About
54
Publications
3,738
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Introduction
Current institution
Additional affiliations
July 2011 - June 2018
Position
- Professor
Description
- Faculty member in the Mechanical Engineering Technology program.
July 2000 - June 2011
Position
- Professor (Associate)
Description
- Faculty member in the Mechanical Engineering Technology program and General Engineering.
August 1997 - June 2020
Conoco Inc
Position
- Senior Researcher
Description
- Worked with geophysicists to characterize heterogeneous reservoirs containing oil and natural gas.
Education
September 1977 - December 1981
August 1975 - December 1976
August 1971 - May 1975
Publications
Publications (54)
Distributed thermal response tests (DTRTs) on vertical boreholes estimate design parameters, which are used in the coupling of these boreholes to heat pumps. A semi-analytical model of a DTRT has been developed that includes multiple ground layers and the geothermal gradient for deep boreholes. The model is computationally efficient, which allows q...
This paper concerns the modeling of vertical Borehole Heat Exchangers (BHEs) for Ground Source Heat Pump (GSHP) applications. Focus is devoted to the analyses of Thermal Response Test (TRT) simulations aimed at understanding the main factors that influence the ground thermal conductivity and the effective borehole thermal resistance estimations. Th...
Thermal response tests (TRT) are performed on borehole heat exchangers to estimate design properties needed when the boreholes are coupled to heat pumps. In conventional TRTs the heat injection or extraction rate from an external heater or heat pump is controlled to be nearly constant. More recently some investigators have conducted TRTs while cont...
Ground source heat pumps are often coupled with vertical boreholes in order to heat and cool buildings. As the maximum depth of boreholes has increased, the ranges of undisturbed ground temperature and ground thermal conductivity tend to be wider and more important to consider. These larger variations may affect the analysis of a thermal response t...
A thermal response test (TRT) on a borehole evaluates ground and borehole properties, which are needed in the design of borehole fields for ground source heat pump systems. Variation in the heat input rate during a TRT complicates the data analysis, when the electrical power to the test equipment is unintentionally interrupted, or other unwanted ch...
Vertical borehole heat exchangers are often coupled to heat pumps to transfer heat between the ground and the inside of a building. A transient heat transfer model has been developed for a coaxial borehole while taking into account the geothermal gradient found in deep boreholes. The analytical solution is obtained by applying Laplace transform met...
Thermal response tests (TRT) are performed on borehole heat exchangers in order to evaluate ground and borehole thermal properties, which are needed in the design of ground source heat pump systems. When parameter estimation techniques are applied to evaluate the ground thermal conductivity and borehole thermal resistance, the map of the root-mean-...
A recently developed vertical borehole ground heat exchanger model that accounts for transit time effects and time-varying short-circuiting heat transfer has been validated against two multi-flow-rate thermal response tests (MFR-TRT). The MFR-TRT, when performed with a wide range of flow rates, results in significant changes in the borehole thermal...
Thermal response tests (TRTs) are often performed on vertical borehole heat exchangers, which are used in ground-source heat pump systems. Conventional analysis methods for TRTs provide estimates of the ground thermal conductivity and the effective borehole resistance. Both parameters are required in the design of GSHP systems. A parameter estimati...
Vertical borehole heat exchangers are used to couple heat pumps to the ground, which serves as a source or sink of heat. These ground source heat pump systems heat and cool buildings efficiently with low maintenance costs. Many heat transfer models use the mean of the inlet and outlet circulating fluid temperatures as an average temperature along t...
Frost injury patterns are commonly observed on the warm-season turfgrass species bermudagrass (Cynodon species Rich.), zoysiagrass (Zoysia species Willd.), and buffalograss [Bouteloua dactyloides (Nutt.) J.T. Columbus] in cool-temperate and subtropical zones. Qualitative observations of these injury patterns are presented and discussed. A model for...
Ground source heat pump systems use boreholes to exchange heat with the ground. The thermal performances of ten horizontal boreholes have been evaluated by performing in-situ thermal response tests (TRT) on each borehole. The tests determine both ground thermal conductivity and borehole resistance. Ground thermal conductivity depends on moisture co...
Ground-source heat pumps often use vertical boreholes to exchange heat with the ground. A transient heat transfer model has been developed for a thermal response test on a pipe-in-pipe coaxial borehole heat exchanger. The analytical model calculates the vertical temperature profiles in the fluid flowing through the pipes, which are coupled to the s...
