Trade Studies

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Effectiveness of a Passively Cooled, Annular Heat Sink This report studies the effectiveness of an annular heat sink passively cooled by free convection. Analysis of the heat sink results in two graphs. The first graph allows the designer to choose the number of fins and fin thickness necessary for maintaining a set temperature difference between the heat sink and the ambient air. The second graph shows the minimum base height required to support the heat sink chosen from the first graph. Thus, this report simplifies designing a heat sink’s geometry to looking at two graphs. Parabolic Trough Solar Collector Analysis The purpose of this trade study is to examine a parabolic trough and determine the ideal width and focal length given constraints on the amount of light available, the length of the trough, and reflector material properties. It will show for a 48 inch heat collection element and Southwall's Silver-BSR, the ideal width is 50 inches and the ideal focal length is 5.75 inches given South Bend, IN solar radiation. Sizing a Flywheel and Engine Lengths The purpose of this study is to determine the length of two engine links which will generate the highest average torque from our engine during the power stroke and to size the lightest possible flywheel to smooth operation in the engine based on that torque. This study will greatly influence the sizing of mechanical components of the engine, as well as its overall weight, efficiency and size of our design. Stirling Engine The purpose of this trade study is to determine key design variables for the design of the stirling engine and to determine how they will affect other aspects of the design, particularly the feasibility of the overall design. The design variables considered in this study are the engine speed in rpm, the mass of air m, and the engine dimensions, including the length L, the stroke length S, and the diameter D. It is found that for the optimum design of engine speed at 9 rpm, m = .0044 kg, L = 12 in, S = 9.6 in, and D = 5 in, the maximum pressure is Pmax = 127.8 kPa, and the maximum power is achieved, W = 69.5 Watts at an efficiency of 26%. Supporting Truss Structure The purpose of this feasibility study was to determine the optimum angles for a truss structure to support a range of loading conditions. Another result of this trade study was to calculate the optimum dimensions and material for the links with cost as the measure of merit. The support structure is essential for supporting the trough and evacuated solar tube at a 30 degree angle for natural convection to provide fluid circulation in the heat tube. After calculating how stress varied with loading conditions, increasing the truss angle above 30 degrees did not have a significant impact on stress reduction. Once the geometry of the truss was determined, aluminum and steel were compared on a cost basis by determining the minimum size of links required for each material that would ensure that stresses would remain below failure stress by a safety factor of 2. Steel required a significantly lower cross sectional area to remain within the safety factor and thus significantly smaller diameter pipes than aluminum. Therefore, schedule 40, ½” steel pipes were chosen as the material for designing the support structure.
Last Updated: April 24, 2008 18:15

Effectiveness of a Passively Cooled, Annular Heat Sink

This report studies the effectiveness of an annular heat sink passively cooled by free convection. Analysis of the heat sink results in two graphs. The first graph allows the designer to choose the number of fins and fin thickness necessary for maintaining a set temperature difference between the heat sink and the ambient air. The second graph shows the minimum base height required to support the heat sink chosen from the first graph. Thus, this report simplifies designing a heat sink’s geometry to looking at two graphs.

Parabolic Trough Solar Collector Analysis

The purpose of this trade study is to examine a parabolic trough and determine the ideal width and focal length given constraints on the amount of light available, the length of the trough, and reflector material properties. It will show for a 48 inch heat collection element and Southwall's Silver-BSR, the ideal width is 50 inches and the ideal focal length is 5.75 inches given South Bend, IN solar radiation.

Sizing a Flywheel and Engine Lengths

The purpose of this study is to determine the length of two engine links which will generate the highest average torque from our engine during the power stroke and to size the lightest possible flywheel to smooth operation in the engine based on that torque. This study will greatly influence the sizing of mechanical components of the engine, as well as its overall weight, efficiency and size of our design.

Stirling Engine

The purpose of this trade study is to determine key design variables for the design of the stirling engine and to determine how they will affect other aspects of the design, particularly the feasibility of the overall design. The design variables considered in this study are the engine speed in rpm, the mass of air m, and the engine dimensions, including the length L, the stroke length S, and the diameter D. It is found that for the optimum design of engine speed at 9 rpm, m = .0044 kg, L = 12 in, S = 9.6 in, and D = 5 in, the maximum pressure is Pmax = 127.8 kPa, and the maximum power is achieved, W = 69.5 Watts at an efficiency of 26%.

Supporting Truss Structure

The purpose of this feasibility study was to determine the optimum angles for a truss structure to support a range of loading conditions. Another result of this trade study was to calculate the optimum dimensions and material for the links with cost as the measure of merit. The support structure is essential for supporting the trough and evacuated solar tube at a 30 degree angle for natural convection to provide fluid circulation in the heat tube. After calculating how stress varied with loading conditions, increasing the truss angle above 30 degrees did not have a significant impact on stress reduction. Once the geometry of the truss was determined, aluminum and steel were compared on a cost basis by determining the minimum size of links required for each material that would ensure that stresses would remain below failure stress by a safety factor of 2. Steel required a significantly lower cross sectional area to remain within the safety factor and thus significantly smaller diameter pipes than aluminum. Therefore, schedule 40, ½” steel pipes were chosen as the material for designing the support structure.

Last Updated: April 24, 2008 18:15