Showing papers on "Heat exchanger published in 1994"

Principles of Enhanced Heat Transfer

Abstract: Heat Transfer Fundamentals Performance Evaluation for Single-Phase Flows Performance Evaluation Criteria for Two-Phase Heat Exchangers Plate-and-Fin Extended Surfaces Externally Finned Tubes Insert Devices for Single-Phase Flow Internally Finned Tubes and Annuli Integral Roughness Fouling on Enhanced Surfaces Pool Boiling Vapor Space Condensation Convective Vaporization Convective Condensation Enhancement Using Electric Fields Simultaneous Heat and Mass Transfer Additives for Gases and Liquids Problem Supplement Index.

Process heat transfer

Abstract: Process Heat Transfer presents comprehensive coverage of both classical and new topics on the subject. Classical aspects discussed include shell-and-tube heat exchangers, double pipe exchangers, reboilers, and condensers. New topics covered include process integration, heat exchanger selection, heat transfer associated with thermodynamic cycles, and ohmic heating. The book includes both worked examples and problems at the end of each chapter. Extensive sections on the fundamental principles of heat transfer and fluid flow, in addition to a wealth of material on applied techniques and problems, make Process Heat Transfer an invaluable text/reference for students and professionals in mechanical engineering, chemical engineering, and applied heat transfer. "In summary, the essential usefulness of this book is as a 'one-stop' source of information on the basic theory and mechanism of heat transfer, typical correlations and methods for use in thermal design, and all types of modern process heat transfer equipment...the book represents very good value and can certainly be recommended as a textbook for general courses on process heat transfer...it will also be very useful as a general source book for the practicing engineer who needs access to a wide range of information on process heat transfer in a single volume...." - From a review in Heat Transfer Engineering 1042 pages, © 1994

Chemical process design

Abstract: The hierarchy of flowsheet synthesis choice of reactor choice of separator the synthesis of reaction-separation systems distillation sequencing heat exchanger network and utilities - energy targets, capital and total cost targets economic trade-offs safety and health considerations waste minimization heat exchanger network design overall strategy for flowsheet synthesis preliminary economic evaluation heat exchanger network area target number of shells target for heat exchanger capital cost target for heat exchanger networks.

Active thermal control of ultrasound transducers

Abstract: An ultrasound transducer assembly having a housing, a transducer array mounted in the housing, and active cooling mechanism positioned adjacent to the transducer array for actively removing heat generated by the array by transport of heat energy from the affected site. The active cooling mechanism may comprise a heat exchanger including a closed loop circulating coolant system circulating coolant, or a single-pass flowed coolant, passing through the heat exchanger, a heat pipe, a thermoelectric cooler, an evaporative/condenser system, and/or a phase change material. One or more heat exchangers may be used having gas or liquid coolants flowing therethrough. The heat exchangers and coolant pumps may be located in various components of the transducer assembly, including the array housing, the connector assemblies or the ultrasound console.

Variable temperature seat climate control system

Abstract: A temperature climate control system comprises a variable temperature seat (10), at least one heat pump (26 and 28), at least one heat pump temperature sensor (54 and 56), and a controller (64). Each heat pump comprises a number of Peltier thermoelectric modules for temperature conditioning the air in a main heat exchanger (34 and 36) and a main exchanger fan (42 and 44) for passing the conditioned air from the main exchanger to the variable temperature seat. The Peltier modules and each main fan may be manually adjusted via a temperature switch (60) and a fan switch (58), respectively. Additionally, the temperature climate control system may comprise a number of additional temperature sensors (102 and 104) to monitor the temperature of the ambient air surrounding the occupant as well as the temperature of the conditioned air directed to the occupant.

