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Quotes - Engineering - SalesU-Tube Cooling Applications
On cooling duty the design question is less about thermal capability and more about which stream fouls and how the exchanger will be cleaned. That makes a removable bundle worth a great deal, and it makes the decision about which fluid runs in the tubes more consequential than on heating duty.
What Decides the Design
Coolant type and its available supply temperature, which varies seasonally on tower water. Fouling factors on both sides based on actual water quality and process history. The velocity band that keeps both streams turbulent without eroding tubes. And the pressure drop available, which on gas cooling is frequently the binding constraint rather than surface area.
Why U-Tube Suits Cooling
The bundle withdraws, so the shell side can be hydroblasted. Put the fouling stream on the shell side and the clean one in the tubes and the unit stays maintainable for its whole life. Free thermal expansion also handles the seasonal swing in cooling water temperature, which is larger than most designs acknowledge.
The clean one, because tube interiors cannot be mechanically cleaned through a U-bend. Where tower water is the fouling stream, it belongs on the shell side despite the common instinct to put cooling water in the tubes.
As much as your experience supports and no more. Excessive fouling factors produce an oversized exchanger that runs at low velocity when clean, which encourages the very fouling the allowance was meant to cover. Real water quality data beats a default table.
Considerably. A tower supplying 85 degrees in summer may supply far cooler water in winter, which changes both the duty achieved and the control behaviour. Size for the worst case and check the behaviour at the best.
Almost always the cooling water supply temperature. A tower's approach to wet bulb sets the supply, and on a hot humid day that is the highest it gets. If the exchanger was sized on an optimistic assumption, summer is when it shows.
Usually, provided it is sized for the summer case and the control arrangement can turn down enough in winter. Where the range is very wide, a control valve on the coolant side or a bypass arrangement is often needed for stable operation.
