Heat Transfer Modelling of a Cylindrical Er Catch

Abstract

In electro-rheological (ER) devices the control of temperature is often 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 catch. The heat generated there will predominantly be dissipated from the outer surface of the drive/input. The rate of heat transfer is thus principally a function of the speed and area of that surface and the temperatures 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 performance. The paper shows the results of an investigation into the effects on the cooling/heating problem of varying the radii of the clutch rotors, their relative rotational speed and inter-electrode spacing. Equilibrium fluid temperatures are confirmed by experimental evidence. The effects of heat generation in run up to speed and clutch locked periods, (through electro viscous drag and dielectric loading respectively) are quantified and compared with the case of a contemporary ER fluid in a cylindrical catch on zero volts idling. At any given operating condition, uniform temperature, viscosity and constant electro stress are assumed throughout the fluid.

<title>Dynamic modeling and performance of a high-speed electrorheological traversing mechanism</title>

“…The electro-rheological shear stress 're varies linearly with the shear rate and is given by rereo+1J (3) where reo the electro-rheological shear stress at = 0, k is the shear stress vs shear rate gradient, and the shear rates ;•oA 1fld J' Ofl the inner and outer surfaces of the output rotor are assumed to be given by (t2-(L))4 (t2_w)L ToA h0 and h4= 2 (4) where £2 is the angular velocity of the input rotors, h0 and h1 are the radial gaps between the input and output rotors for the outer and inner gaps respectively, and w is the angular velocity ofthe output rotors at the general instant in time t. The viscous torque TOA on the output rotor is given by TOA YoA(7boA,o)7 +pyrd1i,,)- (5) where ,i is the fluid viscosity, ivo and 1 e the viscously active lengths on the outer and inner surfaces of the output rotor respectively. The electro-rheological shear stress 're varies linearly with the shear rate and is given by rereo+1J (3) where reo the electro-rheological shear stress at = 0, k is the shear stress vs shear rate gradient, and the shear rates ;•oA 1fld J' Ofl the inner and outer surfaces of the output rotor are assumed to be given by (t2-(L))4 (t2_w)L ToA h0 and h4= 2 (4) where £2 is the angular velocity of the input rotors, h0 and h1 are the radial gaps between the input and output rotors for the outer and inner gaps respectively, and w is the angular velocity ofthe output rotors at the general instant in time t. The viscous torque TOA on the output rotor is given by TOA YoA(7boA,o)7 +pyrd1i,,)- (5) where ,i is the fluid viscosity, ivo and 1 e the viscously active lengths on the outer and inner surfaces of the output rotor respectively.…”

Heat Transfer From an Esf Radial Plate Clutch Surface

“…In a previous work [2], the heat transfer from the surface of a concentric clutch was modeled and subsequent developments [3] have validated the technique. This model was latterly tested by running the outer rotor at speed whilst holding the inner stationary and measuring the temperature on the outer surface by a remote infra red thermometer.…”

Quasi-Static Heat Transfer in an Experimental Device with a Radial Electro-Structured Fluid Clutch

“…Originality of the above approach and solution relative to previous ones e.g., in (Smyth et al, 1994;Nosek, 1998;Kirk, 1999) consists in the following 5 items:…”

“…1. The fluid is not taken as an isothermal continuum that has been frequently used up to now (Smyth et al, 1994;Kirk,1999;Nosek, 1998). Due to this, in addition to two Equations ( 6) and ( 9) describing conduction through the rotating disc and convection into air, also the 3rd Equation ( 5 (Nosek, 1998), in a power regression form ( 13), but in the form ( 14)-( 16).…”

“…Valuable source of information about various heat transfer problems but not in connection with ESF clutches can be found in the books (Wong, 1977;Welty et al, 1984). Heat transfer in a cylindrical ESF clutch has been examined by Smyth et al (1994), but, in fact, only in quasi-static state and without electro-rheological effect. On the contrary, dynamics of a radial ESF with electrorheological effect but without heat transfer has been investigated by Whittle et al (1997).…”