Automotive air conditioner having condenser and evaporator provided within air duct

Abstract: An automotive air conditioner which conditions air making use of radiation of heat of a condenser and absorption of heat of an evaporator effectively. The evaporator 207 and the condenser 203 are disposed in a duct 100. A bypass passageway 150 is provided sidewardly of the condenser 203 in the duct 100, and a flow rate of air bypassing the condenser 203 is controlled by pivotal motion of an air mixing damper 154. Another bypass passage is provided sidewardly of the evaporator 207 in the duct 100, and a flow rate of air bypassing the evaporator 207 is controlled by pivotal motion of a bypass damper 159. Air is conditioned to an optimum blown out air temperature by varying the cooling rate at the evaporator 207 and the heating rate at the condenser 203 and is blown out to a room of an automobile from spit holes 141, 142 and 143. An outside heat exchanger is provided outside the duct 100, and a flow of refrigerant is changed over suitably among the outside heat exchanger 202, the evaporator 207 and the condenser 203 to perform cooling operation, heating operation, dehumidifying operation, dehumidifying heating operation and defrosting operation.

Evaluation of suction-line/liquid-line heat exchange in the refrigeration cycle

Abstract: The paper presents a theoretical evaluation of the performance effects resulting from the installation of a liquid-line/suction-line heat exchanger (LLSL-HX). It examines cycle parameters and refrigerant thermodynamic properties that determine whether the installation results in improvement of COP and volumetric capacity. The study shows that the benefit of application of the LLSL-HX depends on a combination of operating conditions and fluid properties — heat capacity, latent heat, and coefficient of thermal expansion — with heat capacity being the most influential property. Fluids that perform well in the basic cycle are marginally affected by the LLSL-HX, and the impact on the coefficient of performance and volumetric capacity may be either positive or negative. Fluids performing poorly in the basic cycle benefit the from LLSL-HX installation through increase of the coefficient of performance and volumetric capacity.

An improved liquefied natural gas fueled combined cycle power plant

Abstract: A process and system which improves the capacity and efficiency of a combined cycle power plant. An LNG supply system fuels the combined cycle plant. Gasified LNG in a combustor mixes with the air from the air compressor to provide the hot combustion gas for the gas turbine. The expanding LNG is used to chill a primary heat exchange fuid, e.g. water, which primary heat exchange fluid cools and densifies the intake air for the air compressor. Subsequently, the primary heat exchange fluid is used to condense the spent steam discharged from the steam turbine. The primary heat exchange fluid is then re-chilled and recycled to cool and densify the intake air.

Comparison of correction factors for shell-and-tube heat exchangers with segmental or helical baffles

Abstract: Heat transfer and pressure drop correction factors based on the Bell-Delaware method have been compared for an optimized segmental baffle heat exchanger and a helical baffle heat exchanger. In general, the results showed that properly designed helical baffles offer a significant improvement in heat transfer while providing a reduced exchanger pressure drop. The enhancement in heat transfer for helical baffles was reflected by the so-called turbulence enhancement correction factor, which accounted for the increase in heat transfer observed at a critical baffle inclination angle of 25°. As the baffle inclination angle was increased beyond this critical angle, the turbulence enhancement factor continued to increase and eventually produced a maximum heal transfer enhancement of 1.39 times that for ideal cross-flow conditions. The reduction in pressure drop due to the helical baffles was found to vary from 0.26 to 0.60 depending on the helical inclination angle.

Heat Exchange Effectiveness and Pressure Drop for Air Flow Through Perforated Plates With and Without Crosswind

Abstract: Low-porosity perforated plates are being used as absorbers for heating ambient air in a new type of unglazed solar collector. This paper investigates the convective heat transfer effectiveness for low-speed air flow through thin, isothermal perforated plates with and without a crosswind on the upstream face. The objective of this work is to provide information that will allow designers to optimize hole size and spacing. In order to obtain performance data, a wind tunnel and small lamp array were designed and built. Experimental data were taken for a range of plate porosities from 0.1 to 5 percent, hole Reynolds numbers from 100 to 2000, and wind speeds from 0 to 4 m/s. Correlations were developed for heat exchange effectiveness and also for pressure drop. Infrared thermography was used to visualize the heat transfer taking place at the surface. 7 refs., 13 figs.

Fast changing heating-cooling device and method.

