Abstract:
This disclosure relates to a waste heat recovery (WHR) system and method for regulating exhaust gas recirculation (EGR) cooling, and more particularly, to a Rankine cycle WHR system and method, including a recuperator bypass arrangement to regulate EGR exhaust gas cooling for engine efficiency improvement and thermal management. This disclosure describes other unique bypass arrangements for increased flexibility in the ability to regulate EGR exhaust gas cooling.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/336,945, filed on Dec. 23, 2011, which claims the benefit of priority to U.S. Provisional Patent Application No. 61/426,972, filed on Dec. 23, 2010, the contents of which are hereby incorporated by reference in their entirety. 
    
    
     RESEARCH OR DEVELOPMENT 
     This invention was made with government support under “Exhaust Energy Recovery,” contract number DE-FC26-05NT42419 awarded by the Department of Energy (DOE). The government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to a waste heat recovery (WHR) system and method for regulating exhaust gas recirculation (EGR) cooling, and more particularly, to a Rankine cycle WHR system and method, including a heat exchanger bypass arrangement to regulate EGR cooling for engine efficiency improvement and thermal management. 
     BACKGROUND 
     Increasing the efficiency of internal combustion engines is critical to meet customer expectations and an array of government-mandated regulations. Internal combustion engines generate significant amounts of heat that heat exchangers eventually transfer to the air surrounding the internal combustion engine. If a portion of the wasted heat were recovered by performing a necessary engine function, the efficiency of the internal combustion engine would be improved. However, the recovery of this wasted heat can lead to conflict between the needs of two different portions of an internal combustion engine. The resolution of this conflict can lead to improved engine performance and efficiency. 
     SUMMARY 
     This disclosure provides a waste heat recovery system for an internal combustion engine. The waste heat recovery system comprises a fluid management circuit and a waste heat recovery circuit. The fluid management circuit includes a sub-cooler containing a liquid working fluid and a pump fluidly connected to the sub-cooler. The pump is operable to draw the liquid working fluid from the sub-cooler. The liquid working fluid has a first temperature. The waste heat recovery circuit includes a recuperator receiving the liquid working fluid from the pump and receiving a vaporized working fluid, wherein a transfer of heat from the vaporized working fluid to the liquid working fluid increases the temperature of the liquid working fluid. The waste heat recovery circuit also includes an EGR boiler flow control valve fluidly connected in parallel to the recuperator and receiving the liquid working fluid from the pump. The waste heat recovery circuit also includes a boiler receiving an EGR exhaust gas at a first inlet, the liquid working fluid at the first temperature from the EGR boiler flow control valve at a second inlet, and the liquid working fluid flowing from the recuperator at a third inlet. The liquid working fluid at the third inlet is at a second temperature. Heat is transferred from the EGR exhaust gas to the liquid working fluid to cause the liquid working fluid to vaporize. The liquid working fluid at the first temperature is used to control the amount of cooling provided to the EGR exhaust gas. 
     This disclosure also provides a waste heat recovery system for an internal combustion engine. The waste heat recovery system comprises a sub-cooler containing a liquid working fluid and a pump fluidly connected to the sub-cooler and operable to draw the liquid working fluid from the sub-cooler. The liquid working fluid has a first temperature. The waste heat recovery system also comprises a recuperator receiving the liquid working fluid from the pump and receiving vaporized working fluid from an EGR boiler, wherein the temperature of the liquid working fluid is increased by a transfer of heat from the vaporized working fluid to the liquid working fluid. The waste heat recovery system also comprises a heat exchanger fluidly connected to the recuperator, a first EGR boiler flow control valve fluidly connected to the pump in parallel to the recuperator and a second EGR boiler flow control valve fluidly connected to the recuperator and to the EGR boiler. The EGR boiler receives an EGR exhaust gas at a first inlet, the liquid working fluid at the first temperature flowing through the first EGR boiler flow control valve at a second inlet, the liquid working fluid flowing through the recuperator and the second boiler flow control valve at a third inlet, the liquid working fluid flowing through the recuperator and the heat exchanger at a fourth inlet. The liquid working fluid at the third inlet is at a second temperature higher than the first temperature and the liquid working fluid at the fourth inlet is at a third temperature higher than the second temperature. Heat is transferred from the EGR exhaust gas to the liquid working fluid to cause the liquid working fluid to vaporize. The liquid working fluid at the first temperature and the liquid working fluid at the second temperature are used to control the amount of cooling provided to the EGR exhaust gas. 
     This disclosure also provides a method for regulating EGR exhaust gas temperature in an engine using a Rankine cycle. The method comprises directing a first portion of a liquid working fluid pumped from s sub-cooler through at least one heat exchanger and then to an EGR boiler. The method also comprises directing a second portion of a liquid working fluid pumped from a sub-cooler through a bypass around the at least one heat exchanger to the EGR boiler. The EGR boiler receives the EGR exhaust gas. 
     Advantages and features of the embodiments of this disclosure will become more apparent from the following detailed description of exemplary embodiments when viewed in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of a first exemplary embodiment of the present disclosure. 
         FIG. 2  is a schematic of a second exemplary embodiment of the present disclosure. 
         FIG. 3  is a schematic of a third exemplary embodiment of the present disclosure. 
         FIG. 4  is a schematic of a fourth exemplary embodiment of the present disclosure 
         FIG. 5A  is a schematic of a first exemplary embodiment heat exchanger of the present disclosure. 
         FIG. 5B  is a schematic of a second exemplary embodiment heat exchanger of the present disclosure. 
         FIG. 5C  is a schematic of a third exemplary embodiment heat exchanger of the present disclosure. 
         FIG. 5D  is a schematic of a fourth exemplary embodiment heat exchanger of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , an engine system  10  in accordance with a first exemplary embodiment of the present disclosure is shown. Engine system  10  includes a fluid management circuit  12 , a portion of an exhaust circuit  11 , and elements that are part of a waste heat recovery system or circuit  14 . 
     Fluid management circuit  12  includes a sub-cooler  16 , a condenser  18 , a receiver  20 , and a level control valve  22 . Condenser  18  may be integral with sub-cooler  16  or may be commonly mounted on a common base  24 , which may include a plurality of fluid flow paths (not shown) to fluidly connect condenser  18  to sub-cooler  16 . Receiver  20  may be physically elevated higher than sub-cooler  16  and is connected to sub-cooler  16  through level control valve  22 , which connects to receiver  20  by a receiver conduit  26  and to sub-cooler  16  by a sub-cooler conduit  28 . Sub-cooler conduit  28  may connect directly to sub-cooler  16  or may connect indirectly to sub-cooler  16  by way of common base  24 . Sub-cooler  16  connects to a feed pump  32  by way of a pump conduit  30 . Feed pump  32  connects to a feed pump flow valve  34  by way of a feed valve conduit  36 . Feed pump flow valve  34  connects to receiver  20  by way of a dump conduit  38  and connects to a filter drier  42  by way of a filter drier conduit  40 . 
