Showing papers on "Heat exchanger published in 1993"

Stream temperature dynamics: Measurements and modeling

Abstract: A numerical model based on a finite difference solution of the unsteady heat advection-dispersion equation is formulated to predict water temperatures in streams at time increments of 1 hour. An energy balance accounts for the effects of air temperature, solar radiation, relative humidity, cloud cover, and wind speed on the net rate of heat exchange through the water surface, and heat conduction between water and streambed. Continuous stream temperature recordings in shallow streams show strong dynamic behavior including diurnal variations of several degrees Celsius which are lost in the standard daily records. These measured water temperatures are used to calibrate the model for the optimum percentages of Sun shading and wind sheltering. Stream exposure to solar radiation is shown to vary from 30 to 100% and wind exposure from 10 to 30% depending on the character of the stream. Values are related to stream width and season because of variable leaf cover of trees on stream banks. After calibration, accuracies of hourly and daily water temperature predictions over periods of several weeks are of the order of 0.2° to 1°C. Solar (shortwave) radiation is shown to be the most important component of the heat flux across the stream water surface, but none of the other components, i.e., long-wave radiation, evaporation, and convection to the atmosphere, are negligible. Conductive heat exchange between the streambed and the water is a significant heat balance component in shallow streams.

Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes: Part I—Laminar Flows

Abstract: Laminar flow correlations for f and Nu m are developed based on experimental data for water and ethylene glycol, with tape inserts of three different twist ratios. The uniform wall temperature condition is considered, which typifies practical heat exchangers in the chemical and process industry. These and other available data are analyzed to devise flow regime maps that characterize twisted-tape effects in terms of the dominant enhancement mechanisms. Depending upon flow rates and tape geometry, the enhancement in heat transfer is due to the tube partitioning and flow flockage, longer flow path, and secondary fluid circulation; fin effects are found to be negligible is snug-to loose-fitting tapes

Portable temperature control system

Abstract: A light-weight portable temperature control system which includes form fitting disposable therapy pads for selected body parts having serpentine fluid channels therethrough, a programmable microprocessor for controlling the temperature type and length of cycle, quick disconnects for the therapy pad, a thermoelectric cooler with a liquid heat exchanger and a pump for circulating the fluid through the system.

Battery-powered dispenser for hot melt adhesive

Abstract: A battery-powered dispenser for hot melt adhesive includes an elongated housing supporting a battery power source therein. A heat exchanger is supported within the housing interior and includes an elongated heat exchanger and a resilient support guide sleeve for receiving a to-be-melted low temperature stick. The heat exchanger includes a discharge nozzle and a recess for receiving and supporting an escott heating element which is operatively coupled to the battery power source.

Problems and Costs due to Heat Exchanger Fouling in New Zealand Industries

Abstract: Data are reported on the perception of fouling in New Zealand based on 200 companies and the application of nearly 2000 heat exchangers These data are discussed with respect to their occurrence for various heat exchanger applications, industries, and heat exchanger types The fouling mitigation strategies applied in New Zealand are depicted and compared with the state of the art in fouling mitigation as found from an extensive literature search Some comments are made as to the heat exchanger cleaning frequencies in New\Zealand industries Finally, an attempt is made to provide a reasonably reliable estimate of the annual fouling-related costs in New Zealand These results are then compared with those previously reported from the United States and England

Gas turbine engine fan cooled heat exchanger

Abstract: A fan-jet gas turbine engine heat exchanger is cooled by fan air taken from the fan duct at a relatively high pressure region of the fan nozzle upstream of the fan nozzle's throat and exhausted into a relatively low pressure region of the fan nozzle upstream of the throat. One embodiment provides a cooling air duct with a forward facing scoop at the duct's inlet for capturing cooling air and providing greater dynamic pressure recovery. A diffuser is located upstream of the heat exchanger and a nozzle is located downstream of the heat exchanger with a nozzle exit that forms the cooling duct outlet and an aft facing scoop over the outlet.

