Two-phase heat transfer is a complex phenomenon. The mechanisms of boiling and condensing vary from application to application
In two-phase flow, as with single-phase, creating radial movement in the boundary layer and in the bulk flow will enhance the rate of heat transfer. The heat transfer mechanisms are often complex and may vary considerably along the tube length, from tube to tube and pass to pass. The unique construction and variable geometry of hiTRAN Matrix Elements allows the designer to optimise the level of enhancement needed at any position along the flow length. This may require full or partial fitting within a tube and installed in one or more passes.
Depend upon the particular application parameters, may include;
Upon commissioning, a steam-heated LNG vapouriser was subject to liquid carry-over prior to reaching design capacity, indicating incomplete vapourisation. Analysis showed that the creation of a mist-flow regime in the outlet tube pass was preventing efficient vapourisation of the remaining liquid. hiTRAN Thermal Systems were specified to intercept and vapourise liquid droplets, achieving full design capacity. Case Study 4 (CS4).
A vent condenser serving a filter / dryer package on a fine chemicals plant was undersized, causing excessive quantities of methanol to be vented to the atmosphere and breaching emissions limits. Retro-fit of hiTRAN systems allowed the dew point of the vent stream to be reduced significantly, retaining the volatile components within the process and bringing emissions within the standard required by environmental regulators.
In order to achieve an increase in throughput, an operator required an uprate of a large shell and tube condenser operating under vacuum. A hiTRAN Thermal System was specified within pressure drop constraints which would allow condensing heat transfer to be significantly improved in the lower half of the vertical unit. The hiTRAN Matrix Elements were easily installed within a short shutdown. Upon restart the condenser achieved a 30% increase in duty, providing a payback within two months.
A forced flow reboiler serving a motor oil recycling plant suffered regular fouling due to high tube wall temperatures and long fluid residence times. By increasing boiling heat transfer coefficients with hiTRAN Matrix Elements, the wall temperature was lowered, greatly extending run times. System payback was estimated at 30 days.