Performance of wire finned coiled tube heat exchanger in a small J-T refrigerator

Non-azeotropic, mixed refrigerant of hydrocarbons nitrogen takes place in heat exchangers while boiling and condensation simultaneously at various cryogenic temperature and pressure. It is very difficult to design a heat exchanger in order to undergo boiling and condensation simultaneously. In the present paper, heat exchanger is designed numerically by applying the steady state conditions. Heat transfer coefficients are calculated numerically by applying homogenous model, which is developed by writing a computer programme. This model is validated with the experimental data. This study is carried out with three different refrigerant mixtures. Also, observed that a significant increase in percentage of heat transfer coefficient values in all the three mixtures considered in this study. It is found that 50% increase in tube side and 33% in shell side in the mixture 1 whereas in the mixture 2 it is 31% and 18% and similarly in the mixture 3 the increase is 40% in tube side and 20% in shell side. So the refrigerant with mixture 1 will perform better. Further the study is extended to heat exchanger with wire fin wound around the inner tube. It is observed that there is a significant improvement in heat transfer coefficient when wire fin is used. (C) 2019 Elsevier Ltd. Selection and Peer-review under responsibility of the scientific committee of the International Mechanical Engineering Congress 2019: Materials Science.