Top Of Pipe Research Articles

Piping Stress Analysis of Low Temperature Storage Tank for LNG

Finite element method has been used to analysis the stress of inner pipes of low temperature storage tank for LNG caused by temperature, pressure and weight. Filling liquid state, storing liquid state and unloading liquid state are considered in this paper. The results show that the stress of the top pipes would be the largest under filling liquid state which is only little larger than storing liquid state. The stress of the bottom pipes would be the largest under storing liquid state. The deformation of the inner container of the tank would influence the stress distribution. Choosing a flexible structure as designing the bottom pipes is reasonable.

On the Minimum Ignition Temperature for the explosive Decomposition of tetrafluoroethylene on hot walls: Experiments and calculations

The Minimum Ignition Temperature of Decomposition (MITD) of tetrafluoroethylene in a partially heated pipe was analyzed for different initial pressures (5, 10 and 15 bara). The pipe used had an internal length of 1 m, an internal diameter of 30 mm with a volume of about 0.7 dm3 and was vertically oriented. Pressure at the pipe top and temperature at four different locations along the pipe axis were measured. Tetrafluoroethylene was found to decompose at lower temperatures for increasing initial pressures, in agreement with previous tests with reactors with fully heated walls. A complete passive quenching in the non-heated part of the pipe was observed only for an initial pressure of 5 bara, while for higher initial pressures, the decomposition propagated completely along the test pipe. Moreover, the test results on the MITD were compared with data from previous experiments in fully heated 0.2 and 3 dm3 cylindrical reactors and showed a decrease of the MITD with the heated volume through heated surface ratio of the vessel. Furthermore, the prediction of the MITD of tetrafluoroethylene by simplified calculation methods was attempted, showing a good agreement with the experimental results.

Effect of glycerol addition on phase inversion in horizontal dispersed oil–water pipe flows

The effect of interfacial tension on the phase inversion process during horizontal pipe flow of an oil-aqueous solution was investigated. Interfacial tension was varied by adding small amounts of glycerol in the water phase. At these glycerol concentrations the density and viscosity of the aqueous phase changed by 1% or less. Exxsol™ D140 (5.5mPas, 828kgm−3) was used as the oil phase. The experiments were carried out in a 38mm ID acrylic test pipe. The phase continuity and appearance of phase inversion were investigated using conductivity (wire and ring) probes and an Electrical Resistance Tomographic (ERT) system. The ERT also provided diagrams of the phase distribution in a pipe cross section. Drop size distribution was monitored using a dual impedance probe. It was found that starting from a water continuous flow with increasing oil fraction at constant mixture velocity the mixture inverted initially in the middle of the pipe (measured at 19mm from the top pipe wall) while a higher oil fraction was required for inversion at the top (measured at 4mm from the top pipe wall) and finally the rest of the pipe. The addition of glycerol did not affect the phase fraction where the initial inversion occurred but caused an increase in the oil fraction needed to complete the inversion. The drop size measurements were used to explain this behaviour. Pressure drop was found to decrease with increasing oil fraction but this trend reversed when inversion spread to the pipe wall and the oil continuous phase came in contact with it.

Analysis of Oil/Water-Flow Tests in Horizontal, Hilly Terrain, and Vertical Pipes