     Filter drier  42  connects to a recuperator  44  of waste heat recovery circuit  14  by way of a recuperator conduit  46  and connects to an EGR boiler flow control valve  48  by way of a first boiler control valve conduit  50 . EGR boiler control valve  48  connects to an inlet  74   c  of an EGR boiler/superheater  74  by way of a second boiler control valve conduit  51 . Recuperator  44  connects to a pre-charge air cooler (pre-CAC)  52  by way of a pre-CAC conduit  54 . Pre-CAC  52  connects to an exhaust heat exchanger  56  by way of an exhaust conduit  58 . Exhaust heat exchanger  56  is also part of exhaust circuit  11 . 
     Exhaust circuit  11  may include an aftertreatment system  60  that connects to an exhaust gas control valve  62  by way of an aftertreatment conduit  64 . Exhaust gas control valve  62  connects to exhaust heat exchanger  56  by way of a first exhaust gas conduit  66 . Exhaust gas control valve  62  also connects to a tailpipe or exhaust pipe  72  by way of a second exhaust gas conduit  68 . Exhaust heat exchanger  56  also connects to tailpipe or exhaust pipe  72  by way of a third exhaust conduit  70 . Exhaust gas heat exchanger  56  connects to an inlet  74   d  of EGR boiler/superheater  74  of waste heat recovery circuit  14  by way of an EGR conduit  76 . EGR boiler/superheater  74  is also an EGR cooler. EGR boiler/superheater  74  has an EGR inlet  74   a  and an EGR outlet  74   b.    
     EGR boiler/superheater  74  connects to an energy conversion device  78  by way of a first conversion device conduit  80 , which is connected to an outlet  74   e  of EGR boiler/superheater  74 . Energy conversion device  78  of Rankine cycle WHR system  10  is capable of producing additional work or transferring energy to another device or system. For example, energy conversion device  78  can be a turbine that rotates as a result of expanding working fluid vapor to provide additional work, which can be fed into the engine&#39;s driveline to supplement the engine&#39;s power either mechanically or electrically (e.g., by turning a generator), or it can be used to power electrical devices, parasitic or a storage battery (not shown). Alternatively, the energy conversion device can be used to transfer energy from one system to another system (e.g., to transfer heat energy from WHR system  10  to a fluid for a heating system). 
     Energy conversion device  78  may drive an auxiliary unit  82 . Auxiliary unit  82  may be part of a generator. If auxiliary unit  82  is a generator, it may feed a motor generator that may be part of a hybrid drive system. Energy conversion device  78  connects to recuperator  44  by way of a second conversion device conduit  84 . Recuperator  44  connects to condenser  18  of fluid management circuit  12  by a condenser conduit  88 . Recuperator  44  connects to receiver  20  by way of condenser conduit  88  and a receiver vent conduit  86 . 
     Engine system  10  includes a control module or control system  150 . Control module  150 , which may be a single processor, a distributed processor, an electronic equivalent of a processor, or any combination of the aforementioned elements, as well as software, electronic storage, fixed lookup tables and the like, is connected to certain components of fluid management circuit  12  and waste heat recovery circuit  14  by a wire harness  35 , though such connection may be by other means, including a wireless system. 
     Control module  150  connects to a fluid level sensor  13  associated with sub-cooler  16 . Control module  150  connects to feed pump flow valve  34 , EGR boiler flow control valve  48 , and exhaust gas control valve  62 . Control module  150  may connect to feed pump  32 . Control module  150  may also connect to temperature sensors positioned within EGR boiler/superheater  74 . Referring to  FIG. 5A , control module  150  may connect to a first EGR temperature sensor  15 , a second EGR temperature sensor  17 , a first working fluid temperature sensor  19 , a second working fluid temperature sensor  21 , and a third working fluid temperature sensor  23 . Temperature sensor  17  and temperature sensor  19  may be located in a lower temperature portion  25  of EGR boiler/superheater  74 . Temperature sensor  15 , temperature sensor  21  and temperature sensor  23  may be located in a higher temperature portion  27  of EGR boiler/superheater  74 . 
     Sub-cooler  16  stores liquid working fluid. If the level of liquid working fluid in sub-cooler  16  is less than a predetermined level as determined by a working fluid level sensor  13 , level control valve  22  opens. Liquid working fluid from receiver  20  will then flow through receiver conduit  26 , level control valve  22 , and then sub-cooler conduit  28  to enter either sub-cooler  16  or base plate  24  and then sub-cooler  16 , which are fluidly downstream of receiver  20 . 
     An engine system  10  belt (not shown) or an electric motor (not shown) drives feed pump  32 . Feed pump  32  pulls or draws liquid working fluid from sub-cooler  16  through pump conduit  30 . Feed pump  32  then forces liquid working fluid through feed valve conduit  36  to feed pump flow valve  34 . Feed pump flow valve  34  has two functions. Control module or control system  150  of engine system  10  monitors the cooling function of waste heat recovery circuit  14 . If waste heat recovery circuit  14  requires additional liquid working fluid, control module or control system  150  of engine system  10  directs proportional feed pump flow valve  34  of fluid management system  12  to provide additional liquid working fluid to waste heat recovery circuit  14  through filter drier conduit  40 . Proportional feed pump flow valve  34  directs any liquid working fluid not required by waste heat recovery circuit  14  to receiver  20  by way of dump conduit  38 . 
     Filter drier conduit  40  connects liquid working fluid to filter drier  42 . The function of filter drier  42  is to trap moisture, particulates and other contaminants that might interfere with or cause damage to the operation of waste heat recovery circuit  14 . In an existing Rankine cycle configuration, the liquid working fluid flows downstream from filter drier  42  through recuperator conduit  46  to recuperator  44 . Heat transfers from the hot vaporized working fluid returning to condenser  18  from energy conversion device  78  by way of second conversion device conduit  84  and recuperator  44  to the cooler liquid working fluid entering recuperator  44  by way of recuperator conduit  46 . As will be seen, the cooler liquid working fluid coming into recuperator  44  by way of recuperator conduit  46  may need to be heated to a level sufficient to perform useful work in EGR boiler/superheater  74 , and recuperator  44  may provide a first step in the heating process. While helping to heat the liquid working fluid coming into recuperator  44  by way of recuperator conduit  46 , vaporized working fluid entering recuperator  44  by way of second conversion device conduit  84  is cooled prior to entering condenser  18 . 
