Thermosyphon Tube Research Articles

Experimental study on the thermal characteristics of a 3D thermosyphon heat sink

Phase change heat transfer has received extensive attention in the thermal management of electronic devices. Most studies of heat pipe or vapor chamber were limited to one- or two-dimensional heat transfer mode. Enhancing the phase change heat transfer to three-dimensional mode in heat sinks and exploring the thermal behavior of the heat sinks deserve a dedicated study. In this paper, a three-dimensional thermosyphon (3D-TS) heat sink combining the superiorities of the vapor chamber, thermosyphon and folded fins was experimentally investigated. The experimental reliability was validated and consolidated by the heat loss analysis, and an iteration method was proposed to estimate the saturation temperature to facilitate the in-depth analysis of the results. The coupling characteristics of the air forced convection and phase change heat transfer, and the effects of the heating power and air volume flow rate on the thermal resistance of 3D-TS were involved in the discussion. The main results indicate that the overall thermal resistance exhibits a negative correlation with the heating power and the air volume flow rate. The lowest thermal resistance of 0.14 K·W−1 was achieved with Qtotal = 300 W and 100 CFM air volume flow rate. High temperature on the folded fins indicates that the phase change heat transfer extends from the flat vapor chamber to the vertical thermosyphon tubes. It is also found that for a small heating power, a relatively large air volume flow rate is not able to further reduce the overall thermal resistance due to inadequate phase change intensity. The proposed heat sink is expected to solve the heat dissipation problems for densely packed electronic devices, which can produce favorable performance according to the input heating power and appropriate air volume flow rate.

Experimental Investigation on Productivity Enhancement of a Solar Still Modified with the Evacuated Tube Heat Pipe using Paraffin Wax

The current work involves experimental investigation on a conventional solar still to improve the productivity of fresh water by introducing the evacuated tube thermosyphon heat pipe. The evacuated tube thermosyphon acts as additional heat source to the solar still. The paraffin wax was utilized as latent heat storing medium, filled between the evacuated glass tube and thermosyphon heat pipe to escalate the fresh water productivity during off-sunshine hours. Two identical solar stills, one with three evacuated tube thermosyphon and another without it, were constructed and tested simultaneously. The solar radiation intensity, volume of fresh water produced, and temperature at various points such as basin water, glass cover, ambient and evaporator and condenser section of the heat pipe were measured. The utilization of evacuated tube heat pipe as an additional heat source increases heat input by 84.5%. The increase in heat input upsurges the gathering of fresh water by more than three times when compared to the conventional solar still. Accumulative fresh water productivity from the modified solar still was 215.7% higher than fresh water productivity from the conventional solar still. The modified solar still was capable to yield fresh water during no sunshine hours of evening as an effect of utilization of phase change material. The study suggests that direct coupling of the evacuated heat pipe to the solar still performs well in terms of fresh water yield and the same can be employed for household purpose.

Experimental evaluation of a thermosyphon-based waste-heat recovery and reintegration device: A case study on low-temperature process heat from a microbrewery plant

