scholarly journals Modes of Circulation in an Inverted U-Tube Array With Condensation

1982 ◽  
Vol 104 (4) ◽  
pp. 769-773 ◽  
Author(s):  
C. Calia ◽  
P. Griffith
Keyword(s):  
Heat Transfer ◽  
Steam Generator ◽  
Flow Rate ◽  
Pressure Difference ◽  
Operating Conditions ◽  
Steam Generators ◽  
Modes Of Operation ◽  
Glass Tubes ◽  
Abnormal Operating Conditions ◽  
Plenum Pressure

An experiment and analysis was performed on an inverted U-tube steam condenser (similar to a steam generator) to determine the modes of flow that can exist as the rate of steam flow into the condenser is reduced. The condenser consisted of four glass tubes connected to a common inlet plenum and a common exit plenum. Heat-transfer and flow-rate measurements, as well as visual observations were made. Four different modes of operation were identified. Noncondensables were found to substantially alter the plenum to plenum pressure difference and aid flow stability. Satisfactory analytical descriptions of the observations have been developed as well as application of the results to the condensing behavior of nuclear steam generators under abnormal operating conditions.

Management of PWR Steam Generator Tube Plugging and Primary Flow-Rate Predictions

2011 ◽  
Author(s):  
Olivier Brunin
Keyword(s):  
Steam Generator ◽  
Flow Rate ◽  
Exchange Capacity ◽  
Operating Conditions ◽  
Steam Generators ◽  
Primary Flow ◽  
The Real ◽  
Term Operation ◽  
Tube Plugging

The tubes of PWR steam generators are part of the second barrier between the nuclear fuel and the environment. The integrity in operation of the tubes is addressed with Non Destructive Examinations (NDE) and flaw allowances criteria. If a tube does not match the criteria, it is plugged. As a consequence, the steam generators tube plugging (SGTP) may increase during the maintenance outages. This increase has to be managed properly because it basically affects the heat exchange capacity of the Nuclear Steam Supply System (NSSS). This can be managed by performing long-term predictions in order to prepare in advance the possibility of steam generator replacements. But this “long-term operation” management is to be completed with an intermediate term management considering the real operating conditions of the NSSS. Intermediate term predictions, based on a simulation of the mechanisms leading to the degradation of the tubes, are annually compared with the evolution of real NDE and real SGTP. These predictions are completed with the set-up of a model, for each Reactor Coolant System (RCS), considering the relation between the average SGTP and the primary flow-rate. The predictions are used to check that the real operating conditions of each NSSS can be matched with an existing safety file.

scholarly journals A Numerical Analysis of the Air-Cooling System of a Spark Ignition Aeronautical Engine

2020 ◽  
Vol 197 ◽  
pp. 06003
Author(s):  
Maria Faruoli ◽  
Annarita Viggiano ◽  
Paolo Caso ◽  
Vinicio Magi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling System ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Air Cooling ◽  
Air Mass ◽  
Air Cooling System

It is well known that spark ignition internal combustion engines for aeronautical applications operate within a specific temperature range to avoid structural damages, detonations and loss of efficiency of the combustion process. An accurate assessment of the cooling system performance is a crucial aspect in order to guarantee broad operating conditions of the engine. In this framework, the use of a Conjugate Heat Transfer method is a proper choice, since it allows to estimate both the heat fluxes between the engine walls and the cooling air and the temperature distribution along the outer wall surfaces of the engine, and to perform parametric analyses by varying the engine operating conditions. In this work, the air-cooling system of a 4-cylinder spark ignition engine, designed by CMD Engine Company for aeronautical applications, is analysed in order to evaluate the amount of the air mass flow rate to guarantee the heat transfer under full load operating conditions. A preliminary validation of the model is performed by comparing the results with available experimental data. A parametric study is also performed to assess the influence of the controlling parameters on the cooling system efficiency. This study is carried out by varying the inlet air mass flow rate from 1.0 kg/s to 1.5 kg/s and the temperature of the inner wall surfaces of the engine combustion chambers from 390 K to 430 K.

