scholarly journals Transient Cooling Of A Cylinder In Cross Flow Bounded By An Adiabatic Wall

2018 ◽  
Vol 17 (2) ◽  
pp. 17
Author(s):  
Nawaf H Saeid ◽  
Bashir S. Abusahmin
Keyword(s):  
Thermal Properties ◽  
Cross Flow ◽  
Thermal Inertia ◽  
Cooling Process ◽  
Adiabatic Wall ◽  
Cold Air ◽  
Cooling Period ◽  
Air Stream ◽  
Storage Area ◽  
High Thermal Inertia

The present study investigates the parameters controlling the cooling process of acylindrical food in the storage area for a period of time. Transient analysis of theconduction and convection (conjugate) heat transfer from a cylindrical food, or acylindrical can filled with food is selected for numerical simulations. The cylinder isbounded by an adiabatic wall and the cold air is flowing normal to the cylinder axis (crossflow). The parameters investigated are: Reynolds number, food thermal properties(density, specific heat and thermal conductivity) and the cooling period. The range of theReynolds number is selected from 50 to 500 to be in laminar flow conditions. Threedifferent materials were selected according their thermal properties. The results arepresented to show the cooling process starting from blowing cold air stream on thecylinder for a period of 4 hours. The results show that the food with low thermal inertia iscooled faster than that of high thermal inertia. The present results show also that thecooling process can be shortened by increasing the air velocity and lower its temperature.

Effect of Pulsed Film Cooling on Leading Edge Film Effectiveness

2010 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Richard B. Rivir
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Thermal Inertia ◽  
Leading Edge ◽  
Continuous Film ◽  
Adiabatic Wall ◽  
Blowing Ratio ◽  
Velocity Waveform ◽  
Edge Surface ◽  
Cross Flow Velocity

Detailed film effectiveness measurements have been made on a cylindrical leading edge surface for steady and pulsating flow. The film hole is off-centered by 21.5° from the centerline and angled 20° to the surface and 90° from the stream wise direction. Two jet-to-cross-flow velocity ratios have been considered: VR = 1 and 2 which correspond to blowing ratio of 1 and 2, respectively. The pulsating frequency is 10 Hz and the duty cycle is 50%. Comparisons between film effectiveness with a pulsating film and a continuous film show that for the same blowing ratio, the effectiveness of the film drops by a factor of 2 when the flow is pulsed. Hotwire measurements are made to characterize the pulsating velocity waveform at the exit of the film exit and verify the integrity of the pulse. The variation in the measured surface adiabatic wall temperature over the pulsing duration is very small suggesting a large thermal inertia that keeps the wall surface largely unaffected by the time scale of the pulsations; this holds true for both blowing ratios tested.

scholarly journals Asteroid (101955) Bennu’s weak boulders and thermally anomalous equator

2020 ◽  
Vol 6 (41) ◽  
pp. eabc3699 ◽  
Author(s):  
B. Rozitis ◽  
A. J. Ryan ◽  
J. P. Emery ◽  
P. R. Christensen ◽  
V. E. Hamilton ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Thermal Properties ◽  
Mass Movement ◽  
Thermal Inertia ◽  
Temperature Dependent ◽  
Atmospheric Entry ◽  
Earth Asteroid ◽  
C Complex ◽  
High Thermal Inertia ◽  
Tentative Correlation

Thermal inertia and surface roughness are proxies for the physical characteristics of planetary surfaces. Global maps of these two properties distinguish the boulder population on near-Earth asteroid (NEA) (101955) Bennu into two types that differ in strength, and both have lower thermal inertia than expected for boulders and meteorites. Neither has strongly temperature-dependent thermal properties. The weaker boulder type probably would not survive atmospheric entry and thus may not be represented in the meteorite collection. The maps also show a high–thermal inertia band at Bennu’s equator, which might be explained by processes such as compaction or strength sorting during mass movement, but these explanations are not wholly consistent with other data. Our findings imply that other C-complex NEAs likely have boulders similar to those on Bennu rather than finer-particulate regoliths. A tentative correlation between albedo and thermal inertia of C-complex NEAs may be due to relative abundances of boulder types.

scholarly journals Transient cooling of two circular cylinders arranged in Tandem an bounded by an adiabatic wall

