Impacts of Water Flow Rate on Freezing Prevention of Air-Cooled Heat Exchangers in Power Plants

In this paper, a Gamma type Stirling engine is experimented. A special care was given to the heat exchangers instrumentation. Different set of experimental measurement were made on them. Their corresponding thermal energy and efficiencies are estimated. Three operation parameters are chosen: filling pressure, cooling water flow rate and heating temperature. The influence of these parameters on the performance of each heat exchanger are presented and explained. It can be concluded that all heat exchangers parameters are critical to the performance of the Stirling engine. The regenerator performances are the most significant for the engine. The heating temperature is the parameter that greatly affects performance of heat exchangers. The cooling water flow rate is quite affecting the Cooler efficiency but has a slight influence on other exchangers. The initial filling pressure is significant for the regenerator and for the heater.

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To Combine or Not To Combine An In-Depth Review of Standard and Combined Hydronic Systems and Their Various Pitfalls

Journal of the National Academy of Forensic Engineers ◽

10.51501/jotnafe.v10i2.517 ◽

1993 ◽

Vol 10 (2) ◽

Author(s):

Edward W. Saltzberg

Keyword(s):

Water Flow ◽

Flow Rate ◽

Heat Exchangers ◽

Water Flow Rate ◽

Heating System ◽

Hot Water ◽

Space Heating ◽

System Pressure ◽

Hot Water Supply ◽

Heating Boiler

A hydronic heating system is simply a piping arrangement conveying hot water to heat exchangers in order to provide space heating. A conventional hydronic heating system usually delivers hot supply water at 180 to 200 Fahrenheit temperature and has a dedicated space heating boiler. The hot water return temperature is usually about 140 Fahrenheit, meaning a 40 to 60 temperature difference between supply and return. The conventional hydronic heating system has a relatively constant circulated water flow rate and the temperature of the delivered hot water supply can be reset from outside air temperature. The water flow balancing of a conventional hydronic heating system is somewhat straightforward, although quite critical. The pipe sizing is determined on the basis of gallons per minute flow rate, the selected system pressure drop, and the maximum prudent velocity for the specific piping material. The circulating pump is selected on the basis of the required gallons per minute

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Analysis of Loss-of-Flow Accidents in Pre-Cooler and Inter-Cooler of HTR-10GT

ASME 2018 Nuclear Forum ◽

10.1115/nuclrf2018-7381 ◽

2018 ◽

Author(s):

Xiaoyong Yang ◽

Xiao Li ◽

Jie Wang ◽

Youjie Zhang

Keyword(s):

Water Temperature ◽

Water Flow ◽

Flow Rate ◽

Heat Exchangers ◽

Power Conversion ◽

Water Flow Rate ◽

Inlet Temperature ◽

Brayton Cycle ◽

Reactor Inlet ◽

Conversion System

Closed Brayton cycle (CBC) coupled with High Temperature Gas-cooled Reactor (HTGR) has potential application due to its compact configuration, high power generation efficiency and inherent safety. It is also one of the major power conversion methods for Generation IV advanced nuclear power systems. The typical CBC has several helium-water heat exchangers, including pre-cooler and inter-cooler. These helium-water heat exchangers have important influence on the performance of power conversion system, especially in loss-of-flow accidents (LOFAs). A system model including the reactor and the energy conversion system was established in this paper. The 10MW High Temperature Gas-cooled reactor-test Module helium Gas Turbine (HTR-10GT) was taken as the example to show the consequences of LOFAs. The results showed that LOFAs led to the rising of water temperature out of heat exchangers. With the reduction of water flow rate, the maximum water temperature would increase sharply, and the water temperature in pre-cooler was higher than that in inter-cooler. At low water flow rate, the water temperature would exceed the boiling point. LOFAs also made the rising of helium temperature. It had impacts on the performance of helium compressors. The elevated inlet temperature of helium compressors changed the corrected speed and corrected flow rate, therefore caused the deterioration of compressor’s performance. Furthermore, the LOFAs caused the reactor inlet temperature increasing. In low water flow rate, it would make the reactor inlet temperature beyond the temperature limitation of reactor pressure vessel and influence the safety of reactor. And the LOFAs also reduced the output work of cycle. This paper provides insights of features of CBC in LOFAs and will be helpful to the design and safety operation of closed Brayton cycle coupled with HTGR.

