Return Pipe Research Articles

Validation of RELAP5 model of experimental test rig simulating the natural convection in MTR research reactors

Abstract In an attempt to understand the built-up of natural circulation in MTR pool type upward flow research reactors after loss of power, an experimental test rig was built to simulate the loop of natural circulation in MTR reactors. The test rig consisting of two vertically oriented branches, in one of them the core is simulated by two rectangular, electrically heated, parallel channels. The other branch simulates the part of the return pipe that participates in the development of core natural circulation. In the first phase of the work, many experimental runs at different conditions of channel's power and branch's initial temperatures are performed. The channel's coolant and surface temperatures were measured. The measurements and their interpretation were published by the first three authors. In the present work the thermal hydraulic behavior of the test rig is complemented by theoretical analysis using RELAP5 Mod 3.3 system code. The analysis consisting of two parts; in the first part RELAP5 model is validated against the measured values and in the second part some of the other not measured hydraulic parameters are predicted and analyzed. The test rig is typically nodalized and an input dick is prepared. In spite of the low pressure of the test rig, the results show that RELAP5 qualitatively predicts the thermal hydraulic behaviour and the accompanied phenomenon of flow inversion of such facilities. Quantitatively, there is a difference between the predicted and measured values especially the channel's surface temperature. This difference may be return to the uncertainties in initial conditions of experimental runs, the position of the thermocouples which buried inside the heat structure, and the heat transfer package in RELAP5.

Electricity consumption and economic analyses of district heating system with distributed variable speed pumps

The increasing of energy efficiency and decreasing the transportation power consumption of District Heating (DH) systems have been increasingly focused due to the need to save energy. In this paper a new district heating network with distributed variable-frequency speed pumps (DVFSP) is presented and analyzed. The approach for minimum of the capital costs and energy consumption in a district heating network is presented using a case study based on a district heating network with DVFSP in Dalian, China. The computational tool is a commercial software package, which is used to design and analyze DH networks. Increasing temperature difference between supply and return pipes, the annual total electricity consumption and the equivalent annual cost are reduced. The energy efficiency in the DH system with the DVFSP was compared with the one in the DH system with conventional central circulating pump (CCCP). Analysis results show that the average electrical energy saved by the DH system with the DVFSP is 49.41% of the one saved by the DH system with conventional central circulating pump. The average pumps power consumption of heating area per square meter in primary heat supply network is 0.325kWh/m2.

Construction and 1st Experiment of the 500-meter and 1000-meter DC Superconducting Power Cable in Ishikari

Ishikari project constructs two lines. The length of the Line 1 is 500 m, and connects the photovoltaic cell to the internet-data center. The other line is 1km length, and it is a test facility and called Line 2. The structures of the cable systems are not same to test their performance. The construction was started from 2014 in the field, the Line 1 was completed in May 2015, and it was cooled down and do the current experiment, and warmed up. The Line 2 is almost complete in October 2015. It will be tested in November and December, 2015. In order to reduce the stress of the cable induced by the thermal expansion and contraction, we adopted the way of the helical deformation of the cable. The force of the cable is reduced to 1/3 of an usual cable test. Because the cryogenic pipes are welded in the field and we cannot use the baking of the vacuum chamber of the cryogenic pipe, a new vacuum pumping method was proposed and tested for the cryogenic pipe. Since the straight pipes are used to compose the cryogenic pipe, the pressure drop of the circulation would be 1/100 of the corrugated pipe in the present condition, and it is suitable for longer cable system. The heat leak of the cryogenic pipe is ∼1.4W/m including the cable pipe's and the return pipe's. The heat leak of the current lead is ∼30W/kA in the test bench. Finally the current of 6kA/3sec and the current of 5kA/15min were achieved in Line 1. The reduction of heat leak will be a major subject of the longer cable system. The cost of the construction will be almost twice higher than that of the copper and aluminum over-head line with the iron tower in the present Japan. The cost construction of the over-head line is an average value, and depends on the newspaper.

