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The seed of the "Tango Technology" germinated in Peter Huber's mind over 15 years ago. Development in partnership with close contacts in the pharmaceutical industry led to the technology becoming commercially available in the "Unistat" range of products in 1990.
The Tango Technology has been refined and the Unistats have grown to dominate their field in a variety of applications ... here is why.
The traditional form of thermostats is an open bath. Within this bath are the heat exchangers for heating and cooling in the form of coils and a pump for circulation.
For applications that need to be partially or fully submersed in the reservoir, an "open-bath" thermostat is ideal.
If the application does not need to be placed in the bath but has the thermal fluid pumped to it as a "closed loop circuit" then the open-bath thermostat carries operational disadvantages that have a direct impact on the process.
The main disadvantages are 1. The reservoir:
The reservoir serves two functions.
- To contain the thermal fluid
- To allow for the expansion of the thermal fluid as it heats and cools
The larger the external application the greater the "tidal flow" as the fluid expands and contracts will be, so the bath has to be larger to contain it.
The total thermal load that the cooling and heating system must "drive" is made up (mainly) of the total volume of thermal fluid + the process. The larger the bath the less of the generated power will be spent on the application.
This phenomenon is expressed in "watts per litre" (w/l). A simple example that demonstrates this is a kettle. A two litre kettle with a 1 kW heater will have a w/l ratio of 500 w/l and will take "time x" to boil. The same kettle with only 1 litre of water will have a ratio of 1000w/l and will boil in half the time.
Since the control of a reaction depends on the speed with which the jacket of the reactor can be adjusted to initiate the flow of thermal energy, a large volume of thermal fluid acts as effective thermal "slug" which adversely effects response times.
2. The heat exchange surfaces
Thermal transfer depends greatly on surface area. This phenomenon is expressed as a ratio of "watts per square centimetre" (w/cm²). The smaller the surface area the greater this ratio becomes and the poorer the thermal transfer becomes. Heat exchangers in the form of coils have a comparatively small surface area and so are poor at transferring thermal energy effectively.
3. Moisture absorption
It is well known that water migrates to the coldest place and stays. At the bath opening it is seen as condensation but in the reservoir it collects on the evaporator as ice. Since ice is a good insulator, the growing layer of ice prevents heat from travelling from the thermal fluid to the refrigeration system. If the heat cannot be removed from the thermal fluid, it cannot be removed from the process.
4. Oil vapours
At elevated temperatures the thermal fluids give off vapours which condense on laboratory surfaces. They can also create health and safety issues and clog HEPA filters. These vapours also become flammable at temperatures dependent on the thermal fluids being used. This limits the operational range of the thermal fluid.
Tango Technology eliminates all of the above disadvantages.
The fluid circuit is hydraulically sealed, the expansion and contraction of the thermal fluid as it heats and cools is catered for in an "expansion tank". This expansion tank is thermally isolated but mechanically connected to the circulating fluid system.
This means that no matter what the temperature is at the process, the fluid in the expansion tank remains at 2-3 degrees around room temperature.
Being hydraulically sealed means that there is no moisture absorption at low temperatures and no vapours at high temperatures. This has the effect of widening the operational range of a thermal fluid. It also means the elimination of the build up of oily residues in the laboratory.
It is important to note that this is achieved by using "passive" components and the laws of physics. Mechanical or electro mechanical valves have not been employed for safety and efficiency reasons.
Process control is greatly improved because:
1. There is no "reservoir" in the Unistats. The volume of the circulating thermal fluid is minimal (2-4 litres in most Unistats) and so most of the generated heating and cooling power is spent at the application.
This is expressed in watts per litre and the Unistats have the highest ratios.
This results in extremely fast ramp times. The temperature of the jacket can be rapidly adjusted to initiate and maintain the flow of thermal energy enabling tight control over the most dynamic of reactions.
2. Plate heat exchangers are used to transfer thermal energy much more efficiently. The characteristic of a plate heat exchanger is to present a very large surface area within a very low volume.
This is expressed in "watts per square centimetre" (w/cm²). Because this ratio is so low, Unistats capable of not just generating massive thermal powers but also of transferring them rapidly without damaging the thermal fluid.
The net effect is a smaller, more compact and process directed thermostat. Results can be measured in increased yields, faster process times and duplication of results. |
