Heat Transfer Research Paper

CHAPTER-1

INTRODUCTION

Heat exchangers are important engineering devices in several process industries since the efficiency and economy of the process largely depends on the performance of the heat exchangers and other important engineering applications in heat exchangers such as power plants, air-conditioning, petrochemical industry, natural gas processing, refrigeration, solar water heater, chemical reactors, sewage treatment, shell and tube heat exchangers in nuclear reactors. The design procedure of heat exchangers is quite complicated, as it needs exact analysis of heat transfer rate and pressure drop estimations apart from issues such as long term performance and the economic aspect of the equipment. The major challenge in designing

In automobiles, the heat generated by the prime mover needs to be removed for proper operation. Similarly, electronic devices dissipate heat, which requires a cooling system. Heating, ventilation system and air conditioning systems also include various heat transfer processes. Heat transfer is the key process in thermal power stations. In addition to these, many production processes include heat transfer in various forms: it might be the cooling of machine tools, pasteurization etc. In most of these applications, heat transfer is improved through some heat transfer devices such as heat exchangers, evaporators, condensers and heat sinks. Increasing the heat transfer efficiency of these devices is suitable, because by increasing efficiency, the space occupied by these devices can be minimized, which is an important for applications with compactness requirements. Further, in most of the heat transfer systems, the working fluid is circulated by a pump, and improvements in heat transfer efficiency can minimize the associated power

If the circulation rate of the fluid is increased, sedimentation is reduced, but the erosion of the heat transfer devices, pipelines, etc., increases rapidly.

3. The large size of the particles tends to clog the flow channels.

4. The pressure drop in the fluid increases rapidly.

5. Finally, enhancement of conductivity based on particle concentration is achieved (i.e., the greater the particle volume fraction is, the greater the enhancement and greater the problems, as indicated above).

However, the emergence of modern materials technology provided the opportunity to produce nanometer-sized particles which are quite different from the previous material in mechanical, thermal, electrical, and optical properties.

1.1 Emergence of Nano fluids

Choi and Eastman [24] in Argonne National Laboratory revisited this field with their nano scale metallic particle and carbon nanotube suspensions. They have tried to suspend various metals and metal oxides nanoparticles in different fluids. Their results are promising, however, many things remain elusive about these suspensions of nano structured materials, which have been termed “Nano fluids”.

1.2 Applications of Nano