Flow In Smooth Tubes Research Articles

Pressure Drop Estimation of Two-Phase Adiabatic Flows in Smooth Tubes: Development of Machine Learning-Based Pipelines

The current study begins with an experimental investigation focused on measuring the pressure drop of a water–air mixture under different flow conditions in a setup consisting of horizontal smooth tubes. Machine learning (ML)-based pipelines are then implemented to provide estimations of the pressure drop values employing obtained dimensionless features. Subsequently, a feature selection methodology is employed to identify the key features, facilitating the interpretation of the underlying physical phenomena and enhancing model accuracy. In the next step, utilizing a genetic algorithm-based optimization approach, the preeminent machine learning algorithm, along with its associated optimal tuning parameters, is determined. Ultimately, the results of the optimal pipeline provide a Mean Absolute Percentage Error (MAPE) of 5.99% on the validation set and 7.03% on the test. As the employed dataset and the obtained optimal models will be opened to public access, the present approach provides superior reproducibility and user-friendliness in contrast to existing physical models reported in the literature, while achieving significantly higher accuracy.

Ammonia single-phase and two-phase frictional pressure losses in horizontal smooth and straight inner-grooved tubes

The experimental study of single-phase and two-phase frictional pressure losses has been performed with ammonia flow in stainless steel smooth tubes (internal diameter of 5.5 mm and 8.5 mm) and six straight inner-grooved aluminium tubes with different nominal diameters (7.15 to 13.3 mm), length (0.45 to 2.0 mm) and thickness (0.35 to 0.8) of fins. Single-phase test boundary conditions correspond to Reynolds numbers of 1000 to 20,000. Two-phase tests have been carried out at saturation temperature of 45 to 65 °C, mass velocity of 50 to 210 kg·m−2s−1 and vapour quality of 0.1 to 0.9. Comparison of obtained test data with the existing frictional losses approaches shows that the Blasius model is appropriate to single-phase flows in smooth tubes, and Müller-Steinhagen and Heck's (1986) model is most accurate in predictions of two-phase frictional losses in smooth tubes. Existing approaches of single-phase frictional pressure loss predictions in the pipes and channels with longitudinal fins (Carnavos, 1980; Edwards and Jensen, 1994) are not adequately suited to the ammonia test points obtained in the considered straight inner-grooved tubes. A new semi-empirical model has been proposed, based on generalisation around the revealed geometric dimensionless factor, which accurately describes friction pressure losses in the considered inner-finned profiles. The simplest homogeneous model for defining two-phase friction pressure losses, using McAdams et al.'s (1942) recommendation for mixture dynamic viscosity definition and a new model of single-phase friction factor, best fit both quantitatively and qualitatively to ammonia two-phase test points in most of the considered straight inner-grooved tubes.

Evaluation of heat transfer correlations based on input parameters in a solar parabolic trough collector using supercritical carbon dioxide

Concentrating Solar Power (CSP) technologies have emerged as leaders in generating renewable power. Parabolic trough collector (PTC) is the most widely used CSP technology for various applications of solar thermal heat at commercial level. Altering the heat transfer fluid (HTF) to supercritical CO2 (s-CO2) holds promise in improving the efficiency and operations of solar PTC. The present study discusses heat transfer correlations from literature for the horizontal flow in smooth tubes. The correlations have been evaluated for their suitability to predict the average Nusselt numbers by s-CO2 as the HTF in a solar PTC. Nusselt Numbers computed using these correlations have been compared with the validated numerical simulation. Utilizing a previously validated non-uniform solar heat flux as input for the three-dimensional finite volume method, the numerical thermal simulations were performed These correlations have been compared for the operating boundary range of the solar PTC. The impact of each thermophysical input parameter of HTF is outlined in the study. Additionally, a novel correlation is proposed based on the multiple regression of thermophysical input properties of the s-CO2 as HTF in the solar PTC. The proposed correlation based on input parameters has very high prediction accuracy. It can simplify the design analysis of the solar PTC field for the s-CO2.

