Showing papers on "Micro heat exchanger published in 1986"

Engineering Heat Transfer

Abstract: Fundamental Concepts Mechanisms of Heat Transfer Dimensions and Units Fourier's Law of Heat Conduction Thermal Conductivity Convection Heat Transfer Convection Heat-Transfer Coefficient Radiation Heat Transfer Emissivity and Other Radiative Properties Combined Heat-Transfer Mechanisms Steady-State Conduction in One Dimension One-Dimensional Conduction Equation Plane Geometry Systems Polar Cylindrical Geometry Systems Spherical Geometry Systems Thermal Contact Resistance Heat Transfer from Extended Surfaces Steady-State Conduction in Multiple Dimensions General Conduction Equation Analytical Method of Solution Graphical Method of Solution Conduction Shape Factor Solution by Numerical Methods (Finite Differences) Numerical Method of Solution for Two-Dimensional Problems Methods of Solving Simultaneous Equations Unsteady-State Heat Conduction Systems with Negligible Internal Resistance Systems with Finite Internal and Surface Resistances Solutions to Multidimensional Geometry Systems Approximate Methods of Solution to Transient-Conduction Problems Introduction to Convection Fluid Properties Characteristics of Fluid Flow Equations of Fluid Mechanics Thermal-Energy Equation Applications to Laminar Flows Applications to Turbulent Flows Natural-Convection Problem Dimensional Analysis Convection Heat Transfer in a Closed Conduit Heat Transfer to and from Laminar Flow in Circular Conduit Heat Transfer to and from Turbulent Flow in Circular Conduit Heat-Transfer Correlations for Flow in Noncircular Ducts Convection Heat Transfer in Flows Past Immersed Bodies Boundary-Layer Flow Turbulent Flow over Flat Plate Flow Past Various Two-Dimensional Bodies Flow Past a Bank of Tubes Flow Past a Sphere Natural-Convection Systems Natural Convection on a Vertical Surface: Laminar Flow Natural Convection on a Vertical Surface: Transition and Turbulence Natural Convection on an Inclined Flat Plate Natural Convection on a Horizontal Flat Surface Natural Convection on Cylinders Natural Convection around Spheres and Blocks Natural Convection about an Array of Fins Combined Forced- and Natural-Convection Systems Heat Exchangers Double-Pipe Heat Exchangers Shell-and-Tube Heat Exchangers Effectiveness-Number of Transfer Units Method of Analysis Crossflow Heat Exchangers Efficiency of a Heat Exchanger Condensation and Vaporization Heat Transfer Condensation Heat Transfer Boiling Heat Transfer Introduction to Radiation Heat Transfer Electromagnetic Radiation Spectrum Emission and Absorption at the Surface of an Opaque Solid Radiation Intensity Irradiation and Radiosity Radiation Laws Characteristics of Real Surfaces Radiation Heat Transfer between Surfaces View Factor Methods for Evaluating View Factors Radiation Heat Transfer within Enclosure of Black Surfaces Radiation Heat Transfer within an Enclosure of Diff use-Gray Surfaces Bibliography and Selected References Appendices Index

Heat exchangers and electrical apparatus having heat exchangers

Abstract: A heat exchanger panel suitable for cooling fluid filled electrical apparatus, such as electrical distribution and power transformers, and method of constructing same, which withstands substantially higher pressures without adding significantly to the weight of the heat exchanger. The metallic sheet which is used to construct the heat exchanger panel includes edges which define a substantially rectangular configuration, with predetermined opposite edges therof being folded to increase the edge thickness of the sheet prior to forming the fins. The fins are formed via bend lines which extend from folded edge to folded edge. This provides at least twice the material thickness where the heat exchanger panel is welded to the tank of the associated apparatus, and at least four times the material thickness where the folded fin is welded to form the fin cavity.

HYDRODYNAMICS and HEAT TRANSFER IN THIN FILM SCRAPED SURFACE HEAT EXCHANGERS — A REVIEW

Abstract: The available literature on hydrodynamics and heat transfer in thin film scraped surface heat exchangers was reviewed and arranged in concise form. the hydrodynamics covers fluid flow, residence time distribution, power consumption and film thickness. In heat transfer, sensible heating and evaporation aspects are explored. the constraints of various mathematical models are explained. the problems needing further investigation are also delineated.

