Heat exchanger for a rankine cycle in a vehicle

[0025] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are only examples of the present invention, and the present invention may be embodied in various and alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or reduced to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but only as a representative basis for teaching those skilled in the art to use the present invention in various forms. The components described in chemical terms refer to the components when added to any composition specified in the specification, and do not necessarily exclude chemical interactions between the components of the mixture once the mixture is mixed. The fluid as described in the present disclosure may refer to substances in various states or phases (including vapor phase, liquid phase, vapor/liquid mixed phase, superheated gas, supercooled liquid, etc.).

[0026] The Rankine cycle can be used to convert thermal energy into mechanical or electrical energy. More than one system (such as engine coolant, engine or transmission oil, exhaust gas recirculation (EGR) gas, exhaust gas, etc.) has been focused on collecting heat energy more efficiently or exhausting waste heat from vehicles. The present disclosure provides a Rankine cycle with a heat exchanger or evaporator that provides phase separation as the working fluid evaporates, thereby improving cycle efficiency and maintaining a substantially uniform temperature distribution of the liquid and vapor phases of the working fluid in the evaporator.

[0027] figure 1 A simplified schematic diagram of the various systems in the vehicle 10 according to an example is shown. The fluid in each vehicle system can be cooled by heat transfer with the working fluid in the heat exchanger of the Rankine cycle, and the working fluid is then cooled by using outside air in the condenser of the Rankine cycle. The Rankine cycle allows energy recovery by converting waste heat in the vehicle 10 that would otherwise be transferred to the outside air as waste heat into electrical or mechanical energy.

[0028] The vehicle may be a hybrid vehicle having multiple torque sources available for wheels. In other examples, the vehicle is a conventional vehicle with only an engine, or an electric vehicle with only an electric motor. In the example shown, the vehicle has an internal combustion engine 50 and an electric machine 52. The motor 52 may be a motor or a motor/generator. The engine 50 and the electric motor 52 are connected to one or more wheels 55 via a transmission 54. The transmission 54 may be a gearbox, planetary gear system, or other transmission. The clutch 56 may be provided between the engine 50, the electric motor 52 and the transmission 54. The power transmission system can be configured in various ways, including parallel, series, or series-parallel hybrid vehicles.

[0029] The electric motor 52 receives electrical energy from the traction battery 58 to provide torque to the wheels 55. For example, during a braking operation, the motor 52 may also operate as a generator to provide electrical energy to charge the battery 58.

[0030] The engine 50 may be an internal combustion engine (such as a compression ignition engine or a spark ignition engine). The engine 50 has an exhaust system 60 through which exhaust gas is discharged from cylinders in the engine 50 to the atmosphere. The exhaust system 60 may include a muffler for noise control. The exhaust system 60 may also include an emission system (such as a catalytic converter, a particulate filter, etc.).

[0031] The engine 50 also has a cooling system 62. The cooling system contains engine coolant fluid that removes heat from the engine 50 during operation, which may include water, glycol, and/or other fluids. The engine 50 may be provided with internal or external cooling jackets having passages to remove heat from various areas of the engine 50 using recirculated engine coolant fluid. The cooling system 62 may include a pump and a reservoir (not shown).

[0032] The vehicle has a thermal cycle 70. In one example, loop 70 is a Rankine loop. In another example, cycle 70 is a modified Rankine cycle or another thermodynamic cycle that includes working fluids that pass through more than one phase transition during cycle operation. The Rankine cycle 70 contains a working fluid. In one example, the working fluid undergoes a phase change and is a mixed-phase fluid that exists in both vapor and liquid phases in the system. The working fluid may be R-134a, R-245 or other organic or inorganic chemical refrigerants based on the desired operating parameters of the cycle.

[0033] The cycle 70 has a pump 72, compressor, or other device configured to increase the pressure of the working fluid. The pump 72 may be a centrifugal pump, a positive displacement pump, or the like. The working fluid flows from the pump 72 to one or more heat exchangers. The heat exchanger may be a preheater, evaporator, superheater, etc. configured to transfer heat to the working fluid.

[0034] The example shown has a first heat exchanger 74 which is configured as a preheater. The second heat exchanger 76 is provided, and the heat exchanger may be configured as an evaporator. In other examples, more or fewer heat exchangers may be provided downstream of the pump 72. For example, the cycle 70 may be provided with only the heat exchanger 76, or may be provided with three or more heat exchangers to heat the working fluid. In addition, the heat exchangers downstream of the pump 72 may be arranged or positioned in various ways relative to each other, for example, in parallel, series as shown in the figure, or a combination of series and parallel flow.

