A Thomas flow meter is a device in which heat is transferred at a measured rate from an electric coil to a flowing fluid, and the flow rate of the stream is calculated from the measured temperature increase of the fluid. Suppose a device of this sort is inserted in a stream of nitrogen, the current through the heating coil is adjusted until the wattmeter reads 1.25 kW, and the stream temperature goes from 30°C and 110 kPa before the heater to 34°C and 110 kPa after the heater.
(a) If the specific enthalpy of nitrogen is given by the formula H (kJ/kg) = 1.04 [T (°C) - 25] what is the volumetric flow rate of the gas (L/s) upstream of the heater (i.e., at 30°C and 110 kPa)?
(b) List several assumptions made in the calculation of part (a) that could lead to errors in the calculated flow rate.