Mechanical and Mechatronics Engineering

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This is the collection for the University of Waterloo's Department of Mechanical and Mechatronics Engineering.

Research outputs are organized by type (eg. Master Thesis, Article, Conference Paper).

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Now showing 1 - 20 of 1542

A Novel Furnace Design Utilizing a Low Temperature Plastic Condensing Heat Exchanger
(1982-03) Wright, John L.; Sullivan, Harry F.
The initial phase of a research and development program for the Consumers' Gas Co. and the Federal Department of Energy, Mines and Resources to design a condensing heat exchanger/gas fired residential air furnace has been completed. Progress to date has resulted in a novel design utilizing a relatively low temperature plastic material for the last stage heat exchanger. To utilize this low temperature plastic, a method of reducing the temperature of the flue gas entering the final heat exchanger was devised using a unique flue gas recirculation process. Heat transfer calculations and pressure drop prediction methods have indicated that the design is sound and can easily be accommodated in a residential furnace with only moderate increase in cost and space requirements. The existing design is also well suited to incorporation as a retrofit package and this is also being pursued. Based on the calculated performance, a condensing heat exchanger was sized, fabricated and installed on a conventional 80,000 BTU/hr input gas fired residential furnace. The initial experimental tests have given very encouraging results. Based on a final flue gas exit temperature of 85F with an excess air condition of 25%, these initial tests yielded a furnace efficiency of approximately 97%. Although combustion air preheat has not been employed in these initial tests, this feature is planned as part of the prototype design.
Effective U-values and Shading Coefficients of Preheat/Supply Air Glazing Systems
(1986-06) Wright, John L.
Research is documented which makes use of a computer program called VISION, This computer program was developed specifically to provide a detailed analysis of heat transfer occurring in glazing systems. VISION was modified to perform an analysis of the energy flows in supply air windows. A model used to quantify heat transfer in the supply air flow is described. Ventilation air is brought in through supply air windows and the energy recovered by the preheat of the air flow is credited to the thermal performance of the window itself, Thus, the net energy flow between the conditioned space and the window was used to calculate an effective U-value and shading coefficient, The use of these "effective" window performance parameters permits the subsequent quantification of energy flows to or from the supply air glazing system without the necessity of modelling the detailed mechanisms of energy transport within the glazing system itself. A variety of glazing system designs are simulated. Indoor glazing temperature is reported for each system. In all cases the presence of preheat ventilation improved the effective shading coefficient moderately and increased the effective thermal resistance appreciably.
Simulation and Measurement of Windows with Low Emissivity Coatings Used in Conjunction with Teflon Inner Glazings
(1987-09) Wright, John L.; Sullivan, Harry F.
Theoretical work has illustrated that highly infrared, transparent plastic films are well suited for use as intermediate glazings when used in conjunction with a low emissivity coating. Prototype glazing systems that incorporate low emissivity coatings and Teflon films were constructed. The thermal resistance of each of these prototypes was measured using the University of Waterloo Natural Convection Apparatus. Simulation of the glazing systems was carried out using a two-band glazing system thermal analysis program called VISION. Comparison between measurement and simulation showed good agreement. It can be concluded that highly infrared transparent intermediate glazings can be useful when high thermal resistance is desired and that the VISION glazing system analysis program is useful not only for parametric and sensitivity investigations but can also be used with confidence to estimate U-values of specific glazing systems.
Simulation And Measurement Of Windows With Metal Films Used In Conjunction With Teflon Inner Glazings
(1987-09) Wright, John L.; Sullivan, Harry F.
Previous work has shown that highly infrared transparent plastic films are well suited for use as inner glazings when used in conjunction with a low emissivity coating. Thermal resistance measurements of a set of glazing systems incorporating gold or copper coatings plus Teflon intermediate glazings are reported. The same glazing systems were simulated using a computer program called VISION. The agreement between the two sets of results was found to be very good.
Glazing System U-Value Measurement Using a Guarded Heater Plate Apparatus
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1988) Wright, John L.; Sullivan, Harry F.
Precise heat transfer measurements have been carried out during the last 20 years using a guarded heater plate apparatus. This apparatus has been adapted and used over the last several years to perform U-value measurements on a variety of prototypical glazing systems. Results from two sets of measurements are presented. One set of results quantifies heat transfer across stagnant air layers containing an intermediate fluorinated ethylene-propylene (FEP) glazing and bounded by plates of various emissivities. The second set consists of values (i.e., glass-to-glass U-values) for a set of glazing systems that incorporate up to four glazings, one of two solar-control metal coatings and up to two intermediate glazings made of FEP film. In each case the measured results are compared to simulation. In the first study the discrepancy between measured and calculated heat transfer rates was less than 2% in all cases. In the second study the discrepancy was never greater than 8% and was less than 3% in the majority of cases. These results indicate that the test method used is well suited to the reliable measurement of glazing system U-value. It is a useful tool as a developmental test procedure for glazing system design because it can be carried out quickly and at low cost. The apparatus and procedure are described in detail.
