Rankine cycle system and method of controlling the same

A Rankine cycle system for generating electricity, comprising:

• an evaporator (10) filled with a working fluid heated by heat supplied from a heat source, for evaporating the working fluid so as to be converted into a high temperature and high pressure gaseous state;
• an expander (20) connected to the evaporator (10) by a pipe, for expanding the high-temperature and high-pressure working fluid flowing into the expander (20);
• a generator (30) attached to the expander (20), for generating electricity;
• a condenser (40) connected to the expander (20) by a pipe through which the expanded working fluid flows into the condenser (40), for condensing the working fluid by heat-exchange with cooling water transferred from the outside so that the working fluid is converted into a low temperature and low pressure liquid state, and for transferring the low-temperature and low-pressure working fluid to the evaporator (10) through two pipes connecting the condenser (40) and the evaporator (10);
• and
• a differential pressure transducer (50) for measuring a difference between the pressure at an outlet of the evaporator (10) and the pressure at an outlet of the expander (20).

A method of controlling a Rankine cycle system, comprising:

• a step (S100) of evaporating a working fluid inside an evaporator (10) so as to be of a high temperature and high pressure, by heating the working fluid by using heat from a heat source while closing first, second and third switch valves (80, 81 and 82);
• a step (S110) of expanding the high-temperature and high-pressure working fluid flowing into an expander (20), by opening the first switch valve (80) when a pressure difference (ΔP) between the pressure before the expander (20) and the pressure after the expander (20) reaches a preset pressure difference (ΔPa);
• a step (S120) of generating electricity, by using a generator (30) during the working fluid is expanding in the expander (20);
• a step (S130) of condensing the working fluid expanded in the expander (20) and transferred to a condenser (40) so as to be of a low temperature and low pressure in the condenser (40) by heat-exchange with cooling water provided from the outside;
• a step (S140) of transferring the low-temperature and low-pressure working fluid to the evaporator (10) by gravity, by closing the first switch valve (80) and opening the second and third switch valves (81 and 82) simultaneously when the working fluid is not present in the evaporator (10), so that the pressure of the evaporator (10) is equal to the pressure of the condenser (40);
• and
• a step (S150) of closing the second and third switch valves (81 and 82) when the working fluid of the condenser (40) is completely transferred to the evaporator (10),
• and wherein the whole processes are repeatedly performed by the operation of the evaporator (10).

A method of controlling a Rankine cycle system, comprising:

• a step (S200) of evaporating a working fluid inside an evaporator (10) so as to be of a high temperature and high pressure, by heating the working fluid by using heat from a heat source while closing first, second and third solenoid valves (90, 91 and 92);
• a step (S210) of expanding the high-temperature and high-pressure working fluid flowing into an expander (20), by opening the first solenoid valve (90) by a first controller (60) when a pressure difference (ΔP) between the pressure before the expander (20) and the pressure after the expander (20) reaches a preset pressure difference (ΔPa) of a differential pressure transducer (50);
• a step (S220) of generating electricity, by using a generator (30) during the working fluid is expanding in the expander (20);
• a step (S230) of condensing the working fluid expanded in the expander (20) and transferred to a condenser (40) so as to be of a low temperature and low pressure in the condenser (40) by heat-exchange with cooling water provided from the outside;
• a step (S240) of transferring the working fluid of the condenser (40) to the evaporator (10) by gravity, by opening the second and third solenoid valves (91 and 92) simultaneously by a second controller (70) receiving a signal from a first liquid level switch (93) when the liquid level of the working fluid in the evaporator (10) reaches the first liquid level switch (93), so that the pressure of the evaporator (10) is equal to the pressure of the condenser (40);
• and
• a step (S250) of closing the second and third solenoid valves (91 and 92) by the second controller (70) receiving a signal from a second liquid level switch (94) when the working fluid of the condenser (40) is transferred to the evaporator (10) and the liquid level in the condenser (40) reaches the second liquid level switch (94),
• and wherein the whole processes are repeatedly performed by the operation of the evaporator.