Example Problems

Fuel System

Problem Statement:
A fuel distribution terminal must be modeled to facilitate future modifications to meet EPA requirements. The fuel mixture changes with season, with the winter mixture being the most limiting (from a fluid flow perspective). The fuel is stored in a vented tank, with a minimum tank level of 8.2 feet.

The supply piping to two parallel pumps is 10 inch. The pump discharge header is 8 inch, with the diameter ultimately reducing to 4 inch at the individual discharge stations.

Normal operation is to run one pump when one or two filling stations are in use and both pumps when three or four stations are in use. The minimum flow requirement to each station is 1000 GPM.
The first question is whether the current configuration meets the desired criteria.

The first step is to build the network. Since the individual filling station supply lines are identical, only one need be built; the remaining three lines can simply be copies of the first line.

The fluid is then specified (as a user-specified custom fluid with the known properties). Known flow information includes the pressures at the inlet tank and the discharge pressures at the filling stations. The system then solves for the flow rates.

Other Considerations:
Unfortunately this problem did not meet the specified criteria. With DF DesigNet, however, it is easy to identify why and also identify possible solutions. In this case, simply displaying differential pressures identifies where the vast majority of the pump discharge head is lost. A simply change to the pump discharge header size will alleviate the problem.