WO2021007202A1

WO2021007202A1 - Waste heat recovery system, coolant system, and control

Info

Publication number: WO2021007202A1
Application number: PCT/US2020/040998
Authority: WO
Inventors: Bhanu Teja Krishnavajjala; Timothy C. Ernst; Rohit Gupta; Srikanth ARAVAMUTHAN
Original assignee: Cummins Inc.
Priority date: 2019-07-08
Filing date: 2020-07-07
Publication date: 2021-01-14

Abstract

A system includes a coolant circuit, a waste heat recovery (WHR) circuit and a controller. The coolant circuit providing coolant to an engine includes a first coolant sub-circuit including a radiator valve and a radiator, and a second coolant sub-circuit including a WHR heat exchanger. The WHR system includes the WHR heat exchanger and a bypass valve coupled across the WHR heat exchanger. The controller coupled to the radiator valve and the bypass valve is configured to operate the bypass valve to direct working fluid into the heat exchanger if a coolant temperature is above a first threshold value, and operate the radiator valve to direct coolant from the second sub-circuit to the first sub-circuit if at least one of the coolant temperature is above a second threshold value, the working fluid temperature is above a third threshold value or the working fluid pressure is above a fourth threshold value.

Description

WASTE HEAT RECOVERY SYSTEM, COOLANT SYSTEM, AND CONTROL

FEDERAL FUNDING STATEMENT

[0001] This invention was made with government support under DE-EE0007761 awarded by the United States Department of Energy. The government has certain rights in the invention.

CROSS-REFERENCE TO RELATED APPLICATION

[0002] This application claims priority to, and the benefit of the filing date of U.S. Provisional Patent Application No. 62/871,350, filed July 8, 2019, the entire disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0003] The present disclosure relates to waste heat recovery (WHR) systems, and in particular to WHR systems used in conjunction with coolant systems.

BACKGROUND

[0004] A WHR system recovers heat energy that would otherwise be lost from a vehicle component or system, such as from an internal combustion engine of the vehicle. The more waste heat energy that is extracted from the component or system by a WHR system, the greater the potential efficiency of the engine. In other words, rather than the exhausted heat being lost, the extracted heat energy from waste heat sources may be repurposed to, e.g., supplement the power output from the internal combustion engine, thereby increasing the efficiency of the system. Some WHR systems use a Rankine cycle (RC), which is a thermodynamic process in which heat is transferred to a working fluid of the RC circuit. The working fluid is pumped through a heat exchanger where the working fluid is vaporized. The vapor is passed through an expander and then through a condenser, where the vapor is condensed back into liquid. The expander may drive a generator to generate electrical energy. An organic RC (ORC) is an RC in which the working fluid is an organic, high molecular mass fluid with a liquid-vapor phase change at a lower temperature than that of water. Such a fluid allows for heat recovery from lower temperature sources relative to other non-organic RC circuits.

SUMMARY

[0005] In one aspect, a system includes a coolant circuit, a waste heat recovery (WHR) circuit and at least one controller. The coolant circuit can provide coolant to an engine, the coolant circuit including a first coolant sub-circuit including a radiator valve and a radiator, and a second coolant sub-circuit including a WHR heat exchanger. The WHR circuit can include the WHR heat exchanger and a bypass valve coupled across the WHR heat exchanger. The at least one controller can be coupled to the radiator valve and the bypass valve, where the at least one controller is configured to operate the bypass valve to direct working fluid into the heat exchanger responsive to receiving an indication that a coolant temperature is above a first threshold value, and operate the radiator valve to direct coolant from the second sub-circuit to the first sub-circuit responsive to receiving indication of at least one of the coolant temperature is above a second threshold value, the working fluid temperature is above a third threshold value or the working fluid pressure is above a fourth threshold value.

[0006] In one or more embodiments, the coolant temperature is measured at a coolant outlet of the engine. In one or more embodiments, the working fluid temperature is measured at an input of an expander in the working fluid system. In one or more embodiments, the working fluid pressure is measured at an output of at least one of a condenser or a sub-cooler of the WHR system.

[0007] In another aspect, a method is provided for operating a coolant circuit and a waste heat recovery (WHR) circuit. The coolant circuit provides coolant to an engine, and includes a first coolant sub-circuit including a radiator valve and a radiator, and a second coolant sub circuit including a waste heat recovery (WHR) heat exchanger. The WHR circuit includes the WHR heat exchanger and a bypass valve coupled across the WHR heat exchanger. The method includes operating the bypass valve to direct working fluid into the heat exchanger responsive to receiving an indication that a coolant temperature is above a first threshold value, and operating the radiator valve to direct coolant from the second sub-circuit to the first sub-circuit responsive to receiving indication of at least one of the coolant temperature being above a second threshold value, the working fluid temperature being above a third threshold value or the working fluid pressure being above a fourth threshold value.

