Physics Help Forum Finding volumetric flow rate of heat engine

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Feb 7th 2018, 07:33 AM #1 Junior Member   Join Date: Feb 2018 Posts: 9 Finding volumetric flow rate of heat engine A Heat Engine has a thermal efficiency of 40% at a steady power output of 30kW. Calculate the required volumetric fuel flow in L/Hr ( litres/hour) if the fuel has a density of 850 kg/m^3 and an energy content of 45 MJ/kg.
 Feb 7th 2018, 08:47 AM #2 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 1,031 So how have you started this question, and where have you got stuck? It is a very straightforward question.
 Feb 7th 2018, 09:26 AM #3 Junior Member   Join Date: Feb 2018 Posts: 9 I found Qlow, Q high. I know that density =mass / volume. But how can i apply the energy balance eqn?
Feb 7th 2018, 09:35 AM   #4
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 Originally Posted by casperneo I found Qlow, Q high. I know that density =mass / volume. But how can i apply the energy balance eqn?
Not sure what you are trying to do here.

If the efficiency is 40% what is the input power?

 Feb 7th 2018, 09:38 AM #5 Junior Member   Join Date: Feb 2018 Posts: 9 75kW
 Feb 7th 2018, 10:10 AM #6 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 1,031 And 75kW is 75 kJ per second. So what mass of fuel per second has this energy content?
 Feb 7th 2018, 06:40 PM #7 Junior Member   Join Date: Feb 2018 Posts: 9 Okay, i got it. Thanks
 Feb 8th 2018, 12:36 AM #8 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 1,031 Hopefully this style of reply has helped you more in the long run than just me writing out the answer.
 Feb 9th 2018, 05:27 AM #9 Junior Member   Join Date: Feb 2018 Posts: 9 I have another question regarding thermodynamics, A ship's anchor, made of 500kg of steel and initially at a temperature of 20 degree is dropped into the ocean which has a temperature of 7 degree. Determine the entropy change of the anchor. Can i assume that since the ocean has a huge volume, the ocean water would not change temperature. Thus, the steel anchor will have a final temperature of 7 degree. Solving it, using Cp= 4.002KJ/KG.K The answer is -0.18162 KJ/K.
Feb 9th 2018, 07:33 AM   #10
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 Originally Posted by casperneo I have another question regarding thermodynamics, A ship's anchor, made of 500kg of steel and initially at a temperature of 20 degree is dropped into the ocean which has a temperature of 7 degree. Determine the entropy change of the anchor. Can i assume that since the ocean has a huge volume, the ocean water would not change temperature. Thus, the steel anchor will have a final temperature of 7 degree. Solving it, using Cp= 4.002KJ/KG.K The answer is -0.18162 KJ/K.
I'm sorry but this is not correct since the temperature of the anchor varies during the cooling.

In any case you should have started a new thread for this.
I will do this for you and we can continue the discussion there.

The entropy change of solids and incompressible liquids

Last edited by studiot; Feb 10th 2018 at 03:44 AM.

 Tags engine, finding, flow, heat, rate, volumetric

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