Experimental Investigations on Thermal Performance of a Closed Loop Pulsating Heat Pipe

2009 ◽  
Author(s):  
Yu Wang ◽  
Weiyi Li ◽  
Lianyou Wei ◽  
Binbin Cao
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Thermal Performance ◽  
Closed Loop ◽  
Effective Conductivity ◽  
Experimental Studies ◽  
Filling Ratio ◽  
Experimental Investigations ◽  
Stable Operation ◽  
Pulsating Heat Pipe

Closed loop pulsating heat pipes (CLPHPs) are complex heat transfer devices having a strong thermohydrodynamic coupling governing the thermal performance. Experimental studies on a CLPHP have focused on visualizing the start-up and operation mode of CLPHP or characterizing the heat transfer capability of CLPHP. In this paper, a visualization setup was established and a series of experimental observations based on the visualization setup were conducted to study the fundamental phenomena and thermal performance in CLPHPs within water. The influence characterization has been studied for the variation of thermal condition in the evaporator section of CLPHPs (large flow rate, little flow rate), inclination angel (30 °, 45 °, 60 °), filling ratio (approximately at 30%, 50%, 70%)of the CLPHP. The thermal performance of CLPHPs was mainly evaluated by calculating the effective conductivity which related to temperature distribution of both evaporator and condenser sections of the CLPHPs, also to the heat transfer between these two sections. The results indicate a strong influence of the filling ratio and the gravity on the CLPHP thermal performance. The filling ratio also affects normal startup and stable operation of the CLPHP.

Experimental Investigations on the Thermal Performance of a Single Closed Loop Pulsating Heat Pipe Using TiO2 Nanofluid

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
G. V. Pradeep ◽  
K. Rama Narasimha
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Closed Loop ◽  
Experimental Investigations ◽  
Pulsating Heat Pipe ◽  
Vertical Orientation ◽  
Stable Suspension ◽  
Bottom Heating ◽  
Heating Mode

This paper describes the experimental investigations conducted on a closed loop pulsating heat pipe (CLPHP) for assessing the thermal performance. The pulsating heat pipe has a single closed loop made of copper. The working fluids used are water and titanium dioxide nanofluids with varying concentrations of TiO2 nanoparticles (1.5% and 1%) on weight basis. The TiO2 particles are mixed in water to form a stable suspension using a sonicator. The heat input is varied between 40 W and 100 W in steps of 20 W. All experiments are conducted in the bottom heating mode (evaporator at the top) in the vertical and horizontal orientations. The parameters considered for evaluating the thermal performance are the temperature difference between evaporator and condenser, thermal resistance, heat transfer coefficient, and thermal conductivity. The results of the investigation reveal that the vertical orientation and increase in nanoparticle concentration favors better heat transfer performance of the single closed loop pulsating heat pipe.

scholarly journals Experiment Study on Improved Closed Loop Pulsating Heat Pipe with Silver/Water Nanofluid

2013 ◽  
Vol 732-733 ◽  
pp. 462-466
Author(s):  
Wei Xiu Shi ◽  
Wei Yi Li ◽  
Li Sheng Pan
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Pulsating Heat Pipe ◽  
Start Up ◽  
High Heating ◽  
Operation Stability ◽  
Heat Transfer Limit

Start up and heat transfer performances of improved closed loop pulsating heat pipe (ICLPHP) charged with water and silver/water nanofluid, respectively, were investigated experimentally with angles of 90° and 60°. Both the average evaporator wall temperature and the overall thermal resistance of the ICLPHP with different working fluids and at the volume filling ratio of 35% were tested and compared. Experimental results showed that nanofluid caused different thermal performances of ICLPHP. Within the experiment range, silver/water nanofluid can improve operation stability and heat transfer limit and reduce starting power compared with water. With high heating power, thermal resistance of nanofluid was lower than that of water. With inclination of 60°, ICLPHP with nanofluid operated better and reduced sensitivity of inclination.

scholarly journals Study of Thermal Performance of Closed Loop Pulsating Heat Pipe using Computational Fluid Dynamics

2021 ◽  
Vol 9 (9) ◽  
pp. 1384-1388
Author(s):  
K. C. Giri
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Pulsating Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Different Temperatures

Abstract: Pulsating heat pipe is a heat transfer device which works on two principles that is phase transition and thermal conductivity which transfer heat effectively at different temperatures. Different factors affect the thermal performance of pulsating heat pipe. So, various researchers tried to enhance thermal conductivity by changing parameters such as working fluids, filling ratio, etc. Analysis of heat transfer characteristics of closed loop pulsating heat pipe (CLPHP) is to be carried out by using Computational Fluid Dynamics. The CLPHP is to be modelled on ANSYS Workbench, the flow of CLPHP is to be observed under specific boundary conditions by using ANSYS Fluent software. Acetone and Water are taken as the working fluid with 70% filling ratio at ambient temperature 30° C and the heat flux of 200 W is supplied at evaporator. Also, the analysis has been done to know the behaviour of PHPs under varying supply of heat flux at evaporator (inlet), the output heat flux is obtained at condenser (outlet) and find out how the heat flux is varying at different temperatures. CFD results shows the heat transfer characteristics observing the performance of CLPHP is a numerical manner. The obtained CFD results are compared with the experimental. The outputs of the simulations are plotted in graphs and outlines. Keywords: Closed Loop Pulsating Heat Pipe, CFD, Heat Transfer, ANSYS.

