P.8 / Heat Exchanger Tubes Heat Exchanger Tubes / p.9 The superior solution Titanium is becoming the most efficient and cost-effective mate-rial for an increasing number of applications. It offers unmatched.
APV ParaTube (tube-in-tube heat exchangers) can be supplied with either straight tubes or corrugated tubes. They all follow a similar construction format with a single tube or number of smaller tubes enclosed within an outer shell.
They are available in the four configurations and can be manufactured as a fully-welded design, with removable end caps or with built-in thermal expansion protection of O-rings or packing between the shell and tube bundle.Product range APV ParaTubeCorrugated Double Tube (CDT) - The APV ParaTube CDT consists of a single corrugated tube concentrically positioned in a larger diameter outer tube. Tube diameters vary according to flows and the size of any particulates which may be present. The double tube offers a completely unrestricted flow path down the center tube. This design makes them particularly well suited for heating or cooling products with very high pulp or fiber content, or products which contain a substantial quantity of particulates which must be processed with a minimum loss of identity.Corrugated Triple Tube (CTT)The APV ParaTube CTT consists of a center tube concentrically positioned in a middle tube which is concentrically located in the outer tube. Stainless steel spacers are used to keep the tubes properly separated. The result is an annular space where heat transfer effectively occurs from both sides. The triple tube is generally applied to high viscosity or Newtonian fluids which may or may not contain small fibers or particulates.Corrugated Quadruple Tube (CQT)The APV ParaTube CQT is a unique design that allows significant flexibility in annulus gap to optimize heat transfer and pressure drop.
It allows balancing of flow rates and pressure drop ratios between the inner and outer annulus. This feature is critical to successful heat transfer of laminar and/or non-Newtonian fluids, particularly when applying it to product-to-product regeneration.Corrugated Multi Tube (CMT)The APV ParaTube CMT consists of smaller diameter corrugated tubes aligned in parallel within a larger diameter outer shell.
Because of the number of tubes within a shell, this design maximizes heat transfer surface in a given volumetric space. The CMT is ideal for heating or cooling duties of lower viscosity products or those containing whole juice cells or pulp. Regeneration is indirect, and we can provide conical tubesheet on the inlet of each module for juice with some pulp.Features/Benefits:.
Working temperatures up to 545°F/285°C. Design pressures to 871 psig/60 bar. Flexibility in materials of construction from carbon steel to special alloys. High particulate capacities. Can handle high viscosity products. Resistant to fouling.
Robust. Easy maintenance.
RMP Lecture NotesShell and Tube Heat Exchangers: CalculationsThe basic design calculation for any heat exchanger is the determinationof heat transfer area. Most generally, this is done usingalthough in practice it is more common to assume that fluid propertiescan be treated as constant at the bulk average values, and approximatethe design equation with:To use this equation, it is necessary to determine the heat transfercoefficient and the temperature difference. We have seen that for adouble pipe heat exchanger the required average temperature differenceis the log mean temperature difference (LMTD). Unfortunately, the flowpatterns in shell and tube exchangers are such that the LMTD by itselfis no longer adequate. It must first be adjusted by means of acorrection factor.The second parameter that must be calculated for a typical processdesign is the pressure drop in the fluids moving through the exchanger.Correcting the LMTDThe LMTD was developed for a model restricted to parallel andcountercurrent flow patterns.
In shell and tube exchangers, the flowpattern is a mixture of cocurrent, countercurrent, and crossflow, so theLMTD does not directly apply. Instead, a corrected LMTD mustbe used. Correction factors ( F correction factors) aretabulated and used to adjust:The correction factor charts are available from many sources (Levenspiel Fig13.5-10; Brodkey & Hershey Fig 11.16; MSH6 Fig 15.6). They are based ontwo parameters:These parameters are cross-referenced on the appropriate chart to findthe F factor. A different chart is needed for each exchanger layout (1-2, 1-4, etc.). Note that the charts provided in MSH are written usinghot and cold subscripts and assume that the hotfluid is on the shell side of the exchanger. Be careful and do what isright for your problem.F factor curves drop off rapidly below 0.8.
Consequently, if yourdesign is indicating an F less than 0.8, you probably need to redesign(add tube passes, increase temperature differences, etc.) to get abetter approximation of countercurrent flow and thus higher F values.Similar correction factors are available for exchanger types other thanshell and tube, including crossflow and compact exchangers.Tube Side Heat Transfer CoefficientsTube side heat transfer coefficients are easy to determine, since theSeider-Tate equation (or equivalent) applies. The most common slipupmade at this stage is to incorrectly divide the stream flow among thetubes. Be sure to adjust all flowrates and velocities for the number oftubes AND the number of tube passes.
If an exchanger has 200 tubes in 2passes, the total flow will be moving through 100 tubes at a time; ifthere are 4 passes, it will go through 50 tubes.Tube Side Pressure DropTube side pressure drop is calculated using the same pipe flow factorsdeveloped in your fluid mechanics class. Again, be careful to dividethe total flow among the correct number of tubes.
The isothermalfriction factor can be obtained from the Moody/Stanton charts or anappropriate correlation.This friction factor must be corrected for the effect oftemperature on viscosity. 115-16 explains correction factors,but you can probably get good enough results using the Seider-Tateviscosity correction:This can then be used with the mechanical energy balance to get thepressure drop:Shell Side Heat Transfer CoefficientsShell side heat transfer coefficients cannot be obtained from Seider-Tate, etc., since the flow patterns and many other factors don't match.For this class, you should use the Donohue correlations (MSH6 eq.