Outlet Header Research Articles

Consumption management in water distribution systems by optimizing pressure reducing valves' settings using genetic algorithm

In this paper an optimization approach is presented to minimize pressure and consequently water consumptions in water distribution networks using Genetic Algorithm (GA) technique. To reduce water consumption a pressure management scheme is considered which uses pressure reducing valves (PRVs). When the PRV outlet head is reduced pressure is decreased in the down stream. This leads to reduction of all uncontrolled output flow from the system (e.g. leakage or sprinkler outlets) and the unwanted consumption by the ordinary customer which is usually happened by excess pressure in the system. In this procedure PRV outlet setting is decision variable of the optimization model. To evaluate pressure values of the system resulted from different PRV's settings an extended period head driven simulation program (EXPHDA) is prepared and is linked to the optimization model. Finally a test network is considered to apply the proposed methodology. It is shown that how much the real consumption is reduced when using the op...

RICE BRAN OIL EXTRACTION USING AN EXPELLER MACHINE

A study was carried out to test and evaluate the effect of screw speed, clearance outlet, and steaming process on the extraction efficiency of rice bran oil using a proto type expeller. Four screw speeds of (30, 50, 70, and 90 rpm ), four clearanceoutlets (0.2, 0.4, 0.6 and 0.8 mm ) and two different bran conditions (raw and stabilized) were studied and evaluated. Both raw and stabilized bran were steamed for 35 min using a laboratory scale steaming unit. The evaluation system based an: extraction efficiency, machine capacity, and percentage of free fatty acids (FFA) in the extracted oil. The results showed that, steaming process increased themoisture content of raw bran from an initial level of 12.05 % to a final level of 14.52 % w.b, while it increased from an initial level of 6.99 % w.b. to a final level of 12.67 w.b. for the stabilized bran. Moreover, during the expression process, the bran moisture content gradually decreased with the increase of screw speed and the decrease of outlet head clearance. Meanwhile, the percentage of extracted oil decreased with the increase of the expeller screw speed, and outlet head clearance. While, the expeller capacity increased with the increase of screw speed and the outlet head clearance. On the other hands, the steaming process increased the extraction efficiency for both raw and the stabilized bran. While, the steamed stabilized bran showed a slightly lower extraction efficiency in comparison with the steamed raw bran. On the same time, the stabilized steamed bran showed lower percentage of free fatty acids and more storage stability of the extracted oil in comparison with the steamed raw bran.

Thermal hydraulic investigations of intermediate heat exchanger in a pool-type fast breeder reactor

Intermediate heat exchanger (IHX) in a pool-type liquid metal cooled fast breeder reactor is an important heat exchanging component as it forms an intermediate boundary between the radioactive primary sodium in the pool and the non-radioactive secondary sodium in the steam generator (SG). The thermal loads during steady state and transient conditions impose thermal stresses on the heat exchanger tubes and on the shells which hold the tube bundle. Estimation of these thermal loads and achieving uniform temperature distribution in the tubes and shells by having uniform flow distributions are the major tasks of thermal hydraulic investigations of IHX. Through multi-dimensional thermal hydraulic investigations performed using commercially available computer codes such as PHOENICS, the flow and temperature distributions in the tubes and shells and in its secondary sodium inlet and outlet headers are obtained with and with out provisions of flow distribution devices. The effectiveness of these devices in achieving acceptably uniform flow and temperature distributions has been assessed and thermal loads on the tubes and shells for thermo mechanical analysis of the IHX have been defined. The predictions of the computational studies have been validated against simulated experiments.

Creep-Fatigue Properties of Fe-Ni Base Alloy HR6W for Piping in 700°C USC Power Plants

Creep-fatigue properties of HR6W, which is Fe-Ni base 0.08C-23Cr-45Ni-7W alloy for piping in 700°C USC power plants, are investigated at 700°C and compared with Ni base superalloy Alloy 617. The fatigue lives of HR6W and Alloy 617 are almost the same under PP (fast-fast) type strain waveform, but the life of HR6W is longer than that of Alloy 617 under CP (slow-fast) and CC (slow-slow) type strain waveforms. In the PP test of both HR6W and Alloy 617 the transgranular fracture is dominant. On the other hand, the intergranular fracture mainly occurred in the CP test. In particular, the intergranular cracking is observed in almost all areas of the fracture surface of Alloy 617, although the transgranular cracking is partly observed in the facture surface of HR6W. It is predicted by three-dimensional FE-analyses that the crack initiation life of HR6W at the ligament parts of superheater outlet headers in the boiler plant operating in the steam condition of 700°C-34.3MPa is longer than that of Alloy 617, because HR6W is superior to Alloy 617 in creep ductility and creep-fatigue properties.

