DESC:MULTI ROW RADIATOR
Field of the invention
Conventional multi row radiators are having plain flat tubes and multi-louvered symmetric outer triangular fins. Conventional multi row radiators such as CF 23-2, CF 76-2 with two rows of 36 mm thickness, CF 27-2, CF 75-2 with two rows of 48 mm thickness, CF 75-3 with 3 rows of 74 mm thickness, CF 75-4 with 4 rows of 100 mm thickness, where more tube thickness and width makes radiator bulky and higher in weight. Conventional multi row radiators are having lower tube side heat transfer co-efficient, which results in lower heat transfer performance. Also, multi-louvered symmetric fins of conventional radiators generates higher cooling air pressure drop. So, a major draw-back of the conventional design is that the radiator requires higher diameter and higher fan power to achieve good performance.
Accordingly, there is a need of advancement in multi row radiators that overcomes the above mentioned drawbacks of the prior art.
Object of the invention
An object of the present invention is to obtain higher heat transfer rate in almost same core thickness/ volume.
Another object of the present invention is to reduce the weight and size of multi- row radiator, which enables better inventory management.
Another object of the present invention is to lower the cooling air side pressure drop.
Another object of the present invention is to meet BS 6 automotive regulation standard.

Summary of the invention
The present invention discloses a multi row radiator having enhanced thermal performance compared to the existing conventional multi row radiators with plain flat tubes. The multi row radiator is having two header tanks fitted on two opposite faces of a radiator core. The first header tank is fitted with a coolant inlet and the second header tank is fitted with a coolant outlet. The radiator core is having a core support fitted with two header plates on two opposite faces thereof. The header plates are provided with multiple rows of an array of parallel slots having a gap of 3 to 5 mm between two slots of the adjacent rows, wherein the core support is provided with cut outs to compensate for thermal expansion and avoid breakage due to higher thermal stresses. In an embodiment, the number of rows provided on two header plates ranges from two to four. In another embodiment, the core thickness ranges from 52 mm to 72mm depending upon the number of rows. A plurality of tubes is fitted between two header plates with one end fitted in the slot of the first header plate and the other end fitted in the corresponding slot of the second header plate by brazing means. Each tube of the plurality of tubes is a folded tube having tube surface provided with a plurality of dimples configured uniformly on the tube surface at a spacing of 10 mm and 5 mm offset and having a folded joint in the mid region along the complete length on one side thereof. In an embodiment, the dimples are circular shaped trapezoidal sectioned dimples having minor diameter ranging from 0.5 mm to 1.5 mm, major diameter ranging from 1.5 mm to 2.5 mm and depth ranging from 0.2 to 0.3. The tubes have plane surface with no dimples near each end thereof. In a preferred embodiment, the tube is having tube size selected from 24 mm, 28 mm and 34mm. The plurality of louvered fins is disposed between each pair of adjacent tubes. The plurality of fins is having a leading edge and a trailing edge, with a leading side louver angle ranging from 31 to 35 deg. and the trailing side louver angle ranging from 19 to 23 deg.

Brief description of the drawings
The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figures 1A, 1B, 1C and 1D show a side view and cut sectional views of a multi row radiator, in accordance with the present invention;
Figures 2A, 2B, 2C and 2D show top views and cut sectional views of header plate of the multi row radiator, in accordance with the present invention;
Figures 3A and 3B show side view and a sectional view of B tube of the multi row radiator, in accordance with the present invention;
Figure 4 shows a closer view of cut outs of a core support of the multi row radiator, in accordance with the present invention; and
Figure 5 shows detailed cross sectional view of asymmetric louvered triangular fins of the multi row radiator, in accordance with the present invention;
Figure 6 is a bar graph showing comparison between the heat performance of the multi row radiator of present invention and that of the radiator with plain tubes of the prior art;
Figure 7 is a bar graph showing comparison between the cooling air pressure drop of the multi row radiator of present invention and that of the radiator with plain tubes of the prior art; and
Figure 8 is a bar graph showing comparison of the core weight of the multi row radiator of present invention and that of the radiator with plain tubes of the prior art.

