scholarly journals Synthesizing heat transfer factors on thermal bonding structure of mineral added polypropylene spun‐bond

2022 ◽  
pp. 52138
Author(s):  
Wei Wei ◽  
Eunkyoung Shim ◽  
Yu Song ◽  
Behnam Pourdeyhimi
Keyword(s):  
Heat Transfer ◽  
Thermal Bonding ◽  
Transfer Factors ◽  
Bonding Structure

Analysis of Heat Transfer Factors for a Heat Pipe Absorber Array Connected to a Common Manifold

1986 ◽  
Vol 108 (1) ◽  
pp. 11-16 ◽  
Author(s):  
J. R. Hull
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Efficiency ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Maximum Efficiency ◽  
Pipe Surface ◽  
Transfer Factors ◽  
Collector Efficiency ◽  
Flow Through

Heat transfer factors and thermal efficiency are calculated for a heat pipe absorber array connected to a common manifold. Arrays with less than ten heat pipes are shown to have significantly less efficiency than a conventional flow-through collector. Efficiency is also sensitive to the heat transfer rate per unit temperature difference from the heat pipe fluid to the manifold fluid divided by that from the heat pipe surface to the ambient, with maximum efficiency occurring for ratios greater than 100.

scholarly journals Solar Salt Latent Heat Thermal Storage for a Small Solar Organic Rankine Cycle Plant

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Sol-Carolina Costa ◽  
Khamid Mahkamov ◽  
Murat Kenisarin ◽  
Mohammad Ismail ◽  
Kevin Lynn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Latent Heat ◽  
Storage System ◽  
Organic Rankine Cycle ◽  
Heat Pipes ◽  
Rankine Cycle ◽  
Thermal Storage ◽  
Thermal Bonding ◽  
Solar Salt ◽  
Computational Fluid Dynamics Analysis

Abstract The design of the latent heat thermal storage system (LHTESS) was developed with a thermal capacity of about 100 kW h as a part of small solar plant based on the organic Rankine cycle (ORC). The phase change material (PCM) used is solar salt with the melting/solidification temperature of about 220 °C. Thermophysical properties of the PCM were measured, including its phase transition temperature, heat of fusion, specific heat, and thermal conductivity. The design of the thermal storage was finalized by means of the 3D computational fluid dynamics analysis. The thermal storage system is modular, and the thermal energy is delivered with the use of thermal oil, heated by Fresnel mirrors. The heat is transferred into and from the PCM in the casing using bidirectional heat pipes, filled with water. A set of metallic screens are installed in the box with the pitch of 8–10 mm to enhance the heat transfer from heat pipes to the PCM and vice-versa during the charging and discharging processes, which take about 4 h. This work presents a numerical study on the use of metallic fins without thermal bonding as a heat transfer enhancement method for the solar salt LHTESS. The results show that the absence of the thermal bonding between fins and heat pipes (there was a gap of 0.5 mm between them) did not result in a significant reduction of charging or discharging periods. As expected, aluminum fins provide better performance in comparison with steel ones due to the difference in the material conductivity. The main advantage observed for the case of using aluminum fins was the lower temperature gradient across the LHTESS.

Modified Zonal Method for Thin Solid Semi-Transparent Media With Reflective Boundary

2007 ◽  
Author(s):  
Georges M. El-Hitti ◽  
Maroun Nemer ◽  
Khalil El Khoury ◽  
Denis Coldic
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Transient Operation ◽  
Scattering Media ◽  
Zonal Method ◽  
Total Heat Transfer ◽  
Transfer Factors ◽  
Transparent Media ◽  
The Matrix ◽  
Time Required

In this paper a detailed description of a modified zonal method used for the prediction of transient operation in glass treatment furnaces is presented. This method calculates the radiative transfer factors for scenes containing both diffusive surfaces and absorbing-emitting/non-scattering media with high indices of refraction all embedded in a totally transparent atmosphere. The method used combines the flux plans approximation for calculation of the view factors, the plating algorithm originally developed by Edwards for calculation of the total heat transfer factors, and finally, Emery’s equations for deduction of the surface-volume and volume-volume heat transfer factors. The matrix of radiative transfer is then simplified by eliminating the low energy level factors, thus rendering the matrix hollow and thereafter decreasing the time required for calculation.

