Experimental investigation of transient thermal convection in porous media

A laboratory experiment of transient thermal convection in a 1-m-high cell was conducted to compare the length and time scales of plume development to theory. The temperature field was resolved to less than 1 mm and was measured by dissolving a solution of thermochromic crystals into the water–glycerin working fluid. The time-dependent experiment was run by applying heat at the bottom boundary that eventually was 6oC above the background temperature of the fluid. After development of a thermal boundary layer, the instability became visible at 26 min, with the development of 11, 3–4 cm width plumes growing from the boundary layer. The initially rapid growth rate reached a limiting velocity of approximately 0.5 cm min-1, and then decelerated throughout the experiment. Plumes interacted primarily by merging together; by the end of the experiment only three plumes were present. The Nusselt number at the onset of convection was 10, although it dropped to 4 after 45 min, which would be expected of a barely unstable system

Predatory Lending Laws and the Cost of Credit

Various states and other local jurisdictions have enacted laws intending to reduce predatory and abusive lending in the subprime mortgage market. These laws have created substantial geographic variation in the regulation of mortgage credit. This article examines whether these laws are associated with a higher or lower cost of credit. Empirical results indicate that the laws are associated with at most a modest increase in cost. However, the impact depends on the product type. In particular, loans with fixed (adjustable) rates are associated with a modest increase (decrease) in cost. Copyright 2008 American Real Estate and Urban Economics Association