This paper describes field tests on ten different vertical-bore ground heat exchangers (GHXs). The field tests consist of both short-term thermal response tests on the boreholes and full-year performance measurements on the associated ground source heat pump (GSHP) systems. While providing space conditioning to nearly identical homes, the energy co...
A transient heat transfer model has been development for a thermal response test (TRT) on a vertical borehole with a U-tube. Vertical borehole heat exchangers are frequently coupled to ground source heat pumps, which heat and cool buildings. The model provides an analytical solution for the vertical temperature profiles of the circulating fluid thr...
Ground source heat pump systems are often coupled to the ground by circulating a fluid through vertical Borehole Heat Exchangers (BHEs). The design of a system requires estimates of the ground thermal conductivity and the borehole thermal resistance, which are usually determined by an in situ thermal response test on a completed borehole. The usual...
The design of ground source heat pump systems requires values for the ground thermal conductivity and the borehole thermal resistance. In situ thermal response tests (TRT) are often performed on vertical boreholes to determine these parameters. Most TRT analysis methods apply the mean of the inlet and outlet temperatures of the circulating fluid al...
The design of a ground source heat pump system requires accurate knowledge of properties, such as ground thermal conductivity and borehole thermal resistance. These properties are often determined using an in-situ thermal response test of a pilot borehole. These tests are sometimes interrupted by unexpected circumstances and occasionally a retest i...
Ground source heat pump systems often use closed-loop heat exchangers, which depend on the soil thermal conductivity and borehole thermal resistance as parameters. An in-situ thermal response test provides a method to estimate these two parameters. In analyzing the in-situ test, one commonly uses the mean of the measured inlet and outlet temperatur...
Ground source heat pump systems often use vertical boreholes to exchange heat with the ground. Two areas of active research are the development of models to predict the thermal performance of vertical boreholes and improved procedures for analysis of in situ thermal conductivity tests, commonly known as thermal response tests (TRT). Both the models...
This paper describes an instructive laboratory exercise for undergraduate students studying mechanical measurements and instrumentation. The experimental setup uses a pressure transducer, rubber tubing and a balloon to study the dynamic response of the
assembled system as the balloon is punctured. The experiment demonstrates how the length of the t...
Geothermal heat pumps exchange heat with the ground through the use of ground heat exchangers where the heat transfer rate depends on the thermal conductivity of the surrounding soil. An in-situ test is often performed on a vertical borehole to estimate soil thermal conductivity, but the test must have sufficient duration in order to obtain an accu...
Thermal tests are often performed on vertical boreholes for ground-source heat pump systems, which heat and cool buildings. These in-situ tests estimate soil thermal conductivity, which is an important parameter in the design of these systems. If an electrical power loss or other equipment failure interrupts the test, the interruption greatly compl...
The design of a geothermal heat pump system requires an estimate of soil thermal conductivity. An in-situ test on a bore-hole provides such an estimate, along with an estimate of the borehole resistance. Sometimes electrical power interruptions, running out of fuel, or other equipment problems temporarily disrupt the test and greatly complicate the...
Local estimates of amplitude, frequency, and phase have been used in the past to characterize seismic data. In particular, these attributes have sometimes been successfully related to well attributes at the reservoir scale (net pay thickness, sand fraction, etc.). This paper introduces a method called SINFIT for computing local amplitude, frequency...
An in-situ test on a borehole provides a way to estimate soil properties, which are needed to design geothermal heat pump systems. Having sufficient testing time becomes an issue in planning, performing, and interpreting the test. This paper develops a quick method to calculate the minimum testing time necessary to estimate soil thermal conductivit...
fn-situ tests to determine soil thermal conductivity and borehole resistance are often difficult to interpret due to variability in the heat rate during the test. This paper demonstrates that simply smoothing out fluctuations in temperature data will not remove the distortions caused by variable rates. Instead, an algorithm is developed to properly...
Geothermal heat pump systems exchange heat with the ground, often through a vertical, U-tube, ground heat exchanger. The performance of this U-tube heat exchanger depends on the thermal properties of the soil, as well as grout or backfill in the borehole. In-situ tests provide a means of estimating some of these properties, but the routine analysis...
Geostatistics has become a popular way to distribute reservoir properties between wells. One of the geostatistical methods being used is fractal geostatistics. Most porosity well logs have been found to have a fractal character. An analysis of vertical and horizontal logs, core photos, and outcrop photos has led to a rather simple model to describe...
