Heat and mass transfer in three-phase fluidized-bed reactors—an overview

Modeling simultaneous nitrification and denitrification (SND) in a fluidized bed biofilm reactor

Three Phase Sparged Reactors — Some Design Aspects

Solid-liquid mass transfer in a gas-liquid-solid fluidized bed

Heat transfer characteristics of two (liquid-gas, liquid-solid) and three (liquid-gas-solid) phase fluidized beds have been studied in a 15.2 cm-ID column fitted with an axially mounted cylindrical healer. Effects of gas velocity (0-12 cm/s). liquid velocity (0-16cm/s), particle size (1.7-8.0 mm) and liquid viscosity (0.001-0.039 Pa s) on heat transfer coefficient were determined. The heat transfer coefficient increased with fluid velocities and particle size and it decreased with liquid viscosity in two and three phase fluidized beds. The bed porosity at which the maximum heat transfer occurred decreased with particle size but increased with liquid viscosity. The coefficient were correlated in terms of experimental variables. Modified Nusselt number from the present and previous studies has been correlated with modified Prandtl and Reynolds numbers.

Heat transfer characteristics of three phase fluidized beds

The axial dispersion characteristics of liquid phase in two (gas-liquid, liquid-solid) and three (gas-liquid-solid) phase fluidized beds were studied in a 14.5 cm-I.D. column. The effects of liquid velocity (2-13 cm/s), gas velocity (0-12 cm/s), liquid viscosity (1-27 cP), surface tension (38.5-76 dyn/cm) and particle size (1.7-6.0 mm) on axial dispersion of liquid phase were examined. Liquid-phase axial dispersion in terms of Peclet numbers were correlated empirically by equations involving the ratio of fluid velocities and the ratio of particle-to-column diameters. The dispersion coefficients increased with gas flow rate, liquid surface tension and viscosity. However, liquid viscosity generally reduced the coefficient in beds of smaller particles at higher gas rates.

Axial dispersion characteristics of three phase fluidized beds.

High-temperature superconducting (HTS) direct current (dc) power cable systems, capable of delivering power exceeding 10 MW while being cooled with cryogenic helium gas, have been developed for applications on naval electric ships, electric aircraft and in data centers. Current injection from room temperature into the superconducting power cable causes by far the greatest heat load to the cryogenic system. Efficient current leads with integrated helium gas heat exchangers were developed to inject a current exceeding 1 kA from room temperature into a superconducting Conductor on Round Core (CORC®) power cable, without the need for liquid nitrogen pre-cooling. A 2 m long single-pole CORC® power cable system that included current leads was cooled using a Stirling cryocooler with a closed-loop helium gas circulation system. The turnkey power cable system allowed cool down from room temperature to its operating temperature of 60 K–70 K within 5 h, after which continuous operation at 1.2 kA was demonstrated. The successful development and demonstration of a CORC® power cable with current leads containing integrated helium gas heat exchangers enables widespread implementation of HTS MW-class, high current density superconducting dc power cables in many applications with constrained space that require a power dense solution.

A turnkey gaseous helium-cooled superconducting CORC® dc power cable with integrated current leads

Liquid Nitrogen (LN2) is used as the cryogen and is part of the dielectric insulation system in most high temperature superconducting (HTS) power cables. However, in electric propulsion systems for transportation, using LN2 is not feasible due to asphyxiation concerns in the event of a leak in a confined space. Gaseous helium (GHe) has been proposed as an alternate cryogen to relieve this asphyxiation concern. GHe has benefits such as a wider operating temperature range and versatility for a centralized cryogenic cooling system for multiple devices which could potentially reduce the overall weight of the superconducting system. The drawback is that GHe has a lower dielectric strength compared to LN2, which limits its use to low-medium voltage applications. A hybrid cryogen HTS cable was proposed using LN2 as the dielectric media and GHe as the cryogen of an HTS cable to solve the limitations and issues associated with each cryogen and explained in this paper. A 1-m prototype cable that used LN2 as the cryogen and dielectric was fabricated and dielectric breakdown measurements were performed on it to establish a baseline on what to be expected from the hybrid cryogen HTS cable.

Superconducting liquid cryogen insulated power cables for medium voltage applications

Superconducting power devices provide a solution to increase the flexibility and power density of electrical power systems for future electric ships. To assess the benefits and constraints of superconducting power devices it is necessary to understand the modifications required to the electrical power system. The paper focuses on recent development on superconducting generators, motors, and cables and assess their inclusion as part of notional superconducting power systems for future all electric ships.

SuPErShip – A Multidisciplinary Collaborative Study on System-Level Benefits of Superconducting Power Devices on Electric Ships

A prototype design of the Frequency Loss Induced Quench (FLIQ) protection system for high temperature superconducting magnets was validated on a small Second-Generation High-Temperature Superconducting (2G HTS) coil. Calorimetric measurements, based on liquid nitrogen boil-off rate, were performed to quantify the heat energy introduced by FLIQ system in the coil. The technique was previously used for steady state AC loss measurements and adopted for the transient losses generated in FLIQ operation. A series of tests of the FLIQ system on 2G HTS pancake coils were performed to study the dynamics of the quench and the energies involved in the quenching process. The results suggest the suitability of the FLIQ technique for quench protection of HTS coils. A measurement protocol of extended repetitive high-frequency current pulses established in the study provided a way to estimate the energy deposited by the AC losses generated in the coil by the FLIQ system. The measurement method described is a practical way to validate the design parameters of the FLIQ system and to evaluate the sensitives of the various design parameters of the FLIQ. The paper reports an experimental technique used to study the sensitivities of various FLIQ design parameters by establishing and measuring quasi-equilibrium heat load and boil-off rate as a result of extended repetitive high-frequency current pulses.

C. H. Kim

Papers

Axial dispersion characteristics of three phase fluidized beds.

A turnkey gaseous helium-cooled superconducting CORC® dc power cable with integrated current leads

Superconducting liquid cryogen insulated power cables for medium voltage applications

SuPErShip – A Multidisciplinary Collaborative Study on System-Level Benefits of Superconducting Power Devices on Electric Ships

Evaluation of Frequency Loss Induced Quench Protection Prototype at 77 K Using HTS Coils