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Heat pipes are promising heat removal devices widely used in a variety of fields ranging from thermal management of electronic components to terrestrial and aerospace applications. Their working principle, phase change of a working fluid, makes them superior to other conventional cooling methods. Heat pipes have been commercially available since the mid of 1960’s. Only in the past few years the electronics industries have embraced heat pipes as reliable, cost-effective solutions for high end cooling applications. This paper presents a detailed review of the materials, applications and performance of heat pipes using nanofluid as working medium. The first section reviews the heat pipes which are operating with nanofluid as working fluid. This section deals with nanofluid of different nanoparticles. The second section reviews heat pipes coated with different types of nanoparticles and third section reviews the performance of heat pipes with nanoparticle coated wick. [ABSTRACT FROM AUTHOR]

Cryogenic loop heat pipes (CLHPs) are promising thermal links between the cryocoolers and the cooled components. This paper presents a prototype of cryogenic loop heat pipe working in the temperature range from 77 K to 100 K with nitrogen as working fluid, whose high heat transfer capacity was investigated in the earlier work. Besides a main loop, the prototype introduced a secondary loop with responsibility for the cool down and the thermal management of the CLHP during the operation. In this paper, a series of experiments were performed by changing the heat loads on the secondary evaporator during the operating process. The results were compared and analyzed to investigate the influence of the secondary evaporator to the performance of the CLHP. Beneficial conclusions were also obtained and demonstrated. [ABSTRACT FROM AUTHOR]

The paper proposes a design of a condensing heat exchanger of thermosyphon loop heat pipe for cooling of electrotechnical box. The heat pipe appears to be a very good cooling device that does not require any mechanical device in its construction. A heat pipe is a structurally simple device capable of transmitting high heat flows over relatively long distances. It may be of circular or other cross-section. If one part of the heat pipe is heated - the evaporator and the other cooled - the condenser, there is a constant evaporation and condensation of the working fluid. The section between the evaporator and the condenser where there is no phase change is called adiabatic section. The heat transfer in the heat pipe is based on the phase change principle. The design of the condensing exchanger must ensure condensation of the vapor phase and heat the environment to the surrounding environment in an ideal state only by natural convection. The article describes the design of a condensing exchanger and the impact of the amount of working fluid on performance heat pipes. [ABSTRACT FROM AUTHOR]

Pulsating heat pipe (PHP) is a new, promising yet ambiguous technology for effective heat transfer of microelectronic devices where heat is carried by the vapor plugs and liquid slugs of the working fluid. The aim of this research paper is to better understand the operation of PHP through experimental investigations and obtain comparative results for different parameters. A series of experiments are conducted on a closed loop PHP (CLPHP) with 8 loops made of copper capillary tube of 2 mm inner diameter. Ethanol is taken as the working fluid. The operating characteristics are studied for the variation of heat input, filling ratio (FR) and orientation. The filling ratios are 40%, 50%, 60% and 70% based on its total volume. The orientations are 0° (vertical), 30°, 45° and 60°. The results clearly demonstrate the effect of filling ratio and inclination angle on the performance, operational stability and heat transfer capability of ethanol as working fluid of CLPHP. Important insight of the operational characteristics of CLPHP is obtained and optimum performance of CLPHP using ethanol is thus identified. Ethanol works best at 50-60%FR at wide range of heat inputs. At very low heat inputs, 40%FR can be used for attaining a good performance. Filling ratio below 40%FR is not suitable for using in CLPHP as it gives a low performance. The optimum performance of the device can be obtained at vertical position. [ABSTRACT FROM AUTHOR]

This paper gives an overview of several published current studies concerning heat transfer enhancement on the double pipe heat exchanger. Since double pipe heat exchanger has drawn much consideration due to simplicity and wide-range utility. The flow manipulation technique to enhance heat transfer in a double pipe heat exchanger has been frequently cited. Also, various research addressing working fluid on a double pipe heat exchanger has been discussed in detail. Another technique is known as surface modification that has an infrequent investigation comparing the other techniques. Correlation of Nusselt number and pressure drop coefficient shown in this overview. Future research opportunities are mentioned. [ABSTRACT FROM AUTHOR]

As for a specific flat loop heat pipe which our lab designed, with pure water as the working fluid, we have performed a series of experiments for six different fluid inventory(36.5%, 58.3%, 63.6%, 68.0%, 74.6%, 86.2%) under the same condition to study the effect of fluid inventory on the heat transfer performance. This is a meaningful work for choosing more suitable fluid inventory for LHPs. The results show that, the LHPs with 58.3%, 63.3% and 68.0% fluid inventory were relatively better on the heat transfer performance. Below 60W, the operating temperature of 58.3% was the lowest; above 60W, the 63.3% was the lowest. Under the same heat load, the loop resistance of 58.3% was the lowest. When it came to the system resistance, below 60W, the 58.3% showed the lowest; while above 60W, 63.6% showed the lowest. [ABSTRACT FROM AUTHOR]