Field of the invention

The invention relates to cooling devices in automotive applications. Particularly, the invention relates to a liquid charge air cooling device with charge air flow mechanism.

Background

As of today, the internal combustion engine systems extensively employ turbochargers or superchargers to improve the fuel efficiency. Turbochargers or superchargers differ from each other in their driving mechanisms. While turbochargers include a turbine wheel being driven by the exhaust gas, superchargers include a rotary compressor directly driven by the engine. However in both the cases, combustion air gets compressed prior to its admission to the combustion chamber of internal combustion engine. So, by compressing the air in the supercharger or turbocharger, large amount of combustion air is being inducted into combustion chamber, which results in improved combustion efficiency at any given operating condition. One major limitation of employing the turbochargers or superchargers is during the compression process, the combustion air simultaneously gets heated, which in turn results in decrease in density of combustion air.

To overcome this limitation, another heat exchanger is introduced between the supercharger or turbocharger and the intake manifold. The principle applied is that the hot combustion air from the turbocharger or supercharger is being supplied to charge the air cooler, where it loses its heat to an external cooling media. Air or liquid is allowed to pass through the charge air cooler in a flow path isolated from combustion air. Cooling of the combustion air results in increased density of combustion air, which as a result, improves the combustion efficiency and NOx level.

Currently, the automotive sector is growing at a very fast pace, which is leading to tighter environment norms and requirement of highly efficient as well as compact heat exchangers. Thus, there exists a need of highly optimized systems, which can provide increased rate of heat transfer with lesser pressure drop & overall compactness of the heat exchanger. Hence, the present invention is basically aimed to meet such needs, where charge air is being circulated around a heat exchanger in a cross counter flow type arrangement with the help of precisely designed flow mechanism.

Looking at specific prior art, U.S. Patent No. 4436145 dated 13 March 1984, issued to Joseph N. Manfredo discloses an engine charge air cooler for mounting within the intake manifold, wherein charge air is supplied to a heat exchanger employing liquid coolant inside tubes to cool the charge air and inter tube spacing forms the flow path for charge air.

Another patent, U.S. Patent No. 7791710 B2 dated 14 Sep. 2010, issued to Bernhard Lamich discloses a heat exchanger having two banks of equally spaced tubes through which liquid coolant flow in a U flow manner. The inter tube spacing of disclosed heat exchanger consist corrugated ribs to form flow channels through which charge air is allowed to flow. So cooling of charge air has been achieved in two stages by respective tube banks.

Another granted patent, U.S. Patent No. 2013/0152906 A1 dated 20 Jun 2013, issued to Michael Mater further discloses a charge air cooler where charge has been allowed to flow around the periphery of a channel carrying the conventional coolant. The outer surface of the flow channel has fine grooves to achieve enhanced rate of heat transfer. Further, the channel carrying coolant has a provision to rotate about its own axis to enhance the cooling of charge air.

U.S. Patent No. 2013/0220289 A1 dated 29 Aug. 2013, issued to Karen Elizabeth relates to a liquid cooled charge air cooler meant for integration of charge air cooler with intake manifold. The charge air flow through a heat exchanger comprises plurality of flat tubes spaced apart by heat transfer surfaces. Charge air enters into the flow channels via an inlet tank header, whereas, liquid coolant flow through the tubes. Outlet of heat exchanger is directly mounted on the intake manifold of internal combustion engine.

However, the aforementioned prior art has certain limitations, such as: in traditional charge air coolers, a heat exchanger requires different type of tube fin configuration. i.e. existing tube fin configuration used in radiators, heater cannot be used. The entire heat exchanger has to be redesigned in case of existing charge air coolers. i.e. existing assemblies/ child parts of radiators and heaters cannot be used. Also, less heat is transferred per unit area that results in a bigger size.

Traditional charge air coolers involve cross flow of two heat transfer substances. Thus, better heat transfer characteristics (i.e. lower value of temperature difference at the outlets of two heat exchanging mediums) of counter/ parallel flow type arrangements cannot be utilized.

Summary

The present invention discloses a liquid cooled charge air cooling device having charge air flow mechanism in order to achieve advantages of both cross flow as well as counter flow type heat exchangers. Both the charge air and liquid coolant has been introduced in such a way that both the heat transfer substances, i.e. charge air and liquid coolant flows in opposite direction. Charge air is introduced to the heat exchanger with the help of an inlet tank header. The flow of charge air around the heat exchanger is precisely controlled by a casing, which actually ensures a uniform and smoothly guided flow to successive passes of heat exchanger. An outlet tank header serves the purpose of supplying charge air to the engine intake manifold.

The present invention can be described with the help of specific embodiments underlined below:

According to one of the embodiments, a liquid cooled type heat exchanger comprises at least two or more gas flow passes in a charge air cooling device of automotive applications.

