AOCH & AOCHM Series selection Multiply system pressure by the flow rate of the main system divided by 1714 equals system potential (HP). Multiply the system HP by a heat removal factor (Normally 25-35%). Note: In some closed loop systems only a portion of the total system flow is directed through the heat ex- changer. This may affect the cooler selection process substantially. You may contact our factory for additional technical assistance.
Sizing The performance curves provided are for petroleumoil at 50 ssu viscosity. However, fluids with characteristics other than the above mentioned may be used by applying a correction factor. Heat Load If the heat load is unknown, a horsepower value can be calculated by first determining the systems total potential. For a basic hydraulic system, it is helpful to know whether the system is open loop (with a large res- ervoir) or closed loop (normally on mobile equipment, with a very small reservoir). System potentials may be calculated quickly by using one of the two methods below. There are some system parameters that will be required to properly ac- complish thesizingcalculations.Without systemparameters, it isdifficult to determine the optimal heat exchanger size. Normally many of the system parameters can be found on hydraulic schematics or on tags located on the actual equipment. Following are some basic parameters that you should try to acquire before attempting the sizing calculations. However, it is not necessary to have every parameter listed below. • Main system flow rate (gpm) & operating pressure (psi). • Electric motor HP driving hydraulic pump (if more than one add up the Hp for all). • Desired temperature (°F). • Fluid type (SAE 10, 20, 30, etc....). • Ambient air temperature (warmest day). • Desired fan drive (hydraulic, electric, 12-24V DC, etc...). • BTU's or HP to be cooled (normally given for lubrication systems). • Maximum pressure drop allowed through the heat exchanger. • Space available for heat exchanger (LxWxH). • External air condition (dirty, papers,etc). Method 1 Normally used for open loop circuits. Multiply the main hydraulic sys- tems Electric Motor Name plate Horsepower by a heat removal factor (normally 30-50%).
(2000 psi x 60 gpm) = [70 HP x .25] = 17.5 HP heat load _______________ 1714
Example:
Determining Fs value To determine the proper size heat exchanger for your application, use the following equation to first determine the (Fs) factor:
{ heat load (HP) x 2545 x Cv} ________________________ { °F (oil leaving - air entering) }
Fs =
Example: Heat load = 17.5 HP Cv = 1.14 (SAE 20) determined from chart. [Located on page 5.] Desired operating temperature = 120 °F Ambient air temp. = 100 °F
{ 17.5 x 2545 x 1.14 } ________________ { 120 °F - 100 °F }
Fs =
= 2539
Selection To select a model, locate the flow rate (GPM) at the bottom of the flow vs Fs graph. Proceed upward until the GPM flow rate intersects with the calculated Fs. The curve closest above the intersection point will meet these conditions.
Example:
Fs = 2539 = Model = AOCH,AOCHM - 35 GPM = 60 PASSES = 1
Pressure differentials Determine the oil pressure drop from the curves as indicated. For vis- cosities other than 50 ssu, multiply the actual indicated pressure drop for your GPM flow by the value shown in the pressure differential curve for your viscosity value.
Example: 50 HP motor x 0.3 = 15 HP heat load
Example: Model 35 @ 60 gpm & 50 ssu -1 pass curve- Indicated pressure drop 2.4 psi (Approx)
Method 2 Normally used when the HP input potential is unknown or for mobile ap- plications where diesel engines operate the entire system.
{ 2.4 psi x 2.8Cp (for SAE-20 oil) } = 6.72 corrected psi
Cv VISCOSITY CORRECTION FACTORS
Average Liquid Temperature
100 110 120 130 140 150 200 250
1.11 1.09 1.06 1.04 1.03 1.01 0.98 0.95
1.15 1.12 1.10 1.08 1.05 1.04 0.99 0.96
1.25 1.20 1.17 1.13 1.11 1.09 1.01 0.97
1.38 1.32 1.27 1.24 1.19 1.16 1.04 0.98
1.45 1.40 1.35 1.29 1.25 1.22 1.07 0.99
1.08 1.06 1.04 1.03 1.02 1.02 0.98 0.95
1.14 1.13 1.11 1.09 1.08 1.06 0.99 0.96
1.18 1.16 1.14 1.13 1.10 1.09 1.00 0.96
1.26 1.25 1.20 1.17 1.16 1.13 1.01 0.96
1.37 1.31 1.27 1.24 1.20 1.17 1.02 0.97
1.43 1.39 1.35 1.30 1.26 1.22 1.08 0.99
1.56 1.48 1.40 1.34 1.30 1.27 1.09 1.01
1.84 1.67 1.53 1.44 1.39 1.33 1.14 1.02
1.19 1.14 1.09 1.05 1.03 1.01 0.98 0.97
0.92 0.89 0.88 0.85 0.84 0.83 0.79 0.76
0.83 0.80 0.79 0.77 0.76 0.74 0.71 0.69
0.85 0.84 0.84 0.83 0.82 0.82 0.80 0.79
Cp PRESSURE DROP CORRECTION FACTORS
Average Liquid Temperature
100 110 120 130 140 150 200 250
2.00 1.70 1.50 1.40 1.30 1.20 0.93 0.81
2.40 2.10 1.80 1.60 1.50 1.30 0.96 0.82
4.40 3.60 3.00 2.60 2.23 1.90 1.20 0.92
6.40 5.10 4.20 3.40 2.90 2.50 1.40 0.97
8.80 6.70 5.60 4.50 3.70 3.10 1.60 1.05
1.07 1.04 1.02 0.99 0.97 0.95 0.89 0.85
1.53 1.45 1.38 1.30 1.23 1.17 0.99 0.93
1.82 1.72 1.60 1.49 1.38 1.30 1.08 0.96
2.54 2.35 2.15 1.94 1.75 1.61 1.18 1.03
4.19 3.73 3.26 2.80 2.38 2.04 1.33 1.11
6.44 5.70 4.91 4.14 3.47 2.90 1.59 1.21
9.38 8.33 7.23 6.19 5.20 4.35 1.74 1.22
13.56 11.63
1.26 1.20 1.14 1.08 1.03 0.98 0.90 0.83
3.00 2.40 2.10 1.90 1.90 1.70 1.20 1.00
3.50 2.90 2.50 2.20 2.00 1.90 1.30 1.05
0.730 0.720 0.709 0.698 0.686 0.676 0.635 0.556
9.73 7.80 6.11 4.77 1.95 1.23
note: AIHTI reserves the right to make reasonable design changes without notice.
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tel: 434-757-1800 355 American Industrial Drive LaCrosse, VA 23950
email: sales@aihti.com fax: 434-757-1810
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