ExampleSolutions

ExampleSolutions - 2.7- 6Energy Balance on a Flow System...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 2.7- 6Energy Balance on a Flow System with a Pump and Heat Exchanger. Waterstored in a large, well-insulated storage tank at 21.0 C and atmospheric pressure isbeing pumped at steady state from this tank by a pump at the rate of 40 m3/hr. Themotor driving the pump supplies energy at the rate of 8.5 kW. The water is used as acooling medium and passes through a heat exchanger, where 225 kW of heat is addedto the water. The heated water then flows to a second large, vented tank, which is 25 mabove the first tank. Determine the final temperature of the water delivered to thesecond tank.kPa1000 Pa:=25 m heater 2 1 Q T1= 21 C T2= ? Vr40m3hr:=kJ103J:=z25 m:=gz245.166Jkg=v1v2=(approximately 0 in large vessels)p1p2=(both vessels open to atmosphere, no pressure changes)FJkg:=(assume friction losses minimal)H188.14kJkg:=(enthalpy at 21C from saturated Steam Tables)110.0010020 m3kg1-:=1998kgm3=(from sat Steam Tables)mrVr1:=mr11.09kgs=(mass flow rate)Energy from Pump:Energy from Heat ExchangerWs8.5kWmr:=Ws766.53Jkg=dQ255 kWmr:=dQ23kJkg=H2H1Ws+dQ+:=H2111.9kJkg=Temperature Estimate from Enthalpy (interpolate from Steam Tables)2725-() 111.9104.89-()113.25104.89-25+26.677=Implies t2= 26.7 C2.7- 7Mechanical-Energy Balance in Pumping Soybean Oil. Soybean oil is beingpumped through a uniform-diameter pipe at a steady mass-flow rate. A pump supplies209.2 J/kg mass of fluid flowing. The entrance abs pressure in the inlet pipe to thepump is 103.4 kN/m2. The exit section of the pipe downstream from the pump is 3.35 m above the entrance and the exit pressure is 172.4 kN/m2. Exit and entrancepipes are the same diameter. The fluid is in turbulent flow. Calculate the friction lossin the system. The density of soybean oil is 919 kg/m3.FWsgzp+v22+-=oil919kgm3:=Ws209.2Jkg:=p172.4 kPa103.4 kPa-:=z3.35 m:=v2=FWsgzpoil+-:=F101.3Jkg=2.7- 9Pressure Measurements from Flows. Water (998 kg/m3) is flowing at the rate of1.676 m/s in a 3.068-in ID horizontal pipe at a pressure of p1= 68.9 kPa abs. It thenpasses to a pipe having an ID of 2.067 in....
View Full Document

Page1 / 7

ExampleSolutions - 2.7- 6Energy Balance on a Flow System...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online