Inline Steam Jet Heaters

Eductors use steam to heat water through a process that leverages the principles of the Venturi effect and direct steam injection. Here’s how it works:

Motive Fluid (Steam): High-pressure steam is introduced into the eductor as the “motive fluid”.
Nozzle Acceleration: This steam is forced through a converging-diverging nozzle. As it passes through this constriction, its velocity dramatically increases, often exceeding the speed of sound.
Pressure Drop: This rapid acceleration of the steam creates a significant drop in pressure within the eductor’s suction chamber, generating a partial vacuum.
Water Suction: The water to be heated (the “suction material”) is then drawn into this low-pressure zone through a separate inlet.
Direct Contact and Mixing: The high-velocity steam comes into direct contact with the incoming water. The heat from the steam is rapidly transferred to the water as the steam condenses within the mixing chamber.
Discharge: The mixed, now heated, water is then discharged from the eductor.

This method is efficient because it directly transfers heat from the steam to the water, often eliminating the need for heat exchangers. Steam jet heaters are specifically designed for this purpose, with applications such as circulating cleaning solutions, pasteurization, sterilization, and general tank heating. They offer a practical, simple, and cost-effective alternative for heating in open tanks.

Inline steam jet heaters have three common features (designations may vary according to design): inlet, suction and discharge.

Inlet – The operating liquid (some-times called the Motive) under pressure enters the inlet and travels through the nozzle into the suction chamber. The nozzle converts the pressure of the operating liquid into a high velocity stream, which emerges from the discharge side of the inlet nozzle.

Suction – Pumping action begins when steam in the suction chamber is entrained by the high velocity operating liquid stream emerging from the inlet nozzle, lowering the pressure in the suction chamber. The resulting action causes the steam in the suction chamber to flow toward the discharge.

Discharge (sometimes called Outlet) – The entrained steam n the suction chamber mixes and condenses into the operating liquid and acquires part of its energy, flowing into the parallel section. In the diffuser section, part of the velocity of the mixture is converted into a pressure greater than the suction pressure, but lower than the inlet pressure.

Model	Heating Process	Max Temp Rise (°F)	Max Heated Flow (GPM)	Steam Pressure Range (PSIG)
MLE	In-line	180	5,000	Vac – 45
MLH	In-line	215	5,000	Vac – 120
ULJ	In-line	200	700	0 – 150

Eductors use direct contact condensation: high-velocity motive liquid (usually water/process fluid) creates a low-pressure zone that entrains steam. Steam condenses instantly, transferring 100 % of its BTUs to the liquid while also diluting it slightly.

No heat exchanger → no scaling or efficiency loss.
Simultaneous pumping + heating in one compact unit with zero moving parts.

Inline stream jet heater operation Several types of Steam Jet Heaters are available. Although their designs vary, the operation of each is based on the jet operating principles of the jet pump.

Sizing for In-Line Heating (MLE, MLH, ULJ)

Core formula (approximate steam consumption): $Q_s = \frac{Q_m \times 8.33 \times \Delta T}{1100}$ where

$Q_s$ = steam flow (lb/min)
$Q_m$ = motive liquid flow (GPM)
$\Delta T$ = desired temperature rise (°F)
8.33 = lb/gal (water); 1100 ≈ BTU/lb steam (use steam tables for precision).

MLE / MLH procedure (higher temp rise, higher pressure drop):

Calculate required steam $Q_s$ .
Use performance table for motive pressure and desired ΔT.
Compute sizing factor (S.F.) = desired GPM ÷ tabulated GPM.
Select size from S.F. table (1-1/2″ = 1.00 reference).
Verify outlet pressure and available steam pressure.

ULJ procedure (lower pressure drop, multi-pass capable): Steam flow drives sizing; calculate pressure drop with: $\Delta P = (Q_m \times 14.14 \times S.F.)^2$

Worked Example: 90 GPM motive at 60 PSIG, 65 °F rise, 100 PSIG steam, 30 PSIG max outlet → MLH 2½″ (S.F. 3.17) selected.

1. In-Line Heating Eductor (MLH Model) – High Temperature Rise

Application: Single-pass heating of a process stream.

