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Sauro Filippeschi - One of the best experts on this subject based on the ideXlab platform.
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an experimental investigation on the evaporation and condensation heat transfer of two phase closed thermosyphons
Experimental Thermal and Fluid Science, 2017Co-Authors: Davoud Jafari, Paolo De Marco, Sauro Filippeschi, Alessandro FrancoAbstract:Abstract Two-phase closed thermosyphons (TPCTs) are excellent thermal transfer devices that their integration into heat exchangers has been shown a strong potential for energy savings. The scope of this study is an experimental evaluation of the evaporation and condensation heat transfer of a TPCT for uniformly heated Evaporator surface. Water as the working fluid is charged in a TPCT with a length of 500 mm and an inner diameter of 33 mm at different filling ratios (8–100%). The Thermosyphon heat transfer performances are compared with some predictive correlations of suppress the pool boiling insert uniquely and suppress the pool boiling combined with film evaporation for the Evaporator Section at different filling ratios. The experimentally obtained condensation heat transfer is also evaluated by available filmwise condensation model. Results show an agreement with the most of the selected correlations with tolerance ±30% and the appropriate set of correlations are introduced giving an accuracy within ±10%.
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an experimental investigation and optimization of screen mesh heat pipes for low mid temperature applications
Experimental Thermal and Fluid Science, 2017Co-Authors: Davoud Jafari, Paolo De Marco, Sauro Filippeschi, Hamidereza Shamsi, Alessandro FrancoAbstract:The perspectives of utilization of a screen mesh heat pipe (HP) for low to medium operating temperature applications are studied in this study. A two-dimensional mathematical model for heat and mass transfer of HPs is presented to define its performances under steady state operations. The model couples heat conduction in the wall with both liquid flow in the wick and vapor flow in the core. Experimental analysis is developed to evaluate the influence of operating parameters (the orientation and the cooling temperature) as well as the Evaporator Section length on the performance of the HP. Furthermore, a modeling approach to optimize the HP performance from a thermal point of view is presented. Using the heat transfer capability and total thermal resistance as the objective function and the structure parameters as the decision variable, the optimization design for the HP is performed using the Non-Dominated Sorting in Genetic Algorithms-II (NSGA-II). The results show that the optimal wick thickness and wick permeability to be a strong function of the heat flux. It is concluded that to have lower thermal resistance at lower heat fluxes for a screen mesh wick HP may have a large effective thermal conductivity, but have a small permeability. While at high heat transfer rate a small effective thermal conductivity, but a large permeability is recommended. The designer must always make trade-offs between these competing factors to obtain an optimal wick design. The investigations are aimed to determine working limits and thermal performance of HPs for low to medium operating temperature applications.
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experimental study of a closed loop flat plate pulsating heat pipe under a varying gravity force
International Journal of Thermal Sciences, 2015Co-Authors: Vincent Ayel, Lucio Araneo, Alessandro Scalambra, Mauro Mameli, Cyril Romestant, Andre Piteau, Marco Marengo, Sauro FilippeschiAbstract:This paper reports on an experimental study of a closed loop Flat Plate Pulsating Heat Pipe (FPPHP) tested on ground and on board of an aircraft during the 60th ESA parabolic flight campaign, during which hyper- and microgravity conditions were reproduced. The tested FPPHP consists of two brazed copper plates, into one of which a continuous rectangular channel (1.6 × 1.7 mm2) with 12 bends in the Evaporator is machined. The channel is filled with FC-72 as working fluid with a volumetric filling ratio of 50%. Tests have been conducted with the FPPHP positioned both horizontally and vertically (bottom-heated). The FPPHP presents an innovative design, involving the milling of grooves between the channels. Experimental results on the ground show that the thermal device can transfer more than 180 W in both inclinations, and that the horizontal operation is characterized by repeated stop-and-start phases and lower thermal performance. The FPPHP can operate under microgravity conditions and with a transient gravity force, with global thermal resistance reaching 50% and 25% of that of the empty plate (or around 66% and 35% of a full copper spreader of same overall dimensions), in horizontal and vertical orientation respectively. The temperature homogeneity remains within 10 K in the Evaporator Section and 3 K in the condenser Section with thermal power transfer up to 180 W. Minimum thermal resistance of 0.12 K W−1 was recorded, with its value rising as heating grew more powerful. A parabolic flight test demonstrated that the FPPHP in vertical inclination is rapidly influenced by variation of gravity field, even if, due to the novel geometry, it continues to operate under microgravity. In horizontal inclination, on the other hand, there was no observable parameter change during gravity field variations.