Performance comparison of microchannel evaporators with refrigerant R-22

An experimental study on the performance comparison of microchannel evaporators with refrigerant R-22 was conducted. Six microchannel evaporators were designed and manufactured for a residential air-conditioner. They were tested with psychrometric calorimeter test facilities. The experiment was performed with both vapor compression system and refrigerant circulation system. Each evaporator was made up of two parallel flow heat exchangers connected with several return pipes. The parallel flow heat exchanger had 41 microchannel tubes inserted between inlet and outlet headers. The microchannel tube had 8 rectangular ports with the hydraulic diameter of 1.3 mm. For the vapor compression system, the flow area ratio and the number of return pipes had a great effect on the cooling capacity. Type 3 with a flow area ratio of 73% and 58% showed the best cooling capacity. It had 12 return pipes and 3 circuits. There is a merging manifold in it. The effect of the number of circuits and merging manifold on the cooling capacity was relatively small. For the refrigerant circulation system, the effect of the mass flow rate on the cooling capacity was slightly superior to that of inlet quality. The effect of the number of circuits on the cooling capacity was different from the result of the vapor compression system. The effect of merging manifold was negligible, which was consistent with the result of the vapor compression system. The cooling capacity proportionally increased as the vertical inclination angle of the evaporator increased due to gravity force.

Analysis of metastable regimes in a parallel channel single phase natural circulation system with RELAP5/MOD3.2

The objective of the present study is to assess the capability of RELAP5/MOD3.2 computer code to predict the metastable regime (multiple steady states) in a parallel channel system under natural circulation. To examine the basic behavior of such a system, an analysis was carried out for natural circulation flows in vertical multiple channel systems with non-uniform heat inputs. A three parallel channel configuration connected to common inlet and outlet headers with a down-comer, was investigated using RELAP5/MOD3.2 computer code. The results showed the existence of a metastable regime. It was seen that there are two steady state points for the same heat flux ratio differing in flow direction. Further the power level at which flow reversal occurs had been investigated. It was found that, if the power is increased in the down-flowing channel keeping the power of the other two channels constant, then it will start flowing up-wards only after reaching a critical value of power. Similarly, if the power of an up-flowing channel is decreased, it will start flowing down only after reaching another critical value of power. It was observed that the two critical values of power are not the same. It was found that the flow reversal power level depends upon the operating procedure, that is, rate of power rise or power set back. A non-dimensional heat flux ratio ( N H ) has been defined to predict the flow reversal in parallel channel system. The reason for flow reversal has also been investigated. It was observed that the flow directions in the natural circulation loop follow the maximum density (averaged) difference among the channels.

Thermalhydraulic Characteristics in Annular Pebble Beds with Axial and Radial Gas Flows

The purpose of this article is to determine the heat transfer and hydraulic drag in thin annular pebble beds with axial gas flow and investigate the flow distribution along annular pebble beds with radial flow. The experimental investigations showed that in thin annular pebble beds heat transfer values, equal to those for large (unlimited) pebble beds, could be achieved. The observed distributions of the radial flow in annular pebble beds demonstrated that regulation of flow distribution is possible by changing the permeability of the inner wall (outlet header) of the annular channel.

Enhancement of Safety Analysis Capability for a CANDU-6 Reactor Using RELAP-CANDU/SCAN Coupled Code System

The purpose of this study is the development and verification of the coupled code system SCAN and RELAP-CANDU for transient analysis of a Canada deuterium uranium (CANDU) reactor. For this purpose, a spatial kinetics calculation module is developed and implemented in SCAN, a three-dimensional (3-D) CANDU–pressurized heavy water reactor neutronics design and analysis code. Then, a dynamic linked library of the SCAN code is generated for the integration with RELAP-CANDU.The RELAP-CANDU code has been developed for best-estimate transient simulation of CANDU reactor coolant systems based on the RELAP5 code. The SCAN code is a 3-D neutronic calculation code, which is composed of both unified nodal methods based on coarse-mesh finite difference method solutions to the time-dependent two-group diffusion equations.To verify the reliability of the coupled code system RELAP-CANDU/SCAN, the 40% reactor inlet header break accident, the 100% reactor outlet header break accident, and the pump suction pipe break are analyzed. The proposed coupled thermal-hydraulic and neutronic analyses methodology shows that there is an important margin in the traditional accident analysis.