Validation of a new methodological approach for the selection of wire-coil inserts in thermal equipment

• New methodology to select wire coils for thermal equipment enhancement. • The estimation of TSP for a given insert categorizes its hydraulic performance. • Method experimentally validated for heat transfer enhancement in a solar collector. • 4 wire-coils selected with differentiated behaviours in their friction factor curves. • Pressure drop and heat transfer tests were performed in collectors with wire coils. The use of wire-coils is especially relevant at low Reynolds numbers (below the critical number to turbulent flow in smooth tubes) according to its inherent positive features such as the advance of transition onset and, if they present suitable geometric characteristics, the establishment of an extended transitional flow in a critical Reynolds number interval [ Re CL - Re CT ], with a predictable friction coefficient and Nusselt number. This paper presents the experimental validation of a new methodology based on the evaluation of a non-dimensional geometry-based parameter: the TSP (Transition Shape Parameter) that allows to predict the friction coefficient evolution with wire-coil inserts and enables to compute the extension of the transitional flow region. The close relationship between hydraulic and thermal performance of wire-coil inserts makes this methodology a valuable tool for selecting the most appropriate wire-coil geometry for a given tubular heat exchanger. It is observed that to promote an increase in heat transfer, the value of the Re CL of the wire coil must be less than the operating Reynolds number range of the equipment. Thus, the Re CL - Re CT interval of the insert should fall into this range. In order to validate the methodological approach, an application to harp-type solar thermal collectors with typical Reynolds number range [40-6000] is presented. Four representative wire-coils, with a wide geometrical range characterized by TSP values of 759, 196, 35.3 and 3.1 (exhibiting significant differentiated behaviours in their friction factor curves and critical Reynolds numbers) were inserted inside the risers of a modified solar collector and experimentally tested at laboratory conditions. Static temperature at different locations at the absorber plate, and pressure drop were measured to obtain friction factor and Nusselt number inside riser covering the laminar, transitional and low-turbulent regions. For a general application with friction factor constraints the most suitable wire-coil geometry is the TSP W 02 = 196 with a range of critical Reynolds number of Re CL = 663 and Re CT = 2286 and Nu ¯ w 02 / Nu ¯ s = 2.21 for Re = 300 - 3000 with f ¯ w 02 / f ¯ s = 3 , 82 . However, for the case study presented (a harp-type solar collector) it is feasible to insert the third wire-coil geometry TSP W 03 = 35.3 due to its early transition, with a range of critical Reynolds number of Re CL = 364 and Re CT = 2324 , and Nu w / Nu s = 1.35 for Re = 300 with a high friction factor augmentation f ¯ w 03 / f ¯ s = 18.84 . This geometry also promotes the highest absorber temperature reduction. The greatest temperature reduction is observed in the range of Reynolds numbers [700-2000], reaching approximately 6 °C, which represents approximately 15%.

A performance of a single pentagonal plate and momentum transfer studies

In the present study the momentum transfer rates by using single pentagonal plate as turbulent promoter in circular conduit. The present study contains momentum transfer rates increases or decreases with effect of different type’s parameters at side of the plate as 0.023 m, plate thickness 0.06 m, distance of the plate from the entrance of the test section (h) 0.18 m, offered maximum augmentation. A maximum augmentation of 3.94 folds is observed over smooth tube flow. Friction factor value shows similar behaviour with that of momentum transfer. Friction factor values are found to decrease with velocity. Correlations developed based on semi theoretical considerations. Wall similarity concept is applied for the present case.

Experimental and Numerical Study of Chord-Wise Eight-Passage Serpentine Cooling Design for Eliminating the Coriolis Force Adverse Effect on Heat Transfer

Abstract Gas turbine blades are equipped with internal cooling channels which are connected by 180 deg bends. Due to combined effects of Coriolis force and centrifugal buoyancy force, the heat transfer increases on the trailing side (pressure side) and decreases on the leading side (suction side) for radially outward flow. The trend in heat transfer is opposite for radially inward flow. This configuration leads to nonuniform blade temperature which in unfavorable for blade lifespan. This paper presents a novel eight-passage serpentine design, where passages are arranged along the chord of the blade, to rectify the negative effects of Coriolis force on heat transfer and is an extension four- and six-passage smooth channel studies conducted by the authors earlier. Transient liquid crystal thermography (TLCT) is carried out for detailed measurement of heat transfer coefficients. Heat transfer experiments were performed for Reynolds numbers between 14,264 and 83,616 under stationary conditions. For experiments under rotation, non-dimensional Rotation number is set as 0.05. Heat transfer enhancement levels of nearly twice the Dittus–Boelter correlation (for developed flow in smooth tubes) are obtained under stationary conditions. Under rotation, it is seen that the heat transfer enhancement levels on the leading and trailing sides are similar to each other and also with the stationary condition. Some differences in heat transfer are observed on local level, when rotation cases are compared against the stationary cases. Numerically predicted flow field is presented to support the experimental findings.

