Latent heat conversion

The coal conversion efficiency to synthetic, pipeline-cjuality natural gas or licjtiid crude oil is in the 60 to 70 percent range. This means that only 60 to 70 percent of the latent heat energy in the coal can be obtained by burning the product of the conversion. However, for the lower Btu per cubic foot products of water gas and coke oven gas, conversion efficiencies can reach over 95 percent. 

The first term represents the sensible heat of cooling down from ambient to boiling point temperature, the second term represents the latent heat of the phase change, and the third term represents the energy contained in the ortho-para (o-p) conversion. 

Figure 12. In other words, the conversion gas of a PBC system is equivalent to the gas fuel of a gas-fired system. Consequently, the mass flow and stoichiometry of the conversion gas are key quantities in the calculation of the correct excess air number (see Paper I), the latent heat flow of combustion, and the conversion efficiency, and the combustion efficiency of a PBC system.

The combustion enthalpy of the conversion gas is not possible to determine unless the molecular composition of the conversion gas is known. Consequently, the latent heat flow of the conversion gas cannot be determined. 

The combustion heat rate (latent heat flux of conversion gas) (W/m )... 

From the information about the mass flux of the conversion gas it is possible to calculate the latent heat flux of combustion contained in the conversion gases from the relationship... 

Since the oceans comprise over 70% of the earth s surface area, the absorbed solar energy that is stored as latent heat of the oceans represents a very large potential source of energy. As a result of variation in the density of ocean water with temperature, the ocean water temperature is not uniform with depth. Warm surface ocean water with low density tends to stay on the surface and cold water with high density within a few degree of 4°C tends to settle to the depths of the ocean. In the tropics, ocean surface temperatures in excess of 25° C occur. The combination of the warmed surface water and cold deep water provides two different temperature thermal reservoirs needed to operate a heat engine called OTEC (ocean thermal energy conversion). Since the temperature difference of the OTEC between the heat source and the heat sink is small, the OTEC power plant cycle efficiency... 

It appears from this table that when the simp has reached 248°, although wateT continues to be given off, yet the temperature sinks to 234 5°, after which it again rises. If there be no error in tho observation, this 1b probably due to the formation of a definite hydrate of sugar, which requires a higher temperature for its decomposition j but that decomposition being once determined, the water expelled tokos up the caloric as latent heat in its conversion into steam, thus depressing the temperature of the sirup. 

The refrigerant liquid partially flashes to a vapor as it flows through the letdown valve. The flashing represents the conversion of the sensible heat of the refrigerant to latent heat of vaporization. In Fig. 22.1, the refrigerant is chilled from 100 to 40°F. Approximately 25 percent of the liquid flashes to a vapor to provide this autorefrigeration. 

Conversely, condensation from a vapor to a liquid is a heating process, as the latent heat is converted to sensible heat in the liquid, and the liquid temperature rises (as observed in a cooling tower plume). 

This is calculated at 180 °C for the charge of 2kmol and for a conversion of zero, which is conservative. It would be reasonable to interrupt the runaway at its very beginning, for example, at 190 °C. If we consider that the reaction rate doubles for a temperature increase of 10 K, the heat release rate would be 56kW at 190 °C. The latent heat of evaporation can be estimated from the given Clausius-Clapeyron expression ... 

There is a AH for the process of sublimation, called the latent heat of sublimation (heat of sublimation). Sublimation is the conversion from the solid state to the gaseous physical state, skipping the liquid state. Elemental iodine, I2, and C02 are substances that sublime at 1 atm pressure. 

Condensation Conversion of a vapor to a liquid by removing the latent heat of condensation from the vapor. 

Vaporization Conversion of a liquid to a vapor by adding the latent heat of vaporization to the liquid. Boiling is a commonly used synonym but is not as precise. 

Fig. 1.12. Maximum temperature (a) and ethylbenzene conversion (b) during one production cycle for a fixed bed of uniform heat capacity (dotted line), fora structured fixed-bed with inert end sections of higher heat capacity (dashed line), and for latent heat storage inside the catalytic section (solid line) [9].

Figure 3.26 Subtraction technique for elimination of effect of sample heat capacity change. The endotherm from the DTA trace represents both the latent heat of transformation as well as a shift in heat capacity of the sample during the transformation. The baseline (which is the sample temperature lag relative to the reference) shifts most rapidly near the center of the endotherm, where the conversion of reactant to product is most fervent. The right-hand trace represents a DTA endotherm with the effects of sample heat capacity changes subtracted out. Note that in this case, where the total heat capacity of the product is less than the reactant, this subtraction has resulted in an endotherm of larger area.

Trinitrotoluene (also known as y-TNT) is one of the main impurities in military and commercial grades of TNT. Chick and Thorpe (1971) characterized two polymorphs. Form I (mp 376.2 K) may be obtained by recrystallization from alcohol or solidification of the melt. Form II (mp 347.2 K) is produced in small quantities with difficulty from an undercooled melt. It readily converts to Form I by mechanical perturbation or even spontaneously. Chick and Thorpe also determined latent heats of fusion, entropies of fusion, specific heats, IR spectra. Due to the conversion induced by grinding no X-ray data were presented for either form. No crystal structures have been reported. 

The equation, a direct consequence, or rather an expression, of the second law (as discussed on p. 26), has been repeatedly verified. In the first place it corresponds exactly to the law governing change of melting point with pressure, where q is the latent heat of fusion, v the increase of volume on fusion. And then Eeicher verified the above formula experimentally, while Mallard and Le Chatelier did the same for the conversion of silver iodide, which at 146° passes from hexagonal to regular. Eoozeboom, finally, has verified the equation for the fusion of the hydrate HBr.2H20 at — 11 3 which is due to chemical decomposition. 

Similarly, A// for a vaporization is equal to the latent heat of vaporization carried out at constant temperature and pressure. The latent heat of vaporization of water at 100 °C and 1 atm is 540 cal/g or 9.72 kcal/mol = 40.7 kJ/mol. A// for a sublimation process is equal to the latent heat for conversion of a substance from the solid to the gaseous state. 

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