Effects of design parameters on geared two-link mechanisms

The design of a specialized agricultural harvesting machine required the use of a path generation mechanism that was compact, accurate, inexpensive to manufacture and difficult attempts involved the use of a cam and follower, but they were expensive to manufacture and difficult to operate. This paper discusses an alternative method of using a coupled, open loop, two-link mechanism to generate a polygon-like closed path (pseudo-polygon) with an integer number of curved sides and apexes. A complete development of the path and path curvaturei equations are presented. The influence of the design variables on the coupler shape (flatness of each side) is shown in equation and design chart form. An example of a successful application of this design method applied to a plant cutting mechanism is presented.     

Evaluating the solar resource: a review of problems resulting from temporal, spatial and angular variations

Accurate assessment of the availability of solar energy at the Earth's surface is hampered by difficulties associated with the variability of solar radiation in space and time and with the angular position in the sky hemisphere. This paper assesses each of these problem areas by highlighting the difficulties and the attempts to offset them. Major emphasis is placed on extrapolation and interpolation procedures, the sensitivity of inclined surfaces to variations in the solar input, numerical models for calculating the irradiance of inclined surfaces and the time scales for which these computations are valid.Finally, the reader is urged to consider the significance of these difficulties in light of both radiation measurement errors and the sensitivity of the application to imprecise determinations of the radiation environment.     

Solar pond ground heat loss to a moving water table

An analytical solution is presented that calculates the heat loss from the bottom of a solar pond (or any heated object) to a soil that contains a moving water table. The water table is treated as a fluid slab moving as a slug flow in one dimension. Edge effects and horizontal heat conduction are ignored. Both steady-state and time-dependent solutions are presented. Results are presented in terms of an effectiveness ratio—the actual heat flux divided by the steady-state heat flux resulting from a constant temperature heat sink at the depth of the water table. The only water-table parameter that strongly affects the effectiveness is the fluid capacity rate. Thus, for any potential solar pond site, a measurement of the mass flow rate of the water table combined with knowledge of the soil thermal properties will allow a good estimation of the ground heat loss expected over the lifetime of the pond.     

Evacuated-tube directional-radiating cooling system

A new type of radiative cooling system is described. The radiator makes use of nonimaging optics and evacuated-tube technology to radiate significant amounts of heat to the 3 K environment of outer space. The nonimaging optics are used to direct the radiation overhead, through the most transparent part of the 8–13 μm atmospheric window. The required optical concentration is small, and relatively simple mirror geometries are possible. The evacuated-tube technology is used to attain storage temperatures at or below the freezing point, even when dewpoint temperatures are well above the freezing point.