According to another embodiment, said heat exchanger comprises a primary heat exchanger and a charge air flow mechanism.

According to another embodiment, charge air is circulated around a primary heat exchanger in a plurality of passes to form a cross counter type of flow arrangement. The charge air enters normal to a plurality of tubes.

According to yet another embodiment, the plurality of tubes in the primary heat
exchanger has been spaced apart by vertical heat transfer surfaces.

According to still another embodiment, the vertical heat transfer surfaces are primarily louvered type of fins.

According to another embodiment, the type of fin configuration is selected from plate
type, wavy fin type, and strip fin type. Optionally, the type of fin configuration is
dimpled having micro shaped channels.

According to yet another embodiment, the charge air flow mechanism consists of an inlet tank header, subsequent charge air casings and outlet tank header.

According to another embodiment, the inlet tank header, outlet tank header and charge air casings can be made as a single part or as a group.

According to one more embodiment, the charge air casing can be shaped such that R1 is greater than R2 and R3 is greater than R4.

According to another embodiment, the orientation of inlet tank header, outlet tank header and charge air casing is with respect to flow of coolant in the plurality of tubes of primary heat exchanger.

According to yet another embodiment, the number of passes can be increased or decreased depending on the available heat transfer face area of primary heat exchanger.

Brief Description of Drawings

Figure 1 illustrates schematic diagrams of the various heat exchangers known in the prior art.
Figure 2 illustrates a liquid cooled charge air cooling device, according to an embodiment of the invention
Figure 3 illustrates a liquid cooled charge air cooling device, according to another embodiment of the invention.
Detailed Description

The present invention discloses a charge air flow mechanism around a heat exchanger to form a liquid cooled type charge air cooling device. The device includes a heat exchanger having a plurality of equally spaced flat tubes through which liquid coolant flows. Fins extend between flat tubes to define a charge air flow path between the charge air inlet and outlet. The heat exchanger is surrounded by casings on both side walls of tubes characterized by the lower dimensions of tube. The casing is designed in such a way to achieve a very efficient flow of charge air around the aforementioned heat exchanger, in order to achieve uniformly distributed flow in each pass of flow mechanism with a minimal pressure drop.

The invention provides a method for modular and standardized design of charge air coolers having highest level of heat transfer by increased overall contact time between two heat exchanging mediums. The primary advantage of disclosed invention is the improved heat exchanger effectiveness by the efficient use of cross counter flow type charge air flow mechanism. Another inherent advantage of this invention is the relatively compact design of overall heat exchanger with reduced weight. The same can be used in a wide range for automotive and non-automotive applications as a replacement of existing air to air charge air cooler as well as for the integration of engine intake manifold with charge air cooler.

Referring to the prior art, in figure 1(a), 1(b), 1(c), the schematic diagrams of single pass cross flow heat exchanger, multi pass cross- parallel flow & multi pass cross- counter flow type heat exchanger is illustrated. It is well known today that the cross counter flow type heat exchangers are more efficient than cross flow or cross- parallel flow type heat exchangers, which form the fundamental embodiment of present invention.
Further, the heat rejection capacity for any cross flow heat exchanger mainly depends on value of correction factor (F), which actually accounts for decrease in overall log mean temperature difference due to change in flow arrangement from counter flow to cross flow. The value of correction factor (F) depends on the inlet and outlet temperatures of the corresponding heat exchanger.

The prior art depicts that outlet temperatures for the multi pass cross flow (parallel, counter) heat exchangers are such that the fluid getting cooled has relatively lower temperature than in case of single pass cross flow heat exchangers and for the fluid getting heated, temperature is higher than the one in single pass cross flow type. This, in turn, results in a higher value of correction factor (F) in multi pass cross flow (parallel, counter) type heat exchangers than the value of correction factor (F) in single pass cross flow type heat exchangers. Further, it has been observed that multi pass cross- counter flow type heat exchangers are more efficient than multi pass cross-parallel flow type heat exchangers due to higher value of both initial temperature difference (ITD) and resulting value of correction factor (F) in case of multi pass cross-counter flow type heat exchangers.

Referring to figure 2, a heat exchanger for the flow of liquid coolant in plurality of tubes and a charge air flow mechanism for circulating hot air around the heat exchanger is disclosed. This embodiment discloses a tank header, designed in such a way to facilitate parallel entry of coolant with respect to charge air.

As referred in figure 3, a heat exchanger for the flow of liquid coolant in plurality of tubes and a charge air flow mechanism for circulating the hot air around the heat exchanger is disclosed, according to another embodiment of the invention. However in this embodiment, the tank header is designed in such a way that charge air is allowed to enter parallel to the direction of flow of coolant in tubes.