[0008] In still another aspect, a system includes a waste heat recovery (WHR) circuit providing a working fluid to a coolant heat exchanger, and a bypass circuit. The coolant heat exchanger allows heat transfer between the working fluid and a coolant of an engine. The WHR circuit can include a working fluid pump, a second heat exchanger, an expander, a condenser, and a sub-cooler. The working fluid pump can be fluidly coupled to the coolant heat exchanger. The coolant heat exchanger can be downstream of the working fluid pump so as to receive the working fluid from the working fluid pump. The second heat exchanger can be fluidly coupled to the coolant heat exchanger so as to receive the working fluid from at least one of the coolant heat exchanger and the working fluid pump. The expander can be fluidly coupled to the second heat exchanger downstream of the second heat exchanger so as to receive the working fluid from the second heat exchanger. The working fluid can drive a turbine of the expander. The condenser can be fluidly coupled to the expander downstream of the expander so as to receive the working fluid at a high temperature and condense the working fluid back to a liquid state. The sub-cooler can be fluidly coupled to the condenser downstream of the condenser so as to receive the working fluid from the condenser and provide the working fluid to the working fluid pump in a subcooled liquid state.

[0009] The bypass circuit can include a splitter and a bypass valve. The splitter can be fluidly coupled to the coolant heat exchanger upstream the coolant heat exchanger so as to split the working fluid flowing to the coolant heat exchanger. The bypass valve can be coupled to the splitter so as to control the flow of the working fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements).

[0011] Figure 1 shows an example system, according to an embodiment of the present disclosure.

[0012] Figure 2 shows a flow diagram of an example process to control the operation of the bypass valve shown in Figure 1.

[0013] Figure 3 shows a flow diagram of an example process to control the operation of the radiator valve shown in Figure 1.

[0014] The features and advantages of the inventive concepts disclosed herein will become more apparent from the detailed description set forth below when taken in conjunction with the drawings.

DETAILED DESCRIPTION

[0015] Following below are more detailed descriptions of various concepts related to, and embodiments of, inventive WHR systems and methods of operating WHR systems. It should be appreciated that various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the disclosed concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

[0016] WHR systems can recover thermal or other forms of energy in a vehicle that would otherwise be dissipated and lost to the environment, and help convert the energy into usable electrical or mechanical energy. In particular, the WHR systems can absorb heat generated by various components of a vehicle, such as, for example, the engine or the exhaust. The WHR system can use the absorbed heat to impart motion to a heated working fluid, which, in turn, can drive or rotate a driving shaft. The driving shaft can be coupled to a final drive (such as, for example, wheels) or can be coupled to a drive shaft of a motor/generator that can convert the imparted torque into electrical energy. In hybrid vehicles, the WHR system can provide the electrical energy for charging a battery, which, in turn, can provide power to one or more electrical motors that drive the vehicle.

[0017] Some WHR systems can include heat exchangers that exchange heat between a coolant used for cooling the engine and the working fluid. The vehicle can also include a radiator that exchanges heat between the coolant and the ambient environment. In some instances, the vehicle can include a coolant pump that pumps the coolant through a cooling circuit within the engine. The vehicle can also include a temperature controlled valve, positioned on or near the engine and within the coolant circuit, to control the flow of the coolant. For example, the temperature controlled valve can include a thermostat that senses the temperature of the coolant circulating through the engine, and based on the sensed temperature controls the coolant flow. If the temperature of the coolant is below a threshold value, the temperature controlled valve can circulate the coolant fluid within the engine by feeding the coolant back to the input of the coolant valve. The temperature of the coolant being below the threshold value can indicate that the engine is being adequately cooled by the coolant, and there therefore may not be a need to cool the coolant. As a result, the temperature controlled valve can direct the coolant back into an input of the coolant pump. If the temperature of the coolant is above a threshold value, then the coolant may not be adequately cooling the engine. To extract heat from the coolant, the temperature controlled valve can direct the coolant to the radiator or the WHR heat exchanger. The temperature controlled valve is generally installed on or near the engine and can include additional wiring and fluid lines connected thereto. The temperature controlled valve, in addition to the wiring and the fluid lines, can occupy valuable space in the vicinity of the engine. In addition, being installed on or near the engine can increase the risk of heat related damage to the valve, the wiring, or the fluid lines.

