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Kukulka D.J.,York College | Smith R.,Vipertex
Energy | Year: 2014

Demands to increase performance of modern heat exchange systems are constantly being made. Typical requirements include the removal of larger amounts of energy or the development of process units that occupy a smaller unit footprint. Vipertex™ 1EHT enhanced surfaces have been designed and produced through material surface modifications in order to create flow optimized heat transfer tubes which increase heat transfer with only a modest increase in the friction factor. Considerations in the development of the enhanced, three dimensional 1EHT enhanced heat transfer surfaces include: maximization of heat transfer; minimization of operating costs; and/or a minimization of the rate of surface fouling. This study details the performance of a horizontal oriented 1EHT enhanced surface tube bundle and compares heat transfer results to a horizontal bundle of smooth tubes for single phase and two phase conditions. Results for the 1EHT bundle showan increase in the overall heat transfer coefficient up to 200% when compared to the heat transfer performance of a smooth tube bundle using typical fluids (n-Pentane, p-Xylene and water); for midpoint shellside Reynolds number values in the range of 2010-20,400; with effective mean temperature difference (EMTD) values between 8.6°C and 65.7°C. More nucleation sites are produced on the 1EHT tube surface than on an equivalent length of unenhanced commercial tube. Results from this bundle study indicate that the 1EHT enhanced tube surface is well suited for applications where nucleate boiling is significant. Enhanced heat transfer tube bundles using the 1EHT tubes are capable of producing efficiency increases making 1EHT tubes an important alternative to be considered in the design of high efficiency processes. Vipertex 1EHT tube bundles recover more energy and provide an opportunity to advance the design of many heat transfer products. © 2014 Elsevier Ltd. Source


Kukulka D.J.,York College | Smith R.,Vipertex
Chemical Engineering Transactions | Year: 2012

Heat transfer enhancement plays an important role in improving energy efficiency and developing high performance thermal systems. A wide variety of industrial processes involve the transfer of heat energy and many of those processes employ old technology. These processes would be ideal candidates for a redesign that could achieve improved process performance. Increasing efficiency in process plant operations is always a priority with engineers constantly looking for new ways to reduce energy requirements in process plants. Additionally, there is pressure from the government to reduce energy usage to meet economic and environmental goals. Utilization of an enhanced heat transfer tube is an effective method to be utilized in the development of high performance thermal systems. In many areas of the world the availability of process water is scarce and the lack of abundant cooling water volume causes major problems in process design. Extreme water availability risks exist across the Middle East and North Africa. Many countries in this region have a growing population and ambitious economic development plans, creating additional demands on water. Of particular importance to the global and regional economy is the use of large quantities of water in the production of oil and chemical products. Water scarcity could also lead to further increases in global oil prices and heightened political tensions to protect water supplies in the future. Use of enhanced heat transfer tubes to decrease process water requirements while at the same time provide higher levels of heat transfer in energy conversion processes are important design considerations. These were some of the goals that were considered when the Vipertex" EHT series of enhanced tubes were developed. Enhanced heat transfer tubes must be considered in the design of high efficiency heat exchangers. Their use will allow operations to decrease the required cooling water mass flow rate in order to obtain the required heat transfer rate; allowing the heat exchangers to operate in the transitional flow regime, at flowrates not previously considered with current designs, will save both energy and water. Transition from laminar to turbulent flow for smooth tubes typically is assumed to occur for a Reynolds Number of 2300. In reality, a transition point is not as well defined and for some process conditions actually could occur over a wider range of Reynolds Numbers, typically varying between 2300 and 10,000. Vipertex" enhanced tubes allow transition to occur earlier than 2300, providing increased heat transfer while at the same time using a smaller volume of cooling fluid. Vipertex" enhanced surfaces, have been designed and produced through material surface modifications, which result in flow optimized heat transfer tubes that increases heat transfer through a combination of factors that include: increasing fluid turbulence, secondary flow development, disruption of the thermal boundary layer and increasing the heat transfer surface area. Considerations in the Vipertube™ design (when compared to smooth tubes) include the maximization of heat transfer; minimization of operating costs; and/or minimization of the rate of surface fouling. Copyright © 2012, AIDIC Servizi S.r.l. Source


