Abstract:
A heat recovery system for an engine is disclosed herein utilizing a heat storage unit configured to store waste exhaust heat for subsequent use on engine starts in various systems. In this way, improved system operation can be obtained by re-using such waste heat.

Description:
BACKGROUND AND SUMMARY 
       [0001]    Vehicles may recover exhaust heat for transfer to various other systems in an internal combustion engine. 
         [0002]    The inventors herein have recognized various issues with such systems in that the available packaging space for storing waste heat is limited, and further suitable coordination among various vehicle components is lacking. As such, one example approach to address the above issues is, claim  1 . 
         [0003]    It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIGS. 1A-1B  schematically show an example heat storage device that may be included in an exhaust system. 
           [0005]      FIG. 1C  schematically shows an example heat exchanger that may be coupled to the heat storage device of  FIGS. 1A-1B . 
           [0006]      FIG. 2  schematically shows an example heat recovery system including the heat storage device of  FIGS. 1A-1B . 
           [0007]      FIG. 3  schematically shows an example method for operating the heat recovery system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    The following description relates to a heat storage device of a heat transfer system including phase changing materials, which are arranged in such a way that thermal energy from an exhaust system can be recovered. The example arrangements described herein allow thermal energy to be recovered and stored for later heating of a passenger compartment, for example. 
         [0009]    As indicated, the heat transfer system may utilize a heat storage device to transfer heat even when the engine is not in operation. For example, the heat storage device may be in fluidic communication with an exhaust system component downstream from the catalytic converter, such as via heat exchanger. In this way, heat may transfer from the heat storage device even after the engine is no longer in operation. For example, the heat storage device may be insulated to store heat recovered from the exhaust system, which may be available for immediate use at engine start. 
         [0010]    Additionally, the heat transfer system may include various heat transfer fluids to extract thermal energy from the exhaust system under a variety of different operating conditions. In this way, thermal energy may be recovered from the exhaust system to provide heat to various other systems such as a cabin heating system, lubrication systems, and/or other exhaust system components, if desired. 
         [0011]    Further, the example systems allow for a simpler and more compact design as compared to traditional designs. For example, the heat storage device may provide heat to a cabin heating system at engine start, as introduced above. By coupling the heat storage device to a component of the exhaust system downstream from the catalytic converter, the cabin heating system may provide heat to the passenger cabin at engine start without relying upon a coolant system, and therefore, without waiting for the coolant system to warm up at engine start. Further, the system may provide the stored heat to the cabin heating system without delaying catalytic converter light-off, as described above. 
         [0012]      FIGS. 1A and 1B  show a heat storage device  100  according to an embodiment of the present disclosure.  FIG. 1A  shows a perspective exterior view and  FIG. 1B  shows a perspective cross sectional view of heat storage device  100  taken along plane B.  FIG. 1  shows an example bypass heat exchanger that may be coupled to heat storage device  100 . 
         [0013]    Referring first to  FIG. 1A , heat storage device  100  may be a cylindrical shape. In other words, heat storage device  100  may have a circular cross section. Further, heat storage device  100  may be tilted by an angle  101  from a horizontal. Such an angle may facilitate efficient heat transfer through the device. As used herein, the horizontal refers to the ground over which the vehicle travels. For example,  FIG. 1A  shows a horizontal axis  102  and a vertical axis  104 . The vertical axis may be orthogonal to the horizontal axis. Therefore, the vertical axis may be orthogonal to the ground over which the vehicle travels. As shown, heat storage device  100  may be tilted angle  101  from horizontal axis  102 . In some embodiments, heat storage device  100  may be tilted 5° from the horizontal; however, it will be appreciated that other angles are possible without departing from the scope of this disclosure. Further, in some embodiments, heat storage device  100  may not be tilted. For example, heat storage device  100  may be level with the horizontal. In other words, angle  101  may be zero degrees. 