[0018] The WHR systems discussed herein provide a solution which alleviates the need for a thermostat and the accompanying wiring or fluid lines to be installed on or near the engine. Instead, the vehicle includes a heat exchanger bypass valve that allows bypassing the working fluid around the heat exchanger that receives the coolant. In addition, the vehicle includes a radiator valve that controls the distribution of the coolant between the heat exchanger and/or the radiator. The radiator valve and the heat exchanger bypass valve, separately or in combination, can control the coolant flow and temperature. One or more controllers can receive temperature and pressure values of the working fluid in the WHR system and can receive temperature values of the coolant. The one or more controllers, based on the temperature and pressure values, can actuate the radiator valve and the heat exchanger bypass valve to maintain the temperature of the coolant within a desired range of values, the temperature of the working fluid within a desired range of values, and maintain the pressure in the working fluid circuit to within a desired range of values.

[0019] Figure 1 shows an example system 100. The system 100 can include an engine coolant circuit 102 and a WHR circuit 104. The engine coolant circuit 102 includes a first coolant sub-circuit 106 and a second coolant sub-circuit 108. The first coolant sub-circuit 106 includes a radiator valve 122 and a radiator 112, and the second coolant sub-circuit 108 includes a coolant heat exchanger 114. A coolant pump 116 provides coolant to the first coolant sub circuit 106 and the second coolant sub-circuit 108. The coolant can be a heat transfer fluid and can comprise fluids such as ethylene glycol, propylene glycol, and water. The coolant pump 116 pumps coolant through an engine, which allows heat transfer between an engine 120 and the coolant. The coolant from the engine 120 is split into the first coolant sub-circuit 106 and the second coolant sub-circuit 108 at a splitter 124. In the first coolant sub-circuit 106, coolant from the engine 120 is provided to a radiator 112. The radiator 112 can cool the coolant by expelling heat from the coolant into the ambient environment. The coolant from the radiator 112 is provided back to the coolant pump 116. A radiator valve 122 is positioned in the first coolant sub-circuit 106 to control coolant flow to radiator 112. In the embodiment shown in Figure 1, the radiator valve 122 is positioned upstream of the radiator 1 12 and downstream of the splitter 124. In some embodiments, the radiator valve 122 can instead be positioned downstream of the radiator 112 and upstream of the coolant pump 116.

[0020] In the second coolant sub-circuit 108, the coolant is circulated through the coolant heat exchanger 114. Coolant from the splitter 124 is directed to a coolant channel in the coolant heat exchanger 114. The coolant heat exchanger 114 also includes a working fluid channel through which the working fluid of the WHR circuit 104 is passed. The coolant heat exchanger 114 allows heat transfer between the coolant and the working fluid. The coolant from the coolant channel of the coolant heat exchanger is provided back to an inlet of the coolant pump 116. [0021] The radiator valve 122 can be an on-off valve or a variable flow valve. When the radiator valve 122 is in a closed position, all the coolant from the engine heat exchanger 118 is directed to the second coolant sub-circuit 108, that is, to the coolant heat exchanger 114. In a partially open position, the radiator valve 122 directs a portion of the coolant to the radiator 112, thereby reducing the amount of coolant directed to the coolant heat exchanger 114. In a fully open position, the radiator valve 122 can direct substantially all of the coolant to the radiator 112.

[0022] The WHR circuit 104 includes a working fluid pump 126, the coolant heat exchanger 114, one or more additional heat exchangers 128, an expander 130, a condenser 132 and a sub-cooler 134. The working fluid pump 126 can be a fixed flow pump or a variable flow pump. In some embodiments, the WHR circuit 104 can include a bypass valve positioned across the working fluid pump 126 to allow changing the flow of the working fluid independently of the working fluid pump 126. The coolant heat exchanger 114 can be positioned downstream of the working fluid pump 126 and can receive the working fluid at the working fluid channel of the coolant heat exchanger 114. As mentioned above, the coolant heat exchanger 114 can allow heat transfer between the coolant and the working fluid. The working fluid at the output of the working fluid channel of the coolant heat exchanger is provided to a working fluid channel of the additional heat exchanger 128 positioned downstream of the coolant heat exchanger 114 or to an expander 130 positioned downstream of the coolant heat exchanger 114. The additional heat exchanger 128 (i.e., a second heat exchanger) may be in series or in parallel with the coolant heat exchanger 114. For example, the working fluid from the working fluid pump 126 may be received from either or both of the additional heat exchanger and the coolant heat exchanger 114. The working fluid can include a number of different fluids such as, for example, R1233zd(E), R245fa, other refrigerants, ethanol, toluene, water, and other fluids or blends of working fluids.

[0023] The working fluid from the additional heat exchanger 128 can be provided to an expander 130. The working fluid can be in a vapor state when entering the expander 130. Within the expander 130, the working fluid expands and loses pressure, thereby driving a turbine of the expander 130 to generate useful work. The turbine, in turn, can be coupled to a generator to convert the mechanical energy into electrical energy. In some embodiments, the turbine of the expander can be coupled to a crankshaft of the engine 120, an engine accessory shaft, and/or other components, such as, for example, via a gear or belt drive so as to transfer the mechanical energy from the turbine to those devices. According to various embodiments, the expander 130 can include a piston expander, a screw expander, a scroll expander, a gerotor expander, or other type of expander. In some embodiments, the expander 130 can have variable geometry input nozzles. The variable geometry nozzle can be adjusted to change the flow rate verses the pressure characteristics of the expander.

