ASME Code Case 2877 details the design of heat exchangers using Vipertex tubes.
Presented at the 2017 American Society of Thermal and Fluids Engineers (ASTFE) Conference and 4th International Workshop on Heat Transfer (IWHT)
Enhanced heat transfer tubes are widely used in many areas in order to reduce cost and create a smaller application footprint. A numeric study was performed that predicts performance of industrially relevant heat exchangers using the Vipertex model 1EHT enhanced heat transfer tubes and compares them to the performance of heat exchangers that use smooth surface tubes. The Vipertex model 1EHT tubes can be employed to design more efficient heat exchangers while at the same time decreasing the required mass flow rate and allowing the heat exchangers to operate at lower flows; and if needed, they also can reduce the footprint of the heat exchange device. In addition several cases also compared performance to other enhanced tubes. Some of the low fin options performed better for some cases; while for other cases the 1EHT tube performed better. Vipertex 1EHT tubes produced the most consistent performing option for all the cases considered and demonstrate that it is a good overall tube choice for a wide range of conditions. Through the use of 1EHT enhanced heat transfer tubes, optimized design can reduce the number of tubes while maintaining design requirements. In some designs, the physical size of the heat exchanger can be reduced while maintaining design requirements. Additional case studies for a wider range of conditions will be the subject of future studies.
The following research paper has recently been published in Applied Thermal Engineering detailing results of the Vipertex 1EHT tube.
Volume 103, 2016, Pages 639-650.
Geometric optimization for thermal–hydraulic performance of dimpled
enhanced tubes for single phase ﬂow
Ming Li, Tariq S. Khan, Ebrahim Al Hajri
Department of Mechanical Engineering, The Petroleum Institute, Abu Dhabi, United Arab Emirates
Zahid H. Ayub Isotherm Inc., Arlington, USA
Enhanced surfaces have larger heat transfer surface area and offer increased turbulence level hence allowing higher heat exchange performance. In this study, numerical simulations are conducted to simulate geometric design optimization of enhanced tubes for optimal thermal–hydraulic performance. The simulations are validated with experimental data. Two and three dimensional steady incompressible turbulent ﬂow in dimpled enhanced tube is numerically studied using realizable k– e method. The pressure– velocity coupling is solved by Semi-Implicit Method for Pressure Linked Equations Consistent (SIMPLEC) algorithm. Results show that dimples on tube surface present high heat transfer performance. Compared to staggered conﬁguration, the in-line dimples arrangement provided better overall heat exchange characteristics.
The geometric parameters like dimple shape, depth, pitch and starts are found to have significant effects on overall heat exchange performance while the dimple diameter has insigniﬁcant effect on thermal performance.
A new ASTM standard has recently been approved to produce Vipertex EHT tubes .
It is titled Standard Speciﬁcation for Welded Austenitic Alloy Steel Boiler, Superheater, Condenser, and Heat Exchanger Tubes with Textured
This allows the Vipertex tubes to be produced to the roughly the same standards as ASTM 249
Results from a study that evaluated the performance of 2EHT tubes has just been published in a heat transfer journal.
Title:Experimental study on condensation and evaporation ﬂow inside horizontal three dimensional enhanced tubes
Journal title: International Communications in Heat and Mass Transfer Journal. Volume 80, Page 30-40, 2017.
Experimental investigations of tube side condensation and evaporation in two 3-D enhanced heat transfer (2EHT) tubes were compared to the performance of a smooth surface copper tube. The equivalent outer diameter of all the tubes was 12.7 mm with an inner diameter of 11.5 mm. Both the inner and outer surfaces of the 2EHT tubes are enhanced by longitudinal grooves with a background pattern made up by an array of dimples/embossments. Experimental runs were performed using R410A as the working ﬂuid, over the quality range of 0.2–0.9. For evaporation, the heat transfer coefﬁcient ratio (compares the heat transfer coefﬁcient of the enhanced tube to that of a smooth tube) of the 2EHT tubes is 1.11–1.43 (with an enhanced surface area ratio of 1.03) for mass ﬂux rate that ranges from 80 to 200 kg/m s. For condensation, the heat transfer coefﬁcient ratio range is 1.1– 1.16 (with an enhanced surface area ratio of 1.03) for mass ﬂux that ranges from 80 to 260 kg/m s. Frictional pressure drop values for the 2EHT tubes are very similar to each other. Heat transfer enhancement in the 2EHT tubes is mainly due to the dimples and grooves in the inner surface that create an increased surface area and interfacial turbulence; producing higher heat ﬂux from wall to working ﬂuid, ﬂow separation, and secondary ﬂows. A comparison was performed to evaluate the enhancement effect of the 2EHT tubes using a deﬁned performance factor and this indicates that the 2EHT tubes provides a better heat transfer coefﬁcient under evaporation conditions.
