Environmental considerations

Increasing pressures on natural resources have resulted in many countries restricting the use of water run to waste for cooling of instrumentation. The E4800 series can be used in locations where mains water is not available. Corrosion in closed systems can also be minimised by adding inhibitors and, with suitable additives, temperatures below zero can be maintained. A three-term digital temperature controller ensures ease of use and accuracy.

Temperature control

Many instruments measuring physical properties depend on accurate control of temperature and in some processes optimum temperature is essential. With the E4800 series, over-cooling (which affects efficiency) is prevented and the water temperature can be accurately controlled over the range -10 to +60°C.

A commonly misunderstood feature of refrigerated systems is in applications where the control temperature is other than at or near room temperature. When the instruments are to be operated at controlled temperatures below ambient, the extraction deteriorates significantly and, as a guide, the compounded change is 4% per degree Celsius. In practise, the refrigerant gas pressure has to be adjusted to optimise the performance at any particular temperature. However, the E4800 series incorporate automatic adjustment valves in the systems.

The E4800 series are of the ‘closed loop’ type and therefore efficiencies are dramatically improved compared with open bath models. They are simple to set up and to operate, and essentially maintenance free.

Choosing the correct heater/chiller

In order to optimise performance from a heater/chiller system, the correct specification must be selected for a particular application. To cool or heat any instrument or system it is important to obtain the following information from the manufacturer:

* Heat load to be dissipated to water, eg for an electron microscope: diffusion pump heater, lenses, etc
* Flow rate and size of tubing
* Minimum pressure

With this information, consult the Specifications below and select the appropriate heater/chiller. The basic heat load calculation formula is as follows: Flow rate x weight of fluid x specific heat x D T = Heat Extraction.