Gas turbine engine cooling system

Abstract: PURPOSE: To provide a gas turbine engine cooling system realizing improved cooling of high-temperature constituent portions and other portions. CONSTITUTION: A turbocompressor 128 and a heat exchanger 130 are fluidly interconnected and are each in fluid communication to receive air of differing pressures and temperatures. Typically, such air is received from various regions of an engine low pressure compressor and an engine high pressure compressor. A cooling system 110' delivers air through a duct 126 to a portion of the engine for cooling, such as the engine high pressure turbine region, at lower temperatures and higher pressures than if cooling air were directly ducted from the engine compressor to the engine turbine.

Device for cooling drive components and heating a passenger compartment of an electric vehicle

Abstract: A device for cooling drive components and heating a passenger compartment of an electric vehicle (69) with a drive motor powered by a battery (2) comprises a first coolant circuit (1) which is coupled to a second cooland circuit (5) via an intermediate heat exchanger (3). In the second coolant circuit (5) there is a first heat exchanger (6) acting as a cooler and a second heat exchanger (7) acting as a heater. The heat exchangers (6, 7) fitted in the second coolant circuit (5) each have a controllable by-pass (66, 67). A control device (10) detects several temperature conditions and signals derived from the battery control device (9) and processes them in order to actuate corresponding setting and operating means (17, 18, 19, 20) for the coolant flow.

Energy-conserving thermostat and method

Abstract: A thermostat (7) is described for controlling a furnace (2) for a hot air, hot water, or steam heating system which delivers heat to a heated space (5) via a delivery system (4). The thermostat (7) causes the system to conserve energy by limiting the 'burn' or on-time cycle to a system-specific interval during which the heat exchanger of the furnace (2) operates in its linear region. At the end of this interval (designated a 'MAX-ON' interval), the burn cycle is terminated, but delivery of heat to the heated space (5) continues for a secondary-delivery interval during which the furnace's blower (3) (or other delivery means) continues operation. The secondary-delivery interval ends when the residual heat has been extracted from the furnace (2) and delivery system (4). The system then remains off until the next burn cycle begins. The duration of the off-time interval is such that heat input to the heated space (5) and heat outflow to the ambient (6) from the heated space (5) are kept in equilibrium.

Method of making microchanneled heat exchangers utilizing sacrificial cores

Abstract: A method of making a unitary channeled heat exchanger wherein the unitary heat exchanger is to be connected with a first fluid circulation system The unitary heat exchanger preferably includes a first manifold connectible to the first fluid circulation system and a heat transfer body fluidically connected to the manifold The unitary heat exchanger is fabricated by forming a sacrificial core with a first manifold forming portion and a body forming portion having surfaces shaped generally similar to the desired shapes of the first manifold and body of the unitary heat exchanger, depositing heat exchanger forming material about the sacrificial core to form a shell about the sacrificial core, the shell preferably including a manifold and a body integrally formed, providing an access opening through the shell of the unitary heat exchanger, and removing the sacrificial core from within the shell of the unitary heat exchanger through the access opening, thereby leaving passages within the manifold and the body of the unitary heat exchanger that are in fluidic communication with one another The body forming portion of the sacrificial is further preferably made with one or more holes so that upon deposition of heat exchanger forming material, posts are formed connecting upper and lower plates of the shell of the heat exchanger for increased structural integrity Additionally, the deposition can be advantageously controlled so that apertures remain after the post or posts are formed, which may be used for mounting components or as part of a second fluid circulation circuit

heat exchanger tube

Abstract: A heat exchanger tube having an internal surface that enhances the heat transfer performance of the tube. The internal surface has ribs that run substantially parallel to the longitudinal axis of the tube. The ribs have a pattern of parallel notches intersecting and impressed into them at an angle oblique to the longitudinal axis. The pattern of ribs and notches increase the total internal surface area of the tube and also promote conditions for the flow of refrigerant within the tube that increase heat transfer performance.

