An Engineering Approach to the Variable Fluid Property Problem in Free Convection

An analysis is made for the variable fluid property problem for laminar free convection on an isothermal vertical flat plate. For a number of specific cases, solutions of the boundary layer equations appropriate to the variable property situation were carried out for gases and liquid mercury. Utilizing these findings, a simple and accurate shorthand procedure is presented for calculating free convection heat transfer under variable property conditions. This calculation method is well established in the heat transfer field. It involves the use of results which have been derived for constant property fluids, and of a set of rules (called reference temperatures) for extending these constant property results to variable property situations. For gases, the constant property heat transfer results are generalized to the variable property situation by replacing beta (expansion coefficient) by one over T sub infinity and evaluating the other properties at T sub r equals T sub w minus zero point thirty-eight (T sub w minus T sub infinity). For liquid mercury, the generalization may be accomplished by evaluating all the properties (including beta) at this same T sub r. It is worthwhile noting that for these fluids, the film temperature (with beta equals one over T sub infinity for gases) appears to serve as an adequate reference temperature for most applications. Results are also presented for boundary layer thickness and velocity parameters

Recommended Special Specification for Surfacing Materials for Signs and Markers

This special specification supersedes all previous specifications establishing requirements for surfacing materials for vertical signs and markers as defined below. This includes all previous special and temnorary specifications and part 7.23.SB of the Department\u27s 1945 Standard Specifications for State and Federal Road and Bridge Construction

Reflectorizing Surfaces for Signs and Markers

The attached copy of a proposed special specification for reflectorizing surfaces for signs and markers is submitted with the recommendation that this be considered by the specification committee, and furthermore that it be considered tentative. The specification was drawn up at the request of the Division of Maintenance in order that they would have some basis for differentiating materials offered by different vendors when invitations for bids are taken. I am sure that Mr. Palmer and Mr. Ringo consider the matter urgent

Cold-Applied Mastic-Type Crack and Joint Filler Compound

For the past year the Research Laboratory has been investigating joint filling compounds for concrete pavements with the object of determining whether extenders of one type or another placed in the hot-poured rubber-asphalt filler could reduce the cost without reducing the efficiency of these materials. Also included in the investigation was a search for new or different materials that might serve the same purpose but have properties that would make them more desirable or less expensive than the rubber-asphalt fillers. Because of the inconvenience and danger involved in the heating process to 450°F, and also the difficulty of controlling the rubber-asphalt types, a cold applied filler became of primary interest

Memo on Cold Applied Mastic-Type Crack and Joint Filler

For the past year the Research Laboratory has been investigating joint filling compounds for concrete pavements with the object of determining whether extenders of one type or another placed in the hot-poured rubber-asphalt filler could reduce the cost without reducing the efficiency of these materials. Also included in the investigation was a search for new or different materials that might serve the same purpose but have properties that would make them more desirable or less expensive than the rubber-asphalt fillers. Because of the inconvenience and danger involved in the heating process to 450°F, and also the difficulty of controlling the rubber-asphalt types, a cold applied filler became of primary interest