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P1 approximation of spherical harmonics method PACKED BED PACKED BEDS, WETTING PACKED COLUMN CHROMATOGRAPHY PACKED JOINTS PACKED SCRUBBER PACKED TOWERS PACKING IN REGENERATORS PACKING, COLUMNS Paint coatings containing hollow glass microspheres PAIR PRODUCTION PARABOLIC DIFFERENTIAL EQUATIONS PARABOLIC EQUATIONS PARADOX ABOUT THE PROPAGATION OF THERMAL ENERGY SPEED IN A SEMI-INFINITE BODY HEATED BY A FORCED CONVECTIVE FLOW PARAFFIN PARALLEL COMPUTATIONAL CODE Parallel implementation Parallel plates, radiative heat transfer between PARAMETRIC DOMAIN MAP PARSONS, CHARLES PARTIAL PRESSURE PARTIALLY SOLUBLE LIQUIDS PARTIALLY-IONIZED GAS DYNAMIC FLOW PARTICLE CHARACTERIZATION PARTICLE CONCENTRATION MEASUREMENT PARTICLE COUNTING PARTICLE DEPOSITION PARTICLE DIAMETER, EQUIVALENT VOLUME SPHERE PARTICLE DIAMETER, MEAN VALUES PARTICLE FLOW, IN NOZZLES PARTICLE IMAGE VELOCIMETRY, PIV Particle size measurements PARTICLE SIZE PARAMETER PARTICLE TECHNOLOGY PARTICLE TRACKING VELOCIMETRY PARTICLE TRANSPORT IN TURBULENT FLUIDS PARTICLE VELOCITY RESPONSE TIME PARTICLE WALL COLLISIONS PARTICLE-LIQUID SEPARATION PARTICLE-PARTICLE INTERACTIONS PARTICLES IN LIQUID PARTICLES, DRAG AND LIFT PARTICLES, RADIATIVE PROPERTIES OF PARTICLES, SOLID IN LIQUID PARTICULATE COMPOSITES PARTICULATE FOULING PARTICULATE MEDIA PASQUILL CATEGORY PASSIVATION OF POLYCRYSTALLINE SILICON PASSIVE CONTAINMENTS, FOR NUCLEAR REACTORS PASSIVE PLUME PASSIVE SAFETY FEATURES PASSIVE SOLAR DESIGN OF BUILDINGS PASSIVE SOLAR WATER HEATER PAULI EXCLUSION PRINCIPLE PDA PEAK HEAT FLUX PECLET NUMBER PECLET NUMBER EFFECT IN LIQUID-METAL HEAT TRANSFER PECLET, JEAN CLAUDE EUGENE (1793-1857) PELTIER EFFECT PELTIER REFRIGERATOR PELTON TURBINES PENETRATION OF A DROPLET ONTO A POROUS SUBSTRATE PENG-ROBINSON EQUATION PENMAN EQUATION FOR POTENTIAL EVAPORATION PENSTOCKS PENTANE PEPPER SPRAY PERFECT GAS PERFECT MIXTURES PERFORATED PLATES PERFORATED TRAYS PERFORATION PERIODIC KILNS PERIODIC SUCTION VELOCITY PERISTALSIS PERISTALTIC FLOW OF A TWO-LAYER SYSTEM PERMANENT MOULDING PERMEABILITY PERMEABILITY COEFFICIENT PERMEABILITY OF VACUUM PERMEATE PERMITTIVITY PERMITTIVITY OF VACUUM PERTURBATION METHODS PERVAPORATION PETROCHEMICALS PETROL PETROL ENGINES PETROLEUM PETUKHOV AND KIRILLOV CORRELATION FOR HEAT TRANSFER PETUKHOV-POPOV CORRELATION PHASE PHASE DOPPLER ANEMOMETERS PHASE DOPPLER ANEMOMETRY, FOR SIMULTANEOUS VELOCITY AND DROP SIZE MEASUREMENT PHASE DOPPLER ANEMOMETRY, PDA PHASE EQUATIONS PHASE EQUILIBRIA PHASE EQUILIBRIUM PHASE INVERSION PHASE RULE Phase separation overview PHASE SPACE PHASE TRANSITIONS PHASE VELOCITY PHASE VELOCITY, AVERAGE PHENOL PHENOMENOLOGICAL