     From recuperator  44 , liquid working fluid now travels downstream to pre-CAC  52  by way of pre-CAC conduit  54 . Pre-CAC  52  receives air from an engine system  10  turbocharger compressor  53 . The air from turbocharger compressor  53  is heated by action of turbocharger compressor  53 . Pre-CAC  52  transfers some of the heat from that compressed air to the liquid working fluid entering pre-CAC  52  by way of pre-CAC conduit  54 . Similar to the function of recuperator  44 , pre-CAC  52  serves to raise the temperature level of the liquid working fluid entering pre-CAC  52  while cooling the air entering pre-CAC  52 . Charge air exiting pre-CAC  52  travels to a charge air cooler (not shown). The charge air cooler further reduces the temperature of charge air before that air enters the cylinders (not shown) of engine system  10 . 
     Liquid working fluid exiting pre-CAC  52  travels downstream through exhaust conduit  58  to exhaust heat exchanger  56 . Exhaust heat exchanger  56  receives some or all exhaust gas from an upstream aftertreatment system  60 , which is directed to exhaust heat exchanger  56  by aftertreatment conduit  64 , proportional exhaust gas control valve  62  and first exhaust gas conduit  66 . Exhaust gas control valve  62  directs hot exhaust gas through exhaust heat exchanger  56  based on the temperature of exhaust heat exchanger  56 . Temperature sensors may be located in exhaust gas heat exchanger  56 , EGR boiler/superheater  74  or other locations to determine whether exhaust gas heat exchanger  56  is at an appropriate temperature to raise the temperature of the liquid working fluid received from exhaust conduit  58  prior to exiting exhaust gas heat exchanger  56  by way of downstream EGR conduit  76 . Exhaust gas traveling through exhaust heat exchanger  56  travels downstream by way of third exhaust gas conduit  70  to tailpipe or exhaust pipe  72 . To prevent exhaust gas heat exchanger  56  from overheating, exhaust gas control valve  62  can limit the heat load on exhaust gas heat exchanger  56  by diverting some or all exhaust gas around exhaust heat exchanger  56  downstream through second exhaust gas conduit  68  to tailpipe or exhaust pipe  72 . 
     The temperature of the liquid working fluid has been raised three times, first by receiving heat from hot vaporized working fluid in recuperator  44 , second by receiving heat from the turbocharger compressor in pre-CAC  52 , which is downstream of recuperator  44 , and third by receiving heat from exhaust gases in exhaust gas heat exchanger  56 , which is downstream of pre-CAC  52 . The liquid working fluid now travels downstream to inlet  74   d  of EGR boiler/superheater  74  by way of EGR conduit  76 . Exhaust gases exiting the exhaust manifold (not shown) of engine system  10  that are part of an exhaust gas recirculating (EGR) system enter EGR boiler/superheater  74  at EGR inlet  74   a . Exhaust gas from the EGR system flows through EGR boiler/superheater  74 , which may take the place of an EGR cooler. The exhaust gas is cooled in EGR boiler/superheater  74  while transferring heat to the liquid working fluid, causing the liquid working fluid, which has been pre-warmed as previously described, to boil and to produce a high-pressure vapor or gas that exits EGR boiler/superheater  74  at EGR outlet  74   e . The vaporized working fluid then travels downstream via first conversion device conduit  80  to energy conversion device  78 . For simplicity, EGR boiler/superheater  74  may be called EGR boiler  74  or boiler  74  hereinafter. The exhaust gas exits EGR boiler/superheater  74  at EGR outlet  74   b  to return to the EGR system. 
     High-pressure energy conversion device  78  may drive auxiliary device  82 . Auxiliary device  82  can channel mechanical energy into the driveline (not shown) of engine system  10  or can generate electrical energy to power electrical devices or for storage in one or more batteries. If auxiliary device  82  is an electrical generator, the power could power a driveline motor generator (not shown) by way of power electronics (not shown) to help drive a vehicle (not shown) in which engine system  10  is mounted. 
     The vaporized or gaseous working fluid flows downstream through second conversion device conduit  84  to recuperator  44 . As previously noted, the gaseous working fluid entering recuperator  44  from second conversion conduit  84  is relatively hot compared to the liquid working fluid entering recuperator  44  from upstream recuperator conduit  46 . Because recuperator  44  acts as a heat exchanger, heat is transferred from the gaseous working fluid to the liquid working fluid entering recuperator  44  from upstream recuperator conduit  46 . The gaseous working fluid next flows downstream through condenser conduit  88  to condenser  18 . Condenser  18  has cooling air or fluid flowing through it to cool the gaseous working fluid, returning the gaseous working fluid to a liquid state. The working fluid, now returned to a liquid state, flows downstream through fluid passages that may be in base plate  24  to return to sub-cooler  16 . Note that receiver  20  vents by way of receiver vent conduit  86  to condenser conduit  88 , permitting the level of liquid working fluid in receiver  20  to raise and lower as needed. 
     The system described thus far is a Rankine cycle waste heat recovery system or an organic Rankine cycle if the working fluid is an organic high molecular mass fluid with a liquid-vapor phase change that is lower than the water-steam phase change. Examples of Rankine cycle working fluids, organic and inorganic, include Genetron® R-245fa from Honeywell, Therminol®, Dowtherm J™ from Dow Chemical Co., Fluorinol® from American Nickeloid, toluene, dodecane, isododecane, methylundecane, neopentane, neopentane, octane, water/methanol mixtures, or steam. While the system described above may be a Rankine cycle or an organic Rankine cycle, it also presents an opportunity with respect to the exhaust gas recirculation (EGR) system. 
     Current EGR systems are passive devices without the ability to regulate EGR cooler output temperature actively. The present disclosure describes a configuration that provides an ability to regulate EGR outlet temperature by using a partial bypass of recuperator  44  while still maintaining Rankine cycle efficiency and the improved fuel economy yielded by EGR. As previously noted, recuperator  44  provides a heat exchange between gaseous working fluid entering recuperator  44  from upstream second conversion device conduit  84  and liquid working fluid entering recuperator  44  from upstream recuperator conduit  46 . The liquid working fluid then travels downstream to pre-CAC  52 , then to exhaust heat exchanger  56  and then to EGR boiler/superheater  74 , thus gaining the benefits of interfacing with these components. However, a portion of the liquid working fluid bypasses recuperator  44  in a parallel path by way of first boiler control valve conduit  50 , EGR boiler flow control valve  48 , and second boiler control valve conduit  51 . EGR boiler flow control valve  48  may be a proportional valve that permits a portion of the liquid working fluid to bypass recuperator  44 . Alternatively, EGR boiler flow control valve  48  may be modulated to open and close to adjust the amount of liquid working fluid entering second boiler control valve conduit  51 . 