System and method for high-efficiency air cooling and dehumidification

Abstract: The system in the present invention is an outside air ventilation cooling and room dehumidification system for use in commercial HVAC applications. The system includes a high-efficiency air filter, chilled water or evaporator precooling coil, a refrigeration compressor, an evaporator coil, a heat exchanger for removing heat and moisture from the air entering the evaporator coil and supplying heat to the air leaving the evaporator coil, a condenser coil located in the discharge airstream that reheats the air, and a fan to move the air through the coils. The heat exchanger can be a phase-change heat-pipe-type heat exchanger; a water cooling/heating coil "runaround loop"; an air-to-air plate-type heat exchanger; or a rotary heat exchanger.

Crystallization Fouling in Plate Heat Exchangers

Abstract: Crystallization fouling of calcium sulfate was investigated in a plate and frame heat exchanger. The effects of flow velocity, wall temperature, and CaSO 4 concentration on the fouling rates have been investigated and the distribution of scale along the heat transfer surface has been observed. The measured fouling curves are compared with predictions from a surface reaction controlled model

Aircraft cooling method

Abstract: A method for supplying cooling air on vehicles such as high speed aircraft includes diverting high pressure air from the compressor section of a gas turbine engine, cooling this air in a heat exchanger, and expanding the diverted high pressure air through an auxiliary turbine. Coolant in the heat exchanger may be inlet ram air, fan air, or aircraft fuel (which may be endothermic), and the coolant is ultimately introduced into the engine downstream of the compressor section. An auxiliary compressor may be used to further compress the diverted high pressure air or coolant prior to the flowing thereof through the heat exchanger, and one or more auxiliary turbines may be used to power the auxiliary compressor, or mechanical accessories on the vehicle.

Air manager system for metal-air battery

Abstract: An air manager system for a metal-air battery cell having an air cathode, the air manager system producing a flow of air through the air manager system and battery cell and directing a first air flow adjacent to the air cathode to provide reactant air and directing a second air flow adjacent to a portion of the battery cell isolated from the air cathode to provide cooling of the battery cell, preferably near the anode. The air manager system may be used with multiple cell metal-air battery packs. Heat exchange between the isolated air flows may be facilitated, and the reactant air may be recirculated for uniform cooling.

Active magnetic regenerator method and apparatus

Abstract: In an active magnetic regenerator apparatus having a regenerator bed of material exhibiting the magnetocaloric effect, flow of heat transfer fluid through the bed is unbalanced, so that more fluid flows through the bed from the hot side of the bed to the cold side than from the cold side to the hot side. The excess heat transfer fluid is diverted back to the hot side of the bed. The diverted fluid may be passed through a heat exchanger (59) to draw heat from a fluid to be cooled. The apparatus may be operated at cryogenic temperatures, and the heat transfer fluid may be helium gas and the fluid to be cooled may be hydrogen gas, which is liquified by the device. The apparatus can be formed in multiple stages to allow a greater span of cooling temperature than a single state, and each stage may be comprised of two bed parts (35, 36).

Controlled clean-emission biomass gasification heating system/method

Abstract: A biomass fuel gasification chamber, blast tube, and heat exchange chamber are interconnected horizontally and subjected to negative drawing pressure by a large variable speed chimney fan. An auger with an air lock feeds biomass fuel automatically into the gasification chamber. Fuel is moved across the gasification chamber on a partially serrated sloping grate. Three stages of fuel activity are created: anaerobic heating for pyrolysis, combustion, and incandescent charcoal oxydation for gasification. A variable speed fan, variable flue, and directional air duct and baffles control the stages with underfire air. A programmed auger in an airtight chamber removes ash automatically. In large systems a hydraulic moving wedge floor assists the fuel feeding auger and a moving sloping grate moves the fuel. A fan and long preheating duct with baffles and fins inside the gasification chamber preheat and direct air into a blast tube leading from the gasification chamber. Openings from the preheating tube angled both longitudinally and transversely into the blast tube create turbulence in the blast tube directed away from the gasification chamber. Preheated directed air flow and the negative pressure of the chimney fan draw gases from the gasification chamber into the blast tube, crack the gases, and shoot a fire blast into the heat exchange chamber. The fire blast heats an external system. Particulates are removed producing a clean-emission exhaust gas. Temperature and air quality sensors in the chimney provide feedback signals to various system controls to maintain optimum operating conditions.

