Chiller, refrigerated circulator, recirculating chiller, heater, what is the difference??
Selecting the proper chiller for your application can be somewhat confusing especially with the large selection of chillers and circulators on the market. The term chiller, refrigerated circulator, and recirculating chiller are all interchangeable to a degree. No matter what name you choose to call it, you are expecting a machine that will provide a specific temperature of cooled, or heated, liquid for your application. The best way to figure out which chiller you need is to answer a few key questions. Ask yourself the following things: What type of equipment am I pairing the chiller with? How much liquid capacity does my equipment hold? What temperature do I need to reach? And how much of a heat load will my equipment put on the chiller? We will discuss of each of these questions in detail in the following paragraphs.
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The first piece of equipment we will discuss is the rotovap. Rotovaps need chillers to operate efficiently, and if you do not have the right chiller for your rotovap you will quickly realize how difficult it is to maintain temps and recover solvents. During evaporation of solvents in a rotovap, the solvent vapor being evaporated will be quite warm. This means there will be a larger heat load on the chiller than other applications. This means we need a chiller with a high cooling capacity. Many chillers that have high cooling capacity, have a smaller temperature range. This is not neccessarily a bad thing. To maintain 10C is much easier to maintain than -40C. When using a rotovap, we want temperatures to be as close to 0C as possible although any temp up to 15C will work fine. Let's compare two Polyscience chillers to see which one would be best for a rotovap. The first is the Polyscience 6160. The temperature range on the 6160 is -10C to 40C and the cooling capacity at 10C is 1925 Watts. The second chiller is the Polyscience 15L Advanced Digital Refrigerated Circulator. The temp range on the 15L is -30C to 200C and the cooling capacity at 10C is 915 Watts. Based on this information, which chiller would be a better choice for a rotovap? If you answered the 6160, you are correct. We can easily deduce that the 6160 is a better choice for a rotovap because it has higher cooling capacity.
Deciding what chiller you need for an extraction system will depend primarily on the temperature you are trying to reach and the capacity of the system. For instance, let's say you have a 4" x 24" fully jacketed column and are planning on using this to dewax solvent. The first thing to think about is heat load. Will there be any heat load on the chiller from this application? The answer is no. The solvent is not being evaporated so there is no heat load to the chiller. But what about temp range? When dewaxing we want to achieve the coldest temps possible. If we were to look at the chillers from the previous rotovap example, the 6160 and the AD 15L, which one would be a better choice for the fully jacketed column? If you answered the 15L, you are correct. The temp range on the 15L is -30C to 200C. This means we can theoretically achieve a temperature of -30C. We don't need very high cooling power because there is no heat load. But what about capacity? For a jacketed column, we want to find the capacity of the volume of the jacket. Once we have this number, we want to select a chiller that will hold roughly twice as much liquid volume as the jacket, this way we can ensure there will be enough cold liquid to circulate through the column and it will not take hours to reach temperature. Now, if we want to also use a chiller for our solvent tank, we would do the same calculation to find out the volume of either the jacket or internal coil depending on which one we would like to circulate liquid through. Once we have this number, we can decide which chiller has enough capacity and a low enough temp range to successfully cool our solvent tank.
What About Heaters?
For certain applications, we might only need a heater. For instance, heating a jacketed base during recovery requires heat only. Heating is a bit more simple to figure out because it is much easier to heat a liquid at room temperature than it is to cool a liquid at room temperature. You will notice some of the chillers we have already discussed such as the Polyscience 15L AD have a large temperature range. The Polyscience 15L AD will heat all the way to 200C. This means you could use this chiller for both heating and cooling. Buying just a heater will always be more affordable than a chiller but, if you have multiple applications that require both heating and cooling, it might be a better option to buy a chiller with a large temp range that can also heat as well as cool.
