Improving the Thermal Efficiency of Gasket Plate Heat Exchangers Used in Vegetable Oil Processing

The study investigates, by calculations, some ways to improve the thermal efficiency of plate heat exchangers used in the vegetable oil processing industry. The performance of these heat exchangers is limited by the heat transfer rate on the oil side and by the low thermal conductivity of the plate material. The study starts from a base case with vegetable oils cooled with water in plate heat exchangers, all with chevron angle 30o and different number of channels and plate transfer area. The change of one geometrical characteristic of the plates, namely the chevron angle, from 30o to 45o then to 60o, led to important increasing of the overall heat transfer coefficients, by 16.0 % when changing from 30o to 45o and by 28.1% on average when increasing the angle from 45o to 60o. This is an important increase accompanied by the rise of the pressure drops in circuits, but the values are acceptable since not exceeding 1 bar on oil circuit and 1.4 bar on cold fluid circuit, respectively. The use of Fe3O4–SiO2/Water hybrid nanofluids with concentration 0.5% v/v, 0,75% v/v and 1% v/v were investigated, to replace the cooling water. An increase by 2.2% on average was noticed when using the 1% v/v nanofluid comparatively with water, which is not large but adds to the chevron angle increasing. A supplementary 2.6% increase is possible by changing the manufacture material for plates with aluminum alloy 6060, also adding to the performances obtained by previous modifications. The total increase for all the set of modification can increase the performance by 34.2% on average. Thus, for the design of new PHEs, the miniaturization of the equipment becomes possible.