Specific heat, mean

Thermal Properties. Because all limestone is converted to an oxide before fusion or melting occurs, the only melting point appHcable is that of quicklime. These values are 2570°C for CaO and 2800°C for MgO. Boiling point values for CaO are 2850°C and for MgO 3600°C. The mean specific heats for limestones and limes gradually ascend as temperatures increase from 0 to 1000°C. The ranges are as follows high calcium limestone, 0.19—0.26 dolomitic quicklime, 0.19—0.294 dolomitic limestone, 0.206—0.264 magnesium oxide, 0.199—0.303 and calcium oxide, 0.175—0.286. 

Table 8. Mean Specific Heats of Refractory Brick and Minerals, Between 0°C and the Indicated Temperature, J/(kg-K) ...

Cij = mean specific heat of combustion products from base temperature to leaving-gas temperature Te-C = cold-surface fraction of a furnace enclosure. 

An equation representing an energy balance on a combustion chamber of two surface zones, a heat sink Ai at temperature T, and a refractory surface A assumed radiatively adiabatic at Tr, inmost simply solved if the total enthalpy input H is expressed as rhCJYTv rh is the mass rate of fuel plus air and Tp is a pseudoadiabatic flame temperature based on a mean specific heat from base temperature up to the gas exit temperature Te rather than up to Tp/The heat transfer rate out of the gas is then H— — T ) or rhCp(T f — Te). The... 

The mean specific heat of coal ash and slag, which is used for calculating heat balances on furnaces, gasifiers, and other coal-consuming systems, follows. 

Mean specific heat of steam of air at constant pressure Cp, = 4210 J kgp K ... 

Essentially, the analytical approach outlined above for the open circuit gas turbine plants is that used in modem computer codes. However, gas properties, taken from tables such as those of Keenan and Kaye [6], may be stored as data and then used directly in a cycle calculation. Enthalpy changes are then determined directly, rather than by mean specific heats over temperature ranges (and the estimation of n and n ), as outlined above. 

C = total weight of contents when full (kg (lbs)), h = mean specific heat of fuel oil,... 

The following values should be used for the mean specific heat ... 

Class offuel Mean specific heat 0-100°C kJlkg°C)... 

Corollaries.—(1) To find the true specific heat when the mean specific heat is given, multiply the latter by 6 and differentiate with respect to 6. 

The method just described leads to the mean specific heats over a fairly large range. Nernst, Koref, and Lindemann (1910) have recently described a method of measuring the true specific heat at a given low temperature. The substance is contained in a block of copper cooled to the requisite temperature in liquid carbon dioxide, liquid air, etc., and energy is supplied by a heating spiral of platinum wire carrying an electric current, the measurement of the resistance of which serves at the same time to determine the temperature. 

The mean specific heat of saturated steam at a temperature slightly higher than 100° was found by Regnault to be 0 48. 

The calculation may be extended to specific heats which are quadratic functions of temperature, etc., and we may also replace the integral of the true specific heat by a mean specific heat multiplied by the difference of temperatures ( 6) ... 

Page 14, line 2 The method of Nernst, Koref, and Lindemann, by the use of the copper-calorimeter, determines the mean specific heat over a range of temperature. The mode of procedure is the same as in ordinary calorimetry, except that a hollow block of copper, the temperature of which is determined by means of inserted thermoelements, is used instead of a calorimetric liquid, and the method therefore made applicable to very low temperatures. 

Mean specific heat values are tabulated in various handbooks. If the values are for unit mass, calculated from some standard reference temperature, tr, then the change in enthalpy between temperatures i and t2 is given by ... 

R is equal to the shell-side fluid flow-rate times the fluid mean specific heat divided by the tube-side fluid flow-rate times the tube-side fluid specific heat. 

C mean specific heat including heat of melting over the range 80-Te, BTU/lb F r = throughput, lb/hr... 

The horsepower is the greatest for regular polystyrene because it has the greatest melt temperature. Using the mean specific heat for polystyrene ... 

A flow of 0.35 kg/s of a solid is to be dried from 15 per cent to 0.5 per cent moisture on a dry basis. The mean specific heat capacity of the solids is 2.2 kJ/kgdegK. It is proposed that a co-current adiabatic dryer should be used with the solids entering at 300 K and, because of the heat sensitive nature of the solids, leaving at 325 K. Hot air is available at 400 K with a humidity of 0.01 kg/kg dry air and the maximum allowable mass velocity of the air is 0.95 kg/m2s. What diameter and length should be specified for the proposed dryer ... 

In equations 17.103 and 17.104, cps and cpg are the mean specific heats over the ranges of temperature and concentrations encountered. Properties with subscripts 1 and 3 are known from inlet and exit conditions respectively. If the plateau values represented by subscript 2 are in equilibrium, then the values C2, Cv2 and 73 may be found from the equations for any known form of the adsorption isotherm CS2 = f(C2). 

If a temperature is desired at an equivalence ratio other than that listed, it is best obtained from a plot of T versus for the given values. The errors in extrapolating in this manner or from the graph are trivial, less than 1%. The reason for separate Figs 1.4 and 1.5 is that the values for = 1.0 and 4> = 1.1 overlap to a great extent. For Fig. 1.5, = 1.1 was chosen because the flame temperature for many fuels peaks not at the stoichiometric value, but between = 1.0 and 1.1 owing to lower mean specific heats of the richer products. The maximum temperature for acetylene-air peaks, for example, at a value of = 1.3 (see Table 1.2). 

The flame temperature values reported in Fig. 1.3 show some interesting trends. The H/C ratio has a greater effect in rich systems. One can attribute this trend to the fact that there is less nitrogen in the rich cases as well as to a greater effect of the mean specific heat of the combustion products. For richer systems the mean specific heat of the product composition is lower owing to the preponderance of the diatomic molecules CO and H2 in comparison to the triatomic molecules C02 and H20. The diatomic molecules have lower... 

C02 increases and the differences diminish. At the highest reaction enthalpies, the temperature for many fuels peaks not at the stoichiometric value, but, as stated, between

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