Hard temperature control

These are also referred to as hard temperature control, if heat is drawn from the mould, and soft temperature control, if heat is to be supplied. Separate temperature control for the two halves of the mould is also important from this point of view. The parts of the mould on which the component is shrunk, such as cores, for example, will accept more heat, and thus will be more strongly heated, if they are not temperature controlled in a suitable fashion. Parts of the mould from which the component shrinks away accept less heat and will therefore remain colder without temperature control. In extreme cases, it can even happen that one half of the mould, with the core parts, has to be cooled, while the other half has to be heated, so as to obtain the same mould temperature in both halves of the mould. 

If hard temperature control is possible and neeessary, its quality has an essential part to play in whether the proeess is economically viable, because inadequate cooling means the cycle time is extended. The ejeetion losses here can be up to 100%. 

The cheapest fluid temperature control can be carried out using circuit water. Of course, it is only suitable for hard temperature control. For this purpose, a water distribution system is provided in all parts of the injection moulding machines, to which the temperature control circuits of the mould can be connected. The cooling intensity is set by the water throughput using valves. So as to obtain values with a certain amount of repeatability, throughput gauges and thermometers (in the counterflow) are required in each circuit. 

Oil is used as a temperature eontrol mediiun for cycle temperatures of over 95 °C. As a rule, a temperature range of 30 to 250 °C can be covered using these units, which can also be used for cycle temperatures below 95 °C. They are less suitable for hard temperature control, of course, as the heat absorption capacity of oil is smaller than that of water. Thus more heat can be transferred using water than oil, for the same amount of eirculated fluid. 

Temperature control Of the factors mentioned, temperature is probably the easiest to control this can be accomplished by means of a thermostat or by operating at the boiling point of the testing solution with an appropriate reflux condenser to maintain the solution at a constant concentration. Control to 1°C is not hard to accomplish. 

It is interesting to note that when the same reaction was performed using a variable frequency MW system [49] with temperature control at 80 °C in the absence of a solvent, it occurred at the same rate as a similar reaction heated conventionally at the same temperature. The use of variable frequency provides very uniform heating, minimizing the possibility of hot spots. Thus it can be concluded that the modest rate enhancement observed in ethanol under reflux was because of hot spots or to a general superheating of the solvent. Again, it should be emphasized that these modest MW rate enhancements should not be taken as hard evidence for nonthermal MW effects. 

Phosphonates are commonly used in laundry powders at 0.5-1.0% of the powder, DTPMP and EDTMP for all uses and HEDP mostly for hardness ion control. Wash conditions for powder detergents are usually pH 9-10 and typical temperatures of 40-60 °C, although there is a strong drive to reduce this to 30 °C or even to use a cold water wash. 

Ceramic Durable, good zoning, lower cost, good temperature control High installation cost, hard to find burned-out elements, below average temperature -response time... 

The control system must manipulate heat removal from the reactor, but what should be the measured (and controlled) variable Temperature is a good choice because it is easy to measure and it has a close thermodynamic relation to heat. For a CSTR. temperature control is particularly attractive since there is only one temperature to consider and it is directly related to the heat content of the reactor. However, in a spatially distributed system like a plug-flow reactor the choice of measured variable is not so clear. A single temperature is hardly a unique reflection of the excess heat content in the reactor. We may select a temperature where the heat effects have the most impact on the operation. This could be the hot spot or the exit temperature depending upon the design of the reactor and its normal operating-profile. 

The reconstituted freshwater used during the D. magna culture and tests was prepared following a recipe recommended as being suitable for producing a hard water by the US Environmental Protection Agency (USEPA, 1975). The tests were carried out in a temperature-controlled room set at a nominal 20 2°C with artificial illumination of the test vessels on a 16 h light/8 h dark automatic cycle. 

Combining the hexachloroantimonate salt of the trichlorocyclopropenylium ion 13 with N-(trimethylsilyl)dimethylamine resulted in the transamination reaction, which was controlled by variation of the stoichiometry and reaction temperature. The reaction afforded the series of 1-amino-2,3-dichloro-, 1,2-diamino-3-chloro- and 1,2,3-triaminocyclopropenylium ions (14-16) in reasonable to good yield (50-100 /o). When the chloride, tetrafluoroborate or tri-fluoromethanesulfonate ion was used as a counterion, the reaction was hard to control and triamination occurred exclusively. ... 

---