Heater and water dispenser

The invention relates to the technical field of water dispensers, and provides a heater and a water dispenser. The jet assembly is provided with a jet cavity, a water inlet and a plurality of jet holes, the water inlet and the jet holes are communicated with the jet cavity, a water passing gap is formed between the outer wall face of the jet cavity and the inner wall face of the heating pipe, and the water inlet faces the liquid inlet port. The ratio of the total area of the jet flow holes to the area of the inner wall of the jet flow cavity is 0.94%-78.35%, and the coverage rate of the jet flow cavity and the heating area of the heating pipe in the axial direction of the heating pipe is 85%-95%. Liquid flow directly exchanges heat with the heating pipe, the heat exchange efficiency of the liquid flow is improved, meanwhile, the liquid flow can be efficiently heated by limiting the hole proportion of the jet flow holes in the jet flow cavities and the coverage rate of the multiple jet flow cavities and the heating area, and the heating efficiency is improved. And meanwhile, the heat exchange coefficient, the Nusselt number and the pressure drop of the heater can be in a better range, so that the pressure drop of the jet flow cavity and the heat exchange efficiency between the liquid flow and the heating wall surface are balanced.