MICRO-TUBE OIL COOLING ASSEMBLY
TECHNICAL FIELD
The present subject matter, in general, relates to an oil cooling assembly for engines and in particular, relates to a micro-tube based oil cooling assembly for engines.
BACKGROUND
The main function of oil cooling assembly is the use of engine oil as a coolant, typically to remove surplus heat from engines, more specifically, internal combustion engines. The hot engine transfers heat to the oil which then usually passes through a heat-exchanger known as oil cooling assembly. The cooled oil flows back into the hot object to cool it continuously. For an engine cooling system a compact, lightweight, durable, high thermal performance and robust oil cooling assembly is vital. The growing demand for efficient and light weight oil cooler with variable core sizes under very short development time is a big challenge.
In conventional plate and fin oil cooler used in engine cooling system, the general trend was to increase or decrease the number of plates as per performance targets as plate length is fixed. To modify plate length complete new tooling was required. In conventional plate and fin design, multi louvered fin design is fixed for plate and cannot be altered. Hence, flexible core options for oil coolers were not available.
Therefore, there is a long felt need for an oil cooling assembly for engines which overcomes the aforementioned and other challenges.

SUMMARY
The present subject matter provides a new concept of flexible manufacturing and performance of an oil cooling assembly used in transmission, engine, gear box and hydraulic applications. Oil in an automobile, lubricates and helps in regulating temperature of moving components of an engine or transmission. Thus, maintaining optimum oil temperature is important not only to keep the oil at its efficient lubricating state, but also to aid the radiator in keeping the motor cool.
The present subject matter aims at replacing conventional plate and fin oil cooler used in engine cooling system. The present subject matter allows flexible core options with superior performance specifications to that of the conventional plate and fin oil cooler. Less effort is required towards entire design and development of the oil cooling assembly. The use of micro-tubes, instead of plates provides a great flexibility in core options. Different fin options having variable fin height can be used, unlike conventional design where fin height was fixed for a specific plate. Use of extruded micro tube and seam welded single piece header eliminates numerous brazing joints present in conventional plate and fin oil cooler. Unique profile of extruded micro tube caters to superior thermal performance. The cost of product development is reduced to a great extent. Hence it leads to a highly economic design.
In an embodiment, the present subject matter provides an oil cooling assembly having enhanced flexibility of the core.
The present invention relates to an oil cooling assembly for automobiles. The oil cooling assembly comprises a plurality of micro-tubes stacked parallely in a horizontal direction. At least two single piece headers are attached vertically to the ends of the plurality of micro-tubes.

Further, at least one multi-louvered fin is placed between each pair of the micro-tubes in proximity to the single piece headers.
In an embodiment, the micro-tubes are formed through extrusion process.
In another embodiment, the micro-tubes are joined to the header by the means of furnace brazing.
In yet another embodiment, the multi-louvered fins are placed between each of the pair of the micro-tubes in proximity to the single piece headers in order to enhance heat transfer efficiency.
In yet another embodiment, the extruded micro-tubes make the oil cooling assembly leak-proof.
In yet another embodiment, maintenance and replacement of parts of the oil cooling assembly is simple.
In yet another embodiment, use of micro-tubes makes the oil cooling assembly lightweight.
In yet another embodiment, use of extruded micro-tubes and single piece headers provide flexibility in relation to the number of micro-tubes, length of micro-tubes and number of multi-louvered fins.

BRIEF DESCRIPTION OF DRAWINGS
The foregoing and further objects, features and advantages of the present subject matter will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements.
It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter, and are therefore, not to be considered for limiting of its scope, for the subject matter may admit to other equally effective embodiments.
Figure 1 illustrates a conventional aluminium plate and fin oil cooling assembly used in engine cooling system in accordance with an embodiment of the present subject matter.
Figure 2 illustrates a sectional view of a plate (conventional plate) of the conventional oil cooling assembly with internal turbulator showing detailed view of its internal structure.
Figure 3 shows a perspective view of a micro-tube oil cooling assembly, illustrating extruded micro tubes and seam welded single piece header.
Figure 4 illustrates a sectional view of a micro tube internal structure used in the micro-tube oil cooling assembly in accordance with an embodiment of the present subject matter.
Figure 5 illustrates a sectional view of a micro-tube oil cooling assembly in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
The present subject matter relates to an oil cooling assembly for internal combustion engines. The conventional plate and fin oil coolers consist of plate packed with internal turbulator. The general trend was to add or remove plate as per the heat rejection requirements.