An experimental study was conducted to design, build and test the performance of a waste-heat recovery device. Its feasibility and performance were evaluated, based on its implementation within a brewing process; recovering unallocated residual energy from wort cooling water (40 °C to 80 °C) and using it to heat cool air for barley drying (32 °C to 48 °C). Given the quality associated to the low-temperature source, thermosyphons were selected as heat conveyance device. The proposed heat recuperator design uses 18 carbon-steel thermosyphon tubes filled with a mixture of distilled water and hydrazine hydrate, as corrosion inhibitor, at 20% of the total inner volume. Given the passive nature of the device, the length ratio between the evaporation and condensation zones was also analysed, ranging from 50:50, 40:60 and 30:70. The results showed that the 50:50 length ratio was the most disadvantageous configuration available, with the lowest efficiency and heat conveyance, ascribed to a higher radial heat flux into the evaporator, thus, reducing the operation range considerably. Meanwhile, increasing condenser length, 40:60 and 30:70 length ratios, yields a higher maximum condensation heat flow, with 4.15 KW and 4.22 KW, respectively, a 31% increase. However, given the 1.2% difference between them, said increase is comparatively negligible, entailing that, for this thermosyphon setup, peak heat transfer available is reached with the 40:60 length ratio. Regarding efficiencies, it was found that the 50:50 length ratio is particularly susceptible to the thermosyphon inherent operation limits, specifically, the boiling limit. Nonetheless, all configurations have efficiencies above 50% with heat flows above 1.5 KW. Additionally, it was found that the lowest air flow velocities yield the highest achievable efficiencies, with 84%, 98% and 94%, for the 50:50, 40:60 and 30:70 length ratios respectively. Similarly, when evaluating through the thermal capacity framework, it was found that the 50:50 length ratio only possess a 8% accomplishment rate, whilst the remaining configurations, increase said rate by 20%. However, it also shows that the 30:70 length ratio yields a more dispersed dataset, which reveals that the imbalance after surpassing peak heat transfer, renders the device more susceptible to both inherent and environmental effects. From the findings it was found that the proposed device, with a 40:60 length ratio is capable of successful recover and reintegration of residual energy, without modifying existing brewhouse installation or requiring additional energy input. Therefore, the general assessment conducted proposes thermosyphon-based heat exchangers as viable alternatives for low-temperature heat recuperation beyond the case study here discussed.

Heat Transfer Performance of a Two-Phase Closed Thermosyphon.(Dept.M)

An experimental investigation has been made in order to study the heat transfer performance of a two-phase closed thermosyphon tube. A smooth copper tube of total length 1500 mm and 21 nun inside diameter is used as a container of the thermosyp hon. Each of the evaporator section and the condenser section has a length of 600 mm, while the remaining part of the thermosyphon tube is the adiabatic section. The working fluid used is R22. The effects of heat transfer rate (100 W ≤Q≤ 300 W), filling percentage (30≤%v+≤100%) and the inclination angle of the thermosyphon (22.5°≤θ≤90) are studied. It is found that, the optimum filling percentage and the best inclination angle values are 50% and 30°, respectively. The overall heat transfer coefficient ratio (U/U90) has been correlated in a dimensionless form as a function of Kutateladze number, filling ratio, inclination angle, and reduced pressure ratio.

Heat Transfer Performance of A Vibrated Two-Phase Closed Thermosyphon.(Dept.M)

An experimental investigation had been carried out in order to study the heat transfer performance of a vibrated two-phase closed thermosyphon tube. The working fluid used was R143a. The effects of heat flux (1276W/m2 ≤q≤ 6331 W/m2), filling percentage (30%≤V+≤5100%), the vibration dimensionless frequency (1.085≤ F ≤3.26), and the dimensionless amplitude (0.19 ≤ B ≤0.57) were studied. It was found that, the optimum filling percentage and the best dimensionless frequency values are 50% and 1.448, respectively. The Nusselt number had been correlated in a dimensionless form as a function of Kutateladze number, filling ratio, dimensionless frequency, dimensionless amplitude, and reduced pressure ratio.

Heat Transfer Performance of a Two Phase Closed Corrugated tube Thermosyphon (Dept.M)

The two phase closed Thermosyphons are highly sufficient heat transfer element At present. however, actual applications are mostly limited for thermosyphon using smooth tube as its container. In the present work, a corrugated. tube was used as its container with distilled water as the working fluid. The corrugated tube container is flexible and has several features to allow the thermosyphon to be used in a wide range of applications The influence of liquid filling ratio, inclination angle, evaporator heat flux and condenser to evaporator length ratio on the heal transfer performance was experimentally studied The experiments are carried out for values of heat flux of 11, 20,5. 32.8. 44 kW/m2, Filling ratios of 20,40.60, 80 and 100 % with respect to evaporator volume for thermosyphon configuration arc used. The effect of inclination angle of zero, 20, 40, 60, 80 and 90 degrees measured from the vertical axis is examined. Three different values (or length ratios between condenser to evaporator of I, 1.5 and 3 are used. According to the measured values of problem parameters, the mean heat transfer coefficient is calculated. it is found that the optimum filling ratio is in the range o( 40-60 % for both smooth and corrugated tubes. in addition, the maximum performance is Obtained at inclination angle of 40 degree Moreover. a comparison is made between corrugated tube and smooth tube at the same tested parameters.

