Manufacturing of a 3d Finned Tube for Enhanced Boiling and Condensation Using Rolling-cutting-extruding Composite Forming

3D finned tube is a high efficient enhanced heat transfer element and its manufacturing has always been the focus of research’s attention. It is a challenging job to manufacture a 3D finned tube that can enhance both boiling and condensation because the enhanced boiling structure is completely different from the enhanced condensation structure due to different heat transfer enhancement mechanisms. An innovative rolling-cutting-extruding composite forming method is developed to realize the manufacture of a staggered stepped lattice finned tube (SLFT) with helical fins, two layers of staggered stepped lattice fins and inner helical threads, which can enhance boiling as well as condensation heat transfer. The three skewed rolling-cutting tools specially designed are uniformly distributed around the base tube and the kinematics conditions of rolling-cutting-extruding process is analyzed. The relative plunge depth of a rolling blade can’t exceed a certain limit value and the feeding angle has to be equal to the helix angle of outer helical fin. According to the kinematic conditions, the parameters of the rolling-cutting tool are selected and processing experiments of the SLFT are conducted.

Researche influence of holding time on the rheological properties of alumina slips containing with dispersing and hardening additives and the properties of corundum ceramics samples which made from them

The researches influence of holding time on the rheological properties of the slips and the properties of corundum ceramics samples based on alumina of the MARTOXID MR70 brand with dispersing and hardening additives (for casting thin-walled products) and only with the dispersing additive (for casting of thick-walled products) which made of them were carried out. The holding time has a significant effect on the rheological properties of the slips were established. The destruction of aggregates in initial alumina on particles were begining with increasing the holding time the slips to 24 hours as a result the dynamic viscosity of these slips decreases and reaches a minimum value. In the slips with combined additive (dispersing and hardening) with increasing the holding time more than 24 hours beginning the formation of a coagulation-condensation structure. In the slip with only a dispersing additive and in the slips without additive beginning the formation of a coagulation structure the dynamic viscosity of the slips increases and this process does not end at 672 hours. However, with a little mechanical mixing in all three slips their structure are fragile and easily almost completely destroyed and such slips are suitable for making quality products from them. The samples which made from the slips after a holding time of 24 hours and 720 hours have practically the same properties, so the increasing the holding time for more than 24 hours does not affect the properties of the samples. For making quality products the fresh slips are also suitable and it is necessary to choose the holding time of slips according to the size and configuration of products, their service conditions and production volumes. According to the electronicmicroscopic studies the formation a gel-like substance that envelops alumina particles and thereby prevents its settling in the slip which contains the hardening additive.

Potassium uranyl borate 3D framework compound resulted from temperature directed hydroborate condensation: structure, spectroscopy, and dissolution studies

A potassium uranyl borate K[(UO2)B6O10(OH)] (KUBO-4) framework structure was synthesized and characterized with a variety of measurements.

Modeling of Reliability for Anti-Condensation Wall System in Underground Engineering Based on Markov Process

This paper introduces the basic principle and structure of the Anti-condensation wall system in underground engineering, sets up the modeling of reliability for Anti-condensation wall system based on Markov process, which contains models of reliability for 5 different series repairable Anti-condensation unit and Parallel Anti-condensation structure. By analyzing the availability of example, this paper can provide some references to rational repair plan.