MODELS PHONONS, IN THERMAL CONDUCTIVITY OF SOLIDS PHOSPHORESCENCE PHOSPHORIC ACID PHOSPHORUS PHOTO CORRELATION SPECTROSCOPY PHOTO ELECTRIC EFFECT PHOTOCHROMIC DYE TRACING PHOTOCONVERSION PHOTODIODE ARRAYS PHOTOGRAPHIC METHODS, FOR DROPSIZE MEASUREMENT PHOTOGRAPHIC METHODS, FOR PARTICLE SIZING PHOTOGRAPHIC TECHNIQUES PHOTOGRAPHY PHOTOLUMINESCENCE PHOTOMULTIPLIERS PHOTONIC DEVICES PHOTONS PHOTORESPONSE OF METAL-POROUS SILICON-SILICON STRUCTURE PHOTOVOLTAIC EFFECT PHYSICAL ADSORPTION Physical basis of interaction between thermal radiation and turbulence Physical nature of thermal radiation Physical quantities used to characterize radiation of surfaces and media PHYSIOLOGY AND HEAT TRANSFER PI THEOREM PID, PROPORTIONAL-lNTEGRAL-DERIVATIVE CONTROLLERS PIEZOCERAMIC SHELLS PIEZOELECTRICITY PIEZOMETRIC HEAD LINE PIEZOMETRIC LINE PIG IRON PIN-FIN TYPE HEAT SINKS PINCH DESIGN METHOD PINCH POINT PINCH TECHNOLOGY OR PINCH ANALYSIS PIPE FILTERS PIPE JUNCTIONS PIPELINE SAMPLING PIPELINES PIPELINES, HIGH PRESSURE GAS PISTON ENGINES PITOT STATIC TUBE PITOT TUBE PITZER AND CURL RELATIONSHIP PLANCK'S FUNCTION PLANE POTENTIAL FLOW PLANIMETRY PLASMA PLASMA ARC FURNACE PLASMA DISCHARGE PLASMA PHOTOELECTRIC CONVERTER PLASMA PROCESSING OF CONCRETE AND RELATED MATERIALS Plasma radiation and applications PLASMA ROCKET ENGINES Plasma spectra at LTE (examples for some particular plasmas) PLASMA THERMAL CONDUCTIVITY PLASMA TORCH PLASMA TUBE PLASMATRON PLASTICITY IN MONOCRYSTALS PLASTICS PLATE AND FRAME HEAT EXCHANGERS PLATE EVAPORATORS PLATE FILTERS PLATE FIN HEAT EXCHANGERS PLATE HEAT EXCHANGERS PLATE THEORY OF CHROMATOGRAPHY PLATE TYPE CONDENSERS PLATE-FIN EXTENDED SURFACES PLATINUM PLATINUM RESISTANCE THERMOMETER PLESSET AND ZWICK EQUATION, FOR BUBBLE GROWTH Plug flow PLUG FLOW HEAT TRANSFER PLUMES PLUNGING JET Plunging liquid jets PLUTONIUM PLUTONIUM 239 PLUTONIUM, BURNING IN FAST REACTOR PNEUMATIC TRANSPORT POD BOILERS POISEUILLE EQUATION Poiseuille Flow POISEUILLE LAW POISSON EQUATION POISSON STATISTICS POISSON'S RATIO POLARIZATION POLARIZATION METHOD, FOR DROPSIZE MEASUREMENT POLARIZED RADIATION POLLUTANTS POLLUTION POLLUTION CONTROL POLYCRYSTALS POLYDISPERSION POLYETHYLENE POLYMER PROTON EXCHANGE MEMBRANE POLYMER SEPARATION POLYMERIC COMPOSITES POLYMETS POLYMORPHS POLYNOMIALS POLYSTYRENE ANION EXCHANGE RESINS POLYSTYRENE SULPHONIC ACID CATION RESINS POLYTROPIC INDEX POLYTROPIC PATH POLYTROPIC PROCESS POOL BOILING POOL BOILING IN MICROGRAVITY AND IN ELECTRIC FIELDS POOL BOILING OF LIQUID METALS POOL FIRES POPULATION BALANCE, CRYSTALS POROSITY POROSITY MODEL OF BRANCHED PIPEWORK POROUS BODIES, DIFFUSION IN POROUS CATALYSTS POROUS CAVITY POROUS COATINGS, FOR