Thermal anomalies

Fig. 3. (a) General locations of hydrothemial power plants in the continental United States (6). Power is produced directiy from hydrothermal steam indicated by the steam plume at The Geysers in northern California. At all other locations, hot water resources are utilized for power production. In 1993, a hydrothermal power plant also came on line on the island of Hawaii, (b) Location of The Geysers steam-dominated hydrothermal field (D) in Lake and Sonoma counties, within the boundaries of the Cleadake—Geysers thermal anomaly (B). 

Thermography is a predictive maintenance technique that can be used to monitor the condition of plant machinery, structures and systems. It uses instrumentation designed to monitor the emission of infrared energy, i.e. temperature, to determine their operating condition. By detecting thermal anomalies, i.e. areas that are hotter or colder than they should be, an experienced surveyor can locate and define incipient problems within the plant. 

The most likely reason for the thermal anomaly at the ring edge is that it coincides with an area of increased thermal conductivity in the clays. This area also coincides with an area of decreased hydraulic conductivity (Fig. 3). 

Thermal anomalies ( kinks ) in the properties of water and aqueous solutions appear to be manifestations of higher-order phase transitions in structured elements of water. Some concentration-dependent anomalies are also described and discussed in terms of (a) the occurrence of discrete structural units of water in the unaffected solvent, (b) the possible separate existence of somewhat similarly structured units in the ionic hydration atmospheres, and (c) overlapping of large (but not necessarily structured) hydration atmospheres. 

An understanding of equilibrium phenomena in naturally occurring aqueous systems must, in the final analysis, involve understanding the interaction between solutes and water, both in bulk and in interfacial systems. To achieve this goal, it is reasonable to attempt to describe the structure of water, and when and if this can be achieved, to proceed to the problems of water structure in aqueous solutions and solvent-solute interactions for both electrolytes and nonelectrolytes. This paper is particularly concerned with two aspects of these problems—current views of the structure of water and solute-solvent interactions (primarily ion hydration). It is not possible here to give an exhaustive account of all the current structural models of water instead, we shall describe only those which may concern the nature of some reported thermal anomalies in the properties of water and aqueous solutions. Hence, the discussion begins with a brief presentation of these anomalies, followed by a review of current water structure models, and a discussion of some properties of aqueous electrolyte solutions. Finally, solute-solvent interactions in such solutions are discussed in terms of our present understanding of the structural properties of water. 

The thermal anomalies, which have become known as kinks, have been illustrated in the articles mentioned above. (We shall use the phrases thermal anomalies and kinks interchangeably.) In this section, we show only a few examples to indicate the diversity of aqueous systems in which they occur. We contend that the anomalies are of general occurrence and indicate transitions in the structure of water and can therefore elucidate both the problems of water structure of water itself and solute-solvent interactions. 

In several previous papers, the possible existence of thermal anomalies was suggested on the basis of such properties as the density of water, specific heat, viscosity, dielectric constant, transverse proton spin relaxation time, index of refraction, infrared absorption, and others. Furthermore, based on other published data, we have suggested the existence of kinks in the properties of many aqueous solutions of both electrolytes and nonelectrolytes. Thus, solubility anomalies have been demonstrated repeatedly as have anomalies in such diverse properties as partial molal volumes of the alkali halides, in specific optical rotation for a number of reducing sugars, and in some kinetic data. Anomalies have also been demonstrated in a surface and interfacial properties of aqueous systems ranging from the surface tension of pure water to interfacial tensions (such as between n-hexane or n-decane and water) and in the surface tension and surface potentials of aqueous solutions. Further, anomalies have been observed in solid-water interface properties, such as the zeta potential and other interfacial parameters. 

Before proceeding, a few comments should be made on the authenticity of these anomalies (31, 32). In some cases it is necessary, in order to delineate the existence of a thermal anomaly, to sight down the line on a graph to determine if a more or less abrupt change occurs. Usually, the difficulty is in deciding whether this is, indeed, in the nature of an abrupt change (i.e., taking place over a temperature interval of 2°-3°)... 

