The pressure drop through the condenser is not negligible in relation to the total pressure. The relatively high pressure drop may affect the condenser performance negatively.
This message just points out that the calculation was performed using the double vapor connection option set, i.e. with two vapor inlet connections.
This message is shown when the estimated two-phase channel inlet velocity is greater than 100 m/s and is a very strong signal indeed to rerun the case using a heat exchanger with larger port diameter to avoid the possibility of erosion of the plate. The channel velocity refers to the velocity on the edge of the plate in the very beginning of a channel.
High liquid flow rate might lead to erosion in the connections and ports. Try to decrease mass flow and/or select BPHE with larger ports. SSP indicates the port velocity, never the connection velocity. Connection velocity can be calculated in the Connection impact tool. By using titanium plates and connections, a slightly higher velocity up to 6.5 m/s is possible.
This message is shown when the estimated two-phase channel inlet velocity is greater than 100 m/s and is a very strong signal indeed to rerun the case using a heat exchanger with larger port diameter to avoid the possibility of erosion of the plate.
The pressure recovery in the inlet port is more than one third of the total pressure drop causing a pressure increase of more than 5 %. If this message is shown, it is recommended that the case is rerun using a heat exchanger with larger port diameters.
The reason for this warning is a too high port pressure drop in relation to channel pressure drop. This leads to channel mal distribution of secondary side. High pressure drop is often due to high flow rate in small ports. SWEP recommend to rerun the selection with a heat exchanger with larger port diameters and/or higher channel pressure drop (e.g. using a heat exchanger with higher chevron angle H>M>L).
The evaporation and condensation verification tests in the SWEP laboratory are for practical reason maximized in heat flux. This warning show that design is above these test points. Design may still be valid but check with SWEP sales representative for very high values, i.e. for evaporators and condensers above 20 kW/m2.
When you run the program using the heat recovery option, this message displays the total pressure drop in the heat exchanger if the gas of inlet conditions was flowing alone without condensation, i.e. if secondary side is inactivated.
Channels connected to ports F1-F4 have a pattern with low (L) chevron angle, while the channels connected to F2-F3 have a pattern with high (H) chevron angle and smaller ports. A high chevron angle enables more efficient heat transfer, but to the expense of larger pressure drop. When applying B60 as condenser, it is therefore important that the refrigerant enters through F2 port and leaves through F3 port to reach the requested performance.
The BPHE has been tested at lower heat flux than calculated. The SSP model is optimized for the tested heat flux range and selection outside this range can be less accurate. Please contact SWEP representative for further support.
In SSP there are for some condensers both a regular BPHE and a NHP-BPHE. The regular BPHEs are intended for the condenser window and the NHP-BPHEs are intended for the condenser heat pump window.
SWEP tests BPHEs at different thermal cases depending on what application the BPHEs are intended for. Two phase calculations need correction factors to have optimal fit test data.
The NHP-BPHEs are tested at heat pump conditions according to EN14511 and have correction factors in SSP optimized for heat pump calculations. The corrections for NHP-BPHEs fits test data best at low temperature approaches.
Regular BPHEs are often tested for chiller conditions and their corrections do often fit test data best in higher temperature approaches than the NHP-BPHEs.
For which temperature approach the condenser heat pump window should be used depend on the model, follow the recommendations in the warning texts.
Use condenser heat pump window if the temperature approach is ≤1K.
Use regular condenser window if the temperature approach is ≥2K.
This warning is shown if the temperature difference between the two fluids in the BPHE is low. The reason could be:
An example of an issue with very tight pinch is at instable operation where fluctuating SH directly will push down the evaporation temperature and thus lower the performance of the system. Try modifying the thermal case to avoid the pinch. This will minimize uncertainty and unnecessarily large heat transfer area.