[0024] The condenser 132 and the sub-cooler 134 can be positioned downstream of the expander 130. The condenser 132 is structured to receive a high temperature working fluid and transfer heat from the working fluid to the ambient environment, thereby substantially or fully condensing the working fluid back to a liquid state. In some embodiments, the condenser 132 can be at least partially air cooled, and can be positioned off-engine in a vehicle cooling package area structured to receive ram air.

[0025] The sub-cooler 134 is positioned downstream of the condenser 132. The sub-cooler 134 is structured to ensure that the working fluid is in a subcooled liquid state before being provided to the working fluid pump 126. Ensuring that the working fluid is in the liquid state reduces the risk of cavitation in the pumps, thereby improving the performance and the reliability of the working fluid pump 126. In some embodiments, the WHR circuit 104 can include a receiver coupled to the condenser where the receiver serves as a reservoir for the working fluid. Flow in and out of the receiver can be controlled to control the flow rate of working fluid through the sub-cooler 134 and fluid inventory in the condenser 132.

[0026] A splitter 136 can be positioned upstream of the coolant heat exchanger 114. The splitter 136 can split the working fluid directed to the coolant heat exchanger to a bypass circuit

138. A bypass valve 140 can control the flow of working fluid into the bypass circuit 138. For example, the bypass valve 140 can be opened to allow at least a portion of the working fluid flowing into the coolant heat exchanger 114 to instead flow into the bypass circuit 138. The bypass valve 140 can be an on-off valve or a flow control valve. In a closed position, the bypass valve 140 blocks any flow of the working fluid in the bypass circuit 138, thereby allowing all of the working fluid at the splitter 136 to flow through the coolant heat exchanger. In a partially open position, the bypass valve 140 can direct a portion of the working fluid at the splitter 136 to the bypass circuit 138, thereby reducing the proportion of working fluid flowing to the coolant heat exchanger 114. In a fully open position, the bypass valve 140 can direct substantially all of the working fluid through the bypass circuit 138.

[0027] The system 100 also can include one or more temperature and pressure sensors. For example, the system 100 can include a coolant temperature sensor 142 for sensing the temperature of the coolant in the coolant circuit 102. As shown in Figure 1, the coolant temperature sensor 142 is positioned at the outlet of the engine heat exchanger. In this position, sensing the temperature of the coolant can provide information about an operating temperature of the engine 120. However, the coolant temperature sensor 142 could be placed at other locations within the coolant circuit 102 as well, such as, for example, at the inlet or outlet of the coolant pump 116. In some embodiments, the system 100 can include additional temperature sensors positioned at the inlet and/or outlet of the radiator 112, at the inlet and/or outlet of the coolant channel of the coolant heat exchanger 114, or at any other location within the coolant circuit 102.

[0028] The system 100 also can include temperature sensors in the WHR circuit 104. For example, a working fluid temperature sensor 144 may be positioned at an inlet of the expander 130 to measure the temperature of the working fluid at the expander 130. The system 100 also can include a working fluid pressure sensor 148 positioned at an outlet of the sub-cooler 134 or the condenser 132. Maintaining the temperature and the pressure of the working fluid within specified ranges of values can allow for efficient operation of the WHR circuit 104. For example, maintaining the working fluid in a superheated state at the inlet of the expander 130 can increase the efficiency of the WHR circuit 104, increase the power output of the expander 130, and also reduce the risk of condensation within the expander 130— thereby reducing the risk of damage to the expander 130 due to liquid droplets. In addition, maintaining the working fluid at the outlet of the condenser 132 or the sub-cooler 134 in subcooled conditions (certain temperature and pressure range based, in part, on the type of working fluid) can increase the amount of cooling provided to the working fluid as well as ensure the working fluid is in the liquid state when it enters the working fluid pump 126 (thereby improving the reliability of the working fluid pump 126). [0029] The system 100 can further include a controller 150, several sensors, and several actuators. For example, the sensors can include temperature and pressure sensors, and actuators can include valves. The sensors and valves can be communicably coupled to the controller 150. In particular, the sensors can provide the controller 150 with values of the measured parameters, and the valves can receive actuating signals from the controller to actuate the valves. As shown in Figure 1, the system 100 includes sensors such as the coolant temperature sensor 142, the working fluid temperature sensor 144, and the working fluid pressure sensor 148, each of which can be communicably coupled with the controller 150. The system 100 also includes a radiator valve 122 and a working fluid bypass valve 140, each of which also can be communicably coupled to the controller 150. The controller 150 can receive the inputs from the sensors and based, in part, on the inputs, can actuate one or more of the valves. In some embodiments, the controller 150 can include an engine control unit or module and a WHR control unit or module.