INCREASING BURNOUT FLUX POROUS ENCLOSURE POROUS LAYER POROUS MATRIX OF VARIABLE THICKNESS POROUS MEDIA, HEAT TRANSFER IN POROUS MEDIA, HYDRAULIC LOSSES IN POROUS MEDIUM POROUS METALLIC FOAMS POROUS SHELL FILLED WITH HELIUM II POROUS WALL COOLING POROUS WEDGE POSISTOR RESISTANCE THERMOMETERS POSITIVE CATALYSIS POST DRYOUT HEAT TRANSFER POST-DRYOUT HEAT TRANSFER POTABLE WATER POTASSIUM POTASSIUM CARBONATE POTENTIAL FLOW POWER FLOWMETERS POWER LAW FLUIDS POWER NUMBER POWER PLANTS POWER SERIES POWER SPECTRUM PRA, PROBABILITY RISK ASSESSMENT PRANDTL NUMBER PRANDTL TUBE PRANDTL'S BOUNDARY LAYER PRANDTL'S FORMULA, FOR FRICTION FACTOR PRANDTL'S MIXING LENGTH MODEL PRANDTL, LUDWIG (1875-1953) PRANDTL-MEYER RELATIONSHIP PRECIPITATION PREHEATERS PREMIXED FLAMES PRESSURE PRESSURE AVERAGES PRESSURE DIE-CASTING PRESSURE DROP IN BENDS PRESSURE DROP IN CIRCULAR PIPES PRESSURE DROP IN COILED TUBE PRESSURE DROP IN FLUIDIZED BEDS PRESSURE DROP MULTIPLIERS PRESSURE DROP OSCILLATIONS Pressure Drop, Single-Phase Pressure Drop, Two-Phase Flow PRESSURE DUE TO RADIATION PRESSURE EFFECTS ON BOILING PRESSURE GRADIENT PRESSURE GRADIENT IN ANNULAR FLOW PRESSURE GRADIENT, COMPONENTS OF IN MULTIPHASE FLOW PRESSURE INDUCED FLOW PRESSURE MEASUREMENT PRESSURE NOZZLES PRESSURE OF BLOOD OF A STENOTIC ARTERY PRESSURE PRISMS PRESSURE SUPPRESSION PRESSURE SUPPRESSION CONTAINMENTS, FOR NUCLEAR REACTORS PRESSURE TRANSDUCERS PRESSURE VESSEL DESIGN CODES PRESSURE VESSELS PRESSURE WAVES PRESSURE-SWIRL NOZZLES PRESSURIZED WATER REACTORS, PWR PRESTON TUBE PRILLING PRILLING TOWERS Primary quantity PRIMARY RECOVERY PROCESS PRINTED CIRCUIT HEAT EXCHANGER PROBABILITY DENSITY FUNCTION, PDF PROBABILITY THEORY PROCESS PROCESS CONTROL PROCESS HEATERS PROCESS INTEGRATION PRODUCER GAS PROFILE METHOD OF SURFACE HEAT BALANCE PROFILING, OPTICAL TECHNIQUE PROPANE PROPELLANTS PROPERTIES OF MATERIALS Properties of real surfaces PROPYLENE PROTONS PSA, PROBABILITY SAFETY ASSESSMENT PSEUDO CRITICAL TEMPERATURE PSEUDO FILM BOILING PSEUDO HOMOGENEOUS FLOW PSEUDO-SOUND PSEUDOPLASTIC FLUIDS PSYCHROMETER PSYCHROMETRIC CHART PSYCHROMETRIC RATES PSYCHROMETRIC RATIO PULSATILE FLOW IN AN ARTERY MODEL PULSATING CAPILLARY HEAT PIPE PULSATIONS PULSE HEATING PULSED CAPILLARY DISCHARGE WAVEGUIDES PULSED COLUMNS PULSED LASERS PULSED THERMAL ANEMOMETERS PULSED THERMOGRAPHY PULSED TWO-PHASE FLOW PULVERIZED COAL COMBUSTION PULVERIZED COAL FURNACES PULVERIZED FUEL, PF PUMPED STORAGE PURIFICATION PURIFICATION OF METALS PUSHER CENTRIFUGE PUSHKINA AND SOROKIN CORRELATIONS, FOR FLOODING PVT RELATIONSHIPS PYRIDINE PYROLYSIS PYROMETALLURGY PYROMETRY, RADIATION
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PLATE FIN HEAT EXCHANGERS

