![]() The enthalpy of the inlet air is obtained from Fig. Relative humidity = 15 percent Wet-bulb temperature = 51.5☏ Dew point = 25.2☏ To convert British thermal units per pound dry air-degree Fahrenheit to joules per kilogram-kelvin, multiply by 4186.8 and to convert cubic feet per pound to cubic meters per kilogram, multiply by 0.0624. 12-2 Psychrometric chart-medium temperatures. To convert British thermal units per pound to joules per kilogram, multiply by 2326 to convert British thermal units per pound dry air-degree Fahrenheit to joules per kilogram-kelvin, multiply by 4186.8 and to convert cubic feet per pound to cubic meters per kilogram, multiply by 0.0624. 12-1 Psychrometric chart-low temperatures. Volume in Cubic Feet Per Pound of Dry AirįIG. ![]() Reading directly from the psychrometric chart (Fig. Determine the quantity of heat added per pound of dry air. Find the relative humidity, wet-bulb temperature, and dew point of the heated air. = 0.011 lb waterflb dry air Enthalpy at saturation h' = 31.6 Btuflb dry air Enthalpy deviation D = -0.1 Btuflb dry air True enthalpy h = 31.5 Btuflb dry air Specific volume v = 13.8 ft3flb dry air Relative humidity = 51 percent Dew point td = 60.3☏Įxample 3: Air Heating Air is heated by a steam coil from 30☏ dry-bulb temperature and 80 percent relative humidity to 75☏ dry-bulb temperature. 12-6 shows the solution dia-grammatically). Subscripts 1, 2, 3, etc., indicate entering and subsequent states.Įxample 2: Determination of Moist Air Properties Find the properties of moist air when the dry-bulb temperature is 80☏ and the wet-bulb temperature is 67☏. T = dry-bulb temperatures, ☏ tw = wet-bulb temperature, ☏ td = dew-point temperature, ☏ H = moisture content, lb waterflb dry airĪH = moisture added to or rejected from the air stream, lb waterflb dry air h' = enthalpy at saturation, Btuflb dry air D = enthalpy deviation, Btuflb dry air h = h' + D = true enthalpy, Btuflb dry air hw = enthalpy of water added to or rejected from the system,ītuflb dry air qa = heat added to the system, Btuflb dry air qr = heat removed from system, Btuflb dry air The thermodynamic properties of moist air are given in Table 12-1.Įxamples Illustrating Use of Psychrometric Charts In these examples the following nomenclature is used: Figure 12-5 shows a psychrometric chart for combustion products in air. The corrections required at pressures different from atmospheric are given in Table 12-2. These charts are for an absolute pressure of 1 atm. ![]() Figure 12-4 shows a modified Grosvenor chart, which is more familiar to the chemical engineer. 12-1 to 12-3 for low-, medium-, and high-temperature ranges. Three charts for the air-water vapor system are given as Figs.
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