Infinite Sink Research Articles

Conversion of atmospheric heat into work

SYNOPSIS Just as a heat engine works between a finite source (produced by burning of fuels) and an infinite sink (viz. atmosphere), it can also work between an infinite source (atmosphere), and a finite sink, converting heat of the atmosphere into work. A relevant factor analysing the work of such heat engines is the amount of work output per unit quantity of heat flowing into the finite sink. Some possibilities of producing a finite sink are discussed and their specific work output capacities are calculated. A finite sink, liquid CO2, is equivalent to a liquid which is capable of producing 138°C, so far as working of a heat engine is concerned. It can act as a transportable, storable and inexpensive “sink storage” of solar energy. Another finite sink is aqueous solution of NH4CI or of NH4NO3. It can continuously convert atmospheric heat into useful work without violating the second law of thermodynamics.

Discussion on ‘selecting a working fluid for a Rankine-cycle engine’

The authors state the usual assumption that 'the theoretical maximum effectiveness of transforming heat into mechanical work is the Carnot efficiency, namely: r/c c = 1 TCOr~D/TEv, where TEV and TCOND are the maximum and minimum absolute temperatures of the cycle, corresponding to the saturation temperatures, respectively, of the evaporator and condenser'. While this is true of the particular circumstances of this project, where the source of heat is condensation of steam at constant pressure, it is not generally true of either primary or waste-heat sources. These are commonly either a stream of hot gas or of hot liquid, both of which in yielding up their heat may vary in temperature. Hence the ideal cycle to utilise such variable-temperature heat is not a Carnot cycle, nor any other ideal cycle such as the Stirling cycle, which embodies isothermal heat reception. It is no accident that the majority of practical heat engines use largely or entirely non-isothermal heat reception processes--all gas turbines and internal-combustion engines and even steam turbines are supplied by 'boilers' in which the bulk of the heat is supplied over a range of temperature--feed heating, superheating and reheating. Nevertheless, the belief survives--and is perpetuated in all text books of thermodynamics-that the Carnot-cycle efficiency is the ultimate ideal for which all heat engines should strive. As this writer has pointed out,1 Carnot himself clearly laid down as the basis for his cycle both an infinite heat source and an infinite heat sink. Under such circumstances

Laser surface alloying

Laser alloying is a material-processing method which utilizes the high power density available from focused laser sources to melt metal coatings and a portion of the underlying substrate. Since the melting occurs in a very short time and only at the surface, the bulk of the material remains cool, thus serving as an infinite heat sink. Large temperature gradients exist across the boundary between the melted surface region and the underlying solid substrate. This results in rapid self-quenching and resolidification. Quench rates as great as 1011 KS-l and concomitant resolidification velocities of 20m S-l have already been achieved. What makes laser surface alloying both attractive and interesting is the wide variety of chemical and microstructural states that can be retained because of the rapid quench from the liquid phase. These include chemical profiles where the ‘alloyed’ element is highly concentrated near the atomic surface and decreases in concentration over shallow depths (hundreds of nanometres), and uniform profiles where the concentration is the same throughout the entire melted region. The types of microstructures observed include extended solid solutions, metastable crystalline phases, and metallic glasses.

