Heat exchangers are used to transfer heat from one fluid stream to another fluid stream. Coiled TiTHEXs (Tube in tube Heat exchangers) are widely used in refrigeration, air-conditioning and cryogenic applications. Research has been carried out extensively on coil tubes to assess their performance. Studies on overall system level with these heat exchangers, is done by a few while some studies reported the correlations for Nusselt number and friction factor to estimate the heat transfer coefficients and pressure drops. Most of the work is done on coiled tubes, but there is a wide gap in literature in the estimation of the friction factor and rate of heat transfer in multiple TiTHEXs. The present paper deals with review of coiled tube heat exchangers over past few decades and also discuss about the importance of multiple TiTHEXs which would helpful to the researchers to have a precise selection of a device used in cryogenic applications. © IAEME Publication.