Comparative experimental investigation of two evacuated tube solar water heaters of different configurations for domestic application of Baghdad- Iraq

Evacuated tube solar water heaters have drawbacks that limit their performance against local habits of hot water consumption, like slow water temperature rise and slow response to loading. A method to enhance their performance is using heat pipes as heat transport tools from the solar collectors to the storage water. The present work investigates the enhancement of thermal performance of evacuated tube solar water heaters subjected to (non- standard) load conditions and weather conditions of Baghdad- Iraq. Two identical evacuated tube solar water heaters (both of 120 l capacity and 20 evacuated tube solar collectors) are investigated experimentally. One system works with thermosyphon (natural convection); the other system incorporates 20 wickless heat pipes (closed thermosyphon tubes), of 16 mm diameter and 1750 mm length and are charged with methanol as working fluid at 50% fill charge ratio, as thermal conductors from the solar collectors to the storage tank. A comparison of performance of the two solar systems has been conducted by subjecting them simultaneously to different load conditions namely; no load, intermittent and continuous loading to simulate the hot water consumption habits in the local community. Extra experiments were conducted at sunny days and various weathers at no load to verify the thermal diode effect of heat pipes and the effect of weather conditions on the systems performance. Experimental results reveal an enhancement in overall daily efficiency of the heat pipe system over the thermosyphon system by 22.5% for no load, 42.5% for intermittent loading and 32.4% for continuous loading. The heat pipe system produced higher temperatures and better response at all load conditions and adverse weather conditions that make it more suitable for local domestic application. The thermosyphon system performs suitably with no load and intermittent load at small removal quantities. Results agree with those in the literature.

Experimental validation data for CFD of heat transfer processes in a heat exchanger thermosyphon type with complex geometry

The paper explores the validation of experimental studies by means of numerical modelling of heat transfer processes occurring in a two-phase thermosyphon air heater. The object analysed is an air heater, used for the utilisation of the heat from flue gases emitted by a steam generator running on solid fuel with nominal load of 125 t/h, and temperature of the flue gases at nominal load 220C. The experimental study performed shows heat transfer coefficients of the evaporation and condensation zones of hfgas = 104.9 and hfgas = 84.9 W(m2 · K) respectively, and a reduction of the exhaust gas temperature down to 184°C. The numerical study pertains to a thermosyphon tube with complex geometry. Three zones can be distinguished for the air heater in question. In the evaporation zone the tube is inclined at 30 degrees in the direction of the flue gasses, in addition to the inclines of the adiabatic zone – 30 degrees, and the evaporation zone of the thermosyphon – 90 degrees to the horizon. The commercial software Ansys Fluent was used to perform the numerical calculations.

Critical heat flux of a two-phase closed thermosyphon with fins

The critical heat fluxes (CHFs) of two-phase closed thermosyphons with and without fins were studied. The thermosyphons were fabricated using 1.25-mm-thick iron tubes with inner diameters of 16, 21 and 26 mm. The lengths of the evaporator, adiabatic, and condensation sections were 20, 10 and 20 cm, respectively. Pure water, ethanol, and R134a refrigerant were used as the working fluids with 50 % filling rate of the evaporation length. CHF data when using fins of different thicknesses (1.0, 1.5 and 2.0 mm), radii (5, 10 and 15 mm), and spacing (10, 20 and 30 mm) were recorded. The CHF increased with the fin thickness and radius but decreased with the increase in fin spacing. In addition, the CHF increased with the diameter of the thermosyphon tube. Overall, the CHF of thermosyphons with fins was higher than that of thermosyphons without fins regardless of the working fluid.

