1. Field of the Invention
The present invention relates to a heat exchanger for exhaust heat recovery of a vehicle. More particularly, the present invention relates to an exhaust heat recovery apparatus for a vehicle in which a coolant and a lubricant are subjected to heat exchange for exhaust heat.
2. Description of Related Art
In general, a heat exchanger in a vehicle recovers exhaust heat by performing heat exchange between an exhaust gas and a coolant in such a manner as to lower the temperature of a high-temperature exhaust gas while increasing the temperature of a low-temperature coolant.
The heat, recovered through the heat exchanger, is transmitted to a part of a vehicle requiring heat, and used for the heating of a lubricant, the fast warming up of an engine, heating, and the like.
The heat exchanger is provided with a heat exchange part in which heat exchange with a coolant takes place. An exhaust gas exchanges its heat with the coolant while flowing through the heat exchange part. In a case where heat recovery is unnecessary, the heat exchanger changes a flow path such that the exhaust gas bypasses the heat exchange part.
For example, as for a structure for heating a lubricant by recovering the exhaust heat, the exhaust heat is made to pass through the heat exchange part. After the lubricant is heated to an appropriate temperature, the exhaust gas is made to bypass the heat exchange part to thus prevent a further increase in the temperature of the lubricant.
That is, at a low temperature or in initial starting, the high-temperature exhaust heat is supplied to the heat exchange part for the exchange of heat with the coolant. The coolant having increased in temperature increases the temperature of the lubricant. Since the lubricant has a high level of viscosity at a low temperature, the lubricant increases friction when supplied to a transmission or a work part of an engine. The lubricant heated by the coolant can reduce friction of the transmission, and the like.
The lubricant, when excessively heated, is degenerated and thus fails to properly perform lubrication. For this reason, at a high temperature or in acceleration, the exhaust gas is made to bypass the heat exchange part. In this case since heat exchange does not occur between the exhaust gas and the coolant, the coolant is maintained at a low temperature and the lubricant can be cooled by the low-temperature coolant.
In such a heat exchanger according to the conventional art, a single passage through which the coolant flows is disposed at a region in which the exhaust gas passes, and a tube through which the lubricant is distributed is installed within the passage to thus form the heat exchange part.
Accordingly, at the low temperature or in the initial starting of a vehicle, heat exchange between the exhaust gas and the coolant occurs in the region where the exhaust gas passes so as to increase the temperature of the coolant. The coolant can increase the temperature of the lubricant. The lubricant the temperature of which has been increased in the above manner contributes to enhancing fuel efficiency by reducing friction of the transmission, and the like.
However, since the heat exchanger according to the conventional art has the heat exchange part formed simply by installing a tube through which the lubricant is distributed within a single coolant path, the contact area and contact time of the coolant path with respect to the exhaust gas are insufficient. This may deteriorate heat-exchange performance and slow down the temperature increase of the lubricant, resulting in deterioration of fuel efficiency.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.