This document provides information on different modes of heat transfer including conduction, convection and radiation. It defines conduction as the transfer of heat through direct contact of particles over large distances. Convection is defined as the transfer of heat from one place to another inside a system through fluid motion, requiring a material medium. Radiation is defined as the transfer of heat in the form of electromagnetic waves with no need for a material medium. The document also discusses various concepts related to these modes of heat transfer such as Fourier's law of conduction, heat transfer coefficients, Nusselt number, Prandtl number and Reynolds number.
Understand the physical mechanism of convection and its classification.
Visualize the development of velocity and thermal boundary layers during flow over surfaces.
Gain a working knowledge of the dimensionless Reynolds, Prandtl, and Nusselt numbers.
Distinguish between laminar and turbulent flows, and gain an understanding of the mechanisms of momentum and heat transfer in turbulent flow.
Derive the differential equations that govern convection on the basis of mass, momentum, and energy balances, and solve these equations for some simple cases such as laminar flow over a flat plate.
Non dimensionalize the convection equations and obtain the functional forms of friction and heat transfer coefficients.
Use analogies between momentum and heat transfer, and determine heat transfer coefficient from knowledge of friction coefficient.
Introduction to convection
The dimensionless number and its physical significance
Similarity parameters from the differential equation
Dimensional analysis approach and its application
Numerical on Dimensional analysis approach
Review of Navier-Stokes equation
Understand the physical mechanism of convection and its classification.
Visualize the development of velocity and thermal boundary layers during flow over surfaces.
Gain a working knowledge of the dimensionless Reynolds, Prandtl, and Nusselt numbers.
Distinguish between laminar and turbulent flows, and gain an understanding of the mechanisms of momentum and heat transfer in turbulent flow.
Derive the differential equations that govern convection on the basis of mass, momentum, and energy balances, and solve these equations for some simple cases such as laminar flow over a flat plate.
Non dimensionalize the convection equations and obtain the functional forms of friction and heat transfer coefficients.
Use analogies between momentum and heat transfer, and determine heat transfer coefficient from knowledge of friction coefficient.
Introduction to convection
The dimensionless number and its physical significance
Similarity parameters from the differential equation
Dimensional analysis approach and its application
Numerical on Dimensional analysis approach
Review of Navier-Stokes equation
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
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Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
6. DEFINITION
The process, in which heat energy is
transferred from one system to
another system due to movement of
particles through large distances, is
called convection.
7. EXPLANATION
In fluids (liquids or gases) heat
transfer from one place to
another inside a system takes
place through convection. This
mode of transfer of heat
requires a material medium.
The molecules take heat the
heat energy and their kinetic
energy increases and they
carry heat through large
distances.
8. •VENTILATORS: Ventilators are provided in the walls
of a room near the ceiling, which help to keep the room
temperature moderate by continuous circulation of air.
The air inside the room gets impure and heated due to
our breathing. This hot air rises up and passes out
through ventilators, thus allowing space for currents of
fresh air from outside windows or doors.
9. As air warmed at the Equator rises towards the poles,
the rotation of the Earth causes it to deflect and flow
back towards the Equator. In the northern hemisphere,
the winds blow from the east to the west, while they
blow in the opposite direction in the southern
hemisphere. These winds tend to be much stronger
over open water than they are across land, which has
made them ideal for sailors.
10. LAND BREEZES AND SEA BREEZES:
Land is better conductor of heat than water. hence in day time,
the land gets hotter than in the sea. The air above the land
becomes warm and rises up being lighter and some what cold
air above sea surface moves towards the sea shore. This is
known as sea breeze.
During night land becomes cooler than water and so warm air over the
water in sea rises up. The air on the land near the sea shore begins to
move towards sea side and is called land breeze
11. RADIATION
DEFINITION
“The process in which heat energy travels from one
system to another in the form of electromagnetic
waves with no need of material medium is called
Radiation.”
EXPLAINATION: In radiation heat travels from
one system to another in the form of
electromagnetic radiations (photons). Thus no
medium is required for this mode of transfer of
heat.
13. • A rate equation that allows determination of the conduction heat flux
from knowledge of the temperature distribution in a medium
Fourier’s Law
• Its most general (vector) form for multidimensional conduction is:
q k T
Implications:
– Heat transfer is in the direction of decreasing temperature
(basis for minus sign).
– Direction of heat transfer is perpendicular to lines of constant
temperature (isotherms).
– Heat flux vector may be resolved into orthogonal components.
– Fourier’s Law serves to define the thermal conductivity of the
medium /k q T
16. Thermodynamic
x
Q/t Q/t
T1 T2
= T1-T2
For a uniform rod the rate of flow of heat through a
conductor ( Q/ t) is proportional to
•the cross sectional area (A) of the conductor
•the temperature gradient ( q/ x)
The constant of proportionality, k, is the thermal conductivity BUT note that heat
flows down a temperature gradient so we also introduce a negative sign to account
for this and obtain:
Q
T
kA
x
Thermal conductivity
17. Thermodynamics
k depends on the material and is called the thermal conductivity.
Rearranging in terms of k we can evaluate the units of k:
k
Q
t A
x
Wm-2
K-1
m Wm-1
K-1
So k is defined as the rate of flow of
heat through unit area of cross
section of 1m of material when the
temperature difference between the
surfaces is 1K.