Power Rising and Descending Transient for the OTSG of a Small PWR

2020 ◽  
Author(s):  
Baihui Jiang ◽  
Zhiwei Zhou ◽  
Zhaoyang Xia ◽  
Qian Sun
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Flow Stability ◽  
Phase Flow ◽  
Steam Generators ◽  
Two Phase ◽  
Water Reactors ◽  
Secondary Side

Abstract As key heat transfer system in small and medium size pressurized water reactors, once-through steam generators are important parts of energy exchange between primary and secondary circuits, and are very important for the design and operation of reactors. However, two-phase flow and heat transfer in once-through steam generators are very complicated. When a reactor experience power rising and descending transient, the heat removal of once-through steam generator, the flow rate, the inlet fluid temperature and outlet steam temperature will all change accordingly. Especially when a reactor is running at a low power, the flow rate of the secondary side of OTSG is extremely small and the single-phase region of the secondary side of OTSGs is also too small. The two-phase flow instability may occur, which has a serious impact on reactor operation and safety. So, a reasonable power-up and power-down transient scheme is required to ensure operational stability when starting up and shutting down a reactor. RELAP5/MOD4.0 is a commercial software developed by Innovative System Software, LCC for transient analysis of light water reactors (LWR). After years of development and improvement, RELAP5 has been a basic tool for analysis and calculation of various simulators of nuclear power plants. Scholars all over the world have carried out a large number of analysis of two-phase flow stability using RELAP5, and the results are reliable. This paper takes once through steam generators with given structural parameters as the research object, and uses RELAP5 as the calculation tool. The influencing factors of flow instability are discussed in this paper, and the operating parameters of the fluid on the primary and secondary sides are designed to satisfy the flow stability under different powers. And a set of power-up and power-down schemes for stable operation is proposed.

Experimental Investigation of Spray Cooling Heat Transfer on Circular Grooved Surface

2017 ◽  
Author(s):  
Azzam S. Salman ◽  
Jamil A. Khan
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
Target Surface ◽  
Spray Cooling ◽  
Operating Conditions ◽  
Low Flow ◽  
Inlet Temperature ◽  
Flow Rates

An experimental study was conducted in a closed loop spray cooling system working with deionized water as a cooling medium, to investigate the effects of surface modification on the spray cooling heat transfer enhancement in the single-phase region. Plain copper surface with diameter 1.5 cm and an enhanced surface with circular grooves were tested under different operating conditions. The volumetric flow rate of the coolant ranged from 115 mL/min to 177 mL/min., and the water inlet temperature was kept between 21–23 °C. Also, the distances between the nozzle and the target surface were varied at 8, 10, and 12 mm respectively. The results show that the distance between the nozzle and the target surface did not have a significant effect on the heat transfer performance for the low flow rates, while it has a slight effect on high flow rates for both surfaces. Also, increasing the liquid volumetric flow rate increases the amount of heat removed, and the heat transfer coefficient for both surfaces. Moreover, the maximum enhancement ratios achieved were 23.4% and 31% with volumetric flow rates of 153 mL/min, and 177 mL/min respectively.

Detection of Cavitation in a Venturi Injector With a Combined Method of Strain Gauges and Numerical Simulation

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Yuncheng Xu ◽  
Yan Chen ◽  
Jianqiang He ◽  
Haijun Yan
Keyword(s):  
Flow Rate ◽  
Pressure Difference ◽  
Volume Fraction ◽  
Operating Conditions ◽  
Strain Gauges ◽  
Maximum Pressure ◽  
Operating Pressure ◽  
Average Growth ◽  
Rate Of Increase ◽  
Suction Flow

The fertilizer suction capability of a Venturi injector is dependent on the vacuum pressure in the throat portion. As the vacuum level drops below the saturation vapor pressure, the pressure decreases to a particular value corresponding to the maximum pressure difference (Δpmax) between inlet and outlet pressures, and critical cavitation is likely to occur, leading to an unstable suction flow rate and low fertilization uniformity. A new method of using strain gauges to detect cavitation in Venturi injectors was explored experimentally and verified numerically under various operating conditions. The standard deviation (SD) of the measured strain values and the simulated values of the vapor-phase volume fraction (Vf) were used to evaluate the influence of cavitation. The results showed that both the rate of increase (ηm) of the average SD and the average growth rate (AGR) of the simulated cavitation length reach relatively large values at the maximum pressure difference (Δpmax), where the measured suction flow rate simultaneously reaches a maximum. In addition, SD and Vf shared similar variation trends at pressure differences larger than the corresponding Δpmax under various conditions. This new cavitation detection method has been proved to be feasible and reliable. It helps to determine accurately the value of Δpmax at different inlet pressures and to ensure that the Venturi injector runs in a safe operating-pressure range.