Chilling Fluid and Chiller Tubing
When deciding what type of fluid to buy for your chiller, start with the temp range that matches up with your chiller. We always recommend Dynalene HC-50 for its low toxicity. It is also non-flammable. HC-50 will start to congeal around -50C. It is a good choice for applications that don't need to get colder than this. If you need lower temps, an ethanol mixture will most likely be needed. Ethanol will not freeze until -173F but it is highly flammable so extreme caution should be taken when using it as a chilling fluid. When selecting chiller tubing, make sure to look at your chillers pump specifications. This will give you a good idea of the pressure the pump is putting behind the liquid. Make sure the tubing you are using reflects that pressure. It should also have a temp range suitable for your application. At very cold temps, some tubing will become brittle. As always, insulated lines will improve cool down times and help the chiller reach its set temperature.
Recommended Equipment/Chiller Pairings
- 2L Rotovap: Polyscience LS -20C to 40C 1/2HP Chiller w/ Turbine Pump
- 5L Rotovap: Polyscience LS -20C to 40C 1/2HP Chiller w/ Turbine Pump or Polyscience 6160 -10C 4.2L 1HP Chiller w/ Turbine Pump
- 10L Rotovap: Polyscience 6160 -10C 4.2L 1HP Chiller w/ Turbine Pump or Polyscience DuraChill -10C to 80C 1.5HP Chiller w/ Turbine pump
- 20L Rotovap: Polyscience DuraChill -10C to 80C 1.5HP Chiller w/ Turbine Pump
- 30L Rotovap: Polyscience DuraChill -10C to 80C 1.5HP Chiller w/ Turbine Pump
- 50L Rotovap: Polyscience DuraChill -6C 42L 5HP Chiller w/ Displacement Pump
- 2L Short Path: Polyscience 7L MX Heated Circulator or Polyscience 7L MX Refrigerated Circulator or Polsycience 7L Standard Digital Refrigerated Circulator or 7L Advanced Digital Refrigerated Circulator
- 5L Short Path: Polyscience 7L Sstandard Digital Refrigerated Circulator or Polyscience 15L Advanced Digital Heated Circulator or 7L Advanced Digital Refrigerated Circulator
- 10L+ Short Path: Polyscience 15L Advanced Digital Refrigerated Circulator or Polyscience 15L Advanced Digital Heated Circulator
- 10L Glass Reactor: Polyscience 15L Advanced Digital Refrigerated Circulator or Thermo Scientific Glacier Series G50 Ultra-Low Refrigerated Circulator
- 20L Glass Reactor: Polyscience 28L Advanced Digital Refrigerated Circulator or Thermo Scientific Glacier Series G50 Ultra-Low Refrigerated Circulator
- 50L+ Glass Reactor: Polyscience 45L Advanced Digital Refrigerated Circulator or Thermo Scientific Glacier Series G50 Ultra-Low Refrigerated Circulator
- 50L Stainless Steel Reactor: Polyscience 45L Advanced Digital Refrigerated Circulator or Thermo Scientific Glacier Series G50 Ultra-Low Refrigerated Circulator
- 1lb Fully Jacketed Columns: Polyscience 15L Advnaced Digital Refrigerated Circulator or Polyscience 7L Advanced Digital Refrigerated Circualtor
- 2lb Fully Jacketed Columns: Polyscience 15L Advnaced Digital Refrigerated Circulator
- 5lb Fully Jacketed Columns: Polyscience 28L Advanced Digital Refrigerated Circulator or Thermo Scientific Glacier Series G50 Ultra-Low Refrigerated Circulator
- #25 Fully Jacketed Stainless Steel LP Tank: Polyscience 7L Advanced Digital Refrigerated Circulator or 7L Standard Digital Refrigerated Circulator
- #50 Fully Jacketed Stainless Steel LP Tank: Polyscience 15L Advanced Digital Refrigerated Circulator
- #100 Fully Jacketed Stainless Steel LP Tank: Polyscience 28L Advanced Digital Refrigerated Circulator