Single-sided Heating Research Articles

Photographic Study on Two-Phase Flow Patterns of Water in a Single-Side Heated Narrow Rectangular Channel

Abstract Visualized experimental observation on flow patterns during flow boiling of water under single-side heated and fluid-inlet subcooled conditions in a vertical narrow rectangular channel with the cross section of 40×3 mm2 have been carried out. Four discernible flow patterns, which names dispersed bubbly, coalesced bubbly, churn flow, and annular flow are observed. Flow visualization in two dimensions of two-phase flow patterns for narrow rectangular channel, which provided clearer evidence to distinguish flow patterns, have been performed. Based on the experimental results, a flow pattern map for single-side heated narrow rectangular channel has been developed and then compared with the exiting maps and flow transition criteria.

Thermal Performance of a Prototypical Gas-Cooled T-Tube Divertor Module with Single-Sided Heating

Extensive experimental and numerical studies of the planar jet impingement concept used in gas-cooled T-tube divertor modules have been previously performed at Georgia Tech.1 The experiments were used to validate the numerical CFD model based on the FLUENT[registered] software package. However, the test module used in those experiments did not duplicate the exact geometry of the T-tube divertor, particularly the single-sided nature of the incident heat flux. In this paper, the thermal performance of a prototypical T-tube divertor module is experimentally and numerically examined. The test module has been designed and constructed to match the geometry, dimensions, material properties, and single-sided heating configuration of the actual T-tube divertor. Experiments were performed using air as the coolant with different values of the incident heat flux. The coolant flow rate and inlet pressure were selected to span the expected range of non-dimensional parameters for the actual helium-cooled T-tube divertor design. The experimental values of the local heat transfer coefficient and pressure drop show good agreement with the numerical (FLUENT[registered] 6.3) predictions. The data obtained in this investigation provide added confidence in the predicted performance of the T-tube divertor concept, and the ability of the FLUENT CFD software package to predict its thermal performance, as well as the thermal performance of other complex gas-cooled high heat flux components.

Thermal performance study of integrated cold plate with power module

A novel cold plate for cooling of the electronic components with high heat flux and high heat dissipation requirements is proposed. The cold-plate structure of the S-type with guide plates is introduced to avoid the heat hot concentration and increase the heat transfer area. The experimental results show that the maximum chip temperature of the novel cold plate is approximately 40% lower than those of the conventional cold plate. Thermal performance optimizations are conducted, indicating that it is extremely effective to install the heat source on two sides of the cold plate. Compared with the single-side heat source, the maximum chip temperature is increased only 20%. However, the heat dissipation is doubled in the limited space for the double-sides arrangement heat source. Moreover, the integrated density of the power module is greatly enhanced by using the cold plate. Transient state temperature variation indicates that the cold plate have quick thermal response in start-up process. It is beneficial to the heat dissipation of integrated module for high power density.

Study on 100 Gbit/inch2 Density Molding Using Double-Sided Heat Insulated Mold

Previously we showed substrates without any pit deformation in the case of injection molding a 40 Gbit/inch2 read only memory (ROM) substrate using the single-sided heat insulated mold, in which a heat insulating plate was located below a stamper, and the slow mold opening method. This type of mold is characterized by the fact that pits on the substrates can be replicated at a low mold temperature, to avoid the twisting of substrates. However, it was found that the radial tilt was large. Therefore, we investigated this phenomenon using simulations, and fabricated a double-sided heat insulated mold with a symmetric structure in the thickness direction of the substrates. We showed that performing injection molding using this double-sided mold rendered the radial tilt of substrates controllable, so that it was possible to obtain flat disks. Furthermore, we obtained a 120-mm-diameter 100 Gbit/inch2 ROM substrate, which had no pit deformation over the entire pit area even though the pit wall angle was greater than 80 deg. This density corresponds to approximately 140 Gbyte.

