Steam flows in concrete cracks: Pressure differentials and flow rates

Experiments in which heated nitrogen/steam mixtures are passed through model cracks in concrete while monitoring the temperature and the pressure at the entry and exit of the crack provide links between the mass flow rate and the pressure difference across the crack. Cooling of the nitrogen/steam mixture by the concrete, and particularly the formation of condensation, alter the relationship between the pressure difference and the flow rate. At low flow rates, the nitrogen/steam mixture is cooled to the temperature of the concrete and the flow is practically the same as for the cold nitrogen portion. At higher flow rates, the pressure differences approach and can rise above the values they would have if the concrete were heated to the same temperature as the ni-trogen/steam mixture.