Flow measurement device, flow measurement method, and flow measurement program

A method for measuring a flow rate of a measurement target fluid, the method being implemented by

• a flow measurement device including
• a thermal flow sensor configured to sense the flow rate of the measurement target fluid flowing through a main channel, the thermal flow sensor including a heater configured to heat the measurement target fluid and a temperature sensor configured to sense a temperature of the measurement target fluid, the heater and the temperature sensor being arranged parallel to each other in a flow direction of the measurement target fluid;
• a characteristic-value obtaining unit configured to obtain a characteristic value of the measurement target fluid, the characteristic-value obtaining unit including a second heater configured to heat the measurement target fluid and a second temperature sensor configured to sense a temperature of the measurement target fluid, the second heater and the second temperature sensor being arranged parallel to each other in a direction orthogonal to a flow of the measurement target fluid, wherein the characteristic value is a ratio of an output value of the second temperature sensor obtained by flowing a predetermined gas to an output value of the second temperature sensor obtained by flowing a reference gas, and the characteristic value indicating a thermal diffusivity of the measurement target fluid, and
• a sub-channel section branching from the main channel and having one end continuous with a first inlet opening in the main channel and another end continuous with a first outlet opening in the main channel, the sub-channel section including a characteristic-value sensing channel containing the temperature sensor included in the characteristic-value obtaining unit and a flow sensing channel containing the thermal flow sensor, wherein the flow sensing channel and the characteristic-value sensing channel are defined by the sub-channel section separated by a circuit board located in parallel with the flow direction of the measurement target fluid in the sub-channel section, and the thermal flow sensor is located on a first surface of the circuit board and the temperature sensor included in the characteristic-value obtaining unit is located on a second surface of the circuit board opposite to the first surface
• the method comprising:
• sensing, performed by the thermal flow sensor, the flow rate of the measurement target fluid flowing through the main channel;
• measuring, performed by the second temperature sensor, a first temperature of the measurement target fluid;
• changing a temperature of the second heater;
• measuring, performed by the second temperature sensor, a second temperature of the measurement target fluid after changing the temperature;
• obtaining the characteristic value based on a difference between the measured first temperature of the measurement target fluid and the measured second temperature of the measurement target fluid;
• and
• correcting the flow rate of the measurement target fluid by multiplying the characteristic value by the flow rate of the measurement target fluid sensed in sensing the flow rate.

A non-transitory computer-readable storage medium storing a program causing a flow measurement device to measure a flow rate of a measurement target fluid, the flow measurement device including:

• a thermal flow sensor configured to sense the flow rate of the measurement target fluid flowing through a main channel, the thermal flow sensor including a heater configured to heat the measurement target fluid and a temperature sensor configured to sense a temperature of the measurement target fluid, the heater and the temperature sensor being arranged parallel to each other in a flow direction of the measurement target fluid;
• a characteristic-value obtaining unit configured to obtain a characteristic value of the measurement target fluid, the characteristic-value obtaining unit including a second heater configured to heat the measurement target fluid and a second temperature sensor configured to sense a temperature of the measurement target fluid, the second heater and the second temperature sensor being arranged parallel to each other in a direction orthogonal to a flow of the measurement target fluid, wherein the characteristic value is a ratio of an output value of the second temperature sensor obtained by flowing a predetermined gas to an output value of the second temperature sensor obtained by flowing a reference gas, and the characteristic value indicating a thermal diffusivity of the measurement target fluid, and
• a sub-channel section branching from the main channel and having one end continuous with a first inlet opening in the main channel and another end continuous with a first outlet opening in the main channel, the sub-channel section including a characteristic-value sensing channel containing the temperature sensor included in the characteristic-value obtaining unit and a flow sensing channel containing the thermal flow sensor, wherein the flow sensing channel and the characteristic-value sensing channel are defined by the sub-channel section separated by a circuit board located in parallel with the flow direction of the measurement target fluid in the sub-channel section, and the thermal flow sensor is located on a first surface of the circuit board and the temperature sensor included in the characteristic-value obtaining unit is located on a second surface of the circuit board opposite to the first surface
• the program causing an information processing device to perform operations comprising:
• sensing, performed by the thermal flow sensor, the flow rate of the measurement target fluid flowing through the main channel;
• measuring, performed by the second temperature sensor, a first temperature of the measurement target fluid;
• changing a temperature of the second heater;
• measuring, performed by the second temperature sensor, a second temperature of the measurement target fluid after changing the temperature;
• obtaining the characteristic value based on a difference between the measured first temperature of the measurement target fluid and the measured second temperature of the measurement target fluid;
• and
• correcting the flow rate of the measurement target fluid by multiplying the characteristic value by the flow rate of the measurement target fluid sensed in sensing the flow rate.