How to Size a Dairy Heat Exchanger

What moves the answer

Fat is the first thing that shifts a selection. Milk with a few percent fat behaves close to water in a plate channel. Past about 30 percent fat, cream thickens sharply as it cools, a standard plate stops distributing it evenly, and the contact points start to foul. The answer there is a wide-gap plate with a 6–12 mm channel, or a tubular unit. Ice cream mix, with its sugar, stabilizer and high total solids, sits on the same side of that line even at modest fat. Fat also decides the gasket: EPDM on milk and whey, nitrile where cream and butter cream would swell it.

Particulates and shear move it next. Cheese fines in whey, fruit pulp and visible pieces bridge a plate gap, and a set yogurt curd broken for cooling loses body if it is forced through tight channels. Tube-in-tube handles both, with a single-tube bore when pieces approach an inch. A plant that must open and brush the product side by hand, or a UHT line running at 280°F and above, ends up on straight tube or shell-and-tube, whatever the product. Ask what the product looks like at the coldest point inside the unit, and most of these choices settle quickly.

Two layout questions sit on top of the construction. A milk-to-milk regenerator typically recovers 85–94% of the heat, and every point added means more plates and a longer frame. Where raw and pasteurized milk meet across one plate, the pasteurized side has to stay at least 1 psi higher than the raw side, and some plants add double-wall plates as a second barrier behind that margin. Match the Product takes all three choices in order, and Size the Duty picks up from there.