Exhaust heat recovery system

Abstract

An exhaust heat recovery system ( 10 ) includes an exhaust heat recovery heat exchanger ( 18 ) in which heat is transferred from exhaust gas discharged from an internal combustion engine ( 12 ) to an engine coolant for cooling the internal combustion engine ( 12 ), and a heat pump system ( 22 ) for recovering exhaust heat of exhaust gas. The heat pump system ( 22 ) includes a refrigerant circulation passage ( 24 ) for circulating CO2 refrigerant, a heat-absorbing heat exchanger ( 32 ) in which heat is transferred from exhaust gas to the CO2 refrigerant, and a heat-releasing heat exchanger ( 28 ) in which the exhaust heat recovered by heat transfer to the CO2 refrigerant in the heat-releasing heat exchanger ( 32 ) is recovered.

1 . An exhaust heat recovery system comprising:
 an exhaust heat recovery heat exchanger in which heat is transferred from exhaust gas discharged from an internal combustion engine to a coolant for cooling the internal combustion engine; and   a heat pump including:
 a circulation passage for a refrigerant; 
 a heat-absorbing heat exchanger in which the heat is transferred from the exhaust gas to the refrigerant; and 
 a heat-releasing heat exchanger in which the heat is transferred from the refrigerant to the coolant, directly to a circulation passage for the coolant, 
   wherein said heat-releasing heat exchanger is disposed upstream of exhaust heat recovery heat exchanger in the circulation passage for the coolant.   
   
   
       2 . The exhaust heat recovery system according to  claim 1 , wherein the heat-absorbing heat exchanger of the heat pump is disposed downstream of the exhaust heat recovery heat exchanger in a flowing direction of the exhaust gas. 
   
   
       3 . The exhaust heat recovery system according to  claim 1 , wherein the coolant is circulated by a pump driven by a power from the internal combustion engine. 
   
   
       4 . The exhaust heat recovery system according to  claim 1 , further comprising:
 an exhaust heat recovery switching device switchable between an exhaust heat recovery state where exhaust heat of the exhaust gas is recovered and a discharge state where the exhaust gas is discharged to an outside,   wherein the exhaust gas flows through the exhaust heat recovery heat exchanger and the heat-absorbing heat exchanger by switching the exhaust heat recovery switching device from the discharge state to the exhaust heat recovery state.   
   
   
       5 . The exhaust heat recovery system according to  claim 4 , further comprising:
 a control device that switches the exhaust heat recovery switching device to the exhaust heat recovery state when a temperature of the coolant is lower than a predetermined temperature, and switches the exhaust heat recovery switching device to the discharge state when the temperature of the coolant is equal to or higher than the predetermined temperature.   
   
   
       6 . The exhaust heat recovery system according to  claim 4 , wherein the heat pump includes a compressor that compresses the refrigerant to which the heat has been transferred in the heat-absorbing heat exchanger,
 said exhaust heat recovery system further comprising:   a control device that switches the exhaust heat recovery switching device to the exhaust heat recovery state and operates the compressor when the temperature of the coolant is lower than the predetermined temperature.   
   
   
       7 . The exhaust heat recovery system according to  claim 6 , wherein the control device controls the exhaust heat recovery switching device to the discharge state and controls the compressor to a stopped state when the temperature of the coolant is equal to or higher than the predetermined temperature. 
   
   
       8 . The exhaust heat recovery system according to  claim 1 , further comprising:
 a heater core that is disposed upstream of the exhaust heat recovery heat exchanger in the circulation passage for the coolant and heats air for air conditioning,   wherein the heat-releasing heat exchanger of the heat pump is disposed downstream of the heater core in the circulation passage for the coolant.   
   
   
       9 . An exhaust heat recovery system comprising:
 an exhaust heat recovery heat exchanger in which heat is transferred from exhaust gas discharged from an internal combustion engine to a coolant for cooling the internal combustion engine; and   a heat pump including:
 a circulation passage for a refrigerant; 
 a heat-absorbing heat exchanger in which the heat is transferred from the exhaust gas to the refrigerant; and 
   a heat-releasing heat exchanger in which the heat is transferred from the refrigerant to an air for air conditioning,   wherein said exhaust heat recovery system further comprises:   a heat pump switching device switchable between an air supply state where the air for air conditioning is supplied to the heat-releasing heat exchanger and a heat pump bypass state where the air for air conditioning is not supplied to the heat-releasing heat exchanger.   
   
   
       10 . The exhaust heat recovery system according to  claim 9 , further comprising:
 a heater core that is provided in the circulation passage for the coolant and heats the air for air conditioning; and   a heater core switching device switchable between an air supply state where the air for air conditioning is supplied to the heater core and a heater core bypass state where the air for air conditioning is not supplied to the heater core.   
   
   
       11 . The exhaust heat recovery system according to  claim 9 , wherein the heater core switching device is switched to the heater core bypass state when the heat pump is operated, and the heat pump switching device is switched to the heat pump bypass state when the heat pump is stopped. 
   
   
       12 . The exhaust heat recovery system according to  claim 9 , further comprising:
 an exhaust heat recovery switching device switchable between an exhaust heat recovery state where the exhaust heat of the exhaust gas is recovered and a discharge state where the exhaust gas is discharged to an outside; and   a control device that switches the exhaust heat recovery switching device to the exhaust heat recovery state and switches the heater core switching device to the heater core bypass state when a temperature of the coolant is lower than a predetermined temperature.   
   
   
       13 . The exhaust heat recovery system according to  claim 9 , wherein the heat pump includes a compressor that compresses the refrigerant to which the heat has been transferred in the heat-absorbing heat exchanger, said exhaust heat recovery system further comprising:
 an exhaust heat recovery switching device switchable between an exhaust heat recovery state where exhaust heat of the exhaust gas is recovered and a discharge state where the exhaust gas is discharged to an outside; and   a control device that switches the exhaust heat recovery switching device to the exhaust heat recovery state and operates the compressor if a request for heating the air for air conditioning is made when a temperature of the coolant is lower than a predetermined temperature.   
   
   
       14 . The exhaust heat recovery system according to  claim 13 , wherein the control device switches the heater core switching device to the heater core bypass state if the request for heating is made when the temperature of the coolant is lower than the predetermined temperature. 
   
   
       15 . The exhaust heat recovery system according to  claim 13 , wherein the control device controls the exhaust heat recovery switching device to the discharge state and controls the compressor to a stopped state when the temperature of the coolant is equal to or higher than the predetermined temperature. 
   
   
       16 . The exhaust heat recovery system according to  claim 15 , wherein the control device controls the heat pump switching device to the heat pump bypass state when the temperature of the coolant is equal to or higher than the predetermined temperature.