Abstract: A hot water appliance 10 comprises a water tank 12 provided with a water tank wall 14. The hot water appliance 10 further comprises a vacuum vessel 20 which encloses a vacuum space V. The water tank 12 is wholly included in the vacuum space, and the whole water tank wall 14 is bounded by vacuum. The vacuum vessel 20 is provided with a vacuum vessel wall 22 which consists of a number of vacuum vessel wall parts that are gastightly connected with each other by welding or soldering. Further, the hot water appliance 10 comprises at least one functional pipe 100, 200, 300, 400, 500 which extends through the water tank wall 14 and is gastightly connected with the water tank wall 14 at the location of a water tank wall connection 18. The functional pipe 100, 200, 300, 400, 500 also extends through the vacuum vessel wall 22 and is gastightly connected with the vacuum vessel wall 22 at the location of a vacuum vessel wall connection 24.

Abstract: One example discloses a fluid flow device, including: a drop chamber, having an interior, a fluid input, and a fluid output; a drop detector coupled to the drop chamber and configured to detect a fluid drop at the fluid input; a pressure sensor configured to monitor a pressure in the interior of the drop chamber; and a flow rate device configured to determine a fluid flow rate based on a number of fluid drops detected over a time period, and the pressure in the interior of the drop chamber.

Abstract: One example discloses a fluid flow device, including: a drop chamber, having an interior, a fluid input, and a fluid output; a drop detector coupled to the drop chamber and configured to detect a fluid drop at the fluid input; a pressure sensor configured to monitor a pressure in the interior of the drop chamber; and a flow rate device configured to determine a fluid flow rate based on a number of fluid drops detected over a time period, and the pressure in the interior of the drop chamber.