Ultrasonic Pulse-Echo Subwavelength Defect Detection Mechanism: Experiment and Simulation

The ultrasonic pulse-echo backscattered amplitude integral (BAI)-mode imaging technique [IEEE Trans. UFFC, 45:30 (1998)] has demonstrated sensitive detection of subwavelength channel defects (38-μm diameter reliably and 6-μm diameter occasionally) in flexible 220-μm-thick food package seals (17.3 MHz, λ ≈ 86 μm). However, the underlying subwavelength defect detection mechanism is poorly understood. In this contribution, a theoretical modeling study was undertaken to elucidate the mechanism. The subwavelength diameter channel was fused in-between two plastic package films by applying heat from one side of the films. The sample cross-section microstructure was characterized from both optical and acoustic images. The cross-section impedance profiles along sample thickness dimension were determined. Although identical in nominal impedance properties before sealing, the two binding films showed an asymmetric impedance profile after sealing. Transient finite-element heat conduction analysis and impedance profiles of multiple-sealed package samples showed that the single-sided heating process caused an asymmetric impedance profile. A generalized impedance model was proposed based on these observations. An efficient two-dimensional simulation tool using a finite-difference time-domain method and the perfectly matched layer numerically evaluated the defect detection behavior of the radio-frequency (rf) echo waveforms. The normalized correlation coefficients between the simulated and the measured rf echo waveforms were greater than 95% for this generalized model, which suggested the validity of the proposed impedance model.

SIMULTANEOUS NATURAL-CONVECTION HEAT TRANSFER ABOVE AND BELOW AN ISOTHERMAL HORIZONTAL THIN PLATE

Numerical studies were conducted to investigate the simultaneous natural-convection heat transfer above and below an isothermal thin plate in an infinite space. The full two-dimensional conservation equations for laminar flows were solved. The numerical approach was based on the finite-volume technique with a nonstaggered grid arrangement. The SIMPLE algorithm was used for handling the pressure-velocity coupling. Plate width and temperature were used to vary the Rayleigh number over the range 1.0 2 10 5 to 1.7 2 10 7 . The expressions for numerical local and average Nusselt number were correlated, and horizontal velocity and temperature profiles were provided. It was found that the upper-surface Nusselt numbers are smaller than the corresponding lower-surface Nusselt numbers. Numerical results for upward- and downward-facing isothermal horizontal plates (single-sided heat transfer) were also shown for comparison. For these cases, Nusselt numbers on the upward-facing surface are larger than those on the downward-facing surface.

A step towards understanding the heating phase of laser transmission welding in polymers

AbstractIn recent years, laser transmission welding has gained in significance by displaying its specific advantages among the established welding processes for thermoplastics. However, a deep understanding of the developed process variants is so far missing. Useful results for temperature development were obtained in cases of high absorption constants by setting up an analytical model by analogy to single‐sided heat impulse welding. Yet there is no physico‐mathematical model considering the different energy conditions for joining parts with various absorption properties. This investigation is a first step towards a deep and detailed insight into the heating phase of the laser transmission welding process. Experimental data for temperature progression was collected for polypropylene. In addition, an analysis of the heat transfer problem using the finite element method showed a good level of agreement with the experimental results.

Limiting heat loadings to the beam dumps in the systems of injection plasma heating

Abstract The results of experimental studies of the heat exchange crisis in a strongly subcooled water flow under single-sided heating are given. The studies were done with the fragments of beam dumps from the fusion facility injection system. Description of a techniaue for identifying an instant of the heat exchange crisis start-up is given. An empirical relarionship for critical heat loading has been produced.

Experimental study of the heat exchange in the dumps of injection systems at fusion facilities

Abstract The results of the heat exchange experimental studies in a cylindrical pipe under single-sided heating with beams of charged particles (electrons) of high density of thermal energy are presented. The heat removal realized by a straight fluid flow, as well as by a twisted with a screw conveyer insertion one, strongly subcooled below the saturation temperature is presented. The experiments were done with a pipe fragment of the beam collector of the T-15 tokamak injection system. An experimental correlation to a curve of boihng, being a part of the adiabatic cross-section technique for calculating the heat removal parameters in multichannel of high power beams dumps (V.K. Naumov et al., Plasma Devices and Operations, 8, 1999), is presented. It is shown that the removed thermal flux density can attain ∼ 100 MW/m2 under the long-pulse heating (∼ 120 s) and under heat removal conditions with the twisted under heated flux of ∼ 170°C. It should be noted that the fatigue surface destruction takes place after 70 cycles of loading with the mentioned fluxes.