Kukulka D.J.,York College | Smith R.,Vipertex | Li W.,Zhejiang University
Chemical Engineering Transactions | Year: 2015

An experimental investigation was performed, for a wide range of mass flux values and qualities, to evaluate and compare the convective condensation and evaporation on the outside of a smooth tube and the newly developed Vipertex enhanced heat transfer 1EHT tube. Heat transfer enhancement has been an important factor in obtaining energy efficiency improvements in many two phase heat transfer applications. Utilization of enhanced heat transfer tubes is an effective method that is often utilized in the development of high performance thermal systems. Vipertex™ enhanced surfaces, have been designed and produced through material surface modifications which result in flow optimized heat transfer tubes that increase heat transfer. Surface enhancement of the 1EHT tube is accomplished by using a more pronounced primary enhancement (dimple characters) that has been produced over a secondary pattern made up of petal arrays. Heat transfer processes that involve phase-change processes are typically efficient modes of heat transfer; however current energy demands and the desire to increase efficiencies of systems have prompted the development of enhanced heat transfer surfaces that are used in processes involving evaporation and condensation. Vipertex™ was able to develop a series of optimized, three dimensional tubes that enhance heat transfer. This study details the condensation and evaporation results on the outer surface of the Vipertex 1EHT tube. Results are presented here from an experimental investigation of two phase heat transfer that took place on the outside of a 12.7 mm (0.5 in) O.D. horizontal copper tube. Average evaporation heat transfer coefficients for the outside of the Vipertex 1EHT tube are approximately one to four times greater than those of a smooth tube. However for condensation, the heat transfer is approximately 23 % ∼ 65 % of the heat transfer coefficient found for the smooth tube. In both cases the pressure drop increases. Copyright © 2015, AIDIC Servizi S.r.l.,. Source


Kukulka D.J.,York College | Smith R.,Vipertex
Heat Transfer Engineering | Year: 2014

Solar energy production is an important source of green energy that utilizes various thermal designs. Development and modeling of enhanced photovoltaic-thermal solar surfaces is the subject of this study. Design criteria include maximization of the overall energy transfer; minimization of material; and a minimization of any friction increases that might occur in the flowing fluid; and all of these are required while at the same time a structurally superior surface is necessary. Most current designs involve the transfer of energy across a flat and unenhanced solar surface. Current surfaces utilize old technology, making them prime candidates for redesign and improved process performance. Previously developed Vipertex EHT series solar surfaces were tested and found to provide an enhanced energy exchange surface, increased heat exchange surface area, lighter structure, and structural rigidity that exceeds current surfaces using the same amount of material. Vipertex solar surfaces that meet those requirements are produced through material surface modifications and result in additional heat transfer surface area, increased energy absorption, increased fluid turbulence, generation of secondary fluid flow patterns, and produces a disruption of the thermal boundary layer. These enhanced surfaces provide important changes to solar surface design that allow the advancement of thermal solar devices. © 2014 Taylor and Francis Group, LLC. Source


Kukulka D.J.,York College | Smith R.,Vipertex | Fuller K.G.,Vipertex
Applied Thermal Engineering | Year: 2011

Heat transfer enhancement has become popular recently in the development of high performance thermal systems. Enhanced surfaces are typically utilized to increase heat transfer. This study evaluated the overall thermal performance of Vipertube™ EHT, a series of enhanced tubes produced by Vipertex™. Enhancement heat transfer ratios greater than 1 were found for the four enhanced tubes that were evaluated for single phase flow in the range of Reynolds Numbers near 2900. Vipertubes enhance heat transfer through a combination of factors that include: increasing fluid turbulence, generating secondary fluid flow patterns, disturbing the boundary layer and increasing the heat transfer surface area. Additionally, the Vipertex surface design also minimizes the effects of fouling. All these factors lead to an increase in the overall heat transfer coefficient for both new designs and systems that have operated over time. Several enhanced tube configurations were studied here using heat transfer and fouling measurements. When compared to smooth tubes, the patented Vipertubes increase the overall heat transfer by more than 100% and minimized the rate of fouling. Several versions of Vipertex enhanced alloy tubes are produced under ASTM standards, thereby providing a very important advancement in heat transfer design. © 2011 Elsevier Ltd. All rights reserved. Source

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