Prediction of Heat Transfer in Reciprocating Antifreeze Flow Through a Porous Filter

摘要

Heat transfer to an oscillating vertical annular flow through a porous material is investigated experimentally. The flow media includes stationary stainless steel wool filter and monoethy-lene glycol (which is known as a coolant, heat transfer agent or antifreeze) as the working fluid. Reciprocating forced oscillations are imposed on the single-phase monoethylene glycol via a frequency controlled dc motor and a piston-cylinder device where displacement amplitude is kept constant Electrical heater occupies the inner section of the vertical annulus which provides constant heat flux. The analysis is carried out for two different heat fluxes and for five different frequencies and the effect of these on the temperature field and resultant heat convection coefficient are studied. A cycle and space averaged Nusselt number correlation is fitted which is useful in predicting rate of heat transfer from oscillating flows through highly porous and permeable solid media (such as in filters) at low actuation frequencies and at low heat flux rates. Developed correlation equation is validated for monoethylene glycol, glycerol and water. Oscillatory antifreeze flow in porous filter is proposed as a remedy for the limited thermal conductivity of the water-monoethylene glycol solution. These results also have possible applications in fluid pumping technology in converting of low-grade thermal energy to pumping work.