[0035] The heat exchangers 74, 76 are configured to transfer heat from an external heat source to heat the working fluid in the cycle 70 and cause a phase change from the liquid phase to the vapor phase. In the example shown, the heat exchanger 74 is configured to transfer heat from the engine coolant fluid in the cooling circuit 62 to the working fluid in the cycle 70. Therefore, the temperature of the engine coolant is lowered before the engine coolant is returned to the engine 50 to remove heat therefrom, and the heat exchanger 74 acts as a radiator in the cooling system 62. Likewise, the temperature of the working fluid of the cycle 70 increases in the heat exchanger 74.

[0036] In other examples, as discussed in more detail below, the heat exchanger 74 is configured to transfer heat from another fluid in the vehicle system (including but not limited to engine lubricating fluid, transmission lubricating fluid, and battery cooling fluid) to the circuit 70 Working fluid. In a further example, multiple preheat heat exchangers 74 are provided and each preheat heat exchanger 74 is in fluid communication with an independent vehicle system to receive heat therefrom. Valves or other flow control mechanisms can be provided to selectively direct or control flow to multiple heat exchangers.

[0037] In another example, the heat exchanger 74 is located downstream of the heat exchanger 76, so that the heat exchanger 74 is configured as a superheater and receives fluid from various vehicle systems, including but not limited to exhaust gas recirculation (EGR) flow. ) Heat transfer. The heat exchanger 74 provides a radiator for the EGR flow, thereby providing waste heat to the working fluid in the cycle 70. The positioning of the heat exchanger 74 relative to the heat exchanger 76 may be based on the average temperature or available heat of the waste heat fluid of the vehicle system.

[0038] A second heat exchanger 76 is also provided in the cycle 70. In one example, the heat exchanger 76 is configured to transfer heat from the exhaust gas in the engine exhaust system 60 to the circulating working fluid. The engine exhaust system 60 may have a first flow path 78 through or in contact with the heat exchanger 76. The engine exhaust system 60 may also have a second flow path or bypass flow path 80 to divert exhaust gas flowing around the heat exchanger 76. The valve 82 can be configured to control the amount of exhaust gas flowing through the heat exchanger 76, thereby providing information on the amount of heat transferred to the working fluid and the temperature and state of the working fluid at the outlet of the heat exchanger 76 or upstream of the expander 84. control.

[0039] As discussed further below, at least one of the heat exchangers 74, 76 is configured to transfer sufficient heat to the working fluid in the cycle 70 to evaporate the working fluid. The evaporator receives the working fluid in the liquid phase or the liquid-vapor mixed phase solution, and heats the working fluid to the vapor phase or the superheated vapor phase. The present disclosure generally describes the use of a heat exchanger 76 using engine exhaust gas 60 as an evaporator; however, reference is made below image 3 with Figure 4 The evaporator is described in more detail. The heat exchanger 74 in the cycle 70 can be configured as an evaporator.

[0040] The expander 84 may be a steam turbine (such as a centrifugal steam turbine or an axial steam turbine) or other similar devices. As the working fluid expands, work is generated by rotating or actuating the expander 84 by the working fluid. The expander 84 may be connected to the motor/generator 86 to rotate the motor/generator to generate electrical energy, or to other mechanical linkages to provide additional mechanical energy to the drive shaft and wheels 55. The expander 84 may be connected to the generator 86 by a shaft or other mechanical linkage. The generator 86 is connected to the battery 58 to provide electrical energy to charge the battery 58. An inverter or AC-DC converter 88 may be provided between the generator 86 and the battery 58.

[0041] The working fluid leaves the expander 84 and flows to the heat exchanger 90 (also referred to as the condenser 90) in the cycle 70. The condenser 90 may be located in the front area of ​​the vehicle 10. The condenser 90 is configured to be in contact with the outside airflow 92 so that heat is transferred from the working fluid to the outside airflow 92 to remove heat from the working fluid and cool and/or condense the working fluid. The condenser 90 may be single-stage or multi-stage, and valves or other mechanisms may be used to control the flow of working fluid through the stages according to the needs of the circulation 70.

[0042] In some examples, the circulation 70 includes a fluid reservoir 94 or dryer. The reservoir 94 may be configured as a fluid or liquid reservoir for the working fluid in the circulation 70. The pump 72 draws fluid from the reservoir 94 to complete the cycle 70. As from figure 2 It can be seen that the cycle 70 is a closed loop cycle so that the working fluid does not mix with other fluids in the vehicle or the outside air.

[0043] As described below, the loop 70 may include a controller 96 configured to operate the loop within predetermined parameters. The controller 96 may communicate with various valves and/or sensors in the pump 72, the expander 84 and the cycle 70 and the vehicle 10.