Developing Consistent Inlet Thermal Boundary Condition in Micro/Nano Scale Channels With Heat Transfer

2008 ◽  
Author(s):  
Masoud Darbandi ◽  
Shidvash Vakilipour
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Boundary Conditions ◽  
Incompressible Flows ◽  
Thermal Boundary Condition ◽  
Constant Wall Temperature ◽  
Transfer Factors ◽  
The Real ◽  
Nano Scale ◽  
Inlet Boundary Condition

In this work, we present a more realistic inlet boundary condition to simulate compressible and incompressible flows through micro and nano channels considering consistent momentum and heat transfer specifications there. At solid walls, a constant wall temperature with suitable jump is applied as the wall thermal boundary condition; however, two types of thermal inlet boundary conditions are investigated at the inlet. We firstly examine the classical inlet boundary condition, which specifies a uniform temperature distribution right at the real inlet. Alternatively, we apply the same boundary condition but at a fictitious place far upstream of the real channel inlet. To validate our results, the results obtained after employing the former boundary conditions are evaluated against other available numerical results and Lattice Boltzmann solutions. In this validation, the friction factor and Nusselt number are treated as the most important hydrodynamics and heat transfer factors to be appraised. Next, we present the results after applying the second type of inlet boundary conditions and compare them with those of applying the first type of boundary condition. This study suggests an innovation in micro/nano scale heat transfer treatment close to the channel inlets.

scholarly journals NUMERICAL STUDY OF FLUID FLOW AND HEAT TRANSFER IN TUBE BANKS WITH STREAM-WISE PERIODIC BOUNDARY CONDITIONS

1998 ◽  
Vol 22 (4A) ◽  
pp. 397-416 ◽  
Author(s):  
S.B. Beale ◽  
D.B. Spalding
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Boundary Conditions ◽  
Bulk Temperature ◽  
Local Pressure ◽  
Transfer Factors ◽  
Flow And Heat Transfer ◽  
Tube Banks

A numerical procedure for the calculation of laminar fully-developed cross-flow and heat transfer in tube-banks heat exchangers is presented. Boundary conditions are introduced in a form similar to the treatment at conventional inlets and outlets. Calculations are performed for in-line square, rotated square and equilateral triangle geometries, with pitch-to-diameter ratio 1.25-2, Reynolds number 101-103 and Pradtl number 1-100, under both constant heat flux and constant wall temperature boundary conditions. Overall pressure drop and heat transfer factors are compared to previous numerical work, empirical correlations and experimental data. Overall pressure drop calculations correlate with experimental data, while at low Reynolds number, heat transfer calculations are shown to depend upon the choice of reference bulk temperature in the rate equation. Graphs of local pressure, drag, and heat transfer coefficients are provided and discussed in detail.

Numerical and Experimental Study on the Heat Transfer and Pressure Drop of Compact Cross-Corrugated Recuperators

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Zhou Guo-Yan ◽  
Tu Shan-Tung ◽  
Ma Hu-Gen
Keyword(s):  
Heat Transfer ◽  
Control Volume ◽  
Influence Factors ◽  
Sine Wave ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Clear Fluid ◽  
Transfer Factors ◽  
Periodic Cell ◽  
Dynamics Simulations

Recuperator is one of the key components in high temperature gas cooled reactors. Although cross-corrugated plates have been used to increase the thermal performance of the recuperators, the fundamental mechanisms of fluid flow and heat transfer are generally not clear. Fluid dynamics simulations and experiments are hence carried out to study the performance of the recuperators. A periodic cell is employed as the control volume. The flow field and heat transfer in sine-wave crossed-corrugated channels are investigated based on the Navier–Stokes and energy equations in the laminar flow regime between Re = 84 and 1168. The numerical results of the heat transfer factors and friction factors in different operating conditions show a fairly good agreement with the experimental measurements. The influence factors on the heat transfer and the hydraulic performance are also discussed in the paper. It is found that the heat transfer factor j and friction factor f decrease with the increase of the pitch-height ratio for a given Reynolds number.

Preparation and characterization of thin films of carbon nitride

1995 ◽  
Vol 53 ◽  
pp. 104-105
Author(s):  
L. Wan ◽  
R. F. Egerton
Keyword(s):  
Carbon Nitride ◽  
Arc Discharge ◽  
Ion Beam ◽  
Chemical Vapor ◽  
Reactive Sputtering ◽  
Vacuum Arc ◽  
Specimen Preparation ◽  
Bonding Structure ◽  
Electron Energy Loss

INTRODUCTION Recently, a new compound carbon nitride (CNx) has captured the attention of materials scientists, resulting from the prediction of a metastable crystal structure β-C3N4. Calculations showed that the mechanical properties of β-C3N4 are close to those of diamond. Various methods, including high pressure synthesis, ion beam deposition, chemical vapor deposition, plasma enhanced evaporation, and reactive sputtering, have been used in an attempt to make this compound. In this paper, we present the results of electron energy loss spectroscopy (EELS) analysis of composition and bonding structure of CNX films deposited by two different methods.SPECIMEN PREPARATION Specimens were prepared by arc-discharge evaporation and reactive sputtering. The apparatus for evaporation is similar to the traditional setup of vacuum arc-discharge evaporation, but working in a 0.05 torr ambient of nitrogen or ammonia. A bias was applied between the carbon source and the substrate in order to generate more ions and electrons and change their energy. During deposition, this bias causes a secondary discharge between the source and the substrate.

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