Hotspot problem

Poor flow distributions may result in localized dry hotspots which, absent control of the temperature fluctuations, may cause rapid overheating. Temperature and pressure fluctuations, and poor flow distribution, are the main problems that accompany the use of two-phase micro-channels. 

Microwave-mediated reactions can also be easily carried out without solvents (see Section 4.1). The requirements for these dry media reactions are different to those for reactions in solution. As no solvent is involved, the pressure built-up is rather low, and in most instances such reactions are performed under open-vessel conditions. On the other hand, these mixtures can easily be locally overheated, even though the overall bulk temperature may be comparatively low (macroscopic hotspot formation). Stirring and accurate temperature measurement can prove rather difficult within such a matrix, impeding the investigation of certain reaction conditions. Thus, degradation or decomposition of reagents can be a severe problem for these kind of reactions. 

There are several aspects of thermal sensitivity and instability which are important to consider in relation to reactor design. When an exothermic catalytic reaction occurs in a non-isothermal reactor, for example, a small change in coolant temperature may, under certain circumstances, produce undesirable hotspots or regions of high temperature within the reactor. Similarly, it is of central importance to determine whether or not there is likely to be any set of operating conditions which may cause thermal instability in the sense that the reaction may either become extinguished or continue at a higher temperature level as a result of fluctuations in the feed condition. We will briefly examine these problems. 

Overall, the Southeastern Community survey revealed high level of awareness of panhole leak problem among residents of the community. Twenty percent of the households reported actual pinhole leak incidents. The percent of pinhole leak reports was on par with other hotspot areas of corrosion in the U.S., but above the rate of pinhole leak occurrences in non-hotspots (Scardina et al., 2007). The pinhole leak problem was more prevalent in houses built before the 1990s with copper papes installed as the plumbing system. This finding is in an agreement with a Maryland Pinhole Leak Survey conducted by Kleczyk and Bosch in 2004. 

Include in situ tanperature mapping to detect hotspots and identify problem... 

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