LP & LPR Series selection
is not available, the case drain flow can be utilized to help cool the system However, in many instances, the case drain flow alone will not be enough to reject all of the heat generated by the system. Case drain lines should not be treated as a normal return lines since the pressure drop allowable usually can vary from12 - 10 PSI max. Check with your pumpmanufacturer for the appropriate pressure drop tolerance before applying any cooler. To size the system for case flow or case flow plus any additional flushing loops, please use the following method.
SIZING To properly size a DC fan drive air-cooled oil cooler for mobile equipment, you should first determine some basic parameters associated with the system. HEAT LOAD In many instances the heat load must be determined by using a "total poten- tial" method. This total potential or horse power method is the most common method, and is the simplest way to determine basic heat rejection requirements for mobile hydraulic systems. The total potential us equal to the maximum operating flow and pressure that are generated by the system under full load. To determine the total potential (HP) use the following formula.
Formula
T = System temperature entering
HP = [ System Pressure (PSI) x System flow (GPM) ] / 1714
Tc exit = { T - [ Q / (case flow gpm x 210) ]} Example Tc exit = { 150 - [ 6,681 / (4 x 210) ]} = 142
Example: HP = (3000 PSI x 6.0 GPM) / 1714 = 10.5 HP or the total input potential To determine the system heat load in BTU / HR we must use a percentage (v) of the system potential HP. The factor (v) can be calculated by adding up the actual inefficiencies of a system; however, for most applications a (v) value of 25% - 30% can be used.
Tc exit = The corrected temperature of the oil exiting the cooler. Fs =
Q x Cv ____________ Tc exit - t ambient
6,681 x 1.13 ___________ = 180 Fs 142-100
Example: 10.5 HP x .25 = 2.63 HP heat
SELECTION To select a model, locate the flow rate (GPM) at the bottom of the flow vs Fs graph. Proceed upward until theGPM intersectswith the calculated Fs. The curve closest above the intersection point will meet these conditions. Examples:
To convert the horsepower of heat into BTU/HR use the formula below: HP x 2542 = BTU/HR
Example: 2.63 HP x 2545 = 6,681 BTU/HR Applying into a return line
Return Line Fs = 189 GPM = 6 "return line flow" Model = LP - 300
Case Line Fs = 180 GPM = 4 Model = LP - 300
For most open loop systems with a vane or gear type fixed delivery pumps. To calculate the Fs value required when applying the air/oil cooler into a return line use the formula below.
PRESSURE DROP Determine the oil pressure drop from the curves as indicated. For viscosi- ties other than 50 ssu, multiply the actual indicated pressure drop (psi) for your GPM by the value in the pressure differential curve for your viscosity value.
6,681 x 1.13 _______________ 140°F - 100°F
BTU/ HR x Cv _______________ T - t ambient
Fs =
Fs =
= 189
T = Desired system oil temperature leaving the cooler °F (140°F) t ambient = Ambient air temperature entering the cooler °F Cv = Correction factor for oil viscosity. Example: ISO68 oil @ 150°F = 1.13 (see chart) APPLYING INTO A CASE DRAIN LINE In circumstances where the system is a closed loop or when return line flow
Examples:
GPM = 6
GPM = 4
Indicated pressure drop Cp correction factor for ISO 68 oil @ 150°F
.2 PSI
.1 PSI
.213
.113
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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