An electrical impedance monitoring method of water-lubricated oil transportation

We propose a simple and efficient monitoring system based on a single-drive interleaved electrode impedance technique that provides cross-sectional images for real-time detection of fouling in oil–water flows. The simple monitoring method is proposed using a data-interface formula relating between voltage differences measured at sensing electrodes and interfaces of the two immiscible fluids in a pipeline. We estimate the minimum distance between the interface and pipe wall at the images, that is an indicator for monitoring the fouling, by using a voltage–distance map. The robustness of the proposed method is validated through various numerical simulations including oil–water flows in an U-bend return pipe.

Drain Back Systems in Laboratory and in Practice

Drain Back systems with ETC collectors are tested and analyzed in a Danish - Chinese cooperation project. Experiences from early work at DTU, with drain back, low flow systems, was used to design two systems: 1) One laboratory system at DTU. 2) One demonstration system in a single family house in Sorö Denmark. Detailed monitoring and modelling/validation of the system in the DTU lab is done, to be able to generalize the results, to other climates and loads by simulation and to make design optimizations. The advantage with drain back, low flow systems, is that the system can be made more simple with less components and that the performance can be enhanced. Also problems with long term degradation of glycol collector loops are totally avoided. A combination of the drain back and system expansion vessel was tested successfully. It is very important to achieve a continuous slope for the pipes in the collector loop to have a safe reliable operation. The components should also be designed and marked so that only one correct mounting option is possible, like forward and return pipes to/from the collector of slightly different sizes or color. Adapted installer education and training is a very important step to have success with drain back systems. Practices used in glycol systems may give serious failures.

The Stability of Water Ejector Using in Heating System

In the heating system, the water ejector can use the “surplus pressure” to pump return water from return pipe instead of using mixing pumps, thus achieving the purpose of energy conservation. The water ejector is normally devised in the design condition, however, it usually does not operate at the design point because the pressure and flow rate of water in water ejector varies with the fluctuation of adjacent heat consumer, which causes the deviation of the indoor air temperature from the designed value. In the present study, the allowed pressure fluctuation of water ejector was investigated under the condition that the indoor air temperature was maintained in a certain range. The experimental results showed that when indoor air temperature was set at ▪°C, the allowed pressure fluctuation range for the water ejector in Harbin was -10%∼20%, and it expanded as the outdoor design temperature increased and/or the supply water temperature of primary network reduced.

Structure Optimization Design about the Wet Grinding Sanding Machine with Double Cooling System

This paper introduced a wet grinding sanding machine, it is used for fine material. The machine was consists of three parts by stirring grated agencies, cooling system, material handling systems. Rotor and its Rod pin using the whole cast structure, low cost, conical rod pin to improve bending strength. Annular space between the cylinder and the cylinder liner formed cylinder cooling water channel, it connected respectively inlet and return pipes. Hollow spindle, inner pipe, pipe joint and rotor cavity form rotor cooling water channel, dual cooling effect is good. Shell fixed to the cylinder, turn the handle nut, interaction between the thread and the external thread on the piston, forces the pistons to axial movement, used to adjust the working volume and pressure of sanding machine.

Experimental study of flow inversion in MTR upward flow research reactors

Abstract The core cooling of upward flow MTR pool type Research Reactor (RR) at the later stage of pump coast down is experimentally handled to clarify the effect of some operating parameters on RR core cooling. Therefore, a test rig is designed and built to simulate the core cooling loop at this stage. The core is simulated as two vertical channels, electrically heated, and extended between upper and lower plenums. Two elevated tanks filled with water are connected to the two plenums. The first one constitutes a left branch, connected to the lower plenum, and is electrically heated to simulate the core return pipe. The second one constitutes the right branch, connected to the upper plenum, and is cooled by refrigerant circuit to simulate the reactor pool. Channel coolant and wall temperatures at different power and branch temperatures are measured, registered and analyzed. The results show that at this stage of core cooling two cooling loops are established; an internal circulation loop between the channels dominated by the difference in channel's power and an external circulation loop between the branches dominated by the temperature difference between branches. Also, there is a double inversion in core flow, upward-downward-upward flow. This double inversion increases largely the channel's wall temperature. Complementary safety analysis to evaluate this phenomenon must be performed.