         [0014]    As shown, heat storage device  100  includes an inlet passage  106  and an outlet passage  108 . The inlet and outlet passages may carry a heat transfer fluid. Further, the heat storage device may house a phase changing material (PCM). 
         [0015]    Inlet passage  106  may be coupled to heat storage device  100  at a central position. For example, inlet passage  106  may be coupled to a first end  110  of heat storage device  100  at the central position. In other words, inlet passage  106  may have a central axis  112  that is shared with a central axis of end  110 , and further, shared with a central axis of heat storage device  100 . Inlet passage  106  may be configured to supply heat storage device  100  with heat recovered from the exhaust system, for example. In some embodiments, the heat transfer fluid of inlet passage  106  may be coupled to a pump (not shown) to drive a movement of the heat transfer fluid. Further, a bypassable heat exchanger may be positioned upstream from inlet passage  106 . Such a heat exchanger is discussed further with reference to  FIG. 1C . Further, inlet passage  106  may include a portion that extends into an interior  114  of heat storage device  100 . 
         [0016]    Outlet passage  108  may be coupled to heat storage device  100  at a top position. For example, outlet passage  108  may be coupled to a second end  116  of heat storage device  100  at the top position. In other words, outlet passage  108  may have a central axis  118  that is a distance  120  from shared central axis  112  in a vertical direction (e.g., along vertical axis  104 ). In this way, outlet passage  108  is positioned towards a periphery of end  116 , rather than centrally located, to advantageously reduce bubble accumulation in the heat transfer fluid. However, in some embodiments, outlet passage  108  may be centrally located at end  116 , if desired. Outlet passage  108  may be configured to transfer heat from heat storage device  100  to another system of the vehicle. For example, outlet passage  108  may transfer stored heat to the cabin heating system, the coolant system, the lubrication system, and/or another system of the vehicle. Further, outlet passage  108  may include a portion that extends into the interior  114  of heat storage device  100 . 
         [0017]    As shown, heat storage device  100  includes a vacuum passage  122 . For example, vacuum passage  122  may be coupled to heat storage device  100  at end  116 . Vacuum passage  122  may be coupled to both heat storage device  100  and a vacuum pump (not shown). For example, in some embodiments, heat storage device  100  may include a vacuum jacket, and vacuum passage  122  may be a conduit for evacuating an airspace within the vacuum jacket. In this way, a pressure within at least a portion of interior  114  may be reduced. In some embodiments, the pressure within interior  114  may be reduced to 1 microbar or less. 
         [0018]      FIG. 1B  shows a perspective interior view of heat storage device  100 . As shown, heat storage device  100  may be double walled. In other words, heat storage device  100  may include an outer vessel  124  and an inner vessel  126 . For example, heat storage device may include outer walls  128  and inner walls  130 . Further, heat storage device may include vacuum jacket  132  positioned between outer walls  128  and inner walls  130 . As described above, vacuum passage  122 , along with a vacuum pump, may suction air out of vacuum jacket  132  such that a pressure within vacuum jacket  132  is reduced. 
         [0019]    Vacuum jacket  132  may hold a reduced pressure around an exterior of inner vessel  126  when a vacuum is applied. By applying a vacuum, water vapor and other gaseous compounds can be evacuated from the surfaces of the insulating layers as hot fluid is pumped through the heat transfer fluid passages. Further, vacuum jacket  132  may include one or more anti-radiation foils  134  that reduce heat loss to the surrounding environment via radiation. 
         [0020]    It will be appreciated that the perspective view of  FIG. 1B  shows a longitudinal cross section of the heat storage device  100 , thus it will be appreciated that outer walls  128 , inner walls  130 , and vacuum jacket  132  extend circumferentially around a perimeter of heat storage device  100  and longitudinally, for example, along axis  112 . 
         [0021]    Further, at least a portion of inlet passage  106  and outlet passage  108  may be double walled and include a vacuum space. For example, portions  136  exterior to heat storage device  100  may be double walled similar to the inner and outer vessels. Further, vacuum spaces  138  of the inlet and outlet passages may coalesce with vacuum jacket  132  of the heat storage device. 