An indirect heating solution to reduce CO2 emission and improve efficiency of gas distribution networks

The gas industry relies on indirect heating to prevent gas from freezing when it is transferred from high-pressure networks to lower pressure distribution systems. The main challenge in preheating natural gas is designing an indirect heating system capable of consistently maintaining a target temperature, despite large load diversity. The most common form of heating technology has traditionally been water bath heaters and boiler houses. In this paper, a novel technology is introduced, and its performance compared to existing installations. The Immersion Tube Thermosyphon Heater was developed specifically to address high load diversity; it combines a high-efficiency immersion burner with a sub-atmospheric two-phase loop thermosyphon. The use of low-temperature steam provides a flexible and precise solution for temperature control easily adapted to variable gas flows. The Immersion Tube Thermosyphon achieved an average thermal efficiency of 90%, considerably higher than the 46% efficient water bath, allowing an estimated annual saving of 7,660 tonnes CO2 for 1-megawatt gross heat capacity operating with a 50% load factor.

Experimental Study of Heat Transfer in the Steam Thermal Siphon Tube Channel

The results of experimental studies of heat transfer into the thermo-syphon tube with different thermal loads are represented. Are examined two types of liquid as the working fluid. The values of temperatures in the steam channel of thermo-syphon tube are registered and the dependences of the coefficients of heat exchange on the power of heating element are obtained. The influence of thermal load and properties of liquid on the intensity of the processes of evaporation and condensation of working fluid in the thermo-syphon installation are established.

열사이폰관형 태양열집열기를 주열원으로 하는 하이브리드 난방시스템 성능 평가

지열, 풍력, 태양열에너지 등과 같은 신재생에너지 분야에 관한 연구가 활발히 이루어지고 있으나 전체 에너지 중에서 차지하는 비율은 아직 미미하다. 본 논문은 주열원인 열사이폰관형 태양열집열기와 보조열원인 X-L 파이프 보일러장치를 서로 결합한 하이브리드 난방시스템에 관한 연구이다. 특히 새로운 형태의 열사이폰관형 태양열집열기에 관한 성능 평가와 함께 보조열원장치의 성능 및 안전성에 대해 조사하였다. 그 결과, 열사이폰관형 태양열집열기는 이중관형 태양열집열기보다 집열효율이 그 구조적 특성 때문에 최대 20.7% 더 증가하였다. 또한 보조열원장치의 X-L 파이프 내 특수열매체는 순수 물보다 약 20% 더 빠르게 온도가 상승하였으며, X-L 파이프 보일러는 안정성 때문에 팽창압력 해소장치가 필요함을 확인하였다. Recently, even though the researches on renewable energy like geothermal, wind, solar energy have been performed widely, its use-rate in total energy is still low. This study was carried out to investigate the performance of hybrid heating system, which consisted of solar collector of thermosyphon tube type and X-L pipe boiler. Especially, new type of solar collector was tried and compared with double tube type and, futhermore, performance and safety on X-L pipe boiler were investigated. As the results, efficiency of solar collector of thermosyphon tube type was higher 20.7% than that of double tube type, mainly due to its structural characteristics. It was also confirmed that temperature of special heat medium used X-L pipe boiler rose up about 20% rapidly in comparison with that of pure water.

Computational Study of Hybrid Water Heater with Evacuated Glass Tube Solar Collector and Rice Husk Combustion

Problem statement: The thermal performance modeling of hybrid water heater with evacuated glass tube solar collector and flue gas of rice husk combustion was developed. The solar global radiation and ambient air temperature data used in the system modeling belongs Phitsanulok province from 7 am-5 pm in the summer season. Approach: The system can be divided into two parts, i.e., evacuated glass tube thermosyphon solar collector and thermosyphon heat exchanger with flue gas of rice husk combustion. The evacuated glass tube was a coaxial double-layer tube made of Borosilicate. Its outer tube diameter and inner tube diameter were 58 and 47 mm respectively. The inside cavity of evacuated glass tube holed thermosyphon which was made of copper tube and filled with R134a at the filling ratio of 70% of evaporator volume. For latter, the temperature and flow rate of flue gas that was released from the cyclone furnace and used as a heat source of heat exchanger were constant at 150°C and 50 m3 min-1. The heat exchanger was consisted of array of thermosyphon which was made of stainless steel tube and filled with distilled water at 50% filling ratio of evaporator volume. Results: The effects of various parameters on the system performance were computational analyzed. The hybrid water heater system with optimum design of both thermal performance and economic can be obtained and produce the hot water at the temperature exceeding 70°C and the flow rate of 1 m3 day-1. Conclusion: The thermal performance of this optimum hybrid water heater system was investigated along the time of the day in summer.

