Heat sink effect

Agitator failure either due to electrical or mechanical failure could result in loss of system control and "hot spots" in the reactor. In suspension systems loss of agitation could negate much of the "heat sink" effect as the immiscible phases separate and stratify. 

Disadvantages are the dimensional restrictions (only simple shapes can be sintered) low capacity the loss of the heads (clipped parts) which did not obtain the temperature due to the heat sink effect of the contacts. 

Cooling ejfect (heat sink effect) flame retardants that decompose in endothermic reactions are able to cool the fire environment and therefore to slow down the reaction pathway. These additives are usually hydrated minerals or metal hydroxide fillers. 

A second type of filler, called active flame-retardant fillers, is considered more effective than inert particles. Its operating mode involves not only fuel dilution, but also an additional cooling or heat sink effect. Indeed, these compounds are able to decompose at elevated temperature via eudothermic reactions which absorb energy and tend to slow down thermal degradation of the composite. Besides, inert gases (water vapour, carbou dioxide) are formed by the filler decomposition and contribute to diluting the concentration of combustible volatiles in the flame-environment. Common active flame retardant fillers are ... 

The dressing of the through-hole and Cu pad is the next step. An excess of solder remaining in the hole will hinder lead insertion for the new component. It is difficult to extract physically all solder residue form inside a hole, even at modest aspect ratios (board thickness-to-hole diameter). This difficulty is further compounded with thicker,multilayer circuit boards because the soldering iron tip cannot compensate for the large thermal mass of the laminate or the heat-sink effects caused by the internal Cu layers. Finally, it is often necessary to contact the Cu pads of the circuit board briefly, with the braid between the pad and the tip, to remove any excessive solder residue. 

Thicker, multilayer boards are more difficult to solder due to their greater thermal mass and the heat-sink effects of the internal layers. Preheating of the drcuit board can be used to augment the soldering iron heat source. T5q)ically, the circuit board is heated to a temperature in the range of 100 to 125°C. However, because the preheating step is applied to a full-up... 

For all thermal ablations it is important to be aware of the effects of blood flow because all these methods are negatively influenced by the blood flow as the heat is removed before achieving complete tumor ablation. These cooling effects are described with the term heat sink effect . The heat sink effect is due to the tumor-adjacent visible (>1 mm diameter) blood vessels when ablated tissues are heated. 

More critical are unintentional burns to anatomical structures within the vicinity (distance less than 1 cm) of the treated lesion. A thorough planning of the access route and final electrode placement may help to avoid damage of such structures, for example the gallbladder or the renal calices (Ogan et al. 2002 Yamakado et al. 2003). In clinical reality vascular heat sink effects, the peritoneal surfaces and the... 

One of the important issues was to evaluate whether the heat sink effect applies to lung in this same way as it does to liver (Lu et al. 2002). 

Using an in vivo sheep model we macroscopically evaluated the effect of vessel size on the radiofrequency lesion creation in the lung with respect to the potential for a perfusion-mediated heat-sink effect and vascular injury, with histological correlation and assessing the type and severity of complications. 

Gross and histological analysis of all radiofrequency lesions was performed to determine the extent of both vascular injury and the heat sink effect and to assess for complications. 

In the acute, subacute, and chronic setting, the heat sink effect, indicated by invagination of the tissue between the vessel and the ablated region, is only observed in vessels greater than 3 mm in diameter. Thrombus is seen in 20% of vessels smaller than 3 mm. On histopathology, vessels smaller than 3 mm show at least partial vessel wall injury, characterized by endothelial cell necrosis and luminal thrombus. In vessels greater than 3 mm the extent of vessel wall injury decreases with increasing vessel diameter (Steinke et al. 2005). 

Lu DS, Raman SS, Vodopich DJ, Wang M, Sayre J, Lassman C (2002) Effect of vessel size on creation of hepatic radiofrequency lesions in pigs assessment of the heat sink effect. AJR Am J Roentgenol 178(1) 47-51 Luderitz B (2003) Historical perspectives on interventional electrophysiology. J Interv Card Electrophysiol 9(2) 75-83... 

Besides the use of melamine as a component of intumescent systems it has also been advocated as a flame retardant in its own right. It has the advantages of being inexpensive, readily dispersible in most thermoplastics and is commercially available in grades of varying particle size. The flame retardant effect is largely due to a combination of heat sink effects and vapour phase dilution effects so in these respects it has some similarities with the hydrated filler flame retardants. 

Cavities in parts introduce discontinuities in the flow path of heat through the wall thus increasing the insulating capacity. Anyway, the heat-sink effect caused reduced... 

A wide range of micro-structures can be developed, based on cooling rates, and these microstructures are dependent on energy input, preheat, metal thickness (heat-sink effects), weld bead size, and reheating effects due to multi-pass welding. 

Boron compounds used as fire retardants may also owe much of their effectiveness to such heat sink effects due to dehydration or, for ammonium salts, loss of ammonia. A second mode of action may be connected with the formation of a glassy layer at the surface. Boron compounds, however, cannot be regarded as inert, since there is evidence of borate ester formation with cellulose, for example. The ultimate effect is increased char formation, which impedes heat transfer. 

A method for estimating the true compound temperature is illustrated in Figure 10.2, which shows the temperature recorded by thermocouple, the stock temperature, J, measured directly by a probe and the stock temperatures estimated from the temperature difference, - 2> of other runs. These - 2 values were added to the t 2-curve of this run to obtain the J-curve. It was assumed that the temperature difference between the curve and the 2-curve increased smoothly with the rise of the stock temperature. This is based on the previously stated interpretation that the temperature difference, - 2> is caused by the heat-sink effect on the thermocouple. Such an effect is expected to increase with rising stock temperature. The fact that the pattern of 2-curves is very reproducible means that the temperature non-uniformity within the compound is not registered by the thermocouple. This is probably due to the time lag of the thermocouple, which averages out the temperature non-uniformity of the very rapidly sweeping compound. 

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