Abstract:
The invention relates to a system which is used to cool at least one piece of motor vehicle equipment to a low temperature, comprising a heat transfer fluid circulation loop. According to the invention, a low-temperature heat exchanger ( 60 ) and at least one equipment exchanger ( 102 ) are mounted to the aforementioned circulation loop. The heat exchange surface of the equipment exchanger ( 102 ) is divided into at least first and second heat exchange sections ( 104,106 ). A first flow (Q&lt;SB&gt;1&lt;/SB&gt;) of heat-transfer fluid passes through the first heat exchange section ( 104 ), while a second smaller flow (Q 2 ) passes through the second section. The invention is suitable for motor vehicle heat exchangers.

Description:
RELATED APPLICATIONS 
     This application claims priority to and all the advantages of U.S. patent application No. 10/549,887 filed on Sep. 16, 2005, which claims priority to International Patent Application No. PCT/FR2004/000636 filed on Mar. 16, 2004, which claims priority to French Patent Application No. FR 03 03495, filed on Mar. 21, 2003. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a system for cooling to a low temperature at least one piece of equipment, particularly a piece of motor vehicle equipment, comprising a circulation loop for heat-transfer fluid on which loop are mounted a low-temperature heat exchanger and at least an equipment exchanger comprising a heat-exchange surface. It also relates to a low-temperature heat exchanger and to an equipment exchanger that form part of the cooling system of the invention. 
     Present-day motor vehicles comprise an increasingly high number of pieces of equipment which exchange heat with their external surroundings. Some of these pieces of equipment need to be heated up, for example the fuel heater. However, most of these pieces of equipment need to be cooled. This is the case, in particular, of the condenser which forms part of the motor vehicle cabin air-conditioning circuit, and is also true of the oil cooling radiator and the intercooler radiator. Increasingly often, also, the exhaust gases are cooled in order to reduce pollution. 
     Some of these pieces of equipment, such as the oil cooling radiator or the radiator that cools the exhaust gases, do not need to be cooled to a low temperature. They can therefore be placed without disadvantage in the cooling circuit of the vehicle combustion engine through which circuit there circulates a heat-transfer fluid the temperature of which generally ranges between 85° C. and 100° C. However, other pieces of equipment need to operate at the lowest possible temperature so as to improve their efficiency. This is the case in particular of the condenser of the air-conditioning circuit and the intercooler. 
     This is why provision is made for currently known vehicles to be equipped with a low-temperature cooling circuit through which a heat-transfer fluid circulates at a temperature below that of the high-temperature circuit. The condenser of the air-conditioning circuit or the intercooler may thus be cooled more effectively down to a lower temperature. 
     However, in currently known vehicles, the low-temperature cooling circuit is equipped with a low-temperature heat exchanger which has just one inlet nozzle and just one outlet nozzle, the heat-transfer fluid circulating in one or several passes. The low-temperature heat exchanger delivers just one temperature level and the fluid that is to be cooled, for example the air in the intercooler, is cooled to just one level of heat exchange. 
     In currently known vehicles, the coolant fluid is condensed by the ambient air but it is possible, by using a low-temperature circuit, to condense it using the same heat-transfer fluid as is used to cool the engine. 
     The cooling of these fluids is therefore often insufficient to guarantee an optimum reduction in temperature. For example, the temperature of the charge air is too high on the intake side at critical points in the event of high load on the engine, or alternatively the condensation of the coolant fluid is insufficient, which results in degraded performance of the air-conditioning circuit. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is a system for cooling, to a low temperature, at least one piece of motor vehicle equipment which solves these disadvantages. 
     These objects are achieved, in accordance with the invention, through the fact that the heat-exchange surface of the equipment exchanger is split between at least a first and a second heat-exchange section, the first heat-exchange section having a first flow rate of heat-transfer fluid passing through it, the second heat-exchange section having a second flow rate of heat-transfer fluid passing through it, the first flow rate being greater than the second flow rate. 
     By virtue of this characteristic, the fluid that is to be cooled is cooled to at least two heat-exchange levels. Of course, it may just as easily be cooled to more than two heat-exchange levels. 