Performance of a Two-Phase Carbon Dioxide-Filled Thermosyphon

In order to utilize low enthalpy geothermal heat sources, a thermosyphon is a good device which can extract heat without using electric power. The heat transfer in the thermosyphon occurs through the circulation of a working fluid through a sequence of evaporation, vapor transfer, condensation, and liquid return. A two-phase thermosyphon system using carbon dioxide (CO2) as a working fluid has been investigated both experimentally as well as theoretically. Carbon dioxide is the only non-flammable and non-toxic fluid that has the potential to offer environmental safety in a system. A copper tube thermosyphon of total length of 1,000 mm with inside and outside diameters of 9.9 mm and 12.7 mm was developed by consisting of evaporator and condenser sections. The temperature distribution along the thermosyphon was monitored and theninput heat to evaporator section and output heat from condenser were measured as well. The effects of temperature difference between evaporator and condenser section and coolant mass flow rates on the performance of the thermosyphon were determined. The results indicate that the heat flux transferred increased with increasing coolant mass flow rate and temperature difference between evaporation and condenser section. The experimental analysis of the thermosyphon system confirms that the proposed system must be a reliable and highly efficient as well as environmentally friendly alternative to common ground-coupled systems.

Heat Transfer in a Reciprocating Thermosyphon Fitted with Staggered Transverse Ribs

This paper describes an experimental investigation of heat transfer in a reciprocating antigravity open thermosyphon. The thermosyphon tube is square in cross section, and two opposite walls are roughened with staggered transverse ribs. This flow/heat-transfer system has relevance, as a fundamental study, to the shaker-cooling system for the pistons of reciprocating engines. A series of experiments are undertaken to demonstrate the complex interaction that exists between inertial, reciprocating, and buoyancy forces on the performance of this form of cooling system. It is shown that reciprocation of the system significantly improves heat transfer in comparison with the stationary antigravity thermosyphon performance. The buoyancy effects from gravity and reciprocation improve heat transfer. Reductions in the effectiveness of buoyancy forces are produced when the relative strengths of inertial or/and pulsating forces increase. In the extrapolated case of zero buoyancy, it was found that the local heat transfer along the thermosyphon tube was reduced in comparison to the static case at relatively low levels of reciprocation frequency. As the reciprocation frequency was increased, this effect was reversed and heat transfer improved in comparison with the stationary case.

Enhanced Heat Transfer of Shaker-Bored Piston Cooling Channel with Twisted Tape Insert

This experimental study investigates the heat transfer augmentation in a reciprocating anti-gravity open thermosyphon using a twisted tape insert with relevance to the “shaker-bored” piston cooling system for marine propulsive diesel engine. A selection of experimental data illustrates the interactive effects of inertial, reciprocating, and buoyancy forces on heat transfer in the anti-gravity open thermosyphon with and without a twisted tape insert for subcooled and superheated conditions. The impacts of gravitational buoyancy on heat transfer in the static plain thermosyphon tube are reversed from impairing to improving heat transfer when the flow condition yields from subcooled to superheated condition. In the static thermosyphon tube fitted with twisted tape insert and in the reciprocating thermosyphon tubes with and without twisted tape insert, the buoyancy interactions enhance heat transfer coefficients. Due to the isolated reciprocating force effect, heat transfer coefficients are initially impaired from the static levels at low pulsating numbers but recovered to be enhanced at high pulsating numbers in the reciprocating plain thermosyphon tube. For the reciprocating thermosyphon tube fitted with a twisted tape insert, the isolated reciprocating force effect consistently improves heat transfer. The impacts of isolated reciprocating force and buoyancy interaction on heat transfer are Reynolds number-dependent. Heat transfer coefficients in the reciprocating thermosyphon tube fitted with the twisted tape insert could be augmented to the range of 1.2–6 times of plain tube levels. A set of empirical heat transfer correlations that considers the synergistic effects of inertial force, reciprocating force, and buoyancy interaction in the reciprocating anti-gravity open thermosyphon tube fitted with a twisted tape insert is developed to assist the design activity of the piston-cooling system.