         [0022]    Heat storage device  100  may include one or more axial supports  140 . Axial supports  140  may couple inner vessel  126  to outer vessel  124  such that the inner vessels is suspended and supported within the outer vessel. As shown, axial supports  140  may be coupled to outer walls  128  and inner walls  130 , and thus, may be positioned within vacuum jacket  132 . The axial supports may be composed of a material with low heat conducting properties. For example, axial supports  140  may be composed of titanium or a composite including titanium or another material with low heat conducting properties. Further, in some embodiments the axial supports may be perforated to further reduce heat loss to the surrounding environment. 
         [0023]    Further, the inner vessel may be additionally and/or alternatively supported by radial supports  142 . Such radial supports may be located circumferentially at various positions. As shown, radial supports  142  may be coupled to outer walls  128  and inner walls  130 , and thus, may be positioned within vacuum jacket  132 . Similar to the axial supports, the radial supports  142  may be composed of titanium or a composite including titanium or another material with low heat conducting properties. Further, in some embodiments the radial supports may be perforated to further reduce heat loss to the surrounding environment. 
         [0024]    As shown, heat storage device  100  includes two axial supports at end  110 , one axial support at end  116 , and four radial supports  142 . It will be appreciated that the number of axial and radial supports shown is non-limiting and another number of supports and/or another configuration of supports is possible without departing from the scope of this disclosure. The supports are provided to illustrate a general concept of a configuration enabling heat storage device  100  to withstand gravitational acceleration forces that may occur when the heat storage device  100  is rigidly coupled to the vehicle body. 
         [0025]    Heat storage device  100  may further include a phase changing material (PCM) stack  144  supported between retention plates  146  via one or more springs  148 . PCM stack  144  may include a plurality of PCM elements  150  arranged radially about a central feed passage  152 . In some embodiments, the configuration of the PCM stack is such that the PCM stack retains 80% of stored heat for at least 16 hours, which may be used as a heat source at engine start to heat the passenger cabin, as described above. Further, heat stored in PCM stack  144  may be discharged to heat the passenger cabin or another engine system without starting the engine. For example, PCM stack discharge may be initiated remotely and does not necessarily have to coincide with engine-start. However, PCM stack discharge may be initiated remotely along with engine-start, for example, using a remote starter to start engine  12 . 
         [0026]    The plurality of PCM elements  150  include a phase changing material capable of storing a large quantity of heat in a form of a latent heat of fusion. Since the plurality of PCM elements  150  are surrounded by the double wall configuration, heat storing capabilities are enhanced. In other words, the double wall configuration acts like a thermos to retain heat stored within the plurality of PCM elements  150 . In some embodiments, each PCM element may include the same phase changing material, and thus, the PCM stack may have one phase transfer temperature. In other embodiments, the PCM stack may include PCM elements with different phase changing materials, wherein each different phase changing material has a different phase transfer temperature. In such an example, a time to charge the PCM stack may be reduced. In other words, the time for the PCM stack to reach a maximum heat storing potential may be reduced. 
         [0027]    As shown, heat transfer fluid may be delivered to PCM stack  144  via centrally located inlet passage  106 , and further, via center feed passage  152 . Thus, it will be appreciated that inlet passage  106  is in fluidic communication with center feed passage  152 . Thus, heat transfer fluid flows radially from center feed passage  152  to the plurality of PCM elements  150 . Heat transfer fluid exits the heat storage device via outlet passage  108  arranged in the top position, as described above. 
         [0028]    As the heat transfer fluid flows through the PCM stack, a pressure drop occurs. To reduce the pressure drop, the inlet passage  106  and the outlet passage  108  are straight. In other words, the inlet passage  106  and the outlet passage  108  do not include bends. Further, the inlet passage  106  and the outlet passage  108  do not include corrugations. Due to the absence of corrugations, a rate of heat loss may potentially increase. However, since the inlet and outlet passages include a vacuum space around a circumference of these passages, such a potential for heat loss is reduced. 
