scholarly journals Pengaruh Variasi Insulator Saluran Chilled Water Terhadap Performansi Prototype Mini Water Chiller

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Buddhi Satya Utama ◽  
I Nyoman Pasek Nugraha ◽  
I Gede Wiratmaja
Keyword(s):  
Cooling Rate ◽  
Polyurethane Foam ◽  
High Heat ◽  
Nitrile Rubber ◽  
Water Pipe ◽  
Optimal Temperature ◽  
High Heat Transfer ◽  
Dependent Variables ◽  
Chilled Water ◽  
The Right

The high heat transfer rate from the environment to the chilled water pipe will affect the performance of the mini water chiller prototype, so it is necessary to insulate the chilled water pipe using the right insulator to optimize the performance of the mini water chiller prototype. Therefore, this study aims to determine the effect of the chilled water pipe insulator variations: nitrile rubber expanded and polyurethane foam on the optimal temperature and cooling rate of the mini water chiller prototype cabin. The method used in this study is an experimental method with a variation of the insulator as independent variables and the optimal temperature also cooling rate of the mini water chiller prototype cabin as the dependent variables. The testing process was carried out 20 times repetition of data collection on each variation using a stopwatch, thermo gun, thermostat, ampere pliers, a bulb, and a water heating element as a tool in research. In addition, it expanded nitrile rubber and polyurethane foam spray as research material. The results obtained from this study showed that the average optimal temperature achievement of the mini water chiller prototype with polyurethane foam insulator was 11.242◦C, and with the nitrile rubber expanded insulator was 11.250◦C. Otherwise, the average cooling rate of the mini water chiller prototype cabin with polyurethane foam insulator variation was 0.001421◦C, while in the variation of nitrile rubber expanded it was 0.001032◦C, which indicates that there is an effect of chilled water pipe insulator variations on the performance of the mini water chiller prototype.

Influence of tip clearance and cavity depth on heat transfer in a cutback squealer tip

2020 ◽  
pp. 095441002096469
Author(s):  
Weijie Wang ◽  
Shaopeng Lu ◽  
Hongmei Jiang ◽  
Qiusheng Deng ◽  
Jinfang Teng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Suction Side ◽  
High Heat ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Trailing Edge ◽  
Cavity Depth ◽  
High Heat Transfer ◽  
Blade Tip ◽  
High Heat Transfer Coefficient

Numerical simulations are conducted to present the aerothermal performance of a turbine blade tip with cutback squealer rim. Two different tip clearance heights (0.5%, 1.0% of the blade span) and three different cavity depths (2.0%, 3.0%, and 6.0% of the blade span) are investigated. The results show that a high heat transfer coefficient (HTC) strip on the cavity floor appears near the suction side. It extends with the increase of tip clearance height and moves towards the suction side with the increase of cavity depth. The cutback region near the trailing edge has a high HTC value due to the flush of over-tip leakage flow. High HTC region shrinks to the trailing edge with the increase of cavity depth since there is more accumulated flow in the cavity for larger cavity depth. For small tip clearance cases, high HTC distribution appears on the pressure side rim. However, high HTC distribution is observed on suction side rim for large tip clearance height. This is mainly caused by the flow separation and reattachment on the squealer rims.

Pressure Distributions in the Tip Clearance Region of an Unshrouded Axial Turbine as Affecting the Problem of Tip Burnout

1987 ◽  
Author(s):  
Jeffery P. Bindon
Keyword(s):  
Separation Bubble ◽  
Low Pressure ◽  
High Heat ◽  
Tip Clearance ◽  
Small Scale ◽  
Narrow Strip ◽  
Pressure Surface ◽  
High Heat Transfer ◽  
Axial Turbines ◽  
Secondary Vortices

The pressure distribution in the tip clearance region of a 2D turbine cascade was examined with reference to unknown factors which cause high heat transfer rates and burnout along the edge of the pressure surface of unshrouded cooled axial turbines. Using a special micro-tapping technique, the pressure along a very narrow strip of the blade edge was found to be 2.8 times lower than the cascade outlet pressure. This low pressure, coupled with a thin boundary layer due to the intense acceleration at gap entry, are believed to cause blade burnout. The flow phenomena causing the low pressure are of very small scale and do not appear to have been previously reported. The ultra low pressure is primarily caused by the sharp flow curvature demanded of the leakage flow at gap entry. The curvature is made more severe by the apparent attachement of the flow around the corner instead of immediately separating to increase the radius demanded of the flow. The low pressures are intensified by a depression in the suction corner and by the formation of a separation bubble in the clearance gap. The bubble creates a venturi action. The suction corner depression is due to the mainstream flow moving round the leakage and secondary vortices.

