scholarly journals KAJIAN TERHADAP KARAKTERISTIK PERPINDAHAN PANAS PADA LOOP THERMOSYPHON SEBAGAI ALAT RECOVERY PANAS TEMPERATUR RENDAH

2020 ◽  
Vol 1 (1) ◽  
pp. 21-42
Author(s):  
Parulian Siagian ◽  
Saloom Hilton Siahaan ◽  
Lestina Siagian
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Fluid Pressure ◽  
Working Fluid ◽  
Airflow Velocity ◽  
Evaporator Temperature ◽  
Copper Pipe ◽  
Work Pressure ◽  
Heated Fluid ◽  
Air Flow Velocity

The purpose of this study was to examine the effectiveness of the Loop Thermosyphon Heat Exchanger (LTHE) fluidized R134a refrigerant at variations in working fluid pressure of 0.8MPa and 1.2MPa. Thermosyphon is made of three parts, namely, evaporator, condenser and adiabatic part. Evaporators are made of 3/4 inch diameter copper pipe with a length of 3.5 cm. The condenser is made of 3/4 inch diameter copper pipe with a length of 15 cm. The adiabatic part of the steam line is made of copper pipes with a diameter of 3/4 inches and a length of 25 cm and a liquid line with a diameter of 3/8 inches with a length of 27 cm. Things that were investigated included the effect of air flow velocity (heated fluid) of 0.8 m/s, 1m/s, and 1.2m/s on the effectiveness of LTHE and the effect of an increase in evaporator temperature by 400C, 500C, and 600C on the effectiveness of LTHE. The study was conducted experimentally where the LTHE evaporator was heated with a heater. The results of this study show that the effectiveness of LTHE heat transfer work pressure of 1.2 MPa pressure is about 30-68% and higher than the effectiveness of LTHE heat transfer work pressure of 0.8 MPa pressure about 22-35%. Effectiveness decreases with increasing airflow velocity. The LTHE thermal resistance of 0.8 MPa pressure is around 0.3-0.450C/ W and is greater than the LTHE thermal resistance of 1.2 MPa pressure around 0.08-0.40C /W.

Thermal Characteristics of a Cylindrical Heat Pipe using Multi-Layer Screen Mesh Wick

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
R. Sankar Rao ◽  
S. Bhanu Prakash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Thermal Characteristics ◽  
Wire Mesh ◽  
Working Fluid ◽  
Wick Structure ◽  
Screen Mesh

Heat pipe is the most widely used heat exchanging device in removal of heat from any given system at a faster rate. The thermal characteristics of heat pipe with single and multi-layered screen mesh wicks have been observed with two working fluids water and acetone. Heat pipe of length 250 mm and 12.7 mm outer diameter, made of copper material is used in all the trials of with and without wick structure. A 100 mesh stainless steel screen wire mesh is chosen as wick structure. Experiments were conducted at different heat loads and various inclinations with 100% fill ratio in evaporator. The performance is measured based on total thermal resistance and overall heat transfer coefficient. The heat pipe is found effective at 60o inclination with acetone as a working fluid and with four layered screen mesh wick. Uncertainty in thermal resistance and heat transfer coefficient is calculated for a heat input of 10W at 0 and 60 inclinations.

Experimental Investigation of Heat Transfer of Refrigerant Fluid Pulsating Heat Pipe

2017 ◽  
Vol 865 ◽  
pp. 137-142
Author(s):  
Somchai Maneewan ◽  
Chantana Punlek ◽  
Hoy Yen Chan ◽  
Atthakorn Thongtha
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Heat Input ◽  
Filling Ratio ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Filling Volume ◽  
Volume Filling

Heat transfer performances of a pulsating heat pipe (PHP) having internal and external diameter with 4.5 mm and 6 mm with various contents of refrigerant are experimentally investigated. The working fluid as R404A refrigerant was filled in the volume ratios from 0% to 80% and the heat input was controlled in the range from 10 W to 80 W. Obtained results exhibited the ability of R404A refrigerant can enhance the thermal performance in steady state condition. The average temperature difference of the evaporating section and condensing section in the 80% filling volume ratio decreased from 9.5 °C to 2.5 °C when the heating power increase from 10 W to 80 W. The thermal resistance of evaporator and condenser decreased with an increase of the heat input as well. For other filling volume ratios, the trend of temperature difference and thermal resistance was similar to that of the 80% volume filling ratio. Considering the same heat input, the highest heat transfer performance was found at the 80% volume filling ratio. Refrigerant with a relatively low dynamic consistency can lead to relatively high velocity in the PHP that can reduce the temperature difference between the evaporating section and condensing section.