[0030] Figure 2 shows a flow diagram of an example process 200 to control the operation of the bypass valve shown in Figure 1. Figure 3 shows a flow diagram of an example process 300 to control the operation of the radiator valve shown in Figure 1. It is desirable to maintain the temperature of the coolant in the coolant circuit 102 and the temperature and pressure of the working fluid in the WHR circuit 104. Further, it is desirable to utilize as much energy from the coolant in generating power using the WHR circuit 104. The controller 150 can execute the processes 200 and 300 to maintain the desired conditions of the system 100.

[0031] Referring to Figure 2, the process 200 can include directing working fluid away from a heat exchanger receiving a coolant (202). Referring to Figure 1, the heat exchanger can be the coolant heat exchanger 114, which receives the coolant from the coolant circuit 102. The controller can direct working fluid away from the coolant heat exchanger 114 by at least partially opening the bypass valve 140. This process step can be assumed to be executed by the controller 150 when the temperature of the coolant is below a threshold value. For example, when the engine 120 is initially started, the temperature of the coolant is typically low. The controller 150 can control the bypass valve at the start of the engine 120 to direct the working fluid away from the coolant heat exchanger 114. During this time, the controller 150 may also close the radiator valve 122, causing the coolant to be directed to the coolant channel of the coolant heat exchanger 114. As the coolant is blocked from exchanging heat with either the radiator 112 or the working fluid in the heat exchanger, the coolant temperature rises quickly.

[0032] In some embodiments, where the bypass valve 140 is an on-off valve, the controller 150 can turn on the bypass valve 140 such that all the working fluid at the splitter 136 is directed to the bypass circuit 138 and away from the coolant heat exchanger 114. In some embodiments, where the bypass valve 140 is a variable flow valve, the controller 150 can at least partially open the bypass valve 140 to direct a portion of the working fluid entering the splitter 136 into the bypass circuit 138 and away from the coolant heat exchanger 114. The controller 150 may also completely open the variable flow bypass valve 140 to direct all of the working fluid at the splitter 136 to the bypass circuit 138 and away from the coolant heat exchanger 114.

[0033] The process 200 includes receiving the coolant temperature Tcooler (204). The controller 150 can receive the coolant temperature from one or more temperature sensors in the coolant circuit 102. For example, the controller 150 can receive the coolant temperature Tcooler from the coolant temperature sensor 142 positioned at the outlet of the engine heat exchanger 118 as shown in Figure 1. In some embodiments, the controller 150 can determine Tcooler based only on input received from the coolant temperature sensor 142. In some embodiments, the controller 150 can determine the coolant temperature Tcooler based on input from additional temperature sensors positioned in other locations in the coolant circuit 102.

[0034] The process 200 includes determining whether the coolant temperature is greater than a first threshold temperature T1 (206). The first threshold temperature T1 value can be predetermined and stored in a memory coupled to the controller 150. In some embodiments, the first threshold temperature can indicate the temperature over which the coolant temperature can provide useful heat to working fluid in the WHR circuit 104. If the controller determines that the temperature Tcooler of the coolant is less than the first threshold temperature Tl, the controller can continue to direct working fluid away from the coolant heat exchanger 114.

[0035] The process 200 includes directing the working fluid to the heat exchanger receiving the coolant (208) if the controller 150 determines that the coolant temperature Tcooler is greater than the first threshold temperature Tl . As an example, after the engine 120 has been running for a certain period of time after start up, the coolant temperature can begin to rise. When the coolant temperature increases above the first threshold temperature Tl, the coolant can provide useful heat to the working fluid. The controller 150, by directing the working fluid through the coolant heat exchanger 114, allows the heat from the coolant to raise the temperature of the working fluid, and, in turn, causes the temperature of the coolant to reduce. The process 200 can direct the working fluid to the coolant heat exchanger 114 by closing the bypass valve 140. In some embodiments, where the bypass valve 140 is an on-off valve, the controller 150 can switch off the bypass valve 140 to allow all of the working fluid at the splitter 136 to be directed to the coolant heat exchanger 114. In some embodiments where the bypass valve 140 is a variably flow valve, the controller 150 can control the bypass valve to at least partially close the bypass valve 140 to direct an increasing amount of working fluid to the coolant heat exchanger 114. As mentioned above, the transfer of heat from the coolant to the working fluid can reduce the temperature of the coolant in the coolant circuit 102. This allows the cooling of the coolant in the coolant circuit 102 without having to go through the radiator 112.

