constant and to avoid dust [8].…”