Research & Technology Center | HTRI


The HTRI Research & Technology Center (RTC) is a 22,500 ft2 multimillion-dollar research facility in Navasota, TX, USA. It includes eleven operating research units, 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 Air-Cooled Unit is designed according to practical API 661 guidelines with reconfigurable mechanical components. The unit features options for forced- or induced-draft orientation, chimneys, removable tube bundle air seals, louvers, and box or shaped plenums. 

Tube count and fin density 162 high-finned tubes and 393.7 fins/m (10 fins/in)
Tube OD 25.4 mm (1 in.)
Tube length 4.9 m (16 ft)
Tube bundle width 1.77 m (5.8 ft)
Tuberows / tubepasses 6 / 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)
Maximum duty 1.14 MW (3.9 MMBtu/hr)
Maximum process temperature 95 °C (203 °F)
Maximum process pressure 1034 kPa (150 psig)
Process volume flow (measurable range) 6.31 – 75.71 l/s (100 – 1200 gpm)

High Temperature Fouling Unit 1 (HTFU-1)

Using two parallel test sections for a single fluid, the High Temperature Fouling Unit provides thermal fouling data for fluids such as gas oils or crude oils in any flow regime for any metallurgy. 

Maximum surface temperature 482 °C (900 °F)
Maximum bulk temperature 315 °C (600 °F)
Maximum operating pressure 6895 kPa (1000 psia)
Maximum flow rate 2.5 p/s (40 gpm)
Power of each test section 2.3 kW (7848 Btu/hr)

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


High Temperature Fouling Unit 2 (HTFU-2)


To meet the increasing demand for crude oil fouling studies, a second high temperature fouling unit has been constructed. The unit can recirculate a fouling test fluid through up to six different test sections at various wall temperatures and velocities.

Maximum surface temperature 482 °C (900 °F)
Maximum bulk temperature 340 °C (644 °F)
Maximum operating pressure 6895 kPa (1000 psia)
Maximum flow rate 2.5 l/s (40 gpm)
Power of each test section 2.3 kW (7848 Btu/hr)

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


Rotating Fouling Unit (RFU)

The Rotating Fouling Unit provides screening results for crude oil fouling studies. It operates on 3.8 L of crude 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 surface temperature 482 °C (900 °F)
Maximum bulk temperature 260 °C (500 °F)
Maximum operating pressure 6895 kPa (1000 psia)
Maximum stirring speed 1000 RPM (1.5 Pa of shear stress)
Maximum power of probe 600 W (2047 Btu/hr)

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


Liquid-Liquid Heat Exchanger Test Unit (LLHETU)


The Liquid-Liquid Heat Exchanger Test Unit is primarily used to evaluate cooling equipment. HTRI has passed a rigorous set of audits and certification tests by The Air Conditioning, Heating, and Refrigeration Institute (AHRI) and is now qualified to conduct tests meeting its Standard 400 and Certification Operations Manual.

The Liquid-Liquid Heat Exchanger Test Unit is the largest capacity rig in operation at HTRI in terms of flow rates and duty, and consists of two sub-loops: the Cold Water Loop and the Hot Water Loop.

Loop Cold Water Hot Water
Maximum operating pressure 517.1 kPA (75 psia) 517.1kPa (75 psia)
Maximum operating 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 Low Pressure Condensation Unit collects experimental data on heat transfer, mass transfer, and pressure drop 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)
Operating pressure range 0.34 – 103.4 kPa (0.05 – 15.0 psia)
Flow rate 0.00013 – 0.32 l/s (0.002 – 5.0 gpm)
Vapor quality at inlet 0 – 1.0

Multipurpose Boiling Unit (MBU)

The Multipurpose Boiling Unit 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)
Operating 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 (100000 Btu/hr ft²)
Vapor quality at inlet 0 – 0.9

Multipurpose Condensation Unit (MCU)


The Multipurpose Condensation Unit tests pure components and hydrocarbon mixtures (with and without non-condensables) to measure condensation heat transfer and pressure drop performance for shell-and-tube and compact heat exchangers. Tests can cover a wide range of operating conditions, including vacuum and high pressure. This unit has been modified over years of study to maximize its effectiveness.

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

Temperature range Ambient
Operating 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 0.0063 m3/s @ 18.3 m head (100 gpm @ 60 ft head)
Vapor quality at inlet 0 – 1.0
Pipe Flow Loop

The Pipe Flow Loop was added to the Multipurpose Visualization Unit to study two-phase flow regimes in large diameter piping in upflow, horizontal flow, and downflow. It is constructed of 5-in. diameter transparent piping.

Operating temperature Ambient
Operating pressure range -10 psig – 20 psig
-69 kPa – 138 kPa
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 Prototype Test Unit 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 operating pressure 2861 kPa (415 psia)
Design temperature 21 – 204 °C (70 – 400 °F)
Pump capacity 11.04 l/s (175 gpm)

Tubeside Single-Phase Unit (TSPU)

The Tubeside Single-Phase Unit 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 test 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 – 260 °C (500 °F)
Test section wall temperature 10 – 202 °C (50 - 395 °F)
Maximum system operating pressure 2861 kPa (415 psia)

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

The facility′s physical plant includes a 500-horsepower 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 equipment 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 tests ensuring compliance with environmental regulations and to analyze fluids from the research units.

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