HEAT-TRANSFER MODELING OF A CYLINDRICAL ER CATCH

In electro-rheological (ER) devices the control of temperature is ofte n of paramount importance. For a device through which the ER fluid is not able to flow continuously to and from a reservoir, where it may be cooled, this can be a problem. Such a situation occurs in the ER catc h. The heat generated there will predominantly be dissipated from the outer surface of the drive/input. The rate of heat transfer is thus pr incipally a function of the speed and area of that surface and the tem peratures of the ER fluid and atmosphere. Since these factors reflect on the levels of electro-stress, current requirement and viscosity of the ER fluid, an opportunity exists for optimisation of catch performa nce. The paper shows the results of an investigation into the effects on the cooling/heating problem of varying the radii of the clutch roto rs, their relative rotational speed and inter-electrode spacing. Equil ibrium fluid temperatures are confirmed by experimental evidence. The effects of heat generation in run up to speed and clutch locked period s, (through electro viscous drag and dielectric loading respectively) are quantified and compared with the case of a contemporary ER fluid i n a cylindrical catch on zero volts idling. At any given operating con dition, uniform temperature, viscosity and constant electro stress are assumed throughout the fluid.