Thermal conductivity
18. The composite Wall
• The concept of a thermal
resistance circuit allows ready
analysis of problems such as a
composite slab (composite
planar heat transfer surface).
• In the composite slab, the heat
flux is constant with x.
• The resistances are in series and
sum to Rth = Rth1 + Rth2.
• If TL is the temperature at the
left, and TR is the temperature at
the right, the heat transfer rate
is given by
21 thth
RL
th RR
TT
R
T
q
19. Wall Surfaces with Convection
2112
2
0 CxCTC
dx
dT
dx
Td
A
Boundary conditions:
11
0
)0(
TTh
dx
dT
k
x
22 )(
TLTh
dx
dT
k
Lx
Rconv,1 Rcond Rconv,2
T1 T2
20. Heat transfer for a wall with dissimilar
materials
• For this situation, the total heat flux Q is made up of the heat flux in the
two parallel paths:
• Q = Q1+ Q2
• with the total resistance given by:
Heat Transfer Circuit
23. 1 D Conduction(Radial conduction
in a composite cylinder)
22 Feb 2013 23
h1
T∞,1
k1
r1
r2
k2
T∞,2 r3
h2
T∞,1 T∞,2
)2)((
1
11 Lrh )2)((
1
22 Lrh
12
ln 2
1
Lk
r
r
22
ln 3
2
Lk
r
r
t
r
R
TT
q
1,2,
24. Logarithmic Mean area for hollow cylinder
• Convenient to have an expression for heat
flow through hollow cylinder of the same form
as that of for a plane wall.
• Then cylinder thickness will be equal to wall
thickness,
• Area will be equal to Am
22 Feb 2013 24
25. Logarithmic Mean area for
hollow cylinder
22 Feb 2013 25
22 1 1
22 1 1
ln( 2 / 1) ( 2 1)
2
ln( 2 / 1) ( 2 1)
ln( 2 / 1) ( 2 1) 2
2
2 ( 2 1) 2 ( 2 1)
ln( 2 / 1) ln(2 2 / 2 1)
2 1
ln( 2 / 1)
cylinder wall
m
m
m
m m
m
TT T T
Q and Q
r r r r
KL KA
TT T T r r r r
r r r r KL KA
KL KA
L r r L r r
A A
r r Lr Lr
A A
A
A A
26. Convection
• Heat transfer in the presence of a fluid motion on a solid surface
•Various mechanisms at play in the fluid:
- advection physical transport of the fluid
- diffusion conduction in the fluid
- generation due to fluid friction
•But fluid directly in contact with the wall does not move relative to it; hence
direct heat transport to the fluid is by conduction in the fluid only.
T(y)q”
y y
U T
Ts
u(y)
U
TTh
y
T
kq s
y
fconv
0
But depends on the whole fluid motion, and both fluid flow
and heat transfer equations are needed
0
y
y
T
T(y)
y TU
Ts
27. Convection
Free or natural convection
(induced by buoyancy
forces)
forced convection (driven
externally)
May occur with
phase change
(boiling,
condensation)
Convection
Typical values of h (W/m2K)
Free convection: gases: 2 - 25
liquid: 50 - 100
Forced convection: gases: 25 - 250
liquid: 50 - 20,000
Boiling/Condensation: 2500 -100,000
Heat transfer rate q = h( Ts-T )W
h=heat transfer coefficient (W /m2K)
(h is not a property. It depends on
geometry ,nature of flow,
thermodynamics properties etc.)
28. T(y)q”
y
U T
Ts
u(y)
U
Convection rate equation
Main purpose of convective heat
transfer analysis is to determine:
• flow field
• temperature field in fluid
• heat transfer coefficient, h
q’’=heat flux = h(Ts - T)
q’’ = -k(T/ y)y=0
Hence, h = [-k(T/ y)y=0] / (Ts - T)
The expression shows that in order to determine h, we
must first determine the temperature distribution in the
thin fluid layer that coats the wall.
29. • Nusselt No. Nu = hx / k = (convection heat transfer strength)/
(conduction heat transfer strength)
• Prandtl No. Pr = / = (momentum diffusivity)/ (thermal diffusivity)
• Reynolds No. Re = U x / = (inertia force)/(viscous force)
Viscous force provides the dampening effect for disturbances in the
fluid. If dampening is strong enough laminar flow
Otherwise, instability turbulent flow critical Reynolds number
d
Laminar Turbulent
d
Forced convection: Non-dimensional groupings
Forced convection
30. les
x q
Ts
T
h=f(Fluid, Vel ,Distance,Temp)
•Fluid particle adjacent to the
solid surface is at rest
•These particles act to retard the
motion of adjoining layers
• boundary layer effect
Momentum balance: inertia forces, pressure gradient, viscous forces,
body forces
Energy balance: convective flux, diffusive flux, heat generation, energy
storage
FORCED CONVECTION:
external flow (over flat plate)
An internal flow is surrounded by solid boundaries that can restrict the
development of its boundary layer, for example, a pipe flow. An external flow, on
the other hand, are flows over bodies immersed in an unbounded fluid so that the
flow boundary layer can grow freely in one direction. Examples include the flows
over airfoils, ship hulls, turbine blades, etc.