Two new devices have been added to PIPE-FLO® Professional version 15 to perform a thermal analysis of heat exchangers used in a wide variety of applications throughout various industries. The heat source/sink device and the heat exchanger 2-pipe device are used to evaluate sensible heat transfer into, out of or between flowing fluids. One of the optional design data fields for these two devices is the flow control device (FCD). Assigning an FCD establishes a process control link to another device in the piping system model to regulate the flow rate through the heat transfer device. It, therefore, controls the heat transfer rate, inlet temperature or outlet temperature as well.
Figure 1. Modeling an Acid Cooling Water System using Heat Source / Sinks with assigned Flow Control Devices.
Figure 1 shows a model of a typical heat transfer application in the pulp and paper industry. It uses two shell and tube heat exchangers in series to cool weak acid from 107°F to 60°F prior to strengthening in the fortification tower. The production rate of weak acid is established by the acid control valve in the FCV operating mode with a set point of 250 gpm. This defines the hydraulic requirements of the piping system on the acid side. These heat source/sinks are set to calculate the heat transfer rate in the thermal calculation dialog to determine the thermal requirements of the acid system that must be met by the two cooling water systems. For example, how much heat the cooling systems must remove to meet the desired quality assurance temperature requirements of the acid system.
The heat source/sinks on the cooling water side are set to calculate flow rate in the thermal calculation dialog and have control valves assigned as the flow control devices. This makes the process control link to the valves, allowing the thermal requirements of the acid system to establish the hydraulic requirements of the cooling water systems.(i.e. how much flow these systems must deliver to remove the heat from the acid.)