Maximum Temperature Reduction Research Articles

Effect of Molecular Gas Radiation on a Planar, Two-Dimensional, Turbulent-Jet-Diffusion Flame

Non-gray radiation described by the exponential model for molecular gas bands was added to the numerical solution of turbulent combustion of methane in a planar, enclosed, jet-diffusion flame. The planar jet of methane is injected with velocity ufuel into a stream of air flowing with velocity uair parallel to the fuel. Diffusion-controlled combustion occurs in the mixing region of the jet. Plane-parallel, isothermal, black walls symmetrically located above and below the jet form the combustion chamber. A soot-free flame is assumed to exist so that molecular gas bands determine the thermal radiative transfer to the walls. Velocity, composition, and temperature fields and heat flux at the wall are obtained numerically. Approximately 40 percent of the requisite computation time is expended on the radiation calculation. Solutions are obtained to show the effect of channel size, air preheat, and product recirculation. Also the effect of reaction zone thickness was examined by varying an effective first Damko¨hler or mixing number which parameterizes the mixing-controlled reaction rate. It is found that a given reduction in maximum combustion temperature to reduce nitric oxide formation can be accomplished with a much less detrimental reduction on heat transfer by recirculating exhaust product into the combustion air than by reducing air preheat.

Heat Generated by MHD Couette Flow With Porous Walls

The simultaneous effects of mass injection and magnetic field on the heat generation due to viscous dissipation is investigated analytically. The present findings are in general agreement with the temperature measurements of Chang-Yi Wang [1]. Results indicate larger reductions in maximum temperature and a significant increase in the heat take off by porous boundaries, if magnetic field is present. The most striking feature of this investigation is the marked improvement in the temperature reduction with the application of the electromagnetic force.

Reduction of maximum temperature in the polymerization of cold‐ and heat‐curing acrylic resins

AbstractKinetic concepts of reducing exothermal effects during curing of biomedical acrylic resin systems are discussed. The effects of addition of 1, 4‐cyclohexadiene and cyclohexylmethacrylate to the monomer on the temperature rise in cold‐ and heat‐curing resin have been determined. Both compounds appear to be effective in damping the temperature peaks. Screening of compressive strengths and residual monomer determinations revealed that addition of cyclohexadiene results in a less complete polymerization than in the case of cyclohexyl methacrylate modified resins.

The structure of degenerate stars and their minimal properties

In this paper in section I the structure of massive fluid spheres (stars) which are composed of completely degenerate matters is investigated. Equations of equilibrium govering such configurations have been put in convenient forms. In section II a few minimal properties of the stars, such as the maximum (or minimum) central energy density and temperature, etc., have been studied. It has further been shown that for nondegenerate matters the reductions in maximum central energy density and temperature are proportional to 1/K33c−2 and 1/K3 respectively (c=2.998×1010 cm/sec andK3 is assumed to be greater thanK1(=3.17×1012).

The performance limits and design techniques of multistage thermoelectric devices

A method of calculating the performance limits of multi-stage thermoelectric devices is derived by a direct thermodynamic approach and a comparison is made between multi-stage and single stage devices. The results are then applied to the design of feasible multi-stage devices that closely approximate these limits. The calculations indicate that at present there is little advantage in using more than one stage in a thermoelectric generator. In the case of a thermoelectric refrigerator however, a practicable multi-stage device should be able to produce a temperature reduction about twice as great as that obtainable with a single stage device. This at present corresponds to a maximum temperature reduction of approximately 135°C for the multi-stage device. The approximate limits of feasible temperature reduction are calculated as a function of the value of the figure of merit Z. This calculation indicates that even if materials are improved by an order of magnitude or more it will probably never be feasible to construct a thermoelectric refrigerator that can cool to cryogenic temperatures while operating from a room temperature ambient.

Design and construction of a Peltier temperature-control device

A Peltier temperature-control device for use with micro-miniature electronics has been designed, built and tested. The principal features sought were (1) compatibility with conventional power supplies, particularly single-cell electrochemical systems, (2) techniques of assembly that are versatile with respect to physical configurations, and (3) techniques of assembly that are readily adaptable to production. The device contains a 1 in 3 temperature regulation chamber and operates from a supply voltage of 1·5–2·0 V at input powers up to about 6 W. Eighteen thermoelectric couples were connected in series electrically and in parallel thermally. Aluminum was used as the structural material, serving as both the base and the temperature-controlled chamber. An anodized layer on the aluminum provided good electrical insulation and thermal contact between the structural materials and thermoelectric elements. The circuit patterns were placed on the anodized layer by printed-circuitry techniques. By using jigs that are adaptable to quantity production, all 72 solder joints connecting the elements in series and to the structural materials were made in two operations. Tests and evaluation of the device show the performance to be that predicted by simple theory: (1) a maximum temperature reduction of 48°C from a room-temperature ambient; (2) a maximum input power of less than 6 W to maintain the controlled chamber at 25°C while the ambient varies throughout the military range (−54 to +71°C).