         [0029]    As shown, retention plates  146  may be positioned at either end of PCM stack  144 . For example, one retention plate  146  may be positioned proximate to end  110 , and another retention plate  146  may be positioned proximate to end  116 . Retention plates  146  may be a circular shape and may have a diameter that is approximately equal to a diameter of PCM stack  144 . As another example, retention plates  146  may have a larger diameter or a smaller diameter than PCM stack  144 . The retention plates may be coupled to the inner vessel via one or more plate extensions with windows  154  to allow HTF to reach exit  108 . Six axial rods (not shown) allow retention of the PCM stack in the radial and circumferential directions. The rods are welded to the retention plates. As such, the PCM stack is retained inside inner vessel  126  to reduce the potential for stack element sliding and/or rotation during vehicle operation. 
         [0030]    Further, one or more springs  148  may further maintain the position of the PCM stack. As shown, one or more springs  148  may be positioned proximate to end  116  between retention plate  146  and inner walls  130 . Springs  148  may be configured to ensure proper contact between the PCM elements during thermal expansion and thermal compression that results from the heat transfer fluid heating and cooling. In some embodiments, springs  148  may have a combined force of 100 Newtons or higher to maintain proper contact between the PCM elements. As shown in  FIG. 1B , heat storage device  100  may include five springs; however the heat storage device may include more than five springs or less than five springs, if desired. 
         [0031]      FIG. 1C  schematically shows a heat exchanger  156  thermally coupled to exhaust passage  14 . In some embodiments, heat exchanger  156  may be thermally coupled to exhaust passage  14  at a position between engine  12  and one or more exhaust emission control devices  16 . For example, heat exchanger  156  may be thermally coupled to exhaust passage  14  upstream from an oxidation catalyst such as a diesel oxidation catalyst (DOC). Heat exchanger  156  may be fluidically coupled to heat storage device  100  via inlet passage  106 . For example, heat exchanger  156  may be thermally coupled to inlet passage  106  at a position upstream from heat storage device  100 . In some embodiments, heat exchanger  156  may be an evaporative region to extract heat from heat passage  14  and provide said heat to heat storage device  100  by way of inlet passage  106 . For example, heat exchanger  156  may include heat transfer tubing that carries heat transfer fluid supplied by an engine-driven pump to flow inside the tubing. As another example, the heat transfer tubing may carry heat transfer fluid supplied by an electrically-driven pump to flow inside the tubing. Such a configuration of heat transfer tubing may be fluidically coupled to inlet passage  106 . As one example, the heat transfer fluid of the tubing may be the same heat transfer fluid of inlet passage  106 . As another example, the heat transfer fluid of the tubing may be a different fluid than the heat transfer fluid of inlet passage  106 . 
         [0032]    In some embodiments, heat exchanger  156  is a liquid-to-liquid heat exchanger. In other embodiments, the heat exchanger  156  could be a gas-to-liquid or gas-to-thermosyphon heat exchanger. 
         [0033]    Further, exhaust passage  14  may include a bypass valve  158  that directs exhaust gas flow through heat exchanger  156 . Bypass valve  158  is shown in a bypass position (e.g., a closed position) in  FIG. 1C . Bypass valve  158  may be actuated via a controller, or bypass valve  158  may be a passive valve, if desired. Bypass valve  158  may be in an open position (e.g., exhaust gases are not diverted to heat exchanger  156 ) when exhaust back pressure reaches a threshold value. For example, bypass valve  158  may be closed at high exhaust flows and/or high exhaust temperatures. As such, bypass valve  158  may reduce loss of engine output, and therefore, may reduce fuel consumption. 
         [0034]    It will be appreciated that the disclosed system may include more than one heat exchanger. For example, a heat exchanger may be positioned upstream from inlet passage  106 , and one or more heat exchangers may be positioned downstream from outlet passage  108 . For example, a heat exchanger may be positioned at an interface between the heat recovery system and another system of the vehicle. Such a configuration is described in further detail with respect to  FIG. 2 . 
