scholarly journals Experimental and numerical evaluation of thermodynamic effect on NACA0015 hydrofoil cavitation in hot water

2021 ◽  
Author(s):  
Anh Dinh Le
Keyword(s):  
Flow Behavior ◽  
Temperature Drop ◽  
Hot Water ◽  
Maximum Temperature ◽  
Flow Conditions ◽  
Thermodynamic Effect ◽  
Pressure Water ◽  
Phase Change Phenomena ◽  
Temperature Depression ◽  
Effect Phase

In this study, the cavitation in hot water, which implies tight interaction of thermodynamic effect, phase change phenomena, and flow behavior, was studied by a combination of experiment and numerical simulation. The experiment in water up to 90°C was performed in the high temperature and high-pressure water tunnel with NACA0015 as a cavitator. The temperature inside the cavity was measured using the high-accuracy thermistor probe. According to the result, the temperature depression in the cavity was increased proportionally with the increase of freestream temperature. The inverse thermodynamic effect was observed with the increase of cavity length when temperature increased. The maximum temperature depression of about 0.41°C was measured in the water at around 90°C. The temperature drop was reasonably captured in simulation by coupling our simplified thermodynamic model with our cavitation model and governing equations. The tendency of temperature depression in the cavity agreed well with experimental data under different flow conditions.

Study of Thermodynamic Effect On the Mechanism of Flashing Flow Under Pressurized Hot Water by a Homogeneous Model

2021 ◽  
Author(s):  
Anh Dinh Le
Keyword(s):  
Numerical Method ◽  
Saturated Vapor ◽  
Homogeneous Model ◽  
Temperature Drop ◽  
Numerical Data ◽  
Hot Water ◽  
Two Phase ◽  
Suppression Effect ◽  
Flow Parameters ◽  
Thermodynamic Effect

Abstract The flashing flow in a Moby_Dick converging-diverging nozzle under pressurized hot water from 460.5 K to 483.5 K is simulated using a homogeneous compressible water-vapor two-phase flow model. The kinematic and thermodynamic mass transfer are accessed using the cavitation model based on the Hertz-Knudsen-Langmuir equation. Our simplified thermodynamic model is coupled with the governing equations to capture the phase-change heat transfer. This numerical method proved its reliability through a comparison with available experimental data of flow parameters inside the nozzle. Consequently, the present numerical method shows good potential for simulating the flashing flow under pressurized hot water conditions. The satisfying prediction of averaged flow parameters with a slight improvement compared to reference numerical data is reproduced. The results confirm a noticeable impact of the thermodynamic effect on the mechanism of flashing flow, resulting in a considerable decrease in the flow temperature and the saturated vapor pressure. The flashing non-equilibrium is significantly decreased, forcing the flashing flow to be classified as the usual cavitation behavior and better suited to homogeneous model. While the temperature drop is highly dependent on evaporation, the thermodynamic suppression is influenced by the condensation. The suppression effect, unobserved in water at a lower temperature in previous studies, is noticeable for the pressurized hot water flow characterized by the cavitation mechanism. The vapor void fraction decreased considerably in the radial and axial directions as the water temperature rose to 483.5 K in this study.

Thermodynamic Effect on Cavitation in High Temperature Water

2014 ◽  
Author(s):  
Yuki Yamaguchi ◽  
Yuka Iga
Keyword(s):  
High Temperature ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Cryogenic Fluids ◽  
Hydraulic Machinery ◽  
High Temperature Water ◽  
Thermodynamic Effect ◽  
Naca 0015 ◽  
Temperature Depression ◽  
Temperature Water