[0036] The controller 150 can continue to direct working fluid to the coolant heat exchanger 114 while the coolant temperature is above the first threshold temperature Tl . In some embodiments, where the bypass valve 140 is a variable flow valve, the controller 150 can incrementally increase the amount of working fluid directed to the coolant heat exchanger 114. If the controller 150 determines that the coolant temperature is below the first threshold temperature Tl, the controller 150 can incrementally increase the amount of working fluid directed away from the coolant heat exchanger 114.

[0037] By directing the working fluid away from the coolant heat exchanger 114, the coolant temperature can rise relatively quickly than if working fluid was allowed to flow through the heat exchanger. Once the coolant temperature reaches the desired value (e.g., the first threshold temperature Tl), the coolant is allowed to provide heat to the working fluid, and increase the power generated by the WHR circuit 104. Shortening the time in which the coolant temperature rises to a desired value can increase the efficiency of the engine 120.

[0038] Figure 3 shows a flow diagram of an example process 300 to control the operation of the radiator valve 122 shown in Figure 1. The controller 150 can execute the process 300 simultaneously with the execution of the process 200 discussed above in relation to Figure 2.

The process 300 includes closing the radiator valve (302). The controller 150, at engine 120 start up, can close the radiator valve 122, such that coolant is directed to the second coolant sub-circuit 108 including the coolant heat exchanger 114 and away from the first coolant sub circuit 106 including the radiator 112. At engine 120 startup, the coolant in the coolant circuit 102 can have a low temperature. Directing the coolant to the second coolant sub-circuit 108 to the coolant heat exchanger 114 directing the working fluid to the bypass circuit 138 can allow for quickly raising the coolant temperature. As mentioned above, quickly raising the coolant temperature can allow for using the coolant heat to generate power using the WHR circuit 104, and thereby improving the efficiency of the system 100.

[0039] The process 300 includes receiving the coolant temperature Tcooler, the working fluid temperature Twf, and the working fluid pressure Pwf (304). The controller 150 can receive the coolant temperature and the working fluid temperature and pressure from various locations in the coolant circuit 102 and the WHR circuit 104. For example, the controller 150 receives the coolant temperature Tcoolant from the coolant temperature sensor 142 positioned at the outlet of the engine heat exchanger 118, receives working fluid temperature Twf from the working fluid temperature sensor 144 positioned at the inlet of the expander 130, and receives the working fluid pressure Pwf from the working fluid pressure sensor 148 positioned at the output of the condenser 132 or the sub-cooler 134. In some embodiments, the controller 150 can receive determine the coolant temperature based on input received from multiple temperature sensors positioned on the coolant circuit 102. Similarly, the controller 150 can determine the working fluid temperature and pressure based on temperature and pressure readings received from multiple temperature sensors and multiple pressure sensors positioned at various locations in the WHR circuit 104.

[0040] The process 300 includes determining whether the coolant temperature Tcooler is greater than a second threshold temperature T2 (306), whether the working fluid temperature Twf is greater than a third threshold temperature T3 (308), or whether the working fluid pressure is greater than a first threshold pressure PI (310). The second threshold temperature T2, the third threshold temperature T3, and the first threshold pressure PI can be pre-determined and stored in memory accessible by the controller 150. If the controller 150 determines that coolant temperature Tcooler is greater than the second threshold temperature T2, the controller 150 can open the radiator valve (312) to direct coolant from the second coolant sub-circuit 108 including the coolant heat exchanger 114 to the first coolant sub-circuit 106 including the radiator 112.

[0041] During engine start up, the working fluid is directed to the coolant heat exchanger 114 after the coolant temperature is greater than the first threshold temperature, as discussed above in relation to Figure 2. However, the engine 120 may generate heat that is greater than the heat exchanged with the working fluid in the coolant heat exchanger 114. As a result, the coolant temperature can rise. While coolant temperature can be allowed to rise above the first threshold temperature Tl, it is desirable to maintain the coolant temperature to below a value (e.g., the second threshold temperature T2) at which the coolant is considered to be inadequate in cooling to the engine 120. If the temperature of the coolant rises above that value, the controller 150 can determine that the cooling provided by the coolant heat exchanger is not sufficient. To provide additional cooling to the coolant, the controller 150 can open the radiator valve 122 so that at least a portion of the coolant at the splitter 124 is directed to the radiator 112. The combined cooling provided by the coolant heat exchanger 114 and the radiator 112 reduce the temperature of the coolant to desirable levels. In some embodiments, the controller 150 can incrementally open the radiator valve 122 until the coolant temperature Tcooler is below the second threshold temperature T2. In some embodiments, the second threshold temperature T2 can be based on the specified maximum operating temperature of the engine 120. As an example, the second threshold temperature T2 can have a value between 50 degrees centigrade and 110 degrees centigrade, or 107 degrees centigrade.