Summary Flow pattern, pressure drop, and water holdup were measured for oil/water flow in horizontal, hilly terrain (±0.5 and ±3°), and vertical pipelines at a temperature of approximately 35 (±5) °C and a pressure of approximately 245 kPa using the large-scale multiphase-flow test facility of Japan Oil, Gas and Metals Natl. Corp. (JOGMEC). Test lines of 4.19-in. (106.4-mm) inner diameter (ID) and 120-m total length were used, which included a 40-m horizontal or hilly terrain (near-horizontal) and a 10-m vertical test section sequentially connected. The flow pattern was determined by visual observation with video recordings, and a flow-pattern map was made for each condition. New flow patterns were identified for horizontal and hilly terrain flow such as oil flow in a snake-like shape at top of pipe at high rate of water flow and water flow at bottom of pipe at high rate of oil flow. New holdup and pressure-drop data are presented for each flow condition. Flow rate and inclination angle influence holdup and pressure-drop behaviors. In vertical flow, when the oil superficial velocity exceeds a certain value, the pressure drop decreases exponentially as the superficial oil velocity, vSO, increases. Slippage between the phases was analyzed using the measured water holdup plotted against the input water cut with inlet-oil flow rate as a parameter and slip velocity vs. measured water holdup. It was found that the slippage changed significantly with slight changes in inclination angle. This paper provides new experimental data of flow pattern, water holdup, and pressure drop measured particularly at horizontal, hilly terrain, and vertical conditions, with large-diameter pipes. This is indispensable information for developing reliable prediction models for oil/water two-phase and gas/oil/water three-phase flow in pipelines.

A heat transfer model for slug flow in a horizontal tube

A new model is presented for the analysis of hydrodynamics and heat transfer which can be used to predict heat transfer coefficients in horizontal slug flow. The results of Jung [Horizontal-flow boiling heat transfer using refrigerant mixtures, EPRI Rep., 1989, ER-6364] show a considerable variation of the heat transfer coefficient around the periphery of the tube at low qualities, with the top of the tube having the highest coefficient. It is shown that this region is likely to be one in which slug flow occurs. The transition into the low quality regime is shown to be closely associated with that into slug flow, using an existing flow pattern map. The model follows the traditional interpretation of evaporative heat transfer, namely that of forced convective heat transfer which may be enhanced by bubble nucleation processes. Slug flow hydrodynamic parameters such as liquid slug and inter-slug (“film”) lengths to total slug unit length, and the top and bottom film thickness and liquid film velocities in the inter-slug regions are important in understanding the heat transfer phenomena. Therefore, heat transfer models developed for pipe top and bottom should include the effects of these slug flow parameters.

Steam Absorption into Films of Aqueous Solution of LiBr Flowing over Multiple Horizontal Pipes.

The absorbers of absorption chillers consist of horizontal tube banks, over the outer surfaces of which absorbent flows and inside of which cooling water runs. The dependence of the distribution of absorption rate on the position of the pipes is important but has not been studied so far. In this work, the cases of one to three pipes are studied experimentally in the range of film Reynolds number between 5 and 40. Three different surfaces are tested to study the effect of wettability, Numerical calculations are also performed using the method proposed in our previous paper. The highest absorption rates are obtained for the pipes with higher knurls, and their distributions agree with the numerical predictions. The pipe position which shows the maximum absorption rate varies with flow rate but the maximum absorption rate does not vary greatly with flow rate. The heat transfer coefficient is minimum and almost constant with flow rate at the top pipe. At lower pipes it becomes larger, but tends to decrease with increasing flow rate.

Steam absorption into films of aqueous solution of LiBr flowing over multiple horizontal pipes

The absorbers of absorption chillers consist of horizontal tube banks, over the outer surfaces of which absorbent flows and inside of which cooling water runs. The dependence of the distribution of absorption rate on the position of the pipes is important but has not been studied previously. In this paper, the cases of one to three pipes are studied experimentally in the range of film Reynolds numbers between 5 and 40. Three different surfaces are tested to study the effect of wettability. Numerical calculations are also performed using the method proposed in our previous paper. The highest absorption rates are obtained for the pipes with higher knurls, and their distributions agree with the numerical predictions. The pipe position which shows the maximum absorption rate varies with flow rate but the maximum absorption rate does not vary greatly with flow rate. The heat transfer coefficient is minimum and almost constant with flow rate at the top pipe. At lower pipes it becomes larger, but tends to decrease with increasing flow rate. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(7): 476–485, 1996

Mixed convection with flow reversal in the thermal entrance region of horizontal and vertical pipes

