Sultan Qaboos University
College of Engineering
Department of Mechanical & Industrial Engineering

Heat Transfer
Lab report

Free & Forced Convection Heat Transfer

Mahmood Mohsin AL-Khusaibi85135
Amur Sultan Al-Habsi 86260
Rashid Nasser Al Shabibi85362

Aim:
The objective of this experiment to investigate the use of extended surface to improve heat transfer through surfaces. In addition, another target is to demonstrate the effect of the fluid speed on the heat transfer by convection.

Introduction:
Heat transfer by convection is one of three heat transfer methods which are conduction, radiation and convection. Convection is form of energy transfer between a solid surface and the adjacent fluid. It engrosses the mixed effect of the fluid velocity and conduction. The fluid velocity and the surface area effect are both proportional with the rate of heat transfer.

Theory:
Heat transfer due to convection is expressed by Newton’s law of cooling as:

Qconv = hAs(Ts-Tinf)…………..(1)

Where h is the convection heat transfer coefficient and As is the effected surface area. Heat transfer can be improved by using a larger surface area however, in practice this not always applicable. In similar situation, the surface area can be increased by adding fins or pins. This effect can be demonstrated by comparing different types of extended surface area with a flat plate.

Apparatus:
The apparatus used in this are the duct that work like a wind tunnel different types of plates for heat transfer (flat, pined, finned), heat generator and a stopwatch for time measurement.

Procedure:
First of all, Apparatus for this experiment was prepared. Then, the flat plate heat exchanger was fitted into the duct. Heat power control was set to 75w till the temperature reaches steady state. After that, heat power control was set to 20 w till the temperature reaches steady state once again. Once that happened the temperature was...

...Experiment 8 - Free & ForcedConvectionConvectionHeat Transfer.doc
EXPERIMENT ON FREE AND FORCEDCONVECTIONHEATTRANSFER 8.1 OBJECTIVES To study experimental data for heattransfer in order to evaluate the overall heattransfer coefficients and heat balances for the following cases of heattransfer in a .shell and tube heat exchanger. (a) Natural convection and (b) Forcedconvection. 8.2 THEORY A basic diagram of a shell and tube heat exchanger is shown in Figure 8.1. Here steam at a temperature of Tv is sent to the shell side at the port A at a rate of W kg/s. The steam transfersheat to a fluid at the tube side .The steam condenses during this process and leaves the shell side at the port B at a temperature Ts. The tube side fluid enters the heat exchanger at C with a flow rate of M kg/s at a temperature Ti and leaves at D at a temperature To. The heat loss QH from the steam can be expressed as QH = W(λ + CpH.(Tv-Ts)) Similarly, the heat gained by the tube side fluid QC can be expressed as QC= M.CpT. (Ti-To) The heattransfer coefficient for the shell side and tube...

...ForcedConvectionHeatTransfer
I. Introduction
This laboratory deals with forcedconvection, forcedconvection can be considered as a staple of heattransfer. That is to say that forcedconvection can be found in almost any heattransfer problem, and thus understanding its importance and how it affects a given problem is one of the more important learning objectives/outcomes of heattransfer.
When dealing with forcedconvection the most important section, after understanding how convection works, is the convectionheattransfer coefficient. The heattransfer coefficient for convection is denoted by (h) and is measured in w/m^2*K, this lab delves into the application of convectionheattransfer and how it correlates to temperature, velocity, ect of the fluid in question.
II. Objectives
The objectives for this laboratory include; determining the convective heattransfer coefficient and friction factor of the air flowing through a copper pipe, as well as evaluation of the Reynolds analogy and taking measurements of the radial velocity and temp...

...FREESTUDY
HEATTRANSFER
TUTORIAL 2
CONVECTION AND RADIATION
This is the second tutorial in the series on basic heattransfer theory plus some elements of advanced
theory. The tutorials are designed to bring the student to a level where he or she can solve problems
ranging from basic level to dealing with practical heat exchangers.
On completion of this tutorial the student should be able to do the following.
•
•
Explain the use of the surface heattransfer coefficient.
•
Explain the use of the overall heattransfer coefficient.
•
Combine convection and conduction theory to solve problems involving
flat, cylindrical and spherical surfaces.
•
Explain the basic theory behind radiated heattransfer.
•
Explain the affect of the emissivity and shape of the surface.
•
Calculate effective surface heattransfer coefficient.
•
(c) D. J. Dunn
Explain natural and forcedconvection.
Solve basic problems involving convection and radiation.
1
CONVECTIONConvection is the study of heattransfer between a fluid and a solid body. Natural convection occurs
when there is no forced flow of the...