Thermodynamic effect on cavitation appears in cryogenic fluids, refrigerant and high temperature water. The thermodynamic effect is considered to suppress the development of cavitation and improve the performance of hydraulic machinery. However, the actual appearance degree of thermodynamic effect depends on not only thermal property of each fluid but also each hydraulic machinery and its operating condition. So, the clarification of the influence of the flow field with unsteady cavitation on the degree of thermodynamic effect is necessary. In order to investigate thermodynamic effect, many experiments had been conducted with using cryogenic fluids or refrigerant as working fluids. However, there are some difficulties to visualize cryogenic fluids and the experimental results cannot be directly correlated to the condition without thermodynamic effect in same fluid. In the present study, in order to conduct cavitation experiments with and without thermodynamic effect in same fluid, high temperature and high pressure cavitation tunnel had been constructed. The working fluid of this tunnel is water and the free-stream temperature can be varied from room temperature to 140 °C. In the present study, NACA 0015 hydrofoil had been chosen as a cavitator. The extent of thermodynamic effect was estimated through the measurement of temperature in the cavity. The temperature was measured by a thermistor probe which has high accuracy. When the thermodynamic effect appears, temperature depression in the cavity is observed. The maximum temperature depression of cavity about 0.3 K had been measured in water of 80 °C.

scholarly journals Thermal Injuries Caused by Water from Loose Garden Hoses

2021 ◽  
Vol 8 ◽  
pp. 2333794X2110312
Author(s):  
Karolína Uhrová ◽  
Pavel Böhm
Keyword(s):  
Human Skin ◽  
Air Temperature ◽  
Concrete Surface ◽  
Hot Water ◽  
Maximum Temperature ◽  
Water Contact ◽  
Valid Data ◽  
Thermal Injuries

This is a monitoring research, the purpose of which is to point out the danger of scalding with water from loose garden hoses. All the stated data are the result of this research, which occurred during the month of August. To adequately compare the maximum temperature that the water reaches in garden hoses exposed to sunlight, 2 different surfaces were chosen, namely grass and concrete. It has been found that water in garden hoses, which lie in a place exposed to sunlight, is able to reach temperatures at which, in case of contact with human skin, there is a risk of scalding. The results confirmed the assumption that the temperature in the grass will be lower in the hoses than in the concrete surface. At an air temperature of 35°C, the water in the hoses on the grass reached a temperature of up to 47.3°C. On a concrete surface at an air temperature of 28.5°C, the water in the hoses reached 49.8°C. There is a risk of scalding from such hot water contact with the skin, and especially with sensitive baby skin. The aim of this research is to provide valid data on the risk of spilling hyperthermic water in free-lying garden hoses exposed to sunlight. The threat of scalding can occur unknowingly or through negligence, the risk of scalding with such water increases during tropical days significantly.

Experimental investigation of degassing properties of geothermal fluids

2021 ◽  
Author(s):  
Chris Boeije ◽  
Pacelli Zitha ◽  
Anne Pluymakers
Keyword(s):  
High Pressure ◽  
Temperature Drop ◽  
Hot Water ◽  
Visual Cell ◽  
Dissolved Gas ◽  
Bubble Point ◽  
Free Gas ◽  
Bubble Point Pressure ◽  
Geothermal Fluids ◽  
Point Pressure

<p>Geothermal energy, the extraction of hot water from the subsurface (500 m to 5 km deep), is generally considered one of the key technologies to achieve the demands of the energy transition.  One of the main problems during production of geothermal waters is degassing. Many subsurface waters contain substantial amounts of dissolved gasses. As the hot water travels up the production well, the pressure and/or temperature drop will cause dissolved gas to come out of the solution. This causes several problems, such as corrosion of the facilities (due to pH changes and/or degassing-related precipitation) and in some cases even to blocking of the reservoir as the free gas limits the water flow.  To better understand under which conditions free gas nucleates, we need confirmation of theoretical bubble point pressure and temperature, and understand what controls the evolution of the bubble front:  i.e. what are the conditions under which free gas emerges from the solution and at what rate are bubbles created?</p><p>An experimental setup was designed in which the degassing process can be observed visually. The setup consists of a high-pressure visual cell which contains water saturated with dissolved gas at high-pressure. The pressure within the cell can be reduced in a reproducible manner using a back-pressure regulator at the outlet of the system. A high-speed camera paired with a uniform LED light source is used to record the degassing process. The pressure in the cell is monitored using a pressure transducer which is synchronized with the camera. The resulting images are then analysed using a MATLAB routine, which allows for determination of the bubble point pressure and rate of bubble formation.</p><p>The first two sets of experiments at ambient temperatures (~20 <sup>o</sup>C) were carried out using two different gases, N<sub>2</sub> and CO<sub>2</sub>. Initial pressure was 70 and 30 bar for the N<sub>2</sub> and CO<sub>2</sub> experiments respectively. In these first experiments we determined the influence of the initial fluid used to pressurize the system. Using gas as the initial fluid causes a large amount of bubbles, whereas only a single bubble was observed for a system where degassed water is used as the initial fluid. An intermediate system where degassed water is pumped into a system full of air at ambient conditions and is subsequently pressurized yields a number of bubbles in between the two systems described previously. All three methods give reproducible bubble point pressures within 2 bar (i.e. pressure where the first free bubble is formed). There are clear differences in bubble point between N<sub>2</sub> and CO<sub>2</sub>.</p><p>A series of follow-up experiments is planned that will investigate specific properties at more extreme conditions: at higher pressures (up to 500 bar) and temperatures (500 <sup>o</sup>C) and using high-salinity brines (2.5 M).</p>

