Evaporation rate, mass

Liquids with high saturation vapor pressures evaporate faster. As a result, the evaporation rate (mass/time) is expected to be a function of the saturation vapor pressure. In reality, for vaporization into stagnant air, the vaporization rate is proportional to the difference be-... 

L is the heat of vaporization of the liquid (energy/mass ) th is the evaporation rate (mass/time)... 

The released ammonia forms a pool of refrigerated liquid which evaporates by heat transfer from the soil. A constant mass value was assumed for the evaporation rate and a heavier-than-air gas dispersion model was used. 

Given this evaporation rate, the overall mass transfer coefficient may then be calculated from Equation 4-391,... 

Example 6.5 A water tower serves a condenser rated at 880 kW and the water-circulating pump takes another 15 kW. What will be the evaporation rate, the approximate circulation rate, and the air mass flow ... 

At very high qualities the liquid film is thin and the rate of entrainment is low. The entrained liquid mass flux curve is almost parallel with the total liquid mass flux in Figure 5.26 i.e., the liquid evaporation rate is supported solely by the liquid deposition rate. If the boiling heat flux q" < q D, where q"D = GDH]g, the boiling crisis can be averted by a deposition liquid mass flux, GD, as shown in Figure 5.26, and therefore is called deposition-controlled CHF. 

What is the evaporation rate and yield of the sodium acetate hydrate CH3C00Na.3H20 from a continuous evaporative crystalliser operating at 1 kN/m2 when it is fed with 1 kg/s of a 50 per cent by mass aqueous solution of sodium acetate hydrate at 350 K The boiling point elevation of the solution is 10 degK and the heat of crystallisation is 150 kJ/kg. The mean heat capacity of the solution is 3.5 kJ/kg K and, at 1 kN/m2, water boils at 280 K at which temperature the latent heat of vaporisation is 2.482 MJ/kg. Over the range 270-305 K, the solubility of sodium acetate hydrate in water s at T(K) is given approximately by ... 

At the instant of time shown, the entrainment of air into the fire plume is 300 g/s, the outflow of smoke through the door is 295 g/s and the liquid fuel evaporation rate of a spill burning on the floor is 10 g/s. What is the mass rate of smoke accumulation within the room ... 

Mass evaporation rate = diffusion transport rate to the air Heat transfer rate = energy required to vaporize... 

The convective heat transfer coefficient may be approximated as that due to heat transfer without the presence of mass transfer. This assumption is acceptable when the evaporation rate is small, such as drying in normal air, and for conditions of piloted ignition, since XL is typically small. Mass transfer due to diffusion is still present and can be approximated by... 

APV Paravap and Paraflash evaporators are used for products with viscosities up to 5 Ns/m2 and concentrations in excess of 99 per cent by mass. Evaporation rates are up to 4 kg/s. 

In order to obtain the solution desired, a value of Ts is assumed, the vapor pressure of A is determined from tables, and mAs is calculated from Eq. (6.98). This value of mAs and the assumed value of Ts are inserted in Eq. (6.97). If this equation is satisfied, the correct Ts is chosen. If not, one must reiterate. When the correct value of Ts and mAs are found, BT or BM are determined for the given initial conditions Tx or mAco. For fuel combustion problems, mAcc is usually zero however, for evaporation, say of water, there is humidity in the atmosphere and this humidity must be represented as mAco. Once BT and BM are determined, the mass evaporation rate is determined from Eq. (6.87) for a fixed droplet size. It is, of course, much preferable to know the evaporation coefficient (5 from which the total evaporation time can be determined. Once B is known, the evaporation coefficient can be determined readily, as will be shown later. 

Latent heat associated with phase change in two-phase transport has a large impact on the temperature distribution and hence must be included in a nonisothermal model in the two-phase regime. The temperature nonuniformity will in turn affect the saturation pressure, condensation/evaporation rate, and hence the liquid water distribution. Under the local interfacial equilibrium between the two phases, which is an excellent approximation in a PEFG, the mass rate of phase change, ihfg, is readily calculated from the liquid continuity equation, namely... 

As indicated by Fig. 23 and Fig. 24, the source function can be highly asymmetrical. For the liquid droplet corresponding to Fig. 23, one would expect the internal temperature to be higher near the back and front of the sphere because of the spikes in the source function in those regions. As a result, the evaporation rate should be enhanced at the rear stagnation point and the front of the sphere. To calculate the evaporation rate when internal heating occurs, one must solve the full problem of conduction within the sphere coupled with convective heat and mass transport in the surrounding gas. 

Once the surface temperature distribution has been computed, using Eq. (151), the droplet evaporation rate is given by integrating the local mass flux over the droplet surface,... 

The rate of combiastion is controlled either by the evaporation rate of the fuel into the reacting boundary layer or the mass transfer of the O2 from the surrounding air. Note the signs of A Hr and the heat of vaporization AH, . Since vaporization is always endothermic, it will tend to cool the drop and thus slow reaction. 

The current conditions regarding residence time and evaporation rate apply to the past. With no reaction utilizing sodium in the lake, the mass transport equation for the complete mixed reactor is... 

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