Example 2.1. The design indoor air temperature and relative humidity of an air conditioned space at sea level are 75°F (23.9°C) and 50 percent. Find the humidity ratio, the enthalpy, and the density of the indoor moist air
1. By using the ASHRAE chart
2. By calculation
Determine also the dew-point and thermodynamic wet-bulb temperatures of the moist air. The following information is required for the calculations:
Atmospheric pressure at sea level
Specific heat of dry air Specific heat of water vapor Enthalpy of saturated vapor at 0°F Gas constant of dry air
14.697 psi (101,325 Pa)
0.240 Btu / lb °F (1.005 kJ / kg K)
0.444 Btu / lb °F (1.859 kJ / kg K)
1061 Btu / lb (2468 kJ / kg)
53.352 ft lbf /lbm °R (0.287 kJ / kg K)