Calculation method for twisted heat exchangers used for heat treatment of mining equipment tools

Abstract

Introduction. In modern conditions (depletion of deposits, complication of development conditions, the application of sanctions on the import of equipment, etc.), a special role is played by increasing the resource of equipment used in the mining industry, including processing drilling impact-rotary tools. One of these methods is cryogenic processing of machining tools, as a result of which the hardness and wear resistance of the cutting tool increase several times. For the production of cryogenic substances such as nitrogen, oxygen, methane, etc. in the liquid state, a method is proposed based on the use of adsorption-cryogenic technology implemented through the use of heat exchangers, the development of calculation methods of which is the subject of this article. The purpose of the research is to develop a methodology for calculating heat exchangers used as cold sources for cryogenic surface treatment of mining equipment tools in order to harden it. Research methods. The analysis of the current state of development of technical and technological solutions in the field of development and construction of heat exchangers was carried out through the use of such informal methods as: expert, morphological and factographic. To optimize the modeling calculations of the a priori selected configuration of the heat exchange surface, the method of uniform (blind) search was used. Research results and discussion: 1. In the course of the conducted research, the results of the analysis of the current state of development of technical and technological solutions in the field of development and construction of heat exchangers were obtained. 2. A method for calculating twisted heat exchangers has been developed. 3. It is determined that the presented method of calculating heat exchangers used as cold sources for cryogenic surface treatment of mining equipment tools in order to harden them allows optimization of modeling calculations a priori of the selected configuration of the heat exchange surface. 4. It is established that: heat exchangers with finned pipes should be used when the ratio of the heat transfer coefficient of the flow inside the pipes to the corresponding coefficient in the inter–tube space is 3 ...5 times greater. 5. The use of finned pipes in heat exchangers makes it possible to increase the area of the outer surface of the pipes due to finning, thereby improving the thermal characteristics of heat exchangers, while reducing its weight and size characteristics. 6. It has been revealed that heat exchangers with dense winding are less efficient compared to devices with sparse winding, and heat exchangers with smooth pipes should be used in cases of proximity of the values of the heat transfer coefficient of flows in the tube and inter-tube space. Resume: 1. The analysis of the current state of development of technical and technological solutions in the field of development and construction of heat exchangers was carried out. 2. A method has been developed for calculating heat exchangers used as cold sources for cryogenic surface treatment of mining equipment tools in order to harden them. 3. The developed method of calculating heat exchangers can be used to design heat exchangers consisting of pipes with different surface geometries that are wound onto the core in a spiral, used both in the extractive industries and in the engineering, chemical, oil and gas, rocket and space industries. The further development of the research topic is the optimization of the operating parameters of the heat exchanger according to the criterion of energy efficiency.