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Chiller ­ What is it?
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Chiller ­ What is it?

The short answer is a piece of equipment that supplies chilled water. But there is so much more.

The short answer is a piece of equipment that supplies chilled water. But there is so much more. In order to provide the chilled water , the chiller needs to work in conjunction with other equipment.  In the following example chilled water is supplied by a water­cooled chiller working in conjunction with a cooling tower and delivering the chilled water to process equipment. We would like to give you an overview of how the system works and why it is important to maintain the equipment.

There are different processes in a building that need chilled water. The air handling unit that supplies cooling to your office is only one example.  Inindustrial applications, some mechanical equipment use chilled water to keep parts of the equipment cool to avoid overheating.

The chiller / cooling tower / process equipment procedures consist of three "loops".  Loop 1 ­ Water is pumped from the chiller's evaporator to the process equipment and back again. Loop 2 ­ Heat is absorbed from the chilled water into the chiller's evaporator and rejected out of the chiller's condenser into the cooling tower water .  Loop 3 ­ Water is pumped from the cooling tower to the chiller's condenser and back again.

Loop 1 ­ Chiller's evaporator to process equipment. The water is pumped between the evaporator and the process equipment in a closed loop system. The water in the closed loop system should be chemically treated but does not require the same attention as the open loop system between the chiller's condenser and the cooling tower.

Loop 2 ­ Chiller's evaporator and condenser.  The evaporator is a heat exchanger in which heat captured by the process water flow is transferred to the flow of refrigerant fluid. As the heat transfer takes place, the refrigerant evaporates, changing from a low­pressure liquid into a low­pressure vapor, while the temperature of the process water is reduced to the desired leaving water temperature.

Next, the low pressure vapor refrigerant flows to a compressor, which performs two functions. First, it removes refrigerant vapor from the evaporator and ensures that the pressure / temperature of the refrigerant in the evaporator refrigerant line remains low enough to absorb process heat at the correct rate.

Second, it raises the pressure / temperature of the outgoing refrigerant vapor to ensure that its temperature is high enough to release its heat when it reaches the condenser, where the refrigerant returns to a liquid state.

Loop 3 ­ Cooling tower to chiller's condenser.  The water between the cooling tower and the chiller's condenser is an open system. Water is pumped from the cooling tower to the chiller's condenser to absorb heat and then is returned to the cooling tower where the heat is rejected to the atmosphere.

The water, which is supplied by the building's water source to the cooling tower to maintain a proper operating level, contains minerals and sediment normally found in water.  Air is forced across the water flowing through the cooling tower to accelerate evaporation which removes the heat from the water. The minerals and sediments in the water supply, combined with the debris in the air, such as dust and dirt, will deposit on the condenser tubes over time reducing he ability to transfer heat from the condenser refrigerant to the cooling tower water which will reduce the capacity and efficiency of the chiller.  To restore your chiller to a more efficient level of service the chiller tubes need to be cleaned annually.

If your chiller is shut down for the winter months ­ now is the time to schedule the annual maintenance.  For chillers that are used for processes that run year­round, we will work around your schedule to find the best time to shut down your chiller to perform the necessary maintenance to return your chiller to optimal efficiency. If you have any questions about your chiller, cooling tower, or process equipment (or any other equipment for that matter) don't hesitate to call us. We are here to answer all your equipment questions. 

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About Dillett Mechanical

Mike Dillett founded Dillett Mechanical in 1996. With over 30 years of experience in commercial and industrial HVAC Mike realized that most industrial and commercial businesses want to reduce their dependency on outside contractors.


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