THERMAL STRESSES IN PARTIALLY ABSORBING FLAT PLATE DUE TO SUDDEN INTERRUPTION OF STEADY-STATE ASYMMETRIC RADIATION, I: CONVECTIVE COOLING AT REAR SURFACE

1983 ◽  
Vol 6 (1) ◽  
pp. 15-24 ◽  
Author(s):  
J.I. Frankel ◽  
J.P. Singh ◽  
J.R. Thomas ◽  
D.P.H. Hasselman
Keyword(s):  
Steady State ◽  
Flat Plate ◽  
Thermal Stresses ◽  
Rear Surface ◽  
Convective Cooling

Steady-State Thermal Stresses in Wedge-Shaped Cutting Tools

1975 ◽  
Vol 97 (3) ◽  
pp. 1060-1066
Author(s):  
P. F. Thomason
Keyword(s):  
Thermal Stress ◽  
Steady State ◽  
Metal Cutting ◽  
Thermal Stresses ◽  
Heat Conduction Problem ◽  
Equivalent Stress ◽  
Cutting Tools ◽  
Thermoelastic Stress ◽  
Plastic State ◽  
Steady State Heat

Closed form expressions for the steady-state thermal stresses in a π/2 wedge, subject to constant-temperature heat sources on the rake and flank contact segments, are obtained from a conformal mapping solution to the steady-state heat conduction problem. It is shown, following a theorem of Muskhelishvili, that the only nonzero thermal stress in the plane-strain wedge is that acting normal to the wedge plane. The thermal stress solutions are superimposed on a previously published isothermal cutting-load solution, to give the complete thermoelastic stress distribution at the wedge surfaces. The thermoelastic stresses are then used to determine the distribution of the equivalent stress, and this gives an indication of the regions on a cutting tool which are likely to be in the plastic state. The results are discussed in relation to the problems of flank wear and rakeface crater wear in metal cutting tools.

Transient Analysis of a Ceramic High Temperature Heat Exchanger and Chemical Decomposer

2007 ◽  
Author(s):  
Valery Ponyavin ◽  
Taha Mohamed ◽  
Mohamed Trabia ◽  
Yitung Chen ◽  
Anthony E. Hechanova
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Heat Exchanger ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Failure Criteria ◽  
Operating Conditions ◽  
Finite Element Software ◽  
Micro Channels ◽  
Temperature Heat

Ceramics are suitable for use in high temperature applications as well as corrosive environment. These characteristics were the reason behind selection silicone carbide for a high temperature heat exchanger and chemical decomposer, which is a part of the Sulphur-Iodine (SI) thermo-chemical cycle. The heat exchanger is expected to operate in the range of 950°C. The proposed design is manufactured using fused ceramic layers that allow creation of micro-channels with dimensions below one millimeter. A proper design of the heat exchanges requires considering possibilities of failure due to stresses under both steady state and transient conditions. Temperature gradients within the heat exchanger ceramic components induce thermal stresses that dominate other stresses. A three-dimensional computational model is developed to investigate the fluid flow, heat transfer and stresses in the decomposer. Temperature distribution in the solid is imported to finite element software and used with pressure loads for stress analysis. The stress results are used to calculate probability of failure based on Weibull failure criteria. Earlier analysis showed that stress results at steady state operating conditions are satisfactory. The focus of this paper is to consider stresses that are induced during transient scenarios. In particular, the cases of startup and shutdown of the heat exchanger are considered. The paper presents an evaluation of the stresses in these two cases.

Improved Model for Calculating Instantaneous Efficiency of Flat-Plate Solar Thermal Collector

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Oussama Ibrahim ◽  
Farouk Fardoun ◽  
Rafic Younes ◽  
Mohamad Ibrahim
Keyword(s):  
Steady State ◽  
Flat Plate ◽  
Case Studies ◽  
Solar Collector ◽  
Heating System ◽  
Solar Water Heating ◽  
Solar Water ◽  
Flat Plate Solar Collector ◽  
Definition Of ◽  
Solar Water Heating System

The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the system is off-operational provided that the instantaneous rate of heat stored in the heat transfer fluid (HTF) is less than or equal to zero. As a result, the improved efficiency-definition yields more realistic results in reflecting the performance of a flat-plate collector in an active solar water heating system and is recommended to be used.

Flow and Heat Transfer Analysis of Mist-Film Cooling on a Flat Plate

2017 ◽  
Author(s):  
Anjali Dwivedi ◽  
Ankit Verma ◽  
S. Sarkar
Keyword(s):  
Flat Plate ◽  
Latent Heat ◽  
Film Cooling ◽  
Thermal Stresses ◽  
Density Ratio ◽  
Heat Transfer Analysis ◽  
Main Stream ◽  
Two Phase ◽  
Maximum Enhancement ◽  
Cooling Effectiveness

Film cooling is one of the preferred methods for effective cooling of a gas turbine that forms a protective layer between hot flue gases and blade surface. This paper investigates the interaction of mist in the secondary flow and physics indicating the upper limit of mist concentration. Numerical simulations are performed on a flat plate having a series of discrete holes with 35 degree streamwise orientation and the holes are connected to a common delivery plenum chamber. The blowing ratio, density ratio and Reynolds number based on freestream and hole diameter (D) are 0.5, 1.2 and 15885 respectively. A two-phase mist consisting of finely dispersed water droplets of 10 micron in an airstream is introduced as the coolant from these holes. The latent heat absorbed by the evaporating droplets significantly reduces the sensible heat of the main stream, providing heat sinks that result in enhanced cooling effectiveness. The coupling between the two-phases is modelled through the interaction terms in the transport equations. Computations are performed by ANSYS Fluent 15.0 using k-ε realizable model. The results illustrate insight of complex transport phenomena associated with the mist of varying concentration from 2% to 7%. It has been observed that the maximum enhancement of cooling effectiveness reaches 43% at X/D = 10 for 2% mist by mass with an average enhancement of 26.5%. For 3% mist, the maximum enhancement becomes 80% at X/D = 16 with the average cooling enhancement of 43%. Mist concentrations 5% and beyond trend to increase average cooling because of more absorption of latent heat by droplets, but its trajectories shift towards wall, detrimental to the blade due to corrosion effect and thermal stresses.

Axisymmetric Thermal Stresses in a Spherical Shell of Arbitrary Thickness

1957 ◽  
Vol 24 (3) ◽  
pp. 376-380
Author(s):  
E. L. McDowell ◽  
E. Sternberg
Keyword(s):  
Steady State ◽  
Spherical Shell ◽  
Spherical Cavity ◽  
Series Solution ◽  
Thermal Stresses ◽  
Solid Sphere ◽  
Theory Of Elasticity ◽  
Infinite Medium ◽  
Series Solutions ◽  
Arbitrary Thickness

Abstract This paper contains an explicit series solution, exact within the classical theory of elasticity, for the steady-state thermal stresses and displacements induced in a spherical shell by an arbitrary axisymmetric distribution of surface temperatures. The corresponding solutions for a solid sphere and for a spherical cavity in an infinite medium are obtained as limiting cases. The convergence of the series solutions obtained is discussed. Numerical results are presented appropriate to a solid sphere if two hemispherical caps of its boundary are maintained at distinct uniform temperatures.

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