Condensers calculation

Ganapathy, V, Chart Eases Steam-Condenser Calculations, Oil and Gas Joumal,]2Ji. 7 (1980) p. 90. 

Suppose that methane and air in stoichiometric proportions are brought into a calorimeter at 500 K. The product composition is brought to the ambient temperature (298 K) by the cooling water. The pressure in the calorimeter is assumed to remain at 1 atm, but the water formed has condensed. Calculate the heat of reaction. 

Condensation theory is based on thermodynamic equilibrium. More than a century s worth of experiments have yielded thermodynamic data (entropy and enthalpy of formation, plus heat capacity) for elements and compounds. Equations of state describing the stabilities of different compounds under various conditions can be calculated from these data, as briefly described in Box 7.1. Because liquids are not normally stable at the low pressures appropriate for space, the compounds in condensation calculations are generally solid minerals, but liquids can exist at higher pressures (achievable if areas of the nebula with enhanced dust concentrations relative to gas were vaporized). 

The temperatures of appearance of various solid phases as a cooling solar gas condenses are illustrated in Figure 7.1. This particular condensation calculation was performed at a pressure of 10 4 atm (thought to be appropriate for parts of the nebula). It is important to note that not every mineral in the sequence actually condenses directly from the vapor. Instead, some minerals form by reaction of previously condensed solids with the vapor. For example, FeS forms by reaction of already condensed Fe metal with sulfur in the gas phase, and olivine first condenses as the magnesium end member forsterite and then becomes progressively more iron-rich by reaction with vapor as temperature decreases. 

To illustrate how a (simple) condensation calculation works, let s consider the condensation of corundum (Al203), one of the earliest phases predicted to condense from a solar gas. The partial pressures of aluminum (PAi) and oxygen (P0) in the gas phase must first be determined, based on their solar abundances, over a range of temperatures. The eguilibrium between solid (s) corundum and gas (g) can be represented by this equation ... 

In condensation calculations, internally consistent thermodynamic datasets are preferred (but not always used) over data haphazardly collected from disparate sources. Another... 

Applicability of condensation calculations to the early solar system... 

Ebel, D. S. (2006) Condensation of rocky material in astrophysical environments. In Meteorites and the Early Solar System, II, eds. Lauretta, D. S. and McSween, H. Y., Jr. Tucson University of Arizona Press, Tucson, pp. 253-277. A good summary of the modem condensation calculations and modeling of solar system processes. 

Stagnant saturated steam at 100°C condenses on the outside of a horizontal copper tube with outside diameter 5.0 cm. The copper tube has a wall thickness of 1.5 mm and a thermal conductivity of 390 W/m-K. At the axial location being considered, the bulk temperature of the vater flowing inside the copper tube is 80°C and the inside heat transfer coefficient is 3500 W/m2. Assuming film condensation, calculate the heat transfer and condensation rate per unit length of pipe. 

Steam at 1 atm pressure (7 sal = 100°C) is exposed to a 30-by-30-cm vertical square plate which is cooled such that 3.78 kg/h is condensed. Calculate the plate temperature. Consult steam tables for any necessary properties. 

The CNDS subroutine would proceed in a similar manner tor the condenser calculations—first solving material and energy balances to determine unknown flow rates and the heat dut>. and then possibly performing design calculations. 

Condensation calculations in which the thermodynamic equilibrium condensate mineral assemblage is calculated as a function of temperature in a gas of fixed pressure and composition (usually solar) provide an extremely useful framework for interpreting bulk compositions of CAIs, chondrules, meteorites, and planets. Calculations of this sort date back to Urey (1952). Lord (1965) and Larimer (1967) calculated gas-solid equilibria for solar system composition, but did not correct the gas for removal of condensed material. The first detailed high-temperature condensation sequence was defined by Grossman (1972). The results of a calculation of Yoneda and... 

It must be recognized that the availabihty of thermodynamic data requires some compromises in condensation calculations. Eor condensation calculations at pressures where no melt condensation needs to be considered, the best thermodynamic data for mineral phases can be used, although there is still no model for sohd solution... 

Condensation calculations can be carried out to relatively low temperatures Grossman and Larimer (1974) extended calculations to below 400 K, and Lodders (2003) lists 50% condensation temperatures as low as 9 K , but the meaning of calculations below —1,000 K is unclear as gas-solid equilibrium is unlikely to be reached. 

Yamamoto et al. [2] made a condensation calculation to estimate tlie chemical composition of the ice in molecular clouds and cometaiy nuclei. They assumed tlie interstellar molecular composition for tlie abundance of gas. Inter-... 

Maintaining the temperature at 65.6°C enhances mass transfer from the vapor to the liquid by removing the net heat of condensation, calculated as... 

Keywords cosmochemistry, condensation calculations, elements, solar nebula... 

Cosmochemistry is the chemistry of the cosmos. This is a broad topic that ranges from the nucleosynthesis of elements in stars to their chemistry on the Earth today. In this chapter, we describe chemical equilibrium (or condensation) calculations of the cosmochemical behavior of the elements. 

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