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History

Aluminum alloy plate fin heat exchangers have been used in the aircraft industry for 50 years and in cryogenics and chemical plant for 35 years. They are also used in railway engines and motor cars.

Stainless steel plate fins have been used in aircraft for 30 years and are now becoming established in chemical plant.

Concept

The concept is shown in Figure 1 . Corrugated metal fins are placed between flat plates. The structure is joined together by brazing (see later). The fins have the dual purpose of holding the plates together, thus containing pressure, and of forming a secondary (fin) surface for heat transfer. At the edges of the plates are bars, which contain each fluid within the space between adjacent plates.

The heights of corrugations and bars may vary between plates, as shown. For a liquid stream we can use a low height corrugation, matching high heat transfer coefficient with lesser surface area while for a low pressure stream we can use a high corrugation height, matching low coefficient with higher surface area but also giving larger through area to achieve lower pressure drop. An industrial unit contains about 1000 m2 of surface per cubic meter.

Basic construction of plate fin units. (By courtesy of I.M.I. Marston Ltd.)

Figure 1. Basic construction of plate fin units. (By courtesy of I.M.I. Marston Ltd.)

Aluminum units can be made up to 1.2 m × 1.2 m cross section and 6.2 m long.

Stainless steel units can be made up to 500 mm × 500 mm cross section × 1500 mm length.

Corrugations (Fins)

Corrugations are also made with heat transfer enhancement devices. Standard forms are shown in Figure 2 . Characteristics are shown in Figure 3 .

Plain corrugation is the basic form and is used normally for low pressure drop streams.

Perforated corrugation shows a slight increase in performance over plain corrugation, but this is reduced by the loss of area due to perforation. The main use is to permit migration of fluid across fin channels, usually in boiling duties.

Serrated corrugation is made by cutting the fins every 3.2 mm and displacing the second fin to a point half way between the preceding fins. This gives a dramatic increase in heat transfer.

Herringbone corrugation is made by displacing the fins sideways every 9.5 mm to give a zig-zag path. Performance is intermediate between the plain and serrated forms. The friction factor continues to fall at high Reynolds numbers, unlike the serrated, showing advantages at higher velocities and pressures.

The designer can, therefore, vary fin heights, fin pitch and fin thickness together with four standard fin types giving great versatility of design.

Construction

Plate-fin units are normally arranged for counterflow heat exchange. Cross flow units are used for vehicle radiators and cross counterflow is used for liquid subcoolers.

Figure 4 shows the typical layer arrangements for a three-stream heat exchanger. A two-stream exchanger can be constructed by using the first of the arrangements shown for the hot stream, alternating with the second arrangement shown for the cold stream.

In this way, the heat exchanger is built up to the appropriate height. It is then brazed together; headers and pipework are welded over the inlet and outlet parts of each stream to give a finished unit. Layers are normally arranged with alternating hot and cold streams, as below:

An alternative system, called double banking, is sometimes used, as below:

A three-stream unit is made by using all the fin arrangements shown in Figure 4.

Figure 5 gives a drawing of a five-stream heat exchanger. This has "cut away" sections to show components, one of which shows the method used for stream distribution using an end entry inlet. When several cold streams are used in one unit the layers of each stream should be evenly disposed across the stack height.

Types of corrugation. (By courtesy of I.M.I. Marston Ltd.)

Figure 2. Types of corrugation. (By courtesy of I.M.I. Marston Ltd.)

Characteristics of plate fin surfaces.

Figure 3. Characteristics of plate fin surfaces.

Layer arrangement for 3 stream units. (By courtesy of I.M.I. Marston Ltd.)

Figure 4. Layer arrangement for 3 stream units. (By courtesy of I.M.I. Marston Ltd.)

Figure 6 shows a method by which a stream which occupies layers at one end of a block can be taken out at part length and replaced by a second stream at the other end of the block. This can be repeated and in ethylene exchangers up to 5 streams occupy the same layers for different lengths.

A variation of the system allows part of a stream to be taken out (or added) at part length. The use of all these features permits a high degree of process intensification in a single block. The maximum number of streams in one block, so far, is ten, of which three had partway take-offs or additions.

Brazing and Materials

Aluminum units use material AS3003 in the exchanger block. Braze material is AS3003 + silicon. Plates are purchased with a thin film of braze metal on both sides. The unit is built and placed in a vacuum furnace. The braze takes place under vacuum and at a temperature of 580°C. The parts of the block are then firmly attached together.

AS5083 is used for headers and piping below 65°C. Above this temperature AS5454 is used.

Stainless steel units are made of AISI type 321. Braze material is essentially nickel and can be applied to the plates by spraying. Brazing takes place under vacuum at temperatures up to 1050°C.

Figure 5. 

Re-entrant layers.

Figure 6. Re-entrant layers.

Pressures and Temperatures

Aluminum units operate with design pressures up to 100 bars and at temperatures from absolute zero to 65°C. Above 65°C a change of header material will allow operation to 120°C with reduced design pressures. Stainless steel units are currently limited to 50 bars design pressure and temperatures up to 750°C.

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