[0044] The controller 96 can be combined with an engine control unit (ECU), a transmission control unit (TCU), a vehicle system controller (VSC), etc., or with an engine control unit (ECU), a transmission control unit (TCU), a vehicle system controller (VSC), etc. ) And other communications, and can also communicate with various vehicle sensors. The control system for the vehicle 10 may include several controllers, may be integrated into a single controller, or have multiple modules. Some controllers or all controllers can be connected via a controller area network (CAN) or other system. The controller 96 and the vehicle control system may include a microprocessor or central processing unit (CPU) in communication with various types of computer-readable storage devices or media. For example, a computer-readable storage device or medium may include volatile storage and non-volatile storage in read only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a permanent or non-volatile memory that can be used to store various operating variables when the CPU is powered down. The computer readable storage device or medium can use any number of known storage devices (such as PROM (Programmable Read Only Memory), EPROM (Electrically Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), Flash memory or any other electrical, magnetic, optical, or combined storage device capable of storing data, some of which represent executable instructions used by the controller to control the vehicle or loop 70.

[0045] In one or more embodiments, the vehicle may also be provided with an air conditioning system 100. The air conditioning system 100 may form part of a heating, ventilation and air conditioning (HVAC) system for the vehicle 10. The HVAC system provides temperature-controlled air to the vehicle or passenger compartment for cabin climate control of the vehicle occupants. The air conditioning system 100 has a first heat exchanger 101 or a condenser that is in contact with outside air 92. The condenser 101 may be located in the front area of ​​the vehicle 10. The condenser 101 is configured for heat transfer between the outside air and the refrigerant or other fluid in the system 100.

[0046] The air conditioning system 100 may also include an expansion device, a valve or throttle 102, and a compressor or pumping device 104. The system 100 has another heat exchanger 106 that is in contact with the air flow 110 to be directed to the cabin 108 and the refrigerant in the system 100. The airflow 110 used for cabin conditioning flows through the heat exchanger 106 and is cooled by the refrigerant in the heat exchanger 106, and then flows to the cabin 108 according to the needs of the vehicle occupants.

[0047] figure 2 Shows for example figure 1 The pressure-enthalpy diagram of the working fluid of the Rankine cycle or thermal cycle 70 shown in. The vertical axis of the graph is pressure (P) and the horizontal axis is enthalpy (h). The unit of enthalpy may be energy per unit mass, for example kJ/kg.

[0048] A dome 120 provides a dividing line between the phases of the working fluid. In the area 122 to the left of the dome 120, the working fluid is liquid or supercooled liquid. In the area 126 to the right of the dome 120, the working fluid is steam or superheated steam. In the area 124 below the dome 120, the working fluid is a mixed phase (e.g., a mixture of liquid and vapor phases). Along the left hand side of the dome 120, where areas 122 and 124 meet, the working fluid is a saturated liquid. Along the right hand side of the dome 120, where areas 124 and 126 meet, the working fluid is saturated steam.

[0049] According to the embodiment, the figure shows figure 1 The Rankine cycle 70. The drawn loop 70 is simplified for the purpose of the present disclosure, and although there may be losses in practical applications, the loop 70 or any losses in the system are not shown. Losses can include pumping losses, pipe losses, pressure and friction losses, heat loss through various components, and other irreversible factors in the system. Such as figure 2 The operation of the cycle 70 shown in is simplified to assume constant pressure, adiabatic, reversible, and/or appropriate isentropic process steps described below; however, those of ordinary skill in the art should recognize that the cycle 70 is practically applied These assumptions can be different. The cycle is drawn as at high pressure P H And low pressure P L Run between. The figure also shows isotherms (e.g. T H And T L ).

[0050] Cycle 70 begins at point 130 where working fluid enters pump 72. At 130, the working fluid is liquid and can be subcooled to below P L The saturation temperature is 2-3 degrees Celsius or more. At point 132, the working fluid is at a higher pressure P L It leaves the pump 72 in the liquid phase. In the example shown, the pumping process from 130 to 132 is modeled as isentropic or adiabatic reversible.

[0051] At 132, the working fluid enters one or more heat exchangers (e.g., heat exchangers 74, 76). Waste heat from fluids in one or more vehicle systems is used in heat exchangers 74, 76 to heat the working fluid. In the example shown, engine coolant and exhaust gas are used to heat the working fluid. At point 134, the working fluid leaves the heat exchanger. The heating process from 132 to 134 is modeled as a constant pressure process. As can be seen from the figure, the process from 132 to 134 occurs at P H And the temperature increases to T at 134 H. The working fluid starts at 132 in the liquid phase and leaves the heat exchangers 74, 76 at 134 in the superheated vapor phase. In the example shown, the working fluid enters the heat exchanger 76 as a mixed liquid-vapor phase fluid and leaves the heat exchanger 76 in the vapor phase.

[0052] At point 134, the working fluid enters the expander 84 (such as a steam turbine) as superheated steam. As it expands, the working fluid drives or rotates the expander to produce work. At point 136, the working fluid is at pressure P L Leave the expander 84. As shown, at 136, the working fluid may be superheated steam. In other examples, the working fluid may be saturated steam after exiting the expander 84 or may be a mixed phase and be in the zone 124. In a further example, the working fluid is within a few degrees Celsius of the saturated steam line on the right hand side of the dome 120. In the example shown, the expansion process from 134 to 136 is modeled as isentropic or adiabatic reversible. As the working fluid expands, the expander 84 causes a drop in pressure across the device and a corresponding drop in temperature.

