Abstract
The paper describes the results of experimental studies of media as an intermediary in heat exchange taking place in low volume conditions. Their properties predestine them both as a future-proof for transporting and storing heat materials. The paper concerns the current topic related to the miniaturization of cooling heat exchangers. There are many studies in the literature on the phase transition of refrigerants in the flow in pipe minichannels. However, there is a lack of studies devoted to the condensation process in a small volume on the surface of pipe minichannels. The authors proposed a design of a small heat exchanger with a shell-and-tube structure, where the refrigerant condenses on the outer surface of the pipe minichannels cooled from the inside with water. It is a response to the global trend of building highly efficient, miniaturized structures for cooling and air conditioning heat exchangers. Two future-proof, ecological replacements of the CFC refrigerants still present in the installations were used for the experimental research. These are low-pressure fluids HFE 7000 and HFE 7100. The tests were carried out in a wide range of changes in thermal-flow parameters: G = 20–700 kg·m−2s−1, q = 3000–60,000 W·m−2, ts = 40–80 °C.
Highlights
In recent years, there has been an increase in interest in heat transfer in small spaces, both in everyday life, as well as in the economy, technology, and science
It should be noted that this study presents research data in the field of condensation of ecological refrigerants in heat exchangers
The original characteristics of the condensation process were presented in the form of dependencies describing the value of the heat transfer coefficient on the quantities describing the two-phase flow, including the mass flux density level G, temperature difference ts − tw, and heat flux density q
Summary
There has been an increase in interest in heat transfer in small spaces, both in everyday life, as well as in the economy, technology, and science. Kang et al [5] provided an investigation on the influence of the geometrical and thermal-hydraulic parameters of the heat exchanger on heat transfer focused on the steam condensation on the outer surface of a vertical tube in the presence of a non-condensable gas. Li et al [7] investigated the effects of inclination and flow velocity on steam condensation consisting of air on tube bundle external surfaces. The influence of surface enhancement of heat exchanger minichannels on heat transfer was investigated by [13,14]. The authors proposed a design for a small volume shell-and-tube heat exchanger in which the refrigerant condenses on the outer surface of pipe minichannels cooled from the inside by water. It is a response to the global trend of building highly efficient, miniaturized heat exchanger structures for refrigeration and air conditioning installations
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