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The Numerous Uses of Lab Evaporators

Evaporators are versatile tools for labs in different research fields. Here are a few uses for them

by
Sachin Rawat

Sachin Rawat is a freelance science and tech writer based in Bangalore. He holds a master’s degree in biotechnology. Find him on X (Twitter) at @sachinxr.

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Evaporators play a pivotal role in laboratories. There are numerous types of evaporators, each optimized for different applications and scales. This article breaks down how evaporators of different kinds are used across industries.

Cooling

Evaporators are heat-exchanging devices: they take heat from the environment to evaporate some liquid. In air conditioners, for instance, evaporator coils are filled with a refrigerant that absorbs heat before expelling it outside over multiple cycles. The tubes are coiled as it increases the surface area available for heat transfer.

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The refrigerant is cooler than the evaporator’s environment. It gains heat from the warm air and leaves the environment cooler, maintaining it at ambient temperature. Refrigeration evaporators operate on the same principle and find use in biobanks and other long-term storage of biological samples. Super cold storage generally involves nucleate boiling evaporation wherein heat transfer occurs via vapor bubbles formed on the evaporator surface.

On a different scale, evaporators also find multiple use cases in cryogenic research. These include cooling the system under investigation, freeze-drying samples, and coating metals on substrates.

Pharma

Manufacturing pharmaceuticals entails concentrating active ingredients and removing impurities. By removing water and separating different components, evaporators achieve both functions. There is a huge diversity in types of drugs and the volume they are produced at, but there is an evaporator available for every job. The standards for purity are incredibly high when it comes to drug manufacturing. For this reason, the industry commonly uses thin film evaporators. These evaporators use rotors to create a highly turbulent flow that leaves a thin film of the liquid sample on the evaporator's surface. This ensures rapid concentration of heat-sensitive products while maintaining their integrity. Thin film evaporators can handle even viscous or fouling liquids that are common in pharma manufacturing. There is little loss of product, which is critical as many pharma products are high value and low volume.

Albeit on a smaller scale, thin film evaporators are used in academic labs and biomedical/biotech startups as well.

Food and beverages

Food research labs concentrate samples to ensure ingredient integrity and increase shelf life for analyses. Removing water prevents spoilage by denying bacteria conditions to grow. 

Rotary evaporators are a cornerstone of most food research labs. As the evaporation flask rotates, it spreads the sample as a large area of thin film. Since different materials in a sample have different boiling points, they can be separated. This allows food researchers to isolate and extract molecules behind aromas and flavors. The distilled and concentrated materials also simplify further analyses.

Many ingredients are highly temperature sensitive. Therefore, they cannot be exposed to heat for more than a few seconds. Rising film evaporators, also called vertical long tube evaporators, address this limitation. In these evaporators, the product moves from bottom to top in tubes and is heated by steam outside those tubes.

Synthetic chemistry

Synthetic chemists use evaporators to concentrate and dry materials during synthesis. For example, when synthesizing polymers, evaporation removes unreacted monomers, solvents, and other impurities. 

Contrary to a rising film evaporator, the product moves from top to bottom in a falling film evaporator. The product stays in the evaporator columns for a shorter period which reduces thermal degradation, thereby improving product quality. Further, the design uses less energy and enables continuous operation, improving process efficiency. This is why it is an attractive evaporator design for specialty chemicals manufacturers. 

Beyond chemical synthesis, evaporators are routinely used to prepare samples for analysis. Techniques like mass spectrometry and chromatography are sensitive to impurities. Evaporation removes the solvent and impurities, making the sample ready for analysis.

Solvent recovery and recycling

Evaporators concentrate samples by removing solvents but look at it another way and they are also recovering the solvents used. By using evaporators to recover and recycle solvents, research labs minimize waste as well as lower consumables costs.

Rotary evaporators are a popular choice for solvent recovery in part due to their versatility. The vaporized solvent cools down on coming in contact with the condenser and is available for reuse. Falling film evaporators are preferred for ethanol and similar solvents or when larger amounts of solvents need to be recovered. 

Another category of evaporators suited for solvent recovery is the nitrogen evaporator. These evaporators blow a stream of nitrogen over the sample’s surface. Nitrogen transfers heat more efficiently as compared to air and lowers the vapor pressure of the solvent, thereby accelerating evaporation. Nitrogen evaporators provide high recovery efficiency and are a great choice when working with a range of volatile organic solvents.

Nanofabrication

In materials research, nanofabrication finds use in creating nanoparticles. Once the source material is evaporated, it nucleates in contact with a cool surface on the evaporator, creating nanoparticles in the process. Labs also use nanofabrication to design improved materials that are stronger, more durable, or have enhanced surface properties.

Carbon evaporators and electron beam evaporators find use in nanoscience. These evaporators apply a thin conductive film of carbon on non-conductive materials. This makes them accessible to electron microscopy techniques used in designing nanomaterials.

Electron beam evaporators bombard a material with high-energy electrons, sublimating it. The atoms of the material precipitate in a vacuum chamber, creating thin films. The technology ensures high precision and maintains the purity of the source material. Compared to carbon evaporators, electron beam evaporators are a better choice when working with materials that can withstand high temperatures.

Beyond material science, nanofabrication using evaporators is a staple protocol in many labs involved in other disciplines such as semiconductors or photonics.

Most evaporator types find use in multiple research fields, sometimes in conjunction. Advances in materials and evaporator design will improve their energy efficiency. This means a higher steam economy or evaporating more samples and greater product recovery for lower input heat.