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Kukulka D.J.,York College | Smith R.,Vipertex
World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conferen | Year: 2012

Many alternative forms of energy are being evaluated in the search for replacement energy sources and solar energy is proving to be one of the most promising forms of alternative energies. Solar thermal systems are a developed form of solar technology and provide an opportunity for design enhancement. Most of solar thermal designs involve the transfer of energy across a solar absorber surface; and most absorbers are flat, unenhanced absorbers. These surfaces utilize old unenhanced surface technology and that makes them prime candidates for redesign and improved process performance. Heat transfer enhancement has become popular recently in the development of a wide range of high performance thermal systems. New solar designs are desired that are lighter and more efficient; with a smaller footprint. Vipertex™ developed the EHT series of solar surfaces that provide: an enhanced energy exchange surface; is lighter; and provides the same or greater structural rigidity as classic absorbers. Enhanced heat transfer surfaces meeting those requirements are produced through material surface modifications that result in: additional heat transfer surface area, increased energy absorption, increased fluid turbulence, generation of secondary fluid flow patterns, and disruption of the thermal boundary layer. Vipertex EHT surface design criteria includes: maximization of the overall energy transfer; a minimization of any friction increases that might occur in the flowing fluid; minimization of material usage; reduction in absorber weight; and a structurally sound surface. Development of the enhanced surfaces included computational fluids dynamics (CFD) modeling and experimental evaluation of the developed solar surface. CFD modeling allowed a comparison of the flow patterns for several alternative surfaces. Experimental results of the enhanced solar surfaces show a 20% increase in energy transfer for a range of conditions. These enhanced surfaces recover more energy and provide an opportunity to advance the design of many solar thermal and PV/T products.


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.


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.


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.


Kukulka D.J.,York College | Smith R.,Vipertex
Chemical Engineering Transactions | Year: 2013

Enhanced heat transfer surfaces are produced by modifying a process surface. New tube and process designs are necessary in order to increase heat transfer, minimize operating costs and save energy. In a comparison of first generation Vipertex enhanced heat transfer tubes with smooth tubes, an increase of performance in excess of sixty percent was determined for the enhanced tubes. This study was undertaken to further enhance heat transfer on the outer surface of these heat transfer tubes. Through the use of computational fluid dynamic (CFD) methods, a flow optimization study of the characters that are used to build the enhanced surface was performed. This study evaluates the effect of character pattern and character geometry on the fluid flow and heat transfer of the process surface. As a result, new process surface designs were developed that produce performance enhancement on the outside of a tube for Reynolds numbers to 215,000. For this range, the minimum increase in heat transfer was experimentally determined at low flows to be 125 %; an increase of heat transfer in excess of 200 % was found for high flows. Modest increases of the friction factor accompany these increases in heat transfer. Heat transfer enhancement is important in the development of high performance thermal systems. Many industrial processes involve the transfer of heat energy and most employ old technology; if improved process performance is desired, these processes should be considered for redesign using enhanced surfaces. Enhanced heat transfer performance is the result of a combination of surface variations that are a result from this detailed surface study. Enhanced performance characteristics include: increased fluid turbulence, secondary fluid flow patterns enhancement, disruption of the thermal boundary layer and increased process surface area. These enhanced factors lead to an increase in the heat transfer coefficient; the ability to produce a unit with a smaller unit footprint; systems that are more economic to operate and have a prolonged product life. This provides a very important and exciting advancement in the design of processes that utilize heat transfer tubes and surfaces. Copyright © 2013, AIDIC Servizi S.r.l.


Kukulka D.J.,York College | Smith R.,Vipertex
Chemical Engineering Transactions | Year: 2013

Demands to increase performance of modern heat exchange systems are constantly being made; requiring the removal of larger rates of energy, using process units that occupy a smaller unit footprint. Heat transfer enhancement plays an important role in improving energy efficiency and developing high performance thermal systems. Heat transfer processes that involve boiling are typically efficient modes of heat transfer; however the desire to increase efficiencies of those processes have prompted the development of enhanced heat transfer surfaces for boiling processes. A wide variety of industrial processes involve the transfer of heat energy during phase change and many of those processes employ old technology. These processes would be ideal candidates for a redesign that could achieve improved process performance. Utilization of enhanced heat transfer tubes is an effective method used 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. Considerations in the development of the optimized, three dimensional, enhanced heat transfer Vipertube design include the maximization of heat transfer; minimization of operating costs; and minimization of the rate of surface fouling. This study details the 1EHT bundle boiling results over a wide range of conditions. Results for the 1EHT bundle show combined overall bundle increases of shellside and tubeside heat transfer up to 97 % when compared to the heat transfer enhancement of a smooth tube bundle using typical fluids (n-Pentane, p-Xylene and water); for midpoint shellside Reynolds number values in the range of 2,800 to 20,400; with effective mean temperature difference (EMTD) values between 15.4 °F (-9.2 °C) and 118.3 °F(47.9 °C). Enhanced heat transfer tube bundles that are capable of producing efficiency increases in excess of 90 % are important options to be considered in the design of high efficiency processes. These enhanced tube bundles recover more energy and provide an opportunity to advance the design of many heat transfer products. © 2013, AIDIC Servizi S.r.l.