Experimental Investigations of Droplet Deposition and Coalescence in Curved Pipes

Even though there have been several studies conducted by the industry on the use of different inlet devices for gas–liquid separation, there have been limited laboratory and field evaluations on the use of external piping configurations as flow conditioning devices upstream of a separator inlet. The results of a systematic study of droplet deposition and coalescence in curved pipe and pipe fittings are reported in this paper. A facility has been designed consisting of two main test sections: a fixed horizontal straight pipe section and an interchangeable 180 deg return pipe section (or curved pipe section) of the same length. Both inlet and outlet to the 180 deg return are horizontal, but the plane of the 180 deg return pipe section can pivot about the axis of the inlet horizontal pipe to an angle as much as 10 deg downwards allowing downward flow in the return section. Various pipe fittings of different radius of curvature can be installed for comparison in the 180 deg return. Fittings evaluated in this study included: 180 deg pipe bend, short elbow bend (with standard radius of curvature of 1.5D), long elbow bend (with custom radius of curvature of 6D), target tee bend, and cushion tee bend. Experiments have been carried out using water and air, and varying gas velocities and liquid loadings. In order to compare the performance of geometries, Droplet Deposition Fractions (DDF) were measured in the horizontal straight pipe section and in the 180 deg return pipe section as a measure of coalescence efficiency. The results demonstrate that higher DDF occurs for curved fittings as compared to the straight pipe section. The short elbow bend has approximately 10% DDF higher, whereas long elbow bend along with 180 deg pipe bend perform better (by 15–20% DDF) than straight pipe. It was found that the cushion tee and target tee bends can coalesce droplets at lower gas velocities but break up droplets at higher gas velocities. Additionally, no significant differences between DDF's in three different inclination angles of a curved pipe were observed. It can be concluded that 180 deg pipe bend or two 6D long radius elbow bend can serve as a droplet coalescer; a pair of cushion tees or target tees can also work as coalescers at low kinetic energy but as atomizers at high kinetic energy.

Energy-efficient and cost-effective in-house substations bypass for improving thermal and DHW (domestic hot water) comfort in bathrooms in low-energy buildings supplied by low-temperature district heating

Using a bypass to redirect a small flow through the in-house DH (district heating) substation directly to the return pipe is a commonly used but energy-inefficient solution to keep the DH network “warm” during non-heating seasons. Instead, this water can be redirected to the bathroom FH (floor heating) to cool down further and thus reduce the heat lost from bypass operation while tempering the bathroom floor and guaranteeing fast provision of DHW (domestic hot water). We used the commercial software IDA-ICE to model a reference building where we implemented various solutions for controlling the redirected bypass flow and evaluated their performance. The effect on the DH network was investigated using Termis software. Bypass flow redirected into bathroom FH during the non-heating period resulted in comparison to the reference case on average in a 0.6 °C–2.2 °C increase of the floor surface temperature and additional cooling of bypass water by 3.9 °C, reducing the heat loss from the DH network by 13% and covering 40% of the heat used in the bathroom FH. The use of the bypass flow in bathroom FH is a cost-effective solution exploiting the heat that would otherwise be lost in the DH network to improve comfort for customers at discounted price.

