Cold Pipe Research Articles

FEASIBILITY STUDY OF A FIXED OFFSHORE OTEC PLANT FOR COST-EFFECTIVE POWER GENERATION IN MALAYSIA

Ocean Thermal Energy Conversion (OTEC) is a renewable energy technology that harnesses the temperature differential between warm surface water and cold deep ocean water to generate electricity and freshwater. Technological advancements have made OTEC increasingly viable, positioning it as a potential solution for sustainable energy generation in Malaysia. Despite its promise, OTEC development in Malaysia is challenged by the need for suitable sites and the high capital costs associated with traditional floating OTEC platforms. Additionally, efforts to attract anchor partners for OTEC projects have been met with limited success, slowing progress in implementation. This study assessed the feasibility of OTEC plant development in Malaysia through the analysis of sea temperature profiles, identifying five potential sites. A multi-criteria analysis was conducted considering factors such as cold water intake pipe length, proximity to power transmission lines, and environmental impact. The study also proposes a fixed offshore OTEC platform with a single-legged caisson structure, incorporating a braced substructure and dual-level production decks to optimize space for equipment and reduce CAPEX. Kuala Baram (Location C) was identified as the most favorable site due to its optimal conditions for cold water intake and proximity to transmission infrastructure. The proposed fixed platform design offers significant CAPEX reductions compared to floating alternatives, enhancing OTEC’s economic potential. The study’s findings support the immediate application of OTEC in Malaysia, particularly in ongoing projects off the coast of Sabah. Further research, including modeling and testing of the platform design, is necessary to advance commercialization and establish OTEC as a key component of Malaysia's renewable energy strategy.

Development of the method for determining the plane cross-wall diversity of cold-rolled pipes on the basis of experimental research with different options of feeding and turning

In recent years, cold pipe rolling mills have been used in Ukraine, where it is possible to perform different modes of feeding and turning the pipe. Formulation of the problem. We need a method that makes it possible to plan the cross-wall variation of the pipes. Goal. Development of a method for determining the planned diversity for the design of production technology to ensure the regulated increased quality of pipes according to their geometry. Methodology. Obtaining experimental results on the effect of feeding and turning modes during cold rolling on the cross-wall variation of pipes. Mode 1 – the feed is performed before the forward movement, and the turn before the reverse movement of the cage; mode 2 - the feed is performed before the forward movement, and the turn is performed before the forward and reverse movement of the cage; mode 3 – feeding is performed in the front and back position of the cage, and the turn is in the back position; mode 4 – feeding and rotation are performed before the forward and reverse movement of the cage). The results. Of the tested modes, mode 2 and mode 4 are the most effective (from the point of view of correcting the cross-sectional variation of the pipe blanks. Scientific novelty. First, additional experimental data were obtained on the magnitude of the cross-sectional variation of the pipes during the cold rolling process of the pipes with different modes of feeding and turning in front of the straight and It is shown that the process of cold rolling of pipes with feed in front of the direct and turning before the direct and reverse movement of the cage gives 1.5 times better indicators in terms of tube accuracy compared to feeding in front of the direct movement of the cage and turning before the reverse movement of the cage. Тhe indicators are given by the process with forward and reverse motion of the cage. Practical significance. The obtained results are needed in the development of technologies for the production of pipes with increased requirements for transverse diversity

The Effect of Heat Tracing Installation for Wax Prevention on Onshore Buried Swampy Pipelines