Theory of geminate recombination on a lattice

Central to the photogeneration process in molecular systems is the competition between the relaxation of an excited state (to the ground state) and the separation into an ion pair via charge transfer steps. We have developed the first comprehensive model of this process which depends on molecular parameters and denumerates the competition between the various rates. The model is discrete diffusion on a lattice in a combined Coulomb and external field. The model is solved exactly and is computationally straightforward. The analytic method we have used is quite general and can easily be extended to include a broad class of problems involving large numbers of (correlated) ‘‘special sites.’’ The main feature of the computation, needed to solve these problems, is the evaluation of the lattice Green’s functions in the presence of the electric field. Our solution has a larger range of applicability than the (continuum limit) Onsager theory and is more versatile in terms of initial conditions and modeling of transient phenomena. We will elaborate this approach and discuss our results for the quantum efficiency as a function of external field, temperature, and molecular concentration, η(E,T,c). We show that η(E,T,c) exhibits a diversity of behavior dependent on the relative magnitudes of inter- and intramolecular transition rates. Onsager-like behavior for η is contained in the infinite sink limit and more generally, η can change appreciably as a function of the molecular parameters even for a fixed initial separation r0. In this theory the r0 is geometry controlled, and the initial yield φ0 can be determined by the same competition of rates as control the long time yield. The short time yield is controlled by a few discrete hops and therefore follows an exponential decay as indicated by recent picosecond experiments. In general, within this framework, one can study the influence on η of such factors as dimensionality, lattice structure, disorder, tunneling transition rates, intramolecular rates, and intrinsic energy level differences.

Physical Modeling of Backside Gettering

ABSTRACTTo understand gettering action we have modeled the diffusion of metal to a backside getter. A first order model describing the diffusion of metals to an infinite backside sink is found not to fit experimental data. To fit the data for phosphorus gettering at 1000°C and argon implantation gettering at 800°C it is necessary to also hypothesize the injection of silicon interstitials. Assuming that the diffusion of the silicon interstitials is the rate limiting step in gettering, allows one to extract the diffusion coefficient and equilibrium concentration of the interstitial. The hypothesis of silicon interstitial injection agrees with recent work on phosphorus diffusion by Fahey et. al. To test this hypothesis for heavily damaged regions we have looked at the effect of an argon implanted region on the diffusion of a phosphorus buried layer. At both 800°C and 700°C, during nitrogen anneals we see significant enhancement of the phosphorus diffusion.

Role of crystallites in the performance of polycrystalline solar cells

The effects of the crystallite shape and size on the short-circuit current I sc and open-circuit voltage V oc of a polycrystalline solar cell were studied using simple geometrical models for spherical, square columnar and cylindrical grain structures on the assumption that the grain boundaries behave like an infinite sink of minority carriers. Both uniform and inhomogeneous generation of carriers were considered. It was shown that for spherical grain structures I sc can be at best 70% of the single-crystal value and that there will be a loss of at least 35 mV for V oc even for very large crystallites, for uniform generation. However, although for cylindrical and square columnar grain structures both I sc and V oc vary significantly with the grain size, for spherical grains I sc and V oc are relatively unaffected by the grain size variation. Experiments with sintered CdS/Cu 2S solar cells, which were assumed to have a spherical grain structure, appear to support these observations.

Heat Transfer in PAD Thrust Bearings

Results are presented of tests conducted on a 150 mm pad thrust bearing over the speed range 1000–4000 rev/min. Heat transfer to pads and runner is estimated from pad and runner temperatures. Pad heat transfer proved to be of minor importance. The runner is shown to approximate to an infinite heat sink. Heat transfer to the runner is dominated by the film thermal resistance and ranged from 0.1 to 0.8 of film energy dissipation. The dependence of film convective heat transport upon the film Peclet number is demonstrated and an improved method for the prediction of bearing performance is outlined.

Ammonia Exchange at the Land Surface1

AbstractStudies of NH3 exchange between plant leaves and air have mostly been made in controlled chambers where the concentrations were far above the ambient atmospheric levels usually found in nature. Under such conditions leaves act as an infinite sink for NH3. More recent controlled chamber studies, however, have shown NH3 evolving from leaves when concentrations were nearer to those of the atmosphere. In this study we measured both NH3 absorption and evolution by vegetation under field conditions using micrometeorological techniques where vertical profiles of wind and NH3 are measured. Both evolution and absorption strongly suggest that plants have a compensation point for NH3. Data are presented for fields of quackgrass (Agropyron repens L.), soybeans (Glycine max L. Merr.) and alfalfa (Medicago sativa L.). Computer simulation confirmed that vegetation exchange is concentration dependent. We speculate that plants (and soil) keep atmospheric NH3 in check, at low concentrations, with winds moving it from N rich to N poor ecosystems. Dispersed sources of NH3 from crop lands are probably increasing due to more fixed N in farming. Thus the added NH3 due to man's activity probably increases the net global biosphere uptake of both N and C.

