Abstract: The cross-sectional flow area of a fluid duct and/or the flow direction of a fluid flow out of a fluid duct or air outlet is controlled by a control drive with two expansion drives positioned either in axial alignment with each other or with their longitudinal axis extending preferably in parallel to each other. The two drives are thermally separated from each other so that one drive is exposed to the temperature of one fluid while the other drive is exposed to the temperature of another fluid, whereby these fluids may be the same fluid or different fluids or mixture of different fluids. Each expansion drive contains a temperature responsive expansion material so that the power for operating the flow controller is derived solely from the temperature difference between the two fluids and hence any auxiliary energy becomes unnecessary for the control purpose.

Abstract: An upwelling-air distributor for air-conditioning systems. It comprises two concentric, air-permeable cylinders, an outer cylinder (1) and an inner cylinder (2). The cylinders accommodate one or more diaphragms (10 and 11) in the form of flat rings. The distributor is connected to the ventilating system by an air intake (3) at one end. A pipe (6) is accommodated inside the inner cylinder. The pipe is provided with a butterfly valve (7) and is open at the end remote from the air intake. Air can flow through the pipe except when the valve is closed.