A numeric study was performed that compares the performance of heat exchangers using the Vipertex enhanced heat transfer tubes (model 1EHT) to the performance of heat exchangers that use smooth surface tubes. Heat transfer enhancement is an important factor in obtaining energy efficiency improvements in all heat transfer applications. Surface enhancement of the 1EHT tube is accomplished through the use of the primary dimple enhancement and the secondary background pattern made up of petal arrays. Utilization of enhanced heat transfer tubes is an effective method that is utilized in the development of high performance thermal systems. Vipertex™ enhanced surfaces, have been designed and produced through material surface modifications that produce flow optimized heat transfer tubes that increase heat transfer. Current energy demands and the desire to increase efficiencies of systems have prompted the development of enhanced heat transfer surfaces.
Enhanced heat transfer tubes are widely used in many areas (refrigeration, air-conditioning, petro-chemical, chemical, etc.) in order to reduce cost and create a smaller application footprint. A new type of enhanced heat transfer tube has been created; therefore it is important to investigate relevant heat exchanger designs using the Vipertex enhanced surface tube in industrial applications and compare that performance to other tubes. Results include design characteristics and performance predictions using the design simulations produced using HTRI Exchanger Suite (2016). Performance for all cases considered using the Vipertex tube predicted over performance when compared to a smooth tube design. Vipertex tubes produced higher performance and more efficient designs.
Published and Presented at the 22nd International Congress of Chemical and Process Engineering CHISA 2016 and the 19th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction PRES 2016
Chemical Engineering Transactions, 2016, Vol 52, Pg 115, DOI: 10.3303/CET1652020
Recent results on the condensation and evaporation on the outside of the Vipertex 1EHT has been published in Applied Thermal Engineering, doi:10.1016/j.applthermaleng.2016.03.036.
Results are presented here from an experimental investigation that evaluated the outside condensation and evaporation heat transfer that took place on a 12.7 mm (0.5 in.) OD horizontal copper tube. Evaporation conditions include a mass flux that ranged from 10 to 40 kg/m2 s; with an inlet quality of 0.1 (±0.05); outlet quality of 0.8 (±0.05); and a nominal evaporation temperature of 279 K. Average evaporation heat transfer coefficients for R22 and R410A on the 1EHT tube are in the range of one to four times greater than those of a smooth tube.
The following research paper has recently been published in Applied Thermal Engineering detailing experimental and numeric results of the Vipertex 1EHT tube.
Volume 101, 25 May 2016, Pages 38–46
Single phase heat transfer and pressure drop analysis of a dimpled
Ming Li, Tariq S. Khan, Ebrahim Al-Hajri
Department of Mechanical Engineering, The Petroleum Institute, Abu Dhabi, United Arab Emirates
Zahid H. Ayub
Isotherm Inc., Arlington, USA
A non-dimensional performance evaluation criterion (PEC) was used to assess the thermal-hydraulic performance of heat transfer enhancement achieved with the Vipertex 1EHT enhanced tube. Based on the experimental data, Nusselt number and friction factor estimation correlations were proposed for the enhanced tube. Simulations were carried out to obtain heat transfer and pressure drop characteristics of smooth and enhanced tubes, using commercial Fluent.
Flow visualization of flows near a heat transfer tube and evaporation heat transfer results of Vipertex 1EHT tubes are compared to Smooth Tubes have been presented at ECCE10 (10th European Congress of Chemical Engineering).
Visualizations of Pool Boiling in Water for a 1EHT Tube – Vectors indicating Flow Speed of Particles
The evaporation heat transfer coefficient enhancement ratio (for the range considered for flows using R410a), for the 1EHT tube is approximately 1.4
The results of a joint research project between Shell Oil and Rigidized Metals has recently been published in the Journal of Enhanced Heat Transfer. Heat Transfer advantages of the 1EHT tube for crude fouling conditions are discussed.
Shell Global Solutions (US) Inc.
Ridigized Metals Corp.
Shell India Markets Pvt. Ltd.
The evaluation shows that depending on the applied constraints, different benefits can be obtained using Vipertex tubes, inculding: – a heat duty increase of up to 19%, an 18-30% reduced flow rate to achieve the same heat duties, or a change in the geometry to achieve a 8-9% increase in heat transfer at the same pumping power.