Research & Technology Center


HTRI's Research & Technology Center (RTC) is a 22,500 ft2 multimillion-dollar research facility in Navasota, TX, USA. It includes eleven operating research units as well as support facilities and equipment. The RTC enhances our research capabilities by providing a controlled environment for testing. To learn more about our heat transfer testing services, contact us at

Research Units


Air-cooled Unit (ACU)


The ACU is an industrial-scale air cooler designed according to practical API 661 guidelines, with reconfigurable mechanical components. Incorporating two fan cells, this test unit also features a fixed tube bundle layout with the option of forced-draft or induced-draft plenums. To record airside measurements, a traverse system holds various anemometers and thermocouples, as well as static and total pressure sensors. Psychrometric and wind measurements are also recorded. 

Tubecount and fin density 162 extruded high-finned tubes and 393.7 fins/m (10 fins/in)
Tube diameter 25.4 mm (1 in)
Tube length 4.9 m (16 ft)
Tube bundle width 1.77 m (5.8 ft)
Tuberows 6
Tubepasses 2
Plenum depth 0.64 m (2 ft)
Fan diameter 1.5 m (5 ft)
Rated air volume flow 863.7 m3/min (30503 ACFM) per fan
Nominal duty 1.14 MW (3.9 MMBtu/hr)
Maximum temperature 95 °C (203 °F)
Maximum pressure 1138 kPa (165 psia)
Process volume flow (measurable range) 6.31 – 75.71 l/s (100 – 1200 gpm)

High Temperature Fouling Unit (HTFU-1)

Using two parallel test sections for a single fluid, the HTFU-1 provides thermal fouling and pressure drop data for hydrocarbon fluids (e.g., gas oils or crude oils) in any flow regime for any metallurgy. 

Maximum wall temperature 400 °C (750 °F)
Maximum bulk temperature 315 °C (600 °F)
Maximum pressure 6309 kPa (915 psia)
Power of each test section 2.3 kW (0.0078 MMBtu/hr)

Note: The maximum wall temperature is dependent on the operating conditions in use.


High Temperature Fouling Unit 2 (HTFU-2)


Similar to the HTFU-1, the HTFU-2 provides thermal fouling and pressure drop data for hydrocarbon fluids (e.g., gas oils or crude oils) in any flow regime for any metallurgy. The unit also has the capability to perform tests on up to four different test sections.

Maximum wall temperature 400 °C (750 °F)
Maximum bulk temperature 315 °C (600 °F)
Maximum pressure 4930 kPa (715 psia)
Power of each test section 2.3 kW (0.0078 MMBtu/hr)

Note: The maximum wall temperature is dependent on the operating conditions in use.


Rotating Fouling Unit (RFU)

The RFU provides screening results for crude oil fouling studies. It operates on minimal volume (3.8 L/1.0 gal) and has a heated probe with a spinning cup around the probe to induce flow. The unit has lower shear stress, resulting in shorter run times and faster fouling rates. These features make it ideal as a preliminary research tool.

Maximum wall temperature 400 °C (750 °F)
Maximum bulk temperature 260 °C (500 °F)
Maximum pressure 6309 kPa (915 psia)
Maximum stirring speed 1200 RPM (shear stresses up to 2 Pa)
Power of test section 600 W (2047 Btu/hr)

Note: The maximum wall temperature is dependent on the operating conditions in use.


Liquid-Liquid Heat Exchanger (LLHE)


The LLHE is primarily used to evaluate cooling equipment. This unit is the largest capacity rig in operation at HTRI in terms of flow rates and duty, and consists of cold and hot water sub-loops.

Loop Cold Water Hot Water
Maximum pressure 517.1 kPa (75 psia) 517.1kPa (75 psia)
Maximum temperature 51.7 °C (125 °F) 65.6 °C (150 °F)
Maximum flow rate 75.7 l/s (1200 gpm) 75.7 l/s (1200 gpm)

Low Pressure Condensation Unit (LPCU)


The LPCU collects heat transfer and pressure drop data of condensing and single-phase flows over a wide range of vacuum conditions. Hydrocarbons and refrigerants are used as test fluids. The unit features a low temperature chiller and can be configured for tubeside or shellside testing.

Temperature range -45.6 – 149 °C (-50 – 300 °F)
Pressure range 0.34 – 103.4 kPa (0.05 – 15.0 psia)
Flow rate range 0.00013 – 0.32 l/s (0.002 – 5.0 gpm)
Vapor quality at inlet 0 – 1.0

Multipurpose Boiling Unit (MBU)

The MBU measures heat transfer for different flow boiling regimes and boiling mechanisms, as well as pressure drop for various two-phase flow patterns. The unit can examine different geometries, including compact heat exchangers and enhanced tubes using pure fluids or hydrocarbon mixtures.