Transporting crude oil using pipelines is a widely adopted method globally. In one segment owned by PT. XYZ, especially in swampy areas, the fluid temperature tends to drop below the wax appearance temperature (WAT) during oil transportation. This is due to the relatively low temperature in swamp areas caused by heat loss to the environment. The solubility of paraffin in crude oil drastically decreases as fluid temperature drops, causing wax molecules to precipitate and deposit on the cold pipe walls. PT. XYZ employs chemical treatment by adding a pour point depressant (PPD) to lower the pour point temperature (PPT). However, PPD is effective only at certain temperatures, necessitating a study for alternative treatments. Another method involves installing heaters on the pipeline to reduce the viscosity of transported crude oil and enhance its flowability, either through direct heating or heat tracing using insulation with low thermal conductivity. Therefore, in PT. XYZ's case, an analysis is required to identify locations where fluid temperature decreases occur to ensure precise heater installation. Various software tools, including OLGA, have been developed to predict and describe wax deposition phenomena and temperature decreases along the pipeline. OLGA software can simulate locations of fluid temperature decreases in the pipeline, estimate heat loss along the pipeline, and simulate heat tracing technologies to prevent wax deposition. Simulation results indicate that wax deposition can be prevented by installing skin effect heat tracing with a heating power of 15 W/m and insulated with 2-inch aerogel, maintaining the oil temperature downstream at 157.34°F, well above the desired 115°F threshold.

Analysis of Heat Transfer of Molten Salts Startup Flow in Cold Pipes Avoiding Freezing in Solar and Nuclear Energy Systems

Abstract Molten salts are employed as the heat transfer fluid to carry the thermal energy from a solar receiver or a nuclear reactor for delivering to thermal storage systems or thermal power plants for power generation. For the startup operation, molten salts need to be pumped to flow into the pipes which may have lower temperature than the freezing point of molten salt due to the cold ambient temperature overnight or over the suspension of operation. Preventing the freezing of molten salt in cold pipes becomes a critical issue to the safe operation of a concentrating solar thermal power plant or a molten salt nuclear power plant. This study conducted a basic heat transfer analysis of the transient heat transfer from flowing molten salt to a cold pipe to determine the length from entrance to the onset of freezing of the fluid. From our modeling and analytical solution using method of characteristics, the correlation of the location of onset of freezing of molten salt with respect to the flow velocity, heat capacities of molten salt and pipes, dimension of the pipes, and the initial temperatures of salts and pipes, have been understood clearly. The modeling and computational tool can fundamentally help engineers to design a system to avoid freezing and clogging at cold startup when molten salt is applied as a heat transfer fluid.

Mitigation of soil frost heave with fungi

Frost heave and thaw weakening can impose engineering issues on cold region infrastructures, including pavements, slopes, pipes, foundations, and buildings. This study investigated the potential of fungi treatment to mitigate the frost susceptibility of soils. Fungi were grown with organic waste to develop fungal mycelium. Subsequently, it is introduced into the soil. A sensitivity study was conducted on the influence of fungi centration on soil behaviors. The volume change behaviors when subjected to freezing or thawing were monitored. The results indicated that both soil frost heave and thaw weakening were reduced significantly with fungi treatment. The mechanisms are investigated with the measurement of the soil water characteristic curves. The introduction of fungi treatment affected the SWCC and soil water affinity. These affect the moisture transport when soil is subjected to freezing/thawing. Subsequently, the volume changes were suppressed.

Methodology for Fifth Generation District Heating and Cooling Network Simulation

5th generation district heating and cooling networks (5GDHC) will play a rolein the reduction of CO2 emissions and the resilience to global warming. Our analysis of the literature points out that no simulation study proposes a comprehensive enough description of such networks. The simulation solution presented in this article considers the intertwined influences between the thermal-hydraulic balance in the network, the behavior of the decentralized heat pumps and chillers at substations, and the thermal coupling with the ground. For a given simulation scenario, the 3 developed models are iteratively solved until convergence is reached. After showing how the latter is handled,we exhibit an original result about the influence of the differential pressure between the hot and cold pipes.

Effect of microstructure and bending angle in cold bend pipe of SA 106B on flow accelerated corrosion behavior in simulated pressurized water reactor secondary circuit water environment

The flow-accelerated corrosion (FAC) behavior at different bending angles in bend pipe in simulated secondary circuit water environment of pressurized water reactor (PWR) was investigated. The results indicated that the FAC rates at different bending angles within the bend pipe strongly depended on the ferrite nanocrystallization degree and the mass transfer coefficients. Ferrite nanocrystallization played a dominant effect on FAC, and the mass transfer coefficient played a secondary role on FAC, causing the maximum FAC rate in bend pipe was transferred to the 45° position on the intrados.