     The fluid involved in said first and second flow rates of fluid is the fluid from the low-temperature heat exchanger, the sum of said flow rates advantageously being equal to the flow rate entering said low-temperature heat exchanger. 
     This cooling system can advantageously be applied to a condenser of an air-conditioning circuit which comprises a stage for condensing and a stage for supercooling the coolant fluid. 
     The low-temperature heat exchanger might deliver just one temperature level. In this case, it has a single outlet nozzle. However, in a preferred embodiment, the low-temperature heat exchanger comprises at least a first and a second outlet nozzle for the heat-transfer fluid, the first nozzle being connected to the first heat-exchange section of the equipment exchanger, the second outlet nozzle for the heat-transfer fluid being connected to the second heat-exchange section of the equipment exchanger, the heat-transfer fluid leaving the low-temperature heat exchanger via the first nozzle being at a temperature higher than that of the fluid leaving the low-temperature heat exchanger via the second nozzle. 
     By virtue of this characteristic, the temperature of the heat-transfer fluid is lower in the second heat-exchange section of the equipment exchanger, thus allowing the fluid passing through this exchanger to be cooled to a greater extent. 
     In one particular embodiment, the low-temperature heat exchanger comprises a multitude of fluid circulation passes through which the heat-transfer fluid travels in succession, the first nozzle being located upstream of the second nozzle with respect to the circulation of the heat-transfer fluid through the successive passes. 
     In this way, the heat-transfer fluid tapped off by the first nozzle is at a higher temperature than the heat-transfer fluid tapped off by the second nozzle. Of course, it is possible to provide more than two outlet nozzles. It is possible, for example, to provide a third outlet nozzle situated downstream of the second nozzle so as to tap off fluid at an even lower temperature still. 
     Advantageously, the flow rates decrease. In other words, the flow rate tapped off by the first nozzle is higher than the flow rate tapped off by the second nozzle which is itself higher than the flow rate tapped off by the third nozzle, etc. It is possible, for example, to provide increasing pressure drops in order to achieve this result. 
     Additional or alternative characteristics of the invention are listed below:
         the circulation loop comprises a circulation pump;   the circulation loop is mounted as a bypass between the inlet and outlet of the cooling circuit of the motor vehicle combustion engine;   the equipment exchanger is an intercooler;   the equipment exchanger is a condenser forming part of the motor vehicle cabin air-conditioning circuit;   the condenser comprises a coolant-fluid condensation section and a coolant-fluid supercooling section and a reservoir for filtering and dehydrating the coolant fluid, the condensation section constituting the first, heat-exchange section of the equipment exchanger and the supercooling section constituting the second heat-exchange section of the equipment exchanger;   the reservoir for filtering and dehydrating the coolant fluid may be inserted between the condensation section and the supercooling section or alternatively it may be situated after the supercooling section.       

     Other characteristics and advantages of the invention will become further apparent from reading the description which follows of exemplary embodiments given by way of illustration with reference to the attached figures. In these figures: 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  illustrates the management of the thermal energy given off by a motor vehicle engine using a system comprising a high-temperature loop and a low-temperature loop; 
         FIG. 2  depicts a first example of circulation in an independent low-temperature cooling system according to the invention; 
         FIG. 3  depicts a second embodiment of an independent low-temperature cooling system according to the invention; 
         FIG. 4  depicts a cooling system according to the invention mounted as a bypass at the terminals of the high-temperature circuit of the combustion engine; and 
         FIGS. 5 and 6  are partial views of the cooling system of the invention adapted to the cooling of an air-conditioning condenser. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is an overall view of a system for managing the thermal energy given off by an engine  10  of a motor vehicle, which comprises a high-temperature loop denoted by the general reference  2  and a low-temperature loop denoted by the general reference  4 , the loops  2  and  4  being independent. The high-temperature loop  2  comprises the engine  10 , a circulation pump  12  circulating the heat-transfer fluid through the circuit, a thermostat or thermostatic valve (not depicted) and a high-temperature radiator  18  which is the main radiator of the vehicle. The high-temperature loop also comprises a heating branch  22  on which there is mounted a unit heater  24  used for heating the cabin of the vehicle. Furthermore, pieces of equipment which do not need to be cooled to a very low temperature, for example an oil radiator  34  or an exhaust gas cooler  38 , are mounted on a branch  32 . 