     The liquid working fluid that bypasses recuperator  44  connects downstream to inlet  74   c  of EGR boiler/superheater  74  by way of second boiler control valve conduit  51 . The liquid working fluid that enters EGR boiler/superheater  74  by way of valve conduit  51  goes to low-temperature section  25  of the EGR boiler/superheater  74 , which is also an EGR exhaust gas cooler, to regulate, control or adjust the temperature of the exhaust gas that exits EGR boiler/superheater  74  at EGR outlet  74   b . This regulation is possible because the liquid working fluid entering inlet  74   c  is at a much lower temperature than the liquid working fluid entering EGR boiler/superheater  74  from EGR conduit  76 . The liquid working fluid entering EGR boiler/superheater  74  at EGR inlet  74   c  may be at a much lower temperature than the exhaust gas entering EGR inlet  74   a . Thus, by adjusting the amount of liquid working fluid that enters EGR boiler/superheater  74  by way of second boiler control valve conduit  51 , engine system  10  and waste heat recovery circuit  14  have the capability to regulate, control or adjust the temperature of EGR exhaust gas that enters EGR inlet  74   a  and exits EGR outlet  74   b . The capability of regulating the temperature of EGR exhaust gas is accomplished by changing the flow rate of the coolest liquid working fluid within EGR boiler/superheater  74 . The benefit to the ability to adjust the temperature of the EGR exhaust gas is that increased cooling of EGR exhaust gas when the engine is hot increases the efficiency of the engine and generally leads to lower emissions of NOx from the engine. However, excessive cooling may lead to undesirable condensation, so temperature monitoring within EGR boiler/superheater  74  is important to maintain the temperature of EGR exhaust gas within a functionally useful range. Decreasing cooling of EGR exhaust gas increases engine temperature, which is beneficial when the engine is cold so that the engine reaches an optimal operating temperature more quickly. Decreasing cooling of EGR exhaust gas is also beneficial for thermal management of the aftertreatment system, which includes regeneration of certain elements of the aftertreatment system. 
     Control module  150  may regulate the function of boiler  74 . Control module  150  does this by receiving signals from various temperature sensors and then controlling various valves located in engine system  10 . For example, some situations may require additional heat to cause the liquid working fluid to boil, which control module  150  might determine by receiving a temperature and pressure signal from temperature and pressure sensor  23  located in higher temperature portion  27  of boiler  74 . The temperature and pressure signal from sensor  23  may indicate that the superheat of the vaporized working fluid is lower than a target value. Control module  150  may also read the temperature of EGR exhaust gas entering boiler  74  by receiving a temperature signal from first EGR temperature sensor  15  and using that signal to determine whether additional heat needs applied to the liquid working fluid to increase the superheat of the vaporized working fluid. Control module  150  may then command exhaust gas control valve  62  to increase the amount of exhaust gas flow to exhaust heat exchanger  56  to increase the temperature of the liquid working fluid flowing through conduit  76  to boiler  74 . Control module  150  may also close EGR boiler flow control valve  48  to increase the flow of liquid working fluid through recuperator  44 , pre-CAC  52  and exhaust heat exchanger  56  to increase the amount of heat transferred to the liquid working fluid. Control module  150  may also reduce the flow rate of feed pump  32  or bypass liquid working fluid through feed pump flow valve  34  back to receiver  20 , which results in a decreased flow rate through recuperator  44 , pre-CAC  52 , and exhaust heat exchanger  56 , which increases the temperature of the vaporized working fluid at the inlet of energy conversion device  78 . Control module  150  may also increase the flow of EGR exhaust gas into inlet  74   a  of boiler  74  by modulating an EGR valve (not shown). 
     While vaporization or boiling of the liquid working fluid is an important function of EGR boiler/superheater  74 , EGR boiler/superheater  74  also functions as an EGR cooler. The configuration of boiler  74  allows boiler  74  to boil or vaporize the liquid working fluid while continuing to provide cooling of the EGR exhaust gas. Second EGR temperature sensor  17  may indicate inadequate cooling of EGR exhaust gas as it prepares to exit outlet  74   b  of boiler  74 . Control module  150  may actuate EGR boiler flow control valve  48  upstream of inlet  74   c  to increase the amount of relatively cool liquid working fluid entering inlet  74   c  of boiler  74  into lower temperature portion  25  of boiler  74 . The relatively low temperature of the liquid working fluid provides additional cooling of EGR exhaust gas prior to the EGR exhaust gas returning to the EGR system. Liquid working fluid flows through boiler portion  25  into higher temperature boiler portion  27 , joining with liquid working fluid that enters boiler  74  from inlet  74   d  at junction  29 . The higher temperature of the liquid working fluid entering inlet  74   d  in combination with the temperature of the EGR exhaust gas acts to quickly convert the liquid working fluid into a vapor, which proceeds through outlet  74   e  to conduit  80  and then downstream to energy conversion device  78 . Thus, the configuration of boiler  74  permits EGR boiler  74  to provide cooling to EGR exhaust gas while converting liquid working fluid to a vapor. This same process may also adjust the superheat of the vaporized working fluid by decreasing the temperature and pressure of the vaporized working fluid by taking one or more of the actions described hereinabove. 
     Referring now to  FIG. 2 , an engine system  110  in accordance with a second exemplary embodiment of the present disclosure is shown. Engine system  110  includes a waste heat recovery circuit  114 , fluid management circuit  12 , and a portion of exhaust circuit  11 . Elements in this embodiment having the same number as the first embodiment work as described in the first embodiment and are discussed again only as necessary for clarity. 