scholarly journals Performance Analysis and Design Optimization of Shell and Tube Heat Exchangers

2021 ◽  
Author(s):  
praveen math
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Fluid Flows ◽  
Hot Water ◽  
Flow Conditions ◽  
Shell Side ◽  
Shell And Tube ◽  
Side Flow

Abstract Shell and Tube heat exchangers are having special importance in boilers, oil coolers, condensers, pre-heaters. They are also widely used in process applications as well as the refrigeration and air conditioning industry. The robustness and medium weighted shape of Shell and Tube heat exchangers make them well suited for high pressure operations. The aim of this study is to experiment, validate and to provide design suggestion to optimize the shell and tube heat exchanger (STHE). The heat exchanger is made of acrylic material with 2 baffles and 7 tubes made of stainless steel. Hot fluid flows inside the tube and cold fluid flows over the tube in the shell. 4 K-type thermocouples were used to read the hot and cold fluids inlet and outlet temperatures. Experiments were carried out for various combinations of hot and cold water flow rates with different hot water inlet temperatures. The flow conditions are limited to the lab size model of the experimental setup. A commercial CFD code was used to study the thermal and hydraulic flow field inside the shell and tubes. CFD methodology is developed to appropriately represent the flow physics and the procedure is validated with the experimental results. Turbulent flow in tube side is observed for all flow conditions, while the shell side has laminar flow except for extreme hot water temperatures. Hence transition k-kl-omega model was used to predict the flow better for transition cases. Realizable k- epsilon model with non-equilibrium wall function was used for turbulent cases. Temperature and velocity profiles are examined in detail and observed that the flow remains almost uniform to the tubes thus limiting heat transfer. Approximately 2/3 rd of the shell side flow does not surround the tubes due to biased flow contributing to reduced overall heat transfer and increased pressure loss. On the basis of these findings an attempt has been made to enhance the heat transfer by inducing turbulence in the shel l side flow. The two baffles were rotated in opposite direction to each other to achieve more circulation in the shell side flow and provide more contact with tube surface. Various positions of the baffles were simulated and studied using CFD analysis and th e results are summarized with respect to heat transfer and pressure loss.

ELECTRIC BUNTING TO MAINTAIN BODY TEMPERATURE DURING EXCHANGE TRANSFUSION IN THE NEWBORN INFANT

PEDIATRICS ◽  
1951 ◽  
Vol 7 (2) ◽  
pp. 207-209
Author(s):  
P. VOGEL ◽  
R. E. ROSENFIELD ◽  
M. STEINBERG
Keyword(s):  
Body Temperature ◽  
Exchange Transfusion ◽  
Prolonged Exposure ◽  
Newborn Infants ◽  
Electric Heating ◽  
Hot Water ◽  
Maximum Temperature ◽  
Ideal Situation ◽  
The Many ◽  
Water Proof

