from the magnetic studies of either the Ti or the Zr.Finally, we were interested in what happened to the magnetic susceptibility of Zr as the hydrogen began to enter the metal. Thus, starting with pure, ductile Zr, we began measuring the susceptibility as a function of temperature, while the specimen was exposed to an atmosphere of hydrogen. Figure 5 shows the results. Naturally, at low temperatures the values are exactly those of the pure metal. At 900 0 K the specimen began slowly to take on hydrogen and the susceptibility began to increase. Beyond the A-point the specimen did not appear to gain or lose any appreciable quantity of hydrogen, and it is apparent that the susceptibility does not resemble that which the pure metal Zr shows in its high temperature phase. Comparing the A-point with that found for pure Zr in reference 4 (here represented in dashed lines), it is seen that the transition occurs about 200 0 lower. The actual structure change is, however, entirely different, which is rather surprising. The measured curve in Fig. 5 is not reversible with temperature (unless one also pumps out the hydrogen) as the new phase is preserved on lowering the temperature.

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The Lockhart-Martinelli type of approach has been extended for the flow of a gas-non-Newtonian liquid (power law type) two-phase flow system in helical coils. Experimental work on flow pattern, holdup, and isothermal pressure drop at 30 °C was carried out in four helical coils having coil curvature ratios of 0.0100, 0.0198, 0.0476, and 0.0695 with air-water and air with each of the aqueous polymer solutions of 0.3 and 0.5 % (w/w) of sodium alginate and 0.5 and 1.0% of sodium carboxymethyl cellulose as test liquids. Suitable design correlations are proposed to predict the holdup and two-phase pressure drop in helical coils.

Investigations have been carried out on heat transfer and frictional characteristics of five spirally corrugated tubes of one to four corrugation starts, having the same helix angle, but of varying geometrical aspect ratios, for the turbulent flow of water and 50 percent glycerol. The thermal performance of these tubes was found to be superior compared to a smooth tube. Friction factors and heat transfer coefficients in these rough tubes were analysed on the basis of momentum and heat transfer analogy, and the correlation obtained was tested with the present data and also the published results of previous investigators. Performance evaluation criteria were used for the quantitative demonstration of the benefits offered by these spirally corrugated tubes for heat exchanger applications.