In the industry I work in (personal care products), we aim for 5'/sec flow velocity during flushes and CIPs. The flow rate can pretty easily be calculated from your tube geometry. If you're not sure how to do it i can elaborate.
Note that there are different styles out pumps out there though. Most pumps you'll see at the HB level are centrifugal and have a spec curve that relates flow rate and pump head (pressure). The higher the flow, the less head you get, and vice versa. That 320 gph pump is only going to put out 320 gph when there is 0 restriction at the outlet.