         [0035]    It will be appreciated that  FIGS. 1A-1C  are shown in simplified form and that numerous variations are possible without departing from the scope of this disclosure. Further, heat storage device  100  may include additional and/or alternative components than those illustrated in  FIGS. 1A and 1B . Further still, it is to be understood that heat storage device  100  is provided to illustrate a general concept, and thus, numerous geometric configurations are possible without departing from the scope of this disclosure. 
         [0036]      FIG. 2  schematically shows a heat recovery system  200  including heat storage device  100  and a plurality of heat exchangers.  FIG. 2  includes similar features as  FIG. 1 , and like features are indicated with common reference numbers. Such features will not be discussed repetitively for the sake of brevity. 
         [0037]    As shown, heat recovery system  200  includes heat exchanger  156  to recover heat from exhaust system  10 , as described above. Heat recovery system  200  may further include one or more additional heat exchangers  202 . Heat exchangers  202  may transfer heat between heat recovery system  200  and another engine system  203 . For example, heat exchangers  202  may transfer heat to coolant system  204 , cabin heating system  228 , and/or transmission system  206 . In other words, heat exchangers  202  may be thermally coupled (e.g., in thermal contact) with a fluid of the coolant system  204 , the cabin heating system  228  and/or the transmission system  206  to transfer heat to each respective system. 
         [0038]    It will be appreciated that each of the engine systems  203  are separate systems from heat recovery system  200  and exhaust system  10 . As such, engine systems  203  include components that are separate from the components of heat recovery system  200  and exhaust system  10 . Thus, engine systems  203  do not include heat exchanger  156 , heat exchangers  202 , heat storage device  100 , or another component of heat recovery system  200  and exhaust system  10 . For example, cabin heating system  228  may include a heater core and a fan, wherein the heater core and the fan are separate from the heat recovery system and the exhaust system. Thus it is to be understood that only a fluid conduit (e.g., a coolant passage) of each engine system  203  is in thermal contact with the heat recovery system  200  at a position coinciding with the heat exchanger  202 , for example. In this way, heat transfer occurs at the heat exchanger. 
         [0039]    It will be appreciated that one or more of the heat exchangers may be gas-to-liquid and/or gas-to-thermosyphon heat exchangers. As shown, heat exchangers  202  may be thermally coupled to an engine system in parallel. In some embodiments, heat exchangers  202  may be thermally coupled to each of the engine systems in series. For example, heat transfer fluid may flow through a series of heat exchangers  202  fluidically coupled to a common heat transfer fluid passage. 
         [0040]    As shown, heat transfer fluid (HTF) may flow through a heat exchanger and may thermally transfer heat to a fluid of one or more of the aforementioned systems. Arrows  208  generally indicate a direction of HTF flow, and arrows  210  generally indicate a direction of fluid flow for each engine system. Pump  212  may drive HTF fluid flow through heat recovery system  200 . As shown, pump  212  is positioned upstream from heat exchanger  156 ; however, another position is possible without departing from the scope of this disclosure. Further, it will be appreciated that coolant system  204 , cabin heating system  228  and/or the transmission system  206  may have another driving mechanism to drive fluid flow through each respective system. For example, each engine system  203  may have a pump, similar to pump  212 , fluidically coupled to the fluid flow. 
         [0041]    Heat recovery system  200  may further include one or more control valves  214 , one or more variable position valves  216 , one or more manifolds such as manifold  218  and manifold  220 , and expansion device  222 . 
         [0042]    Control valves  214  may be actuated by a controller (not shown) to regulate HTF flow through heat recovery system  200 . As shown, a control valve may be positioned upstream from one of the heat exchangers  202 , upstream from heat storage device  100 , and/or at another position within heat recovery system  200  to regulate HTF flow. Depending on an operational state of the vehicle, one or more of the control valves may be actuated to regulate a temperature of the HTF. For example, when one or more control valves are closed, a volume of circulating HTF can be reduced such that the HTF can increase in temperature more rapidly. 