Two-Phase Flow Distribution and Pressure Drop in Microchannel Tubes Under Non-Heating and Heating Conditions

The present study investigated two-phase flow distribution and pressure drop in microchannel tubes under non-heating and heating conditions using R-22. The test section consisted of inlet and outlet headers with the inner diameter of 19.4 mm and had 15 or 41 parallel microchannel tubes. Each microchannel tube had 8 rectangular ports with hydraulic diameter of 1.3 mm. For non-heating condition, the key experimental parameters were orientation of the header, flow direction of refrigerant into the inlet header, and inlet quality. For heating condition, the key experimental parameters were inclination angle, mass flow rate, and inlet quality. It was found that the effect of the orientation of the header on the two-phase flow distribution and pressure drop was the largest under the non-heating condition. Two-phase pressure drops through the microchannel tubes with the horizontal header were higher than those of the microchannel tubes with the vertical header due to the gravitational effect. Under the heating condition, the cooling capacities of three prototype evaporators were changed as the mass flow rate and inlet quality were increased due to the flow mal-distribution.

Progress of the DUPIC Fuel Compatibility Analysis—III: Reactor Safety

The compatibility of the direct use of spent pressurized water reactor fuel in Canada deuterium uranium (CANDU) reactor (DUPIC) fuel with the existing 713-MW(electric) CANDU (CANDU-6) reactor has been analyzed for large-break loss-of-coolant-accident (LOCA) scenarios such as a 55% pump suction break, a 35% reactor inlet header break, and a 100% reactor outlet header break. The compatibility was assessed for the fuel integrity against the stored energy and the radiation environmental effect resulting from the large-break LOCA. The analysis showed that the stored energy of the DUPIC fuel was below the fuel breakup energy by 32%. The environmental effect was estimated for the personal and public doses using the radiation source term obtained from one-fourth of the fission product inventory in the fuel gap of the CANDU-6 reactor, being steadily operated at full power. The analyses have shown that both the personal and population doses are below the design limits even for a postulated dual failure such as a complete loss of containment building isolation logic.

The Core Characteristics of a LOCA Power Pulse in a CANDU-6 Reactor with the CANFLEX-RU Fuel

The power pulse characteristics following a large loss-of-coolant accident have been analyzed for a Canada deuterium uranium (CANDU)-6 reactor core fueled with a CANDU flexible fueling recovered uranium fuel. The coupled simulations for the reactor physics and channel thermal-hydraulics phenomena are done using the RFSP and CATHENA codes. The 55% pump suction, 35% reactor inlet header, and 100% reactor outlet header breaks were selected. From the analysis results, it is known that the shutoff rods have enough reactivity for a reactor shutdown and to maintain it at a subcriticality state. Even with the highest power pulse, which occurred in a 100% reactor outlet header break, the fuel temperature was maintained below the fuel melting temperature. The summation of the initial stored energy and the transient pulse energy of the hottest fuel pin has a minimum 17% margin for the fuel breakup.

사이드채널형 재생펌프의 성능 특성에 관한 실험적 연구

The performance of a regenerative pump is affected by many parameters, especially blade shape of impeller, leakage flow iii the clearance and head losses at the inlet & outlet. An impeller with J-shape blade was designed and 5 times scale up model was tested at similarity conditions to evaluate the performance Performance variations with clearance change were executed The amounts of leakage flow through the clearance were estimated using the one-dimensional leakage flow models and analysis. Main leakage flow is generated through the gap between the impeller and casing. The inlet & outlet head losses were also estimated such corrections are very important to evaluate the final performance of the impeller and pump. Cavitation test was also performed at 1,200 rpm NPSH of the regenerative pump was obtained and growth of cavity within blades was visualized.