Monogroove cold plate

Abstract: The coolant fluid evaporated in a compact heat absorbing panel (12) utilizing monogroove heat pipes in a pumped two-phase system is replenished through a liquid inlet control valve (35) under the control of an ultrasonic liquid presence detector (40) which is connected to the panel (10). The detector (40) maintains the desired liquid quantity in the panel's liquid coolant channels (25), thereby dynamically responding to varying heat loads.

Air-to-air heat exchanger

Abstract: A heat exchanger for ventilating insulated dwellings with minimum internal heat loss, is disclosed The heat exchanger is characterized by its very low manufacturing cost, its excellent efficiency and its minimum and easy maintenance The heat exchanger consists of an elongated box-like casing forming two opposite end chambers interconnected by a plurality of longitudinally-extending, thin walled glass tubes Warm stale and humid air is expelled through the glass tubes from one to the other chamber, while cool outdoor drier air is circulated within the casing along a generally sinusoidal path about the glass tubes, so that a heat transfer occurs through the walls of the glass tubes The casing is made of molded foam plastic for good heat insulation and in two half-parts having inner edges releasably and sealingly joined by a tongue-and-groove arrangement Each half-part has a tongue and a groove, each extending along half the periphery of its inner edge, so that the half-parts can be made in the same mold The casing is provided with a closure device, which can be easily released to open the two half-parts for easy maintenance of the inside of the heat exchanger

Method of transferring heat from a hot fluid A to a cold fluid using a composite fluid as heat carrying agent

Abstract: A method of transferring heat from a hot fluid to a cold fluid by means of a heat carrying fluid formed from at least two non azeotropic constituents contained in a looped circuit. The hot fluid gives up its heat in an exchanger, this heat being used for evaporating the heat carrying fluid which is then condensed in an exchanger while giving up its condensation heat to the cold fluid. A heat carrying agent reservoir accomodates the heat flux variations and a system imposes a flow direction on the heat carrying fluid.

Heat pipe array heat exchanger

Abstract: A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

Testing and analysis of immersed heat exchangers

Abstract: The objectives were to determine the performance of four immersed, ''supply-side'' heat exchangers used in solar domestic-hot-water systems; to examine the effects of flow rate, temperature difference, and coil configuration on performance; and to develop a simple model to predict the performance of immersed heat exchangers. We tested four immersed heat exchangers: a smooth coil, a finned spiral, a single-wall bayonet, and a double-wall bayonet. We developed two analyticl models and a simple finite difference model. We experimentally verified that the performance of these heat exchangers depends on the flow rate through them; we also showed that the temperature difference between the heat exchanger's inlet and the storage tank can strongly affect a heat exchanger's performance. We also compared the effects of the heat exchanger's configuration and correlated Nusselt and Rayleigh numbers for each heat exchanger tested. The smooth coil had a higher effectiveness than the others, while the double-wall bayonet had a very low effectiveness. We still do not know the long-term effectiveness of heat exchangers regarding scale accumulation, nor do we know the effects of very low flow rates on a heat exchanger's performance.

Heat Transfer in Oil-Flooded Screw Compressors

Abstract: Thermodynamic efficiency of the compression process in oil-flooded screw compressors depends greatly on the oil-gas heat transfer process. The amount of heat transfer is a function of many parameters such as mode of oil injection, oil inlet temperature, etc. This paper describes a mathematical model to calculate this heat transfer, assuming that the oil is injected in the form of non-interacting spherical droplets. The droplet trajectories are calculated from the point of injection to the point where the droplets hit the moving boundaries of the compressor rotor. The overall heat transfer is calculated by summing the heat exchange over all the droplets during their free-flight time. This model is then used to calculate the effect of such heat transfer on compressor performance. Some guidelines on ways to enhance heat tran~fer are also provided.

Flue gas heat pump

Abstract: A flue gas heat pump is provided for extracting heat from the discharged hot flue gas of a furnace. The heat pump includes a condenser at the inlet of the furnace cabinet in heat transfer relation with the flow of air to be conditioned, and an evaporator disposed at the outlet of the furnace heat exchanger for extracting heat therefrom. A compressor is provided for compressing a refrigerant and delivering it to the heat exchangers. The compressor is located in the flow path of the air to be conditioned so that the heat generated by the compressor is transferred thereto.