Enhanced Miniature Loop Heat Pipe Cooling System for High Power Density Electronics

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
J. H. Choi ◽  
B. H. Sung ◽  
J. H. Yoo ◽  
C. J. Kim ◽  
D.-A. Borca-Tasciuc
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Power Density ◽  
Thermal Performance ◽  
High Power ◽  
Design Stage ◽  
Working Fluid ◽  
High Power Density ◽  
Graphic Processing Units ◽  
Maximum Heat

The implementation of high power density, multicore central and graphic processing units (CPUs and GPUs) coupled with higher clock rates of the high-end computing hardware requires enhanced cooling technologies able to attend high heat fluxes while meeting strict design constrains associated with system volume and weight. Miniature loop heat pipes (mLHP) emerge as one of the technologies best suited to meet all these demands. Nonetheless, operational problems, such as instable behavior during startup on evaporator side, have stunted the advent of commercialization. This paper investigates experimentally two types of mLHP systems designed for workstation CPUs employing disk shaped and rectangular evaporators, respectively. Since there is a strong demand for miniaturization in commercial applications, emphasis was also placed on physical size during the design stage of the new systems. One of the mLHP system investigated here is demonstrated to have an increased thermal performance at a reduced system weight. Specifically, it is shown that the system can reach a maximum heat transfer rate of 170 W with an overall thermal resistance of 0.12 K/W. The corresponding heat flux is 18.9 W/cm2, approximately 30% higher than that of larger size commercial systems. The studies carried out here also suggest that decreasing the thermal resistance between the heat source and the working fluid and maximizing the area for heat transfer are keys for obtaining an enhanced thermal performance.

Effect of Wavy Wall and Plate Bifurcations On Heat Transfer Enhancement in Microchannel

2021 ◽  
Author(s):  
Sathish Kumar D ◽  
Jayavel S
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Working Fluid ◽  
Thin Wall ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Entropy Generation Number ◽  
Transfer Characteristics ◽  
Overall Performance ◽  
Study Heat Transfer

Abstract Miniaturization of electronic components requires compact and effective cooling techniques to dissipate large heat flux without significant increase in pumping power. Microchannel heat sink with liquid as working fluid is a suitable technique for the purpose. In the present study, heat transfer characteristics in presence of vertical bifurcation placed in the downstream of the microchannel passage is studied numerically. Six types of bifurcating plates are considered under two categories: (i) thick-plate and (ii) wavy thin-wall. Water is taken as the working fluid and the flow rate has been varied in the Reynolds number range, 100 = Re = 1000.The effect of bifurcations on pressure drop, heat transfer and the overall thermal resistance are analyzed and compared with those of plane microchannel without bifurcation. The numerical results show that the usage of bifurcation in the microchannel reduces the overall thermal resistance. Field synergy number, entropy generation number and hydro-thermal performance index are calculated to quantify the overall performance improvement in the microchannel with bifurcations. Constant wavy thin-wall bifurcation has been found to improve the overall performance of the microchannel. The detailed geometry of the bifurcation, the resulting convective heat transfer characteristics and percentage improvement in the performance are reported.

