scholarly journals Comparison of heat transfer performance of ZnO-PG, α-Al2O3-PG, and γ-Al2O3-PG nanofluids in car radiator

2019 ◽  
Vol 9 ◽  
pp. 184798041987646 ◽  
Author(s):  
XiaoRong Zhou ◽  
Yi Wang ◽  
Kai Zheng ◽  
Haozhong Huang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Propylene Glycol ◽  
Flow Rate ◽  
Volume Concentration ◽  
Maximum Heat ◽  
Cooling Performance ◽  
Maximum Heat Transfer ◽  
The Heat Transfer Coefficient

In this study, the cooling performance of nanofluids in car radiators was investigated. A car radiator, temperature measuring instrument, and other components were used to set up the experimental device, and the temperature of nanofluids passing through the radiator was measured by this device. Three kinds of nanoparticles, γ-Al2O3, α-Al2O3, and ZnO, were added to propylene glycol to prepared nanofluids, and the effects of nanoparticle size and type, volume concentration, initial temperature, and flow rate were tested. The results indicated that the heat transfer coefficients of all nanofluids first increased and then decreased with an increase in volume concentration. The ZnO-propylene glycol nanofluid reached a maximum heat transfer coefficient at 0.3 vol%, and the coefficient decreased by 25.6% with an increase in volume concentration from 0.3 vol% to 0.5 vol%. Smaller particles provided a better cooling performance, and the 0.1 vol% γ-Al2O3-propylene glycol nanofluid had a 19.9% increase in heat transfer coefficient compared with that of α-Al2O3-propylene glycol. An increase in flow rate resulted in a 10.5% increase in the heat transfer coefficient of the 0.5 vol% α-Al2O3-propylene glycol nanofluid. In addition, the experimental temperature range of 40–60°C improved the heat transfer coefficient of the 0.2 vol% ZnO-propylene glycol nanofluid by 46.4%.

Heat transfer characterization under radial jet and falling film induced rewetting

Kerntechnik ◽  
2021 ◽  
Vol 86 (5) ◽  
pp. 325-337
Author(s):  
M. Kumar ◽  
D. Mukhopadhyay
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Jet Impingement ◽  
Falling Film ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Fuel Pin

Abstract Empirical correlations are developed for rewetting velocity and maximum heat transfer coefficient during rewetting phase of single hot vertical Fuel Pin Simulator (FPS) by using radial jet impingement and falling film. Emergency Core Cooling System (ECCS) has been designed for Advance Heavy water Reactor (AHWR) to rewet the hot fuel pin under the loss of coolant accident. Coolant injection takes place from a water rod which is located at the center of the fuel bundle in form of jets to rewet hot surface of fuel pin under loss of coolant accident. This kind of design to reflood the fuel bundle is different than bottom and top spray reflooding practiced in PWR and BWR type of nuclear reactors. There are two different kinds of rewetting found during radial jet induced cooling. The first one is due to radial jet impingement and the second one is due to falling film which is below the jet impingement point. Rewetting velocity has been predicted along the length of fuel pin due to radial jet impingement cooling. Temperature of FPS has been varied from 400°C to 700°C with help of different powers supply, simulating decay heat of reactor. A variation of coolant radial jet mass flow rate is from 0.5 lpm to 1.8 lpm. It is considered during ECCS injection. It has been observed from the experiments that rewetting velocity decreases with increasing the clad surface temperature and increases with increasing the coolant mass flow rate. The rewetting velocity in falling film is found to be nearly 1.8 times higher than rewetting velocity predicted in circumferential direction. Further, it is found that maximum heat transfer coefficient increases with increasing the radial jet coolant mass flow rate. The maximum heat transfer coefficient in case of radial jet impingement is found to be nearly 1.5 times the falling film rewetting. Developed correlation predicts the maximum heat transfer coefficient with experimental data well within the error band of ±10%.

scholarly journals C INVESTIGATION OF HEAT TRANSFER COEFFICIENT AUGMENTATION IN DIVERGENT RECTANGULAR DUCT FOR TWO PHASES FLOW (AIR-WATER)

2020 ◽  
Vol 20 (2) ◽  
pp. 111-121
Author(s):  
Hadi O . Basher ◽  
Riyadh S Al-Turaihi ◽  
Ahmed A. Shubba
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Water Volume ◽  
Maximum Heat ◽  
Air Volume ◽  
The Heat Transfer Coefficient