     In this embodiment, second boiler control valve conduit  51  connects to an inlet  174   c  of an EGR boiler  174 . Recuperator  44  connects to downstream pre-CAC  52  by a pre-CAC conduit  90 . Connected to and extending downstream from pre-CAC conduit  90  is a third boiler valve conduit  92 . A second EGR boiler flow control valve  94  may connect to third boiler valve conduit  92 . A fourth boiler valve conduit  96  connects second EGR boiler flow control valve  94  to a downstream inlet  174   e  of EGR boiler  174 . Pre-CAC  52  connects downstream to exhaust heat exchanger  56  as described in the previous embodiment, and exhaust circuit  11  is as described in the previous embodiment. Exhaust heat exchanger  56  connects to a downstream inlet  174   d  of EGR boiler  174  by way of EGR conduit  76 . EGR boiler  174  also includes an EGR inlet  174   a  and an EGR outlet  174   b.    
     Engine system  110  includes a control module or control system  250 . Control module  250 , which may be a single processor, a distributed processor, an electronic equivalent of a processor, or any combination of the aforementioned elements, as well as software, electronic storage, fixed lookup tables and the like, is connected to certain components of fluid management circuit  12  and waste heat recovery circuit  114  by a wire harness  135 , though such connection may be by other means, such as a wireless system. 
     Control module  250  connects to fluid level sensor  13  associated with sub-cooler  16 . Control module  250  connects to feed pump flow valve  34 , EGR boiler flow control valve  48 , exhaust gas control valve  62 , and second EGR boiler flow control valve  94 . Control module  250  may connect to feed pump  32 . Control module  250  may also connect to temperature sensors positioned within EGR boiler/superheater  174  or in other locations. Referring to  FIG. 5B , control module  250  may connect to a first EGR temperature sensor  111 , a second EGR temperature sensor  113 , a third EGR temperature sensor  115 , a fourth EGR temperature sensor  117 , a first working fluid temperature sensor  119 , a second working fluid temperature sensor  121 , and a third working fluid temperature sensor  123  and a temperature and pressure sensor  129 . Temperature sensor  117  and temperature sensor  119  may be located in a lower temperature portion  125  of EGR boiler/superheater  174 . Temperature sensor  115  and temperature sensor  121  may be located in a moderate temperature portion  126  of EGR boiler/superheater  174 . Temperature sensor  111 , temperature sensor  113 , temperature sensor  123 , and temperature and pressure sensor  129  may be located in a higher temperature portion  127  of EGR boiler/superheater  174 . 
     The second embodiment is similar in many respects to the first embodiment, with one key difference. In addition to the liquid working fluid that bypasses recuperator  44  and connects downstream to inlet  174   c  of EGR boiler/superheater  174  by way of second boiler control valve conduit  51 , and the liquid working fluid that enters inlet  174   d , liquid working fluid also enters a third inlet  174   e . The liquid working fluid in pre-CAC conduit  90  has a higher temperature than the temperature of the liquid working fluid in conduit  51 , but the temperature of the liquid working fluid in pre-CAC conduit  90  is lower than the temperature of the liquid working fluid in conduit  76 . 
     The benefit to this configuration is that the temperature of the EGR exhaust gas may be adjusted, regulated or cooled with greater precision by having the ability to select from three different liquid working fluid temperatures. The lowest temperature is from second boiler control valve conduit  51 , an intermediate temperature is from fourth boiler valve conduit  96 , and a relatively high temperature is from EGR conduit  76 . Note that all three temperatures might be relatively low in comparison with the EGR exhaust gas entering inlet  174   a . As with the first embodiment, decreasing cooling of EGR exhaust gas increases engine temperature, which is beneficial when the engine is cold so that the engine reaches an optimal operating temperature more quickly. Decreasing cooling of EGR exhaust gas is also beneficial for thermal management of the aftertreatment system, which includes regeneration of certain elements of the aftertreatment system. 
     Note also that while this embodiment contains second EGR boiler control valve  94 , which may be a proportional valve that is adjustable, EGR boiler control valve  94  may be eliminated in some embodiments and replaced with an aperture having a fixed diameter or by using a reduced diameter conduit to restrict flow to inlet  174   e . While this configuration has less flexibility than a configuration using an adjustable valve, a fixed amount of liquid working fluid at an intermediate temperature entering the EGR boiler may be beneficial in regulating the temperature limits of the EGR exhaust gas. 
     Control module  250  may regulate the function of boiler  174 . Control module  250  does this by receiving signals from various temperature sensors and then controlling various valves located in engine system  110 . For example, some situations may require additional heat to cause the liquid working fluid to boil, which control module  250  might determine by receiving a temperature signal from temperature and pressure sensor  129  located in higher temperature portion  127  of boiler  174 . The temperature and pressure signal from sensor  129  may indicate that the superheat is lower than target. Control module  250  may read the temperature of EGR exhaust gas entering boiler  174  by receiving a temperature signal from first EGR temperature sensor  111  and using that signal to determine whether additional heat needs applied to the liquid working fluid. Control module  250  may then command exhaust gas control valve  62  to increase the amount of downstream exhaust gas flow to exhaust heat exchanger  56  to increase the temperature of the liquid working fluid flowing through conduit  76  to boiler  174 . Control module  250  may also close EGR boiler flow control valve  48  to increase the flow of liquid working fluid through recuperator  44 , pre-CAC  52  and exhaust heat exchanger  56  to increase the amount of heat transferred to the liquid working fluid. Control module  250  may also close EGR boiler flow control valve  94  to increase the flow of liquid working fluid through pre-CAC  52  and exhaust heat exchanger  56  to increase the amount of heat transferred to the liquid working fluid. Control module  250  may also reduce the flow rate of feed pump  32  or bypass liquid working fluid through feed pump flow valve  34  back to receiver  20 , which results in a decreased flow rate through recuperator  44 , pre-CAC  52 , and exhaust heat exchanger  56 , which increases heat transferred to the liquid working fluid and increases the temperature of the vaporized working fluid at the inlet of energy conversion device  78 . Control module  250  may also increase the flow of EGR exhaust gas into inlet  174   a  of boiler  174  by modulating an EGR valve (not shown). 
