Effects of Absolute Pressure on RPTs

As will be described later in this section, for several types of small-scale tests where RFTs would be expected, an increase in the absolute system pressure had a profound effect in suppressing such incidents. As often noted in previous sections, one current theory to explain RPTs invokes the concept of the colder liquid attaining its superheat-limit temperature and nucleating spontaneously. In an attempt to explain the pressure effect on the superheating model, a brief analysis is presented on the dynamics of bubble growth and how this process is affected by pressure. The analysis is due largely to the work of Henry and Fauske, as attested to by the literature citations. 

Let us consider a superheated liquid which has attained the limit of superheat and a vapor embryo forms in equilibrium with the liquid. The bubble radius is ro, the pressure in the bulk liquid is Pq, and the temperature is Tq. Assume the liquid is pure. 

The vapor embryo, or bubble, is in unstable equilibrium and will either collapse or grow. We are only interested in those that follow the latter path. The chemical criteria of equilibrium between the bubble and liquid state that the temperature and chemical potential of the material in the bubble are equal to those in the superheated liquid, i.e.. 

The latter equality can be related to the bubble pressure P and the liquid 

The exponential term in Eq. (6) is normally only slightly less than unity (Po Pvp) and is often neglected. For the discussion given below, we will also follow this procedure. 

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