Jonas Gylys

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.

Combined heat and power production: Socio‐economic and sustainable development aspects

Abstract The paper is based on the study of Lithuania facing the need for huge investments in both the replacement of the Ignalina nuclear power station and the replacement of district heating production units in many of the existing systems. Lithuania has a big technical potential for implementing small‐scale combined heat and power production (CHP) systems. Meanwhile, such implementation needs public regulation to become feasible not only from a socio‐economic, but also from a business economic point of view. The study focuses upon the analysis of methods for the incorporation of technical, economical and environmental considerations into large‐scale investment decision‐making in the energy sector. The research study could be a guideline for determination of national potential for high efficiency CHP not only from the technical, but both the economical and the environmental point of view. Based upon the results of the study investigation and analysis, areas for improvement in current energy sector inves...

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.

Experimental Study Of Heat Transfer FromIn-line Tube Bundles To Upward Foam Flow

The heat transfer from the in-line tube bundle to the vertically upward directed laminar aqueous foam flow was investigated by means of experimental set-up, consisting of the foam generator, experimental channel, in-line tube bundle, measurement instrumentation and auxiliary equipment. Two in-line tube bundles with different geometries were used for the experiments. One bundle consisted of three rows with six tubes in each. Spacing between centres of the tubes across the experimental channel was s1=0.06 m and spacing along the channel was s2=0.03 m. The second in-line tube bundle consisted of five vertical rows with six tubes in each. Spacing between centres of the tubes was s1=s2=0.03 m. All tubes had an external diameter of 0.02 m. Statically stable foam was used for experiments. It was noticed that structure of foam varied while it passed the bundle: bubbles changed their size, liquid drainage from the foam appeared. Dependence of heat transfer intensity on flow velocity, volumetric void fraction of foam and liquid drainage was determined and described by empirical relationships. Moreover, density and the pattern of tubes location were estimated in experiments and the development of the heat transfer computation method.

Pecularities of heat transfer from in-line tube bundles to upward aqueous foam flow

Four in-line tube bundles with different geometry were investigated for establishing their performance in terms of heat transfer enhancement. Two-phase aqueous foam was used as a coolant. Such coolant was considered, because our previous research showed that large heat transfer intensity may be reached even at small mass flow rate of the foam. Spacing among the centres of the tubes across the first in-line tube bundle was 0. 03 m and spacing along the bundle was 0. 03 m. In the second case spacing among the centres of the tubes across the bundle was 0. 03 m; spacing along the bundle was 0. 06 m. In the third case spacing was accordingly 0. 06 and 0. 03 and in the last case spacing was accordingly 0. 06 m and 0. 06 m. During an experimental investigation it was determined a dependence of heat transfer intensity on flow parameters. The investigation of heat transfer from the bundle to upward vertical foam flow was provided for three different values of foam volumetric void fractions β=0. 996÷0. 998. The velocity of the foam flow was changed from 0. 14 to 0. 30 m/s. The heat transfer coefficient varied from 200 to 2000 W/(m2K) for the above mentioned foam flow parameters. (Less)

Experimental Investigation Of The Heat TransferProcess Between A Tube BundleAnd An Upward Aqueous Foam Flow

High heat transfer intensity and low energy consumption for coolant transportation to heat transfer location are really significant nowadays. An extended range of heat transfer intensity control (control of volumetric void fraction and flow rate of coolant) and low mass flow rate of coolant are one of the most important factors for heat exchangers. In some cases the usage of aqueous foam as a coolant can solve all of the mentioned problems. Our previous investigation showed that heat transfer between a heated tube and aqueous foam flow is over five to ten times lower for the water coolant, but the density of foam is more than one hundred times lower than that of water. When applying aqueous foam as a coolant in practice, some cases are problematic. The reasons for this are the variation of the structure and the characteristics of foam. Therefore, usage of aqueous foam as a coolant needs to be narrowly explored. This work follows our previous investigations. The tube bundle with a new arrangement of tubes was used in this research work. Spacing between the centres of the tubes in the horizontal lines of the bundle and the spacing between tube lines were equal to 0.03 m. Each following line of tubes was located 0.01 m to the right of previous line. During the experimental investigation the dependence of heat transfer intensity (from tubes to foam flow) was determined on the volumetric void fraction of foam and the foam flow velocity. The experiments were performed for upward vertical foam flow for three different values of foam volumetric void fractions equal to 0.996, 0.997 and 0.998. The velocity of the foam flow was changed from 0.14 to 0.32 m/s. The influence of tube position in the bundle for www.witpress.com, ISSN 1743-3533 (on-line) WIT Transactions on Engineering Sciences, Vol 68,

Tube Bundle’s Cooling By Aqueous Foam

Single-phase coolants, such as water, oil or air, are mostly used in industrial apparatus. But usage of two-phase coolants, such as aqueous foam, can significantly reduce material and energy expenditures, simultaneously sustaining proper heat transfer intensity on heated surfaces. Comparing with single-phase coolant, the two-phase foam coolant has additional possibility to change the intensity of heat transfer by changing volumetric void fraction of foam. This enables wider range of regulation of heat transfer intensity. An experimental investigation of heat transfer between in-line tube bundle and aqueous foam flow was performed. One type of aqueous foam – statically stable foam – was used as a coolant. Vertically downward moving foam flow crossed the in-line tube bundle. Spacing between the centres of the tubes across the in-line tube bundle was 0.03 m and spacing along the bundle was 0.03 m. During an experimental investigation it was determined dependence of heat transfer intensity on flow parameters: flow velocity, volumetric void fraction and liquid drainage from foam. Apart of this, influence of tube position in the bundle on heat transfer was investigated. Experimental results were summarized by criterion equations, which are suitable for the design and calculation of foam apparatus. Mentioned experiments are the continuation of our previous investigation with foam flow moving downward after 180-degree turning.

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.

Numerical investigation of two-phase aqueous foam flow for heat exchanger applications

This work details investigation of two-phase aqueous foam flow, which is applicable for developing energy-efficient heat exchangers. In such heat exchangers, heat transfer rates are enhanced due to the structure and properties of aqueous foam, namely gas bubbles separated by a thin liquid film. Aqueous foam is noted to have an especially large inter-phase contact surface and reduced surface tension when compared to pure liquids. However, the foam flow in a channel provided with a heated surface (representing a typical heat exchanger element) invokes rearrangement and collision of foam bubbles. This in turn induces changes in local foam velocity, redistribution of volumetric void fraction and temperature. To study this phenomenon, the finite volume method was applied, which was implemented in FLUENT software (version 6.2). The computation domain consists of a rectangular channel with heat pipe located in a middle of a channel. The influence of different velocities and values of volumetric void fraction was examined. The relationship trend obtained by numerical modelling was compared with data obtained from experimental investigations. (Less)