     While vaporization or boiling of the liquid working fluid is an important function of EGR boiler/superheater  174 , EGR boiler/superheater  174  also functions as an EGR cooler. The configuration of boiler  174  allows boiler  174  to boil or vaporize the liquid working fluid while continuing to provide cooling of the EGR exhaust gas. Second EGR temperature sensor  115  and third EGR temperature sensor  117  may indicate inadequate cooling of EGR exhaust gas as it travels through moderate temperature section  126  and low temperature section  125  of boiler  174  as the EGR exhaust gas travels through boiler  174  and then prepares to exit outlet  174   b  of boiler  174 . Control module  250  may actuate EGR boiler flow control valve  48  to increase the amount of relatively cool liquid working fluid entering inlet  174   c  of boiler  174  into lower temperature portion  125  of boiler  174 . The relatively low temperature of the liquid working fluid entering lower temperature portion  125 , measured by temperature sensor  119 , provides additional cooling of EGR exhaust gas prior to the EGR exhaust gas returning to the EGR system. Liquid working fluid flows through boiler portion  125  into moderate temperature portion  126 , joining with liquid working fluid that entered boiler  174  from inlet  174   e  at junction  131 . The temperature of the liquid working fluid entering inlet  174   e , measured by temperature sensor  121 , provides some cooling of the EGR exhaust gas prior to the EGR exhaust gas traveling to low temperature portion  125 . The liquid working fluid continues to gain heat as it travels through moderate temperature portion  126 . The liquid working fluid then travels into higher temperature boiler portion  127 , joining with liquid working fluid that enters boiler  174  from inlet  174   d  at junction  133 . The higher temperature of the liquid working fluid entering inlet  174   d , measured by temperature sensor  123 , in combination with the temperature of the EGR exhaust gas acts to quickly convert the liquid working fluid into a vapor, which proceeds through outlet  174   f  to conduit  80  and then downstream to energy conversion device  78 . The various temperature sensors in combination with the various valves of the system regulate the amount of cooling provided to EGR exhaust gas as it travels through the various portions of boiler  174  while regulating the amount of heating provided to the liquid working fluid, thus improving the amount of cooling provided to the EGR exhaust gas while assuring the liquid working fluid vaporizes. 
     As with the previous embodiment, the superheat of the vaporized working fluid needs to be within a targeted range in order to optimize performance of WHR system  110 . Adjusting the opening of the valves described hereinabove and taking the actions described hereinabove adjusts the temperature of the liquid working fluid, which also affects the superheat of the vaporized working fluid. Thus, if superheat needs reduced, heat transfer to the liquid working fluid is reduced, or for a given heat input, the flow rate to the heat exchangers is increased by reducing the amount of feed pump bypass valve  34 . If superheat needs increased, heat transfer to the liquid working fluid is increased, or for a given heat input, the flow rate to the heat exchangers is reduced by bypassing increased flow rate at the feed pump bypass valve  34 . 
     Referring now to  FIG. 3 , an engine system  210  in accordance with a third exemplary embodiment of the present disclosure is shown. An engine system  210  includes a waste heat recovery circuit  214 , fluid management circuit  12 , and a portion of exhaust circuit  11 . Elements in this embodiment having the same number as the first embodiment work as described in the first embodiment and are discussed again only as necessary for clarity. 
     In this embodiment, second boiler control valve conduit  51  connects to an inlet  274   c  of an EGR boiler/superheater  274 . Recuperator  44  connects downstream to exhaust cooler  56  by an exhaust conduit  98 . Connected to and extending downstream from exhaust conduit  98  is a third boiler valve conduit  100 . A second EGR boiler flow control valve  102  may connect to third boiler valve conduit  100 . A fourth boiler valve conduit  104  connects second EGR boiler flow control valve  102  to a downstream inlet  274   e  of EGR boiler  274 . Heat exchanger  56  is as described in the first exemplary embodiment, and exhaust circuit  11  is as described in the first exemplary embodiment. Exhaust heat exchanger  56  connects to an inlet  274   d  of EGR boiler  274  by way of EGR conduit  76 . EGR boiler  274  also includes an EGR inlet  274   a  and an EGR outlet  274   b.    
     Engine system  210  includes a control module or control system  350 . Control module  350 , which may be a single processor, a distributed processor, an electronic equivalent of a processor, or any combination of the aforementioned elements, as well as software, electronic storage, fixed lookup tables and the like, is connected to certain components of fluid management circuit  12  and waste heat recovery circuit  214  by a wire harness  235 , though such connection may be by other means, such as a wireless system. 
     Control module  350  connects to fluid level sensor  13  associated with sub-cooler  16 . Control module  350  connects to feed pump flow valve  34 , EGR boiler flow control valve  48  and EGR boiler flow control valve  102 . Control module  350  may connect to feed pump  32 . Control module  350  may also connect to temperature sensors positioned within EGR boiler/superheater  274  or in other locations. Referring to  FIG. 5C , control module  350  may connect to a first EGR temperature sensor  211 , a second EGR temperature sensor  213 , a third EGR temperature sensor  215 , a fourth EGR temperature sensor  217 , a first working fluid temperature sensor  219 , a second working fluid temperature sensor  221 , a third working fluid temperature sensor  223  and a temperature and pressure sensor  229 . Temperature sensor  217  and temperature sensor  219  may be located in a lower temperature portion  225  of EGR boiler/superheater  274 . Temperature sensor  215  and temperature sensor  221  may be located in a moderate temperature portion  226  of EGR boiler/superheater  274 . Temperature sensor  211 , temperature sensor  213 , temperature sensor  223 , and temperature and pressure sensor  229  may be located in a higher temperature portion  227  of EGR boiler/superheater  274 . 
     The third embodiment operates similarly in many respects to the second embodiment, with one key difference. In this embodiment, there is no pre-charge air cooler. However, any heat transfer to the working fluid lost in the elimination of a pre-charge air cooler may be offset by increasing heat transfer in exhaust heat exchanger  56  or in EGR boiler  274 , if increased heat transfer is necessary or desirable. As with the second embodiment, in addition to the liquid working fluid that bypasses recuperator  44  and connects downstream to inlet  274   c  of EGR boiler/superheater  274  by way of second boiler control valve conduit  51  and the liquid working fluid that enters inlet  274   d , liquid working fluid also enters a third inlet  274   e . The liquid working fluid in fourth boiler valve conduit  104  has a higher temperature than the temperature of the liquid working fluid in conduit  51 , but the temperature of the liquid working fluid in fourth boiler valve conduit  104  is lower than the temperature of the liquid working fluid in conduit  76 . The benefit to this configuration is that the temperature of the EGR exhaust gas may be adjusted, regulated or cooled with greater precision by having the ability to select from three different liquid working fluid temperatures. The lowest temperature is from second boiler control valve conduit  51 , an intermediate temperature is from fourth boiler valve conduit  104 , and a relatively high temperature is from EGR conduit  76 . Note that all three temperatures might be relatively low in comparison with the temperature of EGR exhaust gas entering inlet  274   a . As with the first embodiment, decreasing cooling of EGR exhaust gas increases engine temperature, which is beneficial when the engine is cold so that the engine reaches an optimal operating temperature more quickly. Decreasing cooling of EGR exhaust gas is also beneficial for thermal management of the aftertreatment system, which includes regeneration of certain elements of the aftertreatment system. 
