Showing papers on "Fin (extended surface) published in 1975"

The Overall Convective Heat Transfer from Smooth Circular Cylinders

Abstract: Publisher Summary Accurate knowledge of the overall convective heat transfer from circular cylinders is of importance in a number of fields, such as boiler design, hotwire anemometry, and the rating of electrical conductors. The wide dispersion in the published experimental data for the heat transfer from smooth circular cylinders by natural and forced convection is attributed to various factors associated with the experiments. The error due to heat conduction to the supports is particularly important with natural convection, especially where the heat loss and the temperature rise of the cylinder are calculated from the voltage drop across it. A common cause of error is the use of too small a space ratio, so that the temperature and velocity fields are distorted. To reduce this error to less than l%, the space ratio D c /D for natural convection or D T /D for forced convection should exceed 100. The error caused by blockage with wind tunnel measurements can be calculated depending on the type of tunnel. One of the greatest sources of error with forced convection is the failure to allow for the effect of stream turbulence.

Plate and fin heat exchanger

Abstract: A plate and fin heat exchanger in the form of a refrigerant evaporator. The heat exchanger comprises a plate and fin structure providing alternately channels for the flow of refrigerant and spaces for the flow of air. An apertured inlet manifold is in communication with the refrigerant flow channels. A refrigerant distribution tube is inserted into the inlet manifold through the aperture in the latter. The distribution tube is provided with a series of orifices formed in the tube wall in register with the refrigerant flow channels. The improvement comprises a construction and arrangement in which the orifices are directed toward the air inlet side of the heat exchanger. Preferably, the orifices are directed to the air inlet side of the heat exchanger at an acute angle to a horizontal plane, the angularity being on the order of 0° to 15° relative to the horizontal plane and below the latter.

Solidification and Melting of Materials Subject to Convection and Radiation

Abstract: One-dimensional heat transfer in a finite region of solid or liquid with phase change associated with radiative and convective boundary conditions at the fixed boundary surface is solved using both Blot's variational and Goodman's integral methods. The total solidification time and the rates of solidification obtained based on the present approximate analyses agree very well with the numerical solutions of an earlier work.

Locking device for staggered fin-tubes

Abstract: A locking bar having feet which engage staggered finned-tubes of a heat exchanger to fix their positions in a support assembly formed from a plurality of support bars having interlocking arms.

Finned tube useful for heat exchangers

Abstract: A length of a tubing is helically wound with a fin made of a heat-radiating strip and which is corrugated to provide a series of transverse crimps. A base is provided by flattening a portion of the crimps with the use of pressure rollers at one edge of the strip when the section of the fin is "L" shaped, or at the middle of the strip when the section of the fin is "U" shaped in order to cling closely to the tubing. The fin is bent at the boundary area between the flattened portion and the crimped portion when the fin is helically wound around the tubing.

Heat Transfer and Friction Loss Performance of Perforated Heat Exchanger Surfaces

Abstract: A scale-up modeling technique has been developed to examine the effects of perforation geometry on the heat transfer and friction loss performance of compact heat exchangers having plate-perforated rectangular fin surfaces. The test cores, each consisting of a number of aluminum plates separated by wooden spacers to form parallel flow channels, were tested in a subsonic wind tunnel. The effects of the Reynolds number, plate surface porosity, core frontal porosity, and slot geometry on the heat transfer rate, friction loss, and noise intensity are determined. It is found that under certain circumstances plate perforation will produce significant improvement in heat transfer for the same pressure drop and pumping power. These studies are directed to the design of air-cooled condensers for Rankine cycle automotive engines, marine power propulsion systems, and the dry cooling towers of extra-high capacity electric power plants.

Certain aspects of film blowing of low-density polyethylene

Abstract: This article considers two topics: (1) Cooling of the film bubble and (2) Production of shrinkable film Heat is transported by conduction, convection, and radiation, but only convection and radiation are relevant for the cooling results Heat radiation can be calculated with known surface area, temperatures, and emission coefficient Here we learn that the emission coefficient depends on the film thickness Heat transfer by radiation amounts to about 15 percent of the total heat transfer Heat transfer by convection normally can be calculated by known methods assuming ideal flow conditions Because the flow conditions of the cooling air differ considerably from ideal conditions, known heat-transfer laws give incorrect results Therefore, a new formula was set-up by determining the heat transfer conditions in real experiments Each blown film is shrinkable, but in most cases the influence of the die on the shrinkage is disregarded The die causes an important anisotropy in the elastic behavior of the film Further on, shrinkage is influenced by the degree of bubble deformation, the temperature profile, and the deformation velocity between die exit and freeze line This is discussed qualitatively A calculations is not yet possible because of the unknown relaxation behavior of the melt The shrinkage of an LDPE blown film depends on time and temperature Time and temperature are exchangeable variables

Apparatus for the utilization of solar heat

Abstract: My invention relates to a unique apparatus for the utilization of solar heat which incorporates a hexagonal shaped collector element, which achieves maximum heat utilization in conjunction with a heat pipe for transfer of the heat collected by the element. Various minor modifications can be made to the heat collector element and/or the heat transfer pipe without departing from the spirit or the scope of the invention. Basically, however, it is the hexagonal shaped heat collector element with the heat transfer pipe passing therethrough at substantially the optimum position so that maximum heat transfer occurs from the heat collector element to the pipe within each individual element. The entire apparatus can be adjusted for optimum sun angle, depending upon the hemisphere or latitude of use, and extremely efficient heat transfer and use of solar energy is possible.