Water-Ammonia Cycles for the Utilization of Low Temperature Geothermal Resources

2015 ◽  
Author(s):  
Daniele Fiaschi ◽  
Giampaolo Manfrida ◽  
Lorenzo Talluri
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Unit Cost ◽  
Heat Capacities ◽  
Hot Water ◽  
Saturated Steam ◽  
Working Fluid ◽  
Evaporator Temperature ◽  
Power Cycle

The research deals with the possibility of effective exploitation of low temperature geothermal energy resources, which are generally much more widespread worldwide compared to conventional high temperature ones, typically available only in limited areas of the Earth. The basic idea is the application of an advanced binary cycle, only thermally coupled to the primary endogen heat source. The selected reference-power cycle is the well-known Kalina, which gives the possibility of optimizing the matching between heat capacities of the geothermal fluid (i.e. typically hot water or saturated steam) and the cycle working fluid, which is a non azeotropic NH3-H2O mixture with variable vaporization temperature at a fixed pressure. The heat transfer diagrams of the main Kalina heat exchangers, namely the condenser and the evaporator, are analysed with the aim of minimizing the irreversibilities related to the heat transfer. At different fixed NH3-H2O composition and condenser pressures, the evaporator pressure shows an efficiency optimizing value between 40 and 55 bar, generally increasing at higher condenser pressure. At fixed geothermal heat source temperature, condenser/evaporator pressures and working mixture composition, the cycle efficiency increases with increasing evaporator temperature, because of the reduction in the approach temperature difference between the geothermal and the working fluid. Higher efficiencies are found at higher NH3 concentrations. The proposed Water-Ammonia power cycle is further enhanced introducing a chiller (thus making the power cycle a CCP unit), thanks to the properties of the fluid mixture downstream the absorber, through an intermediate heat exchanger between the condenser and the evaporator. Mainly due to the better matching of heat capacities between the geothermal and the working fluid, the proposed power cycle offers the possibility of interesting improvements in electrical efficiency compared to traditionally proposed binary cycles using ORCs, at fixed temperature level of the heat source. In the investigated proposal, values of electric efficiency between 15 and 20% are found. An economic analysis is presented, demonstrating that the CCP system is able to produce electricity at decreased unit cost with respect to the power-only unit.

An Investigation of Flat-Plate Oscillating Heat Pipes

2010 ◽  
Author(s):  
Peng Cheng ◽  
Scott Thompson ◽  
Joe Boswell ◽  
Hongbin Ma
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flat Plate ◽  
Heat Transfer Performance ◽  
Operating Temperature ◽  
Pure Water ◽  
Heat Pipes ◽  
Copper Plate ◽  
Working Fluid ◽  
Transfer Performance

The heat transfer performance of flat-plate oscillating heat pipes (FP-OHPs) was investigated experimentally and theoretically. Two layers of channels were created by machining grooves on both sides of copper plate, in order to increase the channel number per unit volume. The channels had rectangular cross-sections with hydraulic diameters ranging from 0.762 mm to 1.389 mm. Acetone, water and diamond/acetone, gold/water and diamond/water nanofluids were tested as working fluids. It was found that the FP-OHP’s thermal resistance depended on the power input and operating temperature. The FP-OHP charged with pure water achieved a thermal resistance of 0.078°C/W while removing 560 W with a heat flux of 86.8 W/cm2. The thermal resistance was further decreased when nanofluid was used as the working fluid. A mathematical model predicting the heat transfer performance was developed to predict the effects of channel dimension, heating mode, working fluid and operating temperature on the thermal performance of the FP-OHP. Results presented here will assist in optimization of the FP-OHP and provide a better understanding of heat transfer mechanisms occurring in an OHPs.

Effect of Operational Parameters on the Thermal Performance of Flat Plate Oscillating Heat Pipe

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Kamlesh K. Mehta ◽  
Nirvesh Mehta ◽  
Vivek Patel
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flat Plate ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Charge Ratio ◽  
Working Fluid ◽  
Operational Parameters ◽  
Oscillating Heat Pipe ◽  
Transfer Device

