Investigation of Non-ideal Behavior of Plate-fin Heat Exchangers in LNG Services

Abstract

Using a heat exchanger with several parallel channels in boiling services, static instabilities like the Ledinegg instabilities can occur, resulting from a combination of unfortunate operating conditions and the heat exchanger design. Ledinegg instability is characterized by different flow rates in parallel channels that share common inlet and outlet manifolds. Oscillations between different conditions may also occur. In a thermodynamic system like liquefaction of natural gas, the fluids can exhibit a large temperature glide during condensation and evaporation and the actual local fluid temperature inside a heat exchanger will then be directly dependent of the local mass-flow. This means that mass-flow oscillations also imply thermal oscillations. This study shows how this type of non-ideal behavior can be predicted for a plate-fin heat exchanger by requiring all channels for each stream to have equal pressure drop. These nonlinear equations are solved on top of the thermo-hydraulic simulation model for the heat exchanger core.

Rating and performance of plate fin heat exchanger used for cryogenic separation of CO 2

“…The value of “△ p ” is one of the important design factors and it affects the dimension, selection of the fins, and determination of the length of PFHE 52 . The “△ p ” data is more helpful to optimize the geometric parameters in PFHE for the reduction of manufacturing costs 53 …”

“…52 The "4p" data is more helpful to optimize the geometric parameters in PFHE for the reduction of manufacturing costs. 53…”

From Droplets to Process: Multilevel Research Approach to Reduce Emissions from LNG Processes

“…The results showed that to avoid having an excessive large heat exchanger, a MITA between 4-5 was more realistic that 0.5-2 as often used in optimization literature. The SMR process layout and the main results are shown in Figure 4a Another example showing the flexibility of the modeling framework is shown in [19] where a plate-fin heat exchanger is modelled and a configuration using a lumped-stream approach is compared to a configuration using individual layers. With individual layers, effects of stacking pattern on flow mal-distribution and heat exchanger performance can be studied as well situationa where multiple solutions can exsist, known as static or Ledinegg instability.…”