Development of a resource-saving technology of production of strip-type profiles by drawing in roller dies using dummy passes

The rolling-drawing process is used in the production of a large number of shaped profiles of complex configuration, including thin-walled, strip and periodic section profiles. This process, in comparison with drawing in monolithic dies, allows to reduce energy costs by 20–40 %, to increase deformation in one pass to 40–50 %, to reduce the number of preparatory operations (heat treatment, pickling), to exclude the use of expensive lubricants for drawing. Compared to the production of profiles by the method of cold rolling, the rolling-die process has a higher technological flexibility, does not require significant capital investments when organizing the production of precise profiles. At the same time, due to the presence of tensile stresses at the edges of the profile, which can cause their destruction, the assortment of strip-type profiles produced by this method was previously limited to readymade profiles with a ratio of width to height of no more than two. The authors of this work have previously developed a technology for the production of crimped steel strip with a width-to-height ratio of more than 10 by the rolling-drawing method. However, the developed calibration provides for a large number of transitions, complicates the organization of the production of strip profiles of a wide range of sizes, especially in the production of low-tonnage batches. To decrease the number of transitions, the use of dummy paases was proposed. It was shown that this will make it possible to increase the width-to-height ratio of strip-type profiles to 20, and, accordingly, reduce the production cost. The proposed technology for the production of strip-type profiles by the method of drawing in roller dies using dummy passes will allow to comprehensively solve the problem of providing machine-building and instrument-making enterprises by especially precise profiles of a wide range of sizes.

Optimal Shape Selection of Heat Exchangers Surfaces during Convective Heat Transfer

The article contains the results of a research in constructing of modern heat exchangers form of heat exchanging surfaces and modes of heat media flux, providing minimum area (size) of heat exchanging apparatus. Decreasing of heat-transferring area is achieved by using different techniques of intensification of convective heat exchange. Intensification of the heat exchange is accompanied by increasing of energy consumption for pumping the coolant. It is concluded that under the conditions of turbulent flow, the transport mechanism does not strongly depend on the shape of the perturbations introduced into the flow, while the tendency to approach the dependences is common to the curves for the considered surfaces, and the experimental data obtained on pipes with a periodic section of the flow cross-section along the length. Using surfaces creating channels with a greater coefficient of hydraulic resistance when creating a compact heat exchangers, which corresponds to surfaces for which the principle of trans-verse flow is realized.

A Parametric Study of the Effect of Wall-Shape on Laminar Flow in Corrugated Pipes

In this paper we study the effect of wall-shape on laminar flow in corrugated pipes. The main objectives of this paper are to characterize how the flow rate varies with wall-shape, and to identify which shapes enhance the flow rate. We conduct our study by numerically solving the Navier-Stokes equations for a periodic section of the pipe. The numerical model is validated with experimental data on the pressure drop and friction factor. The effect of wall-shape is studied by considering a family of periodic pipes, in which the wall-shape is characterized by the amplitude, and the ratio between the lengths of expansion and contraction of a periodic section. We study the effect that varying these parameters has on the flow. We show that for small Reynolds numbers, a symmetric shape yields a higher flow rate than an asymmetric shape. For large Reynolds numbers, a configuration with a large expansion region, followed by a short contraction region, performs better. We show that when the amplitude is fixed, there exists an optimal ratio of expansion/contraction which maximizes the flow rate. The flow rate can be increased by 8%, for a geometry with small period; in the case of a geometry with large period, the flow rate increases by 35%, for large Reynolds number, and even 120% for small Reynolds numbers.