Steady-state transverse heat transfer in a single channel CICC

Current mathematical models and numerical codes used for thermal–hydraulic analyses of forced-flow superconducting cables used in the fusion technology, such as, e.g. Cable-in-Conduit Conductors (CICCs), are typically 1D. They demand reliable constitutive expressions for the transverse momentum, energy and optionally also mass transport processes occurring between different parallel conductor components, in order to reliably simulate the behavior of any superconducting magnet design either at normal operating conditions or during a quench evolution. Energy transport processes can effectively be expressed using heat transfer coefficient (HTC) and the considered wetted perimeter/surface. Only few HTC correlations for flow in a CICC bundle have been proposed in the literature, but none of them is widely accepted for predictive use. As a result, in thermal-hydraulic studies of conductors designed for the EU-DEMO coils standard heat transfer correlations for flows in smooth tubes are utilized, although they do not seem very appropriate for CICCs. Systematic measurements of heat transfer coefficients in a CICC bundle should be conducted to provide an experimental database for further trials to develop a reliable predictive heat transfer correlation. In the present work we report the results of measurements of the steady-state HTC between a jacket wall and demineralised water flowing (i) in a smooth tube and (ii) in a CICC bundle of the reference sample (JT60-SA TF conductor). The measurements were carried out at the THETIS installation. We used four values of water inlet temperature, in the range 30–68 °C, and various mass flow rates, in the range 0.15 – 0.40 kg/s, to obtain the results in possibly wide range of Pr and Re numbers. The experimental values of HTC for CICC slightly increased with the mass flow rate from about 7500 to 9400 W/(m2∙K) in the considered Re range (890–3490) and were almost independent on temperature. The performed experiment was also simulated with the THEA code for additional validation of the obtained HTC values.

Heat transfer coefficients of laminar, transitional, quasi-turbulent and turbulent flow in circular tubes

Several well-known correlations to determine the heat transfer coefficients of quasi-turbulent and turbulent flow in smooth tubes are available in literature. However, when these correlations are compared with each other, the results vary over a considerable range. The purpose of this study was therefore to conduct heat transfer and pressure drop experiments in the quasi-turbulent and turbulent flow regimes and to develop an accurate heat transfer correlation that can be combined with recently developed laminar and transitional flow correlations to obtain a single correlation that is valid for all flow regimes. A total of 1180 experimental data points were collected from careful experiments that were conducted ourselves using two different test section configurations. The first test section configuration consisted of a tube-in-tube test section on which the wall temperatures were obtained either indirectly using the Wilson plot method or by direct surface temperature measurements. The second test section configuration consisted of single tubes being electrically heated at a constant heat flux. Different test sections covering a range of tube diameters from 4 mm to 19 mm and a range of tube lengths from 1 m to 9.5 m, were used. Experiments were conducted from a Reynolds number of 2445, which corresponded to the start of the quasi-turbulent flow regime, up to 220,800, which was well into the turbulent flow regime. Water, as well as different concentrations of multi-walled carbon nanotubes, were used as the test fluid, which gave a Prandtl number range of 3–10. A new correlation was developed that could estimate 95% of all the experimental data points within 10% and an average deviation of <5%. Furthermore, it was able to predict experimental data in literature with a Prandtl number range of 0.47–276 and Reynolds number range of 3000–401,600 with an average deviation of 14%.

Multi-Pass Serpentine Cooling Designs for Negating Coriolis Force Effect on Heat Transfer: Smooth Channels

The combined action of Coriolis and centrifugal buoyancy forces results in nonuniform heat transfer coefficient on pressure and suction side internal walls, hence leading to nonuniform metal temperatures and increased thermal stresses. The present study addresses the problem of nonuniform heat transfer distribution due to rotation effect and proposes novel designs for serpentine cooling passages, which are arranged along the chord of the blade. The two configurations were four-passage and six-passage serpentine smooth channels. Detailed heat transfer coefficients were measured using transient liquid crystal thermography under stationary and rotating conditions. Heat transfer experiments were carried out for Reynolds numbers ranging from 12,294 to 85,000 under stationary conditions. Rotation experiments were carried out for the Rotation numbers of 0.05 and 0.11. Heat transfer enhancement levels of approximately two times the Dittus–Boelter correlation (for developed flow in smooth tubes) were obtained under stationary conditions. Under rotating conditions, we found that the four-passage configuration had slightly lower heat transfer compared with the stationary case, and the six-passage configuration had higher heat transfer on both the leading and trailing sides compared with the stationary case. The leading and trailing side heat transfer characteristics were near-similar to each other for both the configurations, and the rotating heat transfer was near-similar to the stationary condition heat transfer.

