 # 09404882433 2000 00993 m 3 kg specific heats specific

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) =(0.94)(0.4882)(433)2000= 0.0993 m3/kgSpecific HeatsSpecific Heat at constant volume, is defined asCv = (𝛿?𝛿𝑇) , KJ/kg K.Cv = du/dTthen’du = Cv dT,dU = mCv dT,Thus the first law statesδQ = dU + δW,For constant volume,δW =∫ 𝑝dV = 0 , soδQ = dU, and for constant volume process,
Q= ΔU = mCv (T2T1), and the change in internal energy is,ΔU =m Cv (T2T1) = U2U1Specific Heat at constant Pressure, is defined as,Cp = (𝜹?𝜹𝑻)KJ/kg KFrom h = u + pvdh = Cp dTdH =mCp dTδQ = dH for P = C,hence,δQ = dH = mCp dT, alsodh = du + R dtCp dT = Cv dT+R dT, thusCpCv=RRefer to Table 5.4 , Formulas for specific heats variation with temp.Example Problem;For a certain ideal gas, R = 0.277 KJ/kg K and k = 1.384. What are the values of Cp and Cv??
Example;Determine the average Cp value in kJ/kg K of a gas if 522 KJ of heat is necessary to raise the temperature from 300 Kto 800K making the pressure constant.
Assignments1.A large mining company was provided with a 3000 cm3of compressed air tank. Air pressure in the tank dropsfrom 700 KPa to 180 KPa while the temperature remains unchanged at 280C. What percentage has the mass
2.A mountain is to be measured by finding the change in pressure at constant temperature A barometer at thebase of the mountain reads 730 mm Hg, while at the top it reads 470 mm Hg. The local gravitationalacceleration is 9.6 m/s2
3.For a particular gas, the value of R=0.280 KJ/kg K and the value of k=1.375. Determine the value of Cp and
4.Determine the size of spherical balloon required to lift a payload of 1360 kg. The gas to be used is Helium at101.3 Kpa and 230C. The surrounding air is 101.3 KPa and 100C.
5.Helium is assumed to obey the Beattie- Bridgeman equation of state. Determine the pressure for atemperature of 5000C and a specific volume of 5.2 m3/kg. Compare with the ideal gas equation of state.Ans.
6.Two spherical balloon each 1.81 m in diameter are connected by a pipe in which there is a valve. Each spherecontains helium at temperature of 26.260C when valve closed. One sphere contains 1.1337 kg and the other0.56689 kg. After the valve has been open long enoughfor equilibrium to be obtained, what is the commonpressure in the sphere if there is no loss of energy.
7.The volume of air at 100 KPa and 250C is 300m3. What is the volume of the same mass of air at 400 KPa and350.

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Term
Fall
Professor
Dexter Lobricos
Tags
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