Minewater 2.0 Project in Heerlen the Netherlands: Transformation of a Geothermal Mine Water Pilot Project into a Full Scale Hybrid Sustainable Energy Infrastructure for Heating and Cooling

In the last 10 years numerous research and commercial initiatives have been undertaken in Europe to develop abandoned coal mining fields into low-temperature resources. One of the most successful is the Minewater project of the municipality of Heerlen, the Netherlands, where a low-temperature district heating system was launched in operation in October 2008, under the European Interreg IIIB NWE programme and the 6th Framework Program project EC-REMINING-lowex. The Minewater project is now being upgraded from a straight forward pilot system to a full-scale hybrid sustainable energy structure called Minewater 2.0. A totally new concept which becomes an essential part of the Sustainable Energy Structure Plan of Heerlen and has the following landmarks:•Energy exchange instead of energy supply: cluster grids for energy exchange between buildings and the existing mine water grid for energy exchange between cluster grids.•Energy storage and regeneration in mine water reservoirs instead of depletion.•Addition of poly-generation: bio-CHP, solar energy, feed in of waste heat (data centres and industry), cooling towers for peak cold demands.•Enlargement hydraulic and thermal capacity mine water grid through improving well pumps, pressure boosting systems and reuse of the existing mine water return pipe for additional supply and disposal of hot mine water.•Fully automatic and demand-driven supply of hot and cold mine water through usage of pressurized buffer systems at the extraction wells and sophisticated injections valves at the injection wells.•All geographically dispersed mine water installations at buildings, clusters and wells are equipped with sophisticated process control units that communicate with a Central Monitoring System (CMS) through the internet. A very new application in the build environment.The first phase of the Minewater 2.0 project is in operation since June 2013. In November 2013 at the congress we will be able to share the first experiences.

Experimental Investigation of the Filling and Draining Processes of the Drainback System (Part 1)

Drainback systems (DBS) were developed in the Netherlands in the 1980's, due to governmental regulations regarding potable water quality. The crucial attribute of drainback systems is the draining of the working fluid from the collector - always when the solar circuit is not in operation. The draining ensures a protection against both, overheating and freezing of the circulating fluid in the solar loop. Small installation failures can disturb the desired filling/draining processes. This can lead not only to improperly operation, but even damage the DBS. Therefore the knowledge on behavior of the DBS during the filling and draining is essential for ensuring the proper operation.An experimental setup was developed in order to investigate the filling and draining processes of the drainback system. Two types of drainback systems were considered: system with drain-back reservoir and heat storage as drain-back reservoir. The first type has a separate, so-called drain-back reservoir which is located on the solar flow circle. The collector is hydraulically connected to the heat storage through an internal heat exchanger coil. In the second system type, the heat storage itself is the drain-back reservoir. The measurement equipment comprised magnetic-inductive flow meters, manometers and a data acquisition system. For additional visual assessments, almost all hydraulic components (tubes, collector's absorber, heat storage, drain-back reservoir) were made transparent and colored water was used as working fluid in the solar loop. Based on the dimensions of a real collector with a meander absorber its “imitator” was made of PVC pipes. The 100 liter heat storage and 25 liter drain-back reservoir were made of PP-H plastic.Different experiments were carried out and evaluated. The processes of filling and draining are described in detail in this paper. Results of this investigation are e.g.:•A siphon is a crucial effect for both filling and draining processes•A minimal hydrostatic height difference less than 10mm between flow and return sides is sufficient for draining•The largest share of the heat carrier drains over the solar return pipe, caused by siphoned draining•Horizontal piping without slope does not disturb the draining processExplanations of these processes will be presented in the paper.

A Study on the Key Parameters of Slit Air Nozzle for the Coating Process of Li-Ion Power Battery

The coating and drying process of Li-ion power battery plays an important role in performance of battery. Its drying system is composed of an air inlet and return pipe, heat exchanger, air nozzle and so on. The air nozzle is a key component of drying system. Whether its design is reasonable or not, it will directly affect the distribution of the velocity, pressure and other factors in the dryer. In this paper, the simulation research of the key parameters of slit air nozzle on the coating and drying of Li-ion power battery will be achieved by using fluid simulation software. And then we determine the slit width of the air nozzle with 3mm, slit angle of air nozzle with 60° on the basis of the simulation results.

