Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.
In the paper an experimental analysis of passive heat transfer intensification technique employed in the case of plate heat exchanger is presented. The passive intensification was obtained by a modification of the heat transfer surface. The roughness of surface was increased by a usage of glass micro- beads. Single-phase convective heat transfer in the water-water system was studied. The experiment was accomplished in two stages. In the first stage the commercial plate heat exchanger was investigated, while in the second one – the identical heat exchanger but with the modified heat transfer surface. The direct comparison of thermal and flow characteristics between both devices was possible due to the assurance of equivalent conditions during the experiment. Equivalent conditions mean the same volumetric flow rates and the same media’s temperatures at the inlet of heat exchangers in the corresponding measurements’ series. Due to this the systematic experimental data show that larger roughness of heat transfer surface leads to an increase of heat transfer coefficient on the side of cooling water (increase by about 30 ÷ 35%) and simultaneously to an increase of flow resistance (up to 30% when the volumetric flow rate is equal to 500 l/h). On the side of heating water it was found that the heat transfer coefficient increased by about 25%, while the flow resistance by about 22% (the volumetric flow rate of 500 l/h).