This book is concerned with the study of the effect of Electrohydrodynamics on the heat transfer properties of a tube-in-in heat exchanger with the parallel flow and counter flow. The primary fluid (hot water, steam, etc.) flows through tubes of the heat exchanger and secondary fluid (cold fluid-dielectric fluid) flows through the annulus region of a casing. The electric field is generated by using wire electrodes. The main aim is to study the heat transfer properties of the heat exchanger with the electric field and without an electric field in the presence of dielectric fluid (as a secondary fluid) and comparison of heat transfer rates for normal operation and with electrohydrodynamic effect.