Temperature rise of liquid at normal operation


The temperature rise of a liquid being pumped can be estimated by using any of
these two equations:

T = [(H / 778xC) / (1/E - 1)]

where:

T = temperature rise, degrees F
H = total pump head, FT
C = specific heat of liquid
E = pump efficiency, in decimal point

Or, use the equation:

T = [2545x(BHP-WHP) / (QxC)]

where:

T = temperature rise, degrees F
BHP= brake horsepower
WHP= water horsepower
Q = capacity, lbs/hr
C = specific heat of liquid

use C=1.0 for water, C=0.5 for hydrocarbons if actual value is unknown

The equations neglect the effect of heat loss through the case and assume that
none of the liquid is being recirculated back to pump suction.

Rule-of-Thumb: For safe operation the temperature rise should be limited to 15
degrees F. This criteria was first established for boiler feed pumps and may be a
conservative value for cold water application but may be excessive for other
service such as cryogenic.

Rule-of-Thumb: Allow a minimum flow of 300 GPM for every 100 HP at shut-off to
prevent excessive temperature rise.


Example 1:  A multi-stage pump has a differential head of 5000 FT and an
efficiency of 80%. What would be the temperature rise of the liquid at the pump
discharge?

Solution: T = [(5000/{778x1}) / ({1/0.8}-1)] = 1.6 degrees F


Example 2:  A boiler-feed pump is handling 50,000 lbs/hr of feedwater. The pump
has an efficiency of 70% and requires 20 BHP. What would be the rise in water
temperature?

Solution: The WHP is BHP x Efficiency, or WHP = 20 x 0.70 = 14 HP

T = [(2545x{20-14}) / (50,000x1)] = 0.31 degrees F
CENTRIFUGAL-PUMP.ORG
Related topics

Temperature rise at normal operation
Temperature rise at shut-off operation
Warm-up procedure in high temperature service
Thermal shock
Conversion factors
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