Experimental research of heterogeneous nuclei in superheated steam

¹ Czech Technical University in Prague, Department of Energy Engineering, Technická 4, Prague 6, 166 07, Czech Republic
² Institute of Thermomechanics of the CAS, v.v.i., Dolejškova 5, 182 00 Prague 8, Czech Republic

^a Corresponding author: ondrej.bartos@fs.cvut.cz

Published online: 28 March 2016

Abstract

A mobile steam expansion chamber has been developed to investigate experimentally homogeneous and heterogeneous nucleation processes in steam, both in the laboratory and at power plants using the steam withdrawn from the steam turbine. The purpose of the device is to provide new insight into the physics of nonequilibrium wet steam formation, which is one of the factors limiting the efficiency and reliability of steam turbines. The expanded steam or a mixture of steam with a non-condensable gas rapidly expands in the expansion chamber. Due to adiabatic cooling, the temperature drops below the dew point of the steam at a given pressure. When reaching a sufficiently high supersaturation, droplets are nucleated. By tuning the supersaturation in the so-called nucleation pulse, particles of various size ranges can be activated. This fact is used in the present study to measure the aerosol particles present in the air. Homogeneous nucleation was negligible in this case. The experiment demonstrates the functionality of the device, data acquisition system and data evaluation methods.