Abstract: A method for creating a surface (13,20) having a fast changing temperature, comprises providing a heat exchanger (2) coupled to an orifice (3) opening into a jacket (4) which is in contact with the surface (13,20) to be heated and cooled, the said jacket (4) forming a reservoir capable of housing a fluid in contact with the surface (13,20) to be heated and cooled, and providing two gas sources, each gas source being independently connected to the said heat exchanger (2), one source providing a first gas, which liquefies when it expands through the said orifice (3), and the other gas source providing a second gas, having an inversion temperature lower than the temperature obtained by the liquefaction of the first gas, and causing the exhaust gas flowing out from the said jacket (4), to flow through the said heat-exchanger (2) to preheat or precool the inflowing gas, as the case may be, and further causing the said first and the said second gas alternately to flow through the said heat exchanger (2) and orifice (3), to cool or to heat the said surface (13,20); means (10,11) being provided for allowing and stopping the flow of each gas through the said orifice (3).

Performance enhanced gas turbine powerplants

Abstract: A gas turbine driven powerplant having one or more compressors for producing a down stream air flow, a heat exchanger positioned down stream of the compressors followed by a side stream flow coolant line, a regenerator positioned down stream of the heat exchanger and side stream coolant line, a combustor positioned down stream of the regenerator, one or more turbines positioned down stream of the combustor and mechanically coupled to the compressors, and a power turbine positioned down stream of the turbines. Combustible effluent flows through the heat exchanger and to the combustor, and air discharged from the compressors flows through the heat exchanger and to the coolant line and regenerator. Heat is transferred from the compressor discharge air to the combustible effluent, thereby producing cooling air and heating the combustible effluent. The heat exchanger can be a heat exchanger or a methane/steam reformer which produces a hydrogen-rich, low NO x , steam diluted combustible effluent. In further embodiments, a small portion of the cool air is combined with the recuperation water in a heat recovery unit to allow vaporization of the water throughout the initial portion of the heat exchange path and form a two phased feed of water and air to the combustor. Additionally, in all embodiments a portion of the cooled compressed air can be processed by a compressor/expander for providing coolant to the turbines, compressors, and auxiliary equipment.

Integrated reformer/cpn sofc stack module design

Abstract: A thermally integrated reformer (10) is located inside the stack furnace (12) housing stacks (14) of solid oxide fuel cells (16). The energy to support the endothermic reformation reaction converting hydrocarbon and water feedstock into hydrogen and carbon monoxide fuel is supplied by heat recovered from the oxidation process in the stack (14) of fuel cells (16). The source of hydrocarbons is desulfurized natural gas. Heat transfers to reformers (10) which may be incrementally shielded packed beds (30, 60) of the reactors (18, 19) of the reformer (10) by radiation from the stacks (14), furnace wall (38), or both and by forced convection from the exhausting airflow exiting the stack furnace (12). Temperature gradients in the reformer (10) may be controlled by selective (or incremented) radiation shielding (20) and by counterflow heat exchange to prevent excessive premature cracking in the reformer. Such an optimized design uses a minimum amount of catalyst, yet prevents carbonization from clogging interstices or otherwise rendering the catalyst or catalyst granules (32) ineffective. Alternatively sufficient catalyst may be provided to render the reformation process a heat-limited reaction. In this circumstance, the stacks (132) configured in a module (106) may transfer heat directly to a reformer (110) surrounding the module (106). The air may pass through a heat exchanger 108 or preheater (200) positioned proximate the module 106 in an insulated enclosure (102).

Plasma processing apparatus and method

Abstract: A plasma processing apparatus comprises a first passage opened in a top of suscepter at a peripheral area thereof, a first gas supply source for supplying heat exchange gas into a small clearance between the suscepter and a wafer through the first passage, a first vacuum pump for exhausting the clearance through the first passage, a second passage opened in the top of the suscepter at a center area thereof, a second gas supply source for supplying heat exchange gas into the clearance through the second passage, a second vacuum pump for exhausting the clearance through the second passage, and a controller for controlling the first and second gas supply sources and the first and second vacuum pumps independently of the others in such a way that backpressure caused in the second passage by the second gas supply source and vacuum pump can become lower than backpressure caused in the first passage by the first gas supply source and vacuum pump.