     Control module  350  may regulate the function of boiler  274 . Control module  350  does this by receiving signals from various temperature sensors and then controlling various valves located in engine system  210 . For example, some situations may require additional heat to cause the liquid working fluid to boil, which control module  350  might determine by receiving a temperature signal from temperature and pressure sensor  229  located in higher temperature portion  227  of boiler  274 . The temperature and pressure signal from sensor  229  may indicate that the superheat is lower than target. Control module may read the temperature of EGR exhaust gas entering boiler  274  by receiving a temperature signal from first EGR temperature sensor  211  and using that signal to determine whether additional heat needs applied to the liquid working fluid. Control module  350  may then command exhaust gas control valve  62  to increase the amount of downstream exhaust gas flow to exhaust heat exchanger  56  to increase the temperature of the liquid working fluid flowing through conduit  76  to boiler  274 . Control module  350  may also close EGR boiler flow control valve  48  to increase the flow of liquid working fluid through recuperator  44  and exhaust heat exchanger  56  to increase the amount of heat transferred to the liquid working fluid. Control module  350  may also close EGR boiler flow control valve  102  to increase the flow of liquid working fluid through exhaust heat exchanger  56  to increase the amount of heat transferred to the liquid working fluid. Control module  350  may also reduce the flow rate of feed pump  32  or bypass liquid working fluid through feed pump flow valve  34  back to receiver  20 , which results in a decreased flow rate through recuperator  44  and exhaust heat exchanger  56 , which increases heat transferred to the liquid working fluid. Control module  350  may also increase the flow of EGR exhaust gas into inlet  274   a  of boiler  274  by modulating an EGR valve (not shown). 
     While vaporization or boiling of the liquid working fluid is an important function of EGR boiler/superheater  274 , EGR boiler/superheater  274  also functions as an EGR cooler. The configuration of boiler  274  allows boiler  274  to boil or vaporize the liquid working fluid while continuing to provide cooling of the EGR exhaust gas. Second EGR temperature sensor  215  and third EGR temperature sensor  217  may indicate inadequate cooling of EGR exhaust gas as it travels through moderate temperature section  226  and low temperature section  225  of boiler  274  as the EGR exhaust gas travels through boiler  274  and then prepares to exit outlet  274   b  of boiler  274 . Control module  350  may actuate EGR boiler flow control valve  48  to increase the amount of relatively cool liquid working fluid entering inlet  274   c  of boiler  274  into lower temperature portion  225  of boiler  274 . The relatively low temperature of the liquid working fluid entering lower temperature portion  225 , measured by temperature sensor  219 , provides additional cooling of EGR exhaust gas prior to the EGR exhaust gas returning to the EGR system. Liquid working fluid flows through low temperature portion  225  into moderate temperature portion  226 , joining with liquid working fluid that enters boiler  274  from inlet  274   e  at a junction  231 . The temperature of the liquid working fluid entering inlet  274   e , measured by temperature sensor  221 , provides some cooling of the EGR exhaust gas prior to the EGR exhaust gas traveling to low temperature portion  225 . The liquid working fluid continues to gain heat as it travels downstream through moderate temperature portion  226 . The liquid working fluid then travels into higher temperature boiler portion  227 , joining with liquid working fluid that enters boiler  274  from inlet  274   d  at junction  233 . The higher temperature of the liquid working fluid entering inlet  274   d , measured by temperature sensor  223 , in combination with the temperature of the EGR exhaust gas entering boiler  274  at inlet  274   a , acts to quickly convert the liquid working fluid into a vapor, which proceeds through outlet  274   f  to conduit  80  and then downstream to energy conversion device  78 . The various temperature sensors in combination with the various valves of the system regulate the amount of cooling provided to EGR exhaust gas as it travels through the various portions of boiler  274  while regulating the amount of heating provided to the liquid working fluid, thus improving the amount of cooling provided to the EGR exhaust gas while assuring the liquid working fluid vaporizes. 
     As with the previous embodiment, the superheat of the vaporized working fluid needs to be within a targeted range in order to optimize performance of WHR system  210 . Adjusting the opening of the valves described hereinabove and taking the actions described hereinabove adjusts the temperature of the liquid working fluid, which also affects the superheat of the vaporized working fluid. Thus, if superheat needs reduced, heat transfer to the liquid working fluid is reduced. If superheat needs increased, heat transfer to the liquid working fluid is increased. 
     Referring now to  FIG. 4 , an engine system  310  in accordance with a fourth exemplary embodiment of the present disclosure is shown. Engine system  310  includes a waste heat recovery circuit  314 , fluid management circuit  12 , and a portion of exhaust circuit  11 . Elements in this embodiment having the same number as previous embodiments work as described in the first embodiment and are discussed again only as necessary for clarity. 
     In this embodiment, second boiler control valve conduit  51  connects to an inlet  374   c  of an EGR boiler  374 . Recuperator  44  connects to downstream pre-CAC  52  by a pre-CAC conduit  90 . Connected to and extending upstream from pre-CAC conduit  90  is a third boiler valve conduit  97 . A second EGR boiler flow control valve  99  may connect to third boiler valve conduit  97 . A fourth boiler valve conduit  101  connects second EGR boiler flow control valve  94  to an upstream outlet  374   e  of EGR boiler  374 . Pre-CAC  52  connects downstream to exhaust heat exchanger  56  as described in the previous embodiment, and exhaust circuit  11  is as described in the first two embodiments. Exhaust heat exchanger  56  connects to a downstream inlet  374   d  of EGR boiler  374  by way of EGR conduit  76 . EGR boiler  374  also includes an EGR inlet  374   a  and an EGR outlet  374   b.    
     Engine system  310  includes a control module or control system  250 . Control module  450 , which may be a single processor, a distributed processor, an electronic equivalent of a processor, or any combination of the aforementioned elements, as well as software, electronic storage, fixed lookup tables and the like, is connected to certain components of fluid management circuit  12  and waste heat recovery circuit  314  by a wire harness  335 , though such connection may be by other means, such as a wireless system. 
