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Heat Transfer Augmentation of Latent Heat Thermal Storage Systems Employing Extended Surfaces and Heat Pipes
Published in Moghtada Mobedi, Kamel Hooman, Wen-Quan Tao, Solid–Liquid Thermal Energy Storage, 2022
Embedding the heat pipes as passive, two-phase thermal devices in an LHTS system is an effective method to enhance the heat transfer in PCM and improve its efficiency. Heat pipe has a closed structure containing working fluid which is able to transfer a large amount of thermal energy between the evaporator and condenser sections of the heat pipe during phase change processes. Robak et al. [53] investigated the melting and solidification of n-octadecane utilizing heat pipes or fins. The findings showed that the heat pipe-assisted systems reduce both melting and solidification times by 50% compared to the fin-assisted system. Figure 7.10 presents the Photographs of the melting and solidification processes in the benchmark, heat pipe-assisted, and fin-assisted enclosures. The remarkable impact of employing heat pipes on heat transfer enhancement is evident in both melting and solidification processes.
Modular Systems for Energy Usage in Buildings
Published in Yatish T. Shah, Modular Systems for Energy Usage Management, 2020
The above-described heat tube imparts several advantages to passive solar water heating systems. The heat pipe has excellent thermal conductance in that it has very high heat transfer capability over even a relatively small temperature gradient. In addition, the evaporation–condensation cycle provides highly anisotropic, essentially one-way heat transfer along the tube. It may help to consider the situation at night or during other periods of low incident solar radiation for better understanding. At such times, there is little or no evaporation and condensation of the working fluid; the fluid in its liquid state pools at the low incident solar radiation. At such times, there is little or no evaporation and condensation of the working fluid; the fluid in its liquid state pools at the low incident solar radiation. The resulting discontinuity in the conduction path between the absorber/concentrator and the tank essentially eliminates heat loss via the working fluid. The combined result of the excellent thermal conductance characteristics and the one-way heat transfer characteristics is very efficient heat transfer along the heat pipe into the reservoir with little outward heat loss. Other advantages of adapting heat tubes to passive solar collectors, not exhaustive, include relatively lightweight; adaptability to freeze protection, since only the reservoir tank contains water; and a high percentage net usable system energy, since little or no parasitic power consumption is required to operate the system.
Effect of various geometrical parameters on the thermal performance of an axially grooved heat pipe
Published in Alka Mahajan, B.A. Modi, Parul Patel, Technology Drivers: Engine for Growth, 2018
Akshay Desai, V.K. Singh, R.R. Bhavsar, R.N. Patel
Heat pipes are highly efficient heat transfer devices which use evaporation and condensation of working fluid to transfer a large amount of heat with very little temperature gradient between the heat source (hot end) and heat sink (cold end) within a closed metallic tube having a capillary wick structure on the internal periphery for circulation of the working fluid. For spacecraft thermal control, axially grooved heat pipes are used as a part of honeycombed structural panels and act as isothermalizers (Rassamakin et al., 1997). Wire mesh and sintered heat pipes perform excellently in microgravity or terrestrial conditions for a short distance but they are not viable for long-distance heat transportation (>1 meter) due to the large pressure drop experienced in liquid (Engelhardt, 2008; Kempers et al., 2006). Axially grooved heat pipes have long-distance heat transportation capability, with a wide range of operation, flexibility, reliability, low manufacturing cost and less pressure drop in liquid over wire mesh and sintered powder heat pipes (Hoa et al., 2003).
Investigating the effect of the presence of a pulsating heat pipe on the geometrical parameters of the microchannel heat sink
Published in Numerical Heat Transfer, Part A: Applications, 2023
Mohammad Ahmadian-Elmi, Mohammad Reza Hajmohammadi, Seyed Salman Nourazar, Kambiz Vafai, Mohammad Behshad Shafii
One of the primary cooling systems in electronic devices is heat pipes [23], whose performance is based on the phase change of the working fluid inside the pipes. Due to the very high effective thermal conductivity (more than several thousand times larger than copper) and insignificant thermal resistance, heat pipes are one of the most suitable cooling devices for electronic devices, and due to high heat dissipation, this cooling method has a special place in the electronic industry [24–26]. A heat pipe is a system with very high thermal conductivity, no moving components, and the ability to efficiently transport large amounts of heat without needing external input power. Heat pipes have other advantages, some of which are: noiseless cooling, long life, low cost, many applications (due to simple and durable design and construction), small size and weight (suitable for modern electronic devices), and, more importantly, it does not have harmful side effects on the environment and electronic devices. Different types of heat pipes are used in electronic cooling, which include: Vapor chambers [27], Flat heat pipes [28], and pulsating (oscillating) heat pipes [29].
Heat-Pipe Heat Exchangers for Salt-Cooled Fission and Fusion Reactors to Avoid Salt Freezing and Control Tritium: A Review
Published in Nuclear Technology, 2020
Bahman Zohuri, Stephen Lam, Charles Forsberg
Heat pipes are used today for a wide variety of applications from electronics to building heating to space nuclear reactors. Recent work with sodium heat pipes includes a 2018 ground demonstration of a nuclear space reactor with sodium heat pipes1 to move heat from the reactor to the power cycle. Today sodium heat pipes are being considered for microreactors2 with power ratings up to 15 MW(electric). The interest in microreactors implies development of heat exchangers at the multi-megawatt scale using sodium heat pipes—the same base technology that would be used for salt-cooled fission and fusion reactors with the added considerations of (1) heat transfer shutdown as liquid salts approach their melting points to avoid freezing salt and (2) control of tritium.
Influence of Inclination Angle on the Start-up Performance of a Sodium-Potassium Alloy Heat Pipe
Published in Heat Transfer Engineering, 2018
Qing Guo, Hang Guo, Xiao Ke Yan, Fang Ye, Chong Fang Ma
In heat pipes, a large amount of heat is transferred from the evaporator section to the condenser section with a small temperature drop only when a continuously effective evaporation and condensation of the working fluid occurs inside the tube. The cyclical movement of the condensed working fluid at the condenser section of GHPs, which are known as wickless heat pipes, is mainly driven by gravity force with respect to capillary force. Thus, the evaporator section of GHPs is generally placed below the condenser section in the process of the practical operation. Gravitational force along the axial direction, which is varied with the inclination angel (from vertical direction) changing of the heat pipe, is one of the major factors that affects the movement of the gas-liquid PCM and thermosyphons of GHPs. An experimental investigation certified that inclination angle significantly impacts inside vapor movement and liquid reflex behaviors in low-temperature thermosiphon devices [22]. Therefore, understanding the influence of the inclination angle on the start-up is necessary to promote transfer behavior of PCMs, decrease the temperature difference, and enhance heat transfer performance in Na-K GHPs.