Low-Frequency Discontinuous Noise Diagnosis and Reduction of Air Conditioner Outdoor Unit

Abnormal discontinuous low-frequency noise occurs in the outdoor unit when the air conditioner is operating at 86~96 Hz. This noise has the characteristics of low frequency, strong penetration, long transmission distance, and poor sound quality, which can cause serious noise pollution. In order to reduce the low-frequency noise of the outdoor unit of the air conditioner, the discontinuous noise frequency is first located by testing the time-domain and frequency-domain maps of the noise. It is then compared with the frequency of fan rotation noise and structural radiation noise. It is found that the discontinuous noise is caused by the coupling of fan rotation noise and structural radiation noise. It is found that low-frequency noise improvement is significant when the frequency difference between two noise peaks is greater than 8 Hz or when a single noise peak is less than 25 dB(A) by studying the methods of frequency modulation and amplitude modulation of noise peaks. By adjusting the fan speed from 930 rpm to 940 rpm, the problem of 94 Hz noise is solved. Then, through testing the natural frequencies of the pipe and shell, it is found that the natural frequencies of the pipe are close to the excitation frequencies. The structural radiation noise is mainly caused by the pipe. Modal analysis is conducted on the pipe. When the normal boundary with the condenser and the normal boundary with the valve of the pipe is constrained by springs, the simulated values are closer to the measured values. Finally, structural optimization design is carried out on the pipe. When the U-tube of the exhaust pipe is shortened by 30 mm, a 30 g mass block is added to the cold inlet pipe, and a 97 g mass block is added to the lower part of the valve pipe of the suction pipe. The discontinuous noise of the optimized prototype is significantly improved.

Development of a Mechatronic System for the Main Drive of a Cold Pipe Rolling Mill

Development of a Mechatronic System for the Main Drive of a Cold Pipe Rolling Mill

Transient modelling of water condensation rate for top of line corrosion

Top of line corrosion (TOLC) is typically a concern in the first few kilometres of wet gas pipelines where water in the warm gas condenses on the cold pipe walls. With the introduction of a subsea tieback to existing infrastructure, the changing fluid composition and temperature profiles may increase condensation in sections not previously expected to have condensation. Accurate prediction of the water condensation rate (WCR) becomes essential to support reliable corrosion modelling. Transient flow simulation of pipeline operating conditions and detailed heat transfer modelling is required to calculate the WCR. This calculation is complicated because the mass of water condensation is very small compared to the fluid mass in the pipeline, and sensitive to glycol that is often present in the aqueous phase for hydrate management purposes. This paper introduces a method to calculate WCR by using detailed transient modelling of the pipeline operating conditions. The fluid thermal hydraulic behaviour and hydraulic pressure drop in the pipeline are considered in the model. The fluid composition in the pipeline and glycol component in the aqueous phase are calculated by using a PVT software package. A few sensitivity studies will also be presented. The implications of Equation of State (EoS) and transient flow module on WCR calculation will be quantified. The WCR sensitivity results will be analysed based on varying inlet temperatures, glycol concentrations, and pipeline heat transfer coefficients. A WCR calculation method will be recommended for TOLC modelling.

The Application of a Self-Made Integrated Three-in-One Microsensor and Commercially Available Wind Speed Sensor to the Cold Air Pipe of the Heating, Ventilation, and Air Conditioning in a Factory for Real-Time Wireless Measurement.