Numerical analyses have been conducted for combined free and forced laminar convection flow at low Péclet numbers in the thermal entrance region of horizontal and vertical pipes. Effects of both buoyancy force and axial conduction on the hydrodynamic and heat transfer characteristics are systematically investigated, and numerical results are extensively presented for velocity and temperature profiles, distributions of the Nusselt number and wall shear stress in both horizontal and vertical pipes. In a horizontal pipe, the secondary flow pattern has already developed at the beginning of heating and a reverse flow occurs near the pipe top as the axial conduction and buoyancy effects become large. Consequently, the local Nusselt number at the pipe top and then the circumferential average Nusselt number decrease with increasing secondary flow. The regime of reverse flow is clearly identified in the Pe− Ra coordinates. In a vertical pipe, flow reversals are observed at the pipe center in the heating case and near the wall in the cooling case at relatively high | Gr Re |. The regime of reverse flow is identified for both heating and cooling cases in the Pe−| Gr Re | coordinates.

Numerical Analysis of Combined Free and Forced Laminar Convection of Liquid Metals in a Horizontal Pipe.

Numerical analysis has been conducted for combined free and forced laminar convection of liquid metals in a horizontal pipe which is isothermally heated from a certain axial location. The steady-state solutions have been obtained in consideration of axial conduction for Peclet numbers of 0.3∼7.5 and Rayleigh numbers of 15∼500. The results reveal marked effects of axial conduction on the flow and heat transfer characteristics of liquid metals. At the entrance to the heated section, the secondary flow has already developed and a reverse flow occurs near the pipe top as the buoyancy effect becomes large. Consequently, the circumferential average Nusselt number decreases with increasing secondary flow in comparison with that observed in moderate and large Prandtl-number flows. The regime of reverse flow is clearly identified in the Pe-Ra coordinates.

The Double Pipe Test for Commercial Explosives II. Numerical modelling and interpretation

AbstractAn approximate numerical model of the Double Pipe Test has been devised to examine the effects of properties of the top pipe, witness pipe and the explosive on the depth of dent generated in the witness pipe. The model is based on a static calibration of the strength of the witness pipe, with strain‐rate correction for high rates of loading. The inertia of all material accelerated by the explosive product gases is also considered. A comparison of predicted and measured dent depths for various peak explosive pressures shows that the model adequately describes dynamic behaviour during the test. Measured dent depths are expected to correlate with the ability of an explosive to generate a shock wave in rock.

The Double Pipe Test for Commercial Explosives I. Description and Results

AbstractA new test for commercial explosives called the Double Pipe Test has been devised. A column of explosive is placed in the top pipe, simulating a borehole. This pipe rests on a thick‐walled witness pipe, which is dented by the action of the explosive. The arrangement of explosive and initiator in the top pipe is made to represent as closely as possible the practical use of the explosive. No special skill or instrumentation is needed to conduct the test, and scaling up to large charge diameters is easy. Results presented show that the test is very sensitive to variables such as type of initiator and degree of consolidation of the explosive. These and other aspects of explosive performance which are important in their practical use can readily be studied quantitatively with the Double Pipe Test.

The Prehistoric Society of East Anglia

THE members of the Prehistoric Society of East Anglia are to be congratulated on the systematic manner in which they are studying the properties of flint, with special reference to the identification of human workmanship. In the latest part of their proceedings1 Dr. W. Allen Sturge discussess the patina of flint implements, and concludes that it is produced entirely by exposure on the surface. Permanent burial appears not only to retard, but even to prevent, patination. Mr. J. Reid Moir describes some experiments on the chipping of flints, and attempts to show that the flaking of a margin by natural causes is comparatively irregular, while the blows directed by man to produce such flaking are at definite angles with much regularity. He also demonstrates that flakes produced by natural pressure often exhibit a bulb at each end. Mr. F. N. Haward follows with additional notes on the chipping of flints by natural agencies, and concludes that much can be accounted for by movements in the ground. He instances particularly the chipping due to the creeping motion of gravel at the top of pipes in the chalk.