     The low-temperature loop  4  comprises a circulation pump  58 , a low-temperature heat exchanger  60  (in this instance a cooling radiator) and an equipment exchanger  102 , for example a condenser of an air-conditioning circuit or an intercooler. The pump  58  and the exchangers  60  and  102  are mounted in series in a branch  62 . 
     The flow rate of heat-transfer fluid circulating through the high-temperature loop  2  is about ten times as high as the flow rate circulating the low-temperature loop  4 . By way of example, the flow rate circulating through the high-temperature radiator  18  may range from 5000 to 10,000 liters per hour, while the flow rate circulating through the low-temperature radiator  60  ranges between 0 and 1,000 liters/hour. 
       FIG. 2  depicts a first embodiment of a low-temperature cooling system according to the invention. The low-temperature radiator  60  comprises an inlet header box  72  and an outlet header box  74 . An inlet nozzle  76  is connected to the inlet header box  72  and an outlet nozzle  78  is connected to the outlet header box  74 . A matrix of tubes  80 , generally flat, is arranged between the inlet  72  and outlet  74  header boxes. The inlet header box  72  is split into two by a transverse partition  82  and, likewise, the outlet header box  74  is split into two by a transverse partition  84 . Thus three passes  86 ,  88  and  90  for the circulation of the heat-transfer fluid are delimited. 
     Having entered the header box  72 , the heat-transfer fluid first of all travels through the pass  86 , as indicated schematically by the arrows  92 , then the pass as indicated schematically by the arrow  94  and finally the pass  90  as indicated schematically by the arrow  96 . The cooling system also comprises an equipment exchanger  102 , for example an intercooler or a condenser of an air-conditioning circuit. The equipment exchanger  102  comprises an inlet header box and an outlet header box, each of these boxes being split into two by a transverse partition (not depicted). This then determines two heat exchange sections  104  and  106 . These heat-exchange sections are defined by the number of tubes present in the two chambers delimited by the transverse partitions of the header boxes. As can be seen from  FIG. 2 , the heat-exchange section  104  is preferably larger than the heat-exchange section  106 . 
     The fluid circulation loop comprises a branch  108  in which the heat-transfer fluid circulates in the direction defined by the arrow  110  under the impetus of a circulation pump  112 , for example an electric pump. The fluid circulation loop also comprises two branches  114  and  116  in which the fluid circulates in the direction defined by the arrows  118 . 
     As indicated schematically by the arrows  120  and  122 , the fluid that is to be cooled, for example the air in the intercooler or the coolant fluid in the air-conditioning circuit travels first of all through the heat-exchange section  104  then through the heat-exchange section  106 . Thus, the fluid that is to be cooled is cooled to two levels of heat exchange. 
     In consequence, the flow rate Q 1  of the heat-transfer fluid which circulates in the first heat-exchange section  104  is greater than the flow rate Q 2  which circulates in the second heat-exchange section  106 . 
       FIG. 3  depicts a second embodiment of a cooling system according to the invention. In this example, the low-temperature radiator  60  comprises two outlet nozzles, namely a nozzle  78 , as before, and a second nozzle referenced  132 . The nozzle  132  taps off heat-transfer fluid at the first fluid circulation pass (arrows  92 ) while the second nozzle  78  taps off fluid at the last fluid circulation pass (arrow  96 ). Thus, the heat-transfer fluid which has flowed through just one pass of the low-temperature exchanger  60  emerges via the outlet nozzle  132  at a temperature higher than that of the heat-transfer fluid which has traveled in succession through the three passes of the exchanger  60  and which emerges via the outlet  78 . 
     In this example, the low-temperature cooling radiator  60  therefore delivers two temperature levels. The fluid of the first temperature level enters the heat-exchange section  104  via a pipe  134 , while the fluid of the second temperature level (which is lower) enters the heat-exchange section  106  via a pipe  136 . The distribution of the pressure drops in the circuit, particularly in the outlet nozzles  78  and  132  is such that the flow rate Q 1  that passes through the heat-exchange section  104  is higher than the flow rate Q 2  passing through the heat-exchange section  106 . 