Possible Mechanisms for Thermal Conductivity Enhancement in Nanofluids

2006 ◽  
Author(s):  
Amit Gupta ◽  
Xuan Wu ◽  
Ranganathan Kumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Brownian Dynamics ◽  
Lattice Vibration ◽  
Experimental Studies ◽  
High Heat ◽  
Conductivity Enhancement ◽  
High Heat Transfer ◽  
Dynamics Simulations

This study discusses the merits of various physical mechanisms that are responsible for enhancing the heat transfer in nanofluids. Experimental studies have cemented the claim that ‘seeding’ liquids with nanoparticles can increase the thermal conductivity of the nanofluid by up to 40% for metallic and oxide nanoparticles dispersed in a base liquid. Experiments have also shown that the rise in conductivity of the nanofluid is highly dependent on the size and concentration of the nanoparticles. On the theoretical side, traditional models like Maxwell or Hamilton-Crosser models cannot explain this unusually high heat transfer. Several mechanisms have been postulated in the literature such as Brownian motion, thermal diffusion in nanoparticles and thermal interaction of nanoparticles with the surrounding fluid, the formation of an ordered liquid layer on the surface of the nanoparticle and microconvection. This study concentrates on 3 possible mechanisms: Brownian dynamics, microconvection and lattice vibration of nanoparticles in the fluid. By considering two nanofluids, copper particles dispersed in ethylene glycol, and silica in water, it is determined that translational Brownian motion of the nanoparticles, presence of an interparticle potential and the microconvection heat transfer are mechanisms that play only a smaller role in the enhancement of thermal conductivity. On the other hand, the lattice vibrations, determined by molecular dynamics simulations show a great deal of promise in increasing the thermal conductivity by as much as 23%. In a simplistic sense, the lattice vibration can be regarded as a means to simulate the phononic transport from solid to liquid at the interface.

A Photographic Study of Flow Boiling Stability on a Plain Surface With Tapered Manifold

2015 ◽  
Author(s):  
Ankit Kalani ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Bubble Nucleation ◽  
High Heat Transfer ◽  
Plain Surface ◽  
High Heat Transfer Coefficient

Flow boiling in microchannels offers many advantages such as high heat transfer coefficient, higher surface area to volume ratio, low coolant inventory, uniform temperature control and compact design. The application of these flow boiling systems has been severely limited due to early critical heat flux (CHF) and flow instability. Recently, a number of studies have focused on variable flow cross-sectional area to augment the thermal performance of microchannels. In a previous work, the open microchannel with manifold (OMM) configuration was experimentally investigated to provide high heat transfer coefficient coupled with high CHF and low pressure drop. In the current work, high speed images of plain surface using tapered manifold are obtained to gain an insight into the nucleating bubble behavior. The mechanism of bubble nucleation, growth and departure are described through high speed images. Formation of dry spots for both tapered and uniform manifold geometry is also discussed.

Impact of Stefan blowing and magnetic dipole on bio-convective flow of Maxwell nanofluid over a stretching sheet

2021 ◽  
pp. 095440892110581
Author(s):  
A. Alhadhrami ◽  
Hassan A. H. Alzahrani ◽  
B. M. Prasanna ◽  
N. Madhukeshwara ◽  
K. C. Rajendraprasad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Brownian Motion ◽  
Magnetic Dipole ◽  
Stretching Sheet ◽  
High Heat ◽  
Hard Drives ◽  
Linear System Of Equations ◽  
High Heat Transfer ◽  
Non Linear System ◽  
The Impact

