= (10 m 3) (9.81 m/s 2)į l = lifting force - change in gravity force (weight) (N)Ī g = acceleration of gravity (9.81 m/s 2)ĭm = V d ρ = change of mass in the balloon (kg)ĭρ = change in density due to temperature difference (kg/m 3) The change in gravity force (weight) of the air volume is the potential lifting force of the balloon. The temperature of the surrounding air is 20 oC. The mass of 10 m 3 air can be calculated asĮxample - Lifting Force of a Hot Air BalloonĪn air balloon with volume 10 m 3 is heated to 100 oC. The mass of 10 m 3 air can be calculated asĮxample - Mass of Air at Temperature 20 oCįrom the table above - the density of air is 1.205 kg/m 3 at 20 oC. Temperature ChartĮxample - Mass of Air at Temperature 100 oCįrom the table above - the density of air is 0.946 kg/m 3 at 100 oC. The triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.ĭownload and print Air - Density vs. The curve between the triple point and the critical point shows the air boiling point with changes in pressure.Īt the critical point there is no change of state when pressure is increased or if heat is added. The phase diagram for air shows the phase behavior with changes in temperature and pressure. However, at low temperature and high pressures the gas mixture becomes a liquid. See also more about atmospheric pressure, and STP - Standard Temperature and Pressure & NTP - Normal Temperature and Pressure,Īs well as Thermophysical properties of: Acetone, Acetylene, Ammonia, Argon, Benzene, Butane, Carbon dioxide, Carbon monoxide, Ethane, Ethanol, Ethylene, Helium, Hydrogen, Hydrogen sulfide, Methane, Methanol, Nitrogen, Oxygen, Pentane, Propane, Toluene, Water and Heavy water, D 2O.Īir is a mixture of gases at standard conditions. Specific heat (heat capacity) at varying temperature.Specific heat (heat capacity) at varying pressure.Properties at gas-liquid equilibrium condition.Diffusion coefficients of gases in excess of air.Density, specific weight and thermal expansion coefficient at varying temperature.Viscosity, kinematic, at 0☌ and 1 bara: 0.00001349 m 2/s = 13.49 cSt = 0.0001452 ft 2/sįollow the links below to get values for the listed properties of air at varying pressure and temperature:.Specific heat capacity (C v) air at 0☌ and 1 bara: 0.7171 kJ/kgK = 0.17128 Btu(IT)/(lb m ☏) or kcal/(kg K).Specific heat capacity (C p) air at 0☌ and 1 bara: 1.006 kJ/kgK = 0.24028 Btu(IT)/(lb m ☏) or kcal/(kg K).Liquid density at boiling point and 1 bar: 875.50 kg/m 3 = 54.656 lb/ft 3.Bulk modulus elasticity: 1.01325 x 10 5 Pa or N/m 2.Of course, the force generated from the pressure on an object has both a magnitude and direction. Note that pressure is a scalar quantity it has a magnitude but no direction. Instead, $\lb/\inch^2$, abbreviated psi, is the standard. The standard unit of pressure in the US system is $\lb/\ft^2$ but is rarely used. The standard unit of pressure in the SI system is $\N/\m^2$ and has its own name, the pascal (Pa). \įor this definition to work the area must be small enough so that the force is uniformly distributed over that area. The density of a fluid is its mass per unit volume, Density, specific weight & specific gravity Density The sections below go through a number of physical properties that are commonly used to characterize fluids. Both liquids and gases fit this description and the word fluid refers to either. Density, specific weight & specific gravityĪ fluid is a substance that continually deforms or flows under an applied shear stress.
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