Mauro Mameli - One of the best experts on this subject based on the ideXlab platform.
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experimental study of a closed loop flat plate pulsating heat pipe under a varying gravity force
International Journal of Thermal Sciences, 2015Co-Authors: Vincent Ayel, Lucio Araneo, Alessandro Scalambra, Mauro Mameli, Cyril Romestant, Andre Piteau, Marco Marengo, Sauro FilippeschiAbstract:This paper reports on an experimental study of a closed loop Flat Plate Pulsating Heat Pipe (FPPHP) tested on ground and on board of an aircraft during the 60th ESA parabolic flight campaign, during which hyper- and microgravity conditions were reproduced. The tested FPPHP consists of two brazed copper plates, into one of which a continuous rectangular channel (1.6 × 1.7 mm2) with 12 bends in the Evaporator is machined. The channel is filled with FC-72 as working fluid with a volumetric filling ratio of 50%. Tests have been conducted with the FPPHP positioned both horizontally and vertically (bottom-heated). The FPPHP presents an innovative design, involving the milling of grooves between the channels. Experimental results on the ground show that the thermal device can transfer more than 180 W in both inclinations, and that the horizontal operation is characterized by repeated stop-and-start phases and lower thermal performance. The FPPHP can operate under microgravity conditions and with a transient gravity force, with global thermal resistance reaching 50% and 25% of that of the empty plate (or around 66% and 35% of a full copper spreader of same overall dimensions), in horizontal and vertical orientation respectively. The temperature homogeneity remains within 10 K in the Evaporator Section and 3 K in the condenser Section with thermal power transfer up to 180 W. Minimum thermal resistance of 0.12 K W−1 was recorded, with its value rising as heating grew more powerful. A parabolic flight test demonstrated that the FPPHP in vertical inclination is rapidly influenced by variation of gravity field, even if, due to the novel geometry, it continues to operate under microgravity. In horizontal inclination, on the other hand, there was no observable parameter change during gravity field variations.
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local heat transfer measurement and thermo fluid characterization of a pulsating heat pipe
International Journal of Thermal Sciences, 2014Co-Authors: Mauro Mameli, Marco Marengo, Sameer KhandekarAbstract:Abstract A compact Closed Loop Pulsating Heat Pipe (CLPHP), filled with ethanol (65% v/v), made of four transparent glass tubes forming the adiabatic Section and connected with copper U-turns in the Evaporator and condenser Sections respectively, is designed in order to perform comprehensive thermal-hydraulic performance investigation. Local heat transfer coefficient is estimated by measurement of tube wall and internal fluid temperatures in the Evaporator Section. Simultaneously, fluid pressure oscillations are recorded together with the corresponding flow patterns. The thermal performances are measured for different heat input levels and global orientation of the device with respect to gravity. One exploratory test is also done with azeotropic mixture of ethanol and water. Results show that a stable device operation is achieved (i.e. Evaporator wall temperatures can reach a pseudo-steady-state) only when a circulating flow mode is established superimposed on local pulsating flow. The heat transfer performance strongly depends on the heat input level and the inclination angle, which, in turn, also affect the ensuing flow pattern. The spectral analysis of the pressure signal reveals that even during the stable performance regimes, characteristic fluid oscillation frequencies are not uniquely recognizable. Equivalent thermal conductivities of the order of 10–15 times that of pure copper are achieved. Due to small number of turns horizontal mode operation is not feasible. Preliminary results indicate that filling azeotropic mixture of ethanol and water as working fluid does not alter the thermal performance as compared to pure ethanol case.
Marco Marengo - One of the best experts on this subject based on the ideXlab platform.