The features of ferromagnetic fluids make it supportive for an extensive usage in loudspeakers, magnetic resonance imaging, computer hard drives, directing of magnetic drug and magnetic hyperthermia. Owing to all such potential applications, the current investigation is to understand the relationship between the thermal distribution, magnetic field and resulting fluid flow of Maxwell liquid over a stretching sheet. Investigation of thermal energy and concentration is carried out in the presence of thermal radiation, non-uniform heat sink/source, chemical reaction, Stefan blowing, magnetic dipole, thermophoresis and Brownian motion. Also, microorganisms are considered just to stabilize the suspended nanoparticles. Boundary layer approximation is employed during mathematical derivation. Based on a new constitutive relation, the governing equations are formulated and are reduced into a coupled non-linear system of equations using appropriate transformations. Further, these equations are solved numerically using fourth-order Runge–Kutta method with shooting technique. The impact of involved parameters is discussed and analysed graphically. Outcomes disclose that Newtonian liquid shows high heat transfer when compared to non-Newtonian (Maxwell) liquid for increased values of Brownian motion and thermophoresis parameters. Increased values of Peclet number declines the rate of gyrotactic microorganisms. Finally, an increase in Brownian and thermophoresis motion parameters declines the rate of heat transfer.

Heat Transfer Characteristics of a Flow Passage With Long Pin Fins and Improving Heat Transfer Coefficient by Adding Turbulence Promoters on a Endwall

2001 ◽  
Author(s):  
K. Takeishi ◽  
T. Nakae ◽  
K. Watanabe ◽  
M. Hirayama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
High Heat ◽  
Atmospheric Conditions ◽  
Pin Fin ◽  
High Heat Transfer ◽  
Turbine Vanes ◽  
Pin Fins

Pin fins are normally used for cooling the trailing edge region of a turbine, where their aspect ratio (height H/diameter D) is characteristically low. In small turbine vanes and blades, however, pin fins may also be located in the middle region of the airfoil. In this case, the aspect ratio can be quite large, usually obtaining values greater than 4. Heat transfer tests, which are conducted under atmospheric conditions for the cooling design of turbine vanes and blades, may overestimate the heat transfer coefficient of the pin-finned flow channel for such long pin fins. The fin efficiency of a long pin fin is almost unity in a low heat transfer situation as it would be encountered under atmospheric conditions, but can be considerably lower under high heat transfer conditions and for pin fins made of low thermal conductivity material. A series of tests with corresponding heat transfer models has been conducted in order to clarify the heat transfer characteristics of the long pin-finned flow channel. It is assumed that heat transfer coefficients can be predicted by the linear combination of two heat transfer equations, which were separately developed for the pin fin surface and for tubes in crossflow. To confirm the suggested combined equations, experiments have been carried out, in which the aspect ratio and the thermal conductivity of the pin were the test parameters. To maintain a high heat transfer coefficient for a long pin fin under high-pressure conditions, the heat transfer was augmented by adding a turbulence promoter on the pin-finned endwall surface. A corresponding equation that describes this situation has been developed. The predicted and measured values showed good agreement. In this paper, a comprehensive study on the heat transfer of a long pin-fin array will be presented.

Heat Transfer Behavior of Silica Nanoparticles in Pool Boiling Experiment

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Denitsa Milanova ◽  
Ranganathan Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Chemical Composition ◽  
Particle Deposition ◽  
Ph Value ◽  
Pool Boiling ◽  
High Heat ◽  
Boiling Regime ◽  
High Heat Transfer ◽  
The Wire

The heat transfer characteristics of silica (SiO2) nanofluids at 0.5vol% concentration and particle sizes of 10nm and 20nm in pool boiling with a suspended heating Nichrome wire have been analyzed. The influence of acidity on heat transfer has been studied. The pH value of the nanosuspensions is important from the point of view that it determines the stability of the particles and their mutual interactions toward the suspended heated wire. When there is no particle deposition on the wire, the nanofluid increases critical heat flux (CHF) by about 50% within the uncertainty limits regardless of pH of the base fluid or particle size. The extent of oxidation on the wire impacts CHF, and is influenced by the chemical composition of nanofluids in buffer solutions. The boiling regime is further extended to higher heat flux when there is agglomeration on the wire. This agglomeration allows high heat transfer through interagglomerate pores, resulting in a nearly threefold increase in burnout heat flux. This deposition occurs for the charged 10nm silica particle. The chemical composition, oxidation, and packing of the particles within the deposition on the wire are shown to be the reasons for the extension of the boiling regime and the net enhancement of the burnout heat flux.

