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Quotes - Engineering - SalesFour Steps to a Sized Recommendation
1.
Name the fluids and the product-contact side
Start with what is on each side. Product on one side, utility on the other, and be clear about which is which, because the product-contact side sets the finish, the connections and the drainability rules while the utility side can usually be plain 304. Write down the product as it actually runs: raw milk at 3.5% fat, single-strength juice with pulp, 40% sucrose syrup, WFI at 80 C. If the product changes between runs, list the worst case for viscosity and the worst case for fouling separately, because they are often different products.
2.
Pin down flow, temperatures and regeneration
Flow rate, inlet temperature and outlet temperature on the product side give the duty directly: Q equals mass flow times specific heat times temperature change. Ten thousand pounds per hour of milk from 40 F to 165 F at a specific heat of 0.93 is about 1.16 MMBtu per hour. Then decide whether the hot product should preheat the cold product on its way in. Regeneration of 85 to 95% is normal on a pasteurizer and cuts the utility duty to a fraction, but it changes the exchanger from one unit into two or three sections, so it has to be decided before anything is sized.
3.
Let viscosity, particulates and hygiene class pick the construction
Three facts choose between plate, shell-and-tube and tube-in-tube. Viscosity: gasketed plates are comfortable below about 500 cP, and above that the pressure drop climbs faster than the heat transfer, so the duty moves to a tube. Particulates: anything above about an eighth of an inch, or any fiber that can bridge a plate gap, calls for tube-in-tube or a wide-gap plate. Hygiene class: food-grade drainable, 3-A, or ASME BPE pharma. The class decides whether a double tubesheet, a specific surface finish and full documentation are required or merely nice to have.
4.
Finish the spec: connections, finish, CIP/SIP and utility
The last step turns a thermal size into an orderable unit. Connection type and size on both sides (tri-clamp on product, and often on utility as well), the product-contact finish as a Ra number, whether a double tubesheet is required, what the CIP chemistry and temperature will be, and whether the unit will see live steam during SIP. Then the utility: plant steam, culinary steam, a hot water loop, chilled water or glycol, each with its supply temperature and the pressure available at the exchanger. With those in hand the quote is a price, not a list of questions.
What Sizing Takes
What a Sized Recommendation Looks Like
A finished selection names the construction, the surface area, the number of passes or plates, the utility flow and the pressure drop on each side. On a plate unit that reads as plate size, plate count and frame length with the port sizes. On a sanitary shell-and-tube it reads as shell diameter, tube count, tube length, tube-side and shell-side passes and the connection sizes. On a tube-in-tube it is the inner tube size, the number of tubes in the annulus, the module length and how many modules are in series. Every one of those numbers is an output of the four steps above, and every one is checkable against the duty you gave us.
The three branches of this section follow the same order as the steps. Size Your Exchanger covers duty, log mean temperature difference, regeneration, viscosity and particulates. Choose the Construction compares plate, shell-and-tube and tube-in-tube on the same duty, works through the double tubesheet decision, and matches the utility to the product. Replace Your Exchanger is for the buyer who already has a unit on the floor and needs the equivalent: look it up by manufacturer and model, match it by dimensions and connections, and send the nameplate data.
The common mistake is to size on the nominal case and forget the start-up, the CIP cycle and the changeover product. A pasteurizer that runs milk five days a week and cream on the sixth will have been sized for milk and will fall short on cream, because the specific heat is close but the viscosity is not. Ask for the worst case on every line of the form, and if you are not sure what the worst case is, say so and we will size for it.
Related
Sizing & Selection
Size Your Exchanger
Duty, temperature difference and the U-value your product will actually give you.
+ Learn More
Sizing & Selection
Choose the Construction
Plate, shell-and-tube or tube-in-tube, single or double tubesheet, and the utility that suits the product.
+ Learn More
Sizing & Selection
Replace Your Exchanger
Look up the unit you have, match it by dimensions and connections, and send us the nameplate.
+ Learn More
