16 Slices
Medium 9788131806135

he16-1

Mahesh M. Rathore Laxmi Publications PDF

Experiments in

Engineering Heat Transfer

16

Expt. 1 Thermal Conductivity of Metallic Rod. Expt. 2 Thermal Conductivity of Insulating Powder. Expt. 3 Thermal Conductivity of Composite Wall. Expt. 4 Natural Convection Experiment. Expt. 5 Forced Convection Experiment. Expt. 6 Heat Transfer from Pin

Fins. Expt. 7 Stefan Boltzmann Constant. Expt. 8 Measurement of Emissivity of a Test Surface. Expt. 9 Heat Exchanger Experiment.

Expt. 10 Critical Heat Flux. Expt. 11 Heat Pipe. Expt. 12 Thermocouples Calibration Test Rig—Review Questions—References

Engineering education has placed a great emphasis on the ability of an individual to perform experiments along with a theoretical analysis of the problems. The experimental methods have their own importance. They help in better understanding of the basic principles of the subject and to verify the result obtained analytically.

Therefore, in engineering curiculla, the students are expected to devote one laboratory period a week for experimentation. The students are exposed to the basic instruments and get acquainted with the methods used for measuring the physical properties.

See All Chapters
Medium 9788131806135

he14-1

Mahesh M. Rathore Laxmi Publications PDF

Heat Exchangers

14

14.1. Classification of Heat Exchanger. 14.2. Temperature Distribution. 14.3. Overall Heat Transfer Coefficient. 14.4. Fouling Factor.

14.5. Heat Exchanger Analysis. 14.6. Log Mean Temperature Difference Method—Parallel flow heat exchanger—Counter flow heat exchanger—Condenser—Evaporator. 14.7. Multipass and Cross Flow Heat Exchangers. 14.8. The Effectiveness-NTU Method—Heat exchanger effectiveness—NTU—Capacity ratio—Effectiveness of a parallel flow heat exchanger—Effectiveness of a counter flow heat exchanger. 14.9. Rating of Heat Exchangers. 14.10. Sizing of Heat Exchangers. 14.11. Compact Heat Exchangers. 14.12. Plate Heat

Exchanger (PHE). 14.13. Requirements of Good Heat Exchanger. 14.14. Heat Exchanger Design and Selection. 14.15. Practical

Applications of Heat Exchangers. 14.16. Heat Pipes. 14.17. Summary—Review Questions – Problems – References and Suggested

Reading.

A device used for exchange of heat between the two fluids that are at different temperatures, is called the heat exchanger. The heat exchangers are commonly used in wide range of applications, for example, in a car as radiator, where hot water from the engine is cooled by atmospheric air. In a refrigerator, the hot refrigerant from the compressor is cooled by convection into atmosphere by passing it through finned tubes. In a steam condenser, the latent heat of condensation is removed by circulating water through the tubes. The heat exchangers are also used in space heating and air-conditioning, waste heat recovery and chemical processing. Therefore, the different types of heat exchangers are needed for different applications.

See All Chapters
Medium 9788131806135

he12-1

Mahesh M. Rathore Laxmi Publications PDF

Thermal Radiation:

Properties and Processes

12

12.1. Theories of Radiation—Maxwell’s theory—Max Planck’s theory. 12.2. Spectrum of Electromagnetic Radiation. 12.3. Black body

Radiation. 12.4. Spectral and Total Emissive Power. 12.5. Surface Absorption, Reflection and Transmission. 12.6. Black body

Radiation Laws—Black body spectral emissive power—Wien’s displacement law—Stefan Boltzmann law—Radiation function and band emission. 12.7. Emissivity—Hemispherical and total emissivity—Spectral emissivity—Directional emissivity—Kirchhoff’s law—Gray and diffuse surfaces : Gray Lambert body approximation. 12.8. Radiation From a Surface—Solid angle—Spectral intensity of radiation (Ibλ)—

Radiation intensity (Ib). 12.9. Radiosity. 12.10. Solar Radiation—Solar radiation on the earth—Atmospheric emission—Green house effect—

Selective surfaces. 12.11. Summary—Review Questions—Problems—References and Suggested Reading.

Thermal radiation or radiation heat transfer is a distinct separate mechanism from conduction and convection for transfer of heat energy. It refers to the heat energy emitted by the bodies because of their temperatures. All bodies at a temperature above absolute zero temperature emit energy by a process of electromagnetic radiation. The intensity of such radiation depends upon the temperature and nature of the surface. The energy transfer by radiation does not require any medium between hot and cold surfaces. The energy transfer by radiation is the fastest (at the speed of light) and it does not suffer any attenuation even in the vacuum. In fact, the heat transfer through an evacuated space can occur only by radiation. When a person sits infront of a fire, he gets most of the heat energy by radiation as shown in Fig. 12.1. Further, it is also interesting that the radiation heat transfer can also occur between two bodies separated by a medium that is colder than the both bodies. For an example, the energy emitted by sun reaches the earth surface after travelling through space and extremely cold air layers at high altitudes.

See All Chapters
Medium 9788131806135

he8-1

Mahesh M. Rathore Laxmi Publications PDF

8

External Flow

8.1. Laminar Flow Over a Flat Plate—Approximate analysis of momentum equation—Approximate analysis of energy equation. 8.2. Reynolds

Colburn Analogy : Momentum and Heat Transfer Analogy for Laminar Flow Over Flat Plate. 8.3. Turbulent Flow Over a Flat Plate.

8.4. Combined Laminar and Turbulent Flow. 8.5. Flow Across Cylinders and Spheres—Drag coefficient—Heat transfer coefficient.

8.6. Summary—Review Questions—Problems—References and Suggested Reading.

When a fluid flows over a body such as plate, cylinder, sphere etc., it is regarded as an external flow. In such a flow, the boundary layer develops freely without any constraints imposed by adjacent surfaces. Accordingly, the region of flow, outside the boundary layer in which the velocity and temperature gradients are negligible is called the free stream region.

In an external flow forced convection, the relative motion between the fluid and the surface is maintained by external means such as a fan or a pump and not by buoyancy forces due to temperature gradients as in natural convection.

See All Chapters
Medium 9788131806135

he2-1

Mahesh M. Rathore Laxmi Publications PDF

Conduction—Basic Equations

2

2.1. Generalised One Dimensional Heat Conduction Equation. 2.2. Three Dimensional Heat Conduction Equation—For the cartesian coordinates—Three dimensional heat conduction equation in cylindrical coordinates—Three dimensional heat conduction equation in spherical coordinates. 2.3. Initial and Boundary Conditions—Prescribed temperature boundary conditions—Prescribed heat flux boundary conditions—Convection boundary conditions : Surface energy balance—Radiation boundary condition—Interface boundary condition. 2.4. Summary—Review Questions—Problems.

The objective of this chapter is to provide a good understanding of the heat conduction equations and boundary conditions for the use in mathematical formulation of heat conduction problems.

2.1.

GENERALISED ONE DIMENSIONAL HEAT

CONDUCTION EQUATION

For the thermal analysis of the bodies having shapes such as slab, rectangle, the cartesian coordinates are used, while for cylindrical and spherical bodies, the polar and spherical coordinate systems are used.

See All Chapters

See All Slices