[0053] At 136, the working fluid enters one or more heat exchangers (e.g., heat exchanger 90). The outside air received through the front area of ​​the vehicle is used in the heat exchanger 90 to cool the working fluid. At point 130, the working fluid leaves the heat exchanger 90 and then flows to the pump 72. A reservoir may also be included in cycle 70. The cooling process from 136 to 130 is modeled as a constant pressure process. As can be seen from the figure, the process from 136 to 130 occurs at P L Place. The temperature of the working fluid in the heat exchanger 90 can be reduced. The working fluid starts at 136 as a superheated steam or vapor-liquid mixed phase and leaves the heat exchanger 90 at 130 as a liquid.

[0054] In one example, loop 70 is configured to start with P H /P L Operation at a pressure ratio of about 3, or in a further example, a pressure ratio of about 2.7. In other examples, the pressure ratio may be higher or lower. According to the requirements of the vehicle 10 and its surrounding environment, the cycle 70 can be adapted to operate in various external environments. In one example, the cycle 70 is configured to operate within the range of possible outside temperatures. The outside temperature may provide a limit to the amount of cooling of the working fluid that can be used in the heat exchanger 90. In one example, the cycle 70 may operate between outside or ambient temperature of -25 degrees Celsius and 40 degrees Celsius. In other examples, the cycle 70 may operate at a higher and/or lower ambient temperature.

[0055] The power provided by the cycle 70 may be a function of the mass flow rate of the waste heat fluid, the temperature of the waste heat fluid, the temperature of the working fluid at point 134, and the mass flow rate of outside air. For example, in the case where the exhaust gas provides the only waste heat source, the power provided by the circulation 70 is the mass flow rate of the exhaust gas passing through the heat exchanger 76, the temperature of the exhaust gas entering the heat exchanger 76, and the temperature of the working fluid at point 134 And as a function of the mass flow rate of outside air. For systems with more than one waste heat source, the power provided by cycle 70 will also include the mass flow rate and temperature of each source. In one example, the power output of the cycle 70 is about 0.5-1.5kW, and in a further example, for a cycle where the exhaust gas temperature is in the range of 500-800 degrees Celsius and the exhaust gas mass flow rate is in the range of 50-125kg/hr, The output power is about 1kW.

[0056] The efficiency of the cycle 70 relative to the vehicle 10 may be determined based on the electricity generated by the generator 86 and the rate of available heat transfer from waste heat sources (eg, engine exhaust, engine coolant, etc.). The rate of heat transfer available is a function of the mass flow rate of the waste heat fluid through the associated circulating heat exchanger and the temperature difference of the waste heat fluid across the heat exchanger. In one example, the cycle efficiency using only exhaust heat is measured to be above 5% on average, and in a further example, for a cycle using only waste heat of exhaust gas, the cycle efficiency is measured to be above 8% on average.

[0057] Maintaining the state of the working fluid at a particular operating point in the cycle 70 or relative to system operation and maintaining system efficiency may be critical. For example, one or both of the heat exchangers 74, 76 may need to be designed to use liquid phase, mixed phase fluid, and vapor phase fluid. The working fluid may need to be in the liquid phase at the midpoint 130 of the cycle to prevent air lock in the pump 72. In addition, based on the structure of the expander 84, it may be necessary to maintain the working fluid as steam between points 134 and 136 because the mixed phase may reduce system efficiency or wear device 84. Based on the outside air temperature and the vehicle speed controlling the outside airflow rate, the cooling amount and/or cooling rate of the working fluid available in the heat exchanger 90 may also be limited. In addition, the amount and/or rate of heating available for the working fluid may be limited when the engine exhaust gas and/or engine coolant have not reached their operating temperature when the vehicle is started.

[0058] For example, based on the minimum outside air operating temperature T L,min And the maximum outside air operating temperature T H,max , Cycle 70 can operate under multiple operating conditions. The working fluid is selected based on the cycle and the operating conditions at various points in the cycle and the constraints imposed by these operating conditions. In addition, the flow rate of the exhaust gas or other waste heat source through the heat exchangers 74, 76 can be modified to control the circulation 70 to operate within a desired temperature and pressure range, thereby controlling the amount of heat transferred to the working fluid and the point of the working fluid. The temperature at 134. The heat exchanger 90 can also be controlled by providing additional stages or restricted stages for the working fluid to flow through based on outside air temperature, flow rate, and humidity, thereby controlling the working fluid temperature and cooling amount at point 130. In addition, the flow rate of the working fluid can be controlled by the pump 72, so that the working fluid has a longer or shorter residence time in each heat exchanger 74, 76, 90, thereby controlling the heat transfer to or from the working fluid. The amount.

