Heat balances exchanger networks

The analysis of the heat exchanger network first identifies sources of heat (termed hot streams) and sinks (termed cold streams) from the material and energy balance. Consider first a very simple problem with just one hot stream (heat source) and one cold stream (heat sink). The initial temperature (termed supply temperature), final temperature (termed target temperature), and enthalpy change of both streams are given in Table 6.1. 

The energy cost of the process can be set without having to design the heat exchanger network and utility system. These energy targets cam be calculated directly from the material and energy balance. Thus... 

In addition to being able to predict the energy costs of the heat exchanger network and utilities directly from the material and energy balance, it would be useful to be able to calculate the capital cost, if this is possible. The principal components that contribute to the capital cost of the heat exchanger network are... 

Let us take each of these components in turn and explore whether they can be accounted for from the material and energy balance without having to perform heat exchanger network design. 

Having explored the major degrees of freedom, the material and energy balance is now fixed, and hence the hot and cold streams which contribute to the heat exchanger network are firmly defined. The remaining task is to complete the design of the heat exchanger network. 

Heat Recovery, Energy Balances, and Heat-Exchange Networks. The goal of heat recovery is to be sure that energy does the... 

For this process with a ATmin of 20°C, various heat exchanger networks can be devised. Generally, there are four sections in most network problems (see Figure 4.47). These are identified from a balanced composite diagram by... 

The design of the Heat Exchanger Network takes place in the balanced grid diagram. This means that the utilities have been placed on the Grand Composite Curve. As illustrated by the Fig. 10.3, the hot streams run from left to right at the top, and cold streams run counter-currently at the bottom. 

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