Primary Heat Transport System - pressure drop and pumping power - HCPB

[ym1906]

If the primary coolant is helium, the pumping power is of the order of 100 MW so it is important to get it right. EUROfusion have calculated the flow rate and pressure drop for the primary coolant circuit of the HCPB concept.

• Check that we believe these values, and
• Find a way to make them parametric.

EDIT 27/1/25 and 3/2/25

The latest EUROfusion design uses separate water-cooled limiters to protect the breeding blanket from the highest surface heat fluxes.
At this stage we are interested in the helium only.
This report covers the whole of the PHTS with molten salt energy storage, including the helium-salt heat exchanger:
EFDA_D_2NZL6Z - HCPB BB PHTS DDD (Indirect Coupling Option) - Long Version]

Circulator

This report covers the whole of the PHTS and discusses the circulator at length:
EFDA_D_2NZL6Z - HCPB BB PHTS DDD (Indirect Coupling Option) - Long Version]

The most important engineering constraint on the circulator performance is the outlet/inlet pressure ratio. Siemens have suggested an upper limit of 1.05. DEMO currently uses 1.03. Table 6.3 in the above report lists helium and CO2 circulators used in nuclear reactors in the (distant) past. Note that the speed of sound in helium is much higher than in CO2, so experience from CO2 circulators is not that relevant.

EFDA_D_2QH9J2 - BB-S.02.01-T001-D016: Dedicated Thermo-hydraulic CFD Analyses for HCPB – Report 2022
The integrated engineering design concept of the upper limiter within the EU-DEMO LIMITER system
EFDA_D_2RJ4AS - BB-S.02.01-T001-D019: Design Description Document (DDD) of the HCPB BB - 2022

This means that the mass flow rates and pressure drops are fairly uniform over the breeding blanket. There are localised regions where higher mass flow rates are required, but it might be reasonable to say that these could be eliminated with suitable effort.

Guangming acknowledges that one should use the maximum pressure drop and not the mean; and also mentioned that the pressure drop calculation in his paper (below) were done only for the outboard side, even though the highest flow rates were on the inboard side.

Older papers and reports
Primary pumping and energy conversion ("BoP") models (GitLab Issue 503, not carried over to GitHub)
PROCESS_primary_pumping_and_BoP_models.docx

Thermal hydraulics activities for consolidating HCPB breeding blanket of the European DEMO (2020)

This is a good paper in many ways, but I am not sure about the conclusion that the overall pressure drop in the blanket segment is 0.7994 bar. This is based on averaging the pressure drops of the different first wall channels, rather than taking the maximum. The pressure drop in the first wall channel with the highest flow is much greater than this. The conclusion is show here:

This spreadsheet is comprehensive, but doesn't explain how the pressure drops are calculated:
Saved version without figures: HCPB_-_Relevant_data_of_BB_PHTS_and_IHTS_2NDGNW_v1_0 (1).xlsx
Link to complete version: EFDA_D_2NDGNW - HCPB - Relevant data of BB PHTS and IHTS - 2019

It gives the pressure drops for the whole of the PHTS, but it doesn’t provide any details for how the pressure drop in the blanket (79.9 kPa) is calculated. The total is 265.8 kPa, which is the same as the value in the paper by Evaldas:
Overview of thermal hydraulic optimization and verification for the EU-DEMO HCPB BOP ICD variant
W Hering, E Bubelis, et al

Figure 3 is a flow diagram from the EBSILON code. No details of the blanket or heat exchangers are given but it shows pressures, flows and temperatures. The parameters are as follows:

Blowers pumping power (total of 8 blowers): 87.954 MW
Upper left helium circuit:
Blower outlet = 80.270 bar
Return from blanket = inlet to helium/salt heat exchanger = 78.282 bar
Outlet from heat exchanger = blower inlet = 77.611 bar

• Pressure drop (entire circuit) = 80.270 - 77.611 = 2.659 bar = 265.9 kPa.

How to make the model parametric

The options available at the moment:

primary_pumping : This switch controls the calculation of the mechanical pumping power required for the primary coolant.

• If primary_pumping = 0, the user sets mechanical pumping directly
• If primary_pumping = 1, the user sets mechanical pumping power as a fraction of thermal power removed by coolant. This is scalable, provided the fraction is independent of the size and shape of the machine, and of the permissible first wall temperature (if these are to be variable). Matti's calculation (see above) relates this fraction directly to the pressure drop (option 3).
• If primary_pumping = 2, the mechanical pumping power is calculated using a fairly detailed model.
• If primary_pumping = 3, the mechanical pumping power is calculated using specified pressure drop. The pressures and temperatures are set by the user. This is scalable if the pressure drop is regarded as a constant.

Originally posted by @mkovari in #3491