Thermal resistance measurement of glazing system edge-seals and seal materials using a guarded heater plate apparatus
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1989) Wright, John L.; Sullivan, Harry F.
In cold climates the increased edge-glass heat transfer at the perimeter of a sealed glazing unit creates a special problem. This is where condensed water and frost most readily occur. One mechanism contributing to edge-glass heat transfer is edge-seal conduction. Very few data are available regarding the thermal resistance of the various edge-seal configurations that are commercially available. An experimental procedure has been devised whereby the thermal resistance of an edge-seal can be directly measured using a guarded heater plate apparatus. Results are reported for nine edge-seal test samples. In addition, results from similar tests provide measured thermal conductivities for four of the materials used in the construction of the edge-seal test samples and commercially available edge-seals.
Natural Convection in Sealed Glazing Units: A Review
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1989) Wright, John L.; Sullivan, Harry F.
In cold climates the augmented edge-glass heat transfer at the bottom of a glazing system creates a special problem. This is where condensed water and/or frost most readily occur. Two mechanisms determining the rate of edge-glass heat transfer, namely, edge-seal conduction and fill gas convection, are discussed. Current methods for estimating average edge-glass heat loss rates are reviewed. No reliable methods have been established for calculating the minimum temperature near the bottom of the indoor glazing. Heat transfer by natural convection of a gas in a vertical slot is a highly complex process about which there exists an abundance of technical information. The literature reviewed describes laminar flow regimes, mechanisms of heat transfer, local heat transfer, hydrodynamic stability, and conditions governing the onset of turbulence. These findings are discussed as they pertain to total and local heat transfer rates in glazing systems.
A Study Of Pane Spacing In Glazing Systems
(Solar Energy Society of Canada, 1989-06) Wright, John L.; Baker, J. A.; Sullivan, Harry F.
The selection of optimum pane spacing for glazing systems has been a topic of ongoing debate in the window manufacturing industry. Arguments are often based on speculation, intuition and results from tests not specifically designed to examine the effects of pane spacing. This study presents a set of measured centre-glass U-values taken from experiments where pane spacing was carefully varied while holding all remaining conditions unchanged. Heat flux measurements were made using a guarded heater plate apparatus. Glazing systems were all double glazed, air filled and tested in the vertical position. Measured centre-glass U-values were compared to calculated U-values. These calculations were performed using a version of the VISION glazing system thermal analysis program which was modified in order to model the guarded heater plate test conditions. VISION runs were also carried out in order to predict the optimum pane spacing as a function of variations in glazing system design, fill gas type, weather condition, and the number of panes incorporated in the glazing system. VISION results were combined with results of the window frame thermal analysis program, FRAME. FRAME was used to estimate the average edge-glass and frame U-values for several design options. The results of these calculations provide an estimate of the sensitivity of overall U-values to variations in pane spacing.
Thermal Resistance Measurement Of Glazing System Edge-seals
(1989-11) Wright, John L.
The existing design of glazing system edge-seals creates increased edge-glass heat transfer at the perimeter of sealed glazing units. This thermal short-circuit caused by edge-seal conduction results in added mechanical stress. condensation problems in cold climates and augments the building energy load. New edge-seal designs are being marketed but very few data are available regarding the thermal resistance of any of the various edge-seal configurations that are available. An experimental procedure hos been devised whereby the thermal resistance of an edge-seal can be directly measured using a guarded heater plate apparatus. Results for nine edge-seal test samples are reported and discussed. A variety of conclusions and design guidelines are presented.
A two-dimensional numerical model for natural convection in a vertical, rectangular window cavity
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1994-12-31) Wright, John L.; Sullivan, Harry F.
It is common for sealed glazing units to exhibit condensation problems when operated in cold climates. Condensation often forms along the perimeter of the exposed surface of the indoor glazing because of the thermal short circuit caused by the edge seal. Furthermore, condensation most readily forms along the bottom edge of the indoor glazing because of the combined effects of edge seal conduction and fill gas convection. A simple two-dimensional numerical control volume formulation is presented that can be used to model the natural convection of gas within a vertical, rectangular cavity. Details of a unique perturbation scheme used to generate secondary cells are also presented This model closely reproduces the average Nusselt number results of more complex numerical models. Average and local Nusselt numbers have also been compared with experimental results and close agreement has been demonstrated for conditions typical of window cavities.