scholarly journals PENGARUH VARIASI FLUIDA PENDINGIN TERHADAP CAPAIAN SUHU OPTIMAL PADA RANCANGAN MESIN PENDINGIN MINI WATER CHILLER

2019 ◽  
Vol 7 (1) ◽  
pp. 36
Author(s):  
Putu Deva Supriana ◽  
Kadek Rihendra Dantes ◽  
I Nyoman Pasek Nugraha
Keyword(s):  
Coolant Fluid ◽  
Water Mixture ◽  
Heat Absorption ◽  
Water Coolant ◽  
Optimal Temperature ◽  
Fluid Mixture ◽  
Independent Variables ◽  
Average Temperature ◽  
Chilled Water ◽  
Modern Era

Di era modern ini perkembangan ilmu pengetahuan dan teknologi sangatlah pesat sehingga mengakibatkan perkembangan dunia industri juga semakin cepat. Mereka berlomba-lomba menemukan alat pendingin untuk memberikan mereka kenyamanan saat melakukan kegiatan-kegiatan didalam ruangan yang panas. Water Chiler adalah proses penanganan udara untuk mengontrol secara serempak terhadap temperatur, kelembaban, kebersihan dan distribusi untuk mencapai kondisi yang diinginkan. Refrigerant yang mengalir dalam siklus sekunder adalah fluida air (water) yang disirkulasikan dengan bantuan pompa. Fluida air pendingin (chilled water) inilah yang nantinya akan mengambil panas ruangan. Dilihat dari beberapa penelitian sebelumnya variasi fluida seperti coolant juga dapat mempengaruhi penyerapan panas dengan baik. Penelitian ini bertujuan untuk mengetahui pengaruh penggunaan variasi fluida air, coolant dan campuran air + coolant terhadap suhu yang dicapai Mini Water Chiler. Metode yang digunakan dalam penelitian ini adalah eksperimen dengan variable bebas yaitu air, coolant dan campuran air + coolant sedangkan variable terikat yaitu suhu. Pengujian dilakukan sebanyak 20 kali dan mencatat hasilnya tiap 20 menit. Dari hasil penelitian fluida campuran air + coolant mendapatkan suhu yang sangat optimal dibandingkan fluida air dan fluida coolant dengan rata-rata suhu di AHU 1 untuk fluida air: 13,430C, coolant: 12,520C dan campuran air + coolant: 11,520C, AHU 2 untuk fluida air: 13,330C, coolant: 12,420C dan campuran air + coolant: 11,420C dan AHU 3 untuk fluida air: 13,230C, coolant: 12,320C dan campuran air + coolant: 11,320C. Berdasarkan hasil penelitian tersebut fluida campuran air + coolant mendapatkan suhu yang sangat optimal dikarenakan karakteristik yang di miliki fluida air dan fluida coolant.Kata Kunci : mini water chiler, variasi fluida, suhu optimal, pendingin In this modern era the development of science and technology is so rapid that the development of the industrial world is also accelerating. They are competing to find refrigerators to provide them comfort while carrying out activities in a hot room. Water Chiler is an air handling process to simultaneously control temperature, humidity, cleanliness and distribution to achieve the desired condition. Refrigerant that flows in the secondary cycle is fluid water (water) which is circulated with the help of a pump. This chilled water will later take the heat of the room. Viewed from several previous studies fluid variations such as coolants can also affect heat absorption well. This study aims to determine the effect of using variations of water fluid, coolant and water + coolant mixture to the temperature achieved by Mini Water Chiler. The method used in this study is an experiment with independent variables namely water, coolant and water + coolant mixture while the dependent variable is temperature. The test is done 20 times and records the results every 20 minutes. From the results of the fluid mixture + coolant research get a very optimal temperature compared to water fluid and coolant fluid with an average temperature in AHU 1 for water fluid: 13.430C, coolant: 12.520C and water mixture + coolant: 11.520C, AHU 2 for water fluid: 13,330C, coolant: 12,420C and mixture of water + coolant: 11,420C and AHU 3 for water fluid: 13,230C, coolant: 12,320C and water mixture + coolant: 11,320C. Based on the results of this study, the mixture of water + coolant fluid gets a very optimal temperature due to the characteristics possessed by water fluid and coolant fluid.keyword : mini water chiller, fluid variations, optimal temperature, coolant

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