Heat medium heating apparatus and vehicular air-conditioning system including the same

A vehicular air-conditioning system comprising:

• a heat medium heating apparatus;
• a heat radiator placed in an air flow passage through which a heat medium heated by the heat medium heating apparatus circulates, wherein the heat medium heating apparatus comprising:
• a plurality of flat heat exchanger tubes each including an inlet header part, a flat tube part, and an outlet header part, the flat heat exchanger tubes each allowing a heat medium to flow thereinto through the inlet header part, circulate through the flat tube part, and then flow to an outside thereof through the outlet header part;
• PTC heaters that are respectively incorporated between the flat tube parts of the flat heat exchanger tubes stacked on each other;
• a heat exchanger holding member that presses the flat heat exchanger tubes and the PTC heaters alternately stacked on each other, from one side of the flat heat exchanger tubes toward an inner surface of a casing, to thereby bring the flat heat exchanger tubes and the PTC heaters into close contact with each other;
• and
• a control board that has a surface on which a control circuit is mounted, the control circuit including a heat-generating electrical component that controls the PTC heaters, wherein
• the control board includes a heat penetration part that is formed so as to pass through the control board correspondingly to a mounting position of the heat-generating electrical component, the heat penetration part being made of a highly thermally conductive material, and
• the heat-generating electrical component is mounted so as to be cooled via the heat penetration part.