Enthalpy sensible

TABLE 2-222 Ideal Gas Sensible Enthalpies/ hr - (kJ/kgmol)/ of Combustion Products... 

In towers with inert packing, both radial and axial gradients occur, although conduction in the axial direction often is neglected in view of the preponderant transfer of sensible enthalpy in a flow system. 

Use equation 3.11a to calculate the enthalpy of each component. Tabulate the results. Sum the columns to find the total stream sensible enthalpy. 

Rate of heat release measurements have been attempted since the late 1950 s. A prominent example of instrument design for the direct measurement of the sensible enthalpy of combustion products is the Ohio State University (OSU) calorimeter. This has been standardized by ASTM and a test method employing this technique (ASTM-E-906) is part of a FAA specification for evaluation of large interior surface materials. 

The last term Sh is the volumetric heat source, which may include user-defined energy source terms. The sensible enthalpy, h, is defined as... 

FIGURE 1.3 Flame temperatures (in kelvins) of hydrocarbons and air as a function of the total enthalpy content of reactions (in kilocalories per gram) for various equivalence and H/C ratios at 1 atm pressure. Reference sensible enthalpy related to 298 K. The Fl/C ratios are in the following order ... 

The enthalpy is given by the sum of the sensible enthalpy and chemical enthalpy ... 

The h-S diagram becomes most convenient in following rocket motor processes and this is the reason for its introduction. The conveniences obtained are generally hidden by machine computation programs which essentially deal with the enthalpy-entropy process for the expansion process, h is the sensible enthalpy only. Theoretical performance calculations are performed in terms of the total enthalpy which is here defined as the sum of the sensible and chemical enthalpies only. 

It is most convenient to carry out the determination of the performance parameters in terms of the total enthalpy of the reacting mixture and the total entropy S both quantities are computed for a definite amount of mixture. The total enthalpy is the sum of the sensible enthalpy and the chemical enthalpy. Since energy must be conserved and there is no kinetic energy change in the combustion chamber part of the motor, the total enthalpy of the incoming propellants must be equal to the total enthalpy of the product gas at the product temperature. 

The sensible enthalpy changes of the vapor and liquid are negligible compared to the latent heats. 

The energy conservation equation can be written using the sensible enthalpy as dependent variable ... 

When calculating energy balance around a boiler it is important also to consider fuel and air inlet temperatures. In general fuel temperature can be neglected in boiler efficiency analysis, at least it is inside standard conditions. This temperature is more important for the performances of the fuel line and atomization process. The situation is different for inlet air its temperature can have an important impact on boiler efficiency due to the flow mass involved (compare Figure 34.4). In case the inlet air is preheated by exhaust smoke, the boiler efficiency expression doesn t change with respect to Equation 34.1. In case the air is preheated by an external source, sensible enthalpy of air has to be considered in both the denominator and the numerator. 

Sensible enthalpy changes and heat of mixing are negligible compared to latent heats of vaporization. 

The mechanical energy is exchanged as shaft work. Note that the volumetric work is incorporated directly in the computation of enthalpy. If only change in temperature is involved, and no phase change occurs, the variation of the (sensible) enthalpy is ... 

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