...HeatTransfer by Convection
Ch.E. 324 Based on the lecture notes of Prof. Alberto Laurito
Learning Objectives
At the end of the discussion you should be able to: • differentiate convection from conduction • identify whether a heattransfer by convection is forced or natural • solve individual film coefficients(h) and overall heattransfer coefficients(U) in a double pipe heat exchanger.
Convection
- heat is transferred due to a mixing process between cold and hot portions of a fluid. Two Types of Convection 1. Forcedconvection - mixing is due to mechanical means such as pumps, compressors, agitators. 2. Natural convection - mixing is due to density difference arising from temperature gradient.
Convection
APPLICATIONS: 1. Double pipe heat exchanger* 2. Shell and tube heat exchanger 3. Bank of tubes 4. Film type condensation
Film Concept
Metal wall
Ti
Cold fluid Tb To Ta Hot fluid
• When a rapidly moving fluid comes in contact with a stationary phase, a thin film is formed.
q
Inner film
•The thin film acts as a boundary layer between the moving fluid and the wall.
•The thin film contributes an additional resistance to heat flow.
outer film...

...Forced and freeconvection Laboratory
Introduction
Convection, along with conduction and radiation is one of the three ways in which heat is transferred. In convection, heat can be exchanged from one fluid to another. In this experiment, a heated plate is in contact with air inside a rectangular cross section duct. The air is heated by conduction from the heated plate. The density of the air decreases as it is heated and this makes the warm air rise. Colder air, which in turn is less dense, then replaces the warmer air, which has risen. The plate then heats this colder air, which will eventually rise to be replaced by colder less dense air. This is known as freeconvection. However in forcedconvection, the flow of air is not due to small currents set up by natural convection. Forcedconvection is due to a large interfering flow of air such as a fan.
Aims and objectives
The aim of this laboratory experiment it to find the convectionheattransfer coefficient of a flow of air that is flowing over a heated plate at a known speed. The convectionheattransfer coefficient can be determined using the values of temperatures recorded, the area of the heated plate and finally the energy...

...3rd Year Thermodynamics Lab Report
Mechanical Engineering Science 10
ForcedConvection (in a cross flow heat exchanger)
Summary
The aim of this lab is to determine the average convective heattransfer coefficient for forcedconvection of a fluid (air) past a copper tube, which is used as a heattransfer model.
Introduction
The general definition for convection may be summarized to this definition "energy transfer between the surface and fluid due to temperature difference" and this energy transfer by either forced (external, internal flow) or natural convection.
Heattransfer by forcedconvection generally makes use of a fan, blower, or pump to provide high velocity fluid (gas or liquid). The high-velocity fluid results in a decreased thermal resistance across the boundary layer from the fluid to the heated surface. This, in turn, increases the amount of heat that is carried away by the fluid. [1]
Theory Background [2]
Considering the heat lost by forcedconvection form the test rod. The amount of heat transferred is given by
(1)
Where
= rate of heattransfer, unknown...

...Mechanisms of HeatTransfer
Prepared by: Ms. Ana Antoniette C. Illahi
1
Conduction
• conduction (or heat conduction) is the transfer of thermal energy between regions of matter due to a temperature gradient. Heat spontaneously flows from a region of higher temperature to a region of lower temperature, and reduces temperature differences over time, approaching thermal equilibrium.
Prepared by: Ms. Ana Antoniette C. Illahi
2
(Heat Current in Conduction)
• • • • • • • • H - Heat Current dQ – Quantity of Heat dt – Time dQ/dt – the rate of heat flows A – Cross sectional area (TH - TC) – Temperature difference L – Length k – constant (thermal conductivity)
Prepared by: Ms. Ana Antoniette C. Illahi
H = dQ/dt = kA (TH - TC)/L
3
Conduction
H = dQ/dt = -kA (dT/ dx) H = A(TH - TC) / R R = L/ k R – thermal resistance
Prepared by: Ms. Ana Antoniette C. Illahi 4
Thermal Conductivities k (W/m oC)
Metals Aluminum Brass Copper Lead Mercury Silver Steel 205.0 109.0 385.0 34.7 8.3 406.0 50.2
Prepared by: Ms. Ana Antoniette C. Illahi 5
Solids (representative values) Brick. Insulating 0.15 Brick. red 0.6
Concrete 0.8
Cork Felt Fiberglass Glass Ice Rock wool Styrofoam Wood
0.04 0.04 0.04 0.8 1.6 0.04 0.01 0.12-0.04
Prepared by: Ms. Ana Antoniette C. Illahi 6
Gases Air Argon Helium Hydrogen Oxygen
0.024 0.016...

...HEATTRANSFERHeattransfer, also known as heat flow, heat exchange, or simply heat, is the transfer of thermal energy from one region of matter or a physical system to another. When an object is at a different temperature from its surroundings, heattransfer occurs so that the body and the surroundings reach the same temperature at thermal equilibrium. Such spontaneous heattransfer always occurs from a region of high temperature to another region of lower temperature, as required by the second law of thermodynamics.
In engineering, energy transfer by heat between objects is classified as occurring by heat conduction, also called diffusion, of two objects in contact; fluid convection, which is the mixing of hot and cold fluid regions; or thermal radiation, the transmission of electromagnetic radiation described by black body theory. Engineers also consider the transfer of mass of differing chemical species, either cold or hot, to achieve heattransfer.
II. THREE MODES OF HEATTRANSFER
1. Conduction
In heattransfer, conduction (or heat conduction) is the transfer of thermal energy between neighboring molecules in...