Dr. Perkins studies thermophysical and transport properties as a researcher in the Experimental Properties of Fluids Group of the Thermophysical Properties Division at NIST, Boulder. Dr. Perkins received his B.S. (1979) and Ph.D. (1983) in chemical and petroleum refining engineering from the Colorado School of Mines. He then worked for two years as a research associate in the Chemical Engineering Department at Rice University with Professor Riki Kobyashi before accepting a position as a chemical engineer at NIST, Boulder. He has done research on synthetic fuel properties, hydrates of natural gas, bio and process separations, and convection in porous media. His thesis work focused on the thermal conductivity of synthetic fuels from coal and included development of a unique transient-hot-wire apparatus that could be operated with either ramp-power or step-power heating. He currently studies the thermal conductivity and thermal diffusivity of gases, liquids and supercritical fluids with the NIST transient hot-wire apparatus at temperatures from 55 K to 750 K with pressures up to 70 MPa. Fluid system that have been studied include air, cryogenic fluids, alternative refrigerants, natural gas, aqueous mixtures, rocket propellants, turbine fuels, bio-fuels, and working fluids for power generation. He also works with Dr. Mark McLinden at NIST on measurements of the sound speed of gases, liquids and supercritical fluids with a spherical resonator apparatus and a dual-path pulse-echo apparatus. His fluid property work at NIST has also included work on vibrating-wire viscometers, a light scattering apparatus to measure thermal diffusivity, and isochoric calorimeters. In his research areas he has published over 90 research papers, including contributions to book volumes. He has worked on international round-robin studies and development of international consensus standards for viscosity and thermal conductivity.
Thermal conductivity work at NIST, Boulder began with steady-state parallel-plate measurements of the thermal conductivity of cryogenic helium and hydrogen at temperatures from 17 to 200 K (Hans Roder and Dwain Diller, 1970). Hans Roder began development of the cryogenic transient hot-wire apparatus at NIST in 1978. Dr. Perkins began development of a transient hot-wire apparatus at Colorado School of Mines in 1979 with Hans Roder on his thesis committee. Hans Roder began development on the second transient hot-wire apparatus for high temperatures in 1986 and Dr. Perkins joined the project in 1987. Today, the two apparatus have many hot-wire cells and offer unique capability to measure the thermal conductivity and thermal diffusivity of gases, liquids and supercritical fluids at temperatures from 55 K to 750 K with pressures up to 70 MPa. Recent work includes measurement and correlation of the thermal conductivity and thermal diffusivity of rocket propellants, turbine fuels, turbine lubricants, hydrogen, 4th generation alternative refrigerants/working fluids, bio-fuels, and high-temperature aqueous mixtures for advanced gas turbine design.
The transient hot-wire apparatus at NIST are absolute, requiring no calibration with a fluid of known thermal conductivity, and are constantly evolving to adapt to new fluid systems and to reduce uncertainty. Some important developments include: nulling improvements to allow thermal diffusivity determination, thermal radiation analysis for absorbing-emitting fluids, pre-polarization to reduce errors with polar fluids, electrically insulated hot wires (anodized tantalum) for conducting fluids, steady-state hot-wire capability for dilute gases, and AC drive/phase-sensitive measurement (1-30 kHz) for polar/weakly conducting fluids.
Dr. Perkins is active in the development of reference data standards for fluids such as toluene and water to allow reliable calibration and verification of thermal conductivity apparatus. He is also active in the development of international consensus standards for the viscosity and thermal conductivity of key industrial fluids such as water and D2O (IAPWS), carbon dioxide and hydrogen.
Dr. Perkins has long been interested in calorimetry, beginning with his post-doctoral studies when he developed a heat-flux type differential scanning calorimeter for high-pressure studies of natural-gas hydrates. He has worked with Dr. Joseph Magee at NIST on constant-volume adiabatic calorimeters to measure triple points, heats of fusion, densities, vapor pressure, and two-phase and isochoric specific heats of refrigerants and natural-gas components. These properties are used during development of accurate multi-properties equations of state.
The sound speeds of both the liquid and gas are also valuable for the development of accurate multi-property equations of state. Dr. Perkins is working with Dr. Mark McLinden on apparatus to measure the speed of sound of gases with the spherical resonator technique and liquids with the dual-path pulse-echo technique.
The spherical resonator apparatus determines the speed of sound of gases at temperatures from 280 K to 500 K with pressures up to 10 MPa. This resonator has been used for determination of the sound speed and ideal-gas specific heat of potential working fluids for organic Rankine cycles, fourth generation refrigerants and mixtures of argon with carbon dioxide. The dual-path pulse-echo sound speed apparatus determines the speed of sound of liquids at temperatures from 228 K to 423 K with pressures up to 90 MPa. The dual-path pulse-echo apparatus has been used to determine the speed of sound of fuels and fuel components, alternative refrigerants and lubricants.
For developing state-of-the-art techniques for measuring the thermal conductivity of highly-polar and electrically conducting fluids