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experimental study of a closed loop flat plate pulsating heat pipe under a varying gravity force
International Journal of Thermal Sciences, 2015Co-Authors: Vincent Ayel, Lucio Araneo, Alessandro Scalambra, Mauro Mameli, Cyril Romestant, Andre Piteau, Marco Marengo, Sauro FilippeschiAbstract:This paper reports on an experimental study of a closed loop Flat Plate Pulsating Heat Pipe (FPPHP) tested on ground and on board of an aircraft during the 60th ESA parabolic flight campaign, during which hyper- and microgravity conditions were reproduced. The tested FPPHP consists of two brazed copper plates, into one of which a continuous rectangular channel (1.6 × 1.7 mm2) with 12 bends in the Evaporator is machined. The channel is filled with FC-72 as working fluid with a volumetric filling ratio of 50%. Tests have been conducted with the FPPHP positioned both horizontally and vertically (bottom-heated). The FPPHP presents an innovative design, involving the milling of grooves between the channels. Experimental results on the ground show that the thermal device can transfer more than 180 W in both inclinations, and that the horizontal operation is characterized by repeated stop-and-start phases and lower thermal performance. The FPPHP can operate under microgravity conditions and with a transient gravity force, with global thermal resistance reaching 50% and 25% of that of the empty plate (or around 66% and 35% of a full copper spreader of same overall dimensions), in horizontal and vertical orientation respectively. The temperature homogeneity remains within 10 K in the Evaporator Section and 3 K in the condenser Section with thermal power transfer up to 180 W. Minimum thermal resistance of 0.12 K W−1 was recorded, with its value rising as heating grew more powerful. A parabolic flight test demonstrated that the FPPHP in vertical inclination is rapidly influenced by variation of gravity field, even if, due to the novel geometry, it continues to operate under microgravity. In horizontal inclination, on the other hand, there was no observable parameter change during gravity field variations.
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local heat transfer measurement and thermo fluid characterization of a pulsating heat pipe
International Journal of Thermal Sciences, 2014Co-Authors: Mauro Mameli, Marco Marengo, Sameer KhandekarAbstract:Abstract A compact Closed Loop Pulsating Heat Pipe (CLPHP), filled with ethanol (65% v/v), made of four transparent glass tubes forming the adiabatic Section and connected with copper U-turns in the Evaporator and condenser Sections respectively, is designed in order to perform comprehensive thermal-hydraulic performance investigation. Local heat transfer coefficient is estimated by measurement of tube wall and internal fluid temperatures in the Evaporator Section. Simultaneously, fluid pressure oscillations are recorded together with the corresponding flow patterns. The thermal performances are measured for different heat input levels and global orientation of the device with respect to gravity. One exploratory test is also done with azeotropic mixture of ethanol and water. Results show that a stable device operation is achieved (i.e. Evaporator wall temperatures can reach a pseudo-steady-state) only when a circulating flow mode is established superimposed on local pulsating flow. The heat transfer performance strongly depends on the heat input level and the inclination angle, which, in turn, also affect the ensuing flow pattern. The spectral analysis of the pressure signal reveals that even during the stable performance regimes, characteristic fluid oscillation frequencies are not uniquely recognizable. Equivalent thermal conductivities of the order of 10–15 times that of pure copper are achieved. Due to small number of turns horizontal mode operation is not feasible. Preliminary results indicate that filling azeotropic mixture of ethanol and water as working fluid does not alter the thermal performance as compared to pure ethanol case.
S Rittidech - One of the best experts on this subject based on the ideXlab platform.
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Application of flat thermosyphon in a solar collector for increasing the temperature in a reboiler
2012Co-Authors: T. Premprayoon, S Rittidech, B. BubphachotAbstract:This research aims to study the application of a solar collector with flat themosyphons to increase the temperature in a reboiler of ethanol distillation. The solar collector was divided into three Sections, 1) solar collecting plate Evaporator, 2) adiabatic Section, and 3) heat exchange tank or condenser Section. The inside flat thermosyphons tube had cross-Section in x-axis of 0.628 cm and y-axis of 0.46 cm, and 185 cm length. There were 10 tubes using in the solar collector. The length of each tube consisted of Evaporator Section 150 cm long, adiabatic Section 5 cm long and condenser Section 30 cm long. The R123 was used as working fluid with filling ratio of 50% of the Evaporator volume. The 10 flat thermosyphons tubes filled with the R123 were parallel placed in the solar collecting plate with a 10 cm gap of each tube. The tubes arrangement was aligned at an inclination angle of 18 degrees from the horizontal plate and the solar collecting plate was turned to the south. Efficiency evaluations were conducted during daylight hours over a month period. The experimental results showed that an average of the solar collector efficiency in daily was 70%. When applying the flat thermosyphons solar collector to a reboiler with a set of closed-loop oscillating heat pipe with check valves, it was found that the temperature in the reboiler increased 22.9C. In addition, the ethanol distillation time decreased 52 min. However, the economics analysis is used to accept an investment. It was found that internal rate of return (IRR) and the payback period (PP) were 14% and 1.3 years, respectively.
