Selecting Hot and Cold Side Streams

When a heat exchanger unit is included in the simulation, PRO/II requires all the existing sides to be specified. The streams can be selected from the Simple Heat Exchanger Main Window by pushing the appropriate buttons in the hot and cold sides. However, the buttons cannot be selected at random. PRO/II makes an initial determination of the current Heat Exchanger Type and makes available only those buttons that are valid for entering data. This is done by determining the number of sides to which process streams are connected in the flowsheet. The following describes the various possibilities and the buttons that will become available for each case.

1. Process streams attached to both sides: The exchanger is a two-sided type with process streams connected on both sides. In the Simple Heat Exchanger Main Window both the "Process Streams buttons" are available. In the Process Streams Window, specifying the hot or cold side for one set of feed and product streams automatically sets the side for the second set of streams. None of the "Utility Stream" and "Attach to Column" buttons are available in this case.

2. Process stream connected to one side only: The exchanger can be either one-sided or two-sided. Initially, only the "Process Stream" buttons are available, and you must first specify the side to which the process stream belongs using the Process Streams Window. Once the process stream side has been selected, the "Utility Stream" and "Attach to Column" buttons on the unspecified side become available. You then have the option to neglect the other side completely (a one-sided exchanger) if the second side's process conditions are not required for the simulation. If the second side is a part of the simulation (two-sided exchanger), you can then select either a utility stream or a column internal stream by pushing the appropriate buttons. Note that when the process stream's side has been specified, the second "Process Stream" button will not be available.

3. No process streams attached: The exchanger is two-sided with one side attached to a column and the other side containing a utility stream. When you specify the side to which the column internal stream belongs, PRO/II allows you to select only the "Utility Stream" button on the other side, or vice versa, thus ensuring a valid entry. Note that both the "Process Stream" buttons are not available in this case.

The following combinations are not allowed in PRO/II:

(a) Utility streams on both sides,

(b) Both sides attached to column,

(c) Utility stream or column internal stream on one side, and leaving the second side unspecified.