Begell House Inc.
Heat Transfer Research
HTR
1064-2285
43
4
2012
VORTEX GENERATION IN FLOWS PAST DIFFERENTIALLY DIMPLED SURFACES
285-295
Igor A.
Popov
Tupolev Kazan National Research Technical University – Kazan Aviation
Institute, 10 K. Marx Str., Kazan, Tatarstan, 420015, Russia
A. V.
Shchelchkov
A. N. Tupolev Kazan National Research Technical University, 10 K. Marx Str., Kazan, 420111, Russian Federation
D. V.
Ryzhkov
A. N. Tupolev Kazan State Technical University, Kazan, 420111, Russia
R. A.
Ul'yanova
A. N. Tupolev Kazan State Technical University, Kazan, 420111, Russia
The results of visualization of vortical water and air flows past surfaces with various dimples (trench-like, semispherical, and cylindrical) for heat transfer intensification in laminar, transient, and turbulent regimes are presented. Flows past single dimples and their systems were investigated. Various methods of visualization were used such as smoke, the carbon oil, and coloring admixtures. Flow pictures and flow pattern diagrams on the surfaces with various dimples are given. Comparative results of infra-red investigations of convective heat transfer on surfaces with such intensifiers are presented. The mechanisms underlying heat transfer intensification on such surfaces are defined. Optimum design parameters of such heat transfer intensifiers are recommended.
COMPARATIVE MODELING OF LEVEL MODELS OF CHEMICAL REACTIONS
297-310
S. A.
Losev
Instutute of Mechanics, M. V. Lomonosov Moscow State University,Moscow, Russia
A. L.
Sergievskaya
Institute of Mechanics, M. V. Lomonosov Moscow State University, Moscow, Russia
Properties of the models of physical-chemical processes of dissociation and exchange reactions involving vibrationally excited molecules in the level description are an object of the investigation. The work is aimed at study and classification of the known and new models according to the principle of their information software and the complexity of their implementation with subsequent recommendations for practical use in applied problems. The main methodology of performing this work is the use of the principles of information and mathematical simulation. The result of the work done is a structured description of eight models of dissociation and exchange processes in the level description. In the process of testing the models and of conducting computational experiments some a priori unknown properties of the models and relationships between objective functions of different models are obtained. This has allowed one to substantially simplify the conditions for use of these models.
SOURCES OF ENERGY ABSORPTION OF SPARK DISCHARGE IN DIRECT DETONATION INITIATION
311-326
K. V.
Korytchenko
Military Training Department of the National Technical University "Kharkov Polytechnic Institute", Kharkov, Ukraine
The work presents the estimate of the distribution of the spark discharge energy throughout different sources of its absorption for the problem of direct detonation initiation. The estimate is obtained by mathematical simulations of both transient process in the RLC-circuit at nonlinear load and gas dynamic expansion of a spark channel in the reactive mixture. The results of oscilloscope recording and photography of the spark channel served as initial data for mathematical simulation. Discharge energy loss due ohmic heating, loss in near-electrode regions, loss due to dissociation and ionization, as well as loss due to uncontrolled energy supply were taken into account.
ANALYSIS OF ENTROPY GENERATION, PUMPING POWER, AND TUBE WALL TEMPERATURE IN AQUEOUS SUSPENSIONS OF ALUMINA PARTICLES
327-342
Mohammad
Karami
Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, Iran
Ebrahim
Shirani
Foolad Institute of Technology, Fooladshahr, Isfahan, 8491663763, Iran
Abdollah
Avara
Department of Mechanical Engineering, Persian Gulf University of Bushehr, Bushehr, Iran
In the present paper, the practical efficiency of using aluminaminus;water nanofluid was evaluated numerically by the method of entropy generation; pumping power and tube wall temperature were analyzed. Laminar forced convection by water-based nanofluid flow through a uniformly heated circular tube is considered. A single-phase fluid approach is adopted to investigate the behavior of nanofluid and numerical results are compared with the experimental data. Good agreement is achieved in the developed region.
The aim of the present study is to investigate the influence of volume fraction, duct length, Reynolds number, and tube diameter on pumping power, entropy generation, and tube wall temperature to evaluate the nanofluid overall efficiency. The results indicated that increasing volume fraction of nanofluid for heat performance increases the pumping power exponentially and decreases the entropy generation and tube wall temperature linearly, so this suggests that using nanofluid with high volume fraction is not reasonable due to the cost of pumping power. Since it was observed that entropy generation and pumping power increase and tube wall temperature decreases relative to the duct length, this suggests that increasing tube length will reduce the overall efficiency of nanofluids. However, to avoid high wall temperature, duct length cannot be too short. Also, the results showed that increasing tube diameter will decrease entropy generation and pumping power and tube wall temperature remains constant, so it can be concluded that increasing pipe diameter will enhance the overall efficiency of nanofluids. Since the product of the diameter and length is constant, the tube diameter has the maximum value at the point which shows the maximum wall temperature; also, the duct length is minimum at this point, too. Therefore, it can be concluded that the overall efficiency of nanofluid is maximum at this point.
NUMERICAL INVESTIGATION OF GROUND-COUPLED VERTICAL BOREHOLE HEAT EXCHANGERS WITH GROUNDWATER ADVECTION
343-362
Marzio
Piller
Department of Engineering and Architecture, University of Trieste, via A. Valerio 10, 34127
Trieste (TS), Italy
Alberto Liuzzo
Scorpo
Dipartimento di Ingegneria Civile e Architettura, Universita degli Studi di Trieste, 34127 Trieste (ITALY)
Groundwater advection is commonly neglected in the design of ground-coupled vertical borehole heat exchangers. In this work, the efficiency of heat transfer from a vertical borehole with groundwater advection is investigated by numerical simulations. The actual borehole geometry is accounted for, resulting in a perturbed flow field. The present results are compared with the analytical solution for the transient, two-dimensional heat convection around a line heat source derived by Diao et al. (2004). A wide range of viable Peclet numbers is considered.
EFFECTS OF CHEMICAL REACTION DOUBLE DISPERSION ON HEAT AND MASS TRANSFER IN NON-DARCY, NON-NEWTONIAN FLUID OVER A VERTICAL SURFACE
363-382
P. K.
Kameswaran
Department of Engineering Mathematics, GITAM University, Hyderabad Campus, Rudraram, Hyderabad, Andhra Pradesh, India
A. S. N.
Murti
Department of Engineering Mathematics, GITAM University, GIT, Gandhi Nagar, Rushikonda, Visakhapatnam-530 045, Andhra Pradesh, India
T. Poorna
Kantha
Department of Engineering Mathematics, GITAM University, GIT, Gandhi Nagar, Rushikonda, Visakhapatnam-530 045, Andhra Pradesh, India
D. R. V. S. R. K.
Sastry
Department of Mathematics, Aditya Engineering College, Aditya Nagar, ADB Road, Surampalem, Pin:533437, East-Godavari District, Andhra Pradesh, India
This paper presents a numerical investigation of double-diffusive free convective heat and mass transfer of a chemically reacting fluid flowing through a non-Darcian porous medium adjacent to a vertical surface. The Forchheimer extension is considered in the flow equation, chemical reaction is considered in the concentration equation. The governing equations are solved numerically by means of the fourth-order Rungeminus;Kutta method coupled with the double-shooting technique. The effects of thermal dispersion, solute dispersion, velocity, temperature, and concentration profiles as well as heat and mass transfer rates are discussed.