Förstudie till energioptimering av tankdrift i uppvärmda oljetankar genom CFD-modellering

Abstract

Proposals to energy saving measures during oil storage and handling are presented in this report. The proposals are based on measurements and evaluations of operating and storage conditions in non-stirred oil storage tank equipped with hot water coils. Detailed knowledge about flow and temperature fields in both tank and heating coils has rendered possible by modelling the system in CFD. A model has been created by gradually simplifications in the geometry of the tank. The model has been able to render a solution despite limited computer capacity, a solution which correlated with measurement data. The investigated tank has proved to have large energy losses, about 65 % of the supplied heat, which arises from the inferior insulation. Theoretical calculations have been carried out at different insulation thicknesses and a moderately improved insulation can reduce the energy losses to about 10 %. The results from the simulations have shown that the hot water coils are poorly dimensioned in order to enable a quick heating of the oil. A large part of the heat transfer area of the coils is not utilized due to a quick temperature drop of the hot water which is caused by a low flow rate inside the coils. The investigated tank is shown to provide satisfactory spontaneous mixing, which leads to the conclusion that no mixing equipment is necessary. The measurements have indicated that the regulation of the hot water flow is insufficient. There are several problems that should be further investigated and attended to. Examples of these are the response time of the system, unstable hot water flow and high energy consumption in an empty tank. This report is the basis for future decisions about measures that could be taken in order to reduce the energy consumption during oil storage and handling.