With the object of improving the efficiency of a thermo-compression system, the subject was studied from the view point of the second law of thermodynamics. As an example, irreversible entropy increase was calculated, by entropy balance, in the process of salt evaporation, so as to make clear that thermodynamical efficiency which is defined as the ratio of reversible work of salt evaporation to available energy, required for recompression of vapors, could be improved by reducing the irreversible losses in the process.

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The author calculated the steam flow rates at the throat of a diffuser, from the experimental data already made public by himself, using the momentum theory.
(1) Steam Injector for Feeding Boiler Water
It has been made clear by the momentum theory that the larger the quantity of steam going through the diffuser throat, the higher the delivery pressure. But when the quantity of steam injected in the diffuser increases, it may happen that the delivery pressure decreases. Accordingly, we must design the injector taking into calculation the ratio of steam quantities at the diffuser throat to the steam consumption of the steam injector as shown in Fig. 10.
(2) Steam Ejector.
When the suction water has more vacuum, its magnitude decreases, the diffuser being in need of more steam flow rate at the throat. For the purpose of increasing the magnitude of the suction water, the steam flow rate at the throat of the diffuser must be so arranged as to have a certain value, (proper for each type of the steam ejector) which, in the case of the steam ejector presented in Fig. 1, being 10% under the condition of 0-30cmHg vacuum of suction water (Fig. 6)
As shown in the author's experiments made public before, the maximum efficiency occurs at the value of L=4.5mm for the 20-30cmHg vauum of suction water.
At the value of L<4.5, the mixing is not in such a condition as to deliver more magnitude to the suction water.
At the value of L>4.5, the mixing loss becomes so great that the efficiency decreases, although the steam flow rate through the diffuser throat remains constant owing to the slow heat exchange between steam and unsaturated water heated to elevated temperature by the steam.

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A method of calculating the maximum performance of jet pumps or ejectors is presented by eqs. (26), (27) and (28) or (29). These equations have been introduced by a one-dimensional analysis which contains some assumptions; namely, ideal gas law can be applied to primary and secondary gases, the mixing process of both the gases follows eq. (13), the flow is adiabatic to the outside of the ejector, and both the friction loss factor, ζ, and the ratio of specific heats, γ, are constant.
Eq. (28) is to be used for the design of jet pumps, and eq. (29) for ejectors.
Several diagrams, Fig. 2-12, are drawn for the designers' convenience. The calculations would be simplified by using these diagrams.
The comparisons between the calculation results and the experimental data have been made with some examples. Fairly good agreements are recognized as shown in Figs. 13, 14, 15.

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