Measuring the Average Volumetric Heat Transfer Coefficient of a Liquid-Liquid-Vapour Direct Contact Heat Exchanger

Analogies between the transient momentum and energy equations of particles

An investigation of dispersed liquid–liquid two-phase turbulent swirling flow in a horizontal pipe is conducted using a particle tracking velocimetry (PTV) technique and a shadow image technique (SIT). Silicone oil with a low specific gravity is used as immiscible droplets. A swirling motion is given to the main flow by an impeller installed in the pipe. Fluorescent tracer particles are applied to flow visualization. Red/green/blue components extracted from color images taken with a digital color CCD camera are used to simultaneously estimate the liquid and droplet velocity vectors. Under a relatively low swirl motion, a large number of droplets with low specific gravity tend to accumulate in the central region of the pipe. With increasing droplet volume fraction, the liquid turbulence intensity in the axial direction increases while that in the wall-normal direction decreases in the central region of the pipe. In addition, the turbulence modification in the present flow is strongly dependent on the droplet Reynolds number; however, the interaction of droplet-induced turbulences is significant due to vortex shedding, particularly at high droplet Reynolds numbers and higher droplet volume fraction.

PTV investigation of phase interaction in dispersed liquid-liquid two-phase turbulent swirling flow

Experimental measurements and theoretical prediction for the volumetric heat transfer coefficient of a three-phase direct contact condenser

An experimental investigation for the time dependent volumetric heat transfer coefficient of the bubbles type, three-phase direct contact condenser has been carried out utilising a short column (70 cm in total height and 4 cm inner diameter). A 47 cm active height was chosen with five different mass flow rate ratios and three different initial dispersed phase temperatures. Vapour pentane and constant temperature tap water as dispersed and continuous phases were implemented. The results showed that the volumetric heat transfer coefficient decreases with increased time until it almost reaches its steady state conditions. A sharp decrease in the volumetric heat transfer coefficient was found at the beginning of the operation and, diminished over a short time interval. Furthermore, a positive effect of the mass flow rate ratios on the volumetric heat transfer coefficient was noted and this was more pronounced at the beginning of the operation. On the other hand, the volumetric heat transfer coefficient decreased with an increase in the continuous phase mass flow rate and there was no considerable effect of the initial dispersed phase temperatures, which confirms that latent heat transfer is dominant in the process.

Transient volumetric heat transfer coefficient prediction of a three-phase direct contact condenser

A steady-state one-dimensional multiphase flow model is developed to describe the characteristics of a spray column type direct-contact liquid-liquid heat exchanger. Several models are assumed to describe the interphase heat exchange between water as the continuous phase and organic liquids as the dispersed phase. For small-diameter droplets, it is shown that existing experimental data are best described by a model that assumes the heat transfer is controlled by conduction within the drops

A Heuristic Evaluation of the Governing Mode of Heat Transfer in a Liquid–Liquid Spray Column

The governing equations for the transient multiphase flow in a liquid-liquid spray column are developed. Using the model, numerical calculations are presented that represent typical fluctuations observed in the operation of the direct contact tower of the geothermal power plant at East Mesa. The response time is determined for the column and conditions leading to local flooding are determined

M. Golafshani

Papers

A Heuristic Evaluation of the Governing Mode of Heat Transfer in a Liquid–Liquid Spray Column

Stability of a Direct-Contact Spray Column Heat Exchanger