[0042] The controller 150 can also consider the condition of the WHR circuit 104 to determine whether to open or close the radiator valve 122. As mentioned above, it is desirable to maintain the temperature and pressure of the working fluid in the WHR circuit 104 within certain range of values. During operation, when the working fluid is passed through the coolant heat exchanger 114, the coolant temperature can cause the temperature and pressure of the working fluid to rise above the desired range of values. One option to reducing the working fluid temperature or pressure involves bypassing the working fluid away from the coolant heat exchanger 114. In another approach, the controller 150 can open the radiator valve 122 such that a smaller amount of coolant is directed towards the coolant heat exchanger 114, thereby reducing the amount of heat being transferred to the working fluid the WHR circuit 104. Further, by directing the coolant to the radiator 112, the radiator 112 can provide cooling to the coolant that would otherwise had been provided by the coolant heat exchanger 114.

[0043] The coolant can open the radiator valve 122 based on either the working fluid temperature Twf or the working fluid pressure Pwf being above the third threshold temperature T3 and the first threshold pressure PI, respectively. By measuring the working fluid temperature Twf at the input of the expander 130, the controller 150 can ensure that the working fluid is in the desired vapor state. By measuring the working fluid pressure Pwf at the output of the condenser 132 or the sub-cooler 134 can ensure that the working fluid is in the desired liquid state when it enters the working fluid pump 126. In some embodiments, the third threshold temperature T3 can have a value between 200 degrees centigrade and 240 degrees centigrade, or 220 degrees centigrade. In some embodiments, the first threshold pressure PI can have a value between 350 KPa and 450 KPa, or 400 Kpa. The third threshold temperature T3 and the first threshold pressure PI can be selected based, in part, on the type of working fluid used and the corresponding characteristic saturation curve of the working fluid.

[0044] If the controller 150 determines that none of the conditions are met: whether the coolant temperature Tcooler is greater than a second threshold temperature T2 (306), whether the working fluid temperature Twf is greater than a third threshold temperature T3 (308), or whether the working fluid pressure is greater than a first threshold pressure PI (310), the controller can close the radiator valve 302 and allow more or all of the coolant to flow through the coolant heat exchanger 114. As a result, the heat generated by the coolant is utilized by the WHR circuit 104 instead of being lost in the ambient environment by the radiator 112.

[0045] The controller 150 executing the process 300 can provide an efficient utilization of the coolant heat in generating power using the WHR circuit 104 while ensuring that the operation of both the coolant circuit 102 and the WHR circuit 104 is maintained within the desired parameters. Further, the system 100 can be devoid of the temperature controlled valve (thermostat) and the accompanying wiring or fluid lines to be installed on or near the engine, thereby improving the reliability of the system 100.

[0046] For the purpose of this disclosure, the term“coupled” means the joining of two members directly or indirectly to one another. Such joining may be stationary or moveable in nature. Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another. Such joining may be permanent in nature or may be removable or releasable in nature.

[0047] It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure. It is recognized that features of the disclosed embodiments can be incorporated into other disclosed embodiments.

[0048] It is important to note that the constructions and arrangements of apparatuses or the components thereof as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter disclosed. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present disclosure.

[0049] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other mechanisms and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that, unless otherwise noted, any parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.

[0050] Also, the technology described herein may be embodied as a method, of which at least one example has been provided. The acts performed as part of the method may be ordered in any suitable way unless otherwise specifically noted. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

[0051] The claims should not be read as limited to the described order or elements unless stated to that effect. It should be understood that various changes in form and detail may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims. All embodiments that come within the spirit and scope of the following claims and equivalents thereto are claimed.

Claims

1. A system including:

a coolant circuit providing coolant to an engine, the coolant circuit including a first coolant sub-circuit including a radiator valve and a radiator, and a second coolant sub-circuit including a waste heat recovery (WHR) heat exchanger;

a WHR circuit including the WHR heat exchanger and a bypass valve coupled across the WHR heat exchanger; and

at least one controller coupled to the radiator valve and the bypass valve, the at least one controller configured to:

operate the bypass valve to direct working fluid into the WHR heat exchanger responsive to receiving an indication that a coolant temperature is above a first threshold value, and

operate the radiator valve to direct coolant from the second sub-circuit to the first sub-circuit responsive to receiving indication of at least one of the coolant temperature is above a second threshold value, a working fluid temperature is above a third threshold value or a working fluid pressure is above a fourth threshold value.

2. The system of claim 1, wherein the WHR circuit further includes a second heat exchanger and an expander fluidly coupled to the WHR heat exchanger, the expander receiving the working fluid directed away from the WHR heat exchanger by the bypass valve.

