Permeability and Thermal Conductivity of Compact Adsorbent of Salts for Sorption Refrigeration

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
L. Jiang ◽  
L. W. Wang ◽  
Z. Q. Jin ◽  
B. Tian ◽  
R. Z. Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transfer Performance ◽  
Natural Graphite ◽  
Heat Transfer Intensification

Properties, such as thermal conductivity and permeability, are important for the heat and mass transfer performance in sorption refrigeration. This Technical Brief investigates the thermal conductivity and permeability of eight types of chlorides, which are consolidated with expanded natural graphite (ENG) for the heat transfer intensification.

scholarly journals Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8191
Author(s):  
Shahbaz Ahmad ◽  
Zarghaam Haider Rizvi ◽  
Joan Chetam Christine Arp ◽  
Frank Wuttke ◽  
Vineet Tirth ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Weather Conditions ◽  
Nonlinear Dependence ◽  
Transfer Model ◽  
Power Cable ◽  
Cable Systems ◽  
Underground Power Cable

Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.

scholarly journals Characteristics of supercritical heat transfer during filmboiling of nanofluids on a vertical heated wall

2018 ◽  
pp. 29-35
Author(s):  
А. Avramenko ◽  
M. Kovetskaya ◽  
A. Tyrinov ◽  
Yu. Kovetska
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Heat Flux ◽  
High Temperature ◽  
Heat And Mass Transfer ◽  
Heated Surface ◽  
Heated Wall ◽  
Film Boiling

Nanofluid using for intensification of heat transfer during boiling are analyzed. The using boiling nanofluids for cooling high-temperature surfaces allows significantly intensify heat transfer process by increasing the heat transfer coefficient of a nanofluid in comparison with a pure liquid. The properties of nanoparticles, their concentration in the liquid, the underheating of the liquid to the saturation temperature have significant effect on the rate of heat transfer during boiling of the nanofluid. Increasing critical heat flux during boiling of nanofluids is associated with the formation of deposition layer of nanoparticles on heated surface, which contributes changing in the microcharacteristics of heat exchange surface. An increase in the critical heat flux during boiling of nanofluids is associated with the formation of a layer of deposition of nanoparticles on the surface, which contributes to a change in the microcharacteristics of the heat transfer of the surface. Mathematical model and results of calculation of film boiling characteristics of nanofluid on vertical heated wall are presented. It is shown that the greatest influence on the processes of heat and mass transfer during film boiling of the nanofluid is exerted by wall overheating, the ratio of temperature and Brownian diffusion and the concentration of nanoparticles in the liquid. The mathematical model does not take into account the effect changing structure of the heated surface on heat transfer processes but it allows to evaluate the effect of various thermophysical parameters on intensity of deposition of nanoparticles on heated wall. The obtained results allow to evaluate the effect of nanofluid physical properties on heat and mass transfer at cooling of high-temperature surfaces. The using nanofluids as cooling liquids for heat transfer equipment in the regime of supercritical heat transfer promotes an increase in heat transfer and accelerates the cooling process of high-temperature surfaces. Because of low thermal conductivity of vapor in comparison with the thermal conductivity of the liquid, an increase in the concentration of nanoparticles in the vapor contributes to greater growth in heat transfer in the case of supercritical heat transfer.

An Experimental Study on Heat and Mass Transfer in a Helical Absorber Using LiBr+LiI+LiNO3+LiCl Solution

2000 ◽  
Author(s):  
Jung-In Yoon ◽  
Choon-Geun Moon ◽  
Oh-Kyung Kwon ◽  
Eunpil Kim
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Experimental Study ◽  
Heat And Mass Transfer ◽  
Working Fluid ◽  
Transfer Performance ◽  
Falling Film ◽  
Absorption Chiller ◽  
Libr Solution ◽  
Cylindrical Form

Abstract An experimental study has been performed to investigate the heat and mass transfer performance in a falling film absorber of a domestic small-sized absorption chiller/heater. The components of the chiller/heater were concentrically arranged in a cylindrical form with low temperature generator, an absorber and an evaporator from the center. The arrangement of such a helical-type heat exchanger allows to make the system more compact as compared to a conventional one. As a working fluid, the LiBr+LiI+LiNO3+LiCl solution is used to get improved heat transfer. The heat and mass flux performance of the LiBr+LiI+LiNO3+LiCl solution shows 2 ∼ 5% increase than that of the LiBr solution. When a surfactant in the LiBr+LiI+LiNO3+LiCl solution is used, the performance of heat and mass transfer improves 15 ∼ 20%. This result shows the LiBr+LiI+LiNO3+LiCl solution with a surfactant can be applied to a small-sized absorption chiller/heater.

A Review on Working Pair Used in Adsorption Cooling System

2015 ◽  
Vol 23 (02) ◽  
pp. 1530001 ◽  
Author(s):  
Vinayak D. Ugale ◽  
Amol D. Pitale
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Cooling System ◽  
Physical Adsorption ◽  
Vital Role ◽  
Transfer Performance ◽  
Adsorption System ◽  
Adsorption Cooling System ◽  
Adsorber Bed

Adsorption cooling system find its application in refrigeration, air conditioning, chiller, Ice making, etc. It uses thermal energy as driving force. Adsorption systems are environmental friendly (zero global warming potential and ozone depleting potential) and also eliminates use of compressor and minimize vibration problem. So it can be used as substitute for conventional vapor compression refrigeration system or vapor absorption system. The adsorption generally classified in two types as physical adsorption (due to weak van der waal forces) and chemical adsorption (chemical reaction between adsorbent and adsorbate form new molecules). The working pair of adsorber and adsorbate play vital role in the performance of adsorption system. Activated carbon, zeolite, silica gel are commonly used adsorber and water, ammonia, methanol and ethanol can be used as adsorbate. The poor heat and mass transfer performance of adsorption is major challenge for researchers. The heat transfer performance of adsorption system can be increased by increasing heat transfer area of adsorber bed i.e., design of new adsorber bed, while mass transfer performance is improved by use of new adsorbent with higher sorption rate. Composite adsorber solve the problem of heat and mass transfer performance of chemical adsorbents and adsorption quantity of physical adsorbents by combination of chemical and physical adsorbent but it can add some limitation with it. In this paper, various adsorption pair, their selection, design of adsorber bed, methods to improve thermal performance of adsorber bed is reviewed with their properties, advantages and limitations.