In this project, the flow distribution for air and water, and the enhancement of the heattransfer coefficient are experimentally studied. Experimental studies have been performed totest the influence of discharge, pitch, the height of ribs at a constant heat flux on thetemperature and pressure distributions. Along the channel of the test and the heat transfercoefficient, the water volume flow rate was about (5-12 L/min), the air volume flow rate wasabout (5.83-16.66 L/min), and heat were (80, 100,120, watt). An experimental rig wasconstructed within the test whole system. On the other hands, the channel has a divergentsection with an angle =15o with vertical axis. The study included changing in the ribs heightby using three values (12, 15, 18 mm) and changing the ribs pitch into three values (5, 8, 10mm).The results indicated an increasing in the local heat transfer coefficient as a result ofincreasing the discharge. While there was an inverse influence for the temperature distributionalong the test channel which drops when the discharge rise. The results also confirm that theincreasing in the pitch distance leads to reduce the heat transfer coefficient. Increasing theribs height increases the coefficient of heat transfer. However, the experiment heat transfercoefficient improves about (15.6 %) when the water volume flow rate increased from (5 to 12L/min), and about (18.7%) when the air volume flow rate increased from (5.83 to 16.66L/min). The best heat transfer coefficient was about (35.6 %) which can be achieved whenthe pitch decreased from (10 to 5mm). The increasing of the height from (12 to 18) mmimproves the heat transfer coefficient about (11.2 %). The best rib dimension was 18 mmheight, and 5 mm pitch, which give a maximum heat transfer coefficient (1212.02 W/m2. oC).

Flow Boiling in a Heat Sink Embedded With Hexagonally Linked Minichannels

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Shubhankar Chakraborty ◽  
Omprakash Sahu ◽  
Prasanta Kr. Das
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Vapor Quality ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
The Heat Transfer Coefficient

The thermal hydraulic performance of a miniature heat sink during flow boiling of distilled water is presented in this article. The unique design of the heat sink contains a number of microchannels of 1 mm × 1 mm cross section arranged in a regular hexagonal array. The design facilitates repeated division and joining of individual streams from different microchannels and thereby can enhance heat transfer. Individual slug bubble experiences a typical route of break up, coalescence, and growth. The randomness of these processes enhances the transport of heat. With the increase of vapor quality the heat transfer coefficient increases, reaches the maximum value, and then drops. The maximum heat transfer coefficient occurs at an exit vapor quality much higher than that observed in conventional parallel microchannel heat sinks. Repeated redistribution of the coolant in the interlinked channels and the restricted growth of the slug bubbles may be responsible for this trend.

An Experimental Study of Heat Transfer Coefficient in a Bubble Flow throughout an Annulus Pipe Heated at Inner Wall

2014 ◽  
Vol 660 ◽  
pp. 654-658
Author(s):  
Sarjito ◽  
Sartono Putro ◽  
Nurmuntaha Agung Nugraha
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Rate ◽  
Volume Flow Rate ◽  
Research Work ◽  
Water Volume ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Water Mass Flow Rate

The aim of the research work describe in this paper is to investigate correlation of water, air massflow rate and calor fluks to heat transfer coefficient. The investigation was carried out toward a pipe section test developed from acrylic with diameter of 60 mm and 210 mm length, therefore, the buble can be easier to shoot. A concurrent water were flowed upward and air was injected from the bottom. The wall of the heater was heated using two thermocouple installed at the outer surfece of the heater. The fluid flow was measured using thermocouple installed along the annulus pipe. A heater with transparent tube diameter of 50 mm and 1800 mm length was also installed, and supplied with 1000 Watt electric power. Result of the experiment showed that heat transfer coefficient incresed along with the air massflow rate increased, and its decreased with the increasing of water mass flow rate. The maximum heat transfer coefficient of 4340,602 W/m2 °C at electric fluck calor of 29582,448 W/m2 was echieved on water volume flow rate of 3 lpm and 9 lpm of air volume rate.

scholarly journals Enhancement of Nucleate Pool Boiling Heat Transfer with Sodium Oleate

2017 ◽  
Vol 29 (1) ◽  
pp. 44-48
Author(s):  
KM Tanvir Ahmmed ◽  
Sultana Razia Syeda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Sodium Oleate ◽  
Surfactant Concentration ◽  
Chemical Engineering ◽  
Pool Boiling ◽  
Nucleate Pool Boiling ◽  
Maximum Heat ◽  
Maximum Heat Transfer

In this study saturated nucleate pool boiling of water with sodium oleate surfactant on a horizontal cylindrical heater surface has been investigated experimentally and compared with that of demineralized water. The concentration of sodium oleate in water was 100-300 ppm. The experimental results show that a small amount of surfactant enhances the heat transfer coefficient significantly. At low surfactant concentrations, heat transfer coefficient increases with increasing surfactant concentration in water. The maximum heat transfer enhancement is found to be at 250 ppm of sodium oleate solution. By adding more surfactant to water, heat transfer coefficient is found to be lowered. Surface tension of different concentration of sodium oleate solutions is measured. It is observed that the maximum heat transfer coefficient is obtained at a surfactant concentration that corresponds to the critical micelle concentration (cmc) of the sodium oleate solution.Journal of Chemical Engineering, Vol. 29, No. 1, 2017: 44-48

Effect of Liquid Properties on Phase-Change Heat Transfer in Porous Wick Structures

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Steve Q. Cai ◽  
Avijit Bhunia
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Mode Transition ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Phase Change Heat Transfer ◽  
The Heat Transfer Coefficient