3. The system of claim 1, wherein the coolant temperature is measured at a coolant outlet of the engine.

4. The system of claim 2, wherein the working fluid temperature is measured at an input of the expander in the WHR circuit.

5. The system of claim 1, wherein the working fluid pressure is measured at an output of at least one of a condenser or a sub-cooler of the WHR circuit.

6. The system of claim 1, wherein the WHR circuit further includes a plurality of sensors configured to indicate the coolant temperature, the working fluid temperature, and the working fluid pressure.

7. The system of claim 1, wherein the radiator valve is an on-off valve.

8. The system of claim 1, wherein the radiator valve is a variable flow valve.

9. A method of operating a coolant circuit and a waste heat recovery (WHR) circuit, the coolant circuit providing coolant to an engine, and including a first coolant sub-circuit including a radiator valve and a radiator, and a second coolant sub-circuit including a waste heat recovery (WHR) heat exchanger, the WHR circuit including the WHR heat exchanger and a bypass valve coupled across the WHR heat exchanger, the method comprising:

operating the bypass valve to direct working fluid into the WHR heat exchanger responsive to receiving an indication that a coolant temperature is above a first threshold value, and

operating the radiator valve to direct coolant from the second sub-circuit to the first sub-circuit responsive to receiving indication of at least one of the coolant temperature being above a second threshold value, a working fluid temperature being above a third threshold value or a working fluid pressure being above a fourth threshold value.

10. The method of claim 9, wherein the working fluid is directed away from the WHR heat exchanger by at least partially opening the bypass valve when the coolant temperature is below the first threshold value.

11. The method of claim 10, wherein the working fluid directed away from the WHR heat exchanger is directed to a second heat exchanger or to an expander positioned downstream of the WHR heat exchanger.

12. The method of claim 9, wherein the coolant is directed to the second sub-circuit by closing the radiator valve when the coolant temperature is below the second threshold value.

13. The method of claim 9, wherein the indication that the coolant temperature is above the first threshold value is received from a coolant temperature sensor positioned at an outlet of a heat exchanger of the engine.

14. The method of claim 9, wherein the indication of the coolant temperature being above the second threshold value is received from a coolant temperature sensor positioned at an outlet of a heat exchanger of the engine.

15. The method of claim 9, wherein the indication of the working fluid temperature being above the third threshold value is received from a working fluid temperature sensor positioned at an inlet of an expander of the WHR circuit.

16. The method of claim 9, wherein the indication of the working fluid pressure being above the fourth threshold value is received from a working fluid pressure sensor positioned at an output of a condenser or sub-cooler of the WHR circuit.

17. A system comprising:

a waste heat recovery (WHR) circuit providing a working fluid to a coolant heat exchanger to allow heat transfer between the working fluid and a coolant of an engine, the WHR circuit including: a working fluid pump fluidly coupled to the coolant heat exchanger, the coolant heat exchanger downstream of the working fluid pump so as to receive the working fluid from the working fluid pump;

a second heat exchanger fluidly coupled to the coolant heat exchanger so as to receive the working fluid from at least one of the coolant heat exchanger and the working fluid pump;

an expander fluidly coupled to the second heat exchanger downstream of the second heat exchanger so as to receive the working fluid from the second heat exchanger, wherein the working fluid drives a turbine of the expander;

a condenser fluidly coupled to the expander downstream of the expander so as to receive the working fluid at a high temperature and condense the working fluid back to a liquid state; and

a sub-cooler fluidly coupled to the condenser downstream of the condenser so as to receive the working fluid from the condenser and provide the working fluid to the working fluid pump in a subcooled liquid state; and

a bypass circuit, including:

a splitter fluidly coupled to the coolant heat exchanger upstream the coolant heat exchanger so as to split the working fluid flowing to the coolant heat exchanger; and

a bypass valve coupled to the splitter so as to direct the flow of the working fluid.

18. The system of claim 17, further comprising at least one controller coupled to the bypass valve, the at least one controller configured to operate the bypass valve to direct the working fluid into the heat exchanger responsive to receiving an indication that a coolant temperature is above a first threshold value.

19. The system of claim 18, further comprising a coolant temperature sensor configured to sense the coolant temperature for determining if the coolant temperature is above the first threshold value.

20. The system of claim 19, wherein the coolant temperature sensor is positioned at a coolant outlet of an engine fluidly coupled to the coolant heat exchanger.

21. The system of claim 17, further comprising a receiver fluidly coupled to the condenser, the receiver configured to control the flow rate of the working fluid.

22. The system of claim 17, wherein the bypass valve is positioned across the working fluid pump, the bypass valve configured to control the flow of the working fluid independently of the working fluid pump.