Heat exchangers are the important engineering equipments used for transferring heat from one fluid to another. Heat exchangers are widely used in various kinds of application such as power plants, nuclear reactors, refrigeration and airconditioning systems, heat recovery systems, petrochemical, mechanical, biomedical industries. Helical coil heat exchangers are gaining wide importance now-a-days because it can give high heat transfer coefficient in small footprint of surface area. This paper focuses on the designing of shell and helical coil heat exchanger and its thermal evaluation with counter flow configuration. The thermal analysis is carried out considering the various parameters such as flow rate of cold water, flow rate of hot water, temperature, effectiveness and overall heat transfer coefficient.

The present study reports an experimental analysis on heat transfer, friction factor and thermal performance characteristics of turbulent flow (7500 ≤ Re ≥ 13,000) in heat exchanger tubes with twisted tape as swirl generators under constant wall heat flux condition. The experiments were carried out for twisted tape inserts at five different width ratios (W/D) of 0.35, 0.44, 0.53, 0.62 and 0.71 at constant twist ratio (H/D) of 2.5. The experimental results show that Nusselt number increases with increasing Reynolds number and increasing width ratio (W/D) of the swirl generators. Also the friction factor decreases with increasing Reynolds number and decreasing width ratio. Nusselt number increased in ranges of 6.04% to 17.26% compared to the results of the tube without twisted tape (the plain tube), depending on the operating conditions. At the same pumping power, the use of twisted tape inserts results in thermal performance factor up to 1.17 times of those of the plain tube. In addition, the correlations that developed from the present experimental data for Nusselt number.

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The present research is concerned with the study and experimental investigation of the effect of HFC refrigerant R134a on a vapour compression refrigeration system by using two expansion devises with the conservation of energy by waste heat recovery system. Here two different evaporators are used for air cooling and water chilling respectively and a water cooled condenser is used to produce hot water. The existing system can be easily retrofitted as a waste heat recovery device and the existing R22 refrigerant can be replaced by R134a with minor modifications. R134a play a vital role for the protection of global environment and maintain ecological balance, from the view point of energy conservation. The maximum temperature achieved in water tank with 50 litre of water is 45 C during 3 to 4 working hour. After that performance of system decreases so it needs a regular use of that hot water which can be used for household and industrial purposes.