Heat transfer and fluid friction in bundles of twisted tubes

Abstract: The results of heat-transfer and friction studies in bundles of twisted tubes and rods with spiral wire-wrap spacers are analyzed, and recommendations are given for calculating the heat-transfer coefficient in heat exchangers using twisted tubes

Application of finite elements in heat exchangers

Abstract: The application of finite elements in heat exchangers is illustrated, with the newly proposed element for two types of heat exchangers It is found that the present model predicts the temperature distribution accurately

Low Reynolds Number Flow Heat Exchangers

Abstract: (1986). Low Reynolds Number Flow Heat Exchangers. Nuclear Technology: Vol. 73, No. 1, pp. 129-130.

The consideration of dynamics and control in the design of heat exchanger networks

Abstract: The heat exchanger network method is a way of abstracting the en¬ thalpy and heat flows from the blueprints of a planned or existing processing plant. It enables a systematic design of a plant-wide heat recovery system which is optimal with regard to energy costs, capital costs and operational requirements. A heat exchanger network is a representation of all heat transfer relations between hot process streams (i.e. those which have to be cooled down, e.g. products of distillation) and cold process streams (i.e. those which have to be heated up, e.g. feeds to distillation) within a plant. During the past ten years, the optimal design of heat exchanger networks (i.e. the optimal arrangement of heat transfer relations within a plant) has developed into a field of research of its own. Most of the research in this field has concentrated on the steady-state performance of heat exchanger networks on both fixed and variable operating conditions (in the latter case the term "resilience" is fre¬ quently used). In this work, networks are investigated with respect to their dynamic performance. The intention is to find guidelines for a "design for controllability", which complement the existing steadystate design methods. Both, static methods ("interaction analysis") and dynamic methods ("process reaction curve analysis") from control theory have been used to explore the new field of heat exchanger network dynamics. As a major tool, an interactive, portable computer program for network simulation and controllability assessment has been developed (it is available as a design tool within the frame of the International Energy Agency). Based on the well-understood global parameters: effectiveness and NTU, which follow from the network design, some straightforward methods covering the following topics are presented:

The Effect of Fluid Property Variations on the Performance of Cryogenic Helium Heat Exchangers

Abstract: Balanced flow coaxial tube counterflow heat exchangers have application to a number of helium refrigeration systems. Variations in the helium fluid properties in heat exchangers of this type are large enough to cause concern over the accuracy of simplified constant property analyses. The effect of fluid property variations on the performance of such heat exchangers are investigated with a finite difference thermal model. The model uses temperature dependent values of specific heat, thermal conductivity, and viscosity to evaluate heat exchanger performance, but neglects the effects of pressure losses, internal wall thermal resistance and axial conduction. Ratios of analytically predicted to numerically determined heat exchanger effectiveness versus the design Ntu are presented. For values of Ntu of interest in most cryogenic applications (i.e., greater than 3), predicted performance using variable fluid properties is two percent greater than that predicted using mean properties.

Thin rod packing for heat exchangers

Abstract: The present invention provides heat exchanger apparatus and method for enhancing heat transfer between a fluid and a tubular heat exchanger surface. The invention involves a heat transfer surface, a heat transfer fluid passed along the surface, and a metal or ceramic thin rod packing positioned to impinge the fluid flowing within the heat transfer surface. The thin rod packing is established in the form of a screen heat exchange insert composed of a metal or ceramic material having a high adsorptance and emittance.

Nonazeotropic mixtures as working fluids in large heat pumps - Heat transfer in a falling film evaporator and system simulations

Abstract: The thesis is divided into two main parts, the first one dealing with heat transfer in the evaporator and the second one dealing with simulations of the whole heat pump cycle with nonazeotropic mixtures. One of the aims with the heat transfer studies was to investigate if the additional mass transfer resistance, introduced when mixtures are used, can be reduced in a thin falling film with high turbulence compared with corresponding one for a horizontal tube. The measurements were carried out in one smooth test tube with the mixtures on the inside. The investigated fluids are R22/R114, R12/R114 and R12/R11 and the corresponding pure fluids. For the mixtures the transition point between surface evaporation and nucleate boilng was depressed compared to pure fluids. This was found to be the main reason for the decrease of the heat transfer coefficients for mixtures. When all fluids were in the surface evaporating regime this decrease was small, as a maximum 21 %. The magnitude of the heat transfer coefficients varied between approximately 950 W/m2K and 4 000 W/m2K depending on Re number, heat flux and type of fluid. With aid of the computer program a parameter study on heat pump systems with nonazeotropic mixtures has been performed in the second part of this work. This study has been carried out for three case studies, two industrial ones and one space heating case. The results are shown as COP, heating capacity and condensing pressure. A special emphasis has been laid on the influence on these parameters of the heat exchangers size and a comparison between horizontal and falling film evaporators. The calculations have shown that, for given heat exchangers, there are in some cases possibilities for considerable increases of the COP. In favourable situations this improvement is in the order of 15-20 %. The heating capacity can be increased considerably in all cases where the "mean volatility" of the mixture is higher than that of the pure fluids, with which the comparison is made. Improvements of more than 100 % are possible to achieve. The comparison between falling film and horizontal evaporators has shown that the COP for a given area in some cases can be increased when the falling film type is used. In many cases the same COP can be achieved with a considerably smaller evaporator size, 50 % or less in the falling film case. This fact should make falling film evaporators economically interesting competitors to horizontal heat exchangers in the future.