Thermal performance of meso-scale oscillatory baffled reactors

This study reports the evaluation of heat transfer characteristics and pressure drops in three designs of meso-scale oscillatory baffled reactors over the net flow range Ren = 60–2500 and the oscillatory flow range Reo = 0-1600. The three designs were the oscillatory central baffled reactor (OCBR), the oscillatory helical baffled reactor (OHBR), and the oscillatory orifice baffled reactor (OOBR). The designs were evaluated in terms of “thermal performance” to take the heat transfer and pressure drop into account.Interestingly, in all designs the pressure drop was observed to decrease with increasing oscillation, due to some degree of energy recovery. In all cases, oscillating the flow significantly enhanced the Nusselt number by upto a maximum of around 10-fold. The meso-OBRs were shown to achieve higher thermal performances than steady flows in smooth tubes in all cases. Up to 480%, 460%, and 300% improvements in thermal performance was achieved for the OHBR, OCBR, and OOBR, respectively. The OHBR exhibited the lowest pressure drop, resulting in the highest thermal performance of the designs investigated here. Hence, on the basis of this study, the OHBR design is recommended. New empirical correlations for predicting pressure drop and Nusselt number were established for each design, with data mostly lying in the range ±30% of the correlations.

Determining velocity and friction factor for turbulent flow in smooth tubes

The most popular explicit correlations for the friction factor in smooth tubes are reviewed in this paper. The friction factor for the turbulent flow in smooth tubes is required in some correlations when calculating the Nusselt number. To calculate the friction factor, the velocity profile in a turbulent smooth wall-tube must be estimated at first. The radial velocity distribution was determined using either universal velocity profile found experimentally by Reichardt or by integration the momentum equation using the eddy diffusivity model of Reichardt. The friction factor obtained by using the universal velocity profile gives better results than that obtained from the momentum equation when compared with the Prandtl–von Kármán–Nikuradse equation. Based on the velocity profiles proposed by Reichardt the friction factor was calculated as a function of the Reynolds number and subsequently two formulas for the friction were proposed. They have satisfactory accuracy when comparing with the implicit Prandtl–von Kármán–Nikuradse equation. Thus, it was concluded that the universal velocity profile proposed by Reichardt will provide good results when it is taken into account while integrating the energy conservation equation. There is also a considerable number of experimental correlations for the friction factor in smooth tubes. All these relationships were compared with the experimental data and with the implicit Prandtl–von Kármán–Nikuradse equation that is considered as a standard to test the explicit approximations. The Colebrook and Filonienko explicit correlations are widely used when calculating the Nusselt number for the turbulent flow but they have noticeable errors for small Reynolds number ranged from 3000 to 7000 for the Colebrook relation and from 3000 to 30,000 for the Filonienko relation. For this reason, a new simple and accurate correlation for the friction factor for Reynolds numbers between 3000 and 107 is proposed in the paper.

Experimental investigation on heat transfer and fluid friction correlations for circular tubes with coiled-wire inserts

Heat transfer and pressure drop data for air flow and water flow in smooth tubes with coiled-wire inserts were measured. The wire diameter-to-tube inner diameter ratio (e/d) and coil pitch-to-tube inner diameter ratio (p/d) are in the ranges of 0.0725 to 0.134 and 1.304 to 2.319 respectively. It is found that the Nusselt number (Nu) increases with the e/d value, whereas it increases with a decrease of the p/d value. As air is the working fluid, the dependence of the heat transfer enhancement of the wire coil on the Reynolds number (Re) is minor; as water is the working fluid, the heat transfer enhancement considerably decreases with an increase of the Re value. Two heat transfer empirical equations, one for air and the other for water, are proposed. For both air and water, a common fluid friction empirical equation is established. To effectively and efficiently enhance the heat transfer, for air, the proposed e/d and p/d values of the wire coil are 0.101 and 2.319, respectively; for water, the proposed e/d and p/d values are 0.101 and 1.739, respectively.