Calculating Window Solar Heat Gain
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1995-07) Wright, John L.
Window design has been revolutionized-largely by the introduction of low emissivity (low-e) coatings and substitute fill gases. The large number of design options necessitates the use of computer simulation for development and rating. Two window analysis programs, VISION1 and WINDOW,2 are widely used in North America. Both have been released in several versions-the most recent being WINDOW 4.1 and VISION3. They differ in appearance because WINDOW is text based and VISION3 incorporates a graphical user interface (GUI) but they perform similar solar optical and heat transfer calculations to arrive at center-glass U-factors and solar heat gain values. More detail can be found in Wright's "Summary and comparison of methods to calculate Solar heat gain". This article examines window solar heat gain-how it is calculated and what affects it. Solar heat gain is quantified by the Solar Heat Gain Coefficient (SHGC). SHGC is the fraction of incident solar radiation that reaches the conditioned space. It is customary to consider each of three areas: (1) the center-glass area, A, (i.e., the glazed area more than 2.5 inches (63.5 mm) from any sight line, (2) the edge-glass area, and (3) the frame area, Component SHGC values are area-weighted to give a total window SHGC.
A two-dimensional numerical model for glazing system thermal analysis
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1995-08) Wright, John L.; Sullivan, Harry F.
A simple two-dimensional (2-D) numerical control volume formulation is presented that can be used to model heat transfer through a vertical insulated glazing unit. This model accounts for natural convection of the fill gas (including the effect of secondary cells), conduction within the solid materials, and radiant exchange between the various surfaces facing the fill-gas cavity. This model closely reproduces average and local heat transfer rates measured using a guarded heater plate apparatus. Simulations clearly show that fill-gas motion causes the minimum indoor surface temperature (during cold weather) to be located at the bottom edge of the indoor glazing. Calculated results were also used to gain insights into heat transfer patterns in glazing systems with various combinations of low-emissivity coatings, fill gases, and edge-seal designs.
Summary and comparison of methods to calculate solar heat gain
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1995-08) Wright, John L.
Methods used to calculate the solar gain of windows (including center-glass, edge-glass, and frame) are examined and compared Particular attention is devoted to the public-domain computer programs VISION3 and WINDOW 4.1. Calculated results are presented to quantify the sensitivity of solar heat gain with respect to a wide range of glazing system design parameters and operating conditions. Details concerning solar optical properties and heat transfer mechanisms are examined and discussed When possible, comments are made concerning the development of solar gain measurement procedures. Solar gain is most sensitive to the solar optical properties of the glazings--the most important property being the transmittance of the outdoor glazing. Variables that directly affect heat transfer rates (e.g., fill gas type, convective heat transfer coefficients) have a significantly smaller effect.
A Correlation to Quantify Convective Heat Transfer Between Vertical Window Glazings
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1996) Wright, John L.
Several correlations have been used in recent years for the purpose of calculating convective, centre-glass heat transfer rates across gas-filled interpane window cavities. These correlations are examined and their background discussed. The most recent experimental data are gathered and presented. These data were used to develop a new correlation specifically for the purpose of window analysis. The new correlation is not restricted to conditions customarily encountered in window applications (i.e., low Rayleigh number, high aspect ratio). It also is valid with respect to applications involving low aspect ratio (i.e., windows with wide pane spacing or narrow spacing with muntin bars) and/or applications involving high Rayleigh number (e.g., wide pane spacing, krypton fill gas).
A study of insulated glazing unit surface temperature profiles using two-dimensional computer simulation
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1996) Wright, John L.; Sullivan, Harry F.; De Abreu, Pedro Felipe; Fraser, Roydon A.
This paper describes one part of a collaborative research project, including both measurement and simulation studies, aimed at determining the surface temperature of a set of insulated glazing units (IGUs). In this study computer simulation was used to determine the vertical surface temperature profiles of seven air-filled glazing units. Glazing system design options included variations in edge-seal type, pane spacing, low-e coating, and number of glazings. Two approaches were taken: one, a simulation of the complete problem domain using a fully detailed two-dimensional numerical simulation program (BRAVO); the second, a simplified approach using the VISION4 program for one-dimensional center-glass analysis and the FRAME 4.0 program for analysis of the remaining sections. This study serves as an important step in the development of alternative methods for evaluating condensation resistance. The present study significantly extends the database of two-dimensional simulation results. Details regarding the other parts of this project can also be found in the literature.
