河南 治

Herein, the heat transfer characteristics of a shear-driven liquid film flow, which is a liquid film flow with co-current gas flow, in a rectangular channel were experimentally investigated. An experimental apparatus was fabricated to observe the liquid film behavior and evaluate the local heat transfer coefficient. The rectangular channel had a height of 2 mm and a width of 10 mm, and its heating surface was a horizontal flat plate with 10 mm in width and 100 mm in length. The experiments were conducted by varying the heat flux and gas Reynolds number by maintaining the liquid film Reynolds number constant. Based on the experimental results, the liquid film behavior was classified into six patterns: bubble flow, annular flow, annular flow with drying and wetting, annular flow with rivulet, stratified flow, and annular flow with dry area. Although the local heat transfer coefficient in the shear-driven liquid film flow decreased due to the expansion of dry area caused by the rupture of liquid film compared with that of flow boiling, the local heat transfer coefficient did not decrease considerably. This indicated that considerably high heat flux occurred in the wet area of the rivulet flow due to decreased liquid film thickness.

Abstract This paper presents an experimental investigation of local heat transfer characteristics of single-phase flow in a plate heat exchanger (PHE). The local heat transfer coefficient is evaluated using a test section with PHE geometry for measuring wall temperature distribution. The test section of 1.5 mm thickness is employed to consider the heat conduction effect of the heat transfer plate. The results indicated that the local heat transfer coefficient is influenced by the development of the thermal boundary layer along the flow direction and the maldistribution of water flows along both the direction perpendicular to the flow and the stacking direction. The harmonic mean heat transfer coefficient calculated by the measured local heat transfer coefficient agrees with the average heat transfer coefficient evaluated by the modified Wilson plot method within ±25% and within ±16% for the hot side and the cold side, respectively.