The sensible heat duty for natural gas at constant pressure is:
Heat capacity is determined at atmospheric conditions and then corrected for temperature and pressure based on reduced pressure and temperature.
The gas pseudo critical pressures and temperatures can be approximated from Figure 2-16 or they can be calculated as weighted averages of the critical temperatures and pressures of the various components on a mole fraction basis. Table 2-10 shows a calculation for the gas stream in our example field.
For greater precision, a correction for H2S and CO2 content may be required. Refer to the Gas Processors Suppliers Association’s Engineering Data Book or other text for a correction procedure.