MASS FLOW RATE DISTRIBUTION AND PHASE SEPARATION OF R-22 IN MULTI-MICROCHANNEL TUBES UNDER ADIABATIC CONDITION

The present study investigated mass flow rate distribution and phase separation of R-22 in multi-microchannel tubes under adiabatic condition. The test section consisted of inlet and outlet headers with the inner diameter of 19.4 mm and 15 parallel multi-microchannel tubes. Each microchannel tube had 8 rectangular ports with hydraulic diameter of 1.32 mm. The key experimental parameters were the orientation of the header (horizontal and vertical), flow direction of refrigerant into the inlet header (in-line, parallel and cross flow), and inlet quality (0.1, 0.2, and 0.3). The effect of inlet quality on the mass flow rate distribution and phase separation in the microchannel tubes was negligible. The effect of the orientation of the header on the mass flow rate distribution and phase separation was the largest among the test parameters. Horizontal header showed better mass flow rate distribution and phase separation characteristics than vertical header. Both parallel and cross-flow conditions showed better mass flow rate distribution and phase separation than in-line flow condition.

Experimental and analytical investigations on core flow distribution and pressure distribution in the outlet header of a PHWR : Chandraker, D. K. et al. Experimental Thermal and Fluid Science, 2002, 27, (1), 11–24

Experimental and analytical investigations on core flow distribution and pressure distribution in the outlet header of a PHWR : Chandraker, D. K. et al. Experimental Thermal and Fluid Science, 2002, 27, (1), 11–24

Dynamic Fracture Toughness and Charpy Transition Properties of a Service-Exposed 2.25Cr-1Mo Reheater Header Pipe

Residual life analysis of power plant components like boiler tubes, superheater outlet headers, reheater headers, steam pipes, etc., is important for life extension and avoidance of catastrophic failure. In this context, fracture toughness is very important. The fracture characteristics after prolonged exposure to high temperatures and pressures are likely to be different from that of the virgin material. 2.25Cr-1Mo reheater header pipe exposed at 813 K for 120,000 h was studied by instrumented impact tests (IIT) to evaluate dynamic fracture toughness and Charpy transition properties. The methods presented in this paper for estimating dynamic fracture toughness from IIT of Charpy specimens give reliably conservative results without the need for precracking. For estimating fracture appearance transition temperature (FATT) from IIT load-time traces, the equation for percent shear fracture, PSF3, gives the best 1:1 correlation with measured values from fracture surfaces. The lower bound equation for variation of fracture toughness with temperature derived in the present study is higher than that obtained from the FATT master curve (FATT-MC) approach. Comparison of Charpy indices like FATT and upper-shelf energy for the service exposed steel to results for the virgin material reported in the literature and the compositional J-Factor estimates for temper-embrittlement susceptibility indicate that the present steel, even after 120,000 h exposure to high temperature service, has probably undergone only very little or nil degradation in toughness properties.

Experimental and analytical investigations on core flow distribution and pressure distribution in the outlet header of a PHWR

The Indian pressurised heavy water reactor (PHWR) comprises of a number of horizontal channels containing nuclear fuel bundles. The parallel channels are connected to headers at the inlet and outlet through feeder pipes. The flow distribution between the channels of the PHWR is an important aspect of the design of the core and primary heat transport system. A correct determination of the channel flow distribution is required to evaluate the thermal safety margin. The estimation of the design flow rate in the channels is based on the assumption that the pressure in each header is uniform. Moreover, in the reactor core only sixteen channels out of the 306 channels are provided with flow metering elements. An analytical model has been developed to enable a better prediction of the flow distribution between the different channels and the variation of pressure in the outlet header. The flow rates in the channels and the pressure distribution in the outlet header are predicted from the solution of two first order differential equations (pressure-flow equation set) involving the flow rate and the pressure difference across the headers. The outlet header is divided into four basic combining flow manifolds and an iterative procedure has been adopted to satisfy the flow and pressure conditions at each junction point between two successive manifolds by solving the pressure-flow equation set for each manifold. The model adopted for the analytical studies has been validated against experimental data. The experimental studies were carried out on a one-fourth scale model to determine the channel flow distribution in the reactor core and the pressure distribution in the outlet header at different flow rates, with (i) both the steam generating (SG) branches open and (ii) one of the steam generator branches closed. Air was used as the test fluid. The measured flow distribution in the test model has been compared with the theoretically obtained flow distribution. The pressure variations in the outlet header for different modes of pump operation are compared. The analytical results for the flow distribution are in excellent agreement with the experimental data. Analysis is also performed for the prototype reactor header using the validated model for different modes of pump operation. The analytically obtained results are compared with the plant data.

