Stasys Sinkunas

Influence of vertical foam flow liquid drainage on tube bundle heat transfer intensity

The results of an experimental investigation of staggered tube bundle heat transfer to upward and downward moving vertical foam flow are presented in this article. It was determined that a dependency exists between tube bundle heat transfer intensity on foam volumetric void fraction, foam flow velocity and direction, and liquid drainage from foam. In addition to this, the influence of tube position of the bundle on heat transfer was investigated. Experimental results were summarized by criterion equations, which can be applied in the design of foam type heat exchangers.

Different Type Tube Bundle Heat Transfer to Vertical Foam Flow

Gas-liquid foam due to especially large inter-phase contact surface can be used as a coolant. An experimental investigation of the staggered and in-line tube bundles’ heat transfer to the vertically upward and downward laminar foam flow was performed. The experimental setup consisted of the foam generator, vertical experimental channel, tube bundles, measurement instrumentation and auxiliary equipment. It was determined dependency of heat transfer intensity on flow parameters: flow velocity, direction of flow, volumetric void fraction of foam and liquid drainage from foam. Apart of this, influence of tube position in the bundle to heat transfer was investigated. Foam flow structure, distribution of the foam’s local void fraction and flow velocity in cross-section of the channel were the main factors which influenced on heat transfer intensity of the different tubes. Experimental investigation showed that the heat transfer intensity of the frontal and further tubes of the bundles to vertical foam flow is different in comparison with one-phase fluid flow. The results of the experimental investigation are presented in this paper.Copyright

Heat transfer during foam flow across bank of tubes

Heat transfer of a staggered tube bank under a flow of foam was investigated experimentally. The experiments were performed on a model of the heat exchanger. The cellular foam flow was used in the model as the heat transfer carrier. The experiments were accomplished for the middle and side rows of a three-row tube bank. The results of investigations are discussed with respect to the influence of tube position in the rows. Also, phenomena of the liquid deposition under cellular foam flow, as well as its influence on heat transfer intensity, are studied. This article is concluded with a simple heat transfer correlation describing the Nusselt number for the process in point.

Modelling of Combined Heat and Mass Transfer of Water Droplets in Thermal Technology Equipment

Water droplet evaporation process is numerically modelled under various heat and mass transfer conditions. Regularities of heat transfer process interaction are examined. Modelling in this work was performed using the combined analytical–numerical method to investigate heat and mass transfer in the two-phase droplets-gas flow system. The influence of forced liquid circulation on the thermal state of droplets is taken into account by the effective coefficient of thermal conductivity. Calculating the rate of droplet evaporation and the intensity of convective heating, the influence of the Stefan’s hydrodynamic flow is taken into account. Balancing energy fluxes in the droplet to within one hundredth of a percent and using the fastest sinking the droplet surface temperature is determined.Copyright

Theoretical and Experimental Analysis of Turbulent Liquid Film Flowing down a Vertical Surface

The purpose of the present study is to obtain a comprehension for the momentum and heat transfer developments in gravitational liquid film flow. Analytical study of stabilized heat transfer for turbulent film was performed. A calculation method of the local heat transfer coefficient for a turbulent film falling down a vertical convex surface was proposed. The dependence of heat flux variation upon the distance from the wetted surface has been established analytically. Experimental study of velocity profiles for turbulent liquid film flow in the entrance region is performed as well. Analysis of profiles allowed estimating the length of stabilization for turbulent film flow under different initial velocities.

Analysis of In-line Tube Bundle Heat Transfer to Vertical Foam Flow

Liquid or gas (single phase coolant) is widely used for heat removal in heat exchangers. Nevertheless usage of two-phase system (foam flow — particulary) as a coolant in some cases allows achieving better results: smaller coolant mass flow rate, relatively large heat transfer rate, low energy consumption required for coolant delivery to heat transfer place and etc.. An experimental study of the in-line tube bundle heat transfer to the vertically upward and downward after 180 degree turn laminar foam flow was performed. One type of gas-liquid foam-statically stable foam flow was used as a coolant during the experiments. It was determined dependence of heat transfer intensity on flow parameters: flow velocity, direction of flow, volumetric void fraction of foam and influence of liquid drainage from foam. Apart of this, influence of tube position of the bundle to heat transfer was investigated. Results of the investigation showed, that heat transfer intensity of the in-line tube bundle to the foam flow is much higher than to the one-phase airflow under the same flow velocity. Heat transfer intensity of the frontal and further tubes to vertical foam flow is different in comparison with one-phase fluid flow.