Showing papers on "Forced convection published in 1972"
TL;DR: In this article, the authors measured energy transport at Rayleigh numbers up to 675 times the critical (linear stability theory) value in a layer of dilute electrolyte bounded horizontally by two rigid planes of constant and equal temperature; Joule heating by an alternating current passing horizontally through the layer provides the volumetric energy source.
Abstract: Energy transport at Rayleigh numbers up to 675 times the critical (linear stability theory) value is measured in a layer of dilute electrolyte bounded horizontally by two rigid planes of constant and equal temperature; Joule heating by an alternating current passing horizontally through the layer provides the volumetric energy source. Horizontally averaged temperature profiles are determined optically. Mean temperature distributions are asymmetric at elevated Rayleigh numbers, the energy transport at the upper boundary being more than twice that at the lower boundary. Three regimes of flow are identified and discrete transitions in the energy transport appear to exist when the flow is turbulent. Extrapolation of the data to the conduction value of the Nusselt number yields a critical Rayleigh number which is within + 10·7% of linear theory values. No subcritical convection is observed when finite amplitude disturbances are introduced into the fluid at a Rayleigh number between the critical values predicted by the linear stability theory and energy theory respectively.
176 citations
IBM1
TL;DR: In this paper, the kinetics of fluid flow and of material and heat transport are discussed, while processes occurring in stationary and uniformly rotating containers are included, the emphasis is on forced convection phenomena due to accelerated or decelerated rotation.
113 citations
TL;DR: In this article, a finite difference solution of the equations describing transient natural convection in porous media is presented, and the linearized equations are solved to provide an estimate of the number of possible convective modes as a function of the Rayleigh number.
112 citations
89 citations
TL;DR: In this paper, the authors investigated mass transfer characteristics in a vapor deposition reactor and found that forced convection laminar flow in a rectangular reactor produced better uniformity on the deposition rate distribution across the width than did combined convection spiral flow.
Abstract: To study mass transfer characteristics in a vapor deposition reactor, gas flow patterns in a horizontal tube were investigated. Combined free and forced convection spiral flow and pure forced convection laminar flow were observed depending on experimental conditions of various flow rates and pressures. Further, local deposition rates under two flow behaviors were numerically obtained by solving a three‐dimensional mass conservation equation. It was estimated on the basis of calculated results that forced convection laminar flow in a rectangular reactor produced better uniformity on the deposition rate distribution across the width than did combined convection spiral flow.
77 citations
TL;DR: In this paper, an experimental investigation of free convection heat transfer from heated spheres to water is reported, and the experimental data extend over a wide range of Rayleigh number, thus covering the laminar, transition, and beginning of the turbulent regimes.
66 citations
TL;DR: In this article, the effect of component size on convective heat transfer from small devices (with surface areas between 2·00 and 0·01 sq cm) was investigated analytically and experimentally.
62 citations
TL;DR: In this paper, the forced-convection mass transfer of various realistic leaf models at Reynolds numbers 2 x 103
Abstract: The forced-convection mass transfer - and by analogy, heat transfer - of various realistic leaf models at Reynolds numbers 2 x 103
59 citations
TL;DR: In this article, two-phase boundary layer equations of laminar filmwise condensation are solved with an approximate method due to Jacobs under the conditions as follows; saturated vapour flows vertically downwards, a cooled surface of uniform temperature is placed parallel to the flow direction, both body force and forced convection are considered in the condensate film, which is so thin that the inertia and convection terms can be neglected.
54 citations
54 citations
TL;DR: In this paper, a study has been made of roof type solar stills under forced convection conditions, and the effect of water and ambient air temperatures, wind velocity, and angle of inclination of the cover on the performance of the still is shown by means of tables and graphs.
TL;DR: In this paper, experimental results are given concerning stationary heat and mass transfer in the laminar boundary layer of a vertical cylinder placed in still air, and the combined effect is considered as well as the two separate effects.
Abstract: In this paper experimental results are given concerning stationary heat and mass transfer in the laminar boundary layer of a vertical cylinder placed in still air. The combined effect is considered as well as the two separate effects.
TL;DR: In this article, the authors present the results of an experimental and theoretical study of heat transfer during film and transition boiling on vertical surfaces, where the theoretical analysis is confined to natural convection saturated film boiling, while the experimental work shows the effect of bulk liquid velocity with saturated and with subcooled methanol.
TL;DR: In this paper, the structure of finite-amplitude thermal convection within a self-gravitating fluid sphere with uniform heat release was determined for a fixed-surface boundary condition.
Abstract: Finite-difference calculations have been carried out to determine the structure of finite-amplitude thermal convection within a self-gravitating fluid sphere with uniform heat release. For a fixed-surface boundary condition, single-cell convection breaks up into double-cell convection at a Rayleigh number of 30,000, at a Rayleigh number of 500,000 four-cell convection is observed. With a free-surface boundary condition only single cell convection is obtained up to a Rayleigh number of 5,000,000.