         [0043]    Further, the HTF temperature may be regulated via actuation of variable control valve  216 . Such a control valve may be actuated to open at varying degrees to change a fluid flux of the HTF passing through variable control valve  216 . As shown, variable control valve  216  is positioned upstream from manifold  220 , and is included within bypass loop  224 . Bypass loop  224  may bypass heat storage device  100 . Therefore, bypass loop  224  may allow HTF to circulate without passing through heat storage device  100 . For example, to conserve heat stored in heat storage device  100 , variable control valve  216  may be adjusted to allow HTF fluid flow to flow through bypass loop  224 . In other words, bypass loop  224  may be a blending loop that blends cooler HTF fluid with warmer HTF fluid that circulates through heat exchanger  156 , heat storage device  100 , and/or one or more heat exchangers  202 . By blending HTF circulating through bypass loop  224  with other circulating HTF flow, an overall temperature of the circulating HTF may be reduced. 
         [0044]    Further still, the HTF temperature may be regulated by routing all circulating HTF flow through bypass loop  226 . For example, bypass loop  226  may be an exhaust temperature boosting loop and bypass loop  226  may be a thermal recharging loop, depending on the operational state of engine  12  and/or the thermal capacity of heat storage device  100 . For example, bypass loop  226  may function as the exhaust temperature boosting loop when heat storage device  100  holds a thermal charge and the exhaust temperature is below a threshold value. Further, heat exchanger  156  may be positioned upstream from one or more exhaust emissions control devices and heat storage device  100  may discharge heated HTF to be delivered to heat exchanger  156 . In this way, heated HTF may only be circulated through bypass loop  226  to increase a temperature of the exhaust flow, such that a time to reach catalyst light-off is reduced. 
         [0045]    Further, as the thermal recharging loop, bypass loop  226  may extract heat from the exhaust flow to recharge heat storage device  100 . Thus, HTF may only flow through thermal charging loop  225  to increase the temperature of HTF via heat exchanger  156 . In this way, HTF may be heated by the exhaust flow to recharge the thermal capacity of heat storage device  100 . It may be advantageous to recharge heat storage device  100  in this way when a temperature of the heat storage device is below a threshold value. For example, after heat storage device has discharge its thermal capacity, and/or after the various engine systems are sufficiently warm. 
         [0046]    In other words, one or more control valves  214  positioned upstream from heat exchangers  202  may be closed to reduce a volume of circulating HTF, and/or variable position control valve  216  may also be closed, such that circulating HTF only passes through bypass loop  226 , heat exchanger  156 , and heat storage device  100 . A method for regulating HTF flow through heat recovery system  200  by actuating one or more control valves is described with respect to  FIG. 3 . 
         [0047]    As shown, manifolds  218  and  220  may be positioned in heat recovery system  200  where more than one pipe carrying HTF fluid merges. For example, manifold  218  may be configured to receive HTF fluid from one pipe and may include two HTF outlets. As another example, manifold  220  may be configured to receive HTF fluid from more than one pipe and may include more than one outlet. As shown, manifold  220  receives HTF flow from heat storage device  100  and from bypass loop  224 . Further, manifold  220  may have an outlet directed towards each heat exchanger  202  and/or to thermal charging loop  225 . It will be appreciated that manifolds  218  and  220  are provided as non-limiting examples, and thus, other configurations are possible without departing from the scope of this disclosure. 
         [0048]    Expansion device  222  may be positioned downstream from the plurality of heat exchangers  202 . As shown, expansion device  222  is configured to receive HTF from each of the heat exchangers  202 , as well as thermal recharging loop  225 . For example, expansion device  222  may be provided for degassing. In other words, expansion device  222  may be positioned downstream from heat exchangers  202  and thermal recharging loop  225  to regulate a pressure of the incoming HTF flow. 
