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In this article, our attention will be directed towards 6 important factors to consider when deciding which chiller is most convenient for your specific needs:

1. Operating Principle:

The operating principle in Air-Cooled Chillers consists of dissipating heat into the ambient air. They contain a refrigerant whose main purpose is to absorb heat from the processed coolant and then it releases it into the atmosphere through condenser coils cooled by fans. In contrast, Water-Cooled Chillers use water instead of air to reject heat, excelling at managing high heat loads, particularly in larger laboratory or industrial setups. These systems require access to a water supply. Alternative liquids may be used as coolants in closed systems, such as when geothermal cooling loops are used.

image courtesy of PolyScience¹

2. Efficiency:

Generally, Air-Cooled Chillers are less efficient than their water-cooled analogues, especially in hot climates. This is because their fans require significant amounts of electricity to operate and draw air over the condenser coils. The cooling efficiency of air-cooled chillers is directly related to ambient air temperature. Water-Cooled Chillers, in contrast, use water (usually grey water) as a coolant to remove heat from the refrigerant. This method makes them work more efficiently, as water's superior heat conductivity demands less energy to cool an equivalent amount of heat. 

3. Maintenance:

Air-Cooled Chillers typically require less maintenance compared to water-cooled units. Regular and routine tasks include cleaning the condenser coils at least every three months, brushing or vacuuming them to prevent dust from causing blockages, replacing the air filters, and regularly cleaning the fans and air vents to ensure efficient airflow. Accumulated dust can impede proper cooling, leading to inefficiency. Conversely, Water-Cooled Chillers require more frequent maintenance due to the continuous flow of water, potential for deposits and corrosion, and possibility for water leaks in their system. To ease their maintenance, it is highly recommended to install an in-line filter as preventive maintenance. Water, especially if unfiltered, may carry particles that can block the channels within the chiller's heat exchanger. Employing an in-line filter safeguards the heat removal system and prevents the need for maintenance due to impure water stream and plumbing issues. In closed-loop systems, a water cleaner and clarifier can also be used to help prevent microbial growth.

4. Noise Level:

Air-Cooled Chillers can be noisier due to the operation of the fans. Efforts have been made to reduce noise levels in the air-cooled chillers industry; however, they may still be unsuitable for noise-sensitive environments. This is an advantage for Water-Cooled Chillers as they are generally quieter since they don’t use fans for cooling.

5. Initial Cost and Lifespan:

Air-Cooled Chillers generally have lower upfront costs due to fewer equipment and infrastructure requirements; however, their lifespan may be shorter compared to water-cooled chillers. This shorter lifespan may be attributed to a larger number of internal components, which inevitably make them more likely to break, and a rigorous cleaning checklist that, if not performed timely, can significantly reduce their lifespan, especially in warmer regions where increased temperatures can strain the chiller. 

Water-cooled chillers typically come with higher initial costs due to the extra equipment and infrastructure needed. Nevertheless, they commonly exhibit extended lifespans and may offer better long-term value if the necessary plumbing is already in place. Operating at lower temperatures reduces wear and tear on the machine’s components, increasing its durability. Additionally, their operation at lower temperatures results in decreased energy consumption, translating into long-term financial savings.

Determining the exact lifespan of a machine can often be challenging, but there are methods to estimate its durability. One approach is to review the warranty terms, as machines with longer warranties tend to be more reliable. However, water-cooled and air-cooled chillers generally do not have different warranties if they are provided by the same manufacturer. Warranties will be much more likely to be different when considering systems from different manufacturers. Another option is to consult the manufacturer for insights into the typical lifespan of the machine, although you may not always get a clear answer. 

Air and Water Cooled models Available 

6. Environmental Impact:

Air-Cooled Chillers don't require direct water usage, but they consume more electricity, which could result in increased carbon emissions depending on the energy source. Water-Cooled Chillers use less electricity but there may be environmental concerns related to water usage. As water scarcity and utility prices increase, building water consumption is an increasingly important aspect of sustainability and efficiency. For buildings where water-efficient fixtures and cooling system upgrades have already been made, the final step toward ‘net zero’ water consumption is capture, treatment, and re-use of onsite and auxiliary water sources². Water use can also be dramatically reduced by using closed-loop, geothermal cooling systems, although such systems can be very costly to install.

Conclusions

Taking all of these factors into account we can conclude the decision between them depends on a variety of considerations including space availability, efficiency requirements, cooling capacity requirements, facility capabilities / limitations, initial budget, and long-term operational considerations.

Choosing the appropriate chiller system necessitates a meticulous assessment of all pertinent variables to guarantee optimal performance and cost-effectiveness.

Typically, however, unless the ambient air is excessively hot or contaminated or the cooling capacity requirements are sufficiently great to make it unfeasible, labs find it more convenient and economical to opt for air-cooled chillers. They are 'plug and play,'  requiring simple setup by plugging in, filling with coolant, and operating. In contrast, water-cooled chillers need plumbing for water supply, and if not available, significant facility modifications may be needed.

Less powerful chillers often only come in air-cooled models. This is because they are easier to cool, and therefore facilities generally do not need or want the complexity of setting up water cooling. Sometimes very powerful chillers only come in water-cooled models because air cooling is not efficient enough to cool them. Consequently, for higher efficiency and power requirements, water-cooled chillers would likely be a better fit for your lab.

You can view our entire selection of recirculating chillers, which includes models from many leading manufacturers, at https://waterbaths.net/collections/chillers.

References:

1. https://polyscience.drift.click/ChillersandCoolers
2. Aiming for Net Zero: Onsite Water Treatment Systems/ Charles Upshaw, University of Texas at Austin / Blue Is the New Green: The Water-Energy "Next Is"?