Detailed description of the embodiments:
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiments.
The present invention provides a multi row radiator having a combination of dimpled B tubes with multiple rows along with asymmetric triangular louvered fins. The combination enhances the radiator thermal performance, compared to the existing conventional multi row radiators, with plain flat tubes.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description and in the table below.
Table 1:
Ref No: Component Ref No: Component
8 Header- tube joint 40 Core support
10 Fluid inlet 60 Fins
12 Gap 72 Dimples on tube
14 Slot 74 Fold
20A, 20B Header plates 80 Tubes
30 Cutout 90 Radiator core
Referring to the figures from 1 to 5, a multi row radiator (100) (hereinafter referred as “the radiator (100)”) is shown in accordance with the present invention. The radiator (100) comprises of two header tanks (not shown) fitted on to opposite sides of a radiator core (90), two header plates (20), a core support (40), a plurality of fins (60) and a plurality of tubes (80) as shown in Fig 1. The first header tank is fitted with a coolant inlet and the second header tank is fitted with a coolant outlet. Two header plates (20) fitted on two opposite faces of the core support (40) defines the radiator core (90).
Two header plates (20A, 20B) are provided with multiple rows of array of parallel slots (14) having a gap of 3 to 5 mm between two slots (14) of the adjacent rows. Cut outs (30) are provided at 2/3rd of the core height of the core support (40) to compensate for thermal expansion and avoid breakage due to higher thermal stresses. In an embodiment, the number of rows provided on two header plates (20A, 20B) ranges from two to four. The core thickness ranges from 52 mm to 72 mm depending upon the number of rows.
The plurality of tubes (80) are arranged between two header plates (20) with one end fitted in the slot (14) of the first header plate (20A) and the other end fitted in the corresponding slot (14) of the second header plate (20B). Thus, the radiator core (90) includes multiple rows of the array of parallel tubes (80) held between two header plates (20). Referring to figure (2D), the header-tube joint (8) is brazed to hold the tube (80) firmly in the header plate (20) such that the header-tube joint (8) can avoid any coolant leakage or tube cracking due to improper loose joint.
The plurality of tubes (80) are folded tubes (B tubes) having tube surface provided with a plurality of dimples (72). The radiator coolant flows through the plurality of tubes (80). The dimples (72) are configured uniformly on the tube surface at a spacing of 10 mm and 5 mm offset to augment the heat transfer co-efficient on the tube side, by generating local turbulence, as against the conventional plain flat tubes. In an embodiment, the dimples (72) are circular shaped trapezoidal sectioned dimples having minor diameter ranging from 0.5 mm to 1.5 mm and major diameter ranging from 1.5 mm to 2.5 mm. The depth of the dimple (72) ranges from 0.2 to 0.3 mm with a connecting radius of 0.2 mm along the edges. The tubes (80) are having plane surface (76) with no dimples (72) near each end thereof. The length of plane surface (76) ranges from 10 mm to 15 mm. The tubes (80) are having a folded joint (74) in the mid region along the complete length on one side thereof. The folded joint (74) (center pillar) provides strength to the tube (80). The tube (80) and the folded joint (74) are formed by the rolling process. In a preferred embodiment, the tube is having tube size selected from 24 mm and 28 mm. The plurality of tubes (80) having 24 mm diameter, arranged in two rows with 4 mm gap (12) there between, provides a core thickness of 52 mm while the plurality of tubes (80) having 28 mm diameter, arranged in two rows with 4 mm gap (12) there between, provides a core thickness of 60 mm.
The plurality of fins (60) is disposed between each pair of adjacent tubes. The plurality of fins (60) is asymmetric fins having a leading edge and a trailing edge, with different louvered fin angles on the leading and trailing side as seen in Fig. 5. Louver angles are differentiated to reduce the trailing edge side cooling air pressure drop. Leading side louver angle is 33 + 2o greater than the trailing edge louver angle 21 + 2o. The different angles of trailing edge are less effective in terms of heat transfer as compared to the leading edge.
It will be evident from the experimental results given in Table 2 and 3 and also from figures 6, 7 and 8 that the multi row radiator (100) of the present invention tubes (80) enhances the radiator thermal performance compared to the existing conventional multi row radiators with plain flat tubes. Bar graphs of the figure 6 and 7 respectively show the comparison of the heat performance and cooling air pressure drop of the multi row radiator of present invention and that of the radiator with plain tubes of the prior art.
Table 2:
Core size: 600 x 600 x …@ 5m/s cooling air velocity,
90 lpm water flow 55°C temperature difference
Core type CF 75-2 CF 75-3 RCS 24-1 RCS 28-1 RCS 52-2
Number of tube rows 2 3 1 1 2
Fin type Louvered
Core thickness (mm) 48 74 24 28 52
Core weight (Kg) 5.659 7.787 3.251 3.896 5.981
Tube size (mm) 22 22 24 28 24
Tube width (mm) 1.6 1.8 1.3 1.4 1.3
Number of tubes 156 201 90 90 160
Tube pitch 7.6 8.8 6.6 6.6 7.4
Fin pitch 3.25 4 2.25 2.5 3.25
Heat transfer 68.14 79.26 71.76 76.3 83.6
Cooling air pressure drop (Pa) 228.62 186.7 242.61 199 198.26
Water pressure drop (KPa) 1.62 1.07 14.98 8.92 3.05
Table 3:
Core size: 600 x 600 x …@ 8m/s cooling air velocity,
150 lpm water flow 55°C temperature difference
Core type CF 75-2 CF 75-3 RCS 24-1 RCS 28-1 RCS 52-2
Number of tube rows 2 3 1 1 2
Fin type Louvered
Core thickness (mm) 48 74 24 28 52
Core weight (Kg) 5.659 7.787 3.251 3.896 5.981
Tube size (mm) 22 22 24 28 24
Tube width (mm) 1.6 1.8 1.3 1.4 1.3
Number of tubes 156 201 90 90 160
Tube pitch 7.6 8.8 6.6 6.6 7.4
Fin pitch 3.25 4 2.25 2.5 3.25
Heat transfer 98.91 109.89 107.76 109.81 118.94
Cooling air pressure drop (Pa) 466.35 465.38 454.88 410.43 412.87
Water pressure drop (KPa) 3.82 2.49 36.48 24.81 8.41
Advantages of the invention
1. The radiator (100) provides high thermal performance of tube side heat transfer enhancement, due to the local turbulence generated by tube dimpling.
2. The radiator (100) provides lower cooling air pressure drop using asymmetric louvered fins.
3. The radiator (100) provides light weight radiators of the same volume using thinner tubes.
4. The radiator (100) provides lower fan power requirements to overcome the same heat load in the same available packaging volume.
5. The radiator (100) provides better inventory management, as existing 24 mm thick and 28 mm wide tubes are used for developing multi-row radiators.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the scope of the invention.