The figures 2 and 3 form two closely related embodiments of the invention. Both the heat exchangers disclosed in figure 2and 3 are same in terms of working principle as well as in the basic heat exchanger configuration. Here, the basic heat exchanger configuration may refer to the type of tube fin configuration, charge air flow mechanism & inlet and outlet tanks for primary heat exchanger i.e. the heat exchanger carrying the liquid coolant.
The only difference between the two figures 2 and 3 is the design of inlet tank header 8 and outlet tank header for charge air 9. Design of inlet tank header 8 and outlet tank header 9 for charge air in figure 2 allows parallel entry of charge air with respect to liquid coolant, whereas design of inlet and outlet tank headers 8 and 9 disclosed in figure 3 are meant for entry of charge air normal to liquid coolant.

Another important aspect of present invention is the design of charge air casing 10 and 11 which is in such a way that, once the charge air flow through the certain well defined face area of heat exchanger and gets past the said heat exchanger. It is redirected towards the remaining face area of heat exchanger by the precisely optimized design of charge air casing. This process continues till charge air flowing through the heat exchanger covers all the available heat transfer area of primary heat exchanger 7. This can be observed in figures 2 and 3 of present invention, wherein top views of entire heat exchanger assembly depicts direction of charge air flow, which in turn results in charge air flow in number of passes controlled by face area of primary heat exchanger.

With reference to both figures 2 and 3, heat exchanger 7 includes plurality of flat tubes through which liquid coolant is allowed to flow. The said tubes are equally spaced and inter tube spacing consists of vertical heat transfer surfaces also termed as fins.
One aspect of present invention discloses at least one manifold 5 to distribute liquid coolant into plurality of tubes and a collection chamber 6 to collect liquid from said tubes. The entry and exit of liquid coolant has been served by inlet pipe 1 and outlet pipe 2. According to another embodiment, a charge air flow mechanism is disclosed that consists of charge air inlet pipe 3, inlet tank header 8, charge air casings 10 and 11 to facilitate flow of charge air around the heat exchanger and an outlet tank header 9. The charge air casing 10 and 11 disclosed in figures 2 and 3 has been designed in such a way to provide well guided charge air flow to successive passes of primary heat exchanger 7. The outlet pipe 4 is in connection with intake manifold to supply the cooled air.

The inlet charge air tank header 3 and outlet charge air tank header 4 in both the major embodiments have a unique design to serve the purpose of uniform flow to the heat exchanger with a minimal pressure drop. The shape and orientation of inlet and outlet tank headers for charge air in both the embodiments i.e. figure 2 and 3 has been maintained in such a way that it provides homogeneous flow to the heat exchanger with reduced pressure drop for different engine operating conditions as well as for different orientation of intake manifold with respect to the charge air cooler.

CLIAMS:1. A liquid cooled type heat exchanger comprising at least two or more gas flow passes in a charge air cooling device of automotive applications.
2. A liquid cooled type heat exchanger of claim 1, said heat exchanger comprises a primary heat exchanger and a charge air flow mechanism.
3. A liquid cooled type heat exchanger of claim 1, wherein charge air is circulated around a primary heat exchanger in a plurality of passes to form a cross counter type of flow arrangement.
4. A liquid cooled type heat exchanger of claim 3, wherein charge air enters normal to a plurality of tubes.
5. A liquid cooled type heat exchanger of claim 4, where the plurality of tubes in the primary heat exchanger has been spaced apart by vertical heat transfer surfaces.
6. A liquid cooled type heat exchanger of claim 5, wherein the vertical heat transfer surfaces are primarily louvered type of fins.
7. A liquid cooled type heat exchanger of claim 6, wherein the type of fin configuration are selected from plate type, wavy fin type, and strip fin type.
8. A liquid cooled type heat exchanger of claim 7, wherein the type of fin configuration is dimpled having micro shaped channels.
9. A liquid cooled type heat exchanger of claim 2, wherein the charge air flow mechanism consists of an inlet tank header, subsequent charge air casings and outlet tank header.
10. A liquid cooled type heat exchanger of claim 9, wherein the inlet tank header, outlet tank header and charge air casings can be made as a single part or as a group.
11. A liquid cooled type heat exchanger of claim 10, wherein the charge air casing can be shaped such that R1 is greater than R2 and R3 is greater than R4.
12. A liquid cooled type heat exchanger of claim 9, wherein the orientation of inlet tank header, outlet tank header and charge air casing is with respect to flow of coolant in the plurality of tubes of primary heat exchanger.
13. A liquid cooled type heat exchanger of claim 1, wherein the number of passes can be varied depending on the available heat transfer face area of primary heat exchanger.