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COB313 ESCOAMENTO DE ÓLEO E REFRIGERANTE PELA FOLGA RADIAL EM COMPRESSORES ROTATIVOS DE PISTÃO ROLANTE / OIL AND REFRIGERANT FLOW THROUGH RADIAL CLEARANCE IN ROLLING PISTON COMPRESSORS
José Luiz Gasche, Álvaro Toubes Prata* & Rogério Tadeu da Silva Ferreira*
Departamento de Engenharia Mecânica, Faculdade de Engenharia - UNESP - Ilha Solteira
CEP 15.385-000 - Ilha Solteira-SP, Brasil - E-mail:gasche@feis.unesp.br
*Departamento de Engenharia Mecânica - NRVA, UFSC
CEP 88.040-900 - Florianópolis-SC, Brasil - E-mail prata@nrva.ufsc.br, rogerio@emc.ufsc.br
In this work, important points associated with the leakage of the refrigerant gas through the radial clearance in rolling piston compressors are discussed. This leakage is the main cause of volumetric efficiency loss. The principal characteristic of this leakage flow is its transient behavior since the chamber compression pressure, the absolute tangential velocity of the piston surface and the radial clearance, all vary with time during the compression cycle. These parameters must be determined by modeling the gas compression process and the piston dynamics, and by knowing the pump geometric characteristics. Another important aspect in this flow modeling is related to the nature of the leaking fluid: a mixture composed by oil and dissolved refrigerant. As this mixture flows through a low pressure region, the dissolved refrigerant separates from the oil, forming bubbles, so that the mixture shifts to a new equilibrium condition, and a two-phase flow is created. Also foam may form in the flow due to the large number of bubbles. Following this discussion, the importance of the inertial forces in the flow is analyzed and a first model to calculate the oil and refrigerant flow through radial clearance is presented.
Keywords: Compressor (Compressor), Refrigeração (Refrigeration), Refrigerante (Refrigerant), Óleo (Oil), Folga (Clearance)
COB346 FORÇA AXIAL ATUANDO NUM DIFUSOR RADIAL DEVIDO AO MOVIMENTO SÚBITO DA PALHETA / AXIAL FORCE ON THE FRONTAL DISK OF A AXIALLY FED RADIAL DIFFUSER WITH MOVING BOUNDARY
Carlos F. E. Alves1,*, Washington Braga Filho1 & Carlos A. Thompson2
1Departamento de Engenharia Mecânica, PUC-Rio - Rua Marques de São Vicente, 225
CEP 22453-900 Rio de Janeiro, Brasil - E-mail: wbraga@rdc.puc-rio.br
2Centro Universitário Augusto da Motta - Rua Paris 72
CEP 21041-020 Rio de Janeiro, Brasil - E-mail: cthompson@openlink.com.br
This paper reports preliminary numerical results of some aspects of the axially fed radial flow between parallel disks. Particularly, the characteristics of the axial force on a situation in which the frontal disk is suddenly moved to a new location (closer or further apart) is studied. The flow is assumed incompressible, laminar and isothermal.
Keywords: compressor; radial flow; finite volume; moving grid; space conservation/
compressores; escoamento radial; volumes finitos; fronteiras móveis; conservação de espaço