Proceedings of the XIII International Symposium on Dynamic Problems of Mechanics (DINAME 2009), Almeida, C. A. (Editor), ABCM, Angra dos Reis, RJ , Brazil, March 2nd - March 6th, 2009 Construction of a Demonstrative Apparatus for the Thermoacoustic Refrigeration Effect Flávio de Campos Bannwart <fcbannwart@fem.unicamp.br > José Roberto de França Arruda <arruda@fem.unicamp.br > Departamento de Mecânica Computacional – DMC Faculdade de Engenharia Mecânica - FEM Universidade Estadual de Campinas – UNICAMP Cidade Universitária “Zeferino Vaz” Rua Mendeleiev, 200 Bairro Barão Geraldo Campinas/SP – CEP: 13083 – 860 BRASIL Ph. : +55 19 3521-3386 Fax : +55 19 3289-3722 (Diretoria/Pós-Graduação) Abstract: Thermoacoustic refrigeration has been developed since the early eighties, mostly in the United States, Europe and Japan. However, in the last decade, a few research groups have started preliminary investigations in Brazil. At Unicamp specifically, a demonstrative apparatus was built in order to reproduce the thermoacoustic effect, aiming at refrigeration or heat pumping applications. The construction elements involved were very simple, consisting basically of an acrylic tube, an automotive catalyser (stack) and a moveable piston directly connected to a small shaker. The purpose of the shaker is to provide mechanical power, acoustically, inside the tube filled with atmospheric air. As a consequence of this input power, acoustic waves cross the stack on its axial direction through its longitudinal holes. When this happens at a resonance frequency of the air inside the tube and a standing wave is formed, a gas parcel has its expansion and contraction at fixed spots, establishing therefore only one way of thermal interaction with the stack internal walls, so that a net heat is transferred from one end to another of the stack. The lenght of the tube must be chosen as a function of the first mode wavelength of the standing wave, which is a function of the stack hole dimensions, and the stack must be positioned in a suitable way with respect to the wave pattern. Measurements showed a consistent temperature difference of 2.2ºC between the stack ends, which demonstrated the presence of the thermoacoustic effect in this apparatus. Ongoing investigations aim at improving the insulation conditions, incrementing the gas pressure and specific power input, and also the installation of heat exchangers, according to proper analytical considerations. In this paper, the operative principle of a standing wave thermoacoustic refrigerator is reviwed and the preliminary results obtained with the demonstration apparatus are presented and discussed. Keywords: thermoacoustic, acoustic, transport phenomena, refrigeration NOMENCLATURE P = pressure T = temperature Cp = specific heat at const. P c = sound speed f = frequency k = gas thermal conductivity L = tube length Greek Symbols ΔP = gap of pressure ΔT = gap of temperature δk = thermal penetration depth ρ = density λ = wave length Subscripts H hot C cold pm prime-mover r refrigerator