In this study, the integrated three-in-one (temperature, humidity, and wind speed) microsensor was made through the technology of the Micro-electro-mechanical Systems (MEMS) to measure three important physical quantities of the internal environment of the cold air pipe of the Heating, Ventilation and Air Conditioning (HVAC) in the factory, plan the installation positions of the integrated three-in-one microsensor and commercially available wind speed sensor required by the internal environment of the cold air pipe, and conduct the actual 310-h long term test and comparison. In the experiment, it was also observed that the self-made micro wind speed sensor had higher stability compared to the commercially available wind speed sensor (FS7.0.1L.195). The self-made micro wind speed sensor has a variation range of ±200 mm/s, while the commercially available wind speed sensor a variation range of ±1000 mm/s. The commercially available wind speed sensor (FS7.0.1L.195) can only measure the wind speed; however, the self-made integrated three-in-one microsensor can conduct real-time measurements of temperature and humidity according to the environment at that time, and use different calibration curves to know the wind speed. As a result, it is more accurate and less costly than commercially available wind speed sensors. The material cost of self-made integrated three-in-one microsensor includes chemicals, equipment usage fees, and wires. In the future, factories may install a large number of self-made integrated three-in-one microsensors in place of commercially available wind speed sensors. Through real-time wireless measurements, the self-made integrated three-in-one microsensors can achieve the control optimization of the HVAC cold air pipe's internal environment to improve the quality of manufactured materials.

Numerical investigation of condensation-induced water hammer effects in horizontal and vertical cold reheat pipes

Condensation-induced water hammer (CIWH) is an unavoidable phenomenon in power generation facilities and must be properly adjusted for the thermal efficiency and safety of the system. This study simulated CIWH in a realistic steam pipe to analyze its characteristics in horizontal and vertical pipe sections. Additionally, CIWH intensities with respect to key parameter changes were explored for its mitigation. Numerical simulations for the CIWH were performed using an OpenFOAM solver, ICFMCondFOAM, which was validated for multiple phase change computational fluid dynamics (CFD) problems. The geometric and operating conditions of the cold reheat pipe of our partner company were used for CFD simulations. To assess the intensity of the water hammer effect, various inlet water flow rates and steam temperatures were employed and pressure over time was recorded at two measurement points: horizontal and vertical sections. Results of the CFD simulation show that the CIWH phenomenon behaves differently in horizontal and vertical pipes. CIWH strength was also evaluated using the Froude (Fr) and modified Jakob (Ja) numbers. Smaller Fr and larger Ja were found to be desirable for lowering the pressure increase ratios caused by the CIWH in both the horizontal and vertical pipe sections.

Energy harvesting from liquid cooling systems using thermo-electrochemical flow cells

We report a flow thermocell that is integrated into liquid cooling systems to convert the temperature difference between hot and cold pipes into electrical energy. This flow thermocell uses porous Ni foam electrodes that are inserted into the pipes carrying heated and cooled fluids. An aqueous ferricyanide/ferrocyanide electrolyte is used as a coolant fluid to generate electricity through thermally driven redox reactions on the electrodes. The power generation capability of the fabricated device is evaluated for operating conditions. As the flow rate of electrolytes having a temperature difference of 22 °C increase from 0.3 to 1.5 mL/s, the power density increase from 0.129 to 0.208 mW/cm2 owing to the reduction in the mass transport overpotential for power generation, and a Carnot-relative efficiency of 0.304% is obtained at an optimal flow rate of 1.2 mL/s. The efficiency can be further increased to 0.50% by reducing the heat loss from heated to cooled electrolytes with increasing the inter-electrode spacing. The efforts provide here to optimize the design and performance of flow thermocells would be useful in devising new active cooling systems that incorporate the ability to harvest heat flow in liquid cooling systems into electrical energy while simultaneously performing liquid cooling.

Convective heat transfer in I-shape heat sink under the action of Lorentz force via LBM

Via the non-orthogonal multiple-relaxation time Lattice Boltzmann Method, the natural convection phenomenon inside I-shape heat sink under the effect of Lorentz force is investigated. The cavity is filled with MWCNT-Fe3O4/water hybrid nanofluid, and three cold and three hot tubes exist inside the cavity at the same time. The influences of Rayleigh number (103–106), Hartmann number (0–100), magnetic field tilt angle θ (0 – π/2), and different cold and heat pipe arrangements (Case 1–Case 5) on the heat transfer and fluid flow are numerically simulated. The calculated results are shown by the variation of flow lines, isotherms and the average Nusselt number. The results show that the amplitude of the flow function is always the largest for Case 5, which is the best arrangement from the fluid motion point of view, while Case 2 has the largest Nusselt number for different Rayleigh numbers, magnetic field inclination angle θ and different Hartmann numbers, which is the best arrangement from the heat transfer efficiency point of view. However, with different cold and hot pipe arrangements, the average Nusselt number increases when the Rayleigh number and the magnetic field inclination angle θ increase. In contrast, as Hartmann number increases, the average Nusselt number decreases. The local Nusselt number of the cold and hot tubes is further investigated, comparing the discrepancy of the heat transfer performance near each wall surface.

