Research on the Selection of Low Temperature Aluminum Heat Pipe Working Fluid

Abstract

Heat pipe is a kind of high efficient heat transfer element, which is widely used in all aspects of life, especially in solar energy technology and permafrost. This research focuses mainly on the low temperature gravity heat pipe working fluid and discusses the influence of refrigerant thermos-physical characteristics to heat transfer. It is shown that the aluminum heat pipe optimal refrigerant is acetone. Introduction Heat pipe is a heat transfer components which relies on its phase change to achieve the effect. Due to its high thermal conductivity, excellent isothermal advantages, it is widely used in aerospace and the modern industrial manufacturing field, especially all kinds of heat exchanger and the cooler [1]. There are two types of heat pipe mainly. One is the classic heat pipe, and the other is the gravity heat pipe [2]. The working fluid in the heat pipe absorbs heat from evaporation section and rises to condensation section to emit heat, and then returns to evaporation section by its own gravity. Since the gravity heat pipe is simple in structure, easy to manufacture and low cost and excellent heat transfer performance, it is widely used in the field of heat exchange [3]. The tube shell of the heat pipe works as the role of isolating the working fluid and the environment, so it must be sealed. Because of the near vacuum environment in the pipe, it must withstand the pressure difference between the internal and the external. At the same time, it also cannot react with the working fluid. [4]. The selection of heat pipe working medium The heat pipe discussed in this paper is made of aluminum alloy. The selection of the working fluids mainly considers the following questions: (1) The working fluid should be compatible with the shell material. (2) The saturation vapor pressure of the working fluid should be suitable at the heat pipe working temperature. (3)The condensation point and boiling point of the working fluid should be in accordance with the working temperature range of the heat pipe. (4)The working fluid should have good characteristics of thermal stability, economy, safety and environmental protection. (5) Working fluid should have good thermal physical properties [5]. The working fluid should be compatible with the shell material. The commonly used working fluids of the heat pipe and the compatible shell materials at different operating temperatures are shown in Table 1 [6]. 2nd Workshop on Advanced Research and Technology in Industry Applications (WARTIA 2016) © 2016. The authors Published by Atlantis Press 1278 Table 1 Common working fluid of heat pipe Species Working fluid Working temperature/°C Compatible material Low temperature heat pipe Ammonia R-21(CHCl2F) R-11(CCl3F) -60-100 -40-100 -40-120 Aluminum, Stainless steel, Low-carbon steel Aluminum, iron Aluminum, Stainless steel, Copper Normal temperature heat pipe Hexane Acetone Ethanol Methanol