Yaroslav Chudnovsky

Development and Field Trial of Dimpled-Tube Technology for Chemical Industry Process Heaters

Most approaches to increasing heat transfer rates in the convection sections of gas-fired process heaters involve the incorporation of fins, baffles, turbulizers, etc. to increase either the heat transfer surface area or turbulence or both. Although these approaches are effective in increasing the heat transfer rates, this increase is invariably accompanied by an associated increase in convection section pressure drop as well as, for heaters firing ‘dirty’ fuel mixtures, increased fouling of the tubes – both of which are highly undesirable. GTI has identified an approach that will increase heat transfer rates without a significant increase in pressure drop or fouling rate. Compared to other types of heat transfer enhancement approaches, the proposed dimpled tube approach achieves very high heat transfer rates at the lowest pressure drops. Incorporating this approach into convection sections of chemical industry fired process heaters may increase energy efficiency by 3-5%. The energy efficiency increase will allow reducing firing rates to provide the required heating duty while reducing the emissions of CO2 and NOx.

Strategy for Integrated Use of the Industrial Waste Heat

The domestic industrial sector uses over 32 quads of energy that represents one-third of the total energy consumed annually in United States of America. Energy consumption details can be found at www.eia.doe.gov/aer/ . Obviously, that the efficient use of available energy has a substantial impact on the competitiveness of domestic manufacturers as well as on the environment. Efficient conversion of raw materials into usable products and usable work/energy strictly depends on the commercially available technologies and equipment. Energy efficiency significantly varies across multiple industries and different applications but one of the major energy losses is thermal energy loss, so-called waste heat. Sources of the waste heat comprise of variety of gaseous exhausts, waste process liquids, cooling media, chemical waste and environmental losses. Over 30 years the engineering community has been trying to develop cost-effective approaches for waste heat recovery and utilization. However, so far there is no universal and cost-effective solution or approach for the industrial waste heat recovery and utilization. In this paper authors discuss an integrated strategy of the industrial waste heat use through the consideration of the closest surrounding of the waste heat source and other types of waste (chemical, mechanical, acoustical, etc.) along with most promising heat exchanger design concepts to be appropriate for integrated waste heat recovery and utilization.Copyright

Vortex Heat Transfer Enhancement in Narrow Channel by Oval Dimples Arrangement

There are many passive techniques of heat transfer enhancement ranging from surface (2D) to volumetric (3D) vortex generators, however only a few of them are capable to provide a reliable increase in a heat transfer rate overrunning the increase in pressure losses. One of such successful techniques is the profiling of a heat transfer surface with the regulated arrangement of 3D cavities (dimples). The authors explored that the deviation of the dimple geometry from the spherical shape affects the flow structure and thermal and hydraulic performance of the dimpled wall. Detailed numerical simulation of fluid flow and heat transfer has been performed in the narrow channel with the 2.5 × 0.33 cross section normalized by the equivalent diameter of the dimple footprint at the constant Reynolds number Re = 10,000 and the constant heat flux through the dimpled wall. The oval dimple geometry was varied by changing the aspect ratio of the dimple footprint from 1 to 4.5 keeping the same footprint area. In the course of the numerical study, the optimal geometry, the arrangement and the orientation of oval dimples on the heated surface to achieve the superior thermal and hydraulic performance over the spherical cavities are established. Numerical results of local and integral heat transfer characteristics enhanced with the visual representation of the generated vortices clearly illustrated the flow restructuring and an increase in the thermal and hydraulic performance.Copyright

Heat Transfer Between Liquid Film Formed on the Inclined Dimpled Surface and Ambient Air

Heat transfer enhancement area attracts the close attention of the researchers and engineers worldwide for the last decades. The most popular techniques nowadays to enhance heat transfer from the surface is to extend it with the fins, studs, etc. or to profile it with the elements of artificial roughness, winglets, dimples, etc. Those types of surface enhancement allow improving the thermal efficiency of the heat transfer equipment with minimal design modification and without significant capital expenses. One of the interesting and promising techniques of the surface profiling is the formation on the surface the arrangement of spherical dimples, which generate intensive vortex structure near the surface, increase flow turbulence and, as a result, enhance heat and mass transfer between a profiled surface and a liquid (or gas) flowing over it [1–3]. In this connection, it is interesting to establish whether surface profiling will also enhance the heat transfer intensity between a liquid film on such a surface and ambient air. Unfortunately, authors were not able to find any publications on this subject in the open domain. At the same time, the investigation of this process could be of great interest for the engineering practice, in particular, for the cooling towers advancement. In the present work, the authors discuss some experimental results obtained for the different profile parameters and flow regimes.© 2011 ASME

