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The LMTD is a steady-state concept, and cannot be used in dynamic analyses. In particular, if the LMTD were to be applied on a transient in which, for a brief time, the temperature difference had different signs on the two sides of the exchanger, the argument to the logarithm function would be negative, which is not allowable.
The number of transfer units (NTU) method is used to calculate the rate of heat transfer in heat exchangers (especially parallel flow, counter current, and cross-flow exchangers) when there is insufficient information to calculate the log mean temperature difference (LMTD). Alternatively, this method is useful for determining the expected heat ...
By adding a correction factor, known as the activity (, the activity of the i th component) to the liquid phase fraction of a liquid mixture, some of the effects of the real solution can be accounted for. The activity of a real chemical is a function of the thermodynamic state of the system, i.e. temperature and pressure.
A fudge factor is an ad hoc quantity or element introduced into a calculation, formula or model in order to make it fit observations or expectations. Also known as a correction coefficient , which is defined by
This would introduce a second correction factor λ B into λ R, giving = (). Experimental values for the "generalized" coefficient A G are generally of the order of magnitude of A 0 , but do differ significantly as between different emitting materials, and can differ as between different crystallographic faces of the same material.
This graph is called the "Van 't Hoff plot" and is widely used to estimate the enthalpy and entropy of a chemical reaction. From this plot, − Δ r H / R is the slope, and Δ r S / R is the intercept of the linear fit.
That is, observed temperatures above 60 °F (or the base temperature used) typically correlate with a correction factor below "1", while temperatures below 60 °F correlate with a factor above "1". This concept lies in the basis for the kinetic theory of matter and thermal expansion of matter , which states as the temperature of a substance ...
where J is the emission current density, T is the temperature of the metal, W is the work function of the metal, k is the Boltzmann constant, q e is the Elementary charge, ε 0 is the vacuum permittivity, and A G is the product of a universal constant A 0 multiplied by a material-specific correction factor λ R which is typically of order 0.5.