Given conditions (exact example from the PDF):

Motive liquid flow required: 90 GPM
Motive pressure (Pm): 60 PSIG
Inlet liquid temperature: ~85 °F
Desired outlet temperature: 150 °F
Desired temperature rise (ΔT): 65 °F
Available steam pressure (Ps): 100 PSIG (saturated)
Maximum allowable discharge pressure: 30 PSIG

Step-by-step sizing (MLE/MLH procedure):

Calculate required steam flow
1. $Qs=Qm×8.33×ΔT1100Q_s = \frac{Q_m \times 8.33 \times \Delta T}{1100}$ $steamQ_s = \frac{90 \times 8.33 \times 65}{1100} = 44.3 \, \text{lb/min steam}$
Use the MLH performance table At 60 PSIG motive pressure and 65 °F temperature rise, a 1-1/2″ unit handles 30 GPM of motive liquid.
Calculate required Sizing Factor (S.F.) $flow=9030=3.0\text{S.F.} = \frac{\text{Desired motive flow}}{\text{Tabulated motive flow}} = \frac{90}{30} = 3.0$
Select size from the S.F. table
- 2″ → S.F. = 1.82
- 2½” → S.F. = 3.17 (meets or exceeds 3.0) → Choose MLH 2½”
Verify steam pressure Table shows required steam pressure < 100 PSIG available → OK.
Verify outlet pressure Table shows maximum outlet pressure ≈ 50 PSIG (with steam flowing) > required 30 PSIG → Acceptable.

Final selection: MLH 2½” eductor

Actual calculated performance of selected unit:

Motive flow = 29 GPM (tabulated) × 3.17 = 91.9 GPM
Steam flow = 15.6 lb/min × 3.17 = 49.4 lb/min
Actual ΔT = $\frac{49.4 \times 1100}{91.9 \times 8.33} \approx 71^\circ$ F (slightly higher than 65 °F target)

If the actual rise is too high, reduce steam pressure or throttle the steam valve slightly.

Quick Notes

Always verify final outlet pressure and actual ΔT with the full performance tables in the PDF.
For intermittent operation or low-pressure steam, the ULJ model may be preferred (lower pressure drop).

Steam Jet Heaters operate by condensing steam into the liquid that is being heated. The process ensures a complete transfer of the BTUs in the steam to the liquid. The steam gives up its BTUs as it condenses into the liquid. This also dilutes the motive liquid with the condensate. Eductor liquid heaters function under the normal principles of eductors. In actuality, the process is that of a liquid pumping a gas.

The only thing that differs with pumping steam as a suction fluid is the increased affinity of steam for cold water. Because of this affinity, a greater volume of steam is pumped under the same conditions. Also, in some cases, the BTUs being released allow the unit to discharge to higher pressures than either the motive or the suction pressure.

In line steam Jet Heaters utilize the principal of direct injection to mix steam with a cold liquid uniformly. Operation is efficient because the heat in the steam is absorbed by the liquid being heated to approximately 10% of liquid saturation temperature. The jet action produces agitation and circulation, eliminating the need for other equipment to accomplish these functions in most applications. In operation, jet heaters use steam (or steam and water under pressure) as the motive force to entrain, mix with, heat, and pump (or circulate) the suction liquid.

Typically, a steam jet heater includes an inlet for the liquid to be heated, a steam inlet (suction) where steam is introduced under pressure, and a discharge where the heated liquid and condensed steam leave the heater. (These correspond to the inlet, suction and discharge of a jet pump.)

The advantages of using steam jet heaters for heating liquids Steam Jet Heaters offer many advantages:

They have no moving parts, nothing to break or wear.
There are no packing glands.
No lubrication is required.
The initial cost is low.
Installation cost is low because they are compact and no foundation or wiring is necessary.
They provide reliable operation with low maintenance cost.

Steam jet heater applications:

There are numerous possible applications for Steam Jet Heaters. Heaters are available for heating liquids in line or in a tank. Steam Jet Heaters are commonly found in these industries: food processing, petroleum, dairy, manufacturing, chemical, distilling/brewing, and others.

Specific applications for inline heaters include: circulating cleaning solutions, pasteurization, producing scalding sprays, sterilization, heating water, blanching, exchanging heat, degreasing, heating slurries, laundering, cooking, pickling, bonderizing, quenching and tempering.

Specific applications for open tank heaters include cooking grain, cooking mash, cooking starch, heating and circulating, mixing.