Flow-Feedback Method for Mitigating the Vortex Rope in Decelerated Swirling Flows

When reaction hydraulic turbines are operated far from the design operating regime, particularly at partial discharge, swirling flow instability is developed downstream of the runner, in the discharge cone, with a precessing helical vortex and its associated severe pressure fluctuations. Bosioc et al. (2012, “Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone,” ASME J. Fluids Eng., 134(8), p. 081104) showed that this instability can be successfully mitigated by injecting a water jet along the axis. However, the jet discharge is too large to be supplied with high pressure water bypassing the runner, since this discharge is associated with the volumetric loss. In the present paper we demonstrate that the control jet injected at the inlet of the conical diffuser can actually be supplied with water collected from the discharge cone outlet, thus introducing a new concept of flow feedback. In this case, the jet is driven by the pressure difference between the cone wall, where the feedback spiral case is located, and the pressure at the jet nozzle outlet. In order to reach the required threshold value of the jet discharge, we also introduce ejector pumps to partially compensate for the hydraulic losses in the return pipes. Extensive experimental investigations show that the wall pressure fluctuations are successfully mitigated when the jet reaches 12% of the main flow discharge for a typical part load turbine operating regime. About 10% of the jet discharge is supplied by the plain flow feedback, and only 2% boost is insured by the ejector pumps. As a result, this new approach paves the way towards practical applications in real hydraulic turbines.

Energy consumption and economic analyses of a district heating network

An approach for minimisation of the capital costs and energy consumption in a district heating network is presented using a case study based on a district heating network in South Wales, UK. A number of different design cases were simulated using the PSS SINCAL, taking into account different supply and return temperatures and target pressure losses. The operation of the district heating network was synthesised under different design cases using four district heating operating strategies. Optimisation was conducted to obtain the optimal flow rate and supply temperature for the variable flow and variable supply temperature operating strategy. The optimisation model was formulated using the FICO™ Xpress optimisation suite. The objective of optimisation was to minimise the annual total energy consumption and costs. Using each operating strategy, the annual pump energy consumption, heat losses and the equivalent annual cost were found and compared. A variable flow and variable supply temperature operating strategy was found to be beneficial in all cases. Design cases with minimum annual total energy consumption and cost used small pipe diameters and large pressure drops. Further, by increasing temperature difference between supply and return pipes, the annual total energy consumption and the equivalent annual cost were reduced.

Research of Drilling Gas Kick and Blowout Characteristic Based on The Volume of Fluid Model

The accident of drilling blowout out of control is a serious drilling accident. One of the measures that prevent this accident is detecting gas kick early. Mud pool liquid level method is one of the most widely used methods. But, due to the drilling bell mouth is exposed to the atmosphere, drilling fluid in the return pipe flow is not a full pipe flow but a free flow. When the gas kick was tiny, the change of mud pool level is unobvious and Liquid level detection device could not measure the level changes effectually. Drilling fluid return flow can’t be measured, and the error was so great that can’t detect the gas kick early. Air and drilling fluid (non-Newtonian fluid) were taken as mediums, to simulate the drilling fluid liquid level when drilling fluid return flow changed based on the Volume of Fluid multiphase flow model, then the characteristic of liquid level change in the return pipeline was analyzed with different gas rate in drilling fluid. It concluded that the liquid level in the bell mouth was changing obviously, when the drilling fluid has been changed with none gas. Give a suggest that Liquid level detection should be installed on the bell mouth in drilling fluid return pipe in order to find gas kick more accurately and effectively earlier. The gas kick rate has a great impact on the stability of the drilling fluid liquid level in the return pipeline.

Case study of heat transfer behavior of helical ground heat exchanger

This paper presents an experimental and numerical case study of the heat transfer around the helical ground heat exchanger. With varying helical pitch, indoor thermal response tests were conducted in a dry sand. The tests were analyzed based on axisymmetric finite element analyses and recently published heat source models for spiral coil heat exchanger including our modifications of them by adding finite-length line source solution to consider vertical return pipe at center of helical heat exchanger. In addition to reasonable agreements in soil temperature rises at exteriors the helical heat exchanger, existence of return pipe was found to be important for estimation of heat transfer inside helical exchanger. Besides, the heat source models were found to be applicable to approximate mean fluid temperature during TRTs. The numerical and analytical models were applied to field thermal response test for an energy pile reported in literature. Compared with numerically estimations, the analytical solutions considerably overestimated temperature rise at the exterior of the energy pile. The results reveal that reasonable considerations in estimation of effective thermal properties may be needed when applying the heat source models for energy pile, even though they would evaluate reliable heat transfer behavior of helical heat exchanger embedded in a homogeneous ground.