Finite time thermodynamics analysis and research of pulsating heat pipe cold storage device

Phase change energy storage technology can effectively solve the energy mismatch in space and time. There are many disadvantages of phase change materials (PCMs), such as high supercooling, phase separation and poor heat transfer performance. As a new type of heat exchange structure, pulsating heat pipe has the advantages of simple structure, high heat transfer coefficient and good economic behavior. The system efficiency can be greatly improved by using pulsating heat pipe combined with cold storage technology. A set of pulsating heat pipe type cold storage device is developed, the finite time thermodynamic analysis is carried out, and the correlation between heat pipe efficiency and power is established. The three-dimensional physical model of pulsating heat pipe is simulated and verified by experiments. The experimental results show that in the cold storage stage, with the increase of the filling rate, the greater the pressure is, the better the heat transfer effect is; in the cold release stage, with the decrease of the filling rate, the smaller the pressure is, the better the heat transfer effect is.

Investigation of the effect of crystallization conditions and "Difron-4201" depressant additive on the composition and properties of paraffin deposits

For the first time in the laboratory, the physical and chemical characteristics of the model oil sample, the composition, and relative amounts of normal alkanes with carbon atoms from C8 to C60 were determined by high-temperature liquid-gas chromatography. When Difron-4201 is added to the model oil, seven carbon atoms are displaced in the direction of the lower molecular weight distribution of paraffin hydrocarbons in the sediment. The effect of the Difron-4201 additive on the group composition of model oil and oil sediments obtained at different temperatures of the "cold finger" was studied. It was found that with the addition of the additive and with a decrease in the temperature of model oil and "cold pipe", the number of paraffin hydrocarbons in the group composition of sediment increases and the amount of resin and asphaltenes decreases. Microanalysis of the structure of asphaltene–resin–paraffin sediments obtained after the addition of the additive showed that the model oil sediments, separated at 30/1500C and containing large amounts of high-molecular paraffin hydrocarbons, resin, and asphaltene components, have the highest proportion of amorphous structures. An increase in the share of dendritic modification of the crystalline structure is characteristic for paraffin hydrocarbons in sediments obtained with the addition of 900 g/t "Difron-4201" additive.

СИСТЕМА ЭЛЕКТРОПРИВОДА СТАНА ПРОКАТКИ ТРУБ ПАО «ЧТПЗ»

The relevance of the presented work is to increase the speed in the operation of the pipe cold rolling mill for a possible in-crease in technical and economic indicators. In the pilot plant, it was decided to take the KhPT-450 machine (PJSC Chel-yabinsk Pipe Rolling Plant), the speed of which was increased to 30 % by switching on energy-efficient equipment. The analysis of cyclic automation showed that the operating time of the electric drive is about 30 %, which gives a positive technical and economic indicator. In view of this, it was decided to take a decision from the mechanical power circuit of the bevel gear, which in turn turned into a mechanical part of the system. However, reducing the gear ratio of the gearbox leads to a dynamic load on the motor shaft. The analysis of the work of the technological process with the help of the technique of synthesis of the power part of the electric drive is carried out. The method includes several stages of analysis: determination of the trajectory of motion parameters, electrical equipment, structure selection, as well as corrective connection parameters. This method allows you to give a complete reverse opera-tion of the electric drive. As a result, the speed, position, and torque control loop data is carefully correc¬ted. In the Agree-ment, a feasibility study was carried out from the introduction of the presented methodology. The indicators show that the positive effect is not only manifested in the speed of work by 80 %, but the economic effect is also growing in a positive way.

