The research project deals with different techniques to improve evaporation heat transfer surfaces for heat exchangers to be used in a variety of industrial applications in the lower temperature range (<<150 C). The different approaches to be investigated are expected to lead to heat exchangers with improved performance and reduced size, weight and price.
The research project deals with different techniques to improve evaporation heat transfer surfaces for heat exchangers to be used in a variety of industrial applications in the lower temperature range (less than 150 C). Heat transfer leading to evaporation is applied in a large variety of industrial processes and domestic appliances. An improvement in their performance can therefore lead to large energy savings.
A number of enhanced surfaces have been investigated, and potentially satisfactory cost effective techniques for enhancing evaporation have been found. Active enhancement by rotation has been shown to improve heat transfer coefficients by 30 to 80% both in evaporation and condensation.
Heat transfer leading to evaporation is applied in a large variety of industrial processes and domestic appliances. An improvement in their performance can therefore lead to large energy savings. In the development of improved evaporation heat transfer surfaces, a number of options will be explored.
Evaporation heat transfer from structured surfaces will be investigated by IKE and NEL with support from TMX, CAL GAVIN and ICI. Planar samples with micro-cavity structure and cylindrical tubes with helically wrapped fine wire structures will be designed and tested at low temperatures (x C) and pressures ( bar). The experimental data will be compared with a theoretical model to be developed by NEL.
Evaporation heat transfer from covered surfaces (evaporation in a narrow gap between two surfaces, one of which is heated) will be tested. GRETh will investigate planar surfaces; parameters such as gap width, orientation of the two plates, material of the plates, roughness of the plates, will be varied. Testing will take place at temperatures up to 100 C and at atmospheric pressure. NEL will carry out similar experiments for tubes and develop a theoretical model for evaporation from both covered plates and tubes. Evaporation heat transfer from smooth and roughened vertical narrow channels will be experimentally investigated by ETU; a theoretical model will also be made and evaluated.
CRES and NTU with support of ICI will explore experimentally and theoretically the field of evaporation heat transfer from rotating (100-1000 rpm) smooth and structured surfaces (rotation is expected to enhance heat transfer).
The participation of four industrial companies: TMX (tube manufacturer), CAL GAVIN (producer of tubes and special heat exchanger surfaces), CIAT (manufacturer of heat exchangers) and ICI (user of heat exchangers) ensures an industrial input in this project.
An extension of the above activities allows more detailed investigation of several aspects of enhanced evaporation surfaces. This covers different surface geometries, additional operating parameters, such as temperature and surface conditions and the extended use of flow visualisation techniques to support the analytical models developed in the previous part of the project.
Funding SchemeCSC - Cost-sharing contracts
B12 OXN Birmingham
19009 Pikermi Attiki
EH14 4AS Edinburgh
G75 0QU East Kilbride
NE2 4AA Newcastle Upon Tyne