Allan Kirkpatrick

Centreline velocity decay measurements in low-velocity axisymmetric jets

The streamwise velocity profiles of low-velocity isothermal axisymmetric jets from nozzles of different diameters were measured and compared with previous experimental data. The objective of the measurements was to examine the dependence of the diffusion of the jet on the outlet conditions. As the outlet velocity was decreased, the centreline velocity decay coefficient began to decrease at an outlet velocity of about 6 m s −1 .

An experimental investigation of mixed cavity natural convection in the high Rayleigh number regime

Abstract Using four different configurations of differentially heated and cooled vertical and horizontal surfaces in a cubical enclosure, natural convection experiments at high Rayleigh numbers were conducted. All of the experiments were variations of the heating-from-below case. Experimental measurements and observations were made of the heat transfer, flow patterns, and the mean and fluctuating temperature distribution. The results indicated that the heated floor promoted mixing in the enclosure and reduced the thermal stratification. For the boundary conditions of the experiment, the heat transfer from the horizontal surfaces was not strongly affected by the presence of a horizontal temperature gradient.

Characteristic and Computational Fluid Dynamics Modeling of High-Pressure Gas Jet Injection

The topic of this paper is the computational modeling of the gas injection process in a large-bore natural gas fueled engine. At high injection pressures, the overall gas injection and mixing process includes compressible flow features such as rarefaction waves and shock formation. The injection geometries examined in the paper include both a two-dimensional slot and an axisymmetric nozzle. The computations examine the effect of the supply pressure/cylinder stagnation pressure ratio, with ratios ranging from 3 to 80, on the velocity and pressure profiles in the near field region. Computational fluid dynamics modeling was compared with results obtained from a two-dimensional analytical method of characteristics solution and experimental results. The comparison process evaluated factors such as pressure and Mach number profiles, jet boundary shape, and shock location.

High Rayleigh number natural convection in partially divided air and water filled enclosures

Abstract This paper describes an experimental study aimed at determining the effect of internal partitions on the natural convection heat transfer across an enclosure. Experiments are conducted using a representative cubic geometry differentially heated from the side with an internal partial vertical partition. Two test cells with different working fluids are used, an air (Pr∼-0.7) and a water (Pr∼-0.6) cell. Nusselt-Rayleigh-aperture width correlation curves are developed for both the air and the water data using a resistance model. For a constant Rayleigh number, as the aperture width is decreased, the flow field undergoes a transition from a boundary layer regime to a blocked flow bulk density driven regime.

Ground-Coupled Heat and Moisture Transfer from Buildings Part 1–Analysis and Modeling*

Ground-heat transfer is tightly coupled with soil-moisture transfer. The coupling is threefold: heat is transferred by thermal conduction and by moisture transfer; the thermal properties of soil are strong functions of the moisture content; and moisture phase change includes latent heat effects and changes in thermal and hydraulic properties. A heat and moisture transfer model was developed to study the ground-coupled heat and moisture transfer from buildings. The model also includes detailed considerations of the atmospheric boundary conditions, including precipitation. Solutions for the soil temperature distribution are obtained using a finite element procedure. The model compared well with the seasonal variation of measured ground temperatures.

Ground-Coupled Heat and Moisture Transfer from Buildings Part 2–Application

In this paper the effects of moisture on the heat transfer from two basic types of building foundations, a slab-on-grade and a basement, are examined. A two-dimensional finite element heat and moisture transfer program is used to show the effects of precipitation, soil type, foundation insulation, water table depth, and freezing on the heat transfer from the building foundation. Comparisons are made with a simple heat conduction model to illustrate the dependency of the soil thermal conductivity on moisture content.

Stable Cu-Based Back Contacts for CdTe Thin Film Photovoltaic Devices

Cadmium telluride (CdTe) thin film photovoltaic devices fabricated in a-line process developed at Colorado State University (CSU) have shown stability during long-term (over a 5 year period) accelerated stress testing. These devices have a copper (Cu) containing back contact. The Cu profile as measured by secondary ion mass spectrometry characterization shows, for the maximum stressed device (23,399 h), that there is a significant (two times) change in the concentration of secondary Cu ions in the bulk of the material; however, the Cu concentration gradient at the back of the device has no significant change, and the CdS layer has no significant Cu concentration increase at open-circuit bias and 65°C temperature conditions. This indicates that with a proper CdCl 2 treatment, Cu can be used to form the back contact for CdTe devices with acceptable stability. These devices have a projected field lifetime of greater than 60 years.

Spectral Analysis of the Effective Temperature in Passive Solar Buildings

The effective temperature, a linear combination of a buildings enclosure temperature, mean radiant temperature, and the ambient temperature, is a measure of the thermal comfort inside a building. Results from an analytical study of the relationship between the effective temperature, glazing areas, and thermal energy storage in passive solar buildings are presented in this paper. Spectral analysis is used to find the effective temperature response of a mixed-direct and indirect-gain passive solar building to Typical Meteorological Year (TMY) weather data. The response is given by the complex product of the building transfer functions and the weather inputs. Results are presented for the sensitivities of the maximum, minimum, and average daily effective temperature to changes in the direct and indirect gain glazing area and thermal energy storage.

ASME vision 2030: Helping to inform mechanical engineering education

In July 2008, the ASME Center for Education formed an engineering education task force, subsequently entitled ASME Vision 2030. The committee was composed of representatives from industry and education, including both engineering and engineering technology educators. This paper provides a summary of the extensive survey effort undertaken by ASME to gather input from industry (both supervisors and early career engineers) and academia about the strengths and weaknesses of mechanical engineering graduates. The number of survey respondents totals almost 3000. This paper summarizes data highlights and relevant issues revealed by them. Of special interest to educators are the areas where the academic view is either contradictory to, or aligned with, the view of industry practitioners. In addition, the professional development needs of early career engineers provide insight into improvements needed in both current curricula and post graduate educational offerings. The salient points stemming from these data also apply to engineering disciplines beyond mechanical engineering.

Influence of Aperture Height and Width on Interzonal Natural Convection in a Full-Scale Air-Filled Enclosure

The topic of this paper is the influence of aperture height and width on interzonal high Rayleigh number, natural convection heat transfer. Experiments were conducted in an 8 ft. air-filled cube divided into two zones by a vertical partition which was centered between a constant flux hot wall and an isothermal cold wall. The partition was configured to form doorway-like apertures. The aperture height relative to test cell height range from 1/8 to 1 and the aperture width relative to test cell width ranged from 0.009 to 1. The zone-to-zone temperature difference and the overall Nusselt number were determined experimentally, and correlated with the overall Rayleigh number, aperture, and enclosure geometry, using a series resistance model for the enclosure. A turbulent boundary layer resistance was used to represent the hot and cold boundary layer flow, while an orifice resistance was used to represent the aperture flow. For flux Rayleigh numbers between 5*1011 and 5*1012 , the enclosure Nusselt numbers ranged between 15 and 165, with a strong dependence on aperture height.