Grain boundary diffusion of aluminum in polycrystalline silicon films

Grain boundary diffusion of Al in poly-Si films has been measured by an Auger sputter profiling technique in a temperature range of 350–425 °C. The Al atoms were observed to diffuse through Si grain boundaries, then accumulated near a poly-Si/SiO2 interface. By concentrating on the initial stage of diffusion, the diffusion problem was analyzed using a simple model in which a steady-state flux of Al though Si grain boundaries is accumulated by an effectively infinite sink at the poly-Si/SiO2 interface. Auger measurements yielded quantitative information regarding the concentration gradient in the middle of the poly-Si layer and the amount of accumulation near the poly-Si/SiO2 interface. From this information, the grain boundary diffusion coefficient of Al in Si Db was determined. The temperature dependence of Db fits an Arrhenius-type relation with D°b =1.3×107 cm2/s and Qb =2.64 eV. The measured activation energy was found to be consistent with that of the grain boundary diffusion of P and B as well as the dislocation diffusion As in Si.

Use of osmotically active therapeutic agents in monolithic systems

The functionality of a new class of monolithic systems for the controlled release of drugs is discussed. The systems consist of uniformly dispersed particles of osmotically active therapeutic agents (drugs) in biocompatible polymeric matrices. The drug particles are encapsulated by polymers to form a multiplicity of microcapsules throughout the matrix. These osmotic film systems display zero-order drug delivery kinetics. The principal energy source governing the release of agents is osmotic in nature. When such a film is placed in an aqueous infinite sink, the film imbibes water into the outermost layer of the dispersion at a rate dictated by permeability of the polymer. Water transport into the film continues until volumetric rupture of the drug-containing capsules occurs, after which time saturated drug solution is pumped through channels created by the rupture. This process repeats itself in a serial fashion until the system is exhausted of agent. Due to the osmotic functionality of these systems, reduction of the thermodynamic activity of water outside the system can proportionally reduce the release of agent. In this paper the effects of varying drug particle size, osmotic pressure gradients, system area, drug type, polymer type, and temperature upon the drug release kinetics are presented. Application of this new technology has allowed the fabrication of several useful drug therapeutic systems.

Computer simulation of flow-dependent absorption in microperfused short Henle's loop of rats

With computer simulation we examined the extent to which current theories and experimental data explain function of single microperfused superficial Henle's loops in rats. In the model standard phenomenological equations describe transport; two sets of transport parameters labeled rat and rabbit were taken from published experiments; Michaelis-Menten kinetics in the ascending thick limb were adjusted arbitrarily; tubular radius is either constant or depends on luminal pressure with compliance based on experimental observations; the interstitium is an infinite sink with salt and urea concentrations constant in the cortex and exponentially increasing in the outer medulla; concentrations resemble those found in hydropenic or saline diuretic rats. The following predictions were obtained. The model with rabbit parameters does not recirculate urea and will not operate with high medullary urea concentrations; with rat parameters too much urea recirculates an the results of perfusion with equilibrium solution are not reproduced. Using a compromise between rat and rabbit parameters, the model reproduces water absorption, salt reabsorption, and urea recirculation as observed in vivo in rat loops perfused at 5-40 nl/min. It also simulates perfusion with saline, equilibrium solution, saline plus furosemide, and 300 mM mannitol. When the model includes a short early distal segment, effluent salt concentration reaches a minimum at a 15 nl/min perfusion rate as observed in vivo; however, concentration at the macula densa is a monotonically increasing function of flow. When permeation rate is a function of wall surface area and thickness a better fit to experimental results is produced. However, the effect is small: water absorption alters by 4% or less and effluent salt concentration is reduced by up to 10% at low perfusion rates. Comparison of rigid and compliant loops shows no relationship between transit time per se and reabsorption.