Crack propagation life prediction of a perforated plate under thermal fatigue

Superheater outlet headers of boilers are well known to be subjected to the cycling of high pressure and high thermal stress during plant operations. Thermal stresses during cyclic operation are generally severest on the inside surface of the ligaments between the stub-tube holes, where many examples of ligament cracking due to thermal fatigue have been found recently. A method to predict the crack propagation life of the ligaments of boiler headers under thermal fatigue has been required. Firstly in this paper, to model the crack propagation behavior of the ligament regions of boiler headers, a perforated plate of normalized and tempered 2 1/4Cr–1Mo steel was examined under out-of-phase thermal fatigue at a maximum temperature of 600°C in the air. Inelastic analysis of the perforated plate under thermal fatigue was carried out, and the nonlinear fracture mechanics parameters such as the J and C ∗ integral were obtained by the line integral for observed cracks. A simplified method was proposed for predicting these parameters under displacement-controlled conditions such as thermal fatigue. In this method, the change of the macroscopic stress–strain relation of the perforated plate with propagating cracks was combined with the reference stress concept under displacement-controlled conditions. The predicted fracture mechanics parameters from this method coincided well with those from the inelastic analysis. The prediction of the crack propagation life on the basis of the proposed method provided a good correspondence with the test results of the perforated plate under thermal fatigue.

Microstructural evolution in seven 2.25Cr–1Mo superheater outlet headers resulting from service exposure

Seven 2.25Cr–1 Mo superheater outlet headers with service exposures ranging from as fabricated through to 190 kh (21.7 years) have been examined using analytical TEM. Parent plate, heat affected zone, and weld regions have been characterised to understand the influence of service exposure on the microstructure and the carbide make-up. Post-weld stress relief heat treatment in a virgin header produced a starting microstructure devoid of M3C, and consisting of M7C3 and M23C6 in the bainite and M2C in the ferrite. Service induced aging produced coarsening of M2C and the development of denuded zones along prior austenite grain boundaries. The carbide compositions in the bainite shifted towards thermodynamically stable phases, rich in Mo and Cr. One header exhibited anomalous behaviour; parent plate compositional effects may have contributed to this, along with fabrication and/or operational differences. Most of the individual carbide phases studied were found to undergo compositional changes with parabolic kinetics. These microstructural and compositional changes may find application in the assessment of effective time at temperature.

Some applications of analytical TEM to the characterisation of high temperature equipment

Much of the high temperature refinery and power generation equipment currently in use in Australia is typically quite old. In many cases plant has been operating for over 20 years, and in a few cases, for 40+ years. Understanding and predicting the behaviour of service-exposed equipment, which has operated at high temperatures and pressures for extended periods, requires a detailed understanding of the material microstructures and properties. Remaining life assessment of aged plant brings to bear a raft of techniques to measure mechanical properties and to look for damage effects. Analytical transmission electron microscopy (AEM), while not a traditional tool for looking at such problems, can provide some useful insights into the microstructural degradation processes which can occur during service, such as carbide coarsening, secondary precipitation and transformation. This paper will highlight some of the potentially useful information which AEM can provide, along with some of its limitations, with reference to refiner pressure vessels, turbine generating rotors, and superheater outlet headers.

Measurements of heat transfer in microchannel heat sinks

The paper presents new experimental measurements for pressure drop and heat transfer coefficient in microchannel heat sinks. Tests were performed with devices fabricated using standard Silicon 100 wafers. Two different channel patterns were studied. The parallel pattern distributed the fluid through several parallel passages between the inlet and the outlet headers located at two ends of the wafer. The series pattern carried the fluid through a longer winding channel between the inlet and the outlet headers. Channels of different depths (or aspect ratios) were studied. Tests were carried out using water as the working fluid. The fluid flow rate as well as the pressure and temperature of the fluid at the inlet and outlet of the device, and temperature at several locations in the wafer were measured. These measurements were used to calculate local and average Nusselt number and coefficient of friction in the device for different flow rate, channel size, and channel configuration.