     A system of this type may make it possible to bring the fluid that is to be cooled down to a temperature significantly lower than can be achieved in a system delivering just one temperature level. By way of example, the heat-transfer fluid emerges from the first pass at a temperature ranging between 40° C. and 60° C. After the second pass  94 , its temperature ranges between 30° C. and 50° C., and finally, after the third pass  90 , its temperature drops to about 20° C. to 40° C. The heat-transfer fluid entering the heat-exchange section  104  therefore has an average temperature of about 50° C., whereas the fluid entering the heat-exchange section  106  has a temperature of about 30° C. These values are given by way of indication and are dependent on ambient temperature. 
     The fluid that is to be cooled gives up most of its heat in the first heat-exchange section  104  before being placed in a heat-exchange relationship with a heat-transfer fluid at the far lower temperature which allows its outlet temperature to be lowered. This cooling system can advantageously be applied to a condenser of an air-conditioning circuit because it makes it possible, in the first heat-exchange section  104 , to condense the coolant fluid and supercool this fluid in the heat-exchange section  106 . 
       FIG. 4  depicts another embodiment of a cooling system according to the invention. In this system, the low-temperature cooling radiator  60  has four passes. Specifically, the inlet header box  72  has two transverse dividing partitions  142  and  146  while the outlet header box  74  has just one dividing partition  144 . The dividing partitions  142 ,  144  and  146  therefore determine four outbound and return paths for the heat-transfer fluid in the tubes of the low-temperature heat exchanger  60 . 
     An outlet nozzle  141  taps off the fluid after it has passed through the third pass. This fluid is carried, as in the previous example, to the heat-exchange section  104  by the pipe  134  of the equipment exchanger  102 . An outlet nozzle  143  taps off the heat-transfer fluid after it has passed through the fourth and final pass of the low-temperature heat exchanger  60 . This fluid is carried by the pipe  144  to the heat-exchange section  106  of the equipment exchanger  102 . Thus, as before, the fluid that passes through the heat-exchange section  106  is at a temperature lower than that of the fluid that passes through the heat-exchange section  104 . 
     Furthermore, unlike in the previous examples, the fluid circulation loop is not independent but is mounted as a bypass across the terminals of the high-temperature circuit  2 . A pipe  150  may tap off the fluid directly at the outlet from the engine. A pipe  152  is connected to the inlet of the vehicle engine. 
     Thus, in this embodiment, the temperature of the fluid is higher than in the previous cases. The heat-transfer fluid enters the inlet header box at a temperature of about 90° C. It emerges via the outlet nozzle  141  at a temperature of about 60° C. and via the outlet nozzle  143  at a temperature of about 40° C. It can thus be seen that, in spite of a high inlet temperature, the heat-transfer fluid can be cooled down to a relatively low temperature. 
     The cooling system of the invention can advantageously be applied to the cooling of the coolant fluid of an air-conditioning circuit as depicted in  FIGS. 5 and 6 . Indeed it is known that the condensers of air-conditioning circuits comprise an intermediate reservoir known as a “bottle” that allows the coolant fluid to be filtered and dehydrated. This intermediate reservoir also allows variations in volume of this fluid to be compensated for and allows the liquid and gaseous phases to separate. Its insertion between an upstream part and a downstream part of the condenser means that only fluid in the liquid state, which is thus supercooled below the liquid/gas equilibrium temperature can be made to circulate through this part of the condenser, thus improving condenser performance and making the performance relatively independent of the amount of fluid contained in the circuit. 
     The intermediate reservoir is generally fixed to a base secured to one of the header boxes of the condenser and through which two connecting pipes pass. This reservoir is equipped at its lower end with a head fixed to the base by means of a screw thread. 
     This situation corresponds to the embodiment depicted in  FIG. 6  in which the intermediate reservoir  154  is inserted between the heat-exchange sections  104  and  106 . The heat-exchange section  104  thus condenses the coolant fluid while the heat-exchange section  106  supercools it. 
     In an alternative form of embodiment depicted in  FIG. 5 , the reservoir may be arranged at the outlet of the supercooling stage. However, the condenser in the same way comprises a condensation section  104  and a supercooling section  106 .