Navegando por Autor "Hovsapian, Rob"

Agora exibindo 1 - 3 de 3

Item
Notional all-electric ship systems integration thermal simulation and visualization
(2012) Vargas, Jose Viriato Coelho; Souza, Jeferson Avila; Hovsapian, Rob; Ordonez, Juan Carlos; Chiocchio, Tim; Chalfant, Julie; Chryssostomidis, Chryssostomos; Dilay, Emerson
This work presents a simplified mathematical model for fast visualization and thermal simulation of complex and integrated energy systems that is capable of providing quick responses during system design. The tool allows for the determination of the resulting whole system temperature and relative humidity distribution. For that, the simplified physical model combines principles of classical thermodynamics and heat transfer, resulting in a system of three-dimensional (3D) differential equations that are discretized in space using a 3D cell-centered finite volume scheme. As an example of a complex and integrated system analysis, 3D simulations are performed in order to determine the temperature and relative humidity distributions inside an all-electric ship for a baseline medium voltage direct current power system architecture, under different operating conditions. A relatively coarse mesh was used (9410 volume elements) to obtain converged results for a large computational domain (185m×24m×34m) containing diverse equipment. The largest computational time required for obtaining results was 560 s, that is, less than 10 min. Therefore, after experimental validation for a particular system, it is reasonable to state that the model could be used as an efficient tool for complex and integrated systems thermal design, control and optimization.
Item
Temperature and pressure drop model for gaseous helium cooled superconducting DC cables
(2013) Ordonez, Juan Carlos; Souza, Jeferson Avila; Shah, Darshit Rajiv; Vargas, Jose Viriato Coelho; Hovsapian, Rob
The need to transfer large amounts of power in applications where cabling weight and space are a major issue has increased the interest in superconducting cables. Gaseous helium and neon are being considered as possible coolants due to their suitability for the expected operating temperature ranges. Gaseous helium is preferred due to its higher thermal conductivity and relatively lower cost than neon. This paper enhances a previously presented mathematical model of a superconducting cable contained in a flexible cryostat by including flow pressure drops. In this way, the model is capable of properly sizing and minimizing fan power, and allows the prediction of system response to localized heating events (e.g., quenching). A volume element model approach was used to develop a physics model, based on fundamental correlations, and principles of classical thermodynamics, mass and heat transfer, which resulted in a system of ordinary differential equations with time as the independent variable. The spatial dependence of the model is accounted for through the three-dimensional distribution of the volume elements in the computational domain. The model numerically obtains the temperature distribution under different environmental conditions. Pressure drop calculations are based on realistic correlations that account for the wavy nature of the coolant channels. Converged solutions were obtained within the imposed numerical accuracy even with coarse meshes.
Item
Thermal modeling of helium cooled high-temperature superconducting DC transmission cable
(IEEE, 2011) Souza, Jeferson Avila; Ordonez, Juan Carlos; Hovsapian, Rob; Vargas, Jose Viriato Coelho
The recent increase in distributed power generation is highlighting the demand to investigate and implement better and more efficient power distribution grids. High-temperature superconducting (HTS) DC transmission cables have the potential to address the need for more efficient transmission and their usage is expected to increase in the future. Thermal modeling of HTS DC cables is a critical tool to have in order to better understand and characterize the operation of such transmission lines. This paper introduces a general computational model for a HTS DC cable. A physical model, based on fundamental correlations and principles of classical thermodynamics, mass and heat transfer, was developed and the resulting differential equations were discretized in space. Therefore, the combination of the physical model with the finite volume scheme for the discretization of the differential equations is referenced as Volume Element Model, (VEM). The model accounts for heat transfer by conduction, convection and radiation obtaining numerically the temperature distribution of superconductive cables operating under different environmental, operational and design conditions. As a result, the model is expected to be a useful tool for simulation, design, and optimization of HTS DC transmission cables.