Net energy streams

Let E be the whole set of the net energy streams constituting the 2(n)-terms as explained. Let us introduce the coefficients obeying the convention... 

The technological system extended by net energy streams and energy distributors can be represented by graphs G and Gg see Section 5.2. Here, the additional Gg is of node set... 

As an immediate consequence of the conventions, for any de Dg we can find some arc i E (net energy stream) whose other endpoint is in Ty, hence with an appropriate arrangement of the set E we have the partition... 

The partition of a heat exchanger (as technological unit) into two nodes (8.3.32) has been motivated by separate (generally multicomponent) mass balances of the cold and hot sides. On the other hand, it can happen that we are not interested in the (unknown) heat transfer rates. Then the latter can be eliminated by merging the nodes (8.3.32). Let us first partition the set E of net energy streams... 

Equation 6.33 provides the definition of exergy if state 1 is chosen as the state at ambient condition, namely, P, = P0 and = T0 the minimum amount of work required to transfer the system from environmental conditions to those at P2 and T2. At these conditions, this is the maximum amount of work available for the reverse process. That is the valuable idea behind the exergy concept to be able to assign to any process stream a value, its exergy, that expresses the confined work available in the stream. For the general change in state from P0r T0 to P, T, we can write the net energy input as... 

If air infiltration is avoided (or minimized to an acceptable level), it is possible to recover all of the latent heat supplied in the SSD from the exhaust by condensing the exhaust stream or by mechanical- or thermocompression to elevate its specific enthalpy for reuse in the dryer. As SSD will necessarily produce steam equal in amount to the water evaporated in the dryer, it is necessary to have a useful application for this excess steam in the process plant. If this steam is used elsewhere, the latent heat recovered is not charged to the SSD, leading to a net energy consumption figure of... 

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