[0059] image 3 A Rankine cycle 70 or similar heat exchanger 150 of a mixed phase thermodynamic cycle for waste heat recovery in a vehicle is shown. The heat exchanger 150 is configured as an evaporator for the circulation 70. The heat exchanger 150 may be used as the heat exchanger 76 in the cycle 70 and is configured to transfer heat between the exhaust gas and the working fluid in the cycle 70 to heat the working fluid. In other examples, the heat exchanger 150 may be used to transfer heat between another waste heat fluid flow (eg, EGR flow) and the working fluid.

[0060] The heat exchanger 150 has a housing 152 that encloses a series of heat exchange tubes 154 or cavities. The heat exchanger 150 may have one heat exchange tube 154 or may have two, three, five, ten, or any number of heat exchange tubes 154 or cavities. The inlet manifold 156 provides the working fluid flow in the thermodynamic cycle 70 to the heat exchanger 150. The inlet manifold 156 is connected to the inlet header 158. The inlet header 158 has a series of tubes, each tube is connected to an associated heat exchange tube 154 and provides a liquid phase working fluid to the associated heat exchange tube 154. The outlet manifold 160 has an outlet header 162 with a tube connected to the associated heat exchange tube 154. The outlet manifold 160 and the outlet header 162 receive the vapor phase working fluid from the heat exchange tubes 154 so that the working fluid continues to flow through the thermodynamic cycle.

[0061] The heat exchanger 150 has a longitudinal axis 170, a transverse axis 172 and a vertical axis 174. The heat exchange tube 154 is shown as having a longitudinal axis substantially parallel to the longitudinal axis 170, for example, the heat exchange tube 154 extends substantially parallel to the longitudinal axis 170. The vertical axis 174 may be substantially aligned with gravity on the heat exchanger 150. The longitudinal axis 170 and the lateral axis 172 may be substantially perpendicular to the vertical axis 174 such that both of them are in the horizontal plane of the heat exchanger 150. As described above, since the heat exchanger 150 can be used in the vehicle 10 with the circulation 70, as the vehicle 10 moves through different gradients, the axes 170, 172, 174 may deviate from true vertical and horizontal. However, as the vehicle travels through different gradients, the vertical axis 174 maintains at least the vertical gravity component.

[0062] The inlet manifold 156 is positioned downstream of a pump or the like in a thermodynamic cycle (such as cycle 70). The inlet manifold 156 receives the working fluid in a liquid phase or a mixed phase of liquid and vapor. In other examples, the working fluid may be in the vapor phase, for example, when another heat exchanger is located between the pump and the heat exchanger 150 in the cycle. The working fluid containing the liquid phase flows through the inlet manifold 156. Although only one inlet manifold 156 is shown, the heat exchanger 150 may also have additional manifolds, valves to control fluid flow, etc. in other examples. The inlet manifold 156 may extend in the lateral direction and may be substantially parallel to the lateral axis 172. In other examples, the manifold 156 may be positioned in the heat exchanger 150 in other ways. The inlet manifold 156 can allow working fluid to flow through the inlet manifold substantially horizontally.

[0063] The inlet manifold 156 has an inlet header 158 that includes one or more inlet header tubes or inlet risers 180 to direct the working fluid to each heat exchange tube 154. The inlet header 158 may include one or more inlet risers 180 for each heat exchange tube 154. The inlet riser 180 fluidly connects the inlet manifold 156 to the heat exchange tube 154. Each inlet riser 180 may include a section 182 that provides a vertical flow component for the working fluid. Such as image 3 As shown in, the riser 180 has a first section connected to the manifold 156 and a substantially vertical section 182 connected to the heat exchange tube 154. The first section and the section 182 may be perpendicular to each other or arranged at another angle with respect to each other. In other examples, the riser 180 may have other shapes or may only have straight pipe sections (such as section 182) connecting the manifold 156 to the heat exchange tubes 154. Since the heat exchange tubes 154 are arranged in an array, the individual risers 180 of the header 158 may be different from each other to connect the manifold 156 to the heat exchange tubes 154.

[0064] The heat exchange tube 154 is disposed in the heat exchanger 150 and provides a main mechanism for heat transfer between the waste heat fluid and the working fluid in the heat exchanger 150. As shown in the figure, the heat exchange tube 154 may extend substantially horizontally within the heat exchanger 150 and may be substantially parallel to the longitudinal axis 170. In other examples, the heat exchange tubes 154 may be positioned in the heat exchanger 150 in other forms. As shown, the heat exchange tubes 154 may be arranged in an array, where they are spaced apart from each other to allow waste heat fluid to flow between them. The spacing and positioning of the heat exchange tubes 154 can also provide control of the flow path of the waste heat fluid through the heat exchanger 150. For example, by offsetting the heat exchange tubes 154 in adjacent rows, turbulence can be generated in the waste heat fluid, thereby increasing heat transfer.