Analysis of the NOx storage behaviour during cold start of modern SCR flow-through substrates and SCR on-filter substrates

AbstractSelective catalytic reduction (SCR) systems are the state-of-the-art technology to reduce nitrogen oxide emissions (NOx) of modern diesel engines. The system behaviour is well understood in the common temperature working area. However, the system properties below light-off temperature are less well known and offer a wide scope for further investigations. Vehicle measurements show that under specific conditions during cold start, NOx can be partially stored and converted on on-filter and flow-through SCR catalysts. The purpose of this work was in a first step to analyse the main influence parameters on the NOx storage behaviour. Therefore, synthetic gas test bench measurements have been carried out, varying the gas concentrations, temperature, and gas hourly space velocity (GHSV). These investigations showed that the NOx storage effect strongly depends on the NH3 level stored in the catalyst, GHSV, the adsorbed water (H2O) on the catalyst, and the temperature of the catalyst. Further influence parameters such as the gas composition with focus on carbon monoxide (CO), short-chain hydrocarbons and long-chain hydrocarbons have been analysed on a synthetic gas test bench. Depending on operating conditions, a significant amount of NOx can be stored on a dry catalyst during the cold start phase. The water vapor from the combustion condenses on the cold exhaust pipe during the first seconds, or up to a few minutes after a cold start. As the water vapor reaches the surface of the catalyst, it condenses and adsorbs onto it, leading to a sudden temperature rise. This exothermal reaction causes the stored NOx to be desorbed, and furthermore it is partially reduced by the NH3 stored in the catalyst.

Top of line corrosion in gas-condensate pipelines

Low alloyed carbon steel is the only viable material of construction for long pipelines transporting unprocessed gas-condensate. The water that condenses is highly corrosive because it contains dissolved acid gases, i.e., CO2, H2S and organic acids like acetic and formic acid. The high velocity gas also contains droplets of water and condensate, and these will deposit if they hit the steel surface. Monoethylene glycol (MEG) injected to prevent ice and hydrates must be considered when predicting the composition and corrosivity of the aqueous phases in the pipeline. The liquids gathering at the bottom of the pipe have a higher heat capacity than the gas, and the temperature at the top of the pipe will be slightly lower than at the bottom. As the produced fluids cool during the transport from the hot wells to the process plant, water will condense on the cold pipe surface and more at the top than at the bottom. The literature on Top-of-line corrosion (ToLC) has grown steadily since the first reported case in 1960. There are also several prediction models for ToLC. This review is an overview of the main factors that cause ToLC and how these are modelled. Mass transfer from the aqueous phase at the bottom to the top contribute to the condensation. Despite the low MEG to water ratio in the gas due to the difference in vapour pressure, the fraction of MEG in the condensing water may be considerable. The concentration of MEG in the aqueous phase at the top depends on the mass transfer from bottom. The same is the case for organic acids. Liquid droplets entrained in the gas may deposit top of line and contribute to the chemistry of the aqueous phase. Models for ToLC must thus not only predict the composition of the condensing phases but also the mass transfer to be able to estimate the corrosion rate.

New Dimensionless Correlations for the Evaluation of the Thermal Resistances of a District Heating Twin Pipe System

The heat losses from pre-insulated double-pipe district heating (DH) systems buried in a homogeneous soil are studied numerically. The study is conducted using the diameter of the pipes and their distance, the size of the insulation, the thermal conductivity ratio between the insulation and the soil, as well as the burial depth of the double-pipe system, as controlling parameters. A computational code based on a control-volume formulation of the finite-difference method has been developed using the open-source framework OpenFOAM with the purpose to compute the heat transfer rate across adjacent solid regions with different thermophysical properties. The main scopes of the study are: (a) to investigate in what measure the geometry and the relative position of the warm and cold pipes, as well as the temperature imbalance, the burial depth and the physical properties of both the insulation and the soil, affect the heat losses; (b) to analyze the existence of an optimal configuration of the DH system by the thermal resistance enhancement viewpoint; and (c) to develop accurate correlating equations for the evaluation of the thermal resistance existing between each pipe and its surroundings, useful for practical thermal engineering applications.