Analysis of Grain Boundary Permeation in Solids

Methods are described to extract the grain boundary diffusion coefficient from experimental measurements of surface concentration of a diffusing species. For Type C kinetics, where bulk transport is negligible, easily used exact analytical solutions are available for infinite source and zero or infinite sink boundary conditions. For infinite or finite source and finite sink boundary conditions, the surface concentration is described by an exponential curve if the surface capacity is larger than the grain boundary capacity. The finite sink analysis has been applied to chromium diffusing in platinum, and was found to equal . For Type B kinetics, where bulk transport is not negligible, equations developed by Wuttig and Birnbaum may be used with a general criterion for approximating the bulk lattice flux developed in the present work. These solutions are available for infinite and finite source and infinite and zero boundary conditions. For an infinite source and sink condition, was calculated for gold in platinum by a “time‐of‐penetration” measurement and was shown to equal .

Oxidation Kinetics of Cobalt Diffusing out of High Current Density (HCD) Plated Gold

Auger electron spectroscopy and Auger depth profiling techniques have been used to study the growth kinetics of cobalt oxide films which form on thermally aged HCD‐plated hard gold in dry laboratory air. Films were observed to grow according to parabolic growth kinetics. At temperatures of 150° and 180°C, a large amount of potassium is observed on the film surface and may be associated with the observed recrystallization in hard gold electroplates. Film growth appears to saturate at 180°C for times greater than 48 hr. A general model was developed for film growth on dilute two‐component noble metal alloys exposed to a single reacting gas specie, assuming conservation of the reacting specie (flux continuity at the metal‐film interface) and parabolic film growth. The conditions necessary for the film growth to be controlled by diffusion from the alloy are given in terms of the material constants. For this specific case, the general solution reduces to that of an infinite sink and the diffusion constant can simply be computed from the parabolic growth rate constant. The diffusion coefficients for Co in Au were calculated between 100° and 180°C. An activation energy of 1.83 eV was obtained for this process.

On the Limits to Energy Release and Implications for Present Policy

Technology has been a provider of benefits directly improving man’s lot. These benefits have usually gone first to those already at the top of society, but increased production has gradually spread them to those lower down. Today much of our technology is serving affluence rather than basic needs, yet worldwide poverty remains a dominant human problem. Perpetual technological growth is still seen by many as the solution to this problem. But we no longer operate in a world of infinite reservoirs—infinite sources and sinks. Though energy sources may prove to be virtually infinite, energy sinks and pollutant sinks are finite. Engineers have a responsibility to plan for such limitations. The capacity of the atmosphere as a heat sink remains an ultimate geophysical limit to energy release by man. Various writers have estimated the order of magnitude of this limit. Some of these estimates are discussed. Possible modes of approach to a limit are considered in the light of current trends, published predictions, and the problem of meeting human needs. It is found that U. S. planning for an orderly and equitable transition to a fixed-energy-rate economy is already overdue.

Efficiencies of thermodynamic processes

When a system is in a state which differs from that of the infinite atmosphere surrounding it, its capacity to do work is measured by the maximum work which the system is capable of producing as it interacts with the infinite sink and eventually reaches the same state as the sink. When the system is subjected to a process there is, in general, a work interaction between the system and the surroundings, together with an exchange of heat with a source or with a sink other than the infinite sink. Here the actual change in available energy is compared with the ideal change in available energy. An efficiency for the process is defined, which will reflect all the losses or irreversibilities in the process. Hitherto, the definition of efficiency for any process from a purely thermodynamic viewpoint has been hampered by using different fundamental relationships in flow and nonflow processes, and for the flow process analysis it has been restricted to adiabatics in which the well-known parameter called `effectiveness' is used as a criterion of efficiency. In the analysis given here the same basic relationships are used independent of the circumstances in which the process takes place. This has been achieved by introducing the concept of `high-grade' energy.