We now turn briefly to examples of the thermal anomalies in heterogeneous systems. Shamsul Huq and Lodhi (136) recently determined the distribution of benzoic acid between benzene and water as a function of temperature (Figure 7). The upper set of points refers to the observed distribution coefficient based on the monomer (in the benzene phase). The data points are those obtained by Shamsul Huq and Lodhi straight-line segments have been drawn in by the present author. Obviously, little significance can be attached to a 4 curve such as this which is based on only two points for the higher temperature range, yet, it is... 

Figure 10. Types of thermal anomalies, highly schematized...

The temperatures at which the thermal anomalies are most frequently observed are approximately 15°, 30°, 45°, and 60 °C. within dzl-2 degrees. In other words, the first two kinks may be centered near 13° and 31 °C. while the other kinks may occur near 44° and 62°C. Hence, the unexpected symmetry which would otherwise be implied is not necessarily real, and the enumeration of the 15 degree multiples may primarily serve as a convenient mnemotechnic device for recalling the temperatures of the transitions. Each transition apparently occurs over a fairly narrow temperature interval of about 1-2 degrees on either side of the center of the transition temperature. It is possible and, in fact, likely that more than four kinks exist. We believe an additional kink occurs at temperatures near or above 80°C. Very likely there is also an anomaly near 140°-170°C. 

Implications of Thermal Anomalies for Water Structure Models... 

It is appropriate at this point to make a few comments about the importance of the observed thermal anomalies in connection with the theories of water structure mentioned above. If the reality of the thermal anomalies is accepted, the ultimate theory of water structure must be able to allow for the existence of these anomalies and, hopefully, eventually predict their existence. If the thermal anomalies do indeed manifest higher-order phase transitions, structured elements of a certain size must be present in water. In other words, the uniformists , average structural models must definitely be ruled out. Furthermore, noting that the anomalies tend to center around discrete temperatures and apparently are completed over a few degrees, we concluded that if they do manifest... 

Safford and Naumann (128) have shown that the time-of-flight spectra for 4.6M solutions of KF, KC1, CsCl, NaCl, and LiCl show peaks in the inelastic scattering region which coincide both in frequency and shape with the ice-like (structured) frequencies of pure water. Also, solutions of KSCN, KI, KBr, and NaC104 have lattice frequencies where they are found for water although in these cases apparently with less resolution and less intensity. Even an 18.5-M solution of KSCN showed a similar behavior. We take this to suggest that elements of water structure remain in these solutions (as discussed elsewhere in this paper, where we noted that the thermal anomalies occur at approximately the same temperatures, even for relatively concentrated solutions, as where they occur in pure water see also Ref. 103). 

We have discussed some examples which indicate the existence of thermal anomalies at discrete temperatures in the properties of water and aqueous solutions. From these and earlier studies at least four thermal anomalies seem to occur between the melting and boiling points of water —namely, approximately near 15°, 30°, 45°, and 60°C. Current theories of water structure can be divided into two major groups—namely, the uniformist, average type of structure and the mixture models. Most of the available experimental evidence points to the correctness of the mixture models. Among these the clathrate models and/or the cluster models seem to be the most probable. Most likely, the size of these cages or clusters range from, say 20 to 100 molecules at room tempera-... 

Keywords Thermography, fibre optic, thermal anomaly, leak, natural gas, directional... 

The picture below shows two examples of the thermal effect determined by a leak the thermal anomaly on the ground recorded by an helicopter, and the extreme effect of a leak of a block valve (Figure 2 and Figure 3, respectively). 

Figure 2 Examples of thermal effects determined by gas leaks the thermal anomaly from an underground leak.

Fig. 5.19. Steady-state conductive thermal anomalies associated with insulating clathrate lens on Mars...

Spencer JR, Tamppari LK, Martin TZ, Travis LD (1999) Temperatures on Europa from Galileo photopolarimeter-radiometer nighttime thermal anomalies. Science 284 1514-1516... 

The above account has provided sufficient background for analysis of the properties of aqueous solutions. The analysis has been restricted to bulk water the properties of water near interfaces, including biological surfaces, is very interesting but outside the scope of this review. It should be noted, however, that the properties of vicinal water differ from those of bulk water, these differences being important in biological systems (Drost-Hansen, 1972 1973). Thermal anomalies in the properties of water also seem explicable in terms of interfacial phenomena (Drost-Hansen, 1968). 

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