Abstract
Water flowing on a sprinkled tube bundle forms three basic modes: It is the Droplet mode (liquid drips from one tube to another), the Jet mode (with an increasing flow rate droplets merge into a column) and the Membrane (Sheet) mode (with further increasing of falling film liquid flow rate columns merge and create sheets between the tubes. With sufficient flow rate sheets merge at this state and the tube bundle is completely covered by a thin liquid film). There are several factors influencing the individual mode types as well as heat transfer. Beside the above mentioned falling film liquid flow rate they are for instance tube diameters, tube pitches in a tube bundle or a physical condition of a falling film liquid. This paper presents a summary of data measured at atmospheric pressure at a tube bundle consisting of copper tubes of 12 milimeters diameter and of the studied tube length one meter. The tubes are positioned horizontally one above another with the tested pitches of 15, 20, 25 and 30 mm and there is a distribution tube placed above them with water flowing out. The thermal gradient of 15–40 has been tested with all pitches where the falling film liquid’s temperature at the inlet of the distribution tube was 15 °C. The liquid was heated during the flow through the exchanger and the temperature of the sprinkled (heater) liquid at the inlet of the exchanger with a constant flow rate about 7.2 litres per minute was 40 °C. The tested flow of the falling film liquid ranged from 1.0 to 13.0 litres per minute. Sequences of 180 exposures have been recorded in partial flow rate stages by thermographic camera with record frequency of 30 Hz which were consequently assessed using the Matlab programme. This paper presents results achieved at the above mentioned pitches and at three types of tube bundle surfaces.
Highlights
Due to decreasing supply of fossil fuels and their increasing price the minimization of energy consumption becomes first priority, followed by saving of primary fuel entering into energy processes which are supposed to achieve maximum efficiency possible, and last but not least using so called renewable sources of energy
This paper focuses on temperature fields at a sprinkled tube bundle consisting of ten copper tubes and their alterations depending on the change of falling film liquid flow rate, type of the tubes' surface and at various tube bundle pitches
This paper presents partial results of research of temperature fields at a sprinkled tube bundle recorded by a thermographic camera
Summary
Due to decreasing supply of fossil fuels and their increasing price the minimization of energy consumption becomes first priority, followed by saving of primary fuel entering into energy processes which are supposed to achieve maximum efficiency possible, and last but not least using so called renewable sources of energy. At a low flow rate the liquid drips from one tube to another in the so called Droplet mode (a). EPJ Web of Conferences until they fill in the whole gap between the tubes That is why this mode is called the Sheet or Membrane mode (c). The second part is testing of sprinkle modes for various tube diameters, tube pitches and tube materials and determination of individual modes' interface This area is mainly researched by [2, 5, 10]. This paper focuses on temperature fields at a sprinkled tube bundle consisting of ten copper tubes and their alterations depending on the change of falling film liquid flow rate, type of the tubes' surface and at various tube bundle pitches. In our case the temperature at a sprinkled tube bundle was determined by means of a thermographic camera
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