Overview of a Project to Determine the Surface Temperatures of Insulated Glazing Units: Thermographic Measurement and Two-Dimensional Simulation
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1996) Wright, John L.; Sullivan, Harry F.; Fraser, Roydon A.
A collaborative research project was undertaken to generate surface temperature profiles for the indoor side of seven different double and triple-glazed insulated glazing units exposed to the ASHRAE winter design condition. Four research groups produced four sets of results in a blind study. Two sets were measured by means of thermography and two were generated using two-dimensional numerical simulation. In addition, each simulation group produced results using simplified methods. Companion papers each present results from the individual studies along with some observations and commentary. This paper, an overview, presents a compilation of results and provides the opportunity for a variety of comparisons. Good agreement was found among all four sets of data. Simplified simulation models also show promise. The reassurance offered by these accomplishments is important because both the measurement and simulation methods are in the early stages of development. In addition, details found in individual temperature profiles provide valuable insights regarding the mechanisms of window heat transfer.
Calculating Center-Glass Performance Indices of Windows
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1998) Wright, John L.
Building envelope performance is strongly influenced by solar gain and heat transfer through windows. The majority of this energy gain or loss passes through the center-glass area of the glazing system. Various methods have been devised to calculate the corresponding center-glass performance indices. Solar heat gain coefficient (SHGC) and U-factor are the quantities most frequently sought. Hand calculations have given way to computer-based techniques. Computer simulation offers the opportunity to employ more detailed models plus the ability to model the large number of glazing systems made possible by design options, such as low-emissivity or solar-control coatings, selective glass tints, substitute fill gases, and glazing layers, that partially transmit longwave radiation. A new, more accurate method is presented in this paper for manipulating spectral optical data while calculating the energy related optical properties of glazing layers and glazing systems. The use of the same technique to track visible and ultraviolet radiation is also demonstrated. In addition, more refined methods are documented for calculating SHGC and U-factor while accounting for the thermal resistance of individual glazings.
Grid Filters for Local Nonlinear Image Restoration
(University of Waterloo, 1998) Veldhuizen, Todd
A new approach to local nonlinear image restoration is described, based on approximating functions using a regular grid of points in a many-dimensional space. Symmetry reductions and compression of the sparse grid make it feasible to work with twelve-dimensional grids as large as 22¹². Unlike polynomials and neural networks whose filtering complexity per pixel is linear in the number of filter co-efficients, grid filters have O(1) complexity per pixel. Grid filters require only a single presentation of the training samples, are numerically stable, leave unusual image features unchanged, and are a superset of order statistic filters. Results are presented for additive noise, blurring, and superresolution.
A Simplified Numerical Method for Assessing the Condensation Resistance of Windows
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1998) Wright, John L.
Methods have been established for calculating heat transfer in windows whereby a one-dimensional analysis is used for the center-glass area and a two-dimensional numerical calculation is used to model conduction in the edge-glass and frame. The effect of fill gas motion cannot be seen because the fill gas is treated as an opaque solid. The fill gas cools the bottom edge of the indoor glazing, so the predicted minimum indoor glazing temperature will consistently be too high. A detailed two-dimensional simulation of the entire window can be used but requires substantial effort. A simplified method has been devised. The flow pattern of the fill gas in the entire cavity is found using a two-dimensional computational fluid dynamics (CFD) analysis of natural convection where the wall temperatures are established using the one-dimensional center-glass model. Velocities in the edge-glass and the temperature of the fill gas entering the edge-glass section are noted. These data are used in a two-dimensional edge-glass/frame analysis. This method is not complicated and results are obtained quickly. Temperature profiles agree with experimental data and detailed numerical simulation. Sample results in this paper demonstrate the effect of fill gas motion, edge-seal conductance, a low-emissivity (low-e) coating, and argon fill gas on minimum indoor surface temperature.
Computer Simulation of Window Condensation Potential
(American Society of Heating, Refrigerating and Air-Conditioning Engineers, 1998-12) McGowan, Alexander G.; Wright, John L.
Condensation on windows creates obscured view, can cause building damage, and may lead to mold growth and poor indoor air quality. The Canadian Standards Association (CSA) has developed new procedures to evaluate window condensation potential, using a combination of computer simulation and testing. This paper summarizes results of a study into various aspects of computer simulation related to the evaluation of condensation potential. These findings were used to assist in the development of the CSA procedures.

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