Rankine cycle apparatus and method for controlling rankine cycle apparatus

Abstract

A Rankine cycle apparatus includes: a sensor; a pump; an evaporator; an expander; a condenser; and a fluid circuit through which a working fluid flows. The fluid circuit includes a circulation circuit in which the pump, the evaporator, the expander, and the condenser are provided in this order. The sensor is configured to detect one of (I) a pressure of the working fluid, (II) a temperature of the working fluid, and (III) a temperature of a coding medium to be heat-exchanged with the working fluid in the condenser. First control is started if a detected value of the sensor is less than a first threshold value, the first control is control to cause the pump to circulate the working fluid through the evaporator and/or a heater.

What is claimed is: 
     
         1 . A Rankine cycle apparatus comprising:
 a sensor; a pump; an evaporator; an expander; a condenser; and   a fluid circuit through which a working fluid flows, the fluid circuit including a circulation circuit in which the pump, the evaporator, the expander, and the condenser are provided in this order,   wherein the sensor is configured to detect one of (I) a pressure of the working fluid, (II) a temperature of the working fluid, and (III) a temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser,   wherein first control is started if a detected value of the sensor is less than a first threshold value, the first control is control to cause the pump to circulate the working fluid through the evaporator and/or a heater.   
     
     
         2 . The Rankine cycle apparatus according to  claim 1 , wherein (i) the sensor is configured to detect the pressure of the working fluid, and the first threshold value is a pressure higher than or equal to the atmospheric pressure,
 wherein (ii) the sensor is configured to detect the temperature of the working fluid, and the first threshold value is a temperature higher than or equal to the boiling point of the working fluid at atmospheric pressure, or   wherein (iii) the sensor is configured to detect the temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser, and the first threshold value is a temperature higher than or equal to the boiling point of the working fluid at atmospheric pressure.   
     
     
         3 . The Rankine cycle apparatus according to  claim 1 , wherein the sensor is configured to detect the pressure of the working fluid in a portion of the circulation circuit that is downstream of the expander and upstream of the pump. 
     
     
         4 . The Rankine cycle apparatus according to  claim 1 , wherein the fluid circuit includes a bypass circuit configured to connect a portion of the circulation circuit that is downstream of the evaporator and upstream of the expander to a portion of the circulation circuit that is downstream of the expander and upstream of the condenser, the working fluid is circulated through the bypass circuit in the first control. 
     
     
         5 . The Rankine cycle apparatus according to  claim 4 , wherein a valve is provided in the bypass circuit, an opening degree of the valve is set to 50% or more and 100% or less in the first control. 
     
     
         6 . The Rankine cycle apparatus according to  claim 1 , wherein the heater is provided in the fluid circuit; the working fluid is circulated through the evaporator in the first control, and the heater is configured to start generating heat if the detected value is less than a second threshold value and an elapsed time from the start of the first control is greater than or equal to a threshold time. 
     
     
         7 . The Rankine cycle apparatus according to  claim 1 , wherein driving of the pump is stopped if the detected value is greater than or equal to a second threshold value. 
     
     
         8 . The Rankine cycle apparatus according to  claim 1 , wherein the boiling point of the working fluid at atmospheric pressure is 0° C. or higher and 50° C. or lower. 
     
     
         9 . The Rankine cycle apparatus according to  claim 1 , further comprising:
 an electric generator configured to generate electric power by rotation torque of the expander.   
     
     
         10 . A method for controlling a Rankine cycle apparatus; the Rankine cycle apparatus configured to circulate a working fluid through a pump, an evaporator; an expander; and a condenser in this order, the method comprising:
 detecting, by using a sensor, one of (I) a pressure of the working fluid, (II) a temperature of the working fluid, and (III) a temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser; and   starting first circulation to cause the pump to circulate the working fluid in a heated state if a detected value of the sensor is less than a first threshold value.   
     
     
         11 . The method according to  claim 10 , wherein (i) the sensor is configured to detect the pressure of the working fluid, and the first threshold value is a pressure higher than or equal to the atmospheric pressure,
 wherein (ii) the sensor is configured to detect the temperature of the working fluid, and the first threshold value is a temperature higher than or equal to the boiling point of the working fluid at atmospheric pressure, or   wherein (iii) the sensor is configured to detect the temperature of a cooling medium to be heat-exchanged with the working fluid in the condenser, and the first threshold value is a temperature higher than or equal to the boiling point of the working fluid at atmospheric pressure.   
     
     
         12 . The method according to  claim 10 , wherein the Rankine cycle apparatus includes a circulation circuit in which the pump, the evaporator, the expander, and the condenser are provided in this order, and
 wherein the sensor is configured to detect a pressure of the working fluid in a portion of the circulation circuit that is downstream of the expander and upstream of the pump.   
     
     
         13 . The method according to  claim 10 , wherein the Rankine cycle apparatus includes a circulation circuit in which the pump, the evaporator, the expander, and the condenser are provided in this order and a bypass circuit configured to connect a portion of the circulation circuit that is downstream of the evaporator and upstream of the expander to a portion of the circulation circuit that is downstream of the expander and upstream of the condenser, and
 wherein the working fluid passes through the bypass circuit in the first circulation.   
     
     
         14 . The method according to  claim 13 , wherein a valve is provided in the bypass circuit, an opening degree of the valve of the bypass circuit is set to 50% or more and 100% or less in the first circulation. 
     
     
         15 . The method according to  claim 10 , wherein the working fluid is heated by the evaporator and/or a heater in the first circulation. 
     
     
         16 . The method according to  claim 10 , wherein the working fluid is heated by the evaporator in the first circulation, and
 wherein the method further comprises starting heating the working fluid by the heater if the detected value is less than a second threshold value and an elapsed time from the start of the first circulation is greater than or equal to a threshold time.   
     
     
         17 . The method according to  claim 10 , further comprising:
 stopping the driving of the pump if the detected value is greater than or equal to a second threshold value.   
     
     
         18 . The method according to  claim 10 , wherein the boiling point of the working fluid at atmospheric pressure is 0° C. or higher and 50° C. or lower.