Radial Heat Pipe Research Articles

Thermal performance improvement of a radial pulsating heat pipe with diverging channels by adopting Tesla valves at various heat fluxes

The thermal performance of a pulsating heat pipe (PHP) can be improved by increasing the flow circulation with the adoption of novel channel designs to minimize flow resistance. This study aimed to improve the thermal performance characteristics of a radial PHP with diverging channels by adopting Tesla valves. The effects of heat flux, condensation temperature, and heat transfer area ratio on the thermal resistance and heat transfer coefficient of the PHP with Tesla valves were measured under different heating and cooling conditions. In addition, the flow behaviors and pressure variations were analyzed for a short time frame. The PHP with Tesla valves exhibited a 17 %-lower thermal resistance than that without Tesla valves owing to the increased flow circulation with preferential movement in one direction. Furthermore, the heat transfer capability of the PHP with Tesla valves increased with increasing condensation temperature and heat transfer area ratio at the same heat flux. In addition, the optimal filling ratios were determined to be 70, 80, and 90 % for heat transfer area ratios of 0.13, 0.08, and 0.05, respectively. Finally, contour maps for the maximum temperature deviation were developed in terms of the heat flux, heat input, and heat transfer area ratio.

Numerical Investigation on the Thermal Performance of Three Advanced Micro Heat Pipes

Three micro heat pipes belonging to different types are selected as the research objects due to their lowest thermal resistance and the steadiest operation according to published literatures. They are the pulsating heat pipe with corrugated configuration (CPHP), the flat-plate heat pipe with eight microchannels (FPMHP) and the radial pulsating heat pipe (RPHP). A mathematical model common to the three micro heat pipes is built, and the maximum deviation between simulation and actual results is 16.1%. It is found that CPHP has the best heat transfer performance with the minimum thermal resistance of 1.14 K·W−1. Its average wall temperature and center-line velocity regularly oscillate after the start-up point. There is a pause phenomenon of motion for CPHP, and the pause period of motion decreases from 8.93 s to 7.25 s with the increasing input heat flux. RPHP possesses the most excellent temperature uniformity with the maximum axial temperature difference of 5.24 K. Furthermore, FPMHP is suitable for cooling temperature-resistant devices because its average wall temperature of evaporation section is the highest.

Thermo-hydrodynamic analytical model, numerical solution and experimental validation of a radial heat pipe with internally finned condenser applied for building heat recovery units

Heat pipes have been extensively applied in the domain of energy conversion and heat recovery application. A novel radial heat pipe with internally finned condenser has been proposed to recover waste heat from air conditioning units. Full mathematical description and computational fluid dynamics model were developed to predict the loop flow and thermal performance in a single radial heat pipe, respectively. The research focuses mainly on the effects of input power, filling ratio, pipe diameter, and velocity of the cooling water on the thermal performance and entropy generation rate of this novel heat pipe. Numerical results illustrate that average reductions in total thermal resistance with utilization of fins approximately achieved 8.69% and 14.78% for fins nf = 4 and nf = 8, respectively. Similarly, entropy generation rate shows an average decrease of 19.4% and 37.5% for identical operations. Additionally, the effect of internally finned condenser on the multiphase fluid flow has been comprehensively analyzed, including the break of the condensed film, generation of bubbles and nucleation boiling. The results further indicate that incorporation of internal fins has a significant influence on enhancing thermal homogenization and waste thermal recovery efficiency of a radial heat pipe. Case results agreed well with experimental data within average deviation being no more than 10%.

The Integration technology of desulfurization, denitration and heat recovery from coke oven flue gas

The main components of coke oven flue gas were SO2, NOX etc. SO2 and NOX were not only harmful to human health, but also seriously polluted the environment. The stricter “Standard for Discharge of Pollutants from coking chemical industry” was introduced. An integration settlement scheme of flue gas desulfurization, denitration and waste heat recovery was put forward. The proprietary core technologies, such as denitration, COG desulfurization and radial heat pipe boiler were researched. The integration settlement scheme can solve the problems of polluting the environment and waste heat without recovery, which had not only significant economic benefits, but also huge social benefits.

Experimental and numerical investigations of a radial heat pipe for waste heat recovery

In the present work, a novel heat transfer device, radial heat pipe (RHP) has been investigated due to lower flow resistance. Mathematical and computational fluid dynamics (CFD) models have been developed to investigate their thermal performance and two phases flow process inside RHP. The steady-state theoretical model of RHP has been employed to investigate the influence of various filling ratio range of (0–60%) of water and three different values of heat input (3267 W, 4004 W and 4817 W) on the thermal performance of a RHP at different operating conditions. CFD simulations further demonstrate that present built VOF model could effectively reproduce phases-change fluid flow and heat transfer inside RHP. Phenomena such as nucleation boiling, coalescence of bubbles, formation of the liquid film were observed in the heat pipe. Moreover, numerical modelling results were well validated by the experimental tests for various conditions, and maximum deviation falls within 10%.

Numerical Simulation and Optimization of Radial Heat Pipe Heat Exchanger Based on Field Synergy Principle

This paper mainly explores the numerical simulation of flow and temperature fields in the shell-side of the radial heat pipe heat exchangers (HPHE), using CFD software-FLUENT. Field synergy principle is applied to analyze heat and mass transfer mechanism of heat exchangers; also, the influence of the variation of principle constructor parameters of heat exchangers on the field synergy effect and heat exchange performance has been studied. It has been found that better performance of heat exchangers is achieved with better field synergy effect; in the context of increasing transverse and longitudinal tube pitches within certain values of data, the heat transfer coefficient decreases as synergy angle increases. Variation of fin height has little effect on synergy angle, but it would decrease the heat transfer coefficient at unit pressure drop (k/Δp) as it increases; as fin pitch increases, the synergy angle first decreases and then grows, while k/Δp first increases and then decreases. The optimal ranges of heat exchanger structure parameters values were found.

Experimental Research of Thermal Characteristics in Coaxial Radial Heat Pipe

In this paper, heat transfer model is assumed in coaxial radial heat pipe(CRHP) firstly. To verify the model , visualization and performance experiment are studied. Visualization experiments of CRHP are done under different filing radio of 20%, 30%, 35% and inclined angles of 0°(horizontal), 5°, 10°, 15°, 20°. Visualization experimental results show that CRHP of horizontal and 30% filling ratio is better on thermal characteristics. Its heat transfer model is preliminary analyzed from experimental phenomena. In performance experiment , the kind of CRHP is used to test heat transfer characteristics. The temperatures of the outside wall of outer pipe are determined and drawn diagrams. Lastly, heat transfer model is corrected anew by analyzing experimental datas.

Experimental study and analysis on heat transfer coefficient of radial heat pipe

The experimental study was performed on five eccentric radial heat pipes with two outer-tube diameters. The test range can be given as follows, working fluid filling ratio Ω=44%∼83%, heat flux q=10000W/m2∼32000W/m2, and working temperature tv=50°C∼120°C. The correlations between radial heat pipe heat transfer performance and filling ratio, heat flux, working temperature were studied in the experiment. Based on linear regression of experimental data, the relationship between heat pipe equivalent heat resistance R and working temperature tv, heat flux q and filling ratio Ω was obtained.