2021 ◽  
Vol 15 (4) ◽  
pp. 8580-8591
Author(s):  
Nawaf Hazim Saeid ◽  
N. Hasan ◽  
Seri Rahayu Ya'akob ◽  
S. Shuib
Keyword(s):  
Reynolds Number ◽  
Heat Dissipation ◽  
Cross Flow ◽  
Thermal Inertia ◽  
Separation Distance ◽  
Carbon Steels ◽  
Cooling Time ◽  
Circular Cylinders ◽  
Adiabatic Wall ◽  
The Difference

Parametric study is carried out on the transient cooling process of two circular cylinders in tandem arrangement for a specified period of time. Transient analysis of conjugate (conduction and convection) heat dissipation from two identical cylinders is considered with various parameters. The two cylinders of same size and properties are bounded by an adiabatic flat wall from below and the cooling air is flowing normal to their axis (cross flow). The following parameters are investigated in the present study: Reynolds number, cylinders thermal properties, separation distance between the two cylinders and the cooling time. The laminar flow is considered with Reynolds number values from 50 to 500. The simulations are carried out for cooling the two cylinders made of carbon steels, plastics plexiglass and plywood. The local and average Nusselt number for both steady and transient cooling of the two cylinders are presented. The effects of the parameters are investigated and the results are presented to understand the process. It is found that increasing either the separation distance and/or the Reynolds number will increase the heat dissipation and reduce the cooling time. The results show that carbon steels cylinders need longer time of cooling compare with the plywood cylinders due to the difference in their thermal inertia.

Effect of Pulsed Film Cooling on Leading Edge Film Effectiveness

2011 ◽  
Vol 134 (4) ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Richard B. Rivir
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Thermal Inertia ◽  
Leading Edge ◽  
Continuous Film ◽  
Adiabatic Wall ◽  
Blowing Ratio ◽  
Velocity Waveform ◽  
Edge Surface ◽  
Cross Flow Velocity

Detailed film effectiveness measurements have been made on a cylindrical leading edge surface for steady and pulsating flows. The film hole is off centered by 21.5 deg from the centerline and angled 20 deg to the surface and 90 deg from the streamwise direction. Two jet-to-cross-flow velocity ratios have been considered: VR=1 and 2, which correspond to blowing ratios of 1 and 2, respectively. The pulsating frequency is 10 Hz and the duty cycle is 50%. Comparisons between film effectiveness with a pulsating film and a continuous film show that for the same blowing ratio, the effectiveness of the film drops by a factor of 2 when the flow is pulsed. Hotwire measurements are made to characterize the pulsating velocity waveform at the exit of the film exit and verify the integrity of the pulse. The variation in the measured surface adiabatic wall temperature over the pulsing duration is very small, suggesting a large thermal inertia that keeps the wall surface largely unaffected by the time scale of the pulsations; this holds true for both blowing ratios tested.

scholarly journals Thermal behavior of light earth used for building insulation: Insight on PCM introduction impact

2021 ◽  
Vol 2069 (1) ◽  
pp. 012120
Author(s):  
Farjallah Alassaad ◽  
Karim Touati ◽  
Daniel Levacher ◽  
Nassim Sebaibi
Keyword(s):  
Thermal Properties ◽  
Building Materials ◽  
Phase Change Materials ◽  
Natural Fiber ◽  
Research Work ◽  
Thermal Inertia ◽  
Thermal Response ◽  
Thermal Insulating ◽  
High Thermal Inertia ◽  
The Impact

Abstract To reduce building significant contribution to greenhouse gas emissions, architects and engineers are seeking eco-friendly construction solutions. Among investigated options, building’s thermal insulation and heat storage can be cited. In this regard, earth-based materials are attracting particular interest. These last years, there is a renewed interest in these eco-friendly building materials and techniques. This is due to many advantages that they present: excellent humidity regulation ability and high thermal inertia. Present study aims to improve light earth thermal properties. Specifically, this research work focuses on the development of an insulating and heat storing material. To achieve this, phase change materials (PCM) are incorporated in soil-natural fiber mixtures. In fact, different light earth samples are first prepared. Then, thermally characterized to highlight the impact of PCM on the light earth thermal insulating, heat storing properties and thermal response to changing boundary conditions. The incorporation of PCM showed an interesting improvement of the light earth thermal properties namely on thermal conductivity, specific heat capacity, and thermal comfort time.