An empirical study on heat transfer and pressure drop properties of heat transfer oil-copper oxide nanofluid in microfin tubes

In this paper, the convective heat transfer of the heat transfer oil-copper oxide nanofluid flow in horizontal smooth and microfin tubes is investigated experimentally. Using a flow control system, the flow regime is always laminar and the wall temperature is constant by using a steam tank. Pure heat transfer oil and nanofluid with the weight concentrations of 0.5%, 1% and 1.5% are used as working fluids. The results are in good agreement with the classic correlations for the pure fluid flow. Based on the results, combination use of nanoparticles and the microfin tube leads to the heat transfer enhancement up to 230%, in comparison with the base fluid flow in the smooth tube. The results are useful in the prediction of the heat transfer rate and the pressure drop in nanofluid flows.

Heat transfer in all pipe flow regimes: laminar, transitional/intermittent, and turbulent

A predictive theory is presented which is capable of providing quantitative results for the heat transfer coefficients in round pipes for the three possible flow regimes: laminar, transitional, and turbulent. The theory is based on a model of laminar-to-turbulent transition which is also viable for purely laminar and purely turbulent flow. Fully developed heat transfer coefficients were predicted for the three regimes. The present predictions were brought together with the most accurate experimental data known to the authors as well as with several algebraic formulas which are purported to be able to provide fully developed heat transfer coefficients in the so-called transition regime between Re = 2300 and 10,000. It was found that over the range Re > 4800, both the present predictions and those of the Gnielinski formula [V. Gnielinski, New equations for heat and mass transfer in turbulent pipe and channel flow, Int. Chem. Eng. 16 (1976) 359–367] are very well supported by the experimental data. However, the Gnielinski model is less successful in the range from 2300 to 3100. In that range, the present predictions and those of Churchill [S. Churchill, Comprehensive correlating equations for heat, mass, and momentum transfer in fully developed flow in smooth tubes, Ind. Eng. Chem. Fundam. 16 (1977) 109–116] are mutually reinforcing. Heat transfer results in the development region have also been obtained. Typically, regardless of the Reynolds number, the region immediately downstream of the inlet is characterized by laminar heat transfer. After the breakdown of laminar flow, a region characterized by intermittent heat transfer occurs. Subsequently, the flow may become turbulent and fully developed or the intermittent state may persist as a fully developed regime. The investigation covered both of the basic thermal boundary conditions of uniform heat flux (UHF) and uniform wall temperature (UWT). In the development region, the difference between the respective heat transfer coefficients for the two cases was approximately 25% (UHF > UWT). For the fully developed case, the respective heat transfer coefficients are essentially equal in the turbulent regime but differ by about 25% in the intermittent regime. The reported results are for a turbulence intensity of 5% and flat velocity and temperature profiles at the inlet.

Flow pattern assessment in tubes with wire coil inserts in laminar and transition regimes

The paper presents an analysis of the flow mechanisms in tubes with wire coils using hydrogen bubble visualization and PIV techniques. Results have been contrasted with experimental data on pressure drop. The relation between the observed flow patterns and the friction factor has been analysed. The experimental analysis that has been carried out allows one to state that at low Reynolds numbers ( Re < 400) the flow in tubes with wire coils is basically similar to the flow in smooth tubes. At Reynolds numbers between 500 and 700 and in short pitch wire coils a recirculating flow appears. The insertion of wires coils in a smooth tube accelerates significantly the transition to turbulence. This is produced at Reynolds numbers between 700 and 1000 depending on the wire pitch.

Model of Turbulent Oscillating Flows in Smooth Tubes

Turbulent oscillating flows in smooth tubes are considered. A group of flows in which the logarithmic boundary layer grows monotonically with time is distinguished; the conditions of quasistationarity of these flows are determined. A model of a quasistationary turbulent oscillating flow in a smooth tube is constructed; the model is in satisfactory agreement with experiment.

