Deep-water production requires more and more advanced pipeline insulation to produce under safety conditions. For less than ten years, the research focuses on such insulation systems as pipe in pipe and more recently on pipeline bundles, system composed by some pipe sets within a carrier pipe. Then, attempts have been made to take into account the bundles modelisation in a transient multiphase flow model. The TACITE compositional code is able to simulate the behavior of transient multiphase flow in pipelines with process equipments such as controllers, valves, separators and lateral injectors. A transient pipeline bundle module has been developed to analyse the thermal interactions between several single phase lines and the main production line. The model is based on the numerical resolution of a set of energy balance equations, defined for each lines and the annulus medium within the bundle, to compute the heat transfer between the main production line, all the single phase lines, the carrier pipeline and the outside. The natural convection is taken into account in the annulus area. The SYSTUS code developed by SYSTUS International is currently used at Stolt Offshore to solve thermal engineering problems including pipeline bundles. The results of SYSTUS output have been checked against full size bundle test and then can be considered as a reference in this domain. Different simulations have been done with SYSTUS and TACITE in multiphase conditions in order to validate TACITE. This illustrates that the model developed for TACITE is both efficient and accurate. Also the simulation results demonstrate that it is important to take accurately into account thermal effects is case of deep-water production to predict phenomena such as hydrate formation or was deposition.