[0065] The heat exchange tube 154 is generally shown as a straight tube. In other examples, the heat exchange tube may be curved or other shapes. The heat exchange tube 154 has a first end area 184 and a second end area 186. The middle region 188 is located between the two end regions 184,186. In one example, as shown, the inlet header 158 is connected to the first end region 184.

[0066] As shown by the arrow 190, the heat exchange tube 154 may have a shell structure. The shell structure of the heat exchange tube 154 allows the waste heat fluid to flow through the inner and outer walls of the heat exchange tube 154, thereby increasing the surface area of ​​the heat exchange tube 154 and increasing the heat transferred from the waste heat fluid to the working fluid. In another example, the heat exchange tube 154 is configured as a standard tube without a shell structure. In a further example, the heat exchange tube 154 may have a multi-layer shell structure that provides additional surface area for heat transfer.

[0067] The outlet manifold 160 has an outlet header 162 that includes one or more outlet collection tubes 200 that receive working fluid from each heat exchange tube 154. Each collection tube 200 of the outlet header 162 may include one or more outlet risers 202. The outlet riser 202 and the collection pipe 200 fluidly connect the heat exchange pipe 154 to the main outlet pipe of the outlet manifold 160.

[0068] Each outlet riser 202 may contain a section that provides a vertical flow component for the working fluid. Such as image 3 As shown in, the riser 202 has a substantially vertical section connected to the heat exchange tube 154. The riser 202 provides outlets for the working fluid in the vapor phase from multiple locations of the heat exchange tube 154. In the example shown, a plurality of risers 202 are provided for each heat exchange tube 154, wherein one riser 202 is connected to the heat exchange tube 154 in the first end region 184, and the other riser 202 is in the second The end region 186 is connected to the heat exchange tube 154 and the other riser 202 is connected to the heat exchange tube 154 throughout the middle region 188. The riser 202 may be connected to the heat exchange tube 154 and be spaced apart along the longitudinal axis 204 of the heat exchange tube 154. The risers 202 may be equally spaced apart from each other, or there may be a variable spacing between the risers 202. The riser 202 may have the same cross-sectional area, or may have a varying cross-sectional area to provide additional control over the flow of working fluid. Since the heat exchange tubes 154 are arranged in an array, the respective tubes of the header 162 including the riser pipe 202 may be different from each other to connect the manifold 160 to the heat exchange tubes 154.

[0069] The collection tubes 200 are all located above each heat exchange tube 154 and may be substantially parallel to the longitudinal axis 204. The collection tube 200 can substantially extend the length of the heat exchange tube 154 and fluidly connect the riser 202 with the tube of the outlet manifold 160. In one example, the collection pipe 200 and the stand pipe 202 are arranged substantially perpendicular to each other.

[0070] The main pipe of the outlet manifold 160 is positioned upstream of the expander or the like in the thermodynamic cycle. The outlet manifold 160 provides a working fluid in a vapor phase or a superheated vapor phase. Although only one outlet manifold 160 is shown, the heat exchanger 150 may also have additional manifolds, valves to control fluid flow, etc. in other examples. The outlet manifold 160 may extend in the lateral direction and may be substantially parallel to the lateral axis 172. In other examples, the manifold 160 may be positioned in the heat exchanger 150 in other ways. The outlet manifold 160 may allow working fluid to flow through the outlet manifold 160 substantially horizontally. The outlet manifold 160 may be opposed to the inlet manifold 156 so that the heat exchange tubes 154 are positioned between them. In other examples, the inlet manifold 156 and the outlet manifold 160 may be located on the same side of the heat exchanger 150 and adjacent to each other.

[0071] The heat exchange tube 154 may be supported by the housing 152 (for example, supported at the end of the housing). The housing is provided with an inlet 206 and an outlet 207 for waste heat fluid. In the example shown, the inlet 206 is provided on one end plate of the housing 152, and the outlet 207 is provided on the other end plate of the housing 152. The inlet 206 and the outlet 207 may be connected to an exhaust system for an engine or another vehicle system that provides waste heat for a Rankine cycle or a thermal cycle. The heat exchanger 150 shown in the figure is configured as a counter-flow heat exchanger in which a working fluid and a waste heat fluid travel in opposite directions. In other examples, the heat exchanger 150 may be configured as a parallel flow heat exchanger, a cross flow heat exchanger, or the like. The heat exchanger 150 may be an once-through heat exchanger in which the working fluid passes through the heat exchanger only once and is not circulated or recirculated therein.

[0072] The housing 152 may be provided with a baffle 208. The baffle 208 can provide structural support for the heat exchange tube 154, the collection tube 200, and the outer wall of the housing. The baffle 208 may additionally support the riser 202 or form a part of the riser 202. The baffle 208 may include a plurality of openings 209 to allow the passage of waste heat fluid. The spacing and positioning of the baffles 208 can be used to control the flow of waste heat fluid through the heat exchanger 150. In addition, the position and size of the opening 209 in the baffle 208 may be formed to control the flow of waste heat fluid through the heat exchanger 150.

