Low thermal mass

The thermal mass of parts and tools and the heating capacity of the autoclave naturally limit the maximum heating rate. Attempting to increase the heat-up rate by overheating the autoclave air can result in overheating of areas of the assembly with low thermal mass. 

The vent sizing package (VSP) was developed by Fauskes Associates, Inc. The VSP and its latest version VSP2 employ the low thermal mass test cell stainless steel 304 and Hastelloy test cell with a volume of 120 ml contained in a 4-1, high-pressure vessel as shown in Figure 12-13. The typical ([t-factor is 1.05-1.08 for a test cell wall thickness of 0.127-0.178 mm. Measurements consist of sample temperature Tj and pressure Pj, and external guard temperature Tj and... 

The device consists of a low thermal mass test cell of 110 ml volume. This is made of stainless steel with a 0.015-mm wall thickness, but test cells made from other materials can be used. The contents of the cell are mixed using either a magnetically driven stirring bar or a direct drive agitation test cell. The test cell is... 

Modern low-density insulation such as those based on ceramic fibers can be used to save energy in plant operating on a batch basis. The low thermal mass permits a rapid heating and cooling period that can save a substantial amount of energy. With continuously operating plant the advantages are not so pronounced. 

Fig. 4. Microwave heating system showing a micro-fluidic chip with a golden film (10 nm thick) patterned on the channel and to act as an efficient heating patch, which will have high thermal energy but low thermal mass...

For capillary GC, the split/splitless inlet is by far the most common and provides an excellent injection device for most routine applications. For specialized applications, there are several additional inlets available. These include programmed temperature vaporization (PTV) cool on-column and, for packed columns, direct injection. PTV is essentially a split/splitless inlet that has low thermal mass and a heater allowing rapid heating and cooling. Cool injection, which can be performed in both split and splitless mode with the PTV inlet, reduces the possibility of sample degradation in the inlet. Capabilities of the commonly available inlets are summarized in Table 14.3. 

The accuracy of temperature controllers and sensors is typically about 0.1°. Because of their high-thermal mass, packed columns are more often operated isothermally, while due to their low-thermal mass, capillary columns are most often temperature programed. Important parameters related to basic column dimensions are shown in Table 14.4. 

Like cold on-column injection the PTV has a low thermal mass, so can be heated and cooled quickly. However, unlike cold on-column the sample is injected into an injector liner and not direct onto the column. Unlike conventional split/spUtless injection, the aim is to make use of volatility selectivity of the system rather than to inhibit it. By selecting an appropriate starting temperature, the anal34es condense in the liner if desired the solvent may be flushed away through... 

The thermal properties (i.e., density, specific heat capacity, and thermal conductivity) have a particularly strong influence on the curing behavior. The exothermal peak temperature is one example It can differ significantly between a composite mold with low thermal mass and a metal mold [35], A more thorough discussion of pros and cons of different mold materials can be found in Morena [37]. 

Blanket-type electrical heaters are often used in combination with low thermal mass GRP tools (e.g., in the tooling concept advocated by Plastech TT, UK). The drawback with electrical heaters is that locally very high temperatures can occur. This can damage the tool and give an unacceptable variation in the curing process. 

The power compensation DSC instrument was first described by Watson et al.3) and by O Neill4) and it was developed into a commercial instrument by the Perkin-Elmer Corporation. It utilises separate sample and reference holders of low thermal mass, with individual heaters and platinum thermometers, as shown schematically in Fig. 1. In addidion to controlling the average temperature the instrument employs a... 

Firing of Enamels. Firing can be carried out in intermittent box-type furnaces or continuous furnaces. The dryer and the furnace form one continuous unit or function as separate units in the continuous firing process. Most industrial furnaces are fiber-lined (low thermal mass), which lowers cost and downtime between firing schedules. 

Pyroelectric detectors depend on the use of a thin slice of ferroelectric material (deuter-ated triglycine sulphate (DTGS), Figure 3.14, is the standard example) - in which the molecules of the organic crystal are naturally aligned with a permanent electric dipole. The thin slab is cut and arranged such that the direction of spontaneous polarisation is normal to the large faces. Typically one surface of the crystal is blackened to enhance thermal absorption, and the entire assembly has very low thermal mass. 

Ochiai, N., K. Sasamoto, H. Kanda, and S. Nakamura. 2006. Fast screening of pesticide multiresidues in aqueous samples by dual stir bar sorptive extraction-thermal desorption-low thermal mass gas chroma-tography-mass spectrometry. J. Chromatogr. A 1130 83-90. 

A non-contact heating method called infrared-mediated temperature control has been employed for PCR. Because the chip material (polyimide) does not absorb IR, only the solution absorbs IR. Therefore, the low thermal mass of the solution allows for fast thermal cycling, and 15 cycles have been achieved in 240 s Amplification of X phage DNA (500 bp) was first conducted at 94°C for 10 s, followed by 15 cycles of 94°C (2 s), 68°C (2 s), 72°C (2 s), then finally stopped at 72°C for 10 s [192],... 

An improved process and equipment for cast PTFE films have been developed, which have considerably higher productivity than the method and equipment described above.14 The process essentially uses a vertical coater with multiple stages. The carrier belt has to be made from a material of low thermal mass which can tolerate repeated exposure to the sintering temperature and has surface properties such that it can be wetted by the dispersion, yet the film can be stripped without being stretched. There are several possible belt materials, but KAPTON H (DuPont) was found to be particularly suitable because of its heat resistance, dimensional stability, and surface characteristics.14 The production speeds used in this process are 3 to 10 m/rnin (9 to 30 I t/min). 

It must have a low thermal mass, a low heat capacity, and efficient heat transfer to permit gaseous heat to heat up the catalyst-carrying washcoat quickly, notably during light-off. 

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