THE maintenance of proper body temperature has been a serious problem in the performance of exchange transfusions on newborn infants suffering from hemolytic disease. Many of these infants are in such poor condition that extreme care in their handling is required, including incubation, oxygen and tracheal aspiration. The many procedures necessary create the hazard of prolonged exposure to room temperature, and a number of deaths may have resulted directly or indirectly from hypothermia. In the Children's Hospital in Boston, the entire exchange transfusion is carried out with the infant lying in a Hess bed; this is an ideal situation which undoubtedly is not readily available in most institutions where an exchange transfusion must be performed. The maintenance of body temperature with electric heating pads and/or hot water bottles has proved cumbersome and unsatisfactory, and has resulted in a number of burns, particularly about the buttocks. A washable electric blanket bunting has been designed (see Figs. and 2) to maintain the temperature of newborn infants throughout the procedure of an exchange transfusion, as well as for a period following the procedure, if a heated crib is not available. This bunting was constructed by the General Electric Company using water-proof washable material and employing the principles of the commercial electric blanket. The bunting can be regulated to any desired temperature although the maximum temperature obtainable is 42°C., which avoids the possibility of skin burns. The design of the bunting is simple: it is a bag with a zipper along one side to allow for easy insertion and removal of the baby, and a "U" shaped zippered flap which can be opened to provide a window at the approximate position of the umbilical cord.

scholarly journals Nonlinear Flow Behavior in Packed Beds of Natural and Variably Graded Granular Materials

2019 ◽  
Vol 131 (3) ◽  
pp. 957-983 ◽  
Author(s):  
J. H. van Lopik ◽  
L. Zazai ◽  
N. Hartog ◽  
R. J. Schotting
Keyword(s):  
Grain Size ◽  
Granular Materials ◽  
Flow Behavior ◽  
Nonlinear Flow ◽  
Packed Beds ◽  
Size Distributions ◽  
Flow Conditions ◽  
Grain Size Distributions ◽  
Sand And Gravel ◽  
Nonlinear Flow Behavior

AbstractUnder certain flow conditions, fluid flow through porous media starts to deviate from the linear relationship between flow rate and hydraulic gradient. At such flow conditions, Darcy’s law for laminar flow can no longer be assumed and nonlinear relationships are required to predict flow in the Forchheimer regime. To date, most of the nonlinear flow behavior data is obtained from flow experiments on packed beds of uniformly graded granular materials (Cu = d60/d10 < 2) with various average grain sizes, ranging from sands to cobbles. However, natural deposits of sand and gravel in the subsurface could have a wide variety of grain size distributions. Therefore, in the present study we investigated the impact of variable grain size distributions on the extent of nonlinear flow behavior through 18 different packed beds of natural sand and gravel deposits, as well as composite filter sand and gravel mixtures within the investigated range of uniformity (2.0 < Cu < 17.35) and porosity values (0.23 < n < 0.36). Increased flow resistance is observed for the sand and gravel with high Cu values and low porosity values. The present study shows that for granular material with wider grain size distributions (Cu > 2), the d10 instead of the average grain size (d50) as characteristic pore length should be used. Ergun constants A and B with values of 63.1 and 1.72, respectively, resulted in a reasonable prediction of the Forchheimer coefficients for the investigated granular materials.

scholarly journals Determining the Effect of Inlet Flow Conditions on the Thermal Efficiency of a Flat Plate Solar Collector

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 67 ◽  
Author(s):  
Mohammad Alobaid ◽  
Ben Hughes ◽  
Andrew Heyes ◽  
Dominic O’Connor
Keyword(s):  
Flat Plate ◽  
Thermal Efficiency ◽  
Solar Collector ◽  
Maximum Temperature ◽  
Inlet Temperature ◽  
Flow Conditions ◽  
Riser Pipe ◽  
Computational Fluid Dynamics Cfd ◽  
Flat Plate Solar Collector ◽  
Feed Temperature

The main objective of this study was to investigate the effect of inlet temperature (Tin) and flowrate ( m ˙ ) on thermal efficiency ( η t h ) of flat plate collectors (FPC). Computational Fluid Dynamics (CFD) was employed to simulate a FPC and the results were validated with experimental data from literature. The FPC was examined for high and low level flowrates and for inlet temperatures which varied from 298 to 373 K. Thermal efficiency of 93% and 65% was achieved at 298 K and 370 K inlet temperature’s respectively. A maximum temperature increase of 62 K in the inlet temperature was achieved at a flowrate of 5 × 10−4 kg/s inside the riser pipe. Tin and m ˙ were optimised in order to achieve the minimum required feed temperature for a 10 kW absorption chiller.

