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Saturday, 16 February 2019

CHILLERS

          A chiller is a machine, its function is to remove heat from a liquid or from one location (Generally process equipment or product) to another place (Genarlly the air outside the manufacturing facility) through a Vapour-compression cycle or absorption cycle. To transfer the heat to and fro from the chiller we commonly use water or water/glycol solution. This liquid is recirculated through a heat exchanger to cool equipment, or another process stream (such as air or process water). As a necessary by product, refrigiration process creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes.

          Chilled water is used to coll and dehumidify air in midum to large commercial and industrial facilities. Water chillers are water cooled, air-cooled, or evaporatively cooled. Water cooled system can be provide efficiency and doesnt harm to the environment when compared to air-cooled systems.

          Industrial water chillers are used to cool products and machinary, like injection molding, tool and die cutting, food and beverage, chemicals, lasers etc.,

          Regardless of industry and process, we have to make sure that we have sufficient cooling system which gives productivity and cost saving.

How does a Chiller Work?
          In most process cooling applications, a pumping system circulates cool water or a water/glycol solution from the chiller to the process. This cool fluid absorbs (removes) heat from the process and this warm fluid returns to the chiller. By this process the heat from the process transfers to the chiller.

          Chiller contains a chemical compound called a refrigerant. There are many types of refrigerent and their applications depending on the process temperatures we required. All refrigerents works on the same basic principle that compression and phase change of the refrigerent from a liquid to a gas (vapour) and back to liquid. This process of heating and cooling the refrigerent and changing it states (liquid-vapour-liquid) is called refrigeration cycle.

          The refrigeration cycle starts with a low-pressure liquid/gas mix entering the evaporator. In the evaporator, heat from the process water or water/glycol solution is transfered to the refrigerent, which changes it from a lo-pressure liquid to a low-pressure gas (vapour). The low-pressure gas enters the compressor where it is compressed to high-pressure gas. The high-pressure gas enters the condensor where ambient air or condenser water removes heat to cool it to a high pressure liquid. The high-pressure liquid travels to the expansion valve, the expansion valve controls the amount of liquid refrigerent enters the evaporator, thereby beginning the refrigeration cycle again.

          There are two types of condensers used chillers; they are air-cooled and water -cooled. An air-cooled condenser uses ambient air to cool and condenstae the hot refrigerent vapour to a liquid. It can be located inside the chiller or outside the chiller, but its ultimate function is to remove the heat from chiller to the air. In water cooled condenser, water which is circulated from the cooling tower cools and condenses the refrigerent.

Best chiller for your process and selection:

          Chillers are ranges in many sizes and design. Chiller selection depends upon total life cycle cost, the power source, evoporator capasity and material, condenser capasity and material, ambient temperature, coolant, discharge temperature of fluid, and COP. Based on these factors chillers are available as small, portable units to large central chillers.       
     

Image Courtesy: The engineeringmindset.com


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