Endoreversible thermal cycle with a nonlinear heat transfer law

Abstract: We calculate the efficiency of an endoreversible Carnot‐type cycle in the maximum power regime by using a nonlinear heat transfer law (the so‐called Dulong and Petit’s law of cooling). The results obtained from this model compare well (around 99% in some cases) with observed efficiencies for several power plants. The considered law of cooling includes conductive‐ convective and radiative contributions to the heat exchange between the working fluid and its surroundings. Our calculations improve considerably those obtained by means of a linear heat transfer law for the same power sources. We also analyze a nuclear power plant using an ecological optimization criterion for finite‐time heat engines.

Power and Refrigeration Plants for Minimum Heat Exchanger Inventory

Abstract: What has been accomplished to date on the question of how to minimize and allocate the heat exchanger inventory in power plants and refrigeration plants is summarized in a table. This table also highlights the three objectives of the present study. The first objective is to devise a much simpler model and analysis to reproduce in closed form Ibrahim et al.'s conclusions for fixed power and minimum UA (total heat exchanger inventory). The second objective is to consider the reverse of the refrigeration problem, and to minimize the total UA while holding the refrigeration load fixed. It will be shown analytically that (UA)[sub H] = (UA)[sub L] is once again a feature of the optimal design, the H and L referring to hot and cold ends of the heat exchanger. The third objective is to minimize the total heat exchanger inventory while holding the refrigerator power input fixed, and to show analytically that (UA)[sub H] = (UA)[sub L]. The overriding objective of this note is to demonstrate in the simplest analytical way possible that power plants and refrigeration plants share a common optimization principle. That principle is that the needed heat exchanger inventory is minimum when it is divided evenlymore » between the two ends of the cycle.« less

Heating/cooling systems

Abstract: A heating/cooling system includes a plurality of solid panels which form part of a wall or floor. The panels are in the form of heating/cooling modules and incorporate a heat exchange element within the panel and in thermal contact with the material, e.g. chipboard, fibreboard or plywood, forming the panel. The panels can be provided with, for example, tongue and groove formations so that they can engage with like panels or with "industry-standard" panels which do not incorporate heat exchange elements.

Method and apparatus for a self contained heat exchanger

Abstract: A self contained heat exchanger useful for reducing the operational temperature of a solid state device utilizing mixtures of two or more coolants within a hermetically sealed chamber or chambers. The present invention includes embodiments that are useful for removing heat from a semiconductor electronic device. The present invention provides a low boiling point coolant that boils at the operational temperatures of the semiconductor devices to agitate a higher boiling point coolant that remains in liquid state. Movement of the higher boiling point coolant is instrumental in uniformly transferring heat from the heat source across metal radiator surfaces due to the excellent surface contact of the heat rich high boiling point liquid. The chamber surface then uniformly radiates the heat into the surroundings. At equilibrium, boiling action of the lower point liquid coolant and condensation on the metal surface create recirculation paths within the present invention that enhances heat transfer. The entire device may rest squarely on top of the semiconductor package and does not require any active mechanical components or external power or maintenance.

Heat pump type air conditioner for automotive vehicle

Abstract: A heat pump type air conditioner for an automotive vehicle has a compressor to which an outer heat exchanger and a first inner heat exchanger are connected through a three-way valve. The outer heat exchanger is connected at its refrigerant outlet to the first inner heat exchanger through one-way valve. The refrigerant outlet of the first inner heat exchanger is connected to a second inner heat exchanger through an expansion valve. The refrigerant outlet of the second inner heat exchanger is connected to the compressor. The second and first inner heat exchangers are disposed in turn downstream of a blower for generating an air flow for air-conditioning a passenger compartment of the vehicle. During a cooling drive the three-way valve is set to lead the refrigerant from the compressor to the outer heat exchanger. During a heating drive the three-way valve is set to direct the refrigerant from the compressor to the first inner heat exchanger while bypassing the outer heat exchanger. As a result, the air-conditioning capacity of the air conditioner is improved without changing the direction of refrigerant flow to the cooling and heating drive.