Kukulka D.J.,York College | Smith R.,Vipertex | Li W.,Zhejiang University
Chemical Engineering Transactions | Year: 2014

Heat transfer enhancement has been an important factor in obtaining energy efficiency improvements in refrigeration and air-conditioning applications. Utilization of enhanced heat transfer tubes is an effective method to be 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. Heat transfer enhancement plays an important role in improving energy efficiency and developing high performance thermal systems. 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 heat transfer and fluid flow results of the Vipertex 1EHT, enhanced heat transfer tube over a range of conditions that involved in-tube evaporation and condensation. Results are presented here from an experimental investigation of two phase heat transfer that took place in a 12.7 mm (0.5 in) O.D. horizontal copper tube. The test apparatus included a horizontal, straight test section with an active length heated by water circulated in a surrounding annulus. Constant heat flux was maintained and refrigerant quality varied. In-tube evaporation measurements of R22 and R410A are reported for evaporation at 10 °C with mass flow rates in the range of 15 to 40 kg/h. Single phase measurements are reported for mass flow rates from 15 kg/h to 80 kg/h. Condensation tests were conducted at a 47 °C saturation temperature, with an inlet quality of 0.8 and an outlet quality of 0.1. In a comparison to smooth tubes, the local and average heat transfer coefficients for the Vipertex 1EHT tube exceeded those of a smooth tube. Average evaporation and condensation heat transfer coefficients for R22 and R410A in the Vipertex 1EHT tube are approximately two times greater than those of a smooth tube. Enhanced heat transfer tubes are important options to be considered in the design of high efficiency systems. A wide variety of industrial processes involve the transfer of heat energy during phase change and many of those processes employ old technology. These processes are ideal candidates for a redesign that could achieve improved process performance. Vipertex 1EHT enhanced tubes recover more energy and provide an opportunity to advance the design of many heat transfer products. Copyright © 2014, AIDIC Servizi S.r.l.


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.


Kukulka D.J.,York College | Smith R.,Vipertex | Zaepfel J.,Vipertex
Chemical Engineering Transactions | Year: 2011

Heat transfer enhancement is important in the development of high performance thermal systems. Fouling of a surface occurs when settlement or growth of unwanted material contaminates the surface to the point that the surface can no longer be used. Deposits are the result of a series of complex reactions that cause deposits to form on the surface. Economic and technical problems associated with fouling in process systems are known and documented. Parameters that influence fouling include: surface geometry, surface temperature, surface material/finish, fluid dynamics, flow velocity and fluid properties. For many conditions, fouling can be reduced but not necessarily eliminated. Vipertex™ enhanced surfaces are flow optimized process surfaces that increase 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. In addition to heat transfer enhancement, the fouling rate of Vipertubes™ was much less than the rate of smooth tubes; additionally the total amount of fouling over a given time period was also less. This reduction in the rate of fouling is the result of secondary flow patterns that forms as a result of the patented Vipertex surface design. These secondary flows circulate near the tube surface and clean it, preventing the buildup of materials. Several Vipertubes were studied here, with flow rate and temperature data being monitored for the duration of the study. The tubes are exposed to untreated lake water for various time periods. Transient observations and heat transfer measurements of the surfaces were obtained. Fouling results presented include instantaneous and total fouling amounts. These observations support the conclusion that when compared to smooth tubes, Vipertubes provide superior thermal performance, providing heat transfer increases of more than 100 %. At the same time the surface of the Vipertubes also minimize the detrimental effects of fouling thus providing additional service time for Vipertex designs. Vipertex surfaces enhance heat transfer, minimize operating costs and recover more energy. These enhanced surfaces provide an opportunity to advance the design of many heat transfer products. Copyright © 2011, AIDIC Servizi S.r.l.


Kukulka D.J.,York College | Smith R.,Vipertex | Zaepfel J.,Vipertex
Theoretical Foundations of Chemical Engineering | Year: 2012

Heat transfer enhancement is important in the development of high performance thermal systems. Some enhanced tubes that are currently on the market are vulnerable to fouling. Economic and technical problems associated with fouling in process systems have been previously discussed in literature; however, they still require additional examination. Parameters that influence fouling include: surface geometry, surface temperature, surface material/finish, fluid dynamics, flow velocity and fluid properties. Vipertex™ enhanced surfaces are optimized process surfaces that increase 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. Vipertubes™ that have been exposed to a fouling environment produce more heat transfer than smooth tubes exposed to the same fouling conditions; additionally there was less total fouling over a given time period. The reduction in the rate of fouling is the result of secondary flow patterns that form as a result of the patented Vipertex surface design. These secondary flows circulate near the tube surface and clean it; slowing down the buildup of materials. Vipertex EHT series tubes enhance heat transfer (even under fouling conditions), minimize operating costs and recover more energy than smooth tubes under the same conditions. These surfaces provide an opportunity to advance the design of various heat transfer products. © 2012 Pleiades Publishing, Ltd.

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