scholarly journals Effects of Louvered Parameters on Exergetic Performance of Louvered Finned Solar Air Heater

2021 ◽  
Vol 39 (5) ◽  
pp. 1649-1658
Author(s):  
Subhash Chand ◽  
Prabha Chand
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Operating Conditions ◽  
High Mass ◽  
Solar Air Heater ◽  
Air Heater ◽  
Pitch Ratio ◽  
Exergy Performance

The aim of the present study to improve the performance of solar air heater because of low thermo-physical properties of air. In the current work, an attempt has been made to improve the performance of the heater by employing louvered fins to the absorber plate, as it not only enhances heat transfer coefficient but also improve heat transfer area. The effect of exergy performance on the geometrical parameters of louvered fin i.e., louvered angle, louvered pitch and louvered length has been studied and analyzed. The results are compared to plane solar air heater (PSAH) to evaluate the effectiveness of louvered finned solar air heater (LFSAH). The exergy efficiency of LFSAH is comparatively higher for all the operating conditions except for higher mass flow rate where it may even go below that of PSAH; possibly due to the higher pressure drop and more loss of exergy at high mass flow rate. In addition, the results conclude that for louvered parameters viz., louvered angle 20°, fin pitch to louvered pitch ratio 0.75 and louvered length to louvered pitch ratio 1.25, high exergy performance of SAH is obtained as compared to other louvered parameter values.

scholarly journals Experimental Studies of the Heat Exchange Between the Water Film and the Casting Roller in the Thermal Preconditioning Chamber

2021 ◽  
pp. 42-46
Author(s):  
Alexander Pereselkov ◽  
Olga Kruglyakova
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Flow Rate ◽  
Large Diameter ◽  
Experimental Studies ◽  
Water Film ◽  
Scientific Paper ◽  
Operating Conditions ◽  
Hot Water ◽  
Thermal Preparation

When the casting roller is cooled or heated in the preconditioning chamber the water is supplied to its surface by flat-jet nozzles. The visual inspection of the model of the casting roller showed that a considerable part of it can be covered with the water film spreading from sprinkling zones. It was established that the heat conductivity in the roller body is considered to be a crucial thermal preparation factor in the conjugate heat-exchange problem for the roller of a large diameter at Bio criterion values exceeding 20. Hence, it is sufficient to provide an essential level of the heat transfer that corresponds to the heat transfer coefficient of 2000 W/(m2∙K) to provide appropriate operating conditions for the thermal preparation of the roller. The conditions are also met in sprinkling zones. Due to this fact this scientific paper studies the heat exchange conditions under the water film that spreads between the adjacent sprinkling zones. A range of changes in the flow rate of the spreading water film was determined experimentally. The conditions of heat exchange between the surface of alpha-calorimeter and the water film were analyzed depending on its flow rate and the heat meter surface temperature. A generalized correlation equation was derived. It was established that the heat exchange intensity in sprinkling zones and under the spreading water film meets technological roller treatment conditions in the preconditioning chambers. The obtained research data can be used for the rational arrangement of the collectors and flat-jet nozzles in casting roller preconditioning chambers to reduce the cold and hot water consumption and cut down operating costs.

Effects of Tube Rupture Modeling Methods on MSSV Lift Time Following a MSGTR Event in PWR

2002 ◽  
Author(s):  
Ji Hwan Jeong ◽  
Ki Yong Choi ◽  
Keun Sun Chang
Keyword(s):  
Steam Generator ◽  
Flow Rate ◽  
Pressurized Water Reactor ◽  
Steam Generators ◽  
Pressurized Water ◽  
Coolant Pump ◽  
Best Estimate ◽  
Main Steam ◽  
Safety Systems ◽  
Estimate System

