Batch Cooling Chillers
Batch cooling can be defined as cooling “X” pounds of fluid from start temp to final temp for a period of time. Batch Cooling allows the processor to increase or decrease cool down time with a larger or smaller chiller. Quicker the cool down higher the capacity refrigeration tonnage required. Cooling down a 1000gal water tank in one hour requires a larger chiller than it would cooling in 2hours or 8 hour etc.
Example cooling water with specific heat 1.00:
- Btu/hr = 1000gal x 8.34lbs per gallon x 80F start -40F finish x specific heat 1.00.
- Btu/hr = 333,600 or 27.8 tons.
- Btu/8hr = 333,600/8hr = 41,700 or 3.48 tons.
Batch cooling is used in many industries including: Pharmaceuticals, Bakeries,concrete casting, cosmetics, foods etc are just a few applications. A batch of water or fluid can be pre-chilled to a specific temperature before the fluid is added to a mix. The mix could be a food process, dough, concrete cast, cosmetics, flavoring, plastics etc. Chilling a batch of potable water to hydro spray vegetables, minimizes the risk for bacterial growth on food products. Pre-chilling a brine solution to spray on seafood or frozen food products or even some cases food processors will use an FDA approved Dowfrost an antifreeze product. If the solution is other than water we must figure in specific heat. The specific heat is the ability of a liquid, gas or solid to give up heat. Vinyl resin for example has with a very low specific heat of .15 gives up “Btu” heat much slower than water with a sp ht of 1.00. So it would take longer to cool down a solution with a lower specific heat. So special considerations should be made when we are cooling a solution with low sp ht. Maybe a more efficient heat exchanger such as a SS plate type would be more efficient than a shell and tube. A Shell and tube heat exchanger would be 3-6 times larger than a plate and frame or brazed plate type to get the same heat transfer rate. So you have to consider the specific heat in cool down time on batches. If you are quenching a solid such as steel, aluminum in water solution then one would consider the specific heat of the solid.
Whaley Modular Chillers are shown below. Modular chillers are used in batch processes quite frequently because of their ease of increasing capacity after installation. Many processors have loads that could fluctuate greatly over time dependent upon what product they need to produce.
Batches can be tanks of acid solution used in anodizing, electroplating, electro polishing. A batch can be cooled or heated with plate coils that hang on the side of the tank and immerses in the solution. A tube or pipe coil immersed in the tank distributed evenly throughout the bottom of the tank with water or glycol mix circulating through it provides equal distribution of heat and maintains constant batch temperature. In some cases the batch will need agitated to speed up the cooling or heating process. 3-way bypass valves are sometimes installed to “automatically” control the batch temp without having to manual deviate the glycol temperature or flow. This type of batch cooling systems are usually used with heavy particulate loaded long batch tanks such as extrusion pelletizing plastic systems. Tanks that have internal mixers utilize externaljacketed coils that either clamp or butt-weld to the tank. Tanks of this nature are used in dough mixing, wineries, and blending operations. Immersed tube coils or plate coils are sometimes more difficult to install and could interfere with the process. The plate type are more efficient and sometimes easier to install because of the high turbulence created when the liquid is being pumped through the embossed plates.
Below you will see an example of a batch cooling layout that utilizes a gravity flowing chilled water reservoir that eliminates the need for a supply pump.
Another common application is quench tanks. Click here to learn more about quench tank applications..
Each application is unique and here at WPI with our 20+ years of experience can figure out type of heat exchanger and chilling system that best fits each application.