Heat Transfer Characteristics of a Latent Heat Storage Unit with a Finned Tube : 2nd Report, Numerical Analysis of Solidification Process

Abstract: A three-dimensional numerical analysis, in which the axial variations of the temperature of a heat exchanger fluid and a solidification layer are taken into consideration, is made to obtain detailed information on the heat transfer characteristics of a latent heat storage unit with a finned tube The calculated results of the timewise variations of the heat flux and the solidification fraction are in good agreement with prior experimental data, so that the validity of the proposed numerical method is verified Also, using this method, the effects of the thickness and the number of fins on the heat transfer characteristics are shown

Heat exchangers in the form of finned tubes

Abstract: The invention relates to heat exchangers in the form of finned tubes or gilled tubes, the gills of which are, by means of appropriate shaping and/or additional clamping elements, connected to the tubes over a large area and so firmly that a particularly high heat transfer is ensured.

A procedure for calculating matrix heat exchangers formed from perforated plates

Abstract: A procedure is proposed for calculating matrix heat exchanger-recuperators, and it is shown that in the general case it is possible to adequately tabulate the efficiency as a function of the length of the apparatus for limited ranges of the important parameters.

A Study of Extended Surface Heat Exchange with Frosting : 1st Report, Overall Heat Transfer Characteristics

Abstract: The effect of deposition on heat and mass transfer was investigated both theoretically and experimentally in a finned tube type heat exchanger under frosting conditions. A method for predicting the efficiency of heat and mass transfer was presented based on a uniform frosting model. The predicted results were in good agreement with the experimental data obtained under the two typical operating conditions of heat exchanger, i.e., the constant air flow rate and the constant revolution number of blower.

Two-pass countercrossflow heat exchangers with both fluids unmixed throughout

Abstract: The aim of this paper is to present the formulas for computing the effectiveness and spatial temperature distribution of each stream and the wall of the two-pass countercrossflow heat exchangers with both fluids unmixed throughout for all possible flow arrangements

Method and device for treating tumour tissue by heat, by means of interstitial micro heat exchangers inserted in the body

Abstract: In methods of the generic type, energy transport into the diseased tissue is effected via small-dimensioned tubes through which warm water flows. The heat transfer on the inside of the tubes is always higher than that on the outside of the tubes resting against the tissue, i.e. the limiting factor in the heat transfer system is outside the heat exchanger which ensures a maximum energy transfer coupled with a minimum temperature of the tube walls. Through the interstitial heat exchangers there flows water or a mixture of water and alcohol maintained at 45-60 degrees centigrade by a precision thermostat. The heat exchangers can be implanted as a single tube by the perforation method and as a coaxial tube by the puncture method. The heat exchanger tubes and the connecting system are dimensioned such that they can also be used as carriers for radioactive products in the patient without any alteration. For microwave therapy, the same system can be used for cooling the antennas inserted in the body.

High effectiveness contour matching contact heat exchanger

Abstract: A high effectiveness contour matching contact heat exchanger (10) includes two opposing plates (12,13), each having alternating double rows (25) of attached pins (20) The ends (23) of the pins (20) opposite their respective plates (12,13) are received in tight-fitting holes (40) in the opposite plate (12,13), providing for flexibility of the heat exchanger (10) to maintain efficient thermal transfer contact between the plates (12,13) and the external thermal sources (50,51) of heat or cold, without causing gaps between the ends (23) of the pins (20) and their respective opposite plates (12,13) that decrease heat transfer effectiveness by adversely affecting flow distribution of the fluid flowing therepast