Heat collector and diffuser

Abstract: A heat collector and diffuser is disclosed for superimposition over elongated fin tube radiators in building heating systems. Blower means induces airflow across an elongated fin tube heat exchanger and into collector ducts which channel the heated air into a diffuser area where the blower means forcefully discharges the heated air into the roomer space. In this manner, inefficient and out-of-date heating systems may be improved and modernized without substantial changes or modifications.

Verification of the Heat-Field Concept for Sonic-Boom Alleviation

Abstract: The results of an experimental program carried out in the NASA-Langley 4 x 4 ft supersonic pressure tunnel to investigate the validity of the heat-field concept for sonic-boom alleviation are reported herein. The basic idea of the heat-field concept is to heat the flow about a supersonic aircraft in such a manner as to obtain an increase in effective aircraft shape (area distribution) that will result in a shock-free pressure signature on the ground. In the program, pressure signatures were measured below a series of wind-tunnel models to provide a step-by-step verification of the concept. For the key model tested, nitrogen is passed through the near of an off-axis slender fin situated below a representative SST configuration having its lift equivalence in volume. Comparisons of pressure signatures for this model with no flow, cold flow, and heated flow through the fin demonstrated substantial effects due to flow and due to heat, essentially verifying the use of mass flow and heat fields for providing equivalent area in supersonic flow. In addition, the ability of an off-axis slender fin to produce a finite-rise-time signature in the presence of lift was demonstrated by testing a wing-body model both with and without a solid fin.

Sheet metal spiral coil for tubular heat exchanger - is produced and installed on continuous cycle processing machine

Abstract: The tubular body of a heat exchanger is rotated and at-advanced through a fixed station where three roller units are placed in a common radial plane. The rollers perform the task of producing a spiral groove on the tube body, bend and locate the spiral fin plate in teh groove and with the third roller set, flatten the groove edges to form a firm location for the fin plates. The first roller set which is used to form the groove consists of three rollers with VEE-shaped radial edges. When they are pressed against the rotating tube, they produce a groove of progressive depth. Since no swarfs are cut, a ridge is formed. This ridge is forced back towards the groove after the fin spiral is located in it. This produces a firm joint between fin plate root and heat exchanger body, thus enhancing the heat flow.

Natural convection heat transfer between bodies and their enclosures

Abstract: Abstract: Natural convection heat transfer between concentrically located isothermal spherical, cylindrical, and cubical inner bodies and their isothermal cubical enclosure (with air, water, 20 cs silicone oil, and glycerin in the test space) was experimentally investigated. Comparisons were made with the existing data for these same inner bodies and a spherical enclosure. In addition, temperature distributions and flow visualization data were obtained for most of these geometries.

Solid state thermal control for spacecraft

Abstract: The steady-state heat-pumping capabilities of thermoelectric devices are examined for spacecraft in earth orbit, using a simple model. Thermoelectric parameters for a standard Bi2Te, alloy are fitted with fourth-order polynomials in temperature. Parameters are used which are the average for the temperature difference across the p-n couple. Internal spacecraft temperatures are varied from 270 to 330 K, and absorbed incident radiation fluxes are varied from zero to 700 W per sq m. It is found that heat rejection can be optimized with respect to thermoelectric device and radiator fin geometries, as well as with respect to input electrical power and that these devices are most useful on the surfaces with highest incident radiant power. Maximum heat fluxes which can be pumped out of the spacecraft are on the order of 50-160 W per sq m for the various thermal environments examined. Input electrical powers corresponding to these maximum heat fluxes range from about 50-300 W per sq m. However, efficiency is greatly improved by operation at lower input-power levels.

Experimental study of local heat transfer in horizontal enclosed layers

Abstract: Experimental results are presented for the local coefficient of heat transfer in horizontal enclosed layers over the range of Rayleigh numbers 1·103 3·103 can differ by as much as a factor of four from the average value

The influence of drilled cavities on natural convection heat transfer from a horizontal surface.

Abstract: The objective of this project was to study the effect that small artificial cavities have on natural convection from a horizontal surface. Tests were run with water and Freon 113. Data for heat flux as a function of bulk temperature difference were carefully obtained. These data yielded Nusselt number as a function of Grashof number or Rayleigh number. All of these were then compared with the data obtained by O'Connor [Ref. 3]. Experimental results are presented for the heat transfer from horizontal circular disks, with and without artificial cavities. The data from a mirror finished surface was compared to that of previous investigations and the agreement was good. The artificial cavities were found to affect the natural convection heat transfer from a horizontal surface: the heat transfer coefficients in both cases (water and Freon 113) were decreased.