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Evaluation Analysis of Double Coil Heat Exchanger for Heat Transfer Enhancement

Diyala Journal of Engineering Sciences ◽

10.24237/djes.2021.14109 ◽

2021 ◽

Vol 14 (1) ◽

pp. 96-107

Author(s):

Itimad Dawood Jumaah ◽

Senaa Kh. Ali ◽

Anees A. Khadom

Keyword(s):

Heat Exchanger ◽

Water Flow ◽

Flow Rate ◽

Heat Exchangers ◽

Water Flow Rate ◽

Hot Water ◽

Outlet Temperature ◽

Single Coil ◽

Coil Heat Exchanger ◽

Coil Heat

In order to maximize the thermal efficiency of shell and coil heat exchangers, substantial research has been done and geometrical modification is one way to improve the exchange of thermal energy between two or more fluids. One of the peculiar features of coiled geometry is that the temperature distribution is highly variable along the circumferential section due to the centrifugal force induced in the fluid. Moreover, most researchers are concentrated on using a shell and single helical coil heat exchanger to enhance the heat transfer rate and thermal efficiency at different operating parameters. Therefore, the aim of this study is to investigate temperature variation ((T-1, T-2, T-3 and T-4) across a shell and single/double coil heat exchanger at different coil pitches, hot water flow rate, and cold-water flow rate along the outer surface of the coil using experimental and numerical analysis. For single and double coil heat exchangers, Computational Fluid Dynamics (CFD) is carried out using pure water with a hot water flow rate ranging between 1-2 l/min for the coil side heat exchanger. For single coil heat exchangers, the numerical analysis findings showed a good agreement with experimental four-temperature measurement results (T-1, T-2, T-3 and T-4) with an error rate of 1.80%, 3.05%, 5.34% and 2.17% respectively. Moreover, in the current double coil analysis, the hot outlet temperature decreased by 3.07% compared to a single coil (baseline case) at a 2.5L/min hot water flow rate. In addition, increasing the coil pitch will increase the contact between the hot fluid and the coil at a constant hot water flow rate and thereby decrease the hot fluid outlet temperature. Finally, a computational analysis was carried out to examine the flow structure inside single and double coil heat exchangers, and the findings indicated that the effect of centrifugal forces in double coil heat exchangers at various coil pitches caused the secondary flow to be substantially reduced.

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Effect of Water Flow on Underwater Wet Welded A36 Steel

Metals ◽

10.3390/met11050682 ◽

2021 ◽

Vol 11 (5) ◽

pp. 682

Author(s):

Eko Surojo ◽

Aziz Harya Gumilang ◽

Triyono Triyono ◽

Aditya Rio Prabowo ◽

Eko Prasetya Budiana ◽

...

Keyword(s):

Mechanical Properties ◽

Water Flow ◽

Flow Rate ◽

Water Flow Rate ◽

Physical And Mechanical Properties ◽

Shielded Metal Arc Welding ◽

Effect Of Water ◽

Bending Effect ◽

Metal Arc Welding ◽

A36 Steel

Underwater wet welding (UWW) combined with the shielded metal arc welding (SMAW) method has proven to be an effective way of permanently joining metals that can be performed in water. This research was conducted to determine the effect of water flow rate on the physical and mechanical properties (tensile, hardness, toughness, and bending effect) of underwater welded bead on A36 steel plate. The control variables used were a welding speed of 4 mm/s, a current of 120 A, electrode E7018 with a diameter of 4 mm, and freshwater. The results show that variations in water flow affected defects, microstructure, and mechanical properties of underwater welds. These defects include spatter, porosity, and undercut, which occur in all underwater welding results. The presence of flow and an increased flow rate causes differences in the microstructure, increased porosity on the weld metal, and undercut on the UWW specimen. An increase in water flow rate causes the acicular ferrite microstructure to appear greater, and the heat-affected zone (HAZ) will form finer grains. The best mechanical properties are achieved by welding with the highest flow rate, with a tensile strength of 534.1 MPa, 3.6% elongation, a Vickers microhardness in the HAZ area of 424 HV, and an impact strength of 1.47 J/mm2.

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Experimental Characterization of a Modified Airlift Pump

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-39899 ◽

2014 ◽

Author(s):

Afshin Goharzadeh ◽

Keegan Fernandes

Keyword(s):

Water Flow ◽

Flow Rate ◽

High Speed ◽

Water Flow Rate ◽

High Speed Photography ◽

Two Phase ◽

Inner Diameter ◽

Airlift Pump ◽

Flow Map ◽

Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

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