enthalpy of vaporization

(redirected from Vaporization heat)

enthalpy of vaporization

[en′thal·pē əv ‚vā·pə·rə′zā·shən]
(thermodynamics)
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When its value is close to 1, there is virtually no difference between multilayer molecules and liquid molecules, i.e., the vaporization heat is close to the water vaporization heat.
Through many analytical studies on the LOE various prediction methods have been proposed with respect to aspects such as the oil-film thickness formed by piston rings on the cylinder wall, the pressure and temperature of the gas in the combustion chamber, the heat transfer from gas to wall, the cylinder wall temperature, the vapor pressure, vaporization heat and vapor diffusion rate of mono-species or multi-species component oils and so on but the predicted values of LOE, the estimated oil evaporation rates, are different from each other as shown in Table 1.
Further, they have proposed the analytical method to predict the LOE of multi-species component mineral oils by using the saturated vapor pressure and the vaporization heat of oil species, and investigated the LOC mechanism comparing the LOE with the LOC measured under the whole operating conditions with a practical diesel engine.
The heat flux due to the oil evaporation [q.sub.2] is given by summing the product [q.sub.2i] of the evaporation mass flux [m.sub.j] and the vaporization heat L[v.sub.i] for each oil species i as below.
Heat transfer process is cauterized into five steps: (i) heat transfer from the hot solution bulk through the boundary layer to the hot side of the membrane surface; (2) part of the heat on the hot side of the membrane provides the vaporization heat for vaporization; (3) heat transfers from the hot side of the membrane surface through pores to the vacuum side; (4) volatile compounds on the vacuum side condenses and releases the vaporization heat; (5) heat transfers from the vacuum side of the membrane surface to the condensing system [9, 10].
Due to the surface vaporization, the liquid loses its latent Vaporization heat so that the temperature decreases.
If the values of parameters b and [T.sub.f] are known, [V.sub.u] which is defined as a burning velocity calculated by neglecting vaporization heat of fuel particles can be evaluated.
By convention, ASHRAE chooses the heat content of moist air as zero at the starting point [T.sub.0] of the temperature scale, (1) while calculating the vaporization heat [h.sub.0.sup.vap] at [T.sub.0] (ASHRAE 2005).
Specifically, if we naively assume that we can set the enthalpy scale such that the enthalpy of moist air at the freezing point of water is its vaporization heat only, we make the invalid assumption that the heat content of air and water vapor are the same at a temperature other than absolute zero; this, of course, is wrong, as (assuming both are ideal gases) the heat content of a quantity of air at 0[degrees]C (32[degrees]F) matches the heat content of a similar quantity of water vapor at -125.41[degrees]C(-193.74[degrees]F).
Refrigerant R134a vaporization heat transfer and pressure drop inside a small brazed plate heat exchanger.
Drying times for water-based systems are still longer at present than solvent-based ones, because the vaporization heat needed for water roughly three times as high as for conventional VOC's.
[h.sub.v] = latent vaporization heat of physical blowing agents per unit polymer mass [cal/g]