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Quotes - Engineering - SalesWhen the product has pieces in it
Tomato sauce with diced onion, salsa with 1/2 inch pepper, chunky soup, chili, fruit preparation with strawberry halves, baby food purees, pie filling, hummus, pet food slurry with meat chunks: none of these will pass a plate exchanger and all of them have to be heated, held and cooled continuously. The exchanger for this family is tubular with nothing in the product path but a smooth bore. A single tube-in-tube with a 2 or 3 inch inner tube handles pieces to 1/2 inch; a multi-tube with 1 to 1-1/2 inch tubes handles pieces to 1/4 inch at higher flow; a corrugated tube-in-tube handles purees with no pieces at all.
The design has to respect two facts that plates never had to. The largest piece sets the minimum bore, at least twice the piece dimension so two pieces cannot bridge. And the slowest particle sets the hold time, because in a viscous carrier at laminar flow a dense piece can lag the fluid, or in a thin carrier it can race ahead of it, and the holding tube has to be validated on the piece, not the sauce.
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Size the bore on the largest piece, not the sauce
A 1/2 inch pepper dice needs a 2 inch bore in practice, since pieces arrive in clusters. Keep velocity at 1 to 3 ft/s so pieces neither settle nor shear to puree, and heat with water 20 to 30 degrees above the product.
Single tube-in-tube for pieces
- 2 to 3 inch product bore for pieces to 1/2 inch
- Utility in the annulus, counterflow, hot water or glycol
- Product velocity 1 to 3 ft/s, pressure drop 15 to 30 psi
- Removable inner tube, long-radius sanitary return bends
- 316L product side, 32 or 20 Ra
Multi-tube for purees and small particles
- Seven to nineteen 1 to 1-1/2 inch tubes in one shell
- Pieces to 1/4 inch, higher flow than a single tube
- Corrugated tubes for purees with no pieces
- Better coefficient than a single tube at the same duty
- Fixed or removable bundle by product
Recommended construction by particulate duty
Bore first, then coefficient. A tube that passes the product is the only starting point; everything after that is optimization.
| DUTY / CONDITION | RECOMMENDED CONSTRUCTION | WHY |
| Salsa, chunky soup, chili, fruit prep with pieces 1/4 to 1/2 inch | Single Tube-in-Tube | Largest available bore, one path, no bridging; return bends are jacketed so the product never sees a cold spot |
| Sauces with 1/8 inch dice, pulpy purees, hummus, applesauce | Multi-Tube | Parallel 1 to 1-1/2 inch tubes carry higher flow with a better coefficient than a single large tube |
| Smooth purees, baby food, ketchup, mustard, dressings | Corrugated Tube | No pieces, so corrugation is free to raise the coefficient and cut the length in half |
| Cooking a sauce with plant steam directly, small batch continuous | U-Tube | Steam on the tube side of a hot water set feeding the tube-in-tube; keeps steam temperature off the product wall |
| Cooling a thin sauce with no pieces on a plate frame | Wide-Gap Plate | Where the product is under 500 cP and free of solids, a wide-gap plate is cheaper than tubes |
| Concentrating tomato or fruit puree before sauce making | Evaporator | Forced-circulation sanitary evaporator; the product is then diluted back to sauce viscosity |
Designing a particulate exchanger that runs all shift
Bore selection comes first and it is not negotiable. Take the largest dimension of the largest piece the product will ever contain, including the piece that comes out of the dicer when the blade is worn, and multiply by two. That is the minimum inner tube diameter. A 1/2 inch pepper dice needs a 1 inch bore in theory and a 2 inch bore in practice because pieces arrive in clusters. Pieces above 1/2 inch, whole beans, meatballs, pasta, are dosed after the exchanger or cooked in a separate vessel; no continuous exchanger handles them well.
Velocity is a compromise. Below 1 ft/s in a thin carrier the pieces settle to the bottom of a horizontal tube, overcook against the hot wall and collect at the return bend. Above 3 ft/s in a viscous carrier the pressure drop through a 200 foot exchanger climbs past 60 psi and the pump shears the pieces into puree. The working band is 1 to 3 ft/s, and the way to get more duty without more velocity is more tube length or a multi-tube in parallel, not a smaller bore.
The wall temperature is what scorches. A tomato sauce at 200 F against a steam-heated wall at 300 F browns in minutes and the brown layer insulates the tube until the outlet temperature drops and the operator turns the steam up, which makes it worse. Heat with hot water at 20 to 30 degrees above the product, keep the approach under control, and the sauce comes out the color it went in. HeatX designs the utility side for hot water and supplies the steam-to-water set that makes it.
Bore, velocity and the wall: three numbers that decide it
Cooling a sauce
Cooling is harder than heating because the viscosity rises as the product cools. A sauce at 200 cP hot may be 2,000 cP at 40 F, and the last section of the cooler sees the highest viscosity and the lowest coefficient at the same time. The cooler is sized on the cold end, the glycol approach is kept moderate so the product does not set on the wall, and the pressure drop budget goes mostly to the last quarter of the tube length.
Regeneration on particulate products
Product-to-product regeneration is possible in tube-in-tube with the hot product in the annulus and cold in the bore, but the annulus gap has to pass the pieces too, and the coefficient is poor. In practice most particulate lines regenerate through a water loop: hot product heats water in one exchanger and that water preheats incoming product in another. It recovers 50 to 60 percent and keeps both product paths full bore.
Pet food and meat slurries
Meat emulsions and pet food slurries at 10,000 to 20,000 cP with bone and meat pieces to 1/2 inch run in 3 inch single tube-in-tube at 1 to 2 ft/s, heated to 185 to 195 F on hot water and cooled on tower water. The product side is 316L, the return bends are jacketed, and the exchanger is built so the inner tube pulls for inspection because a USDA inspector will ask to see it.
What settles the quote
Product with viscosity hot and cold, piece type and largest dimension, flow, inlet and outlet temperatures, hold if any, and the hot water, steam or glycol available. A sample and a spec sheet are better than a description. Call and talk it through with an engineer: 1-805-484-2992
Common FAQs
About 1/2 inch in a 2 to 3 inch bore. Above that the pieces bridge at bends and fittings and the hold time cannot be validated. Larger pieces are cooked separately and combined after the sauce is heated.
Almost always steam directly on the utility side. Switch to hot water at 20 to 30 degrees above the product, hold the velocity above 1 ft/s and the browning stops. HeatX supplies the steam-to-water set.
On the fastest particle at the line's flow rate, found by residence time testing with tagged pieces; the tube is then built with that length and slope. The exchanger is sized so the same flow rate keeps velocity in the 1 to 3 ft/s band.
Yes. Rinse to clear, then caustic at 160 to 180 F at 1.5 times the product flow so velocity in the largest bore exceeds 5 ft/s. Tomato and fruit need an acid step for pectin and mineral films. The removable inner tube is for inspection, not routine cleaning.
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