Setpoint temperature

Bimetallie elements are widely used in instruments sueh as thermostats to sense or eon-trol temperatures. There are several bimetallie element types available, sueh as straight strips, eoils and dises, but all rely on the same working prineiple. In its most basie form, the bimetallie strip eomprises of two dissimilar metal strips bonded together, usually of the same surfaee area, but not neeessarily of the same thiekness thermostat. The eom-posite metal strip is elamped at one end to aet as a eantilever beam, and is horizontal at a partieular temperature. When the temperature is inereased, the strip defleets in the direetion of the metal with the least eoeffieient of linear expansion. Its working prineiple relies on the faet that the metals will expand at different rates as the strip is heated. The purpose of this defleetion is to typieally eause the strip to make eontaet with a switeh or eomplete an eleetrie eireuit at a partieular setpoint temperature above the ambient. 

For the purposes of meeting a eustomer speeifieation, a toleranee for the thermostat setpoint temperature ean be estimated at 3o-Ar) from whieh the approximate thermostat speeifieation beeomes ... 

The very low storage temperature and low operating temperature specifications (see Section 4.3 below) also required dedicated design features because many of the components, such as the pumps and processors, cannot operate at very low temperatures. Because of this limitation there were added to several components cold start heaters controlled by snap switches. Further, an industrial temperature grade microprocessor was used in the SDU. With the snap switches the cold start heaters can come on when the power is applied at less than about 32°F/0°C. The snap switches cut off the cold start heaters and apply power to the full CBMS II system once their setpoint temperature is reached. 

The results are shown in Fig. 5.9 as a function of the set-point temperature for both the model-based and the PID controller. In both cases, the critical 6 increases with the setpoint temperature since a more efficient heat exchange is required when... 

Elimination of parallel ramping is accomplished by introducing an integral function (Figure 2.16 middle) which continuously sums the difference between furnace and setpoint temperatures as swept through time. This area, multiplied by a weighting factor, is added to the proportional portion of the control instruction. If the furnace temperature is persistently below the setpoint, this area continues to accumulate until the furnace temperature is forced up to the setpoint, at which time no additional area is accumulated. 

To maintain the sample at the setpoint temperature during a self-feeding reaction in a power-compensated DSC, small sample mass (e.g. <10 mg) and excellent thermal contact between the sample and its container, as well as the container and the chamber, are required. Figure 3.15 shows the rather unusual effects of using excessive sample masses of glass in... 

For shrinkage rate control [15], the specimen is generally heated at a constant rate into a temperature region where shrinkage begins, and then the system switches over to shrinkage rate control. If the setpoint temperature required to main-... 

The oven is stabilized at the setpoint temperature for at least 30 min before the measurement is performed. For the test the experimental temperature, measured by the temperature probe, and the oven display are registered and documented for 30 min in intervals of 10 min. 

It is noted that, unlike the conventional thermocycler, the control system for the TFRT prototype includes the ramp time in the time at each temperature. Thus, although the system is set to a given temperature for a fixed time (e.g., 10s for the rapid cycling case), the prototype takes as much as 7s to make temperature transitions so the total time at the setpoint temperature is less than the value given in the protocol. 

Forty-five min before the mill is to resume, raise the heat zones setpoint temperatures to 2250 F (1232 C) ... 

Set the desired setpoint temperatures, compare them with the actual values... 

However, let s consider the function the airflow plays. The air heats the pellets in the hopper to the setpoint temperature. The air also provides a low dewpoint, dry-air environment that helps to draw the moisture out of the pellets. As the moisture comes to the surface of the pellets, the air quickly absorbs it and carries it away. 

But, again, how much airflow really is required to do this job You need sufficient cubic feet per minute to heat the incoming polymer, at the applicable throughput rate, from its initial temperature to the desired setpoint temperature, overcoming heat losses through the system s hoses and hopper. Poor system design and lack of insulation will increase heat loss and require additional airflow. 

Finally, the sectors of the generator, of different pedigree and position, are compared in terms of the main polarization effects. The polarization behavior has been investigated at fixed setpoint temperature and overall fuel consumption. On this basis, a parameter estimation, using a polarization model of a single cell, has been performed and used for the analysis of the local activation effects. It has been shown how the local fuel utilization and temperature affect the estimated local anode exchange eurrent density values. 

The generator setpoint temperature Tqen) is the highest temperature measured by five thermocouples placed in the central zone of the generator. This variable can be controlled by the operator, but in the experimental sessions it has not been considered as a independent variable (factor). Its value depends on the value imposed to the air stoichs factor. 

A with overall fuel consumption FC=84.25% and setpoint temperature... 

The tests have been performed maintaining constant the generator setpoint temperature at the value of 967°C this value of temperature is automatically maintained from the system acting on the air flow. A current variation causes a variation of the inlet air temperature this is controlled by a by-pass valve of the low temperature heat recuperator. Besides, a current variation causes a variation in the thermodynamics condition of the stack to maintain constant Tqen, the control system operates on the mass flow of the inlet air flow. 

In the case of this test session, the fixed variables have been the generator setpoint temperature, and the overall fuel consumption in two different values. All the other variables were free to vary, in particular the air flow and the inlet air temperature (Tair,in)-... 

The effect of the air stoichs is coincident to a modification of the setpoint temperature of the generator therefore, where the voltage sensitivity to air stoichs is high, it means that the voltage sensitivity to a modification of the setpoint is high. Of course, this is due to the fact... 

Figure 18. Correlation between voltage sensitivity to air stoichs and to generator setpoint temperature.

As expected, it seems to occur a linear correlation between the voltage sensitivity to air stoichs and to generator setpoint temperature (Figure 18). It is a direct correlation (same trend), because both cause a thermal effect on the generator. 

The analysis was performed during real operating conditions of the generator, thus only short-range V-I characteristics were measured. The current was changed between 435A and 475A, at fixed overall fuel consumption of 84.25% and setpoint temperature of 967°C. 

Solid Oxide Fuel Cell temperature (K) setpoint temperature (K) air pre-heating temperature (K) thiekness of the anode layer (em) thiekness of the eathode layer (em) eell voltage (V) diffusion overpotential (V)... 

The control system contains a comparator, which compares the actual temperature, Ta (measured by the temperature sensor), with the desired or setpoint temperature, Ts, to provide an error or deviation signal, e. The signal is positive when the process is below setpoint, zero when the process is at setpoint, and negative when the process is above setpoint. The proportional term, Kj, gives an output proportional to the error ... 

In a real process, it is rare that the power input required to maintain setpoint temperature is exactly 50% of full power. Therefore, the temperature will increase or decrease, adjusting the power level until an equilibrium condition exists. The temperature difference between the stabilized temperature and the setpoint is called offset or droop. The amount of offset can be reduced by narrowing the proportional band. However, the proportional band can be narrowed only so far before instability occurs. An illustration of a process coming up to temperature with an offset is shown in Fig. 4.27. 

This resetting can be done manually or automatically. With manual reset, a potentiometer is used to electrically shift the proportional band. The amount of shifting has to be done in small increments until the controller power output matches the process power demand as setpoint temperature. 

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