Keeping Step With Dairy Chillers, Plate Exchangers and Coolers

Published on Wed, 06/13/2018 - 10:44am

 Keeping Step With Dairy Chillers, Plate Exchangers and Coolers

 By Bruce Derksen for American Dairymen Magazine

 As I considered the topic of dairy chillers and coolers, I thought I had a firm grasp of the subject.  I mean, how much can there be to it?  You cool the milk, put it in a tank just like dairy farmers have been doing for decades and the wheel just keeps on spinning.  Nothing to see here, right?

But as I researched the subject, I learned that the old saying is true- the more things stay the same, the more they change.  
In the days of the average dairy farm existing almost in a vacuum, relatively stable in size and numbers, the milk was generally pumped from the four or six cow parlor to a refrigerated collection tank where it was cooled over time and later picked up at regular intervals by the dairy truck.  Almost every dairy had a similar number of cows and it was very close to a one size fits all mentality.  The tank that was installed twenty years ago to match the forty cow herd stayed in use until it fell apart, barring a major equipment malfunction.
But as life makes a habit, things are constantly changing.  The severely depleted number of overall producers are adapting by installing larger variable sized robotic milking parlors that can service as many as eighty cows at one time in extremely large operations.  Imagine all that milk rushing from that many cows into a lowly collection cooler tank.  The math to quickly cool such large amounts of product safely simply does not compute, forcing companies to step up their technologies of efficient chillers, plate exchangers and coolers.

Interviewing some very knowledgeable people in the field, I learned of numerous and varied ways that this problem is being attacked- first and foremost being an updated and computer controlled cooler tank. It is an accepted fact that having the cooler and refrigerant system doing the majority of the work bringing the milk to the proper temperature and holding it there, is still the most energy efficient way to proceed, but depending on the size of the dairy operation, taking into account the amount of cows milked in total and at specific times, plus the amount of production from those cows, further help may be needed in getting the milk cooled properly.
As dairies expand, beyond upgrading their coolers, many producers are adding combinations of chillers or thermo- plate heat exchangers, run either by water or glycol and water mixtures. For those with a sufficient amount of cold well water available, a plate heat exchanger can be added to use this supply, pre-cooling the warm milk before it reaches the milk cooler, thereby easing the energy required by and work load placed on the cooler, cutting the operating time of the refrigeration unit by as much as fifty percent.  Depending on the size required, these units can be wall or floor mounted. The basic principle of these plate exchangers is to run cold water through channels on one side while the warm milk does the same through channels on the other side of the exchanger.  Depending on the capacity required, milk can be cooled through single or multiple passes before it is directed to the cooler tank. The water supply, now warmed from the heat of the fresh milk, can be re-circulated back as drinking water for the cows.
Another option for expanding operations is to install a pre-cooler or chiller along with a plate exchanger.  These compact chillers cool a glycol water solution that is circulated through the plate heat exchanger thereby cooling the milk quicker, again saving energy usage on the tank refrigeration unit.  The warmed water is directed back to the reservoir tank to be re-chilled and used again in the process.
All of these options are computer controlled energy efficient units that can be used alone or in combination before the milk reaches the tank cooler.  Technology changes and advancements are inevitable, driven by the requirements of the dairy industry’s supply and demand.  As dairy farms grow in size to meet these demands, the need for more adaptable, reliable, and cost effective energy efficient coolers, chillers and plate heat exchangers become paramount, offering today’s producer many viable choices to fit their ever changing operations.