Effect of a Drop in Working Fluid Pressure on Heat Transfer Performance During Phase Change in Heat Exchanger

2018 ◽  
Vol 42 (4) ◽  
pp. 251-258 ◽  
Author(s):  
Hyo In Lee ◽  
Ji Hwan Jeong
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Heat Transfer Performance ◽  
Fluid Pressure ◽  
Working Fluid ◽  
Transfer Performance

Investigation of the Effects of Simultaneous Internal Flow Boiling and External Condensation on the Heat Transfer Performance

2019 ◽  
Author(s):  
M. M. Kabir ◽  
Sangsoo Lee
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Single Phase ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Internal Flow ◽  
Transfer Performance ◽  
Test Rig ◽  
Phase Change Heat Transfer

Abstract Recent leaps in heat dissipation make it difficult for typical heat exchangers to meet the requirements of the advanced applications even with the maximally obtainable heat transfer performance associated with a single-phase process. Especially high heat flux applications such as thermal management in microelectronics, advanced material processing, and nuclear fusion reactors require extreme heat transfer methods to overcome the current limits. In this study, a heat exchanger adopting simultaneously two-opposite, phase-change heat transfer processes (internal flow boiling and external condensation) was proposed and analytically investigated. The phase-change heat transfer analyses were conducted for internal flow boiling and external condensation at a test section and the heat transfer performances were compared with that of a system with an internal single-phase, liquid flow process. It is found that the proposed heat exchanger configuration with an internal flow boiling can substantially enhance the heat transfer performances and provide better methods to manage the temperature difference comparing to those with an internal single-phase heat transfer due to its significant increase in a heat transfer coefficients and constant temperatures during phase-change processes. Additionally, this study also explains the design for a test rig to evaluate and validate the results in detail. The test rig consists of an internal flow boiling loop with a test section, an external condensation loop, sensors, auxiliary monitoring parts, and controlling and data acquisition systems. Thermodynamic cycle, pressure drop, and heat transfer analyses were conducted to determine the conditions and the specifications of components and sensors for the test rig.

The Start-Up Performance of Pulsating Heat Pipe With Communicating Pipe at Different Inclination Angles

2019 ◽  
Author(s):  
Fu-Min Shang ◽  
Shi-Long Fan ◽  
Jian-Hong Liu
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Heat Pipe ◽  
Heat Transfer Performance ◽  
Working Fluid ◽  
Transfer Performance ◽  
Pulsating Heat Pipe ◽  
High Heat Transfer ◽  
Start Up ◽  
Inclination Angles

Abstract The pulsating heat pipe (PHP) is a passive cooling device, which has the advantages of simple structure, high heat transfer performance and low production cost. The complex vapor-liquid phase change occurs in the in the initial stage of PHP. In this work, we explore the start-up performance of PHP at different inclination angles and the experiment shows that start-up performance is respectively different when the angles are 0°, 45°, 90°, 135° and 180°. Since the gravitational auxiliary function, the working fluid in the communicating pipe which takes longer time to vaporize change phase earlier than that in PHP’s loop when the angles are 0° and 45°. Nevertheless, when the angle is 90°, the phase change of working fluid in communicating pipe and in the loop occurs at the same time. Meanwhile, the oscillating mode affects the stability of the starting and heat transfer performance of the PHP.

scholarly journals Investigation of the Use of an Inorganic Aqueous Solution in Copper-Made Phase-Change Heat Transfer Devices

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Qi Yao ◽  
Jacob Supowit ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Aqueous Solution ◽  
Phase Change ◽  
Heat Transfer Performance ◽  
Capillary Rise ◽  
Copper Surface ◽  
Working Fluid ◽  
Transfer Performance ◽  
Phase Change Heat Transfer ◽  
Inorganic Aqueous Solution

A novel inorganic aqueous solution (IAS) is shown to have a better heat transfer performance than water when used as the working fluid in copper-made phase-change heat transfer devices. First, the physical properties of IAS are measured and compared to those of water. Another, a chemical analysis is performed, and the chemical reactions involved between IAS and the copper surface are listed and categorized by their contributions to the heat transfer performance. In addition, a capillary rise test is performed to show how each chemical contributes to the improvement of the surface wettability. Last, using IAS in copper-made phase-change heat transfer devices is discussed, and the main focus is how IAS improves the heat transfer performance by a smaller thermal resistance and a larger critical heat flux. The conclusion is validated by thermo-siphon tests at different inclination angles.

An Experimental Study of Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry in a Coil Heat Exchanger

2013 ◽  
Author(s):  
Minsuk Kong ◽  
Jorge L. Alvarado ◽  
Ehsan M. Languri
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Phase Change ◽  
Phase Change Material ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Coil Heat Exchanger ◽  
Change Material ◽  
Coil Heat

The use of microencapsulated phase change material (MPCM) slurry as an enhanced heat transfer fluid is considered to be very promising for saving energy in thermal energy systems. However, little is known how MPCM may exhibit enhanced heat transfer performance in coil heat exchanger. Coil heat exchangers are extensively used in industrial applications including heating, ventilating and air conditioning (HVAC) systems because of their superior heat transfer performance and compactness. In this study, the heat transfer characteristics of MPCM slurry in a coil heat exchanger have been investigated experimentally. Thermal properties of MPCM slurry were measured using a differential scanning calorimeter. Pressure drop, overall heat transfer coefficient and heat transfer effectiveness in a coil heat exchanger were determined by considering different flow rates. It was found that heat transfer characteristics were positively affected by the phase change process of the phase change material in MPCM, even though MPCM exhibit reduced turbulence and increased pressure drop. The overall heat transfer coefficient for MPCM slurry is in the range of 5,000 to 9,000 W/m2-K over a Dean number range from 1,600 to 4,000 (equivalent Reynolds number range of 6,000 to 15,000). The enhancement in heat transfer performance is about 17% when compared to that for water. In addition, durability tests of MPCM slurry were conducted to evaluate the MPCM’s ability to withstand continuous pumping conditions, which is critically important in the implementation of MPCM slurry in industrial applications.

EXPERIMENTAL STUDY ON THERMAL TRANSPORT PHENOMENON OF NANOFLUIDS AS WORKING FLUID IN HEAT EXCHANGER

2014 ◽  
Vol 22 (01) ◽  
pp. 1450005 ◽  
Author(s):  
SHUICHI TORII
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Horizontal Tube ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Transfer Performance ◽  
Nanoparticles Concentration ◽  
Transfer Behavior

This paper aims to study the convective heat transfer behavior of aqueous suspensions of nanoparticles flowing through a horizontal tube heated under constant heat flux condition. Consideration is given to the effects of particle concentration and Reynolds number on heat transfer enhancement and the possibility of nanofluids as the working fluid in various heat exchangers. It is found that (i) significant enhancement of heat transfer performance due to suspension of nanoparticles in the circular tube flow is observed in comparison with pure water as the working fluid, (ii) enhancement is intensified with an increase in the Reynolds number and the nanoparticles concentration, and (iii) substantial amplification of heat transfer performance is not attributed purely to the enhancement of thermal conductivity due to suspension of nanoparticles.

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