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Transcript of Types of Heat Exchangers and LMTD Design Methodpdf)-日間/8.1.pdf · Shell-and-Tube Heat Exchanger...
Types of Heat Exchangers and LMTD Design Method
Professor Jung-Yang San
Mech. Engrg. Dept., National Chung Hsing University
(1) Types of Heat Exchangers
Counter-flow Double-Tube Heat Exchanger
Shell-and-Tube Heat Exchanger
(Two Tube Passes& One Shell Pass)
Shell-and-Tube Heat Exchanger (Single Pass)(Condenser/Evaporation)
Compactness? Material Weight Minimization? Reduction of Manufacturing Cost?
Shell-and-Tube Heat Exchanger (Single Pass)
TEMA
(Tubular Exchanger Manufacturers Association)
Assembly of the Core of a Shell-and-Tube Heat Exchanger
baffles
86 !
A Shell-and-Tube Heat Exchanger with Floating Head
Baffle Types in Shell-and-Tube Heat Exchangers
Baffle Cut
0.2 ~ 0.35 D
(Shell Diameter)
Flow Patterns for Different Baffle Cuts
Optimum Baffle Spacing 0.3 D ~ 0.6 D
Helical Baffle
One of The Largest Helical Baffle Exchanger Ever Built
- 12,000 fin tubes: 22 m long- Shell I.D.: 3.8 m- Shipping Weight: 165 Tons
Flat-Tube Cross-Flow Heat Exchanger
Flat-Tube Heat Exchanger with Fins Car Radiator
Helical Coil Heat Exchanger
Single tube helical coil heat exchangers are suited for oil coolers, sump coolers and other high pressure, high temperature, low flow applications.
Pressure ratings up to 345 bar and sample conditions up to 540CCompact and lightweight Highly resistant to thermal and pressure shockStandard 316 SUS construction with other exotic materials available
Helical Coil Heat Exchanger
Special Double Pipe Heat Exchanger
Plate Heat Exchanger
Heat Pipe Heat Exchanger
Spiral heat exchanger
HELICAL COIL HEATER
Twisted TubeTechnology
Tube Bundles
baffles
(tube bank heat exchanger)
Cross Flow Heat Exchanger (SUS 304)
NCHU
Cross Flow Heat Exchanger (made of pp sheets)
Spacing = 2 ~ 5 mm ; Operating temperature < 900CSheet thickness = 0.1 mm ; k (pp-sheets) = 0.12 W/m-K
Core: 300 x 300 x 150 mm (pp) Hot air inlet temperature = 30C Cold air inlet temperature = 15C
Cross-flow micro heat exchanger
Channel dimensions: 100 x 70 m, 200 x 100 m, 200 x 200 mSpecific inner surface up to 30,000 m2 m-3Heat exchange coefficient up to 20,000 W/mKPressure resistance > 100 barLeak rate (Helium) 10-8 mbar (l s)-1Temperature resistance: up to 850CMaterial: Stainless (DIN 1.4301, 1.4435), Hastelloy,
Outer dimensions: 80 x 80 x 25 mm 115 x 115 x 35 mm 200 x 200 x 45 mm
Inner volume per passageUp to 0.3 cm Up to 2 cm Up to 6 cm
Thermal power (water)Up to 20 kW Up to 50 kW Up to 200 kW
Throughput (water at P = 5 bar) Up to 1100 kg/h Up to 3500 kg/h Up to 6500 kg/h
Connectors:Swagelok 8 mm Swagelok 18 mm Swagelok 25 mm
Co/counter-current micro heat exchanger
Specific inner surface up to 30.000 mm-3Heat exchange coefficient up to 20.000 W/mKPressure resistance > 100 barLeak rate (Helium) 10-8 mbar (l s)-1Temperature resistance: up to 850CMaterial: Stainless (DIN 1.4301, 1.4435), Hastelloy,
High throughput micro reactor for chemical production
The main element at the production site, i.e. the micro reactor, is made from a nickel alloy and is 65 cm long and 290 kg in weight. The possible throughput is 1700 kg/h of liquid reactants. The heat released by the chemical reaction, approx. 100 kW is transferred within the reactor to again several ten thousands of micro channels at the cooling passage.
Micro heat exchanger for coffee production
A micro heat exchanger of only 8 cm3 in size is working in a plant for coffee production. Purpose: Cooling of liquid CO2 .
Fabrication of Metallic Micro structured Devices
Glowing micro-structured foil stack during diffusion bonding
Micro-structured foil made of copper
Mechanical Micro Fabrication
Micro drill Micro cutter
The typical surface roughness is like Ra = 0.2 m.
Results of Mechanical Fabrication
Material Min. Aspect HollowProcess Groove Size Ratio Accuracy
Steel Milling 100 m 4 3 m 200 m 7-15
Non Ferrous Milling 50 m 1 (Carbide) 2 mAlloys Milling 100 m 1 (Diamond), 4 (Carbide)
The fabrication of metallic micro structured devices starts with processing of metallic foils.
Precision turning () and milling () are applied therefore and together with partners micro etching () and micro embossing () are carried out.
The micro structured metal plates are then stacked between two base plates and diffusion bonded under a well defined press capacity and temperature in vacuum. By this procedure a microstructured body is yielded, which comprises of thousands of microchannels.
Materials which can not be diffusion bonded can be joined by laser welding or soldering. However, these technologies are under development.
The joined micro structured body gets welded into a housing with tubes or fittings by electron beam welding, vacuum tight and pressure resistant.
Micro Fabrication
Packed-Bed Regenerator
Rotary Regenerator
Selection of Heat Exchangers
The proper selection depends on several factors: heat transfer rate cost (maintenance and power) pumping power size and weight type materials miscellaneous (leak-tight, safety and
reliability, quietness)
Heat Transfer Enhancement Techniques
Tube with Internal Fins and Tube with Internal Roughened Surface
Tubes Inserted with Twisted Tape and Coiled Spring
Secondary Flow Induced by Coiled Spring
Flow Disruption Caused by hiTRAN Wire Matrix Turbulator
Brazed, Soldered, Edge Tension, Stamped
Extrusion
Circular Tube with External Spiral Fins
Circular Tube with Internal and External Spiral Fins
Fin Height : 1.422 (mm)
Outside Diameter : 19.00 (mm)
Wall thickness : 1.32 (mm)
Copper-Nickel Alloys
Corrugated Tubes
(NCHU) -
d t
2 mm p
Tw
rotameter
Ta ,Po o
outlet
pump
water bath
water
inlet
air blower
1
test tube
Tw4 3 2Tw Tw
heater
Ta ,Pi i
surgetank
electricinverter
Correlation of Nu
International Journal of Heat and Mass TransferVol. 49, 2006, pp. 2965-2971JCR (Mechanical Engineering) : 7/106
Correlation of f
Correlation Results
40.26( / ) 1.44 10 Re0.0018( / ) (Re)p d xf e d e e =
42.55 0.26( / ) 1.44 10 Re0.132( / ) (Re)p d xf e d e e =
1.05 0.15 0.3330.0072(Re) ( / ) ( / )Nu p d e d=
0.015 / 0.057e d