heat load from centrifugal Pump

[Russellking]

I am in the process of sizing refrigeration system that uses a closed chilled loop. I am circulating Trichloroethylene (TCE) @ -40 F. I am using two 60 HP 94.6% eff end suction cetrifugal PACO pumps in parallel. Each motor is using 53.7 bhp at load. I am 84.73% on my pump curve.
I know I need to take into account the heat load that is going to be generated into the loop. My question is do i just take the bhp and convert it into btu's, 1bhp=2545.
Or do i take the eff of the motor times the bhp and then the eff of the pump curve times new bhp and then times the btu 2545 to give me my btu per hour input? If this is wrong i gave it my best guess.

I know quite a bit about refrigeration but do not know much about cetrifugal pumps and how they creat heat in the fluids.

One thing i am not an engineer or pretend to be one. I am just looking for some help from the nice knowledgeable person.

Thank You rking@mercerfoods.com

 

[BigInch]

1 HP running for 1 hour is 2500 Btu.

Your at 87% of what on your pump curve... Flow, or you're at 87% Head, or 87% efficiency? Don't know which one you mean?

At any flow, you're basically only going to put a heat load to the fluid of

(1- %pump efficiency/100) * HP

as heat into the fluid.

In other words, the power not being used by the pump to lift the fluid to the higher head or pressure, will be the heat added to the fluid.

So at 76% efficiency with a 100 HP motor, you will deliver approximately 24% * 100 HP * 2500 Btu/Hr to the amount of fluid passing through the pump during that hour.

http://virtualpipeline.spaces.msn.com

 

[BigInch]

Make that 24% x (100 HP motor - any oversized in that 100 HP)

http://virtualpipeline.spaces.msn.com

 

[Russellking]

Let me correct on the 87% it is 85%. The pump is runnig at 85% efficiency which is about the maximium efficiency of this pump.

So the formula would go somthing like this

(1- %pump efficiency/100) * HP)*2500btu)=heat input
(1-85/100)*53.7)*2500)=20137.5 btu

Since i have two pumps doing the same pump curve i can multiply by two i think.

So do i pass the class

 

[Russellking]

what do you mean by

(100 HP motor - any oversized in that 100 HP)

 

[25362]

Russellking, kindly note that TCE is a suspected human carcinogen. I believe that 50 ppm in air is the TLV.

 

[BigInch]

The calculation should be based on the actual power being delivered to the fluid at any given time, the "hydraulic power", which is not necessarily the HP rating of the motor. A motor may not be delivering its rated HP to the fluid at any given time. Power delivered to the fluid will approach rated motor power at BEP rated flows or higher. Even then, the motor may have been sized larger than necessary, so at lesser flows the motor only delivers a percentage of its total rated power.

To calculate the hydraulic power,

PwrHyd_HP = SG * 62.4 * flowrate_cfs * head_ft / 550 / pump_eff

SG = fluid specific gravity
62.4 = lbs/ft3 density of water
flowrate_cfs = flowrate ft3/s
head = pump's differential head ft.
pump_eff = pump's efficiency at flowrate_cfs

pump's differential head ft = (disch press psig - suction press psig) * 144 / SG / 62.4

Yes, if two pumps are running then X 2, if the pumps are identical, otherwise calculate power delivered for each pump and add.

http://virtualpipeline.spaces.msn.com

 

[GregLamberson]

BigInch

Just a clarification on your last sentence - if you use 2 identical pumps, you will 2 x the capacity, but 4 x the head - correct?

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[GregLamberson]

BigInch

Never mind, I got confused, I was thinking that if you double the speed you get 2 x the capcity and 4 x the head.....I'm going to get back to work.

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[Russellking]

Yes TCE has gotten a bad name but from those that improperly handled and disposed of it. I have many safe gaurds in place for dealing with thos types of issues.
TCE is widley used in many things beleive it or not read below.
TCE is a good heat transfer medium in the temperature range of -73°C to +120°C. At -40 C is wher i will be running at this temp TCE is the best HTF out their
Used as a coolant for cutting tantalum and other special metals.
Used as a freezing point depressant, especially in fire extinguisher fluids.
Soaps containing TCE are used as some disinfectants used in hospitals and insecticides.
Used in making rubber cements, bone glue and adhesive activators.
As a solvent for paints, lacquers, dyes, oils, fats, waxes, resins, halohydrocarbons and many other chemicals.
Used in textile industry for removing spots, recovering oils and greases, sizing and dry-cleaning.

Anyways the thing we know today that we didnt know 40 years ago I Should have been dead along time ago. Its all good thou.

 

[BigInch]

Wow Greg, now you got me confused.

http://virtualpipeline.spaces.msn.com