Abstract Flat plate oscillating heat pipe (FP-OHP) is a unique heat transfer device and considered as a promising candidate for effective heat transfer device in electronics industries. A number of theoretical studies and experimental investigations have been carried out on FP-OHP in the past decades after its invention. However, due to the operational characteristics of FP-OHP, the effect of various parameters on the thermal performance of FP-OHP has not been completely revealed so far. This paper attempts to discuss the effect of operational parameters on the thermal performance of FP-OHP. In this study, the FP-OHP was investigated with different charge ratios, orientations, working fluids, and heat loads from 10 W to 150 W. In order to investigate the effect, 18 parallel square channels of 2 × 2 mm2 are machined onto pure copper plate (93 × 70 × 8 mm3) to form FP-OHP. DI water, ethanol, methanol, acetone, and FC-72 are investigated. The measured thermal resistance was strongly dependent on operational parameters. The optimum performance was observed with acetone with a charge ratio of 70% in the vertical orientation. The lowest thermal resistance of 0.39 °C/W is achieved using acetone as a working fluid at 100 W. A Kutateladze number (Ku) was used to compare the experimental data and found to be suitable for prediction of the thermal performance of FP-OHP with standard deviation of 15%.

Experimental Investigation and Performance Evaluation of a Multi Turn Closed Loop Pulsating Heat Pipe

2014 ◽  
Vol 592-594 ◽  
pp. 1554-1558 ◽  
Author(s):  
N. Narendra Babu ◽  
Rudra Naik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Resistance ◽  
Transfer Coefficient ◽  
Heat Pipe ◽  
Closed Loop ◽  
Experimental Result ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Working Fluids

Pulsating heat pipe (PHP) is a passive heat transfer device, which transfers heat from one region to another with exceptional heat transfer capacity. It utilizes the latent heat of vaporization of the working fluid as well as the sensible heat. As a result, the effective thermal conductivity is higher than that of the conductors. An experimental study on three turn closed loop pulsating heat pipe with three different working fluids viz., Acetone, Methanol, Heptane and distilled water were employed. The PHP is made up of brass material with an inner diameter of 1.95mm, with a total length of 1150 mm for different fill ratios (FR) was employed .The PHP is tested for the thermal resistance and the heat transfer coefficient. The experimental result strongly demonstrates that acetone is a better working fluid among the working fluids considered in terms of higher heat transfer coefficient and lower thermal resistance.

scholarly journals IMPROVING FUEL EFFICIENCY OF MARINE SWIRL-CHAMBER DIESEL ENGINE BY INCREASED THERMAL RESISTANCE OF HEAT TRANSFER

2019 ◽  
pp. 80-87
Author(s):  
Alexander Fedorovich Dorokhov ◽  
Pavel Aleksandrovitch Dorokhov
Keyword(s):  
Heat Transfer ◽  
Diesel Engine ◽  
Thermal Resistance ◽  
Combustion Chamber ◽  
Fuel Consumption ◽  
Diesel Engines ◽  
Fuel Efficiency ◽  
Working Fluid ◽  
Gas Temperature ◽  
Swirl Chamber

The article considers ship swirl-chamber diesel engines used in shipbuilding as the main and auxiliary engines. Two reasons for low profitability of the swirl chamber diesel engines are highlighted: large heat losses of the cooling working fluid due to the extended heat transfer surface of the chamber, and significant aerodynamic energy losses of compressed air during its passage through a relatively narrow channel connecting the piston chamber with the combustion chamber and the flow of gases from the swirl chamber on top the piston space. There have been proposed the methods for improving the operational performance of swirl-chamber diesels in production, in particular, their fuel efficiency. The scheme of the swirl-chamber and a section of the swirl-chamber cylinder head are presented. It has been stated that the total coefficient of thermal conductivity can be reduced if the wall of the swirl- chamber is made multi-layer. The layouts of a multi-layer cylinder-spherical wall of a swirl combustion chamber with a titanium cylinder-spherical insertion and thermal insulation of a vortex combustion chamber are given. The total thermal resistance of the spherical wall was calculated, heat loss through the multilayer spherical wall was determined, gas temperature in the vortex chamber was calculated, according to the average cycle temperature diagram. It was inferred that the amount of heat removed from the working fluid to cooling through the thermally insulated wall of the swirl-chamber will be 40% less than the amount of heat released to the cooling through the wall of the swirl-chamber of a commercial diesel engine. The difference in heat will be used to increase the indicator gas operation, which, with the same cyclic fuel supply, will lead to a decrease in the specific indicator fuel consumption, and at a constant level of internal engine losses - to a decrease in the specific effective fuel consumption.

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