Removing Heat at the Point of Use
Chillers are refrigerators that cool down samples or processes to preset temperatures by removing heat from one element and transferring it to another, typically air or water. The term “recirculating” refers to the cooling liquid—typically water, water/ glycol, or silicone fluids— that is pumped through the system to be cooled and returned to the chiller. Choice of cooling fluid is critical: The liquid must remain fluid at low temperatures or it will not recirculate; and some good circulators, like ethanol, are highly flammable.
Recirculators are defined in terms of physical size (benchtop to large process units), operating temperature, and cooling capacity. “The range is from small benchtop units to about six feet tall,” says Mark Diener, product manager at Julabo (Allentown, PA). Lab units rarely get larger than that. Process industries requiring high-volume chilling achieve it with liquid nitrogen instead of mechanical refrigeration.
Despite their name, some chillers also provide modest heating, to about 40ºC. These units, which may also cool to about -20ºC, are replacements for water cooling.
Chillers operating down to about -40ºC are relatively inexpensive and use a single compressor. The price jumps significantly for the -40ºC to -95ºC temperature range because these systems use two compressors. Units cooling to below -100ºC require three compressors and may cost in excess of $100,000.
Chiller applications include plastics processing and testing, cryogenic testing, cooling lab instrumentation, biology, and chemical synthesis. One customer of Julabo’s, which was affiliated with the aerospace industry, purchased a low-temperature chiller to conduct a six-month-long vacuum experiment that simulated deep-space conditions. What was placed inside the unit? “That particular application was top secret,” Diener tells Lab Manager Magazine. Similar units are also used in the pharmaceutical industry, he says, to run low-temperature organic synthesis.
One emerging use for chillers is to provide cooling for rotary evaporators, a mainstay of chemistry labs. Many jurisdictions today have enacted strict single- pass water restrictions. These refer to water that is immediately disposed of after use, which has been the norm for cooling water. In many labs today, the water aspirator has been replaced by a vacuum pump, and the cooling water for the condenser with cooling fluid from a recirculating pump. “Some systems daisy-chain two rotovaps to a single recirculator,” Diener says. “And you don’t have to use very low temperatures at all. If you operate your rotary evaporator properly, you can easily remove most solvents with the chiller set at 5ºC.”
Julabo has calculated that a recirculating pump used on a rotary evaporator can pay for itself in less than four years through lower water and sewage costs
Users usually specify chillers by cooling range, but cooling capacity—the amount of heat the unit can remove from a process— is equally important. Customers should always check capacity for the specified temperature. Vendors can usually help with the calculation.
In their recent survey of worldwide customers, Thermo Fisher Scientific (Newington, NH) identified five areas for improving their chiller products: reliability, global suitability, ease of use, flexibility, and service. From lab washers do work and perform advanced and esoteric washing.”
Small, under-counter washers with forced-air drying and HEPA-filter capability represent a growth market for washers, says Espiritu. “Models with these features used to be three feet wide. Now they’re about as large as a home dishwasher, and they can give you glass that is bone-dry in fifteen minutes.” Another market is for washers that clean labware used for trace metals analysis. For this application, the washer replaces a process of soaking in dangerous acid baths and manual rinsing.
“We sell a lot into wastewater treatment plants that use BOD bottles,” says Sprung. “Generally, if they have reusable glassware, they need … to wash it in a way that provides repeatable results. Hand-washing results can vary significantly.”
To Sprung, price is “always a factor” in lab washer purchases because “washers are considered luxury items.” Espiritu agrees—to a point. “Price is more of a factor for buyers who are not familiar with what constitutes a good washer,” particularly when users are not consulted before the acquisition. He continues, “If the wrong washer is purchased, users can feel shortchanged because the washer does not address their requirements. The correct attitude with regard to price is to think long range, and ask, ‘What is the price of not getting the more expensive washer?’” Possible outcomes include inconsistent washing for critical labware, too-long wash cycles, waste of water and cleaning aids, and short service life.
Other factors affecting purchases include warranty, service, brand recognition, and users’ past experience with washers.
Lab workers accustomed to labware washers rarely pine for the days of hand-washing. “For a lot of laboratories… a robust, functional washer is like oxygen,” says Espiritu. “They cannot get through a single day without it.”
Angelo DePalma holds a Ph.D. in organic chemistry and has worked in the pharmaceutical industry. You can reach him at email@example.com.
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