Process cooling is used in many manufacturing industries to remove heat from a process. This technology which is quite similar to comfort cooling has increased the efficiency of production processes and operations of equipment ranging from food processing, packaging, plastic injection molding to medical imaging equipment.
In comfort air conditioning where chilled water system is used, the water is cooled to a temperature of 34°F – 45°F or 1.1°C – 7.2°C before being circulated to the entire building where heat is extracted from the environment by circulating the water in the fan coil unit.
The return water is typically heated up by 10°F(5.5°C) and heat is rejected at the condenser by using the compression chiller or absorption chiller. The water is then re-circulated throughout the building and the process is repeated.
These systems in buildings usually have a typical chilled-water operating temperature and a constant flow rate. Pumps are used to circulate the water in the piping of the building.
Process Cooling Applications
In process cooling, the temperature and flow of the liquid will depend on the need of that particular process in removing heat from the process. The temperature of the fluid can range from -20°F or -29°C.
This will have to be determined during the design of the cooling processes in tandem with the equipment. In most processes, the temperature of the water and flow are kept constant irregardless of the load.
These process cooling have been widely used in the following five industries.
#1 Plastic Mold Injection Manufacturing
In the production of plastic goods such as plastic bottles, the hot plastic liquid is injected into the mold that has been designed to produce a plastic bottle or arrays of bottles. The cooling process is required to solidify the bottles before being ejected from the cavity of the mold.
By using a constant chilled-water to cool it, the solidification time can be reduced significantly hence increasing the productivity of the bottles being produced. This will translate to cheaper products for the consumers.
#2 Textiles Production
The production of textiles from materials such as wool, cotton, linen and silk requires a consistent temperature and humidity during each processes as these parameters will affect the quality and productivity of the textiles being produced.
In general, all textiles are hygroscopic, meaning that they tends to absorb moisture from the air and vice versa. Correct RH(relative humidity) and temperature will ensure that the properties of the textiles such as elasticity and tensile strength remain within the usable range. Low RH may cause brittleness and loss of weight.
The RH being used may vary from 65%-85% depending on the materials being processed.
Process cooling helps to ensure that the temperature rise during production activities is minimized thus enabling the factory to run continuously if necessary. The control of RH cannot be separated from the cooling of the space hence the use of precise control technology is necessary.
#3 Food Processing
Chillers or liquid nitrogen/carbon dioxide are used to chill food such as poultry, beef, seafood, bread and sausages. These chilled products can be stored, transported and marketed even to consumers thousands of miles away. There are basically three methods to chill the food.
- Tunnel Cooling has a conveyor belt that moves into a refrigerated tunnel where the food is cooled by using liquid nitrogen/carbon dioxide or chillers. This method is usually used for smaller sized food where shorter time for chilling is sufficient.
- Spiral Freezing uses a conveyor belt to move the products to be frozen into a cold enclosure and blasted by the cold air. Due to its helical rotating, the food can be exposed to the chilled air for a longer period of time compared to the tunnel cooling.
- Blast Chamber uses a room or chamber to blast high velocity of cold air onto the food to be frozen. It is used to freeze larger solid food and the food can be kept in the chamber for many hours depending on the processing requirements.
#4 Machine Tools
Tools or equipment that are being used in industry that get heated up quickly need to be cooled to ensure their continuous operations. Welding transformer gets heated up due to the heat being generated during the welding process. As such, it has to be cooled for proper operation.
#5 Medical Imaging Equipment
Imaging equipment such as MRI or Magnetic Resonance Imaging Scan uses strong magnetic field to create images of tissues in the body of the patient. Most hospitals will have this equipment to detect tumors in the body.
The heat being generated in the superconducting magnet needs to be cooled. One method to cool it is using water-cooled chillers. Keeping the temperature of the equipment constant is necessary for optimum performance. Hence removing the heat generated is critical to ensure its reliability.