Bulk temperature range 15.6 – 204 °C (60 – 400 °F)
Pressure range 3.5 – 3447 kPa (0.5 – 500 psia)
Maximum flow rate 2.5 l/s (40 gpm)
Maximum heat flux 315 kW/m² (0.01 MMBtu/hr ft²)
Vapor quality at inlet 0 – 0.9

Multipurpose Condensation Unit (MCU)


The MCU tests pure components and hydrocarbon mixtures (with and without non-condensables) to measure condensation heat transfer and pressure drop performance of shell-and-tube and compact heat exchangers. Tests can cover a wide range of operating conditions, including vacuum and high pressure.

Temperature range 21 – 204 °C (70 – 400 °F)
Operating pressure range 3.4 – 2172 kPa (0.5 – 315 psia)
Maximum flow rate 0.63 l/s (10 gpm)
Vapor generator power 187 kW (0.638 MM Btu/hr)

Multipurpose Visualization Unit (MVU)

The MVU allows qualitative and quantitative flow visualization of two-phase air/water flows in process heat exchanger equipment. The unit's test section is a transparent shell-and-tube exchanger (TSTX) that can be easily reconfigured with different bundle layouts and baffle types, cuts, and spacings.

Temperature Ambient
Pressure range vented system 69 – 207 kPa (10 – 30 psia) in TSTX
Maximum flow rate (air) 0.047 standard m3/s (100 scfm)
Maximum flow rate (water) 6.3 l/s @ 18.3 m head (100 gpm @ 60 ft head)
Vapor quality at inlet 0 – 1.0
Pipe Flow Loop

The Pipe Flow and Serpentine Loops on the MVU enable the study of two-phase flow regimes in large diameter pipes. Both loops were constructed using transparent piping, allowing for flow visualization. The pipe flow loop facilitates research on upflow, horizontal flow, and downflow; the serpentine loop facilitates fired heater research.

Tube diameter 12.7 cm (5 in)
Temperature Ambient
Pressure range 34 – 241 kPa
(5 – 35 psia)
Maximum flow rate (air) 0.118 m3/s (250 cfm) 
Maximum flow rate (water) 31.5 l/s (500 gpm)

Prototype Test Unit (PTU)


The PTU is used to develop and validate thermal design methods for industrial-sized reboilers, condensers, or general purpose exchangers. The unit features a vertical separation tank with up to four prototype exchangers. Bundles or cores can be tested in boiling, condensing, single-phase vapor, or single-phase liquid service, with a variety of hydrocarbon-based fluids from viscous laminar up to turbulent service. The vertical separation tank facilitates testing of thermosiphon reboilers.

Maximum pressure 2861 kPa (415 psia)
Temperature range 21 – 204 °C (70 – 400 °F)
Pump capacity 11.04 l/s (175 gpm)

Tubeside Single-Phase Unit (TSPU)

The TSPU features two single-tube test sections: one where the tubeside fluid is heated and one where it is cooled. A progressive cavity pump is used to circulate the fluid, which can include high viscosity liquids, non-Newtonian fluids, and slurries. It is ideal for testing tube inserts.

Tube diameter 12.7 – 63.5 mm (0.5 – 2.5 in)
Maximum tube length 6.2 m (20 ft)
Flow regimes Deep laminar (Re < 1) to fully turbulent (Re > 150000)
Maximum fluid viscosity 30 kg/m.s (72573 lb/ft hr)
Maximum flow rate 0.63 l/s (10 gpm)
Fluid bulk temperature Ambient to 260 °C (500 °F)
Test section wall temperature 10 – 202 °C (50 – 395 °F)
Maximum pressure 2861 kPa (415 psia)

These research units can be customized to meet the changing needs of our customers. We are also available to conduct research and to construct new rigs under contract.

The facility′s physical plant includes a 500-hp Johnson Boiler with a heating capacity of 4980 kW (17 million Btu/hr) and a two-cell Marley cooling tower with a stainless steel basin and a cooling capacity of 6150 kW (21 million Btu/hr), two cooling tower pumps, two 50-hp (200 cfm) air compressors, a 500 cfm air dryer, and condensate return vessel and pumps.

The machine shop includes a milling machine, lathe, drill press, band saw, pipe threader, and welding equipment. Instrumentation testing is performed on site using various calibration devices. An onsite laboratory allows our technicians to perform various tests to ensure compliance with environmental regulations and to analyze fluids from the research units.

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