scholarly journals Thermal modes of space objects with high thermal inertia

2017 ◽  
pp. 267-274
Author(s):  
M.M. Penkov ◽  
A.M. Dzitoev ◽  
E.V. Lapovok ◽  
S.I. Khankov
Keyword(s):  
Thermal Inertia ◽  
Space Objects ◽  
High Thermal Inertia

Effects of Double Wall Cooling Configuration and Conditions on Performance of Full-Coverage Effusion Cooling

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Nathan Rogers ◽  
Zhong Ren ◽  
Warren Buzzard ◽  
Brian Sweeney ◽  
Nathan Tinker ◽  
...  
Keyword(s):  
Film Cooling ◽  
Cross Flow ◽  
Hole Array ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Full Coverage ◽  
Cooling Hole ◽  
Double Wall

Experimental results are presented for a double wall cooling arrangement which simulates a portion of a combustor liner of a gas turbine engine. The results are collected using a new experimental facility designed to test full-coverage film cooling and impingement cooling effectiveness using either cross flow, impingement, or a combination of both to supply the film cooling flow. The present experiment primarily deals with cross flow supplied full-coverage film cooling for a sparse film cooling hole array that has not been previously tested. Data are provided for turbulent film cooling, contraction ratio of 1, blowing ratios ranging from 2.7 to 7.5, coolant Reynolds numbers based on film cooling hole diameter of about 5000–20,000, and mainstream temperature step during transient tests of 14 °C. The film cooling hole array consists of a film cooling hole diameter of 6.4 mm with nondimensional streamwise (X/de) and spanwise (Y/de) film cooling hole spacing of 15 and 4, respectively. The film cooling holes are streamwise inclined at an angle of 25 deg with respect to the test plate surface and have adjacent streamwise rows staggered with respect to each other. Data illustrating the effects of blowing ratio on adiabatic film cooling effectiveness and heat transfer coefficient are presented. For the arrangement and conditions considered, heat transfer coefficients generally increase with streamwise development and increase with increasing blowing ratio. The adiabatic film cooling effectiveness is determined from measurements of adiabatic wall temperature, coolant stagnation temperature, and mainstream recovery temperature. The adiabatic wall temperature and the adiabatic film cooling effectiveness generally decrease and increase, respectively, with streamwise position, and generally decrease and increase, respectively, as blowing ratio becomes larger.

Effect of cold air stream injection on cyclone performance at high temperature

2017 ◽  
Vol 183 ◽  
pp. 293-303 ◽  
Author(s):  
An-Ni Huang ◽  
Norio Maeda ◽  
Satoshi Sunada ◽  
Tomonori Fukasawa ◽  
Hideto Yoshida ◽  
...  
Keyword(s):  
High Temperature ◽  
Cold Air ◽  
Air Stream

New Reactor Safety Measures for the European Sodium Fast Reactor - Part I: Conceptual Design

2021 ◽  
Author(s):  
Joel Guidez ◽  
Janos Bodi ◽  
Konstantin Mikityuk ◽  
Enrico Girardi ◽  
Bernard Carluec
Keyword(s):  
Fast Reactor ◽  
Heat Removal ◽  
Thermal Inertia ◽  
Lessons Learned ◽  
Reactor Safety ◽  
Fukushima Accident ◽  
Safety Level ◽  
Safety Measures ◽  
Sodium Fast Reactor ◽  
High Thermal Inertia

Abstract Following up the previous CP-ESFR project, the ESFR-SMART project considers the safety objectives envisaged for Generation-IV reactors, taking into account the lessons learned from the Fukushima accident, in order to increase the safety level of the European Sodium Fast Reactor (ESFR). In accordance with these objectives, guidelines have been defined to drive the ESFR-SMART developments, mainly simplifying the design and using all the positive features of Sodium Fast Reactors (SFR), such as low coolant pressure, efficiency of natural convection, possibility of decay heat removal (DHR) by atmospheric air, high thermal inertia and long grace period before a human intervention is needed. In this paper, a set of new ambitious safety measures is introduced for further evaluation within the project. The proposed set aims at consistency with the main lines of safety evolutions since the Fukushima accident, but it does not yet constitute the final comprehensive safety analysis. The paper gives a first review of the new propositions to enhance the ESFR safety, leading to a simplified reactor, forgiving and including a lot of passivity. This first version is supported by the various project tasks in order to assess the relevance of the whole design in comparison to the final safety objectives.

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