The conventional oil coolers lack flexibility of variable core options whereas the micro-tube oil cooling assembly of present embodiment includes a very economic, efficient and flexible design. In conventional design the plate length was fixed and cannot be altered as per requirement, making it less flexible. In the convectional plate and fin oil Cooler the fin design was fixed for a certain plate. Further, in conventional plate and fin oil cooler, depth cannot be altered and in order to alter depth complete new tooling would be required.
As shown in Figure 1, the conventional oil cooling assembly 100 or plate and fin type cooler includes a plurality of flat plates 102 and multi-louvered fins 104. The flat plates 102 are stacked one over another and their ends are joined through brazed joints 106. Figure 2 illustrates a sectional view of a plate (conventional plate) of the conventional oil cooling assembly 100 with an internal turbulator 106. A detailed view of internal structure lying between the two parallel plates is shown; said structure includes a pair of flat plates joined together through brazing joint and the internal turbulator 106 which helps in turning a laminar flow into a turbulent flow.
The micro-tube oil cooling assembly according to present subject matter is very flexible and can have multiple core size options. The core size can be defined as the following header to header (tube length) * fin to fin (height) * depth. The tube length can be altered as per available space. Core height can also be altered as per requirement. Different fin combinations can also be used for selected micro-tubes. The present subject matter allows depth variation along the air flow direction, fin and micro tube depth can be varied as per space constrains. Use of extruded micro tube instead of plate and turbulator design, eliminates the brazing joints (as shown in Figure 1 and 2) present between the plates facilitating a leak proof design. Use of seam welded single piece header in place of plates, eliminates the numerous brazing joints (shown in Figure 1 and 2). Single piece seam welded header caters to a leak proof design. Unique profile of extruded

micro tube with curved ribs delays boundary layer development and create additional surface area to enhance the transfer of heat from the oil during operation of the heat exchanger.
An oil cooler is generally used to cool down the engine oil temperature to a certain limit. By maintaining the oil temperature in a specific range, engine can be operated in optimum condition. As the engine oil flows from the micro-tubes and air passes across the fins, so it acts like a cross flow heat exchanger. Oil flows inside the micro-tubes at higher temperature, and heat transfer happens in convection-conduction-convection process between tube and extended fins. Oil temperature reduces at the exit of the oil cooler with the present heat transfer process before entering into the engine. Heat transfer rate or temperature drop across oil cooler is dependent on air flow rate, oil flow rate, air and oil inlet temperatures, oil properties and geometric specifications of micro-tube and Fins. As shown in figure 3, oil enters in single piece header 204 first and then it passes through micro-tubes 202. After that heat is carried away by air, which is in contact of outer surface of micro-tubes 202 and fins 206 as well.
Figure 3 illustrates a micro-tube oil cooling assembly 200, comprising a plurality of micro-tubes 202, single piece headers 204 and multi-louvered fins 206. Each of the plurality of micro-tubes 202 is stacked horizontally parallel to each other between the two single piece headers 204. Ends of each of the micro-tubes 202 are furnace brazed with the respective single piece headers 204. Further, the multi-louvered fins 206 are installed between each pair of the micro-tubes 202 proximal to the single piece headers 204.
In this assembly, hot oil from engine enters into oil cooler through inlet pipe, succeeds to single piece header. After single piece header, oil flows from micro tubes, succeeded by another

