Condenser Vacuum Control in Steam Infusion Heater for Extend Shelf Life Milk Products

Condenser Vacuum Control in Falling Film and Forced Circulation SystemsGLM Hydro Evaporator Problem Solving: – A small dairy company is operating a steam infusion heater to produce extended shelf life milk products. Our customer struggled with their cooling section of the system that had a cooling water flow control to regulate the vacuum pressure of the condenser.  Simply by pumping more water through the condenser if they required a deeper vacuum or pumping less cooling water through the condenser to raise the vacuum, they controlled the vacuum. The condenser was an indirect tubular condenser directly coupled to a standalone cooling tower. The pressure of in the condenser is measured and the value of the pressure reading controlled the cooling water flow. At a glance there was nothing wrong with this, you would say.

Unbalanced System

Throughout the summer the customer had no issues at all keeping the system running on operating conditions, but when winter came the problems began. There was a fluctuation of pressures and the process pressure was fluctuating a lot which caused the system to be very unbalanced. After our investigating on what caused the issue we found that by controlling the cooling water flow in the winter with a better cooling performance of the cooling tower, the flow was reduced. This happened because the cooling water feed temperature was naturally much lower in the winter than in the summer. By reducing the inlet flow with cooling water feed of a low temperature the water load on the cooling tower was reduced too much. The flow in the condenser tubes was barely turbulent. It was still functional but the reduced flow caused a faulty water distribution in the cooling tower. As a result the cooling tower was constantly loosing cooling capacity which made the cooling water temperature to go up.

This increased the pressure in the condenser which created a higher water flow output from the controller. To bring the condenser shell pressure down, higher water flow on the cooling tower made it to perform until the pressure came down and the entire cycle would start again.

Air-Bleed Connection

To eliminate this effect we constructed a simple air-bleed connection on the condenser. The air-bleed allows air into the condenser which reduced the heat transfer area in the condenser. The result was a constant water flow in the system and a trouble free performance throughout the year.

Contact us for more information when your installation has these or other kind of issues.

Jan de Geest
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