Vol 51, No 11-12 (2016)

An entropy-statistical analysis of a 7 tons/h capacity small-tonnage CNG plant functioning in a cycle with external nitrogen expansion cooling demonstrated a probable value of the magnitude of thermodynamic perfection of 33%. Application of a rational multi-stage scheme with pre-cooling and the use of a compressor with isothermal efficiency 0.65 and turbine expansion engine with adiabatic efficiency 0.835 are responsible for the decisive contribution to achieving an increase in efficiency.

Values of critical parameters of neon isotopes ²⁰Ne and ²²Ne are calculated. Approximate constants of the van-der-Waals, Berthelot, Dieterici I, and Redlich–Kwong equations of state are obtained. The data allow the adsorption isotherms for the neon isotopes on different adsorbents to be estimated by calculations.

Separation of Ne isotopes by fractionation at 28 K is studied. The number of transfer units in the upper and lower column sections is calculated with various loadings. Experimental characteristics of packed fractionation columns and examples of cascade systems constructed from them are given. A diagram of a cryogenic loop using a throttled high-pressure Ne cycle with intermediate N₂ cooling is presented. The need and capability to create a pressure difference between the columns of the various steps were justified.

Entropy and exergy analyses of losses during mixing of flows and volumes of gas are compared. It is shown that both methods give identical analytical expressions for an ideal gas. However, exergy analysis required more cumbersome mathematical transformations than entropy analysis in order to obtain a final result. An analysis of the expressions for determining the mixing losses always gives a positive result regardless of the temperature of the mixed flows or volumes. The final analytical expressions allow mixing losses to be determined. This is very important for thermodynamic analysis of low-temperature, especially cryogenic cycles.

A method is proposed to improve the robot-assisted radical prostatectomy procedure by using a cooling gas of a controlled temperature. To determine the optimal gas flow rate and temperature values, it is necessary to carry out sample calculations taking into account the particular features of the processes taking place. To solve this problem, a mathematical model for the conjugate problem of convective heat transfer in the operational area and adjacent tissues was developed. The model reflects the unsteady cavity boundaries relating to the placement of the surgical incision. The mathematical model can be implemented in a computer program, which permits optimization of the gas parameters to provide the most favorable surgery conditions for the patient.

The non-uniformity of flow rate distribution between separate devices of the plate-fin heat exchanger units working as a part of air separation plant, exceeding 2% of the nominal value, significantly reduces integral characteristics of the unit. Shortcomings of the method for regulating uniformity of flow rate distribution in the plate-fin heat exchanger units by means of regulating valves are considered. It is suggested to use a different approach allowing to avoid the use of expensive regulating valves and to specify the conditions to provide the required uniformity of flow rate distribution between separate heat exchangers already at the preliminary design stage.

Results from theoretical and experimental investigations of the two-dimensional temperature field of a perforated plate that functions as the basic element of a heat-transfer surface in a matrix heat exchanger are presented. Experimental visualization of the temperature field by means of liquid crystals confirms that the assumptions adopted in the theoretical investigation are correct.

General equations for calculation of the capacity and thermodynamic properties of adsorption methane storage systems were written. Experimental results for methane adsorption on AU-1 adsorbent were analyzed and plotted in the nomograph of capacity and thermodynamic properties of the adsorbent–adsorbate–gas adsorption system. Methods for graphical calculation of the processes occurring in the system were presented.

Similitude criteria of compression processes of real gases in the stages of compressors with dynamic compression are presented. A technique of compiling the thermal and caloric equations of state for gas mixtures and a technique of processing test data obtained in gaseodynamic tests are proposed.

An approximate analytical model is proposed to determine the thickness of the water ice layer on the surface of a straight flat fin as part of heat exchange equipment. This solution could be of interest for use in engineering calculations, in particular, in the design of water coolers, TNT evaporators, LNG gasifiers, etc.

The article is devoted to the development of an information system for the creation of an information environment for an industrial facility, including a large number of sites with complex relationships. All text and graphic information is summarized in a single structure in the development of an integrated information environment of the enterprise. Block diagrams were created of the elements necessary to include the information environment into the automated process of enterprise management.

As a result of experimental research, regimes are determined for mechanized argon-arc welding of copper alloys MNZh5-5, L90, and BrAMts9-2 with steels AB2 and 20, providing preparation of high quality joints during manufacture of chemical and petrochemical engineering objects.

New methods are provided for appraising equipment based on selection of macro- and micro-samples of heavily loaded metal and in contact with a working atmosphere, and subsequent analysis of its properties from experimental data. Use of these approaches makes it possible to appraise equipment without subsequent refurbishment, and to accomplish monitoring in order to evaluate equipment life according to static strength and brittle failure resistance criteria.