Effect of Filling Ratio on Thermal Performance of Closed Loop Pulsating Heat Pipe

2018 ◽  
Vol 5 (10) ◽  
pp. 22229-22236
Author(s):  
E.R. Babu ◽  
H.N. Reddappa ◽  
G.V. Gnanendra Reddy
Keyword(s):  
Heat Pipe ◽  
Thermal Performance ◽  
Closed Loop ◽  
Filling Ratio ◽  
Pulsating Heat Pipe

scholarly journals Effect of Filling Ratio on Heat Transfer Characteristics and Performance of a Closed Loop Pulsating Heat Pipe

2013 ◽  
Vol 56 ◽  
pp. 88-95 ◽  
Author(s):  
Himel Barua ◽  
Mohammad Ali ◽  
Md. Nuruzzaman ◽  
M. Quamrul Islam ◽  
Chowdhury M. Feroz
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Closed Loop ◽  
Filling Ratio ◽  
Pulsating Heat Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
And Performance

Thermal performance of a double-pass solar air heater (SAH) with ribbed absorber surface – an experimental study

2020 ◽  
Vol 17 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Nandkishor Sah ◽  
Mohan Jagadeesh Kumar Mandapati
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Flow Rate ◽  
Thermal Performance ◽  
Agricultural Products ◽  
Experimental Investigations ◽  
Absorber Plate ◽  
Content Type ◽  
Solar Intensity ◽  
Passive Techniques

Purpose Use of packed beds, enhanced tubes, nano-fluids and artificial ribs are few passive techniques to increase heat transfer in solar air heaters (SAHs). Artificial ribs attached to the absorber plate of the SAH will enhance the turbulence near the plate. Experimental analyses are conducted to find the thermal performance of SAH with ribs of regular geometries including rectangular, semi-circular and triangular in cross section. This paper aims to present the improvement in thermal performance of SAH with modified-arc. Design/methodology/approach Absorber plates are designed with ribs of rectangular, triangular, semi-circular and modified-arc in cross-section using existing data in literature. Physical dimensions of the ribs are designed by adapting procedure from literature. Absorber plates are manufactured with ribs and coated with blackboard paint and fixed to the existing SAH. Experiments are conducted with a variable-speed blower fixed to the inlet section of the SAH, which is used to supply air at different mass flow rates in a range between 0.495 and 0.557 kg/min. Findings Efficiency is found to be a strong function of mass flow rate of air through the SAH from the present experimental investigations. It was found that use of modified-arc ribs enhanced the efficiency of SAH by 105.35 per cent compared to SAH with plane absorber plate. Efficiency of SAH with modified-arc ribs is found to be higher by 24.43, 45.61 and 63.21 per cent, respectively, for SAH with semi-circular, rectangular and triangular arc ribs on its absorber plate. Research limitations/implications Experiments on SAH are conducted during daytime from 9:00 am to 5:00 pm in open atmospheric conditions. Solar intensity is continuously changing during the experimentation from morning to evening. Calculations are made based on the observations with average values of solar intensity and temperature readings. More accurate values of SAH efficiency can be obtained with constant heat supply to the absorber plate by simulating the experimental setup in indoor conditions. Temperature and flow rate observations could be more accurate with sophisticated instrumentation rather than using simple thermocouples and orifice meters. Social implications SAHs are basically used to supply hot air for both rural and industrial applications. These are used for crop drying, preheating of air, removal of moisture from leather, chemicals, etc. Conventionally, formers in India are using open sun drying to remove moisture from agricultural products. In this method, the moisture can be removed up to a level of 20 to 25 per cent. Use of SAH can remove moisture up to below 5 per cent and process is clean without reducing the quality of agricultural products. Enhancing the efficiency of SAHs will surely increase its usage by formers for crop drying. Originality/value Use of artificial ribs on absorber plate of SAH is most economical among many of the active and passive techniques. Numerical and experimental investigations are found in literature with regular cross-sectional ribs, including rectangular, triangular and semi-circular. The present work proposed new shape of the ribs named as modified-arc, which was not presented in the literature. Experimental analysis proved that the use of modified-arc makes the SAH more efficient in heat transfer.

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