single piece header and exits from outlet pipe. Brackets are used for the purpose of mounting oil cooler on vehicle.
Referring Figure 4, a sectional view of a micro-tube 202 showing its internal structure in accordance with an embodiment of the present subject matter is illustrated. Said figure shows internal flow profile of the micro-tube 202. The micro-tubes 202 are extruded and then installed with the single piece header 204. As shown in figure, the micro-tubes 204 include a plurality of ribs 208. Further, extruded micro-tubes eliminate the brazed joints (in case of conventional oil cooling assembly) and hence make the micro-tube oil cooling assembly leak-proof. Figure 5 illustrates a sectional view of the micro-tube oil cooling assembly 200 in accordance with an embodiment of the present subject matter.
According to a preferred embodiment, hydraulic diameter of the micro-tube lies between 1.2 mm to 3.5 mm. As diameters below 1.2 mm, may lead to very high internal oil pressure drop.
In an embodiment, the micro-tube construction includes ribs (as shown in Figure 4) which increases the surface area and also disturbs the boundary layer leading to increased heat transfer coefficient in oil side. The pressure shoots up above normal pressure during the warm-up periods when the oil is substantially congealed at lower temperatures. Embodiment extruded tube profile helps in overcoming this scenario. Seam welded single piece header with swage down extruded micro tube enable controlling the insertion depth and giving rise to a leak proof oil cooling assembly. The same seam welded single piece header can be ribbed for severe burst pressure requirements if the application demands.
Automobile oil coolers are required to be lightweight and compact for a better performance of the vehicle. This present subject matter provides an efficient way to reduce the oil cooling

assembly’s weight by almost 30 to 40 % due to use of micro-tubes in place of plate and turbulator design.
The micro-tube oil cooling assembly can be used in a variety of applications and is not restricted only to engines. The present subject matter provides a user to manufacture micro-tube oil cooling assembly of various core sizes as per space constrain with superior performances specification and reduced weight solution.
In an embodiment, the micro-tube oil cooling assembly provides 10 to 15 % improved heat rejection, with 10 to 12 % reduced air side restriction and better uniformity on the oil side. The present micro-tube oil cooling assembly is also light in weight providing almost 30 to 40 % weight reduction from the conventional plate and fin design. It also eliminates plentiful brazing joints present in conventional plate and fin design facilitating leak proof oil cooling assembly. In case of conventional design, entire hose pipe assembly needs to be replaced where as in the invention parts can be served at component level. It would bring down the cost of replacement of parts in the field/Service, providing best serviceability. Further, the present micro-tube oil cooling assembly is cost effective solution, as the tooling cost involved will come down and lesser number of parts involved in oil cooler assembly as compared to the conventional design also caters in cost reduction.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore,

contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

We Claim
1. An oil cooling assembly for automobiles, the oil cooling assembly comprising:
a plurality of micro-tubes stacked parallely in a horizontal direction;
at least one multi-louvered fin placed between each pair of the micro-tubes in
proximity to the single piece headers; and
at least two single piece headers attached vertically to the ends of the plurality of
micro-tubes.
2. The oil cooling assembly as claimed in claim 1, wherein the micro-tubes are formed through extrusion process.
3. The oil cooling assembly as claimed in claim 1, wherein the micro-tubes are joined to the header by the means of furnace brazing.
4. The oil cooling assembly as claimed in claim 1, wherein the multi-louvered fins are placed between each of the pair of the micro-tubes in proximity to the single piece headers in order to enhance heat transfer efficiency.
5. The oil cooling assembly as claimed in claims 1 and 2, wherein the extruded micro-tubes make the oil cooling assembly leak-proof
6. The oil cooling assembly as claimed in claims 1, wherein maintenance and replacement of parts of the assembly is simple.
7. The oil cooling assembly as claimed in claims 1 and 2, wherein use of micro-tubes makes the oil cooling assembly lightweight.
8. The oil cooling assembly as claimed in claims 1 and 2, wherein use of extruded micro-tubes and single piece headers provide flexibility in relation to the number of micro-tubes, length of micro-tubes and number of multi-louvered fins.