Vehicle heater

A vehicle heater comprising:

• a burner device comprising a combustion chamber circumferential wall circumferentially enclosing a combustion chamber;
• a flame tube with a first flame tube end adjoining the combustion chamber circumferential wall or forming at least a part of the combustion chamber circumferential wall and a second flame tube end open in a direction of a flame tube longitudinal axis for the discharge of combustion waste gas;
• a heat exchanger housing comprising a heat exchanger housing circumferential wall circumferentially enclosing the flame tube on a flame tube outside and a heat exchanger housing bottom located axially opposite the second flame tube end, a waste gas backflow space with an inlet area at the second flame tube end and with an outlet area adjacent to the first flame tube end being formed between an outer side of the flame tube and an inner side of the heat exchanger housing circumferential wall, wherein an inner dimension of the heat exchanger housing circumferential wall increases in a direction from the inlet area of the waste gas backflow space to the outlet area of the waste gas backflow space and an outer dimension of the flame tube increases in a direction from the second flame tube end to the first flame tube end,
• wherein, on the inner side of the heat exchanger housing circumferential wall, a plurality of heat transfer ribs extending in the direction of the flame tube longitudinal axis and extending radially inwards towards the outer side of the flame tube, are each provided with an apex located opposite the outer side of the flame tube,
• wherein the inner dimension of the heat exchanger housing circumferential wall increases in a length area thereof, which encloses the flame tube, and the outer dimension of the flame tube increases at an essentially equal rate in the direction from the second flame tube end to the first flame tube end for providing a radial distance between the outer side of the flame tube and the inner side of the heat exchanger housing circumferential wall that is essentially constant in the direction of the flame tube longitudinal axis, such that the radial distance is essentially constant, between the second flame tube end and the first flame tube end, between the outer side of the flame tube and the apices of the heat transfer ribs, and is essentially constant, between the second flame tube end and the first flame tube end, between the outer side of the flame tube and wall areas of the heat exchanger housing circumferential wall located between adjacent heat transfer ribs in a circumferential direction at a greater distance to the outer side of the flame tube than the apices of the heat transfer ribs.