Heat exchangers find a wide variety of applications in the chemical industry employing fluids as heat transfer means. It is desirable to have heat exchangers with low pressure drop on all fluid steams, leading to low pumping power, good exchange of heat, maintaining inlet-outlet temperatures, minimizing size, cost and having specified design conditions. The tube system designed by IITB has elements of these features in the tube-tube heat exchanger (TTHE) designed by him.

The present invention of Tube-tube Heat exchangers (TTHE), has a combination of bends, straight lengths, tube diameter, tube material, thermal bonding that enables effective transfer of heat in multi-stream multi-phase heat transfer applications. Variation of mass flow rate of fluid stream/s at immediate stages in a single TTHE is possible. In the present invention judicious use of bends and straight lengths results in significant enhancement in heat transfer due to secondary flows induced in the bends. The secondary flows induced leads to enhancement in bend as well as in straight length downstream of bend without significant increase in pressure drop and pumping power. It options offers a double wall vented design eliminating the problem of mixing of fluid streams in case of leakage and offers the flexibility of utilizing diverse conduit materials that are compatible with the running fluids. It is highly efficient and cost saving design that can be used in the chemical industry.