Rejane De Césaro Oliveski - decesaro@mecanica.ufrgs.br
Arno Krenzinger - arno@mecanica.ufrgs.br
Horácio A. Vielmo - vielmoh@ufrgs.br
Universidade Federal do Rio Grande do Sul, Departamento de Engenharia Mecânica
CP 17819 - 90035-972 - Porto Alegre, RS, Brasil

This paper presents the results of temperature distribution in a vertical cylindrical tank, submitted to natural convection conditions due to thermal losses to the ambient by lateral wall, top and bottom. The numerical simulation is performed with 3 different versions of the Multiple Nodes model (unidimensional) and with a bidimensional model that uses the conservation of mass, momentum and energy equations, discretized by the Finite Volumes Method. The cooling of the water in the tank is simulated with every numerical model in 40 different configurations, using 4 aspect ratios, 5 insulation thickness and 2 volumes. Furthermore, 2 computational strategies created in the Multiple Nodes model aiming to obtain stratified temperature profiles are described here. Comparisons among the various Multiple Nodes models and between these and the bidimensional model are presented too.

Keywords: thermal reservoirs, numerical simulation, multiple nodes, finite volumes.
 
 

J. C. Camargo – joaoc@fem.unicamp.br
Universidade Estadual de Campinas, Laboratório de Hidrogênio
Cx. P. 6039-  13083-970 – Campinas, SP, Brasil
F. R. Apolinário – rezende@ifi.unicamp.br
E. P. da Silva – lh2ennio@ifi.unicamp.br
Universidade Estadual de Campinas, Laboratório de Hidrogênio
Cx. P. 6039-  13083-970 – Campinas, SP, Brasil
 

The use of the solar energy, for thermal or photovoltaics ends, depends basically on the amount of radiation that reaches the ground in the place where desires to carry through this use, defining the necessary area of the collectors, or panels, that in turn are the main components of the final cost of the system and, therefore, of the viability or not on its use. The incident radiation in the terrestrial surface is minor  that one  reaches the top of the atmosphere due to the absorption and dispersion factors. The objective of this work is to present a model of forecast  the monthly average radiation for ends of use in systems of flat solar collectors for heating water, in the city of Campinas - São Paulo, Brazil. This work has been developed by the Hydrogen Laboratory of the Institute of Physics of the Unicamp, being also used for other applications with solar energy. Based in the radiation data, taken  from a local station, a theoretical study was developed to calculate a parameter of loss of radiation when this cross the atmosphere. This Kt loss factor, has basic importance for the knowledge of the effective available energy for use. With this data it is possible to determine, on the basis of the incident radiation in the top of the atmosphere, the value of the radiation on a surface.

Keywords: Solar energy, Radiation absorption
 
 

Gabriel I. Medina Tapia – gabriel@emc.ufsc.br
Sergio Colle – colle@emc.ufsc.br
Universidade Federal de Santa Catarina, Departamento de Engenharia Mecânica
Cx. P. 476 - 88.040-900 - Florianópolis – SC, Brasil

Este trabalho apresenta uma análise de otimização termodinâmica e econômica do ciclo de refrigeração com ejetor assistido por coletor solar, para ar-condicionado. O
acoplamento ótimo entre a energia solar e a energia convencional é estudado. Foram encontradas condições ótimas de operação para o sistema. Procedimentos de otimização do ejetor são também apresentados. A análise termoeconômica é realizada através do método P1 - P2. Para este método encontrou-se uma relação entre a fração solar e a área do coletor. A modelação do sistema é apresentada em detalhes, considerando-se as equações da conservação de energia, quantidade de movimento linear, equação da continuidade, equação de estado e as equações de acoplamento do sistema solar e o mecânico. São apresentados resultados de otimização termoeconômica para a amônia. Uma análise da sensibilidade dos parâmetros sobre o desempenho e o retorno dos investimentos é também realizada, procurando-se ressaltar as vantagens do ciclo.

Palavras-chave: Energia Solar, Refrigeração, Termodinâmica
 
 

Samuel L. de Abreu - samuel@emc.ufsc.br
Universidade Federal de Santa Catarina, Laboratório de Energia Solar
Campus Universitário SN - Trindade - Florianópolis, SC 88040-900 Brasil

Sergio Colle - colle@emc.ufsc.br
Anand P. Almeida - anand@labsolar.ufsc.br
Sylvio Luiz Mantelli Neto - sylvio@labsolar.ufsc.br

The incident solar radiation is one of the most important inputs for simulation programs of solar thermal systems and of thermal behavior of buildings. Actually, these kind of data are well known for countries where long-term measurements of incident solar radiation are available. This fact allows the use of statistical procedures to generate typical meteorological years for simulation. In Brazil, solar radiation data are measured in sites spread all over the country by individual efforts. These data are usually measured only during short periods of time, does not have any standardization, and also are not easy to access. The present work describes the steps of qualification and data-filling used to handle the raw data measured in a specific location. The present data were measured in the radiometric station of the Solar Energy Laboratory (Federal University of Santa Catarina) in Florianopolis, for the period of 1990 to 1999.

Keywords: Solar Energy, Solar Radiation, Solar Heating, TMY
 
 

José Maurício Gurgel - gurgel@les.ufpb.br
Universidade Federal da Paraíba, Laboratório de Energia Solar, CT/CPGEM-DTM
C.P. 5115 - 58051-970 - João Pessoa, PB, Brasil

José Espínola Jr. - UFPB - CPGEM- ETFSE/UNED
Luiz Simão Andrade Filho - UFPB - CT - DTCC
Francisco Marcondes - UFPB- CCT-DEM

The use of a solid adsorption cooling unit based on the binary silica gel/water couple constitute an very promising way to harness solar energy refrigeration purposes. Here is presented an mathematical model for the simulation of the system under several use conditions and it was shown coherent when compared with some experimental results. The several accomplished simulations showed the need to be projected a modulate reactor that can offer cooling easiness during the night period and shown the advantage of the use of an solar collector that can be easily opened and your thermal insulating module placed across the glass close the thermal radiation when the desorption process finish. The simulations results presented here shown an better COP for this configuration through an better cooling of the collector at night.

Keywords: Solar energy, Adsorption, Silica-gel, Refrigeration