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A S Elasfouri - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis of laminar film condensation heat transfer inside inclined wickless heat pipes flat plate solar collector
Renewable Energy, 2001Co-Authors: H M S Hussein, M A Mohamad, A S ElasfouriAbstract:The present work presents a steady state two-dimensional theoretical analysis of laminar film condensation heat-transfer inside the Condenser Section of inclined wickless heat pipes flat-plate solar collector. A theoretical relation for the laminar film condensation heat-transfer coefficient is deduced and compared with the previous work. The comparison indicates good agreement between the present relation and most of the experimental results previously published. The present relation is preferred to the previously published empirical and theoretical relations. This is because it is valid for wide ranges of the wickless heat pipes inclination angles and the Condenser Section dimensions ratio.
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optimization of a wickless heat pipe flat plate solar collector
Energy Conversion and Management, 1999Co-Authors: H M S Hussein, M A Mohamad, A S ElasfouriAbstract:The transient thermal behaviour of wickless heat pipe flat plate solar collectors has been analyzed with regard to various parameters. These parameters include global solar radiation intensity, inlet cooling water temperature, absorber plate material and thickness, ratio of pitch distance to wickless heat pipe diameter and ratio of Condenser Section length to total wickless heat pipe length. The results show that the selection of an absorber plate having a high value of conduction heat transfer rate per unit temperature difference is limited by the pitch distance.
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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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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heat transfer characteristics of a closed loop oscillating heat pipe with check valves
Applied Energy, 2007Co-Authors: S Rittidech, N Pipatpaiboon, P TerdtoonAbstract:The heat-transfer characteristics of this system i.e. a CLOHP/CV, depend on the ratio of check valves (Rcv), aspect ratio (Le/di) and the dimensionless parameters of the heat transfer. The CLOHP/CV used employed a copper tube with inner diameters of 1.77 and 2.03 mm. The evaporator, adiabatic and Condenser lengths were equal to 50, 100 and 150 mm. The selected working fluids were water (H2O), ethanol (C2H5OH) and R123 (CHCl2CF3) with a filling ratio of 50% of total volume. The number of turns was 40. The Rcv values were 20, 8, 5 and 4. The evaporator was heated by hot water, while the Condenser Section was cooled by distilled water. The inclination of the CLOHP/CV used in the experiments was 90° to the horizontal, with a controlled working-temperature of 50 °C. When the system reached the steady state, the temperature and the flow rate of the cooling water were measured in order to calculate the heat-transfer rate of the CLOHP/CV. The experimental results showed that the heat-flux increases with an increase of Rcv and decreases with an increased aspect ratio. A correlation for predicting the heat-transfer rate for the heat-pipe in the vertical position has been established.
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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.
H M S Hussein - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis of laminar film condensation heat transfer inside inclined wickless heat pipes flat plate solar collector
Renewable Energy, 2001Co-Authors: H M S Hussein, M A Mohamad, A S ElasfouriAbstract:The present work presents a steady state two-dimensional theoretical analysis of laminar film condensation heat-transfer inside the Condenser Section of inclined wickless heat pipes flat-plate solar collector. A theoretical relation for the laminar film condensation heat-transfer coefficient is deduced and compared with the previous work. The comparison indicates good agreement between the present relation and most of the experimental results previously published. The present relation is preferred to the previously published empirical and theoretical relations. This is because it is valid for wide ranges of the wickless heat pipes inclination angles and the Condenser Section dimensions ratio.
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optimization of a wickless heat pipe flat plate solar collector
Energy Conversion and Management, 1999Co-Authors: H M S Hussein, M A Mohamad, A S ElasfouriAbstract:The transient thermal behaviour of wickless heat pipe flat plate solar collectors has been analyzed with regard to various parameters. These parameters include global solar radiation intensity, inlet cooling water temperature, absorber plate material and thickness, ratio of pitch distance to wickless heat pipe diameter and ratio of Condenser Section length to total wickless heat pipe length. The results show that the selection of an absorber plate having a high value of conduction heat transfer rate per unit temperature difference is limited by the pitch distance.
M A Mohamad - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis of laminar film condensation heat transfer inside inclined wickless heat pipes flat plate solar collector
Renewable Energy, 2001Co-Authors: H M S Hussein, M A Mohamad, A S ElasfouriAbstract:The present work presents a steady state two-dimensional theoretical analysis of laminar film condensation heat-transfer inside the Condenser Section of inclined wickless heat pipes flat-plate solar collector. A theoretical relation for the laminar film condensation heat-transfer coefficient is deduced and compared with the previous work. The comparison indicates good agreement between the present relation and most of the experimental results previously published. The present relation is preferred to the previously published empirical and theoretical relations. This is because it is valid for wide ranges of the wickless heat pipes inclination angles and the Condenser Section dimensions ratio.
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optimization of a wickless heat pipe flat plate solar collector
Energy Conversion and Management, 1999Co-Authors: H M S Hussein, M A Mohamad, A S ElasfouriAbstract:The transient thermal behaviour of wickless heat pipe flat plate solar collectors has been analyzed with regard to various parameters. These parameters include global solar radiation intensity, inlet cooling water temperature, absorber plate material and thickness, ratio of pitch distance to wickless heat pipe diameter and ratio of Condenser Section length to total wickless heat pipe length. The results show that the selection of an absorber plate having a high value of conduction heat transfer rate per unit temperature difference is limited by the pitch distance.
Sauro Filippeschi - 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.