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internal flow patterns on heat transfer characteristics of a closed loop oscillating heat pipe with check valves using ethanol and a silver nano ethanol mixture
Experimental Thermal and Fluid Science, 2010Co-Authors: N Bhuwakietkumjohn, S RittidechAbstract:Abstract The aim of this research was to investigate the internal flow patterns and heat transfer characteristics of a closed-loop oscillating heat-pipe with check valves (CLOHP/CV). The ratio of number of check valves to meandering turns was 0.2. Ethanol and a silver nano-ethanol mixture were used as working fluids with a filling ratio of 50% by total volume of tube. The CLOHP/CV was made of a glass tube with an inside diameter of 2.4 mm. The Evaporator Section was 50 mm and 100 mm in length and there were 10 meandering turns. An inclination angle of 90° from horizontal axis was established. The Evaporator Section was heated by an electric heater and the condenser Section was cooled by distilled water. Temperature at the Evaporator Section was controlled at 85 °C, 105 °C and 125 °C. The inlet and outlet temperatures were measured. A digital camera and video camera were used to observe the flow patterns at the Evaporator. The silver nano-ethanol mixture gave higher heat flux than ethanol. When the temperature at the Evaporator Section was increased from 85 °C to 105 °C and 125 °C. It was found that, the flow patterns occurred as annular flow + slug flow, slug flow + bubble flow and dispersed bubble flow + bubble flow respectively. The main regime of each flow pattern can be determined from the flow pattern map ethanol and a silver nano-ethanol mixture. Each of the two working fluids gave corresponding flow patterns.
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thermosyphon installation for energy thrift in a smoked fish sausage oven tiso
Energy, 2010Co-Authors: T Parametthanuwat, S Rittidech, K BooddachanAbstract:Abstract This research presents a case study of applying a thermosyphon for energy conservation in a smoked fish sausage oven. An oven with the size of 1.5 m × 1.5 m × 1.7 m (width × length × height) was installed with a thermosyphon made up of 304 stainless steel (AISI 304) tubes with 25.4 mm ID to improve temperature distribution, decrease processing time and reduce LPG consumption. The lengths of the Evaporator and condenser Sections were 30 cm and 120 cm, respectively. Deionized water, deionized water mixed with silver nano particles and deionized water mixed with gold nano particles at the concentration of 0.5% (w/v) were used as working fluids at a filling ratio of 80% by Evaporator Section volume. The oven using deionized water mixed with silver nano particles as working fluid appeared to have uniform temperature distribution. Consequently, processing time and LPG consumption could be reduced by 10 min/unit and 1.8 kg/unit, respectively. The quality of color measurement and consideration of texture of the smoked fish sausages exceeded manufacturing standards.
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effect of Evaporator Section lengths and working fluids on operational limit of closed loop oscillating heat pipes with check valves clohp cv
American Journal of Applied Sciences, 2009Co-Authors: P Meena, S Rittidech, P TammasaengAbstract:This research aims to the effect of Evaporator Section lengths and working fluids on operational limit of closed loop oscillating heat pipes with check valves (CLOHP/CV) with R123 Ethanol and Water were used as the working fluids. A set of CLOHP/CV was made of copper tubes in combination of following dimension: 1.77 mm inside diameter: 10 turns: 5, 10 and 15 cm equal lengths for Evaporator, adiabatic and condenser Sections. The working fluid was filled in the tube at the filling ratio of 50%. The Evaporator Section was given heat by heater while the condenser Section was cooled by volume water in a cold bath. The adiabatic Section was properly insulated. In the test operation. Which the temperature at the adiabatic Section was controlled at 60°C in steady-state condition. From The obtained results obtained, it could be concluded as follows. When the Evaporator lengths increased from 5 cm to 10 and 15 cm the critical heat transfer flux decreased. There was working fluids change from R123 to Ethanol and water the critical heat flux decreased.