NOx Reduction in Partially Premixed Flames by Flue Gas Recirculation

The authors are currently investigating new technical (both design and operation) approach, which is expected to enable the improvement of the performance of partially premixed type burners without jeopardizing the simplicity, cost, and reliability that this type of burners are well known for. The improvements include significant reduction of the NOx emission without substantial redesign of the combustion system. The results of the experimental investigation of burner operation and design improvements are to be presented and further discussed at the podium.Copyright

Integrated Wastewater Recovery and Reuse via Waste Heat Utilization

A variety of industrial wastewater recovery technologies for different areas and applications has been developed over the years, including primarily thermal and membrane processes. The main thermal processes include atmospheric distillation, distillation with mechanical vapor compression, vacuum distillation, multi-stage flash distillation, multi-effect distillation with thermal vapor compression, etc. [1,2]. The membrane processes contain reverse osmosis, electrodialysis, and nanofiltration. The multi-stage flash distillation and reverse osmosis processes dominate in most applications. Wastewater recovery and re-use technologies have been expanding rapidly in recent decades. The market is also driven by the falling costs of wastewater recovery, which are due to the technological advances in the process. The costs of clean water produced by wastewater recovery process dropped considerably over the years as a result of reductions in price of equipment, reductions in power consumption and advances in system design and operating experiences. In this work state-of-the art and innovative wastewater recovery/re-use technologies are estimated and compared in their features and cost respects. The new technology is discussed that allows increasing in energy efficiency of the wastewater recycling and reduce electricity consumption associated with conventional methods. Successful development and implementation of the technology for food processing applications will provide large energy and water savings to the industry. These savings are tied to an energy efficiency increase and reduction in pumping power for process water supply. The ability to integrate waste heat recovery with wastewater reuse also leads to product cost reduction opportunities for producers.Copyright

Integrated Steam/Organic Rankine Cycle (ISORC) for Waste Heat Recovery in Distributed Generation and Combined Heat and Power Production

Energy efficiency improvement and waste heat utilization in power generation and energy intensive industrial applications are in the main focus of the researchers and engineers nowadays. A great deal of experience was gained by the industrial leaders such as ORMAT, Siemens, Caterpillar, Turboden, and others. However, the commercially and semi-commercially available systems for waste heat utilization have certain restrictions that limit the utilization cycle efficiency to approximately 18%. The paper presents an innovative concept of waste heat utilization system that allows reaching the utilization cycle efficiency up to 28–30% employing low-boiling media such as butane, propane, pentane and others. Applying such a concept to Distributed Generation systems the overall energy efficiency could be boost up to 58–60% and further up to 90% in case of CHP production.Copyright

A Coupled Solution Procedure for Zonal Radiative and Convective Heat Transfer in 3-D Enclosures With Blockages and Screens

A new 3D method of modeling convective-diffusive (CDT) heat transfer and zonal radiation transfer (ZRT) employing different calculation schemes and multi-scale curvilinear grids is presented. The coarse multiblock unstructured grid calculation domain allows use of a conservative and an accurate zonal radiation transfer method with only modest computational effort that requires only a small fraction of total processor CPU time. The blockages (e.g., bars in a furnace) and screens have their own very coarse grids. This reduces the time for defining their intersections with rays. Structured fine grid is used for convective-diffusive (CDT) calculations. The main difficulty (i.e., in coupling between CDT and ZRT numerical computations) is successfully overcome using a simple algorithm. The zonal radiation transfer method is based on a fast algorithm for calculating view factors and total exchange areas. The present approach is fast, efficient and accurate for gas fired furnaces and complex internal configurations of the work pieces with many blockages and screens. The utility of the method is demonstrated by calculating the heating of a hundred round metal bars arranged in a continuous natural gas fired furnace. Good agreement between calculations and industrial experiments is demonstrated.Copyright