Structure of exhaust pipe for exhaust heat recovery

A structure of an exhaust pipe for exhaust heat recovery, which heats coolant with heat of exhaust gas, the structure comprising:

• a housing connected to the exhaust pipe so that the exhaust gas flows from a front side to a rear side, and including a first nipple through which the coolant flows in, and a second nipple through which the coolant flows out;
• and
• a plurality of heat transfer pipes having different diameters, wherein the heat transfer pipes are mounted inside the housing and coolant paths that coolant flows through are formed between the heat transfer pipes and the first nipple and the second nipple are opened inside the housing and the coolant paths,
• wherein exhaust gas paths through which the exhaust gas flows are formed between the neighboring coolant paths so as to form layers, and the first nipple is disposed at a rear side of the second nipple,
• wherein the first nipple is formed at a lower end of the housing, and the second nipple is formed at an upper end of the housing,
• wherein each heat transfer pipe has wrinkle portions which protrude from a surface of each heat transfer pipe;
• and
• wherein concave portions and convex portions formed on the wrinkle portions comprise:
• a first wrinkle portion formed to have a shape in which one side in a longitudinal direction of the exhaust pipe is biased toward the front side and another side is biased toward the rear side of the exhaust gas;
• and
• a second wrinkle portion connected to the first wrinkle portion and formed to have a shape biased in a direction opposite to the biased direction of the first wrinkle portion so that the shape of the first wrinkle portion and the shape of the second wrinkle portion are symmetric with each other with respect to a longitudinal axis of the exhaust pipe.