Abstract: Fluid flows through a conduit. To measure flow speed the fluid is heated at a heating location in the conduit with a time-dependent heating strength. A speed of sound in fluid flowing in the conduit is measured at a plurality of sensing locations downstream from said heating location. The flow speed of the fluid is determined from a delay with which the time dependence is detected in the sound speeds measured at said sensing locations. In an embodiment a frequency of the variation of heating strength that is used to determine the flow speed is selected automatically dependent on the flow speed and/or other circumstances.

Abstract: An additive fabrication apparatus is provided comprising a movable foil guiding stage (180) having a contact face (181) and comprising on opposite sides of the contact face a pair of upper and lower foil guiding elements (190, 191), the lower foil guiding element (190) defining a foil height position (H0) distanced from the contact face (181), for guiding a foil (6) including a liquid layer (30) to or from the contact face to contact a tangible object (50) by movement of the foil guiding stage along the tangible object while keeping the foil stationary relative to the object (50). An energy source (90) is arranged for at least partially solidifying at least part of an intersection pattern in the liquid layer arranged on the foil and in contact with the tangible object.

Abstract: An evaporator for evaporating a liquid containing fluid, having an inlet and an outlet connected to an evaporation volume with an internal structure, the inlet and the outlet defining a main flow path there between and the cross-section of the evaporation volume is substantially constant along the main flow path is described. A method method for evaporating a liquid containing fluid by providing an evaporator supplying a liquid containing feed stream to the inlet; exerting heat; choosing the operating conditions so that an annular flow is created.

Abstract: Fluid flows through a conduit. To measure flow speed the fluid is heated at a heating location in the conduit with a time-dependent heating strength. A speed of sound in fluid flowing in the conduit is measured at a plurality of sensing locations downstream from said heating location. The flow speed of the fluid is determined from a delay with which the time dependence is detected in the sound speeds measured at said sensing locations. In an embodiment a frequency of the variation of heating strength that is used to determine the flow speed is selected automatically dependent on the flow speed and/or other circumstances.

Abstract: The invention relates to an evaporator for evaporating a liquid containing fluid, having an inlet and an outlet connected to a evaporation volume, the inlet and the outlet defining a main flow path there between, wherein the evaporation volume is equipped with an internal structure and the cross-section of the evaporation volume is substantially constant along the main flow path. The invention further relates to a method for evaporating a liquid containing fluid comprising the steps of: providing an evaporator according to the invention; supplying a liquid containing feed stream to the inlet of the evaporator; exerting heat to the evaporator volume; choosing the operating conditions of the evaporator thus that an annular flow is created within the evaporator volume.