Abstract: An electric heater for a fluid comprises a plurality of electrically conductive tubes arranged in a bundle for resistive heating having an axial extension, electrical connectors arranged between the tubes. The electric heater is configured for the fluid to flow through the bundle in direct contact with inner and outer surfaces of the tubes. Each of the tubes has an outer diameter within a range of 6-40 mm and an outer diameter to wall thickness ratio within a range of 5-15 or within a range of 7-12. A ratio between a total cross-sectional surface area in between the tubes and a total cross-sectional area inside the tubes lies within a range of ?10% to +30% or within a range of ?5% to +25% of a ratio between the outer and inner diameters of one tube.

Abstract: An electric heater for a fluid comprises a plurality of electrically conductive tubes arranged in a bundle for resistive heating having an axial extension, electrical connectors arranged between the tubes. The electric heater is configured for the fluid to flow through the bundle in direct contact with inner and outer surfaces of the tubes. Each of the tubes has an outer diameter within a range of 6-40 mm and an outer diameter to wall thickness ratio within a range of 5-15 or within a range of 7-12. A ratio between a total cross-sectional surface area in between the tubes and a total cross-sectional area inside the tubes lies within a range of ?10% to +30% or within a range of ?5% to +25% of a ratio between the outer and inner diameters of one tube.