Question

A gas mixture at 685.0°C and 135 kPa absolute enters a heat exchanger at a rate of 73.0 m/hr. The gas leaves the heat exchanger at 215.0°C. The change in enthalpy of the gas during the cooling process is -5.60 kJ/mol. What is the heat required in kW? Assume the gas behaves ideally and that the changes in kinetic and potential energy are negligible. Number In kW

Answer 1

We have the ideal gas equation,

PV = nRT

Where, P is the pressure of the gas, V is the volume, n is the number of moles, R is the gas constant and T is the temperature in Kelvin

By substituting the values, the number of moles can be calculated as,

n = PV/RT = [(135 x 10³ Pa)(73 /3600 m³/s)]/ (8.314 m³Pa/Kmol)( 958 K) = 0.343 mol/s

Here, the change in enthalpy = -5.60 kJ/mol

We have,

Heat = q = H x n = -5.60 kJ/mol x 0.343 mol/s = -1.92 kW

Heat required = -1.92 kW