Thermal Capacitive Flow Sensor

Calorimetric-type gas flow sensors analyze the temperature distribution built up in the environment around a central heater element [2]. Further explanation of its functionality is discussed in the next section. Using thermal electric circuits, thermal behavior of the sensor s stmcture is determined. A number of resistors and capacitors are used in the circuit to function as heat transfer agents. Flquation 11 is modeled for convective resistance and Eq. 12 for thermal capacitance where A is the heater area. The flow velocity can be obtained from Eq. 12. 

In these equations, Q is the heat flow rate with the subscript s or r denoting the sample or reference pod, respectively R is the thermal resistance, C is the heat capacity of the sensor pod (the thermal capacitance), Ts is the sample temperature, T is the reference temperature, To is the temperature of the center sensor (which is called the Tzero thermocouple), diad dTIdt is the heating rate. 

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