Experimental investigation of an ion-drag pump-assisted capillary loop

Abstract

An ion-drag pump was constructed and calibrated to determine the available pumping pressure as a function of input voltage for various working fluids. The experimental results were then compared with an analytical model and found to predict the ion-drag pump performance to within ±15%. Using this information, an analytical model capable of predicting the performance enhancement of an ion-drag pump-assisted capillary loop was also developed and compared with the values obtained from experimental tests conducted on a thermal test loop. Although the analytical model slightly overpredicted the performance enhancement resulting from the ion-drag pump, the predicted trends were similar to those obtained from the experimental program. These trends included decreased thermal test loop performance with increased evaporator/condenser elevation difference, increased performance (due to increased operating temperature), and an increase in performance ranging from 20 to 100%, due to the addition of a two-stage ion-drag pump. The performance enhancement of the thermal test loop was verified at various operating temperatures and evaporator/condenser elevation differences. Nomenclature d = diameter g = gravitational acceleration h = evaporator/condenser height difference / = current L = length Me = merit number P — pressure Q = heat transport capacity r = radius V = voltage 8 = emitter/collector electrode spacing e = dielectric constant 77 = efficiency @ = wetting angle A = latent heat jit = viscosity v = volumetric flow rate p = density a = surface tension (/> = angle of inclination Subscripts c = capillary EHD = electrohydrody namic g = gravitational / = liquid v = vapor 0 = charge