Turbulent Pressure Loss of Yield-fluids In Pipes

Abstract A friction factor equation for yield fluids (yield-pseudoplastic, yield-dilatant, Bingham) was derived from flow equation under turbulent pipe flow conditions. The rheological characteristics of the yield fluid were described by Herschel and Bulkley model. To verify the validity of the proposed approach a comparison was made between published experimental friction factors and those calculated from the developed equation and Torrance correlation. Results show that the average absolute relative error between the experimental data and calculated data ranges from 2.84 to 5.05% for the developed equation and from 6.97 to 13.68% for Torrance correlation. A comparison was also made between the field measurements of the pressure loss in Mobil pipeline and those based on the proposed friction factor, the results showed good agreement. The evaluation emphasizes the accuracy of the developed equation in comparison to earlier work. Introduction All over the world, there are several pipelines transporting yield-fluids under turbulent flow conditions. Design of such pipelines requires an adequate relationship to determine the pressure loss. The yield-fluids include yield-pseudoplastic, yield-dilatant and Bingham fluids. The rheological characteristics of these fluids can be described by Herschel and Bulkley(1) model. Equation 1 (available in full paper) where: n &amp;gt; 1.0 for yield-pseudoplastic fluids n &amp;lt; 1.0 for yield-dilatant fluids n = 1.0 for Bingham fluids In view of the correlations developed for predicting the friction factor in a pipeline handling a yield fluid, there are two groups: Bingham correlations and yield-pseudoplastic and yield-dilatant correlations. For Bingham fluids, Workers(2–5) had applied the Prandtl mixing length concept to the turbulent flow in smooth tubes to derive a friction factor formula. Hanks and Dadia(6) extended the analysis of Hanks(7) for the turbulent flow of Newtonian fluids to the case of Bingham plastics. Thomas(8) presented Bingham fluid data on the turbulent pipe flow and correlated his data with Blasius equation. For yield-pseudoplastic and yield-dilatant fluids, there exists only one correlation developed by Torrance(9). He extended Clapp's treatment to the power law yield-pseudoplastic fluids and deduced the following correlation. Equation 2 (available in full paper) A comparison between the friction factor calculated from the above equation and the published experimental data(5, 7, 10–14) show that, Equation (2) can be used to predict the friction factor with average absolute relative error ranging from 6.97 to 13.68%. Therefore, it is necessary to develop a more accurate equation for pipeline design calculations. In the present analysis, an equation relating the friction factor to Reynolds number and yield-fluid characteristics is developed. The validity of the equation is confirmed with published experimental data. Theoretical Analysis The flow equation of an incompressible fluid under steady state, isothermal and fully developed conditions is given by(15). Equation 3–18 (available in full paper) Equation (17) represents the velocity distribution at the turbulent core. The maximum velocity (Umax) is obtained by equating the velocities at the interface between the turbulent core and the laminar sublayer, that is Equation 19–23 (available in full paper) Friction Factor To obtain an equation for friction factor, the following definitions are used, Equation 24–28 (availabl

Heat and momentum transfer in non-newtonian turbulent flow in smooth tubes

An extension of the Taylor—Prandtl analogy for momentum and heat transfer is presented for time-independent non-Newtonian fluids. The development given requires pressure drop—flowrate characteristics of the fluids in laminar as well as in turbulent flow in smooth tubes. There is thus no commitment to a specific fluid model. Linear velocity and temperature distributions are used for the viscous sub-layer and an effective viscosity μ e , where μ e = [τ w /(8V/D)] L , is used for the momentum flux in the viscous sub-layer. In evaluating the Prandtl group Pr e, the effective viscosity μ e is used. The effective viscosity used here is different from the apparent viscosity and the effective viscosity used by Metzner et al. and Petersen and Christiansen; the Reynolds group Re B used in based on Bowen's parameters. In evaluating Pr e for suspensions, the fluid properties used are those of the continuous phase which occupies the viscous sub-layer. The analysis has also been extended to power law fluids and to other fluids whose laminar flow properties have been obtained with rotational viscometers.

Comprehensive Correlating Equations for Heat, Mass and Momentum Transfer in Fully Developed Flow in Smooth Tubes

Comprehensive Correlating Equations for Heat, Mass and Momentum Transfer in Fully Developed Flow in Smooth Tubes

Singing Corrugated Pipes

A corrugated tube open at both ends, with air flowing through the tube, sings notes which depend on the flow velocity and the length of the tube. The notes it sings are the natural harmonics of the tube. A given note will sing when the flow velocity is such that the “bump frequency” (frequency at which the air bumps into the corrugations) equals the frequency of the note, provided also that the flow velocity is sufficiently high to induce turbulent flow. For some tube diameters and corrugation lengths the critical minimum Reynolds number that I observe for singing agrees with the classical result Rmin = 2000 observed by Reynolds for turbulent flow in smooth tubes. For other lubes I observe singing at much smaller values of R. Three new musical instruments are described: the Water Pipe, the Gas-Pipe Corrugahorn Bugle, and the Gas-Pipe Blues Corrugahorn.