In a heat pipe, operating fluid saturates wick structures system and establishes a capillary-driven circulation loop for heat transfer. Thus, the thermophysical properties of the operating fluid inevitably impact the transitions of phase-change mode and the capability of heat transfer, which determine both the design and development of the associated heat pipe systems. This article investigates the effect of liquid properties on phase-change heat transfer. Two different copper wick structures, cubic and cylindrical in cross section, 340 μm in height and 150 μm in diameter or width, are fabricated using an electroplating technique. The phase-change phenomena inside these wick structures are observed at various heat fluxes. The corresponding heat transfer characteristics are measured for three different working liquids: water, ethanol, and Novec 7200. Three distinct modes of the phase-change process are identified: (1) evaporation on liquid–vapor interface, (2) nucleate boiling with interfacial evaporation, and (3) boiling enhanced interface evaporation. Transitions between the three modes depend on heat flux and liquid properties. In addition to the mode transition, liquid properties also dictate the maximum heat flux and the heat transfer coefficient. A quantitative characterization shows that the maximum heat flux scales with Merit number, a dimensionless number connecting liquid density, surface tension, latent heat of vaporization, and viscosity. The heat transfer coefficient, on the other hand, is dictated by the thermal conductivity of the liquid. A complex interaction between the mode transition and liquid properties is reflected in Novec 7200. In spite of having the lowest thermal conductivity among the three liquids, an early transition to the mode of the boiling enhanced interface evaporation leads to a higher heat transfer coefficient at low heat flux.

scholarly journals Analysis of the effect of ultrasonic vibration on nanofluid as coolant in engine radiator

2021 ◽  
Vol 5 (5 (113)) ◽  
pp. 6-13
Author(s):  
Sudarmadji Sudarmadji ◽  
Santoso Santoso ◽  
Sugeng Hadi Susilo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Transfer Coefficient ◽  
Ultrasonic Vibration ◽  
Flow Rate ◽  
Volume Concentration ◽  
Aluminum Oxide Nanoparticles ◽  
Particle Volume ◽  
Overall Heat Transfer Coefficient

The paper discusses the combined methods of increasing heat transfer, effects of adding nanofluids and ultrasonic vibration in the radiator using radiator coolant (RC) as a base fluid. The aim of the study is to determine the effect of nanoparticles in fluids (nanofluid) and ultrasonic vibration on the overall heat transfer coefficient in the radiator. Aluminum oxide nanoparticles of 20–50 nm in size produced by Zhejiang Ultrafine powder & Chemical Co, Ltd China were used, and the volume concentration of the nanoparticles varied from 0.25 %, 0.30 % and 0.35 %. By adjusting the fluid flow temperature of the radiator from 60 °C to 80 °C, the fluid flow rate varies from 7 to 11 lpm. The results showed that the addition of nanoparticles and ultrasonic vibration to the radiator coolant increases the overall heat transfer coefficient by 62.7 % at a flow rate of 10 liter per minute and temperature of 80 °C for 0.30 % particles volume concentration compared to pure RC without vibration. The effect of ultrasonic vibration on pure radiator coolant without vibration increases the overall heat transfer coefficient by 9.8 % from 385.3 W/m2·°C to 423.3 W/m2·°C at a flow rate of 9 liter per minute at a temperature of 70 °C. The presence of particles in the cooling fluid improves the overall heat transfer coefficient due to the effect of ultrasonic vibrations, nanofluids with a volume concentration of 0.25 % and 0.30 % increased about 10.1 % and 15.7 %, respectively, compared to no vibration. While, the effect of nanoparticles on pure radiator coolant at 70 °C enhanced the overall heat transfer coefficient by about 39.6 % at a particle volume concentration of 0.35 % compared to RC, which is 390.4 W/m2·°C to 545.1 W/m2·°C at 70 °C at a flow rate of 10 liter per minute

scholarly journals Heat transfer in the vortex zone of a cyclone-bed chamber of furnace unit with fluidized bed

2019 ◽  
Vol 64 (1) ◽  
pp. 87-97
Author(s):  
E. A. Pitsuha ◽  
E. K. Buchilko ◽  
Yu. S. Teplitskii ◽  
D. S. Slizhuk
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Radial Direction ◽  
Air Flow ◽  
Air Flow Rate ◽  
Outlet Hole ◽  
The Heat Transfer Coefficient

An experimental investigation of the heat-transfer coefficient to a spherical probe in a cyclone-bed chamber with fluidized bed in the “cold” and “hot” regimes has been carried out. The heat-transfer coefficient was determined by the regular thermal regime. The dependences of the heat-transfer coefficient in the vortex-bed furnace on the various parameters: the diameter of the outlet hole, the air flow rate, the share of the bottom blast and the location of the probe were determined. It is revealed that in the “cold” regime the heat-transfer coefficient has practically constant value in the radial direction, it almost does not depend on the diameter of the outlet hole and the share of the bottom blast and depends significantly on the position of the probe along the height of the furnace and the air flow rate. The effect of flow swirling on the heat-transfer coefficient in a cyclone-bed chamber with fluidized bed is determined. When the fuel burns (“hot” regime), the heat-transfer coefficient is not constant in the radial direction and accept the maximum values in the central area of the chamber. At the same time, the part of conductive-convective component in the total heat-transfer coefficient to the spherical probe, depending on its radial position, is estimated at 40–70 %. The results can be used in the design and creation of modern high-efficiency furnaces for burning local solid biofuels.

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