Computer component cooling system with local evaporation of refrigerant

Abstract: A cooling system for a computer system which includes at least one component which generates substantial thermal energy. The cooling system includes a heat exchanger formed of a thermally conductive material which is attached to the heat generating component, the heat exchanger including an internal expansion chamber. A first conduit provides a pressurized liquid refrigerant supplied from a refrigeration compressor unit to the expansion chamber, wherein the pressurized liquid refrigerant is evaporated absorbing heat from the heat exchanger and the attached heat generating component. A second conduit provides egress of the evaporated refrigerant from the expansion chamber, returning the evaporated refrigerant to the compressor. The first conduit has a smaller diameter than the second conduit and is placed coaxial with and within the second conduit. The coaxial arrangement of the first and second conduits serves two purposes. The evaporated coolant and the second conduit are heated through thermal contact with the first conduit containing pressurized liquid coolant having a higher temperature than the evaporated coolant, reducing the formation of condensation on the second conduit; and the pressurized refrigerant is pre-cooled prior to evaporation within the expansion chamber through thermal contact with the second conduit containing the evaporated coolant which has a lower temperature than the pressurized liquid coolant.

Internal combustion engine with cooling of intake air using refrigeration of liquefied fuel gas

Abstract: A turbocharged or supercharged internal combustion motive system for utilization of gaseous fuel stored as a liquid wherein the liquefied gaseous fuel is vaporized and warmed at least partially with heat removed from the compressed intake combustion air in the turbocharger or supercharger aftercooler In a preferred embodiment, the compressed intake combustion air is first cooled in an aftercooler against an ambiently cooled coolant and is subsequently cooled in further aftercooler heat exchange passages against an intermediate coolant which transfers heat removed from the compressed intake combustion air to the liquefied gaseous fuel Embodiments are disclosed wherein the saturated liquefied gaseous fuel is first subcooled and then pumped to pressures high enough for direct combustion chamber injection and another embodiment discloses vaporization of the saturated liquefied gaseous fuel with compression of the vaporized gas in a compression-type injection system or by low pressure carburetion into the internal combustion engine

Air conditioning and refrigeration systems utilizing a cryogen

Abstract: Methods and apparatus for controlling the tempera-ture of a conditioned space, including a supply of cryogen, and a fluid flow path for the cryogen which includes a heat exchanger. A heater is disposed to heat cryogen in the flow path in response to predetermined conditions, and a cryogen pre-heater is disposed to aid the heater. In a first embodiment, the pre-heater is aided by directing warm cryogen in heat exchange relation with cryogen flowing through the pre-heater, with the warm cryogen being taken from a point downstream from the heat exchanger. In another embodiment, the heater generates heated gases as a by-product, with the pre-heater being aided by directing the heated gases in heat exchange relation with cryogen flowing through the pre-heater.

Method for liquefying natural gas

Abstract: Provided is a method for liquefying natural gas which can be readily adapted to LNG plants of all sizes without requiring expensive and special heat exchangers. The liquefaction of feed gas of natural gas and recycle natural gas is carried out with a single-component refrigerant or a mixed refrigerant in a high temperature stage, and with a substantially isentropic expansion in a low temperature stage, and a non-liquefied part of the recycle gas after the expansion step is pressurized with a compressor and recycled along with a recycle stream of non-liquefied par of the feed natural gas, the liquefied part by the refrigerant exchanging heat with the non-liquefied part stream produced from the substantially isentropic expansion, in a plate-fin heat exchanger or the like. The compressor is driven by the power obtained by the substantially isentropic expansion.

Integrated plate-fin heat exchange reformation

Abstract: The present invention is a reformation process using a compact, plate-fin heat exchanger with multi-stream, multi-passage capability to provide parallel juxtaposed heat exchange of the various process streams of a reformation process.