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closed ended oscillating heat pipe ceohp air preheater for energy thrift in a dryer
Applied Energy, 2005Co-Authors: S Rittidech, W Dangeton, Somchart SoponronnaritAbstract:The CEOHP air-preheater consisted of two main parts, i.e. the rectangular house casing and the CEOHP. The house casing was designed to be suitable for the CEOHP. The inside house casing divided the CEOHP into three parts, i.e. the Evaporator, the adiabatic Section and condenser Section. The CEOHP air-preheater design employed copper tubes: thirty-two sets of capillary tubes with an inner diameter of 0.002 m, an Evaporator and a condenser length of 0.19 m, and each of which has eight meandering turns. The Evaporator Section was heated by hot-gas, while the condenser Section was cooled by fresh air. In the experiment, the hot-gas temperature was 60, 70 or 80 °C with the hot-gas velocity of 3.3 m/s. The fresh-air temperature was 30 °C. Water and R123 was used as the working fluid with a filling ratio of 50%. It was found that, as the hot-gas temperature increases from 60 to 80 °C, the thermal effectiveness slightly increases. If the working fluid changes from water to R123, the thermal effectiveness slightly increases. The designed CEOHP air-preheater achieves energy thrift.
S H Noie - One of the best experts on this subject based on the ideXlab platform.
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investigation of thermal performance of an air to air thermosyphon heat exchanger using e ntu method
Applied Thermal Engineering, 2006Co-Authors: S H NoieAbstract:Abstract Experimental and theoretical research has been carried out to investigate the thermal performance of an air-to-air thermosyphon heat exchanger. Many factors affect the thermal performance of thermosyphon heat exchangers including velocity and temperature of input air, type and filling ratio of the working fluid, and pipe material. The air-to-air thermosyphon heat exchanger has been designed, constructed and tested in a test rig under steady state conditions. The lengths of both the Evaporator and condenser Sections of the heat exchanger were 600 mm and its central adiabatic Section had a length of 100 mm. The heat exchanger had 90 plate finned copper thermosyphons arranged in 6 rows. A test rig was constructed and developed wherein the heated air is recycled into the Evaporator Section of thermosyphon heat exchanger. The temperature across the Evaporator Section was varied in the range of 100–250 °C while the inlet temperature to condenser Section was nearly constant 25 °C. Distilled water was used as the working fluid with a fill ratio of 60% of the Evaporator Section length. The air face velocity ranged from 0.5 to 5.5 m/s and the heat input into the Evaporator Section was varied between 18 and 72 kW using electric heating elements. A computer simulation program based on the effectiveness-NTU method was developed to estimate the outlet temperature by iteration as well as thermal performance of the thermosyphon heat exchanger. Also several experiments were carried out under different operating conditions by varying the parameters in order to determine and investigate their effect on the thermal performance of the thermosyphon heat exchanger. The overall effectiveness of the thermosyphon heat exchanger obtained from experiments varied between 37% and 65%. The experimental results showed the minimum effectiveness of the thermosyphon took place at C h = C c . Therefore, equal value of air face velocities in Evaporator and condenser Sections should be avoided. It was shown that the experimental results were close to those obtained from computer simulation and became better as the velocity increases. The results of this experiment can be used in industrial cases.
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heat transfer characteristics of a two phase closed thermosyphon
Applied Thermal Engineering, 2005Co-Authors: S H NoieAbstract:Abstract The applications of closed two-phase thermosyphons are increasing in heat recovery systems in many industrial practices because of their high effectiveness. Various parameters affect the heat transfer performance of thermosyphons. In this paper, the effect of three parameters: input heat transfer rates ( 100 Q ˙ 900 W ), the working fluid filling ratios (30% ⩽ FR ⩽ 90%), and the Evaporator lengths (aspect ratios) were investigated experimentally. The aspect ratios for these experiments were 7.45, 9.8, and 11.8. A series of experiments were carried out to find the influence of the above parameters on steady-state heat transfer characteristics of a vertical two-phase closed thermosyphon. A smooth copper tube of total length of 980 mm with inside and outside diameters of 25 and 32 mm was employed with distilled water as working fluid. The temperature distribution along the thermosyphon was monitored; input heat to Evaporator Section and output heat from condenser were measured, as well. The experimental boiling heat transfer coefficients were compared with existing correlations. Conclusions have been drawn for the optimum-filling ratio at which the thermosyphon operates at its best for a certain aspect ratio.