System for controlling the temperature of the air in a cabin for an engine-electric motor hybrid car

Abstract: A vehicle is provided with both an electric motor and an internal combustion engine for operating the vehicle. The vehicle is further provided with a duct for discharging air into a cabin of the vehicle for controlling the temperature of the air as discharged. A heater core is arranged in the duct for heating the air passing through the duct. A sensor 9 is provided for detection of the temperature of the cooling water of the engine. When the vehicle is operated by the electric motor, the heat taken from the engine cooling water is supplied to the heat exchanger for heating the air passing through the duct when the temperature of the engine cooling water is higher than a predetermined value.

Chemical-looping combustion power generation plant system

Abstract: A chemical-looping combustion method uses a metallic oxide (MO) as an oxygen carrier A fuel (RH) reduces MO at a low temperature in a first reactor, a reduced product (M) is oxidized by oxygen in moistened air in a high-temperature region in a second reactor to form MO which is recycled to the first reactor Heat generated within these reactors is utilized to drive gas turbines The reactions within the first and second reactors are: RH+MO→mCOsub2 +nHsub2 O+M (1) M+050sub2 →MO (2) Moistened air is the oxygen source in the second reaction The metallic oxides and their reduced products are particulates including an oxygen permeable medium The loss of energy in the conversion reactions and in heat exchange is reduced, power generation efficiency is improved, CO 2 is recovered and water resources are saved

Heat exchanger with oblong grommetted tubes and locating plates

Abstract: This invention relates to a heat exchanger having a core comprised of oblong shaped tubes having substantially flat longer sides and rounded shorter sides, the tubes being separated by and in contact with conventional wave-shaped external cooling fins. Locating plates are provided at both ends of the tubes to accurately align and to secure the tubes into position. The ends of the tubes are sealably secured to header plates by means of resilient grommets. The heat exchanger of the present invention provides better resistance to mechanical and thermal shocks than conventional heat exchangers having tubes soldered or brazed to the header plates and provides better cooling efficiency than heat exchangers having circular, grommetted tubes.

Ground source heat pump system comprising modular subterranean heat exchange units with multiple parallel secondary conduits

Abstract: An improved ground source heat pump system wherein the subterranean piping installation comprises modular heat exchange units. Each modular heat exchange unit comprises a plurality of parallel secondary or branch conduits. The use of multiple parallel secondary conduits significantly increases the heat exchange capacity of the system. Because of the increased efficiency of such a system, less piping is required, which in turn reduces the cost of labor and materials to install such a system and the area of land mass required to contain it. Moreover, because the heat exchange units are modular, they can be prefabricated at a remote site and then conveniently transported to construction site and installed much more quickly than the extended lengths of conventional piping.

Strategic modular commercial refrigeration

Abstract: A commercial refrigeration network (N) including refrigeration system units (10) constructed and arranged for placement in strategic proximity to corresponding product cooling zones (33) within the shopping arena (S) of a food store, each refrigeration unit having a condensing unit rack (20) configured to accommodate the maximum refrigeration loads of its associated zone with an optimum floor space footpring in the shopping arena, and the condensing unit rack including a plurality of multiplexed compressors (21), condenser (12) and associated high side and low side refrigerant delivery (22) and suction (31) conduits operatively connected to evaporators (29) for cooling the corresponding zone, and the network also including another cooling source (11) remote from said modular refrigeration units and constructed and arranged for circulating a fluid coolant in heat exchange relationship with the condenser to obtain optimum condensing and efficiency of said evaporators in cooling the corresponding zone.

Air conditioning system with thermal energy storage and load leveling capacity

Abstract: A vapor compression air conditioning (cooling and heating) system adapted for operation to reduce the consumption of electric power during peak periods of demand for power is characterized by three refrigerant circuits. A refrigerant circuit includes a compressor, outdoor heat exchanger and first indoor heat exchanger for selectively cooling or heating an indoor air space and a second refrigerant circuit comprises the compressor, outdoor heat exchanger and a thermal energy storage unit characterized by a tank having a thermal energy storage medium disposed therein and a heat exchanger coil in communication with the compressor and outdoor heat exchanger for cooling the thermal energy storage medium. A third refrigerant circuit includes the thermal energy storage heat exchanger coil, a refrigerant pump and another indoor heat exchanger in communication with the fluid (e.g., indoor air) to be cooled or heated. Plural isolation valves in the first and second refrigerant circuits, reversing valves in communication with the compressor and pump and a heater in the storage tank provide for operating the system in plural cooling and heating modes to provide cooling and heating with reduced power consumption during peak electrical power demand periods.