Laser Transmission Welding of Thermoplastics: Analysis of the Heating Phase

In laser transmission welding, the parts to be joined are brought into contact prior to welding, and the heating and joining phase take place simultaneously. The laser beam of the Nd:YAG laser penetrates the transparent part being joined and is converted into heat by the absorbing part. The transparent part is similarly heated and plasticised by means of heat conduction, thereby ensuring that the parts are welded together. When the heating phase was analysed, it was seen that if the part that absorbs the laser beam has a high adsorption constant, this process phase can be readily described by a physico-mathematical model by analogy to single-sided heat impulse welding. A comparison of calculated and measured melt layer thicknesses showed that, by introducing a correction factor, it is possible for this model to be successfully used for the case of a low absorption constant as well.

The effect of patterns on thermal stress during rapid thermal processing of silicon wafers

The presence of patterns can lead to temperature nonuniformity and undesirable levels of thermal stress in silicon wafers during rapid thermal processing (RTP). Plastic deformation of the wafer can lead to production problems such as photolithography overlay errors and degraded device performance. In this work, the transient temperature fields in patterned wafers are simulated using a detailed finite-element-based reactor transport model coupled with a thin film optics model for predicting the effect of patterns on the wafer radiative properties. The temperature distributions are then used to predict the stress fields in the wafer and the onset of plastic deformation. Results show that pattern-induced temperature nonuniformity can cause plastic deformation during RTP, and that the problem is exacerbated by single-side heating, increased processing temperature, and increased ramp rate. Pattern effects can be mitigated by stepping the die pattern out to the edge of the wafer or by altering the thin film stack on the wafer periphery to make the radiative properties across the wafer more uniform.

Finite-difference approximation of the adiabatic cross-section technique in a numerical analysis of the single-side heating process of a cooled pipe with the twisted tapeinside by an external heat flux pulse

Abstract The correct finite-difference diagram for the numerical study of the dynamics of single side heating of the pipe, with the twisted tape inside it, cooled with a forced coolant flow by an external heat flux pulse is proposed as a development of the adiabatic cross-section techniaue, the principal statements of which are given in1,4. This technique is illustrated by the results of numerical calculations for thermophysical and strength parameters of a full-scale pipe, as a heat absorbing element in the collector of deviated ions which is included into the injection system of T-15 tokamak under heating by an ion beam pulse, 1.5 sec. long, as well as by that, 0.5 sec. long, with successive cooling for one second. The results of comparison between the calculations, according to the analytical model proposed in4, and those by the finite-difference diagram under single side heating of a pipe by an external heat flux pulse, 1.5 sec. long are given.

Similarities and Differences between Single-Side and Uniform Heating for Fusion Applications—II: Sine Heat Flux

Quantitative correlation factors and functions are derived that relate the inside peak heat fluxes for cases involving either a single-side or a uniform external heat flux, which is applied to a circular coolant channel. The results are also presented in terms of a map that gives insight on how to improve high-heat-flux accommodation. The results show that similarities and differences depend on the channel geometry, material, and internal convection. 6 refs., 5 figs.

Thermal Stability and Flammability of Sulphochlorinated Polyethylene Compositions

Abstract The effect of some metal oxides used as nonactive fillers and fire retardant system components on thermal characteristics and flammability of sulphochlorinated polyethylene was studied. The flammability of compositions was estimated by the limiting LOJ method under standard conditions and also in the case of flame spreading in the horizontal direction and in the vertical one upwards. Temperature profiles in a burning wave were determined with the help of a thermocouple probe for optimum composition. Heat flows from the flame to the polymer surface were calculated. A materials fire-protective properties were estimated by the thermal shock method with single-side heating. The mechanism of a materials fire-protective effect was discussed.

Similarites and Differences Between Single-Side and Uniform Heating for Fusion Applications-I: Uniform Heat Flux

Similarites and Differences Between Single-Side and Uniform Heating for Fusion Applications-I: Uniform Heat Flux