TL;DR: The forced convection of heat from reed leaves was observed in their natural environment, and the turbulence of the natural wind decreased the boundary layer resistance around the leaf to about 40% of the resistance in a laminar steady wind.
Abstract: The forced convection of heat from reed (Phragmites communis) leaves was observed in their natural environment. The leaves were painted with liquid crystals, which displayed or indicated their temperature without any interference with natural air flow. Temperature differences as large as 15 C were observed between the leading and trailing edges of the nontranspiring, painted leaves. The turbulence of the natural wind decreased the boundary layer resistance around the leaf to about 40% of the resistance in a laminar steady wind.
TL;DR: In this article, the authors extended the theory to cover the case of the inclined cell and the vertical cell and showed that convection must be initiated for any temperature gradient to be established between the absorber plate and the glass cover plate.
TL;DR: In this article, the problem of combined forced and free-convection heat transfer from a thin needle in a uniform external stream is considered, and the series and local similarity solutions have been discussed.
Abstract: The problem of laminar combined forced and free‐convection heat transfer from a thin needle in a uniform external stream is considered. The series and local similarity solutions have been discussed.
TL;DR: In this article, it was shown that hydrogen and helium are experimentally more stable than argon or nitrogen under equivalent conditions, also in agreement with Rayleigh number calculations, in general agreement with hydrodynamic predictions, in flowing systems similar to those used in open tube chemical vapor deposition.
01 Jan 1972
TL;DR: The development of helium I forced-convection heat transfer systems can be an important key to solving some of the problems that superconducting magnet designers are now facing as discussed by the authors.
Abstract: The development of helium I forced-convection heat transfer systems can be an important key to solving some of the problems that superconducting magnet designers are now facing. Some of the advantages compared with conventional systems are (1) high heat transfer coefficients, (2) simple cryostat design, (3) modest refrigeration requirements (refrigerator directly coupled to magnet coils), (4) cooldown operations considerably simplified, and (5) electrical insulation problems eliminated (due to a more rigid construction).
TL;DR: In this article, a variational analysis of combined free and forced convection through vertical noncircular ducts is carried out using a VAE technique, where the condition of uniform peripheral heat flux is utilized in deriving the variational expression.
Abstract: Analysis of combined free and forced convection through vertical noncircular ducts is carried out using a variational technique. Fully developed flow with uniform axial heat input and uniform peripheral heat flux is assumed. All fluid properties are considered invariant with temperature except the variation of density in the buoyancy term of the equation of motion. The condition of uniform peripheral heat flux is utilized in deriving the variational expression. This procedure releases the thermal boundary condition from satisfying exactly the condition at the wall. A finite-difference procedure is carried out. For pure forced convection case, a particularly simple variational expression is presented. Nusselt numbers for combined free and forced convection are computed for rectangular, rhombic and elliptical ducts. An exact solution is presented for laminar forced convection through elliptic ducts. Variational results are in agreement with this exact solution. The present results are compared with those in the published literature wherever possible, and good agreement is obtained.
Patent•
16 Jun 1972TL;DR: In this paper, a double-walled reservoir filled with a material suitable for storing heat and provided with heating means for heating the material is considered, and means to effect the supply of heat from the reservoir to the surrounding ambient by forced convection are provided.
Abstract: A heat accumulating device includes a double-walled reservoir filled with a material suitable for storing heat and provided with heating means for heating the material. The free space bounded by the double walls of the reservoir accomodates a plurality of foil radiation screens and the free space is further filled with a hydrogen atmosphere. The hydrogen filled free space is in communication with a reservoir containing a thermally reversible hydrogen getter. By regulation of the temperature of the hydrogen getter by means of an electric heater associated therewith, the hydrogen pressure in the free space and hence thermal conductivity of the free space is controlled whereby the transfer of heat through the walls of the reservoir from the heat storage material is readily regulated. Means may be provided to effect the supply of heat from the reservoir to the surrounding ambient by forced convection. The free space may be divided into a plurality of compartments completely separated from each other with each compartment being communicating with a separate thermally reversible getter whereby discharge of heat from different portions of the reservoir can be separately regulated.
TL;DR: In this paper, an analysis of laminar film condensation of binary vapor mixtures undergoing forced flow down a vertical flat plate is presented, where the conservation equations representing the coupled two-phase flow problem are markedly nonsimilar and were solved numerically using a forward marching technique.
TL;DR: In this article, a new method of accounting for the influence of property variation on heat transfer by forced convection from heated surfaces to liquids is presented, which is used in conjunction with new experimental data to develop a correlation equation for forcing convection heat transfer from cylinders to liquids in crossflow.