[0073] Each tube of the heat exchanger 150 is shown as having a circular cross-section; however, other shapes of tubes for the heat exchanger 150 can also be considered, and the individual tubes may have the same shape and size, or may have different shapes from each other. Shape or size.

[0074] The heat exchanger 150 may be made of various materials and manufactured accordingly. In the example shown, the heat exchanger 150 is made of metal (such as aluminum) and is welded or otherwise connected together. In other examples, the heat exchanger 150 may be made of other materials based on the material's thermal conductivity, melting temperature, and other material properties (such as corrosion resistance or chemical resistance, etc.). For example, if the waste heat fluid is engine exhaust gas, the heat exchanger 150 is configured to operate in a high temperature (for example, a gas of about 800 degrees Celsius). It may also be necessary to design the heat exchanger 150 with pressure drop as a consideration for both the working fluid and the waste heat fluid. For example, when engine exhaust gas is used as a waste heat fluid, the heat exchanger 150 may be configured to provide a low pressure drop for exhaust gas passing through the heat exchanger 150 to limit the back pressure on the engine.

[0075] Figure 4 A schematic partial cross-sectional view of the heat exchanger 150 is shown to describe the operation of the heat exchanger 150 (for example, as the heat exchanger 76 in the cycle 70). The heat exchanger 150 may be provided as an evaporator for the working fluid in the circulation 70.

[0076] The working fluid enters the heat exchanger 150 at the inlet manifold 156. The working fluid in the inlet manifold 156 may be a supercooled liquid, a saturated liquid, or a liquid-vapor mixed phase fluid. In one example, the working fluid in the inlet manifold 156 is located at figure 2 At point 132 on the graph in. In another example, the working fluid may be in another state in area 122, area 124, or along the left hand side of dome 120. In a further example, the heat exchanger 150 can be used as a superheater in which the working fluid in the inlet manifold 156 is in the vapor phase. For the purpose of this disclosure, the working fluid in the inlet manifold 156 is a supercooled liquid (such as figure 2 The evaporator shown at midpoint 132) describes the operation of the heat exchanger 150. The working fluid is heated in the heat exchanger so that the working fluid at the tube of the outlet manifold 160 is vapor phase or superheated steam (such as figure 2 Shown at midpoint 134). Therefore, the heat exchanger 150 is described as providing the 132 to 134 process portion of the cycle 70. In other examples with additional heat exchangers in the cycle, heat exchanger 150 only provides a portion of the heating between points 132 and 134.

[0077] The liquid phase working fluid flows from the inlet manifold 156 to the inlet header 158. The inlet header 180 has a vertical section 182. Figure 4 The middle vertical section 182 is shown connected to the lower surface 210 of the heat exchange tube 154 and connected to the outer wall 212 of the heat exchange tube 154. Such as Figure 4 It can be seen that the inlet header 158 is connected to the end region 184 of the heat exchange tube 154. The heat exchange tube 154 has a shell structure.

[0078] The inlet header 158 is connected to the lower surface 210 to provide an underfill function for the heat exchange tube 154. The inlet header 158 may act as a sump at the low point of the heat exchange tube 154 to supply liquid working fluid for evaporation. Based on the force acting on the liquid due to gravity and the density of the liquid is higher than the density of the vapor phase, the inlet header 158 is positioned on the lower surface 210. At least part of the gravity is along the vertical axis 174. The liquid phase working fluid may fill a part of the heat exchange tube 154 indicated by the liquid level 218.

[0079] The heat exchange tube has an outer wall 212. The heat exchange tube 154 may also have a shell structure with an inner wall 214 as previously described. The inner wall 214 and the outer wall 212 contain a working fluid in the channel defined by the wall. The waste heat fluid 216 (eg, exhaust gas from an internal combustion engine) flows through the inner wall 214 and the outer wall 212. The inner wall 214 and the outer wall 212 may be circumferentially arranged concentrically around the longitudinal axis 204 of the heat exchange tube 154.

[0080] The heat exchanger 150 is shown as a counter-flow heat exchanger. The waste heat fluid 216 is at a higher temperature than the working fluid. The waste heat fluid 216 transfers heat or energy to the working fluid in the heat exchange tube 154. Heat transfer occurs based on both the convective heat transfer process and the conduction heat transfer process. Radiative heat transfer can also occur. Heat is transferred from the waste heat fluid 216 through the heat exchange tube 154 to the working fluid.