Superconducting Splittable Quadrupole Magnet for Linear Accelerators

A new superconducting quadrupole magnet for linear accelerators was fabricated at Fermilab. The magnet is designed to work inside a cryomodule in the space between SCRF cavities. SCRF cavities must be installed inside a very clean room adding issues to the magnet design, and fabrication. The designed magnet has a splittable along the vertical plane configuration and could be installed outside of the clean room around the beam pipe previously connected to neighboring cavities. For more convenient assembly and replacement a “superferric” magnet configuration with four racetrack type coils was chosen. The magnet does not have a helium vessel and is conductively cooled from the cryomodule LHe supply pipe and a helium gas return pipe. The quadrupole generates 36 T integrated magnetic field gradient, has 600 mm effective length, and the peak gradient is 54 T/m. In this paper the quadrupole magnetic, mechanical, and thermal designs are presented, along with the magnet fabrication overview and first test results.

Water reclamation redesign for reducing Cryptosporidium risks at a recreational spray park using stochastic models

Recreational outbreaks associated with sprayparks are well recognized, and may be partly due to the engineering designs used for their water reclamation systems are problematic to control. This work is based on an outbreak of cryptosporidiosis linked to a spraypark in New York State, where it was determined, specifically that the spraypad (the main attraction) was the primary exposure point. We first determined the likely dose the spraypad users were exposed to, then modeled the efficacy of the treatment system and used this to inform a Monte Carlo method to estimate the probability of infection and illness for the users of the spraypad. The current treatment system which consists of; two holding tanks, a dual media filter and chlorine injection as well as two design change recommendations were modeled using three independent Markov chain models. Within the current treatment system design the receiving tank for the treatment train is also connected with a second pipe to the spraypad used to deliver the return (treated) water, this return pipe is acting potentially as a bypass for the treatment train. Based on the risk assessments performed it is recommended that the bypass pipe be removed from the treatment system since in doing so the probability of infection and illness were reduced appreciably. Secondarily including an ozone contactor was shown to slightly reduce the risk further and provide a multiple barrier.

Thermally activated building systems (TABS): Energy efficiency as a function of control strategy, hydronic circuit topology and (cold) generation system

By integrating the building structure as thermal energy storage into the building services concept, thermally activated building systems (TABS) have proven to be economically viable for the heating and cooling of buildings. Having already developed an integrated design method and various control concepts in the past, in the present paper the impact of different aspects of TABS regarding the energetic performance of such systems is analyzed. Based on a simulation case study for a typical Central European office building, the following conclusions can be drawn. The energy efficiency of TABS is significantly influenced by the hydronic circuit topology used. With separate zone return pipes energy savings of approximately 15–25 kW h/m 2 a, or 20–30% of heating as well as cooling demand, can be achieved, compared to common zone return pipes, where energy losses occur due to mixing of return water. A strong impact on energy efficiency can also be observed for the control strategy. Thus, by intermittent operation of the system using pulse width modulation control (PWM), the electricity demand for the water circulation pumps can be reduced by more than 50% compared to continuous operation. Concerning cold generation for TABS, it is shown that free cooling with a wet cooling tower is most efficient, if the cold source is the outside air. Variants with mechanical chillers exhibit 30–50% higher electricity demands for cold generation and distribution, even though their runtimes are much shorter compared to the cooling tower runtimes. In conclusion, the results show that significant energy savings can be achieved using adapted system topologies and applying appropriate control solutions for TABS.