Method and apparatus for cooling hot fluids

Abstract: The cooling of a hot fluid is effected using a heat exchanger (11) adapted to receive the hot fluid and liquid coolant for cooling the hot fluid such that the liquid coolant is vaporized. A turbine (12), having an output shaft (19) connected to a fan (18), is responsive to vaporized coolant which expands in the turbine (12) for driving the fan (18) to move a mass of air, and produce vaporized coolant. A condenser (13) receives the expanded vaporized coolant and is responsive to air blown by the fan (18), for condensing the expanded vaporized coolant thereby cooling the same and producing coolant condensate which is then returned to the heat exchanger (11).

Device for air-conditioning the passenger compartment and for cooling the drive system of electric vehicles

Abstract: A device for air-conditioning the passenger compartment and for cooling the drive system of electric vehicles includes an air-guide duct connected on the inlet and outlet sides to the passenger compartment and having heat exchangers disposed one behind the other therein in the air-flow direction. One of the heat exchangers, which, together with a circulating pump and a cold store, is incorporated within a circuit of a cold-transporting medium. The circuit is run via the evaporator of a refrigeration unit. The other heat exchanger, together with a circulating pump and a heat store, is incorporated within a circuit of a heat-transporting medium. The circuit is run via the drive system of the electric vehicle for vehicle-cooling purposes. With the aim of reducing the weight of the device without altering the storage capacity of the cold and heat stores, these are formed by a single energy store, which, by at least one switchover valve, can be switched alternately into the cold-transporting-medium or heat-transporting-medium circuit. As the cold- and heat-transporting medium, the same liquid transmission medium is used.

Finite-time thermodynamic analysis of a radiative heat engine with internal irreversibility

Abstract: A relation between the design parameters of an internally and externally irreversible radiative heat engine is presented to find the maximum power and the efficiency at maximum power output. It was found that the ratio of the reservoir temperatures must be less than half of the cycle-irreversibility parameter and the ratio of area of the heat exchangers must be less than 1.0 for optimum thermal efficiency and maximum power output. Increasing the cycle-irreversibility parameter and the heat-transfer area of the cold side improve thermal efficiency and maximum power output.

Heat exchanger for thermoelectric cooling device

Abstract: Heat exchangers for a thermoelectric cooling (TEC) device. A heat dissipation assembly comprises an array of foil corrugations disposed in generally parallel spaced relationship with the heat dissipation plate of the TEC. The array of foil corrugations includes at least an inner and an outer bank of foil corrugations and at least one plate sandwiched therebetween and secured thereto by vacuum brazing thereacross. In this manner, heat conductivity is maximized for transfer of heat thereacross and from the TEC to the outer bank. A heat absorption assembly for use with the TEC comprises a thermal transfer plate having a teflon coated, serpentine fluid conduit therein facilitating the flow of a variety of fluids to be cooled therethrough without contamination thereof.

Refrigeration system and method for very large scale integrated circuits

Abstract: To dissipate heat generated internally in integrated circuit units, both an active refrigeration system and a passive refrigeration system are coupled to a heat sink that engages the integrated circuit unit. A cold probe insertable into the heat sink has an interior heat exchanger and receives high pressure but ambient temperature refrigerant which is subcooled and expanded to provide cold liquid refrigerant about the interior heat exchanger. As thermal energy from the circuit unit evaporates refrigerant, the refrigerant passes back to a power refrigeration unit for recirculation. A passive backup unit functions if the cold probe operation fails for some reason by boiling off a second refrigerant in a chamber at the heat sink and condensing the gases within a spaced apart air heat exchanger. Refrigerant that recondenses within the air heat exchanger flows by gravity back into the boil off chamber.