Special Types of Heat Exchangers
Abstract
The article describes the results of experimental research of a new type of heat exchangers in which the heat transfer surface consists of smooth polypropylene fibres with the outer fibre diameter of 0.5 mm and the total heat transfer surface area of 0.14 m 2 . The research output is the information on the value of the heat transfer coefficient, exchanger heat capacity and pressure loss. This type of heat exchangers is contemplated for applications in areas where high chemical resistance of the equipment is required, as well as a relatively low weight and price and excellent resistance to the formation of wall deposits.
Keywords
Download Options
Introduction
Within the new approach to the heat exchanger structure, the heat transfer surface consists of polypropylene fibres with an absolutely smooth and gas-proof surface or a surface with porous walls. The polypropylene fibres, which form plastic capillaries of exchangers, currently seem to be a very simple and cost-efficient component to be used in the structure of heat exchangers. Table 1 contains the technical parameters of a bundle of plastic capillaries which has been subjected to the experimental investigation. The purpose of the investigation was to identify the cooling capacity of the exchanger, but primarily the heat transfer coefficient of the transfer of heat from water in a polypropylene capillary to water in the surrounding environment.
Conclusion
At present, real technical operations lack a heat exchanger made of polypropylene which would offer strength and heattransfer properties similar to those of metal exchangers while exhibiting excellent chemical resistance, relatively low weight and price, and resistance to the formation of wall deposits [3, 4].
The current increased interest in the use of propylene fibres for heat-transfer surfaces may be explained mainly by chemical stability of such heat-transfer surfaces, their resistance to corrosion and self-cleaning capacity. This facilitates the use of fibre bundles in operations where the use of conventional exchangers is impossible. Therefore, it provides a possibility to recover the residual thermal energy for example from waste waters. Such considerations are in favour of the use of exchangers made of polypropylene fibres, which will only be possible under certain conditions. It is also obvious that the use of such exchangers will be limited by their resistance to heat and pressure, or by their strength. Very thin fibres require proper balance between mechanical and operating parameters. Designing such exchangers require the application of the correct correlation between the fibre wall thickness, maximum pressure loss and heat transfer coefficient.