[0081] As the working fluid is heated in the heat exchange tube 154, the energy or enthalpy of the working fluid increases. Since this is a substantially constant pressure process, the heat transferred to the working fluid causes a phase change of the working fluid when the latent heat of vaporization for the working fluid is reached. The working fluid changes from a liquid to a saturated liquid-vapor mixture and at 220 into a vapor phase. The heat exchange tubes 154 may be positioned substantially horizontally or aligned with the axis 170 to provide improved efficiency of the evaporator 150 and circulation 70. In one example, when the waste heat fluid is supplied to the heat exchanger 150 at about 700 degrees Celsius, the efficiency of the heat exchanger 150 is about 90%,

[0082] As the working fluid evaporates, the heat exchange tube 154 and the riser 202 allow direct and instant phase separation of the working fluid and a more uniform temperature distribution within the heat exchanger 150. The liquid phase 218 remains in the heat exchange tube 154 and continues to receive heat from the waste heat fluid 216. Since the heat exchange tubes are arranged horizontally, the liquid phase has a large contact area with the inner and outer walls to improve heat transfer. In addition, the liquid phase of the working fluid and the heat exchange tube 154 have a larger free surface for evaporation. Due to the geometry of the heat exchanger 150 and the plurality of risers 202, the vapor phase has a direct path to the outlet manifold 160 after evaporation, thereby reducing or eliminating intricate flow paths, air resistance, or flow channels due to continuous heating Other areas where a part of the gas phase is trapped by the surrounding liquid, causing "hot spots". Generally, for working fluids, the thermal conductivity of the gas phase is much smaller than the thermal conductivity of the liquid phase. For example, R-134a in the liquid phase and R-134a in the gas phase have thermal conductivity of 0.092 Watts per meter Kelvin (W/mK) and 0.012 W/mK, respectively.

[0083] The vapor phase 220 of the working fluid rises in the heat exchange tube 154 and exits the heat exchange tube 154 through the riser 202. The riser 202 is spaced along the length of the heat exchange tube 154 to provide multiple outlets for the vapor phase. The riser 202 is also positioned for a substantially vertical flow of the vapor phase working fluid 220. The riser 202 is connected to the upper surface 222 of the heat exchange tube 154. The upper surface is substantially opposite to the lower surface 210. The riser 202 may be positioned adjacent to the respective end regions 184, 186 of the heat exchange tube 154, and other risers 202 may be provided in the middle region 188 of the heat exchange tube 154. Each riser 202 is shown as extending along a respective axis 224 that is substantially perpendicular to the longitudinal axis 204 (and in some examples, intersecting the axis 204).

[0084] The vapor phase working fluid 220 flows from the standpipe 202 into the collection pipe 200 and to the outlet manifold 160. Such as Figure 4 As shown in, the collection tube 200 may be substantially parallel to the heat exchange tube 154 and spaced apart from the heat exchange tube 154. The outlet manifold 160 is located upstream of the expander 84 in the cycle 70.

[0085] Such as Figure 4 It can be seen that the heat exchange tube 154 is located between the inlet header 158 and the outlet header 202 and between the inlet manifold 156 and the outlet manifold 160.

[0086] Such as figure 1 The controller 96 shown in can be used to control the circulation 70 and the closed loop so that the working fluid is in the liquid phase at the inlet of the pump 72 and in the vapor phase at the inlet of the expander 84. The controller 96 may be configured to control a closed loop or circulation such that the working fluid includes a vapor phase in the plurality of risers 202 and the working fluid includes a liquid phase in the inlet header 180.

[0087] For example, a conventional evaporator allows the working fluid to flow through a closed channel where the working fluid absorbs heat from the heat flow and evaporates into a gas. Due to its low thermal conductivity compared to liquid vapor, the vapor phase working fluid has reduced heat transfer efficiency. A conventional evaporator includes a flow path or a heat exchange cavity for a working fluid (for example, a circular steam engine) to travel up and down in the steam engine according to a sinusoidal curve. Since the density of the vapor is lower than that of the liquid, the liquid stays at the bottom of the channel and the vapor moves to the top causing a "hot spot", which can cause thermal fatigue and potential leakage problems of the evaporator.

[0088] The various examples of the present disclosure have associated, non-limiting advantages. For example, a heat exchanger for Rankine cycle or other thermal cycle in vehicles is provided. The heat exchanger has a heat exchange tube or cavity for using waste heat fluid (such as exhaust gas flowing around the heat exchange tube) to evaporate the working fluid in the cycle. As the working fluid evaporates in the heat exchange tube, the vapor phase and liquid phase of the working fluid separate and rise in the vertical outlet riser of the outlet header. The liquid phase of the working fluid remains in the heat exchange tube and continues to be heated by the waste heat fluid. The liquid retained in the heat exchange tube has high thermal conductivity and high heat transfer efficiency compared to the vapor phase. Due to the phase separation of the working fluid as the working fluid evaporates, the design of the heat exchanger makes the liquid cavity and the gas tube have a substantially uniform temperature distribution.

[0089] Although exemplary embodiments have been described above, it is not meant that these embodiments describe all possible forms of the present disclosure. On the contrary, the words used in the specification are words of description rather than limitation, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. In addition, the features of various implemented embodiments may be combined to form further embodiments of the present disclosure.