A review on heat exchanger thermal hydraulic models for cryogenic applications

Heat exchangers are the main components in cryogenic processes. Thermo-economic considerations set the need for high-effectiveness equipment and accurate models. This situation is challenging due to the complex operating conditions and the fact that some physical effects, such as changes in fluid properties, flow maldistribution, axial conduction and heat leakage, cannot be neglected.In this work a systematic review of the state of art and challenges in modeling cryogenic heat exchangers is presented. They include lumped parameters, distributed parameters and stream-evolution models. These formulations fail to take all relevant effects into account.A general discussion on the performance of the reviewed models is presented. In general, more effects are included in the framework of numerical solution of discretized energy balance equation. Two main points stand out as not considered by the present models, namely the effects of pressure drop on heat transfer and the existence of partial flow mixing. These two effects are highly relevant for two-phase flow and multi-component applications, as in LNG processes.

► Cryogenic heat exchangers are designed for high-effectiveness.
► Two main challenges: complex operating conditions and non-negligible effects.
► Traditional model do not consider all relevant physical effects for cryogenics.
► State-of-the-art models are reviewed: some advantages for single phase flow.
► Major limitations: effects of pressure drop on heat transfer and partial mixing.