Heat Exchanger Test Stand Facility

Sandia National Laboratories’ Heat Exchanger Test Stand Facility can perform prototype 20- to 40-kilowatt heat exchanger performance analysis, and consists of multiple different particle, molten salt, CO₂, air, and glycol flow loops for precise control of system pressures, densities, flow rates, and temperatures. Our test stand is ready to test and demonstrate the performance of your next generation heat exchanger technologies.

System Overview

The National Solar Thermal Test Facility features a versatile test stand designed for evaluating prototype heat exchangers within a high-temperature particle or molten salt circulation system. The system is supported by adaptable heat extraction and cooling loops.

Key features:

Test area: 22” x 30” x 40” (L/D/H)
Accommodates many types of heat exchangers: molten salt, particle, sCO₂, and steam
Vertical installation of test article
Continuous, high-temperature particle loop
Supercritical CO₂ heat extraction system
Flexible, mobile layout of subsystems to accommodate your needs
Dry-cooling and chiller-coupled glycol extract heat with combined 60 kW thermal capacity
Remotely controlled to ensure safety
Operation requires trained Sandia staff members

Heat Exchanger Test Stand. The test facility is split into two
separate rooms: a control room for all remote operations
and data acquisition, and the adjacent 350 ft² test cell
containing the flow loops.

Test Your Heat Exchanger Using Our Facility

Sandia’s Heat Exchanger Test Stand (HX Stand) was funded by the U.S. Department of Energy and is available for use by external partners such as private industry and technology developers, universities, equipment manufacturers, government agencies, and national laboratories. For a complete system overview and breakdown of components, specifications, and procedures, read our Heat Exchanger Stand Brochure.

Operating Conditions

Actual test conditions vary by heat exchange design and accompanying equipment such as inlet and outlet hardware, flow control mechanisms, pressure ratings. However, Sandia’s Heat Exchanger Test Stand can accommodate the following conditions:

Aspect	sCO₂Loop	Particle Loop	Air Supply	Glycol (Loop 1)	Glycol (Loop 2)
Flow Rate	0-250 g/s	0-250 g/s	0-1000 slpm	0-10 gpm	0-10 gpm
Supply Temperature Range	30-575 °C	25-775 °C	0-400 °C	20-50 °C	15 – 50 °C
Pressure Range	1160 – 2500 psig (8-17.2 MPa)	N/A	0 – 130 psig (0-0.9 MPa)	0 – 30 psig (0-0.2 MPa)	0 – 30 psig (0-0.2 MPa)

Components

System Parameter Table

The table below summarizes the parameters, design attributes, and operating conditions for heat exchangers that can be supported by the heat exchanger test stand. Together, these parameters define the operating range and integration capabilities of the test stand for evaluation of heat exchanger performance.

Parameter	Supercritical CO₂ Loop	Particle Loop	Salt Loop
Heat Exchanger Inlet Temperature Range	30-575 °C	25-775 °C	300-775 °C (salt chemistry dependent)
Heat Exchanger Outlet Temperature Range	30-700 °C	25-700 °C	300-775 °C (salt chemistry dependent)
Operating Pressure	1160 – 2500 psig (8-17.2 MPa)	Atmospheric	0-110 psig (0-0.75 MPa)
Flow Rate	0-250 g/s	0-250 g/s	0-2000 g/s
Density Range	850 -960 kg/m³	N/A, dependent on particle bulk	1000-2000 kg/m³, dependent on salt chemistry
Heating	20 kW electric heating, or recovery of carried sCO₂ heat via recuperation	60 kW electric heating	20 kW electric heating
Supported Fluids/Heat Transfer Media	Liquid CO₂ from siphon tube bottles or dewar, pressurized to supercritical	Sintered bauxite, engineered oxides, additional materials possible upon request	Variety of salt chemistries including FLiNaK and NaCl-KCl-MgCl₂

Operating parameters and design attributes of heat exchangers supported for integration to the sCO₂, salt, and particle loops.

sCO2 Loop Specifications

The sCO₂ loop is instrumented for measuring temperature, pressure, differential pressure, density, and mass flow rates.

Aspect	Details
Pressure and Temperature	Measured in all piping segments and at: recuperator, heater, fill system, pump, heat exchanger
Pressure Change	Monitored across heat exchanger with differential and steady state pressure transducers
Temperature	Direct sCO₂ temperatures measured with RTDs inside piping/tubing; external surface temperatures with thermocouples (TCs)
Flow and Density	Two Coriolis flow meters at pump outlet: one for cold loop flow, one for hot loop and heat exchanger flow
Particle Loop	Two Coriolis flow meters at pump outlet: one for cold loop flow, one for hot loop and heat exchanger flow
Data Collection	Over 100 temperature points monitored and are adjustable per test; inlet/outlet temps of all major components collected; data monitored from control room; exportable to Excel and text files

Sandia’s 575°C sCO2 Loop
CAD Visualization

Particle Loop Specifications

The particle loop is designed for circulation of granular media or particles.

Carbo HSP 40/70 particles are standard in this loop, though many types and sizes are supported
60-kilowatt heater provides heat exchanger inlet temperatures up to 775 °C
Flow rates up to 250 grams per second
Slid-gate style valve on a linear actuator controls particle flow rate
Flow rates from 0 to 300 grams per second are supported
Steady state flow over long duration tests is most reliable from 50 and 250 grams per second
Skip hoist supports recirculation of particles due to higher operating temperature capabilities, and particle size and material flexibility

Particle skip hoist fill, lifting, and discharging positions. The skip hoist can be manually or automatically triggered to carry particles from the bottom of the particle loop to the heater at the top. Dwell time for discharging can be custom programmed by the user to accommodate different skip inventories and flow changes from particle sizes.

Instrumentation and Data Collection

sCO₂ Loop Instrumentation

Aspect	Details
Pressure and Temperature	Measures temperature, pressure, differential pressure, density, and mass flow rates. Measured in all piping segments and at: recuperator, heater, fill system, pump, heat exchanger
Pressure Change Monitoring	Across heat exchanger with differential and steady state pressure transducers
Temperature Measurement	Direct sCO₂ temperatures inside piping/tubing with RTDs; external surface temperatures with thermocouples (TCs)
Flow and Density Measurement	Two Coriolis flow meters at pump outlet: one for cold loop flow, one for hot loop and heat exchanger flow

Particle Loop Instrumentation

Aspect	Details
Instrumentation Components	Weigh hopper for particle flow rate measurement
Temperature Measurement	Thermocouples at heater, heater outlet, heat exchanger inlet, multiple points across heat exchanger, heat exchanger outlet, and weigh hopper

Data Collection

Aspect	Details
Temperature Monitoring	Over 100 temperature points monitored and are adjustable based on test requirements
Component Monitoring	Data monitored from adjacent control room; exportable to Excel spreadsheets and text files

Heat Exchanger Installation

Heat exchangers are typically mounted on support frames custom-built at Sandia and then integrated into the test stand. Sufficient length for the outlet hopper should be considered to meet flow requirements of a specific unit. Typical heat exchanger installations are 20 to 25 inches tall, with 15 to 20 inches for hoppers, though hoppers can be as short as a few inches tall, so long as the height accommodates desired flow requirements.

A 22-by-30-by-40-inch (length/depth/height) test area is available for heat exchanger prototypes, including the inlet and outlet hoppers.