Fluid heating device for engine

A fluid heating device for an engine comprising:

• a holder:
• a heater housed in the holder;
• and
• a radiator pipe inserted into the holder,
• wherein the radiator pipe is formed by an outer pipe and at least one inner pipe in the outer pipe, heat generated by the heater is transferred to the outer pipe and the inner pipe, a fluid passing inside and outside the inner pipe in the outer pipe is heated by heat radiation from the outer pipe and the inner pipe,
• wherein an outwardly-facing surface of the inner pipe is in contact with an inwardly-facing surface of the outer pipe so that the heat of the heater is transferred to the inner pipe via the outer pipe, and
• wherein the holder and the outer pipe respectively comprise a single straight pipe extending straight over an entire length of the holder and the outer pipe,
• wherein the outer pipe extends over the entire length of the holder in an axial direction of the holder and has a flat outer-pipe wall portion with a flat outwardly-facing outer-pipe surface and a flat inwardly-facing outer pipe surface, the heater is flat in form, partially placed at a respective central part of the holder and the outer pipe in a respective axial direction of the holder and the outer pipe, and placed along the flat outwardly-facing outer-pipe surface, and the inner pipe is in contact with the flat inwardly-facing outer-pipe surface,
• and wherein an outwardly-facing surface at the central part of the outer pipe in the axial direction of the outer pipe comprises a heat receiving face along which the heater extends and a fitting face fitted into the holder, the heat receiving face is formed at a part of an entire circumference of the outwardly-facing surface at the central part of the outer pipe in the axial direction of the outer pipe, and the fitting face is formed at an entire rest part of the entire circumference of the outwardly-facing surface at the central part of the outer pipe in the axial direction of the outer pipe.