![]() ![]() Air - Thermophysical Properties - Thermal properties of air at different temperatures - density, viscosity, critical temperature and pressure, triple point, enthalpi and entropi, thermal conductivity and diffusivity and more.Temperature at Constant Pressure - Online calculator with figures and tables showing specific heat (Cp and Cv) of dry air vs. Air - Maximum Moisture Carrying Capacity - Maximum water content in humid air vs.Air - Humidity Ratio - The mass of water vapor present in moist air - to the mass of dry air.Air - Humidity Measurement from Dry and Wet Bulb Temperature - Relative humidity in moist air can estimated by measuring the dry and wet bulb temperature.Air - Humidifying with Steam, SI units - Using steam to humidify air.Air - Humidifying by Adding Steam or Water - Air can be humidified by adding water or steam.Air Psychrometrics - Moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content.H = c pa t + x s + (x - x s) c i t - (x - x s) h im (8)Ĭ i = 2.05 - specific heat ice (kJ/kg oC) If the air contains water as ice or snow, the enthalpy of air can be expressed as: X s = humidity ratio at saturation (kg/kg)Ĭ w = 4.19 - specific heat water (kJ/kg oC) Enthalpy of Moist Air containing Ice or Snow The enthalpy of moist air with fog can be expressed as: If the air contains more water than limited by saturation, some of the water exists as droplets - as fog. Enthalpy of Moist Air containing Water as Fog The sensible heat due to heating evaporated water vapor can be almost neglected. Note! - the latent heat due to evaporation of water is the major part of the enthalpy. The enthalpy of humid air at 25 oC with specific moisture content x = 0.0203 kg/kg (saturation), can be calculated as: You can not convert from metric to imperial enthalpy or vice versa directly. The evaporation heat for water at 0 oF is 1061 Btu/lb as used in eq. (6) imperial units - the "reference" point for enthalpy h = 0 (Btu/lb) is t = 0 oF (-17.8 oC) and x = 0 lb/lb. (5) metric units - the "reference" point for enthalpy h = 0 (kJ/kg) is t = 0 oC (32 oF) and x = 0 kg/kg Note! - the "reference" points for the metric and imperial enthalpies are different. Using (2) and (3), (1) can be modified to The evaporation heat ( water at 0 oC, 32 oF) can be set to H we = evaporation heat of water at 0 oC (kJ/kg)įor water vapor the specific heat can be set to Specific Enthalpy of Water Vapor - the Latent HeatĪssuming constant pressure conditions the specific enthalpy of water vapor can be expressed as:Ĭ pw = specific heat of water vapor at constant pressure (kJ/kg oC, kWs/kgK) This is not correct according the definition of enthalpy in the thermodynamics, but for practical purposes in air psychrometrics this assumption is good enough since our interest is the enthalpy difference. Note! - that the enthalpy is 0 kJ/kg at 0 oC. H w = specific enthalpy of water vapor (kJ/kg, Btu/lb ) Specific Enthalpy of Dry Air - the Sensible HeatĪssuming constant pressure conditions the specific enthalpy of dry air can be expressed as:Ĭ pa = specific heat of air at constant pressure (kJ/kg oC, kWs/kgK, Btu/lb oF)įor air temperature between -100 oC (-150 oF) and 100 oC (212 oF) the specific heat can be set to H a = specific enthalpy of dry air (kJ/kg, Btu/lb ) H = specific enthalpy of moist air (kJ/kg, Btu/lb ) Specific enthalpy of moist air can be expressed as: Specific enthalpy - h - (J/kg, Btu/lb) of moist air is defined as the total enthalpy ( J, Btu) of the dry air and the water vapor mixture - per unit mass ( kg, lb) of dry air. ![]() The total enthalpy - sensible and latent - is used when calculating cooling and heating processes. enthalpy of the evaporated water in the air - the latent heat.enthalpy of the dry air - the sensible heat.The enthalpy of moist and humid air includes the In atmospheric air water vapor content varies from 0 - 3% by mass. When display comes on, release both keys.Moist air is a mixture of dry air and water vapor. Press and hold Hold key and On/Off key at same time. inactivity (To deactivate, turn device off. (90% at ambient temperature of 25☌ / 77☏)Īutomatic power off after 15 min. ![]()
0 Comments
Leave a Reply. |