scholarly journals The Effect of Flow-Induced Vibration on Heat and Mass Transfer Performance of Hollow Fiber Membranes in the Humidification/Dehumidification Process

Membranes ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 918
Author(s):  
Zhenxing Li ◽  
Bo Chen ◽  
Caihang Liang ◽  
Nanfeng Li ◽  
Yunyun Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Hollow Fiber ◽  
Hollow Fiber Membrane ◽  
Laser Vibrometer ◽  
Transfer Performance ◽  
Hollow Fiber Membranes ◽  
Fiber Membranes ◽  
Fiber Deformation

Cross-flow hollow fiber membranes are commonly applied in humidification/dehumidification. Hollow fiber membranes vibrate and deform under the impinging force of incoming air and the gravity of liquid in the inner tube. In this study, fiber deformation was caused by the pulsating flow of air. With varied pulsating amplitudes and frequencies, single-fiber deformation was investigated numerically using the fluid–structure interaction technique and verified with experimental data testing with a laser vibrometer. Then, the effect of pulsating amplitude and frequency on heat and mass transfer performance of the hollow fiber membrane was analyzed. The maximum fiber deformation along the airflow direction was far larger than that perpendicular to the flow direction. Compared with the case where the fiber did not vibrate, increasing the pulsation amplitude could strengthen Nu by 14–87%. Flow-induced fiber vibration could raise the heat transfer enhancement index from 13.8% to 80%. The pulsating frequency could also enhance the heat transfer of hollow fiber membranes due to the continuously weakened thermal boundary layer. With the increase in pulsating amplitude or frequency, the Sh number or Em under vibrating conditions can reach about twice its value under non-vibrating conditions.

The Effect of Vortex Core Distribution on Heat Transfer in Steam Cooling of Gas Turbine Blade Internal Ribbed Channels

2014 ◽  
Author(s):  
Jiangnan Zhu ◽  
Tieyu Gao ◽  
Jun Li ◽  
Guojun Li ◽  
Jianying Gong
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Flow Field ◽  
Gas Turbine ◽  
Heat And Mass Transfer ◽  
Turbine Blade ◽  
Vortex Core ◽  
Side Wall ◽  
High Strength ◽  
Transfer Performance

Steam has already been used as coolant of gas turbine blade internal cooling. A lot of investigations have been carried out to research the heat transfer performance of steam in ribbed rectangular channels. However, the micro-structure of the flow field especially the vortex distribution is not very clear. As the vortex caused by ribs is one of the main factors that enhance heat and mass transfer, it is very necessary to investigate the distribution of vortex in steam-cooled ribbed channels. The numerical simulation of steam flow field in 45° rib channels were carried out by using ANSYS CFX commercial program. The inlet Reynolds numbers are 30000 and 60000. The wall heat flux and inlet static pressure is 10kW/m2 and 0.3MPa, respectively. In order to find out the distribution and shape of all the main vortices, the technology of vortex core is applied, which is based on the critical point theory and Eigen-values of velocity gradient tensor. The distribution and shape of vortex core clearly indicates that the heat transfer strength of vortices positions is relatively higher than other places. There are four high strength vortices at the near-wall region between every two neighbored ribs. At the side wall which is located at the front side of ribs, high strength vortex exists and washes over the most part of the side wall. In the main flow region, the secondary flow caused by angled ribs can also be seen. The heat and mass transfer performance of steam in angled rib channels can be illustrated by the location and shape of vortex core.

scholarly journals Impact of Binary Chemical Reaction and Activation Energy on Heat and Mass Transfer of Marangoni Driven Boundary Layer Flow of a Non-Newtonian Nanofluid

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 702
Author(s):  
Ramanahalli Jayadevamurthy Punith Gowda ◽  
Rangaswamy Naveen Kumar ◽  
Anigere Marikempaiah Jyothi ◽  
Ballajja Chandrappa Prasannakumara ◽  
Ioannis E. Sarris
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Velocity Gradient ◽  
Boundary Layer Flow ◽  
Biological Fluids ◽  
Porosity Parameter ◽  
Layer Flow

The flow and heat transfer of non-Newtonian nanofluids has an extensive range of applications in oceanography, the cooling of metallic plates, melt-spinning, the movement of biological fluids, heat exchangers technology, coating and suspensions. In view of these applications, we studied the steady Marangoni driven boundary layer flow, heat and mass transfer characteristics of a nanofluid. A non-Newtonian second-grade liquid model is used to deliberate the effect of activation energy on the chemically reactive non-Newtonian nanofluid. By applying suitable similarity transformations, the system of governing equations is transformed into a set of ordinary differential equations. These reduced equations are tackled numerically using the Runge–Kutta–Fehlberg fourth-fifth order (RKF-45) method. The velocity, concentration, thermal fields and rate of heat transfer are explored for the embedded non-dimensional parameters graphically. Our results revealed that the escalating values of the Marangoni number improve the velocity gradient and reduce the heat transfer. As the values of the porosity parameter increase, the velocity gradient is reduced and the heat transfer is improved. Finally, the Nusselt number is found to decline as the porosity parameter increases.

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