     Control module  450  connects to fluid level sensor  13  associated with sub-cooler  16 . Control module  450  connects to feed pump flow valve  34 , EGR boiler flow control valve  48 , exhaust gas control valve  62 , and second EGR boiler flow control valve  99 . Control module  450  may connect to feed pump  32 . Control module  450  may also connect to temperature sensors positioned within EGR boiler/superheater  374  or in other locations. Referring to  FIG. 5B , control module  450  may connect to a first EGR temperature sensor  111 , a second EGR temperature sensor  113 , a third EGR temperature sensor  115 , a fourth EGR temperature sensor  117 , a first working fluid temperature sensor  141 , a second working fluid temperature sensor  143 , a third working fluid temperature sensor  145 , a fourth working fluid temperature sensor  147 , and a temperature and pressure sensor  149 . Temperature sensor  117  and temperature sensor  141  may be located in a lower temperature portion  153  of EGR boiler/superheater  374 . Temperature sensor  115 , temperature sensor  143 , and temperature sensor  145  may be located in a moderate temperature portion  154  of EGR boiler/superheater  374 . Temperature sensor  111 , temperature sensor  113 , temperature sensor  147 , and temperature and pressure sensor  149  may be located in a higher temperature portion  154  of EGR boiler/superheater  374 . 
     The fourth embodiment is similar in many respects to the second embodiment, with one key difference. The liquid working fluid that bypasses recuperator  44  and connects downstream to inlet  374   c  of EGR boiler/superheater  374  by way of second boiler control valve conduit  51  exits outlet  374   e  of EGR boiler/superheater  374 . 
     The benefit to this configuration is that the temperature of the EGR exhaust gas may be adjusted, regulated or cooled with greater precision by having the ability to select from two different liquid working fluid temperatures while subjecting the cooler liquid working fluid to additional heat in Pre-CAC  52  and exhaust heat exchanger  56  prior to the liquid working fluid entering high temperature portion  154  of EGR boiler  374 . As with the first embodiment, decreasing cooling of EGR exhaust gas increases engine temperature, which is beneficial when the engine is cold so that the engine reaches an optimal operating temperature more quickly. Decreasing cooling of EGR exhaust gas is also beneficial for thermal management of the aftertreatment system, which includes regeneration of certain elements of the aftertreatment system. 
     Note also that while this embodiment contains second EGR boiler control valve  99 , which may be a proportional valve that is adjustable, EGR boiler control valve  99  may be eliminated in some embodiments. 
     Control module  450  may regulate the function of boiler  374 . Control module  450  does this by receiving signals from various temperature sensors and then controlling various valves located in engine system  310 . For example, some situations may require additional heat to cause the liquid working fluid to boil, which control module  450  might determine by receiving a temperature signal from temperature and pressure sensor  149  located in higher temperature portion  154  of boiler  374 . The temperature and pressure signal from sensor  149  may indicate that the superheat is lower than target. Control module  450  may read the temperature of EGR exhaust gas entering boiler  374  by receiving a temperature signal from first EGR temperature sensor  111  and using that signal to determine whether additional heat needs applied to the liquid working fluid. Control module  450  may then command exhaust gas control valve  62  to increase the amount of downstream exhaust gas flow to exhaust heat exchanger  56  to increase the temperature of the liquid working fluid flowing through conduit  76  to boiler  374 . Control module  450  may also close EGR boiler flow control valve  48  to increase the flow of liquid working fluid through recuperator  44 , pre-CAC  52  and exhaust heat exchanger  56  to increase the amount of heat transferred to the liquid working fluid. Control module  450  may also adjust the flow through EGR boiler  374  by adjusting EGR boiler flow control valve  99 . Control module  450  may also reduce the flow rate of feed pump  32  or bypass liquid working fluid through feed pump flow valve  34  back to receiver  20 , which results in a decreased flow rate through recuperator  44 , pre-CAC  52 , and exhaust heat exchanger  56 , which increases heat transferred to the liquid working fluid. Control module  450  may also increase the flow of EGR exhaust gas into inlet  374   a  of boiler  374  by modulating an EGR valve (not shown). 
     While vaporization or boiling of the liquid working fluid is an important function of EGR boiler/superheater  374 , EGR boiler/superheater  374  also functions as an EGR cooler. The configuration of boiler  374  allows boiler  374  to boil or vaporize the liquid working fluid while improving cooling of the EGR exhaust gas. Second EGR temperature sensor  115  and third EGR temperature sensor  117  may indicate inadequate cooling of EGR exhaust gas as it travels through moderate temperature section  154  and low temperature section  153  of boiler  374  as the EGR exhaust gas travels through boiler  374  and then prepares to exit outlet  374   b  of boiler  374 . Control module  450  may actuate EGR boiler flow control valve  48  to increase the amount of relatively cool liquid working fluid entering inlet  174   c  of boiler  174  into lower temperature portion  153  of boiler  374 . The relatively low temperature of the liquid working fluid entering lower temperature portion  153 , measured by temperature sensor  141 , provides additional cooling of EGR exhaust gas prior to the EGR exhaust gas returning to the EGR system. Liquid working fluid flows through boiler portion  153  into moderate temperature portion  154 , exiting EGR boiler  374  at outlet  374   e . The temperature of the liquid working fluid flowing through low temperature portion  153  and moderate temperature portion  154  may be monitored with temperature sensor  143  and temperature sensor  145 , which assists control module  450  in determining the additional cooling capability of the liquid working fluid as well as the additional heat that needs transferred to the liquid working fluid to boil. After passing through pre-CAC  52  and exhaust heat exchanger  56 , the liquid working fluid enters EGR boiler  374  at inlet  374   d . The higher temperature of the liquid working fluid entering inlet  374   d , measured by temperature sensor  147 , in combination with the temperature of the EGR exhaust gas acts to quickly convert the liquid working fluid into a vapor, which proceeds through outlet  374   f  to conduit  80  and then downstream to energy conversion device  78 . The various temperature sensors in combination with the various valves of the system regulate the amount of cooling provided to EGR exhaust gas as it travels through the various portions of boiler  374  while regulating the amount of heating provided to the liquid working fluid, thus improving the amount of cooling provided to the EGR exhaust gas while assuring the liquid working fluid vaporizes. 
     As with the previous embodiment, the superheat of the vaporized working fluid needs to be within a targeted range in order to optimize performance of WHR system  310 . Adjusting the opening of the valves described hereinabove and taking the actions described hereinabove adjusts the temperature of the liquid working fluid, which also affects the superheat of the vaporized working fluid. Thus, if superheat needs reduced, heat transfer to the liquid working fluid is reduced. If superheat needs increased, heat transfer to the liquid working fluid is increased. 
     While various embodiments of the disclosure have been shown and described, it is understood that these embodiments are not limited thereto. The embodiments may be changed, modified and further applied by those skilled in the art. Therefore, these embodiments are not limited to the detail shown and described previously, but also include all such changes and modifications.