,CLAIMS:We claim:
1. A multi row radiator (100) having two header tanks fitted on two opposite faces of a radiator core (90), the first header tank fitted with a coolant inlet and the second header tank fitted with a coolant outlet, the radiator core (90) comprising:
a core support (40) fitted with two header plates (20A, 20B) on two opposite faces thereof, the header plates (20A, 20B) provided with multiple rows of an array of parallel slots (14) having a gap of 3 to 5 mm between two slots (14) of the adjacent rows, wherein the core support is provided with cut outs (30) at 2/3rd of the core height to compensate for thermal expansion and avoid breakage due to higher thermal stresses;
a plurality of tubes (80) fitted between two header plates (20) with one end fitted in the slot (14) of the first header plate (20A) and the other end fitted in the corresponding slot (14) of the second header plate (20B), wherein each tube of the plurality of tubes (80) is a folded tube having tube surface provided with a plurality of dimples (72) configured uniformly on the tube surface at a spacing of 10 mm and 5 mm offset and having a folded joint (74) in the mid region along the complete length on one side thereof; and
a plurality of fins (60) disposed between each pair of adjacent tubes and having a leading edge and a trailing edge, with a leading side louver angle ranging from 31 to 35 deg. and the trailing side louver angle ranging from 19 to 23 deg.
2. The multi row radiator (100) as claimed in claim 1, wherein each tube of the plurality of tubes (80) is fitted between two header plates (20) at the header-tube joint (8) by brazing means.
3. The multi row radiator (100) as claimed in claim 1, wherein the number of rows provided on two header plates (20A, 20B) ranges from two to four.
4. The multi row radiator (100) as claimed in claim 1, wherein the core thickness ranges from 52 mm to 72 mm depending upon the number of rows.
5. The multi row radiator (100) as claimed in claim 1, wherein the dimples (72) are circular shaped trapezoidal sectioned dimples having minor diameter ranging from 0.5mm to 1.5mm and major diameter ranging from 1.5 mm to 2.5mm.
6. The multi row radiator (100) as claimed in claim 1, wherein depth of the dimple (72) ranges from 0.2 to 0.3 mm with a connecting radius of 0.2 mm along the edges.
7. The multi row radiator (100) as claimed in claim 1, wherein the tubes (80) are having plane surface (76) with no dimples (72) near each end thereof.
8. The multi row radiator (100) as claimed in claim 1, wherein the he tubes (80) are having tube size selected from 24 mm, 28 mm and 34 mm.
Dated this 18th day of March, 2020

Prafulla Wange
(Agent for the applicant)
(IN/PA-2058)