         [0049]    It will be appreciated that heat recovery system  200  is provided by way of example, and thus, is not meant to be limiting. Therefore, it is to be understood that heat recovery system  200  may include additional and/or alternative features than those illustrated in  FIG. 2  without departing from the scope of this disclosure. For example, the heat recovery system may include a three-way valve to regulate HTF flow to more than one engine system. 
         [0050]      FIG. 3  schematically shows an example method  300  that may be used to operate heat recovery system  200 . 
         [0051]    At  302 , method  300  includes determining if an engine has started. If the answer to  302  is NO, method  300  ends. If the answer to  302  is YES, method  300  continues to  304 . 
         [0052]    At  304 , method  300  includes determining if an HTF temperature is below a threshold value. For example, the exhaust temperature may be an exhaust gas temperature upstream and/or downstream from an emissions control device. If the answer to  304  is YES, method  300  continues to  306 . If the answer to  304  is NO, method  300  continues to  308 . 
         [0053]    At  306 , method  300  includes reducing a volume of circulating heat transfer fluid (HTF) and discharging a heat storage device (e.g., heat storage device  100 ) to heat an exhaust system component, such as an exhaust system component. For example, reducing the volume may include closing one or more control valves to inhibit the circulating heat transfer fluid from being distributed to one or more engine systems. Further, discharging the heat storage device may include discharging stored thermal energy of the heat storage device, wherein the stored thermal energy is stored from a previous engine operation. Further still, the stored thermal energy may be transferred to the circulating heat transfer fluid and distributed to the exhaust system component. In some embodiments, the exhaust system component may be upstream from an emissions control device. 
         [0054]    At  308 , method  300  includes distributing circulating HTF to one or more engine systems. For example, one or more control valves may be actuated to distribute circulating HTF to one or more of a cabin heating system, an engine coolant system, a transmission system, etc. 
         [0055]    At  310 , method  300  includes determining if the one or more engine systems are sufficiently warm. If the answer to  310  is NO, method  300  returns to  306 . If the answer to  310  is YES, method  300  continues to  312 . 
         [0056]    At  312 , method  300  includes recharging the heat storage device. For example, the volume of circulating HTF may be reduced and/or a bypass loop may be opened such that HTF is circulated through a heat exchanger thermally coupled to the exhaust system and through the heat storage device. In this way, a thermal capacity of the heat storage device may be increased. 
         [0057]    At  314 , method  300  includes determining if a HTF temperature is above a threshold value. For example, the HTF may become too warm when the vehicle is in operation for an extended period of time. If the answer to  314  is NO, method  300  continues to  316 . If the answer to  314  is YES, method  300  continues to  318 . 
         [0058]    At  316 , method  300  includes closing a blending loop. As such, the volume of circulating HTF is not adjusted in response to the temperature of the HTF. 
         [0059]    At  318 , method  300  includes adjusting a variable position valve of the blending loop. As such, a dead volume of HTF is released from the blending loop to reduce the temperature of the circulating HTF. As described above, the temperature of the HTF may be regulated based on a position of the variable position valve. For example, the valve may be fully opened to rapidly cool the HTF. As another example, the valve may be partially opened to moderately cool the HTF. 
         [0060]    It will be appreciated that method  300  is provided by way of example, and thus, is not meant to be limiting. Therefore, it is to be understood that method  300  may include additional and/or alternative steps than those illustrated in  FIG. 3  without departing from the scope of this disclosure. Further, it will be appreciated that method  300  is not limited to the order illustrated; rather, one or more steps may be rearranged or omitted without departing from the scope of this disclosure. For example, one or more portions of method  300  may occur without starting the engine. As described above, the heat storage device may be activated to discharge without operating the engine. 
         [0061]    Various conduits may be referred to as pipes, which can encompass various forms of conduits, passages, connections, etc., and are not limited to any specific cross-sectional geometry, material, length, etc. 
         [0062]    It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
         [0063]    The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.