A multiple steam generator tube rupture (MSGTR) event in APR1400, an advanced pressurized water reactor, is investigated using the best estimate thermal hydraulic system code, MARS1.4. The effects of parameters such as the number of ruptured tubes, rupture location, affected steam generator on analysis of the MSGTR event in APR1400 are taken into account. In particular, the effects of tube rupture modeling are compared. In the present study, single tube (STM) and double tube modeling (DTM) are examined for assessment on the main steam safety valve (MSSV) lift time. Nuclear steam supply system (NSSS) and several safety systems that are relevant to the APR1400 are modeled. Automatic safety systems are assumed to mitigate the MSGTR events including the reactor protection trip, reactor coolant pump trip, the pressurizer heaters, high-pressure safety injection (HPSI) pumps, and the valves for atmospheric dump, main steam safety, main steam isolation, and turbine stop and bypass. When five tubes are ruptured, the STM permits the operator response time of 2085 seconds before lifting of MSSVs. The effects of rupture location on the MSSV lift time is not significant in case of STM, while the MSSV lift time for tube-top rupture is found to be 25.3% larger than that for rupture at hog-leg side tube sheet in case of DTM. The MSSV lift time for the cases that both steam generators are affected (4C5x, 4C23x) are found to be larger than that for the single steam generator cases (4A5x, 4B5x) due to a bifurcation of the primary leak flow. The discharge coefficient of Cd is found to affect the MSSV lift time only for smaller value of Cd below 0.5. For larger values of Cd than 0.5, its effect on the leak flow rates as well as the MSSV lift time become negligible. It is found that the most dominant parameter governing the MSSV lift time is the leak flow rate. Whichever modeling method is used, it gives the similar MSSV lift time if the leak flow rate is similar, except the case of both steam generators are affected. Therefore, the system performance and the MSSV lift time of the APR1400 are strongly dependent on the break flow model used in the best estimate system code.

Structural Integrity Role in Plant Life Extension - A Case Study

2015 ◽  
Vol 750 ◽  
pp. 295-306
Author(s):  
Jin Hua Shi
Keyword(s):  
Steam Generator ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Operating Conditions ◽  
Life Extension ◽  
Guide Tube ◽  
Gas Temperature ◽  
Steam Generators ◽  
Steam Generator Tube ◽  
The Uk

The steam generators at Advanced Gas-Cooled Reactor (AGR) nuclear power stations in the UK are potentially life-limiting components. Enhancing the capability to monitor the steam generators has been identified as having the potential to provide key evidence in justifying the extension of the generating lifetime of the stations. It has been proposed to install new temperature measuring instrumentation to monitor reactor gas temperature and to provide additional data regarding steam generator operating conditions. The modification will be to introduce thermocouples to the bore of an intact steam generator tube to facilitate temperature measurement at or near to the locations of interest. The modified steam generator tube will be sealed at the feed header upstand. Between the upper surface of the superheater header tubeplate and the wall of the superheater header, the thermocouple bundle and sheath will be contained within a rigid stainless steel guide tube. The guide tube will be attached at both ends by welds, each forming a pressure boundary. At the tubeplate a weld will separate the bore of the sealed guide tube from the steam space within the superheater header; a weld between the guide tube and the superheater header will separate the steam space within the superheater header from atmosphere outside the header. In order to obtain a better design, three 3-dimentional finite element models have been created using ABAQUS. A series of cyclic pressure, and start-up and shutdown thermal transient stress analyses have been carried out to provide stress values for structural integrity assessments to be conducted using ASME III, Subsection NH and R5.

Experimental Investigation of Water Flow Heat Transfer in Metal Foams

2012 ◽  
Vol 189 ◽  
pp. 290-294 ◽  
Author(s):  
Tao Sun ◽  
Shi Bu ◽  
Yue Han Xu ◽  
Zhong Yi Wang
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Dissipation ◽  
Metal Foam ◽  
Cooling System ◽  
Electric Heating ◽  
Equilibrium Temperature ◽  
Metal Foams ◽  
Operating Conditions ◽  
Micro Pump

This paper aims at finding the best pore density and porosity of metal foams for heat transfer, as well as the most proper operating conditions. A circulating water cooling system were designed which include micro-channel heat sink, heat exchanger, micro-pump, rot meter, electric heating rods, and conversion fans for the experiment. The comparison was made between different metal foam samples in terms of flow rate and equilibrium temperature of heating boundary. The results presented that a relatively low temperature can be achieved when flow rate is large, but at the same time the pressure drop increased. The excellent heat dissipation performance of metal foams has a close relationship with its specific surface area.

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