Hawaii Geothermal Project : similarity solutions for free convection about a dike

An analysis is made for steady free convection of groundwater about a hot dike trapped in an aquifer of infinite extent. Within the framework of boundary layer approximations, similarity solutions are obtained for a class of problems where wall temperature varies as xλ, i.e., a power function of distance from the origin where wall temperature begins to deviate from that of the surrounding groundwater. The uniform heat flux solution emerged as a special case with λ = 1/3. It is found that vertical velocity and the temperature profiles are of the same shape, and that the boundary layer thickness is proportional to the square root of the distance from the leading edge. Analytical expressions are obtained for boundary layer thickness, local and overall surface heat flux, as well as the local and average heat transfer coefficients. Some representative velocity and temperature profiles around a dike are also presented.Prepared under National Science Foundation Research Grant No. GI-38319 and Energy Research and Development Administration Research Grant No. E(04-3)-1093

Hawaii Geothermal Project : free convection about a vertical cylinder embedded in a porous medium

An analysis is made for free convective flow about a vertical cylinder embedded in a saturated porous medium, where surface temperature of the cylinder varies as xλ, a power function of distance from the leading edge. Within the framework of boundary layer approximations, exact solution is obtained for the special case where surface temperature varies linearly with x, i.e., λ = 1. For other values of λ, approximate solutions based on local similarity and local non-similarity models are obtained. It is found that the local similarity solutions are sufficiently accurate for all practical purposes. Analytical expressions for local surface heat flux and overall surface heat flux are obtained.Prepared under National Science Foundation Research Grant No. GI-38319 and Energy Research and Development Administration Research Grant No. E(04-3)-1093

A Review of Global Ocean Temperature Observations: Implications for Ocean Heat Content Estimates and Climate Change

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Design and Evaluation of a Concentrated Solar-Powered Thermal-Pasteurization System

A device has been designed, constructed, and tested for heating fluids using solar energy. The device heats water to levels to kill pathogens by a parabolic reflecting surface that concentrates solar energy along an axis. Among the components that increase the thermal performance of the system is a thermally actuated valve, which controls the temperature and the thermal exposure duration of the fluid to cause deactivation of targeted pathogens. Also, a novel fluid-to-fluid heat exchanger arranged in counter flow is used. Experiments were performed with a water solution containing non-pathogenic Escherichia coli K-12 MG1655 (E. coli) bacteria. The results showed that the system is capable of pasteurization to levels where no living pathogens were detected in the heated fluid. The experiments were carried out over a wide range of temperatures and exposure durations to test the device and the underlying mathematical model. E. coli log reductions greater than 1 were achieved in all cases and it is shown that arbitrary values of reduction can be achieved with appropriate temperature/time settings