Heater temperature

The experimental investigations of boiling instability in parallel micro-channels have been carried out by simultaneous measurements of temporal variations of pressure drop, fluid and heater temperatures. The channel-to-channel interactions may affect pressure drop between the inlet and the outlet manifold as well as associated temperature of the fluid in the outlet manifold and heater temperature. Figure 6.37 illustrates this phenomenon for pressure drop in the heat sink that contains 13 micro-channels of d = 220 pm at mass flux G = 93.3kg/m s and heat flux q = 200kW/m. The temporal behavior of the pressure drop in the whole boiling system is shown in Fig. 6.37a. The considerable oscillations were caused by the flow pattern alternation, that is, by the liquid/two-phase alternating flow in the micro-channels. The pressure drop FFT is presented in Fig. 6.37b. Under... 

The time variation of the mean and maximum heater temperature is presented in Fig. 6.39. The mean heater temperature (i.e., the average temperature of the whole heater) changed in the range of ATav = lOK. The maximum heater temperature changed in the range of ATmax = 6 K. Comparison between Figs. 6.37,6.38 and 6.39, shows that the time period (frequency) is the same for the pressure drop, the fluid temperature at the outlet manifold, and the mean and maximum heater temperature fluctuations. It also allows one to conclude that these fluctuations are in phase. 

When the heat flux is increased, at constant value of mass flux, the oscillation amplitudes of the pressure drop, the fluid and the heater temperatures also increase. 

Fig. 6.39 Time variation of average and maximum heater temperature at q = 200kW/m. Reprinted from Hetsroni et at. (2006b) with permission...

A common interpretation of the runaway stage is when both the first and second derivatives of the average time-temperature curve are positive. However, because we had an external heat source in our tests, we had to account for the external heater temperature "T ". 

Additional considerations in the design and operation of a remote hydrogen plasma system include the following (1) convective heat transfer between the downstream gas and the specimen can introduce a significant difference between the heater temperature and the specimen surface temperature (this effect is generally not as severe as for direct immersion in... 

The reformer was operated for over 554 h, which included 402 h of reforming operation and 152 h of hot standby. During hot standby, the catalyst was maintained in the reduced state by flowing 50 cm of hydrogen through the catalyst bed, which was kept at a minimum of 260 °C. The reactor was operated over a heater temperature range of 260—300 °C and up to 70 psia. A methanol and water mixture (S/C 1 1 molar) was fed at 1.5—3.5 mL/min. Table 5 summarizes the device performance. 

Plot the sensitivity diagram of cycle efficiency versus open feed-water heater temperature. 

A microcomputer based control and data acquisition system is required to monitor the 10 thermocouples in the sample and to control the heater temperature. For the latter, the rate of change of the thermocouple in the slab was used and power to the cartridge heaters varied. Details are given by Duever (3) and in a WCPD report (4). 

Pump flow rate accuracy and gradient accuracy Detector linearity of response, noise, drift, and wavelength accuracy Injector precision, linearity, and carryover Column heater temperature accuracy... 

Results from a quasi steady-state model (QSSM) valid for long crystals and a constant melt level (if some form of automatic replenishment of melt to the crucible exists) verified the correlation (equation 39) for the dependence of the radius on the growth rate (144) and predicted changes in the radius, the shape of the melt-crystal interface (which is a measure of radial temperature gradients in the crystal), and the axial temperature field with important control parameters like the heater temperature and the level of melt in the crucible. Processing strategies for holding the radius and solid-... 

Figure 19 shows sample isotherms and interface shapes predicted by the QSSM for calculations with decreasing melt volume in the crucible, as occurs in the batchwise process. Because the crystal pull rate and the heater temperature are maintained at constant values for this sequence, the crystal radius varies with the varying heat transfer in the system. Two effects are noticeable. First, decreasing the volume exposes the hot crucible wall to the crystal. The crucible wall heats the crystal and causes the decrease in... 

Few calculations of three-dimensional convection in CZ melts (or other systems) have been presented because of the prohibitive expense of such simulations. Mihelcic et al. (176) have computed the effect of asymmetries in the heater temperature on the flow pattern and showed that crystal rotation will eliminate three-dimensional convection driven by this mechanism. Tang-born (172) and Patera (173) have used a spectral-element method combined with linear stability analysis to compute the stability of axisymmetric flows to three-dimensional instabilities. Such a stability calculation is the most essential part of a three-dimensional analysis, because nonaxisymmetric flows are undesirable. 

Process variables processing or heater temperature expressed in temperature difference ATp = Th — T0, and screw speed n... 

Process variables pultrusion speed u, initial temperature To, die or heater temperature Th (AT = Th — To), inital degree of cure c, and final degree of cure c2,... 

Figure 5.25 Experimental and computed center-line temperature history during heating of an 8 mm thick PMMA plate. The initial temperature To=20°C and the heater temperature Ts=140°C. [7]...

Determining the effect of viscous dissipation in the metering section of a single screw extruder. Consider a 60 mm diameter extruder with a4 mm channel depth and a screw speed of 60 rpm. The melt used in this extrusion system is a polycarbonate with a viscosity of 100 Pa-s, a thermal conductivity of 0.2 W/m/K and a heater temperature of 300°C. To assess the effect of viscous heating we can choose a temperature difference, AT of 30K. This simply means that the heater temperature is 30K above the melting temperature of the polymer. For this system, the Brinkman number becomes... 

In the plastication step of the process, melting is critical in controlling cycle time. Also, during thermoforming, the heating of the sheet is the most time consuming step of the whole process. For example, if we consider the melting of an infinite slab, at an initial temperature of To, as presented in Fig. 6.61, the heat supplied by thehot wall, set at a heater temperature of Th, will create a layer of molten polymer of thickness, X (t). 

Processing conditions - Heater temperature, T, and rotational speed of the screw, nu... 

Since we are scaling the system with the same material, we can assume that the material parameters remain constant, and for simplicity, we assume that the heater temperature remains the same. In addition, we will fix our geometry to a standard square pitch screw ( =17.65°) and therefore, a channel width proportional to the diameter. Hence, the parameters to be determined are D2, h2 and n2. 

Figure 2.38 Schematic of the suspended-tube reactor (left and middle) and SEM (right) showing four suspended SiNx tubes connected to the Si reaction zone, Si slabs thermally linking the four tubes and a meandering Ti/Pt resistive heater/temperature sensor [72] (by courtesy of L. R. Arana).

The temperature increase in the single wells is clearly visible in the horizontal cross-section and in the vertical cut. The gas temperature in the wells also depends on the material of the titer-plate. In Figure 3.63, the gas temperature obtained in a steel titer-plate (heat conductivity 30 W mKT1) was compared with that in a titer-plate made of a less conductive material such as an aluminum oxide ceramic (heat conductivity 3 W mK-1). In either case, the gas temperature does not exceed the temperature of the solid material by more than 0.5 K and in the solid material between the wells this temperature drops towards the heater temperature. 

A sophisticated integrated flow-through PCR chip was fabricated (see Figure 9.11). Three reaction chambers, connection channels, thin-film resistive heaters, temperature sensors, and optical detectors are fabricated on a Si wafer. A thin... 

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