Showing papers on "Heat pipe published in 2012"

Review and Advances in Heat Pipe Science and Technology

Abstract: Over the last several decades, several factors have contributed to a major transformation in heat pipe science and technology applications The first major contribution was the development and advances of new heat pipes, such as loop heat pipes (LHPs), micro and miniature heat pipes, and pulsating heat pipes (PHPs) In addition, there are now many commercial applications that have helped contribute to the recent interest in heat pipes For example, several million heat pipes are manufactured each month for applications in CPU cooling and laptop computers Numerical modeling, analysis, and experimental simulation of heat pipes have significantly progressed due to a much greater understanding of various physical phenomena in heat pipes as well as advances in computational and experimental methodologies A review is presented hereafter concerning the types of heat pipes, heat pipe analysis, and simulations

A review of heat pipe systems for heat recovery and renewable energy applications

Abstract: Advancements into the computational studies have increased the development of heat pipe arrangements, displaying multiphase flow regimes and highlighting the broad scope of the respective technology for utilization in passive and active applications. The purpose of this review is to evaluate current heat pipe systems for heat recovery and renewable applications utility. Basic features and limitations are outlined and theoretical comparisons are drawn with respect to the operating temperature profiles for the reviewed industrial systems. Working fluids are compared on the basis of the figure of merit for the range of temperatures. The review established that standard tubular heat pipe systems present the largest operating temperature range in comparison to other systems and therefore offer viable potential for optimization and integration into renewable energy systems.

A review of the applications of heat pipe heat exchangers for heat recovery

Abstract: The waste heat recovery by heat pipes is accepted as an excellent way of saving energy and preventing global warming. This paper is a literature review of the application of heat pipes heat exchangers for the heat recovery that is focused on the energy saving and the enhanced effectiveness of the conventional heat pipe (CHP), two-phase closed thermosyphon (TPCT) and oscillating heat pipe (OHP) heat exchangers. The relevant papers were allocated into three main categories, and the experimental studies were summarized. These research papers were analyzed to support future works. Finally, the parameters of effectiveness of the CHP, TPCT and OHP heat exchangers were described. This review article provides additional information for the design of heat pipe heat exchangers with optimum conditions in the heat recovery system.

Optimization of power and efficiency of thermoelectric devices with asymmetric thermal contacts

Abstract: We report the theoretical efficiency of thermoelectric power generation with asymmetric thermal contacts to reservoirs A key ingredient is the electrical and thermal co-optimization Generic formula of the maximum power output and the optimum leg length are obtained The Curzon-Ahlborn limit at maximum power can be rigorously derived when the dimensionless figure-of-merit is very large for any asymmetric thermal contact resistances The results differ from cyclic thermodynamic engines, and some of the reasons are discussed We also point out the similarity and differences with single-level quantum dot heat engines, which assume no explicit thermal contact resistance with reservoirs

Enhanced Heat Transfer in Biporous Wicks in the Thin Liquid Film Evaporation and Boiling Regimes

Abstract: Biporous media consisting of microscale pin fins separated by microchannels are examined as candidate structures for the evaporator wick of a vapor chamber heat pipe. The structures are fabricated out of silicon using standard lithography and etching techniques. Pores which separate microscale pin fins are used to generate high capillary suction, while larger microchannels are used to reduce overall flow resistance. The heat transfer coefficient is found to depend on the area coverage of a liquid film with thickness on the order of a few microns near the meniscus of the triple phase contact line. We manipulate the area coverage and film thickness by varying the surface area-to-volume ratio through the use of microstructuring. Experiments are conducted for a heater area of 1 cm 2 with the wick in a vertical orientation. Results are presented for structures with approximately same porosities, fixed microchannel widths w � 30 lm and w � 60 lm, and pin fin diameters ranging from d ¼3‐29 lm. The competing effects of increase in surface area due to microstructuring and the suppression of evaporation due to reduction in pore scale are explored. In some samples, a transition from evaporative heat transfer to nucleate boiling is observed. While it is difficult to identify when the transition occurs, one can identify regimes where evaporation dominates over nucleate boiling and vice versa. Heat transfer coefficients of 20.7 (62.4) W/cm 2 -K are attained at heat fluxes of 119.6 (64.2) W/cm 2 until the wick dries out in the evaporation dominated regime. In the nucleate boiling dominated regime, heat fluxes of 277.0 (69.7) W/cm 2 can be dissipated by wicks with heaters of area 1 cm 2 , while heat fluxes up to 733.1 (6103.4) W/cm 2 can be dissipated by wicks with smaller heaters intended to simulate local hot-spots. [DOI: 10.1115/1.4006106]

Spacecraft Thermal Control

Abstract: The space mission Space environment Keplerian orbits Conductive heat transfer Thermal radiation heat transfer Thermal control surfaces Insulation systems Radiators Louvers Mechanical interfaces Heat pipes Phase change capacitors Heaters Pumped fluid loops Thermoelectric cooling Cryogenic systems Thermal protection systems Thermal control design Thermal mathematical models Thermal control testing Conclusion.

Isolated Quantum Heat Engine

Abstract: We present a theoretical and numerical analysis of a quantum system that is capable of functioning as a heat engine. This system could be realized experimentally using cold bosonic atoms confined to a double well potential that is created by splitting a harmonic trap with a focused laser. The system shows thermalization, and can model a reversible heat engine cycle. This is the first demonstration of the operation of a heat engine with a finite quantum heat bath.