Vacuum Cooling of Cooked Mussels (Perna perna)

2006 ◽  
Vol 12 (1) ◽  
pp. 19-25 ◽  
Author(s):  
E. Huber ◽  
L. P. Soares ◽  
B. A. M. Carciofi ◽  
H. Hense ◽  
J. B. Laurindo
Keyword(s):  
Weight Loss ◽  
Cold Water ◽  
Temperature Drop ◽  
Relative Weight ◽  
Cooling Water ◽  
Hot Water ◽  
Process Time ◽  
Promising Alternative ◽  
Industrial Processing ◽  
Vacuum Cooling

Mussels pass through a thermal treatment during industrial processing with hot water or steam and then are pre-cooled before the manual extraction of the meat. This pre-cooling is classically accomplished by the immersion of the cooked mussels in cold water. In this work, vacuum cooling of mussels after the cooking stage was used as a technique to quickly decrease the product temperature and to avoid a possible microbial contamination by the cooling water or by manipulation. In about 3 minutes, mussels were cooled from about 90 °C to 20 °C. The relative weight loss during the vacuum cooling of the whole sample (meat and shell) was about 8% of the initial sample’s weight, for temperatures drop cited above. In this way, there was a 8.7 0.26 °C temperature drop for each 1% of weight loss. For separated meat (without shell), the ratio was 7.5 0.30 ºC per 1% weight loss, which agreed with the literature for vacuum cooling of meats in general. A simple numerical simulation was able to determine weight loss during the vacuum cooling process, providing data that agreed very well with experimental results. The vacuum cooling technique is a promising alternative for processing pre-cooked mussels, because process time is shortened and cross-contamination risk is significantly reduced in the cooling stage. The water loss is not a serious problem when the cooled mussels are canned in brine.

Measurements of Sheath Temperature Profiles in Bruce LVRF Bundles Under Post-Dryout Heat Transfer Conditions in Freon

2006 ◽  
Author(s):  
Y. Guo ◽  
D. E. Bullock ◽  
I. L. Pioro ◽  
J. Martin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Uranium ◽  
Outer Ring ◽  
Maximum Temperature ◽  
Experimental Program ◽  
Uniform Heat Flux ◽  
Flow Conditions ◽  
Channel Power ◽  
Ring Element

An experimental program has been completed to study the behaviour of sheath wall temperatures in the Bruce Power Station Low Void Reactivity Fuel (shortened hereafter to Bruce LVRF) bundles under post-dryout (PDO) heat-transfer conditions. The experiment was conducted with an electrically heated simulator of a string of nine Bruce LVRF bundles, installed in the MR-3 Freon heat transfer loop at the Chalk River Laboratories (CRL), Atomic Energy of Canada Limited (AECL). The loop used Freon R-134a as a coolant to simulate typical flow conditions in CANDU® nuclear power stations. The simulator had an axially uniform heat flux profile. Two radial heat flux profiles were tested: a fresh Bruce LVRF profile and a fresh natural uranium (NU) profile. For a given set of flow conditions, the channel power was set above the critical power to achieve dryout, while heater-element wall temperatures were recorded at various overpower levels using sliding thermocouples. The maximum experimental overpower achieved was 64%. For the conditions tested, the results showed that initial dryout occurred at an inner-ring element at low flows and an outer-ring element facing internal subchannels at high flows. Dry-patches (regions of dryout) spread with increasing channel power; maximum wall temperatures were observed at the downstream end of the simulator, and immediately upstream of the mid-bundle spacer plane. In general, maximum wall temperatures were observed at the outer-ring elements facing the internal subchannels. The maximum water-equivalent temperature obtained in the test, at an overpower level of 64%, was significantly below the acceptable maximum temperature, indicating that the integrity of the Bruce LVRF will be maintained at PDO conditions. Therefore, the Bruce LVRF exhibits good PDO heat transfer performance.

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