21818 密閉二相熱サイフォン内熱伝達の解析(熱工学(2))

About a single tube thermosyphon, we performed numerical analysis about a heat transfer characteristic of the condenser section. And we examined it about temperature distribution of condenser section heat transfer surface and influence of distribution of a wall surface heat-transfer coefficient by comparing an analysis result with experimental value of the past. As a result, at the time of charge ratio 90% and coolant temperature 50℃, we got the analysis result that was near to experimental result. We were able to confirm that condenser wall temperature lowered when changed a local heat-transfer coefficient and analyzed it. There was not most of the influence to an average heat-transfer coefficient then.

Start-up from the frozen state of two-phase thermosyphons

In a cold region, ethylene glycol or propylene glycol aqueous solution is usually used as a working fluid of thermosyphons, because if pure water is used as a working fluid, the thermosyphon tube breaks due to the volume expansion of ice when water freezes into ice. If a non-freeze working fluid is required, for example, under the environmental temperature of −20 °C, around 37 mass% ethylene glycol aqueous solution must be used. Usually, two-phase heat transfer coefficients of binary mixtures become lower than pure liquid. As the concentration of ethylene glycol increases, the freezing point lowers, and then the heat transfer coefficient also lowers. Therefore, if the small concentration of ethylene glycol is used, the degradation in heat transfer may be small. In the present study, 1–40 mass% ethylene glycol aqueous solutions were prepared, and they were poured into glass test tubes, respectively. These glass test tubes were immersed in ethanol of −20 °C to −40 °C, which were cooled down by a refrigerator. Consequently, the test tube with pure water was cracked and broken, but the other test tubes were not broken even in the case of 1 mass% concentration. Since the above fact was found, the start-up experiment from the frozen state of the two-phase thermosyphon was carried out using 1 and 2 mass% ethylene glycol aqueous solutions as the working fluid. As a result, it was revealed that these thermosyphons started up smoothly without any troubles.

나선 그루브형 열사이폰의 작동유체의 변화에 대한 응축열전달 성능에 관한 연구

This study concerns the performance of condensing heat transfer in two-phase closed thermosyphons with various helical grooves. Distilled water, methanol, ethanol have been used as the working fluid. In the present work, a copper tube of the length of 1200mm and 14.28mm of inside diameter is used as the container of the thermosyphon. Each of the evaporator and the condenser section has a length of 550mm, while the remaining part of the thermosyphon tube is adiabatic section. A experimental study was carried out for analyzing the performances of having 50, 60, 70, 80, 90 helical grooves. A plain thermosyphon having the same inner and outer diameter as the grooved thermosyphons is also tested for the comparison. The type of working fluid and the numbers of grooves of the thermosyphons with various helical grooves have been used as the experimental parameters. The experimental results have been assessed and compared with existing theories. The results show that the type of working fluids are very important factors for the operation of thermosyphons. And the maximum enhancement (i.e. the ratio of the heat transfer coefficients the helical thermosyphons to plain thermosyphons) is for condensation.

Performance of a two-phase closed thermosyphon solar collector with a shell and tube heat exchanger

In the present study, a two-phase closed thermosyphon flat-plate solar collector with a shell and tube heat exchanger was investigated experimentally under the field conditions of Cairo, Egypt. The collector was designed, constructed, and tested at transient conditions to study its performance for different cooling water mass flow rates at different inlet cooling water temperatures. Also the effect of the number of the thermosyphon tubes on the performance of the collector was investigated. Under different climate conditions, the experimental results showed that the optimal mass flow rate is very close to the ASHRAE standard mass flow rate for testing conventional flat-plate solar collectors. Also, the experimental results indicated that the number of the thermosyphon tubes has a significant effect on the collector efficiency. The performance of the present collector with optimum number of thermosyphon tubes was compared with the performance of two-phase closed thermosyphon flat-plate solar collectors with tube in tube heat exchangers of previous investigators and a better performance for the present collector was obtained at high inlet water temperature.