The study of heart transfer during boiling process of organic fluid

Abstract

The paper considers the problem of studying heat transfer inside the pipes of an evaporator of an organic Rankine cycle unit during boiling of an organic heat transfer fluid. Recently, the organic Rankine cycle units are increasingly used in various industries for the utilization of low-grade heat of various processing units. One of the main elements of these units is the evaporator in which vaporization takes place. The evaporator is a concurrent boiler. One of the problems in the design of concurrent boilers is the lack of knowledge of heat transfer during the process of boiling fluid. This paper presents a study of the heat transfer process inside a concurrent boiler. This study is carried out by creating a model of boiling organic fluid in the pipes of a concurrent boiler. The boiling model was implemented in the Ansys fluent software package. Using this model, the values of the heat transfer coefficient were obtained at each point of the evaporator pipe under consideration. After obtaining the values, the dependence of the heat transfer coefficient on the length of the pipe was analyzed. As a result of the analysis, it was determined that starting from the point of 0.6 m, the heat transfer coefficient sharply decreases by 3.5 times. The value of the heat transfer coefficient after the decrease section is at the level of 125 W/m2K over the entire length of the pipe. Thus, it was determined that under given initial conditions, with a pipe length of more than 1 m, heat transfer ceases to be effective.