Fractal geostatistics can be used to generate distributions of such reservoir properties as porosity and permeability. We compare three different methods that use these distributions in reservoir simulations. The first method is a hybrid finite-difference/stream-tube method that starts with 2D vertical cross sections with relatively fine grids, the...
In many cases, field pressure transient data are matched with homogeneous reservoir models to get effective reservoir properties, even though log and core data show the subject reservoir is heterogeneous. This paper presents field data and a model that demonstrate the above approach does not always work. A pressure transient model is developed for...
Fractal distributions of porosity and permeability in two-dimensional vertical cross sections can be used to represent reservoir heterogeneity. We compare a hybrid finite-difference/streamtube method and pseudorelative permeabilities as two methods of using these distributions in reservoir simulations. We simulate waterflood displacements in a fiel...
Conventional pressure transient models strictly apply to areally homogeneous reservoirs. Yet, core and log data indicate this assumption is often not justified. This paper describes a model for heterogeneous reservoirs and supporting field data from the Grayburg/ San Andres formations in southeastern New Mexico. Conventional models fail to match th...
Conventional pressure transient models stricly apply to areally homogeneous reservoirs. Yet, core and log data indicate this assumption is often not justified. This paper describes a model for heterogeneous reservoirs and supporting field data from the Grayburg/San Andres formations in southeastern New Mexico. Conventional models fail to match thes...
A tracer program to identify channels within the Grayburg/San Andres formations prior to CO2 injection has been performed and analyzed at the Maljamar Cooperative Agreement (MCA) Unit. For safety and costs reasons two separate interwell tracer surveys or phases were conducted. In the Phase 1 tests tritium was injected into 62 wells through injectio...
Classical studies of boundary layer diffusion flames have neglected radiation. As a first step toward a better understanding of radiation heat transfer in fires, a numerical solution is obtained for a steady, laminar, radiating, combusting, boundary layer over a pyrolyzing fuel slab. Two Shvab-Zeldovich coupling functions are needed in the analyses...
The accuracy of six numerical approximations of the convection terms in
the conservation equations is examined for a steady, recirculating flow.
Quadratic upwind, central, nine-point, third-order, and power-law
approximations are tested as alternatives to the widely used
upwind/central hybrid method. Forced flow in a heated cavity is chosen
as a re...
The accuracy of six numerical approximations of the convection terms in the conservation equations is examined for a steady, recirculating flow. Quadratic upwind, central, nine-point, third-order, and power-law approximations are tested as alternatives to the widely used upwind I central hybrid method. Forced flow in a heated cavity is chosen as a...
A multiwavelength laser transmission technique is used to determine soot volume fraction fields and approximate particle size distributions in a forced flow combusting boundary layer. Measurements are made in diffusion flames of polymethylmethacrylate (PMMA) and five liquid hydrocarbon fuels (n-heptane, iso-octane, cyclohexane, cyclohexene, and tol...
The Opposed Flow Diffusion Flame (OFDF) apparatus has been used for estimating the thermochemical properties of materials related to fire safety and for diffusion flame structure studies. The extension of the flame beyond the pyrolyzing fuel surface and the excess pyrolyzate are predicted. Since flame and stagnant plane locations may be sensitive t...
Carbon particulate volume fraction profiles and approximate particle size distributions are measured in a free laminar combusting boundary layer for several liquid hydrocarbon fuels and PMMA (polymethylmethacrylate). A multi-wavelength laser transmission technique determines a most probable particle radius and total particle concentration., which a...
The purpose of the work reported was to develop a load calculation method for design of air-conditioning systems utilizing temperature stratification principles. The calculational method was also intended to provide sufficient detail on load distribution to allow analysis and explanation of the load reduction occurring in stratified systems. A phys...
The assets that Citizen Potawatomi Nation holds were evaluated to help define the strengths and weaknesses to be used in pursuing economic prosperity. With this baseline assessment, a Planning Team will create a vision for the tribe to integrate into long-term energy and business strategies. Identification of energy efficiency devices, systems and...
A comprehensive analysis of the TMI-2 hydrogen deflagration is descibed encompassing hydrogen generation/release rates, hydrogen mixing prior to the burn, likely ignition sources, combustion and cool-down phenomena, and burn-induced mechanical and thermal damage. The analysis independently leads to conclusions that agree in most aspects with those...
