Giorgi Gigineishvili

The article presents the results of an experimental study to determine the effect of two-dimensional, pyramidal and combined roughness on heat transfer when a water film flows down the outer surface of a vertical pipe. A two-dimensional roughness was created by winding a wire around a pipe. The pyramidal roughness was created by cutting the left and right screws on the pipe, as a result of which the pipe surface was covered with densely spaced truncated pyramids of height - k. The combined roughness was created by a combination of the above two types with different heights - h and relative step - s/h of two-dimensional roughness. Three regimes of manifestation of the effect of roughness on the intensity of heat transfer were identified: 1. Regime without manifestation of the effect, 2. Regime with partial manifestation of the effect and 3. Regime of full manifestation of the effect of roughness on heat transfer. It was experimentally established that the maximum increase in the heat transfer intensity (more than 3.5-times) is achieved in the case of using a combined roughness with geometric parameters: k=0.25mm, h =0.7mm, s/h =10. It was also found that the effect of the combined roughness (pyramidal + spiral) on heat transfer in the entire range of the Reynolds number investigated by us is higher than the effect of both two-dimensional and pyramidal roughness.

It has been experimentally established that the creation of two-dimensional roughness on the heat-transfer surface causes a significant increase in the intensity of heat transfer into a film flowing down the surface of a vertical pipe. The highest effect is achieved with the ratio of the step between the roughness elements to their height s/h=10.

The paper describes the current state and prospects for further development of steam engine-pump (SEP) powered by low potential heat. The SEP differs from classical membrane pump by upper part that represents the simplest heat engine with opposing pair, evaporator (heated from above cover with downward facing capillary surface) and upward-facing condenser (a membrane cooled from below by pumped water), and certain charge of low-boiling working agent. When integrated in standalone hot water supply with solar flat plate collector(FPC) the SEP can pump water from water well through the FPC to hot water tank located at high mark, without electric power consumption and virtually no heat loss. The SEP can also circulate water in cooling system of stationary diesel power unit, using the exhaust heat instead spending for it the part of the engine power. In the early years three prototypes of the SEP have been developed. At the present stage new (forth) prototype is developed with so-called „two-speed condensation mode“ ensuring improved performance. Feasibility of the pumping process and encouraging level of efficiency are demonstrated. The problem of self startup is also solved. The thermodynamic cycle of the SEP is considered. The peculiar stage of the cycle is identified when the pair membrane-condensed working agent hits the dried and overheated evaporator. Sandwiched between the evaporator and membrane condensate undergoes peculiar process of boiling that we call percussive boiling. The results of modeling and experimental study of the percussive boiling are also presented.

The paper describes the thermal scheme and the theoretical thermodynamic cycle of the steam-engine working on a wet saturated steam. Created the formula for calculation of the thermal efficiency coefficient of the presented cycle and comparison calculated values with efficiency of the Carnot cycle, at different pressures. Work is funded by a grant from Shota Rustavelı Natıonal Scıence Foundatıon of Georgıa.

The report presents an innovative, solar-powered water-pump. When integrated with a solar flat-plate collector, the pump can circulate water without the electricity consumption and virtually no heat loss. The pump represents the new stage in further development of the created previously specific steam engine-pump alternating evaporation and condensation processes of an intermediate agent in the single working chamber. In order to improve essentially the main characteristics of the pump the new design was proposed and patented.

In the case of several different thermal systems, in particular in the case of low-temperature distillation equipment and heat pump systems for technological processes of milk production processes, the feasibility and effectiveness of one of the most important visible tools for estimating energy efficiency - the practical application of energy flow diagrams is shown. This method will be useful in the process of conducting energy audits of industrial enterprises and buildings

A model of “theatre of director” links dependence of developed boiling HTC only on two external parameters (heat flux average effective radius of active nucleation sites) to short duration of each action of cooling mechanisms. According multifactoring concept significant prolongation of the actions of cooling mechanisms leads to transition to specific regimes with dependence on increased number of factors (duration-dependent multifactoring). Splitting of developed boiling heat transfer curve into several curves, depending on subcooling of bulk liquid, direction of gravity field and thermal parameters of heating surface, has been fixed through experimental study of duration-dependent multifactoring of pool boiling heat transfer on down-facing horizontal heating surface. Interpretation and qualitative analysis of received experimental data on HTC and video films of characteristic boiling regimes allow to arriving at the conclusion about applicability of unified consistent research framework multifactoring concept in terms of description of diversity of boiling heat transfer curves.

Conceptual design of solar-powered water pump integrated into flat plate solar collector has been carried out. SPWP represents simple heat engine-membrane pump operating through alternating of process of evaporation and condensation in its working chamber. It should provide circulation water using part of absorbed by FPC heat and returning it finally to the same heat carrier. Two basic versions of structural layout of FPC have been considered: the first – with flow-through absorber (with circulation of water through riser welded to absorber plate) and the second – with absorber with gravity-assisted heat pipes. In terms of efficient operation important role of proper organization of boiling heat transfer on down-facing heating surface of working chamber has been revealed. Thermo-hydrodynamic peculiarities of this process are considered. The results of preliminary experimental study of boiling heat transfer on downward-facing heating surface are presented

The results of experimental investigation are presented of boiling heat transfer on grooved capillary surfaces. The peculiarities are considered connecting with description of the process by regularities of pure evaporation or pool boiling. Correspondence is revealed of the process to general developed boiling heat transfer law. Approximate approach is developed to evaluation of heat transfer coefficient built upon parameters of incipient boiling at given combination liquid-capillary surface. Semi-empirical equation is offered describing with adequate accuracy existing experimental data on boiling of different liquids on grooved capillary surfaces of different materials and geometrics

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Scientific editor of monographs in foreign languages

Scientific editor of a monograph in Georgian

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Participation in a project / grant funded by an international organization

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Monograph

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Research articles in high impact factor and local Scientific Journals

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