Steady state technique for measuring fluxes and diffusivities in binary liquid systems

AbstractA steady state experimental technique for measuring fluxes of the components and diffusivities in binary liquid systems has been developed. Steady state diffusion is established through a sintered glass diaphragm of ultrafine porosity with a known concentration difference across the diaphragm. The concentrations are maintained by a flow of solution on one side of the diaphragm and an infinite sink on the other side. The fluxes and diffusivities are calculated from the measured flows and compositions. A syringe pump capable of delivering extremely small flow rates with good reproducibility is used to pump the solution past the sintered glass diaphragm. The diffusion cell design permits an accurate control of pressure drop across the diaphragm so that fluxes can be measured both with and without pressure gradients. The diffusion cell was calibrated by using the hydrochloric acid‐water system.Three binary systems, ethanol‐benzene, aniline‐benzene, and aniline‐carbon tetrachloride were chosen for diffusion studies. Diffusivity‐composition data for these systems at 25°C. were used to test the existing correlations for the concentration dependence of binary diffusivity. Of these, the empirical correlation of Vignes (11) represents the data satisfactorily. In addition, experimental molar diffusion flux ratio data for the above systems at 25°C. with no pressure gradients are reported and found to be essentially equal to the ratio of molar volumes of the components.

Bulk flow in diffusion coefficient studies

AbstractThe viewpoint is taken that bulk flow terms in the general equation of molecular diffusion must be measured in apparatus which offers no constraint to the molecular flux in either direction. It is proposed to carry this out in a miniaturized experiment operating with one side of the diffusion gradient as an infinite sink. Dimethyl acetamide–water diffusivities computed from such an experiment were found to be 7.02 × 10−6 sq.cm./sec. over a wide range of compositions. These are compared with values showing considerably wider variation with composition, namely, 2.45 to 7.00 × 10−6 sq.cm./sec. by estimating methods and 11.45 to 14.05 × 10−6 sq.cm./sec. by large cell experiments. Arguments are presented in support of the values obtained by the proposed method operating on a nonideal binary N, N‐dimethyl acetamide and water.

Analysis of Externally Pressurized Rectangular Pads with Multiple Supply Holes

The externally pressurized rectangular pad with multiple supply holes are analyzed theoretically by use of complex potential theory. An appropriate potential function, which satisfies the boundary conditions, is found by using infinite arrays of infinite sources and sinks. Then, the pressure distribution can be obtained theoretically, which leads to the determination of load capacity and flow. Results are given for both incompressible and compressible fluids. Experimental results coincide very well with theory concerning pressure distribution and load capacity if secondary effects owing to the compressibility of the fluid and pressure loss at supply holes is accounted for. Contributed by the ASLE Technical Committee on Bearings and Bearing Lubrication and presented at the Annual Meeting of the American Society of Lubrication Engineers held in Pittsburgh, Pa., May 3–5, 1966.

Development of a Thermally Conductive Ceramic Component Board

This paper describes the development and evaluation of a ceramic component board having all circuit connections electrically insulated but thermally grounded. Individual circuits are encapsulated in epoxy parallelopipeds having large diameter leads of nickel clad copper wire. The leads in turn are resistance welded to metallic (Kovar) studs which have been brazed into an inorganic (Beryllium Oxide Ceramic) wafer having exceedingly good thermal conductance. Interconnections between weld studs are accomplished by metalized plated runs. The component board assembly was then evaluated under simulated operating conditions, i.e., edge clamped to an infinite heat sink and in a vacuum environment. Internal heat rise within the circuit modules was monitored and compared to that found in another module which had not been welded to the board, and plots of the thermal gradients across the ceramic wafer were made.