Efficient, economical, industrial/commercial hot water heating. Steam to water or water to water heat transfer.
THE QUICK, EASY WAY TO "ENGINEER YOUR OWN WATER HEATER"
In the selection of a U-Tube Heat Exchanger for water heating applications, this catalog offers much greater flexibility and exactness than tabular forms commonly used. Ludell's exclusive curve selection method eliminates the limitations inherent in tabular catalog forms. No interpolating is required.
SELECTION PROCEDURE:
The operating conditions which must be established prior to selecting the proper Ludell U-Tube heat exchanger for heating water with steam are:
- Amount of water to be heated in GPM.
- Steam pressure furnished to exchanger in PSIG.
- Incoming water temperature ºF.
- Desired outlet temperature of heated water in ºF.
- Maximum allowable water pressure drop.
- Fouling factor.
To size a Ludell U-Tube Heat Exchanger for an in-the-line water heating application, simply read the curves and proceed to work the following formula.
- Find steam temperature from Curve I.
- Find "f" from Curve II.
- Find heat transfer area required from this Ludell formula:
- t1 = Incoming water temperature in °F.
- t2 = Desired outlet temperature of heated water in °F.
- T = Steam temperature from Curve I in °F.
- f = Factor from Curve II.
Select the heat exchangers from the model selection table which have sufficient heat transfer area and are within the range of the flow requirements. (The allowable flow range is based upon velocities from 2.8 to 7.5 feet per second.)
Calculate the pressure drop (see Curves III and IV) to determine whether or not the selections come within the allowable limits.
The selection formula includes a conservative fouling factor of .0015 for each heat exchanger. For severe hard water, silt, algae or other pollution, we recommend that you consult your local Ludell engineer or contact the Ludell home office in Milwaukee.
EXAMPLE:
Select a heater to heat 130 GPM from 60°F to 140°F with 35 PSIG steam and a maximum water pressure drop of 6 ft. H2O.
- From Curve I, 35 PSIG steam, T = 281°F
- From Curve II, Since Ratio
- Find heat transfer area required
- Select the heaters which have a minimum of 73.1 sq ft. and meet the flow requirement of 130 GPM
These models will apparently qualify:
Model 10U83-2
Model 10U83-4
Model 12U56-4
For final acceptability, calculate the pressure drop of the three heat exchangers.
- Model 10U83-2:
Using Curve III, the point of 130 GPM flow through a 10" diameter, 2-pass heat exchanger intersects with a pressure loss of 0.0204 feet of water for each inch of shell length. Pressure drop = 0.0204 (83) = 1.7 fl. H2O. . . ACCEPTABLE!
- Model 10U83-4:
From Curve IV, a 130 GPM flow rate through a 4-pass, 10" diameter heater indicates a drop of 0.157 ft. H2O per inch of shell length. Pressure drop = 0.157 (83) = 13 ft. H2O. . . NOT ACCEPTABLE!
- Model 12U56-4:
Curve IV shows a pressure drop of 0.082 ft. H2O per inch of shell length at 130 GPM through a 4-pass, 12" heat exchanger. Pressure drop = .082 (56) = 4.6 fl H20. . . ACCEPTABLE!
Final selection should be based upon safety margin, pressure drop and price considerations. The correct specification in this example is Model 10U83-2. It has the most heat transfer area, the smallest pressure drop and is lowest in price.
This catalog makes it easy for you to size a water heater. Please remember that Ludell U-Tube Heat Exchangers have a wide range of applications for liquid-to-liquid and gas-to-liquid heat transfer.
Considering the great number of variables involved in a wide range of applications, we believe your requirements will best be served when you furnish the design data to Ludell application engineers and request a recommended specification. This service places you under no obligation!